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   1640篇
  免费   22篇
  国内免费   14篇
化学   935篇
晶体学   23篇
力学   43篇
数学   278篇
物理学   397篇
  2021年   13篇
  2020年   16篇
  2019年   15篇
  2018年   15篇
  2016年   25篇
  2015年   16篇
  2014年   22篇
  2013年   50篇
  2012年   75篇
  2011年   75篇
  2010年   48篇
  2009年   35篇
  2008年   65篇
  2007年   69篇
  2006年   68篇
  2005年   59篇
  2004年   57篇
  2003年   47篇
  2002年   52篇
  2001年   48篇
  2000年   44篇
  1999年   33篇
  1998年   21篇
  1997年   18篇
  1996年   24篇
  1995年   26篇
  1994年   32篇
  1993年   38篇
  1992年   32篇
  1991年   23篇
  1990年   26篇
  1989年   16篇
  1988年   24篇
  1987年   16篇
  1986年   19篇
  1985年   22篇
  1984年   24篇
  1983年   25篇
  1982年   22篇
  1981年   19篇
  1980年   22篇
  1979年   22篇
  1978年   18篇
  1977年   20篇
  1976年   25篇
  1975年   20篇
  1974年   27篇
  1973年   21篇
  1972年   11篇
  1967年   15篇
排序方式: 共有1676条查询结果,搜索用时 264 毫秒
91.
92.
93.
Recent experimental results from supernovae Ia observations have been interpreted to show that the rate of expansion of the universe is increasing. Other recent experimental results find strong indications that the universe is flat. In this paper, I investigate some solutions of Einstein's field equations which go smoothly between Schwarzschild's relativistic gravitational solution near a mass concentration to the Friedmann-Lemaître expanding universe solution. In particular, the static, curved-space extension of the Lemaître-Schwarzschild solution in vacuum is given. Uniqueness conditions are discussed. One of these metrics preserves the cosmological equation. We find that when the rate of expansion of the universe is increasing, space is broken up into domains of attraction. Outside a domain of attraction, the expansion of the universe is strong enough to accelerate a test particle away from the domain boundary. I give a domain-size–mass relationship. This relationship may very well be important to our understanding of the large scale structure of the universe.  相似文献   
94.
95.
Mao J  Baker DC 《Organic letters》1999,1(6):841-843
[formula: see text] A chiral rhodium complex, (R)-Cp*RhCl[(1S,2S)-p-TsNCH(C6H5)CH(C6H5)NH2] (1a, (S,S)-Cp*RhClTsDPEN), generated from [Cp*RhCl2]2 and (1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine [(S,S)-TsDPEN], and its enantiomer 1b were found to provide superior catalysts for the rapid, high-yielding, asymmetric transfer hydrogenation of some heterocyclic imines, using an HCO2H-Et3N azeotrope as the hydrogen source.  相似文献   
96.
97.
Jon Baker 《Chemical physics》1983,79(1):117-128
The excitation operator manifold required for the calculation of vertical IPs in the EOM/propagator formalism is extended to include products of five spin orbital field operators (refered to as the h5 basis). Spin symmetry adaptation is used for all the operators of this manifold. Using a direct diagonalization technique introduced previously the effect of inclusion of the h5 basis on calculated IPs is illustrated for various levels of approximation to the electron density by numerical applications to ethylene and water. The fourth-order terms thus introduced are shown to have greater magnitude than previously included third-order terms, in agreement with earlier work.  相似文献   
98.
A treatment and equation are developed whereby the maximum attainable resolution and transmission of an energy analyzer may be obtained without regard for specific electrode configuration employed to achieve focussing.  相似文献   
99.
100.
The decay of 12.4 y152Eu to152Sm and152Gd was studied in a high resolution singles measurement and two 4096×2048 Ge(Li)-Ge(Li) coincidence studies. Forty-five gates were analyzed in order to confirm or establish the placement of the γ rays as well as to accurately determine the intensities of the 12 doublets, which included several not previously reported. A new γ-β interband transition, 4 γ + →2 β + (561.4 keV), a possible 3 γ + →2 β + (423.7 keV) transition, and a new 330.9 keV transition between the 4 γ + level and theI π K=3?0 octupole level were established from coincidence data. Levels at 1757.0 keV in152Sm and 1282.5, 1318.7, and 1692.2 keV in152Gd are now established on the basis of coincidence data. These data also establish for the first time the population in the152Eu decay levels at 1680.0 and 1047.9 keV in152Sm and152Gd, respectively, as well as a new level at 1700.8 keV in152Sm.  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