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   278816篇
  免费   1604篇
  国内免费   803篇
化学   127874篇
晶体学   4139篇
力学   16881篇
综合类   10篇
数学   53286篇
物理学   79033篇
  2021年   1973篇
  2020年   2009篇
  2019年   2566篇
  2018年   13889篇
  2017年   13703篇
  2016年   10759篇
  2015年   3151篇
  2014年   4565篇
  2013年   8859篇
  2012年   10489篇
  2011年   18263篇
  2010年   11944篇
  2009年   12539篇
  2008年   14029篇
  2007年   16103篇
  2006年   6876篇
  2005年   7149篇
  2004年   7094篇
  2003年   7077篇
  2002年   6126篇
  2001年   5826篇
  2000年   4411篇
  1999年   3267篇
  1998年   2877篇
  1997年   2892篇
  1996年   2729篇
  1995年   2323篇
  1994年   2398篇
  1993年   2316篇
  1992年   2572篇
  1991年   2704篇
  1990年   2602篇
  1989年   2678篇
  1988年   2589篇
  1987年   2608篇
  1986年   2468篇
  1985年   3078篇
  1984年   3143篇
  1983年   2632篇
  1982年   2603篇
  1981年   2565篇
  1980年   2381篇
  1979年   2751篇
  1978年   2706篇
  1977年   2888篇
  1976年   2888篇
  1975年   2680篇
  1974年   2613篇
  1973年   2736篇
  1972年   2102篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
81.
The following areal objects are considered: an ether thread contracting two material points and a multidimensional ether fibre in the pseudo-Euclidean world of events. An ether space-time model with an arbitrarily determined Riemannian metric is constructed and the problem of the λ term in Einstein equations is discussed in this regard.  相似文献   
82.
A technique for variation of the temperature factor of free-flight models by varying their initial temperature is described. An experiment on a ballistic range is carried out with a free-flying supersonic blunt cone with a half-angle of 15° at a Mach number of 2.3. The flow at the cone base is studied in the transition range (from the laminar to turbulent flow) of Reynolds numbers. The base flow pattern is determined from the shadowgraphs of the flow about the models. The drag coefficient of the blunt cone at a zero angle of attack is found by processing trajectory data. It is found that the near wake geometries and the drag coefficients of the models tested at the laboratory temperature and a temperature of 120 K differ. Explanations of this effect are given.  相似文献   
83.
84.
85.
The sorption of carbon dioxide in glassy Poly(lactic acid) (PLA) films was studied by quartz crystal microbalance (QCM) at high pressures. Two thermal treatments, melted and quenched, were performed in PLA with two different L:D contents, 80:20 and 98:2, films and compared with a third thermal protocol, annealed, and used in a previous work. The results obtained show that for pressures higher than 2 MPa, the carbon dioxide solubility is larger in PLA 80:20 than in PLA 98:2, indicating that the L:D plays a dominant role on this property. The thermal treatments only affect the gas solubility in PLA 98:2. Sorption isotherms at temperatures 303, 313, and 323 K, below the glass transition temperature of the polymer, and pressures up to 5 MPa were measured and analyzed with three different models, the dual‐mode sorption model, the Flory–Huggins equation, and a modified dual‐mode sorption model where the Henry's law term was substituted by the Flory–Huggins equation. This last model performs especially well for CO2 in PLA 80:20, due to the convex upward curvature of the solubility isotherms for that system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 616–625, 2007  相似文献   
86.
87.
88.
Effect of errors of different origin on the efficiency of sound absorption by a local active absorber is investigated. Degradation of the efficiency of absorption because of the errors is shown to be minimal in the case when the controller does not detect the field of the secondary radiator. Estimates of admissible errors are presented. Several active absorber configurations in which the radiator does not affect the receiver are considered.  相似文献   
89.
This paper is in answer to the comment on the GRG paper: Lockerbie N.A. Gen. Rel. Grav. 36, 593 (2004), made by A.V. Sanders, G.T. Gillies (ibid.). N. A. Lockerbie is a member of the STEP (Satellite Test of the Equivalence Principle) Science Study Team, and an Associate of the Institute for Gravitational Research at the University of Glasgow, Scotland, UK.  相似文献   
90.
The spectra of the intensity fluctuations of light scattered by large (erythrocytes of whole blood) and small (vesicles of surgical bile) particles in natural conditions were studied. It is shown that photon correlation spectroscopy can be used in analysis of variations in the size of biological particles in normal and pathological conditions and as an express method of noninvasive diagnostics of diseases.  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