首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   204884篇
  免费   1757篇
  国内免费   603篇
化学   102763篇
晶体学   3376篇
力学   9341篇
综合类   5篇
数学   22587篇
物理学   69172篇
  2021年   1673篇
  2020年   1823篇
  2019年   2010篇
  2018年   2719篇
  2017年   2616篇
  2016年   3784篇
  2015年   2321篇
  2014年   3640篇
  2013年   9129篇
  2012年   7300篇
  2011年   8783篇
  2010年   6075篇
  2009年   5937篇
  2008年   7956篇
  2007年   8122篇
  2006年   7771篇
  2005年   6926篇
  2004年   6443篇
  2003年   5684篇
  2002年   5513篇
  2001年   6436篇
  2000年   4935篇
  1999年   3800篇
  1998年   3043篇
  1997年   3051篇
  1996年   2797篇
  1995年   2615篇
  1994年   2468篇
  1993年   2344篇
  1992年   2700篇
  1991年   2674篇
  1990年   2609篇
  1989年   2401篇
  1988年   2453篇
  1987年   2451篇
  1986年   2280篇
  1985年   2962篇
  1984年   3219篇
  1983年   2637篇
  1982年   2803篇
  1981年   2774篇
  1980年   2641篇
  1979年   2727篇
  1978年   2823篇
  1977年   2820篇
  1976年   2888篇
  1975年   2671篇
  1974年   2647篇
  1973年   2780篇
  1972年   1763篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The possibility to create nonthermal solitions by switching on an inhomogeneous magnetic field along the direction of a one dimensional magnetic chain is investigated using the inverse scattering method.Project of the Sonderforschungsbereich Frankfurt/Darmstadt, financed by special funds of the Deutsche Forschungsgemeinschaft  相似文献   
972.
Brownian motion in media with a space-dependent temperature and density is described by Langevin equations in phase space. Elimination of the velocity shows that diffusion inx-space cannot in general be characterized by a single diffusion parameter, nor can space-dependence always be accounted for by mere assignment of some sense of stochastic integration to the Langevin equation which has been reduced as in the homogeneous case. Steady solutions of the resulting equations agree with thermodynamics. Interactions between Brownian particles (giving rise to nonlinear Fokker-Planck equations) lead to a generalization of Einstein's relation.Work supported by the Swiss National Science Foundation  相似文献   
973.
An expression is found for the first correction to the average field produced by a relativistic electron moving in a constant and homogeneous magnetic field. It has electric and magnetic components which do not depend on the time but have a complicated dependence on the distance to the direction axis of the magnetic field. The obtained expressions are analyzed as functions of the distance to the axis and also of the electron state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 19–22, February, 1981.We thank Professor V. G. Bagrov for his interest in the work and valuable discussions of the results.  相似文献   
974.
In the practical use of electron-beam discharge lasers an important problem is that of their operating reliability. The weakest spot of an EBL is the electron-gun partition foil, and the main cause of its failure is the breakdown of the discharge gap. This paper reports investigations of the mechanisms that destroy the foil and propose for its protection a method that makes it possible to significantly increase the operating reliability of the EBL.Translated from Trudy Ordena Lenina Fizicheskogo Institute Im. P. N. Lebedeva, Vol. 116, pp. 202–208, 1980.  相似文献   
975.
It is shown that thin-film field effect transistors (FETs) made from amorphous (a-) silicon deposited by the glow-discharge technique have considerable potential as switching elements in addressable liquid crystal display panels. The fabrication of the elements and their characteristics with steady and pulsed applied potentials are discussed in some detail. Two important points are stressed: (i) a-Si device arrays can be produced by well-established photolithographic techniques, and (ii) satisfactory operation at applied voltages below 15VV is possible. Small experimental 7×5 transistor panels have been investigated and it is shown that with the present design up to 250-way multiplexing could be achieved. The reproducibility of FET characteristics is good and in tests so far no change has been observed after more than 109 switching operations.  相似文献   
976.
Resistivity and thermal conductivity of the intermediate valence compound CePd3 between 1.3 and 300 K are compared with those of the nonmagnetic and magnetic reference compounds YPd3 and GdPd3 and of alloys of the type Ce1xRE x Pd3 with RE=Y, Gd and 0.01<x<0.5. The analysis reveals the existence of a maximum metallic resistivity of 300 cm for CePd3. The intrinsic resistivity of CePd3 rises proportional toT 2 up to 100 K, with a coefficientB about 107 times larger than e.g. in copper. We interpret this with indirect electron-electron scattering mediated through valence transitions.  相似文献   
977.
Inclusive cross sections of η production by e+e- annihilation for c.m. energies between 4.0 and 5.0 GeV are presented. The η production is shown to be correlated with the production of a weakly decaying particle, indicating that its main source is F production. At the 4.42 GeV resonance it is correlated with a low energy photon, suggesting or production. A mass determination of the F is made at 4.42 GeV using the F → ηπ decay channel.  相似文献   
978.
Ternary and quaternary fission produced in silver and bromine nuclei have been studied withK5 nuclear emulsion exposed to 1.8 GeV/cK beams. The frequency of the ternary events is found to be ∼0.08 of that of the binary events produced in the same volume of the emulsion. The range ratio and range distribution of the fission fragments are studied and the angles between each pair of the fragments are determined. Ranges are found to vary from 5 to 40μ with a maximum number lying between 5 and 10μ. The angles between the fission fragments are found to form a broad distribution extending from 40° to 180°. A few of the events have also been analysed to give them a possible identity. A possible case of quaternary fission has also been reported. This paper was presented at the Symposium on 3rd High Energy Physics held at Bhubaneswar during November 1976.  相似文献   
979.
980.
Instantons and anti-instantons can profoundly influence the structure of a non-Abelian gauge theory involving N flavors of massless quarks. Interactions of the quarks with these pseudoparticles can spontaneously generate a quark mass, break the theory's SU(N) × SU(N) chiral symmetry and bind quark-antiquark pairs to form N2 ? 1 Goldstone bosons. If the spontaneously generated quark mass is small, multipseudoparticle configurations can be treated in a dilute gas approximation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号