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Livestock science, 2016-11, Vol.193, p.20-25
2016
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Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 2003-12, Vol.515 (1), p.226-233
- Acosta, D.
- Apollinari, G.
- Arisaka, K.
- Bondar, N.
- Breedon, R.
- Bujak, A.
- Bylsma, B.
- Chester, N.
- Clare, R.
- Cline, D.
- Cousins, R.
- Cox, T.
- Dolinsky, S.
- Durkin, S.
- Eartly, D.
- Ivanov, Yu
- Ferguson, T.
- Gavrilov, G.
- Gilmore, J.
- Gu, J.
- Gutay, L.
- Hann, F.
- Hartmut, R.
- Hauser, J.
- He, K.
- Ignatenko, M.
- Ilie, S.
- Jiang, C.
- Ko, W.
- Korytov, A.
- Krivshich, A.
- Kuznetsova, K.
- Layter, J.
- Lee, R.
- Levtchenko, P.
- Ling, T.Y.
- Loveless, D.
- Lusin, S.
- Maeshima, K.
- Madorsky, A.
- Matthey, C.
- Matveev, M.
- von der Mey, M.
- Mitselmakher, G.
- Otwinowski, S.
- Padley, P.
- Pal, I.
- Pischalnikov, Yu
- Prokofiev, O.
- Razmyslovich, V.
- Reeder, D.
- Roberts, J.
- Schipunov, L.
- Smirnov, I.
- Souvorov, V.
- Stasko, J.
- Sun, H.
- Sytnik, V.
- Terentyev, N.
- Tripathi, M.
- Vavilov, S.
- Volkov, S.
- Vorobyov, A.
- Vorobyov, I.
- Wang, L.
- Yarba, V.
- Zhou, L.
- Zhu, Z.
2003
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Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 2002-11, Vol.494 (1), p.504-508
- Acosta, D
- Apollinari, G
- Arisaka, K
- Blomquist, J
- Breedon, R
- Bondar, N
- Bonushkin, Yu
- Borissov, E
- Bujak, A
- Bylsma, B
- Chester, N
- Chrisman, D
- Clare, R
- Cline, D
- Cousins, R
- Cox, T
- Dolinsky, S
- Durkin, S
- Eartly, D
- Ferguson, T
- Feyzi, F
- Gavrilov, G
- Gilmore, J
- Gu, J
- Gutay, L
- Hann, F
- Hauser, J
- Hershman II, S
- Ignatenko, M
- Ilie, S
- Ivanov, Yu
- Ko, W
- Korienek, J
- Korytov, A
- Kubic, J
- Layter, J
- Lee, R
- Levtchenko, P
- Ling, T.Y
- Loveless, R
- Lusin, S
- Madorsky, A
- Maeshima, K
- Matthey, C
- Matveev, M
- Medved, S
- von der Mey, M
- Mitselmakher, G
- Otwinowski, S
- Padley, P
- Pal, I
- Petriello, F
- Pischalnikov, Yu
- Prokofiev, O
- Razmyslovich, V
- Reeder, D
- Roberts, J
- Schipunov, L
- Sedov, S
- Smirnov, I
- Smith, B
- Sobolev, S
- Soulimov, V
- Souvorov, V
- Staško, J
- Sytnik, V
- Tannenbaum, B
- Terentyev, N
- Tripathi, M
- Vavilov, S
- Villa, S
- Volkov, A
- Vorobyov, A
- Yarba, V
- Zilizi, G
2002
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 2000-10, Vol.453 (1), p.182-187
- Acosta, D
- Apollinari, G
- Blomquist, J
- Breedon, R
