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   2971篇
  免费   96篇
  国内免费   18篇
化学   1679篇
晶体学   47篇
力学   106篇
数学   632篇
物理学   621篇
  2023年   24篇
  2022年   41篇
  2021年   55篇
  2020年   71篇
  2019年   84篇
  2018年   120篇
  2017年   124篇
  2016年   137篇
  2015年   102篇
  2014年   148篇
  2013年   372篇
  2012年   165篇
  2011年   188篇
  2010年   176篇
  2009年   124篇
  2008年   157篇
  2007年   140篇
  2006年   101篇
  2005年   85篇
  2004年   80篇
  2003年   62篇
  2002年   61篇
  2001年   34篇
  2000年   24篇
  1999年   25篇
  1998年   27篇
  1997年   28篇
  1996年   20篇
  1995年   13篇
  1994年   9篇
  1990年   6篇
  1989年   10篇
  1988年   8篇
  1987年   10篇
  1986年   11篇
  1985年   27篇
  1984年   16篇
  1983年   11篇
  1982年   14篇
  1981年   19篇
  1980年   8篇
  1979年   14篇
  1978年   9篇
  1977年   13篇
  1976年   21篇
  1975年   11篇
  1974年   16篇
  1973年   12篇
  1968年   9篇
  1967年   6篇
排序方式: 共有3085条查询结果,搜索用时 15 毫秒
1.
Suppose there exists a global solution u to the incompressible Navier–Stokes equations, such that u∈Ct(H?1/2). We prove that its H?1/2 norm goes to 0 at infinity. We next use this fact to control the L2t(H?3/2) norm of u, and finally we prove that such a solution is stable. To cite this article: I. Gallagher et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 289–292.  相似文献   
2.
3.
4.
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
5.
We report on the status of the LPCTrap experiment, devoted to measure the β–ν angular correlation in the pure Gamow–Teller decay of 6He. This measurement is motivated by the search for the presence of tensor type contributions to the weak interaction. The 6He ions are confined in a novel transparent Paul trap. The β particles and the recoil ions are detected in coincidence to deduce the angular correlation parameter. The commissioning run performed in 2005 has given the proof of principle of this experiment. Up to 105 coincidences were recorded during a second run in 2006.  相似文献   
6.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U n by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U n . Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure of U n , compute the moments of T(t) and establish asymptotic formulas. Received: January 26, 2007.  相似文献   
7.
We give a concise review and extension of S-procedure that is an instrumental tool in control theory and robust optimization analysis. We also discuss the approximate S-Lemma as well as its applications in robust optimization.The many suggestions and detailed corrections of an anonymous referee are gratefully acknowledged.  相似文献   
8.
Ti(IV) as TiCl3(O3SCF3) and TiO(O2CCF3)2 are used as efficient catalysts for oxidative coupling of aliphatic, aromatic and heteroaromatic thiols to their disulfides in the presence of NaI under air atmosphere.  相似文献   
9.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous, and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide.  相似文献   
10.
This article reports a synthetic method for a norbornene–ethylene–styrene (N‐E‐S) terpolymer, which has not been well investigated so far, via incorporation of styrene (S) into vinyl‐type norbornene–ethylene (N‐E) copolymers catalyzed by a substituted ansa‐fluorenylamidodimethyltitanium [Me2Si(3,6‐tBu2Flu)(tBuN)]TiMe2 catalyst ( I ) activated with a [Ph3C][B(C6F5)4]/Al(iBu)3 cocatalyst at room temperature in toluene. The resulting terpolymerization product contained the targeted N‐E‐S terpolymer and the contaminated homopolymers, which were then able to be completely removed by solvent fractionation techniques. While homopolystyrene was easily extracted by fractionation with methylethylketone as a soluble part, homopolyethylene and a trace amount of homopolynorbornene could be perfectly separated by fractionation with chloroform as insoluble parts. The detail characterizations of a chloroform‐soluble polymer with gel permeation chromatography, nuclear magnetic resonance, and differential scanning calorimetry analyses proved that it contained a true N‐E‐S terpolymer with long N‐E sequences incorporated with isolated or short styrene sequences. The homogeneity of the morphology together with a single glass transition temperature that proportionally decreased with the increase of the styrene contents indicated that the N‐E‐S terpolymer obtained in this work is a random polymer with an amorphous structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2765–2773, 2007  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