全文获取类型
收费全文 | 255035篇 |
免费 | 3913篇 |
国内免费 | 814篇 |
专业分类
化学 | 132270篇 |
晶体学 | 3619篇 |
力学 | 10636篇 |
综合类 | 10篇 |
数学 | 31491篇 |
物理学 | 81736篇 |
出版年
2021年 | 2186篇 |
2020年 | 2587篇 |
2019年 | 2701篇 |
2018年 | 3372篇 |
2017年 | 3264篇 |
2016年 | 5251篇 |
2015年 | 3510篇 |
2014年 | 4991篇 |
2013年 | 11749篇 |
2012年 | 9757篇 |
2011年 | 11481篇 |
2010年 | 7827篇 |
2009年 | 7446篇 |
2008年 | 10396篇 |
2007年 | 10417篇 |
2006年 | 9970篇 |
2005年 | 8931篇 |
2004年 | 8169篇 |
2003年 | 7060篇 |
2002年 | 6780篇 |
2001年 | 7370篇 |
2000年 | 5749篇 |
1999年 | 4437篇 |
1998年 | 3606篇 |
1997年 | 3612篇 |
1996年 | 3471篇 |
1995年 | 3251篇 |
1994年 | 3106篇 |
1993年 | 2998篇 |
1992年 | 3378篇 |
1991年 | 3149篇 |
1990年 | 3092篇 |
1989年 | 2861篇 |
1988年 | 2868篇 |
1987年 | 2868篇 |
1986年 | 2656篇 |
1985年 | 3548篇 |
1984年 | 3776篇 |
1983年 | 3098篇 |
1982年 | 3296篇 |
1981年 | 3273篇 |
1980年 | 3123篇 |
1979年 | 3198篇 |
1978年 | 3277篇 |
1977年 | 3256篇 |
1976年 | 3296篇 |
1975年 | 3082篇 |
1974年 | 3027篇 |
1973年 | 3080篇 |
1972年 | 1961篇 |
排序方式: 共有10000条查询结果,搜索用时 578 毫秒
941.
P Nürnberg I Barth E Fuhrmann C Lenzner T Losanova C Peters H P?che G Thiel 《Electrophoresis》1991,12(2-3):186-192
Germline and somatic instability of the human genome was studied, using synthetic oligonucleotides specific for simple repeat motifs. The following probes were used: (GTG)5, (GACA)4, (GATA)4, (CT)8, (TTAGGG)3, (GT)8, (GAA)6 and (GGAT)4. Each of them is unique with respect to the target regions recognized in the genome. Thus compilation of the various fingerprint data provides a complex map of the genome (and its deviations). While the fingerprints of differentiated somatic tissues never showed any alterations, in tumor tissues (namely gliomas) many changes could be detected. Most of the latter reflect secondary karyological aberrations. In nearly one third of the gliomas, drastically amplified and apparently monomorphic DNA fragments were identified. This marker should make it possible to deal with causal pathogenetic mechanisms as well as novel diagnostic strategies. 相似文献
942.
The correspondence between the imaginary time and real time thermal running coupling constant is discussed. The temperature dependence is derived in pure QCD at one-loop order in a generalized momentum subtraction (MOM) renormalization scheme. 相似文献
943.
944.
We calculate the effect of radial confinement on the Schwinger pair production rate by solving the Dirac equation in a flux-tube cylinder containing a constant chromoelectric field in the longitudinal direction. We show how the Dirac equation separates into radial and longitudinal equations for a mass term which has an arbitrary radial dependence and introduce radial confinement by having a finite mass inside the cylinder and an infinitely large mass outside. The resulting boundary conditions are equivalent to the MIT boundary condition. The equations are solved analytically for a constant quark mass inside the flux-tube, which acts like a waveguide. The discretization of the transverse wave vector which has a continuous spectrum in the non-confined case leads to a large suppression of the Schwinger pair-production rate for small radii. The minimal radius where pairs are created decreases with increasing field strength. The suppression turns out to be larger for heavier quarks than for light quarks. 相似文献
945.
J. H. de Araújo J. B. M. da Cunha A. Vasquez L. Amaral J. T. Moro F. C. Montenegro S. M. Rezende M. D. Coutinho Filho 《Hyperfine Interactions》1991,67(1-4):507-511
57Fe Mössbauer effect measurements in the diluted Ising antiferromagnet Fe x Zn1?x F2 withx=0.25 andx=0.57 at temperatures between 4.2 and 55 K, are reported. DC suceptibility measurements show a spin-glass (SG) phase at low temperatures forx≤0.31. Our Mössbauer spectra show a phase transition to a SG state with antiferromagnetic order (AFSG) forx=0.25 and only antiferromagnetic order forx=0.57. 相似文献
946.
947.
948.
Martin Schechter 《Mathematical Methods in the Applied Sciences》1994,17(4):229-238
We show how saddle point techniques can be used to obtain new results for general resonance problems of the type considered by Landesman and Lazer. 相似文献
949.
A method is proposed for evaluating the resistance of a flywheel rim to radial stresses in free rotation. The method is based on loading a rim segment in pure bending and calculating the limiting moment and the corresponding limiting angular velocity. Applicability of the method is substantiated theoretically by investigating the similarity of the radial stress diagrams in rotation and pure bending. The method is verified experimentally for the strained state of a rim segment in pure bending.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 4, pp. 521–526, July–August, 1993. 相似文献
950.
A. A. Maksimenko I. D. Sadekov A. G. Maslakov O. E. Kompan A. I. Yanovskii Yu. T. Struchkov V. I. Minkin 《Journal of Structural Chemistry》1991,32(3):404-405
Scientific-Research Institute of Physical and Organic Chemistry, Rostov State University. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 3, pp. 104–106, May–June, 1991. 相似文献