- Bondar, N
- Bonushkin, Yu
- Borissov, E
- Bujak, A
- Bylsma, B
- Chester, N
- Chrisman, D
- Cline, D
- Dolinsky, S
- Durkin, S
- Eartly, D
- Ferguson, T
- Feyzi, F
- Gilmore, J
- Gorn, L
- Gorn, W
- Gu, J
- Gutay, L
- Hauser, J
- Hershman II, S
- Hoftiezer, J
- Kisselev, O
- Ko, W
- Korienek, J
- Korytov, A
- Kubic, J
- Layter, J
- Ling, T.Y
- Loveless, R
- Lusin, S
- Matthey, C
- Matveev, M
- Medved, S
- Mitselmakher, G
- Otwinowski, S
- Padley, P
- Petriello, F
- Pischalnikov, Yu
- Prokofiev, O
- Razmyslovich, V
- Reeder, D
- Roberts, J
- Robl, P
- Rush, C
- Santiard, J.-C
- Sedov, S
- Smith, B
- Sobolev, S
- Soulimov, V
- Tannenbaum, B
- Terentyev, N
- Vorobyov, A
- Yarba, V
2000
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 1999-04, Vol.425 (1), p.92-105
- Baarmand, M.M
- Vaniachine, A
- Bonushkin, Yu
- Matthey, C
- Hauser, J
- Muller, T
- Otwinowski, S
- Zeng, J
- Chrisman, D
- Giacomelli, P
- Gorn, W
- Layter, J.G
- Minor, C
- Schenk, P
- Durkin, S
- Hoftiezer, J
- Lennous, P
- Ling, T.Y
- Rush, C
- Ferguson, T
- Hirschfelder, J
- Hoorani, H
- Fitch, J
- Gorn, L
- Korytov, A
- Mitselmakher, G
- Kisselev, O
- Prokofiev, O
- Smirnov, I
- Soulimov, V
- Klem, D.E
- Vercelli, T
- Wuest, C
- Medved, S
- Preston, L
- Santiard, J.C
- von Goeler, E
1999
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 1998, Vol.402 (1), p.36-52
- Baarmand, M.M
- Bonushkin, Yu
- Chrisman, D
- Durkin, S
- Ferguson, T
- Giacomelli, P
- Gorn, L
- Gorn, W
- Hauser, J
- Hirschfelder, J
- Hoftiezer, J
- Hoorani, H
- Kisselev, O
- Klem, D.E
- Korytov, A
- Layter, J.G
- Lennous, P
- Ling, T.Y
- Matthey, C
- Medved, S
- Minor, C
- Mitselmakher, G
- Muller, T
- Otwinowski, S
- Preston, L
- Prokofiev, O
- Rush, C
- Schenk, P
- Sedykh, Y
- Smirnov, I
- Soulimov, V
- Vaniachine, A
- Vercelli, T
- von Goeler, E
- Wuest, C
- Zeng, J
1998
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 1998-12, Vol.419 (2-3), p.469-474
- Acosta, D.
- Blomquist, J.
- Bondar, N.
- Bonushkin, Yu
- Bujak, A.
- Bylsma, B.
- Chrisman, D.
- Durkin, S.
- Eartly, D.
- Ferguson, T.
- Feyzi, F.
- Fisyak, Yu
- Gorn, L.
- Gorn, W.
- Gutay, L.
- Hauser, J.
- Hershman II, S.
- Hoftiezer, J.
- Hoorani, H.
- Kiselev, O.
- Korienek, J.
- Korytov, A.
- Layter, J.
- Lennous, P.
- Ling, T.Y.
- Loveless, R.
- Medved, S.
- Mitselmakher, G.
- Prokofiev, O.
- Razmyslovich, V.
- Rush, C.
- Sedov, S.
- Sobolev, S.
- Soulimov, V.
- Vorobyov, A.
