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   176529篇
  免费   574篇
  国内免费   133篇
化学   73628篇
晶体学   2657篇
力学   10415篇
综合类   1篇
数学   32448篇
物理学   58087篇
  2021年   870篇
  2020年   965篇
  2019年   1105篇
  2018年   10332篇
  2017年   11199篇
  2016年   6183篇
  2015年   1851篇
  2014年   1845篇
  2013年   3398篇
  2012年   7266篇
  2011年   15922篇
  2010年   9751篇
  2009年   9887篇
  2008年   13734篇
  2007年   17312篇
  2006年   2964篇
  2005年   9164篇
  2004年   5682篇
  2003年   5624篇
  2002年   3611篇
  2001年   2404篇
  2000年   1963篇
  1999年   1294篇
  1998年   1172篇
  1997年   1054篇
  1996年   1079篇
  1995年   942篇
  1994年   906篇
  1993年   897篇
  1992年   939篇
  1991年   1014篇
  1990年   956篇
  1989年   991篇
  1988年   915篇
  1987年   862篇
  1986年   822篇
  1985年   962篇
  1984年   1074篇
  1983年   920篇
  1982年   931篇
  1981年   843篇
  1980年   797篇
  1979年   882篇
  1978年   1011篇
  1977年   947篇
  1976年   880篇
  1975年   828篇
  1974年   844篇
  1973年   857篇
  1972年   602篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
The energy loss effect in nuclear matter, which is a nuclear effect apart from the nuclear effect on the parton distribution as in deep-inelastic scattering process, can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of the nuclear parton distribution studied only with lepton deep-inelastic scattering experimental data, the measured Drell-Yan production cross sections for 800 GeV proton incident on a variety of nuclear targets are analyzed within the Glauber framework which takes into account the energy loss of the beam proton. It is shown that the theoretical results with considering the energy loss effect are in good agreement with the FNAL E866 data.Arrival of the final proofs: 24 June 2003  相似文献   
162.
We propose to use the radiofrequency single-electron transistor as an extremely sensitive probe to detect the time-periodic ac signal generated by a sliding electron lattice in the insulating state of the two-dimensional electron gas. We also propose to use the optically-pumped NMR technique to probe the electron spin structure of the insulating state. We show that the electron effective mass and spin susceptibility are strongly enhanced by critical fluctuations of the electron lattice in the vicinity of the metal-insulator transition, as observed in experiment.  相似文献   
163.
164.
Molecular-dynamics (MD) simulation of the destruction of a crystal film heated by a femtosecond laser pulse was carried out. Heating is assumed to be instantaneous, because there is no time for the material to be displaced during the pulse. Film destruction is caused by the interaction of unloading waves. It can be considered as a model of a more complex process of splitting out of a thin surface layer from a massive target in the case where the layer remains solid after heating. It was found that the crystal order is broken due to the stretching strains and to the strong anisotropy of residual stress, resulting in a bipartition of the layer separating from the target. The lattice stretching and the formation of anisotropic stresses are due to the expansion of a heated lattice.  相似文献   
165.
Bibliography: 42 titles.__________Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 306, 2003, pp. 7–15.  相似文献   
166.
The effect of the amount of desorbed water on the mechanical properties of composites based on low-density polyethylene and linen yarn production waste (LW) is analyzed by statistical methods. It is shown that the amount of absorbed water decreases during the desorption process at room temperature both for specimens modified and unmodified with diphenylmethane diisocyanate (DIC.) The most sensitive to the action of water is the elastic modulus, which decreases considerably under the effect of water and is fully restored in the desorption process. The tensile strain also increases with the amount of absorbed water. It is found that the elastic modulus of the unmodified composite correlates linearly with the amount of desorbed water. Between the amount of desorbed water and the tensile strain, as well the specific work of deformation, a negative linear correlation is revealed. After water desorption, all strength and deformation characteristics of both the modified and unmodified composites are fully recovered.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 515–524, July–August, 2005.  相似文献   
167.
We discuss the symplectic geometry of linear Hamiltonian systems with nondegenerate Hamiltonians. These systems can be reduced to linear second-order differential equations characteristic of linear oscillation theory. This reduction is related to the problem on the signatures of restrictions of quadratic forms to Lagrangian planes. We study vortex symplectic planes invariant with respect to linear Hamiltonian systems. These planes are determined by the solutions of quadratic matrix equations of a special form. New conditions for gyroscopic stabilization are found.  相似文献   
168.
Hexagonal and cubic cadmium selenide were prepared from a chemical route by using cadmium chloride and potassium selenium hydride obtained from reaction of selenium powder and potassium boron hydride. The product obtained was thermally treated under argon flux at 300, 500 and 600 °C for 2 h and characterized by X-ray photoelectron spectroscopy and X-ray diffraction. The X-ray diffraction data were refined by Rietveld method and the structural parameters were determined for the phases of each annealed samples. At 300 °C five phases were identified: Cubic and hexagonal cadmium selenides and the contaminants: Potassium chloride, boron oxide and cadmium boron oxide. At 500 and 600 °C only the hexagonal cadmium selenide phase was identified besides the other above mentioned contaminant.  相似文献   
169.
170.
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