全文获取类型
收费全文 | 5056篇 |
免费 | 148篇 |
国内免费 | 12篇 |
专业分类
化学 | 3388篇 |
晶体学 | 45篇 |
力学 | 86篇 |
数学 | 527篇 |
物理学 | 1170篇 |
出版年
2023年 | 49篇 |
2022年 | 160篇 |
2021年 | 153篇 |
2020年 | 127篇 |
2019年 | 139篇 |
2018年 | 110篇 |
2017年 | 121篇 |
2016年 | 205篇 |
2015年 | 159篇 |
2014年 | 160篇 |
2013年 | 302篇 |
2012年 | 334篇 |
2011年 | 397篇 |
2010年 | 255篇 |
2009年 | 246篇 |
2008年 | 344篇 |
2007年 | 309篇 |
2006年 | 256篇 |
2005年 | 214篇 |
2004年 | 205篇 |
2003年 | 149篇 |
2002年 | 123篇 |
2001年 | 83篇 |
2000年 | 87篇 |
1999年 | 52篇 |
1998年 | 33篇 |
1997年 | 32篇 |
1996年 | 47篇 |
1995年 | 34篇 |
1994年 | 32篇 |
1993年 | 32篇 |
1992年 | 39篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 6篇 |
1972年 | 4篇 |
排序方式: 共有5216条查询结果,搜索用时 15 毫秒
71.
Flávia R. O. Silva Camila T. Nabeshima Maria H. Bellini Nestor Schor Nilson D. Vieira Jr Lilia C. Courrol 《Journal of fluorescence》2013,23(1):131-135
This paper describes the elimination of porphyrins by feces. It was demonstrated that porphyrin accumulates substantially more in tumors than in normal tissues, and consequently more PPIX reaches the blood of patients and animals with tumors, and then, it needs to be eliminated. The fluorescence of feces revealed that there are large amounts of PPIX in the excreta of animals with cancer comparing with healthy animals. The autofluorescence of feces porphyrin extracted with acetone was analyzed using fluorescence spectroscopy of animals inoculated with DU145 cells into the prostate and healthy animals to monitor the PPIX concentration. Emission spectra were obtained by exciting the samples at 405 nm. Significant differences were observed in autofluorescence intensities measured in the 575–725 nm spectral regions for the studied groups. The results showed a noninvasive, simple, rapid and sensitive method to detect cancer by feces analysis. 相似文献
72.
73.
Vicenţiu D. Rădulescu Gelson C. G. dos Santos Leandro S. Tavares 《Mathematische Nachrichten》2023,296(6):2555-2574
This paper is concerned with the existence and multiplicity of solutions for a class of problems involving the Φ-Laplacian operator with general assumptions on the nonlinearities, which include both semipositone cases and critical concave convex problems. The research is based on the subsupersolution technique combined with a truncation argument and an application of the Mountain Pass Theorem. The results in this paper improve and complement some recent contributions to this field. 相似文献
74.
S. Czajkowski M. Bernas P. Armbruster H. Geissel C. Kozhuharov G. Münzenberg D. Vieira Ph. Dessagne Ch. Miehe E. Hanelt G. Audi J. K. P. Lee 《Zeitschrift für Physik A Hadrons and Nuclei》1994,348(4):267-272
Neutron-rich Co and Fe isotopes produced by86Kr projectile fragmentation at 500 MeV/u were separated and identified using the fragment separator (FrS) in a bunched energy mode.66Co and65Fe ions were selectively implanted in a double PIN-diode array where the-decay signals were measured. The half-lives were deduced from time correlations between implantation and-decay signals. The remeasurement of the66Co half-life confirms the isotope identification. The value of the65Fe half-life was found to be 0.45±0.15 s. 相似文献
75.
J. Giovinazzo B. Blank C. Borcea M. Chartier S. Czajkowski G. de France R. Grzywacz Z. Janas M. Lewitowicz F. de Oliveira Santos M. Pfützner M.S. Pravikoff J.C. Thomas 《The European Physical Journal A - Hadrons and Nuclei》2001,10(1):73-84
Decay studies of very neutron-deficient nuclei ranging from 39Ti to 49Ni have been performed during a projectile fragmentation experiment at the GANIL/LISE3 separator. For all nuclei studied in
this work, 39, 40Ti, 42, 43Cr, 46Mn, 45, 46, 47Fe and 49Ni, half-lives and decay spectra have been measured. In a few cases, γ coincidence measurements helped to successfully identify
the initial and final states of transitions. In these cases, partial decay scheme are proposed. For the most exotic isotopes,
39Ti, 42Cr, 45Fe and 49Ni, which are candidates for two-proton radioactivity from the ground state, no clear evidence of this process is seen in
our spectra and we conclude rather on a delayed particle decay.
Received: 26 July 2000 / Accepted: 20 December 2000 相似文献
76.
Santos TS Kirby BJ Kumar S May SJ Borchers JA Maranville BB Zarestky J te Velthuis SG van den Brink J Bhattacharya A 《Physical review letters》2011,107(16):167202
We demonstrate that delta doping can be used to create a dimensionally confined region of metallic ferromagnetism in an antiferromagnetic (AFM) manganite host, without introducing any explicit disorder due to dopants or frustration of spins. Theoretical consideration of these additional carriers shows that they cause a local enhancement of ferromagnetic double exchange with respect to AFM superexchange, resulting in local canting of the AFM spins. This leads to a highly modulated magnetization, as measured by polarized neutron reflectometry. The spatial modulation of the canting is related to the spreading of charge from the doped layer and establishes a fundamental length scale for charge transfer, transformation of orbital occupancy, and magnetic order in these manganites. Furthermore, we confirm the existence of the canted, AFM state as was predicted by de Gennes [Phys. Rev. 118, 141 (1960)] but had remained elusive. 相似文献
77.
78.
79.
Daniel S. Covita Dimitrios F. Anagnostopoulos Hermann Fuhrmann Hubert Gorke Detlev Gotta Alexander Gruber Albert Hirtl Tomoichi Ishiwatari Paul Indelicato Thomas S. Jensen Eric-Olivier Le Bigot Valeri E. Markushin Michael Nekipelov Vladimir N. Pomerantsev Vladimir P. Popov Joaquim M. F. dos Santos Philipp Schmid Leopold M. Simons Marian Theisen Martino Trassinelli Joao F. C. A. Veloso Johann Zmeskal 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2018,72(4):72
80.
An image processing study of a reentrant discotic cholesteric – biaxial cholesteric phase transition
D. D. Luders G. A. Zoner O. R. Santos W. S. Braga A. R. Sampaio N. M. Kimura 《Phase Transitions》2018,91(4):398-405
In this work, we study and characterize the cholesteric sequence of phases (ChDr ? ChB ? ChD), where the first ChDr is the reentrant cholesteric discotic phase, ChB is the cholesteric biaxial phase and the second ChD is the cholesteric discotic phase. This sequence of phases is studied through polarized light microscopy and image processing technique, where, for the first time, the domains and borders of these transitions are established and characterized. They are also investigated and optically characterized throughout their textures. 相似文献