1998
Volltextzugriff (PDF)
Nuclear physics. B, 1978-01, Vol.141 (1), p.1-28
1978
Volltextzugriff (PDF)
Nuclear physics. B, 1978, Vol.132 (1), p.29-44
1978
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment, 1985-08, Vol.238 (2), p.265-272
1985
Volltextzugriff (PDF)
Physics letters. B, 1976-01, Vol.60 (5), p.485-490
1976
Volltextzugriff (PDF)
Physics letters. B, 1975-01, Vol.55 (3), p.331-335
1975
Volltextzugriff (PDF)
Physics letters. B, 1976-03, Vol.61 (1), p.89-92
1976
Volltextzugriff (PDF)
Physics letters. B, 1977-02, Vol.66 (4), p.401-404
1977
Volltextzugriff (PDF)
Physics letters. B, 1977-01, Vol.68 (3), p.279-282
1977
Volltextzugriff (PDF)
Physics letters. B, 1975-01, Vol.55 (3), p.336-340
1975
Volltextzugriff (PDF)
The European physical journal. C, Particles and fields, 1998-08, Vol.5 (1), p.1-17
- Ashby, S. F
- Barberio, E
- Batley, J. R
- Bechtluft, J
- Biebel, O
- Bobinski, M
- Burckhart, H. J
- Carter, A. A
- Davis, R
- Desch, K
- Dixit, M. S
- Duckeck, G
- Duerdoth, I. P
- Estabrooks, P. G
- Fierro, M
- Foucher, M
- Gagnon, P
- Gibson, V
- Glenzinski, D
- Goodrick, M. J
- Grunhaus, J
- Hajdu, C
- Hargrove, C. K
- Hart, P. A
- Hauschild, M
- Heuer, R. D
- Hill, J. C
- Hillier, S. J
- Hobson, P. R
- Honma, A. K
- Horvath, D
- Hossain, K. R
- Igo-Kemenes, P
- Imrie, D. C
- Ishii, K
- Jawahery, A
- Jeremie, H
- Jones, M
- Junk, T. R
- Keeler, R. K
- Kennedy, B. W
- Kirk, J
- Klier, A
- Kluth, S
- Kokott, T. P
- Kolrep, M
- Kowalewski, R. V
- Kyberd, P
- Lai, W. P
- Lauber, J
- List, B
- Marcellini, S
- McDonald, W. J
- McMahon, T. J
- McPherson, R. A
- Meijers, F
- Menke, S
- Meyer, J
- Mikenberg, G
- Montanari, A
- Nakamura, I
- Oakham, F. G
- Ogren, H. O
- Pásztor, G
- Pater, J. R
- Petzold, S
- Pinfold, J
- Poffenberger, P
- Poli, B
- Rozen, Y
- Sarkisyan, E. K. G
- Schaile, A. D
- Scharf, F
- Schleper, P
- Schmitt, S
- Schumacher, M
- Scott, W. G
- Shen, B. C
- Sherwood, P
- Skillman, A
- Skuja, A
- Snow, G. A
- Sobie, R
- Söldner-Rembold, S
- Stephens, K
- Stoll, K
- Ströhmer, R
- Taras, P
- Tarem, S
- Teuscher, R
- Torrence, E
- Tsur, E
- Turcot, A. S
- Turner-Watson, M. F
- Van Kooten, R
- Vannerem, P
- Verzocchi, M
- Wilson, G. W
- Wyatt, T. R
- Yekutieli, G
1998
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1979-01, Vol.26 (1), p.68-72
1979
Volltextzugriff (PDF)
Nuclear instruments & methods, 1979-01, Vol.161 (3), p.383-390
1979
Volltextzugriff (PDF)
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 1995-10, Vol.364 (3), p.473-487
1995
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1983-01, Vol.30 (1), p.76-81
- Aihara, H.
- Alston-Garnjost, M.
- Badtke, D. H.
- Bakken, J. A.
- Barbaro-Galtieri, A.
- Barnes, A. V.
- Barnett, B. A.
- Blumenfeld, B.
- Bross, A.
- Buchanan, C. D.
- Carithers, W. C.
- Chamberlain, O.
- Chiba, J.
- Chien, C-Y.
- Clark, A. R.
- Dahl, O. I.
- Day, C. T.
- Delpierre, P.
- Derby, K. A.
- Eberhard, P. H.
- Fancher, D. L.
- Fujii, H.
- Fujii, T.
- Gabioud, B.
- Gary, J. W.
- Gorn, W.
- Hadley, N. J.
- Hauptman, J. M.
- Heck, B.
- Hilke, H. J.
- Huth, J. E.
