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   107530篇
  免费   6723篇
  国内免费   5423篇
化学   62169篇
晶体学   1419篇
力学   6049篇
综合类   369篇
数学   12837篇
物理学   36833篇
  2023年   891篇
  2022年   1979篇
  2021年   2390篇
  2020年   2611篇
  2019年   2795篇
  2018年   3154篇
  2017年   3073篇
  2016年   3846篇
  2015年   2791篇
  2014年   3933篇
  2013年   5542篇
  2012年   5796篇
  2011年   6093篇
  2010年   4781篇
  2009年   4739篇
  2008年   5007篇
  2007年   4622篇
  2006年   4268篇
  2005年   3752篇
  2004年   3379篇
  2003年   2972篇
  2002年   3086篇
  2001年   2739篇
  2000年   2113篇
  1999年   1744篇
  1998年   1676篇
  1997年   1478篇
  1996年   1440篇
  1995年   1184篇
  1994年   1265篇
  1993年   1177篇
  1992年   1115篇
  1991年   1176篇
  1990年   1177篇
  1989年   1076篇
  1988年   944篇
  1987年   933篇
  1986年   912篇
  1985年   949篇
  1984年   937篇
  1983年   841篇
  1982年   811篇
  1979年   811篇
  1978年   834篇
  1977年   816篇
  1976年   932篇
  1975年   820篇
  1974年   856篇
  1973年   855篇
  1972年   756篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
On the example of the effect of an atmospheric wave with given amplitude on the density oscillations of minor gas constituents near the mesopause (at heights 80–90 km, we consider the influence of the quasi-resonant periodic spatial transport on a distributed system responding subharmonically to a periodic external action (diurnal sunlight variations). Numerical modeling revealed the formation of a coherent horizontal distribution of the dynamical variables (i.e., the concentrations of small constituents). Application of this effect to the mesopause conditions is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 47, No. 9, pp. 739–752, September, 2004.  相似文献   
42.
43.
We consider a particular case of the matrix Carleman problem for two pairs of functions in a ring and find a constructive solution of this problem. In addition, we propose an algorithm for the construction of solutions for two infinite systems of smooth transition and for a system of two singular equations of special type. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 49, No. 5, pp. 662–671, May, 1997  相似文献   
44.
A model of an expanding and rotating universe is constructed in the framework of general relativity. The parameters of the model are compared with the fundamental observables and shown to be in good agreement.Kaluzhsk Branch, N. É. Bauman Moscow State Technical University (MGTU). Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 71–77, June, 1993.  相似文献   
45.
46.
47.
Various approaches to the preparation and verification of single-molecule single crystals are discussed for polyethylene and poly (oxyethylene). Analytic tools are electron microscopy, electron diffraction, and differential scanning calorimetry. The main difficulty in producing a single-molecule single crystal is to keep crystals from joining during growth.  相似文献   
48.
Diffuse x-ray scattering (DXS) is used to study the formation of microdefects (MDs) in heat-treated dislocation-free large-diameter silicon wafers with vacancies. The DXS method is shown to be efficient for investigating MDs in silicon single crystals. Specific defects, such as impurity clouds, are found to form in the silicon wafers during low-temperature annealing at 450°C. These defects are oxygen-rich regions in the solid solution with diffuse coherent interfaces. In the following stages of decomposition of the supersaturated solid solution, oxide precipitates form inside these regions and the impurity clouds disappear. As a result of the decomposition of the supersaturated solid solution of oxygen, interstitial MDs form in the silicon wafers during multistep heat treatment. These MDs lie in the {110} planes and have nonspherical displacement fields. The volume density and size of MDs forming in the silicon wafers at various stages of the decomposition are determined.  相似文献   
49.
This work reports a new synthetic approach for single‐phase TiO2 nanomaterials by solvothermal treatment of titanium tetrachloride in acetone at 80–110 °C. Small, uniform, and yet size‐tunable (5–10 nm) anatase titania nanocrystallites were obtained using a low concentration of TiCl4 in acetone (i.e., at molar ratios of TiCl4/acetone ≤ 1:15) in the temperature range of 80–110 °C, while rutile nanofibers were synthesized using a high concentration of TiCl4 (e.g., TiCl4/acetone = 1:10) at 110 °C. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
50.
Modifications are introduced into the large-particle method to make it possible to use the method in arbitrary nonrectangular computing nets in the study of the flow of an ideal compressible gas over mobile thin permeable membranes. A problem in the aeroelasticity of a parachute is stated. An example is given of the solution of a problem in the stationary formulation for an axially symmetric parachute in the wake of a cylindrical leading body for supersonic flow.Translated fromDinamicheskie Sistemy, No. 6, 1987, pp. 16–22  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