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   221221篇
  免费   3010篇
  国内免费   1320篇
化学   123208篇
晶体学   3234篇
力学   8889篇
综合类   61篇
数学   24422篇
物理学   65737篇
  2020年   1776篇
  2019年   1920篇
  2018年   2500篇
  2017年   2546篇
  2016年   3681篇
  2015年   2444篇
  2014年   3555篇
  2013年   8903篇
  2012年   7748篇
  2011年   9447篇
  2010年   6674篇
  2009年   6479篇
  2008年   8831篇
  2007年   8937篇
  2006年   8424篇
  2005年   7731篇
  2004年   6891篇
  2003年   6068篇
  2002年   5996篇
  2001年   6706篇
  2000年   5069篇
  1999年   3671篇
  1998年   3038篇
  1997年   3013篇
  1996年   3012篇
  1995年   2618篇
  1994年   2720篇
  1993年   2582篇
  1992年   2830篇
  1991年   2896篇
  1990年   2703篇
  1989年   2619篇
  1988年   2559篇
  1987年   2499篇
  1986年   2520篇
  1985年   3300篇
  1984年   3360篇
  1983年   2805篇
  1982年   3046篇
  1981年   2811篇
  1980年   2607篇
  1979年   2790篇
  1978年   2996篇
  1977年   3032篇
  1976年   3059篇
  1975年   2793篇
  1974年   2906篇
  1973年   2956篇
  1972年   2318篇
  1971年   1845篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
We consider a two-dimensional Coulomb gas of positive and negative pointlike unit charges interacting via a logarithmic potential. The density (rather than the charge) correlation functions are studied. In the bulk, the form-factor theory of an equivalent sine-Gordon model is used to determine the density correlation length. At the surface of a rectilinear plain wall, the universality of the asymptotic behavior of the density correlations is suggested. A scaling analysis implies a local form of the compressibility sum rule near a hard wall. A symmetry of the Coulomb system with respect to the Möbius conformal transformation, which induces a gravitational source acting on the particle density, is established. Among the consequences, a universal term of the finite-size expansion of the grand potential is derived exactly for a disk geometry of the confining domain.  相似文献   
992.
The nonequilibrium phonon energy due to deformation interactions with hot electrons is determined. This energy depends on the lifetime of phonons with fixed momentum. Lifetime for phonons scattered by electrons and by macroscopic and microscopic impurities are calculated using the Keldysh diagram technique. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 115, No. 2, pp. 289–304, May, 1998.  相似文献   
993.
An exploratory Mössbauer spectroscopy study of the Fe-C system in the C rich region, prepared by high pressure-high temperature treatment near the graphite-diamond stability line, was made. The results obtained for the different processing conditions give no evidence of Fe intercalation in graphite. The presence of some water in the cell produced hydrated Fe complexes, which can explain the deleterious effect of water or hydrogen in the high pressure diamond synthesis.  相似文献   
994.
Translation planes of order q 2 containing non-Desarguesian Baer subplanes are used to construct transversal-free translation nets with very small deficiencies. Also, a generalization of the ideas of Bruen shows that any non-Desarguesian spread in PG(3, q) produces a transversal-free net of small deficiency.  相似文献   
995.
996.
L. Ya. Karpov Physical Chemical Research Institute. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 3, pp. 141–144, May–June, 1991.  相似文献   
997.
It is predicted that resonance coupling between two discrete electron energy levels corresponding to different size-quantization quantum numbers and different Landau quantum numbers can occur in a quantum well in a quantizing magnetic field. The resonance coupling is due to the interaction of an electron with LO phonons and results in the formation of polaron states of a new type. It is shown that for a certain value of the magnetic field, which depends on the splitting of the electron size-quantization levels, the absorption peak and the two-phonon resonance Raman scattering peak split into two components, the separation between which is determined by the electron-phonon coupling constant. The resonance coupling between size-quantization levels with the same Landau quantum numbers is also studied. The splitting of the peaks in this case is virtually independent of the magnetic field and can be observed in much weaker fields. The experimental observation of the effect will make it possible to determine the relative position of the electronic levels and the electron-phonon coupling constant. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 7, 511–515 (10 April 1997)  相似文献   
998.
Stirling渐进公式的一个新的构造证明   总被引:3,自引:1,他引:2  
本文用简易的分析工具,对n!给出了一个精确等式,从而导出Stirling渐近公式(2)的一个新的简短证明.  相似文献   
999.
1000.
The precision of atomic mass measurements in a Penning trap is directly proportional to the charge state q of the ion and, hence, can be increased by using highly charged ions (HCI). For this reason, charge breeding with an electron beam ion trap (EBIT) is employed at TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) on-line facility in Vancouver, Canada. By bombarding the injected and trapped singly charged ions with an intense beam of electrons, the charge state of the ions is rapidly increased inside the EBIT. To be compatible with the on-line requirements of short-lived isotopes, very high electron beam current densities are needed. The TITAN EBIT includes a 6 Tesla superconducting magnet and is designed to have electron beam currents and energies of up to 5 A and 60 keV, respectively. Once operational at full capacity, most species can be bred into a He-like configuration within tens of ms. Subsequently, the HCI are extracted, pass a Wien filter to reduce isobaric contamination, are cooled, and injected into a precision Penning trap for mass measurement. We will present the first results and current status of the TITAN EBIT, which has recently been moved to TRIUMF after assembly and commissioning at the Max-Planck-Institute (MPI) for Nuclear Physics in Heidelberg, Germany.  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