- Hylen, J.
- Iwasaki, H.
- Kamae, T.
- Kenney, R. W.
- Kerth, L. T.
- Koda, R.
- Kofler, R. R.
- Kwong, K. K.
- Layter, J. G.
- Lindsey, C. S.
- Loken, S. C.
- Lu, X-Q.
- Lynch, G. R.
- Madansky, L.
- Madaras, R. J.
- Majka, R.
- Mallet, J.
- Martin, P. S.
- Maruyama, K.
- Marx, J.N.
- Matthews, J. A. J.
- Melnikoff, S. O.
- Moses, W.
- Nemethy, P.
- Nygren, D. R.
- Oddone, P. J.
- Park, D.
- Pevsner, A.
- Pripstein, M.
- Robrish, P. R.
- Ronan, M. T.
- Ross, R. R.
- Rouse, F. R.
- Shapiro, G.
- Shapiro, M. D.
- Shen, B. C.
- Slater, W. E.
- Stevenson, M. L.
- Stork, D. H.
- Ticho, H. K.
- Toge, N.
- Urban, M.
- Van Dalen, G. J.
- van Tyen, R.
- Videau, H.
- Wayne, M.
- Wenzel, W. A.
- vanDaalen Wetters, R. F.
- Yamauchi, M.
- Zeller, M. E.
- Zhang, W-M.
- Madaras, Ronald J.
1983
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1983-02, Vol.30 (1), p.63-66
- Gabioud, Bernard
- Aihara, H.
- Alston-Garnjost, M.
- Badtke, D. H.
- Bakken, J. A.
- Barbaro-Galtieri, A.
- Barnes, A. V.
- Barnett, B. A.
- Blumenfeld, B.
- Bross, A.
- Buchanan, C. D.
- Carithers, W. C.
- Chamberlain, O.
- Chiba, J.
- Chien, C-Y.
- Clark, A. R.
- Dahl, O. I.
- Day, C. T.
- Delpierre, P.
- Derby, K. A.
- Eberhard, P. H.
- Fancher, D. L.
- Fujii, H.
- Fujii, T.
- Gabioud, B.
- Gary, J. W.
- Gorn, W.
- Hadley, N. J.
- Hauptman, J. M.
- Heck, B.
- Hilke, H.
- Huth, J. E.
- Hylen, J.
- Iwasaki, H.
- Kamae, T.
- Kenney, R. W.
- Kerth, L. T.
- Koda, R.
- Kofler, R. R.
- Kwong, K. K.
- Layter, J. G.
- Lindsey, C. S.
- Loken, S. C.
- Lu, X-Q.
- Lynch, G. R.
- Madansky, L.
- Madaras, R. J.
- Majka, R.
- Mallet, J.
- Martin, P. S.
- Maruyama, K.
- Marx, J. N.
- Matthews, J. A. J.
- Melnikoff, S. O.
- Moses, W.
- Nemethy, P.
- Nygren, D. R.
- Oddone, P. J.
- Park, D.
- Pevsner, A.
- Pripstein, M.
- Robrish, P. R.
- Ronan, M. T.
- Ross, R. R.
- Rouse, F. R.
- Shapiro, G.
- Shapiro, M. D.
- Shen, B. C.
- Slater, W. E.
- Stevenson, M. L.
- Stork, D. H.
- Ticho, H. K.
- Toge, N.
- Urban, M.
- Van Dalen, G. J.
- van Tyen, R.
- Videau, H.
- Wayne, M.
- Wenzel, W. A.
- vanDaalen Wetters, R. F.
- Yamauchi, M.
- Zeller, M. E.
- Zhang, W-M.
1983
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1983-02, Vol.30 (1), p.117-121
- Aihara, H.
- Alston-Garnjost, M.
- Badtke, D. H.
- Bakken, J. A.
- Barbaro-Galtieri, A.
- Barnes, A. V.
- Barnett, B. A.
- Blumenfeld, B.
- Bross, A.
- Buchanan, C. D.
- Carithers, W. C.
- Chamberlain, O.
- Chiba, J.
- Chien, C.-Y.
- Clark, A. R.
- Dahl, O. I.
- Day, C. T.
- Delpierre, P.
- Derby, K. A.
- Eberhard, P. H.
- Fancher, D. L.
- Fujii, H.
- Fujii, T.
- Gabioud, B.
- Gary, J. W.
- Gorn, W.
- Hadley, N. J.
- Hauptman, J. M.
- Heck, B.
- Hilke, H.
- Huth, J. E.
- Hylen, J.
- Iwasaki, H.
- Kamae, T.
- Kenney, R. W.
- Kerth, L. T.
- Koda, R.
- Kofler, R. R.
- Kwong, K. K.
- Layter, J. G.
- Lindsey, C.S.
- Loken, S. C.
- Lu, X.-Q.
- Lynch, G. R.
- Madansky, L.
- Madaras, R. J.
- Majka, R.
- Mallet, J.
- Martin, P. S.
- Maruyama, K.
- Marx, J. N.
- Matthews, J. A. J.
- Melnikoff, S. O.
- Moses, W.
- Nemethy, P.
- Nygren, D. R.
- Oddonel, P. J.
- Park, D.
- Pevsner, A.
- Pripstein, M.
- Robrish, P. R.
- Ronan, M. T.
- Ross, R. R.
- Rouse, F. R.
- Shapiro, G.
- Shapiro, M. D.
- Shen, B. C.
- Slater, W. E.
- Stevenson, M. L.
- Stork, D. H.
- Ticho, H. K.
- Toge, N.
- Urban, M.
- Van Dalen, G. J.
- van Tyen, R.
- Videau, H.
- Wayne, M.
- Wenzel, W. A.
- vanDaalen Wetters, R. F.
- Yamauchi, M.
- Zeller, M. E.
- Zhang, W.-M.
1983
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1983-02, Vol.30 (1), p.67-70
- Aihara, H.
- Alston-Garnjost, M.
- Badtke, D. H.
- Bakken, J. A.
- Barbaro-Galtieri, A.
- Barnes, A. V.
- Barnett, B. A.
- Blumenfeld, B. J.
- Bross, A.
- Buchanan, C. D.
- Carithers, W. C.
- Chamberlain, O.
- Chiba, J.
- Chien, C-Y
- Clark, A. R.
- Dahl, O. I.
- Day, C. T.
- Delpiee, P.
- Derby, K. A.
- Eberhard, P. H.
- Fancher, D. L.
- Fujii, H.
- Fujii, T.
- Gabioud, B.
- Gary, J. W.
- Gorn, W.
- Hadley, N. J.
- Hauptman, J. M.
- Heck, B.
- Hilke, H.
- Huth, J. E.
- Hylen, J.
- Iwasaki, H.
- Kamae, T.
- Kenney, R. W.
- Kerth, L. T.
- Koda, R.
- Kofler, R. R.
- Kwong, K. K.
- Layter, J. G.
- Lindsey, C. S.
- Loken, S. C.
- Lu, X-Q.
- Lynch, G. R.
- Madansky, L.
- Madaras, R. J.
- Majka, R.
- Mallet, J.
- Martin, P. S.
- Maruyama, K.
- Marx, J. N.
- Matthews, J. A. J.
- Melnikoff, S. O.
- Moses, W.
- Nemethy, P.
- Nygren, D. R.
- Oddone, P. J.
- Park, D.
- Pevsner, A.
- Pripstein, M.
- Robrish, P. R.
- Ronan, M. T.
- Ross, R. R.
- Rouse, F. R.
- Shapiro, G.
- Shapiro, M. D.
- Shen, B. C.
- Slater, W. E.
- Spangler, W. J.
- Stevenson, M. L.
- Stork, D. H.
- Ticho, H. K.
- Toge, N.
- Van Dalen, G. J.
- van Tyen, R.
- Videau, H.
- Wayne, M.
- Wenzel, W. A.
- vanDaalen Wetters, R. F.
- Yamauchi, M.
- Zeller, M. E.
- Zhang, W-M.
1983
Volltextzugriff (PDF)
IEEE transactions on nuclear science, 1983-01, Vol.30 (1), p.153-157
- Aihara, H.
- Alston-Garnjost, M.
- Badtke, D. H.
- Bakken, J. A.
- Barbaro-Galtieri, A.
- Barnes, A. V.
- Barnett, B. A.
- Blumenfeld, B.
- Bross, A.
- Buchanan, C. D.
- Carithers, W. C.
- Chamberlain, O.
- Chiba, J.
- Chien, C-Y.
- Clark, A. R.
- Dahl, O. I.
- Day, C. T.
- Derby, K. A.
- Delpierre, P.
- Eberhard, P. H.
- Fancher, D. L.
- Fujii, H.
- Ftjii, T.
- Gabioud, B.
- Gary, J. W.
- Gorn, W.
- Heck, B.
- Hadley, N. J.
- Hauptman, J. M.
- Hilke, H-J.
- Huth, J. E.
- Hylen, J.
- Iwasaki, H.
- Kamae, T.
- Kenney, R. W.
- Kerth, L. T.
- Koda, R.
- Kofler, R. R.
- Kwong, K. K.
- Layter, J. G.
- Lindsey, C. S.
- Loken, S. C.
- Lu, X-Q.
- Lynch, G. R.
- Madansky, L.
- Madaras, R. J.
- Majka, R.
- Mallet, J.
- Martin, P. S.
- Maruyama, K.
- Marx, J. N.
- Matthews, J. A. J.
- Melnikoff, S. O.
- Moses, W.
- Nemethy, P.
- Nygren, D. R.
- Oddone, P. J.
- Park, D.
- Pevsner, A.
- Pripstein, M.
- Robrish, P. R.
- Ronan, M. T.
- Ross, R. R.
- Rouse, F. R.
- Shapiro, G.
- Shapiro, M. D.
- Shen, B. C.
- Slater, W. E.
- Stevenson, M. L.
- Stork, D. H.
- Ticho, H. K.
- Toge, N.
- Van Dalen, G. J.
- van Tyen, R.
- Urban, M.
- Videau, H.
- Wayne, M.
- Wenzel, W. A.
- vanDaalen Wetters, R. F.
- Yamauchi, M.
- Zeller, M. E.
- Zhang, W-M.
- Lindsey, Clark S.
1983
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Erscheinungsjahr
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Thema
- Science & Technology
- Physics
- Physical Sciences
- Physics, Particles & Fields
- Particle Physics
- Technology
- Nuclear Science & Technology
- Experiment
- Physics, Nuclear
- Instruments & Instrumentation
- Detectors And Experimental Techniques
- Engineering
- Engineering, Electrical & Electronic
- Astronomy & Astrophysics
- Detectors
- Wires
- Cathodes
- Laboratories
- Spatial Resolution
- Aging
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- Ingenta
- Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
- Elsevier ScienceDirect Journals Complete
- EZB Electronic Journals Library
- IngentaConnect Journals
- Springer LINK 全文期刊数据库
- SpringerLINK Contemporary (Konsortium Baden-Württemberg)
- IEEE Electronic Library Online
- MEDLINE
- PROLA-Physical Review Online Archive (American Physical Society Journals)
Zeitschrift / Serie
- Physics Letters. B
- The European Physical Journal. C, Particles And Fields
- Nuclear Instruments & Methods In Physics Research. Section A, Accelerators, Spectrometers, Detectors And Associated Equipment
- European Physical Journal. C, Particles And Fields
- Ieee Transactions On Nuclear Science
- Zeitschrift Für Physik C Particles And Fields
- Zeitschrift Für Physik. C, Particles And Fields
- Nuclear Instruments And Methods In Physics Research. Section A, Accelerators, Spectrometers, Detectors And Associated Equipment/nuclear Instruments & Methods In Physics Research. Section A, Accelerators, Spectrometers, Detectors And Associated Equipment
- The European Physical Journal C
- Physics Letters B