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   1469篇
  免费   22篇
  国内免费   2篇
化学   865篇
晶体学   10篇
力学   52篇
数学   162篇
物理学   404篇
  2022年   11篇
  2021年   19篇
  2020年   12篇
  2019年   15篇
  2017年   8篇
  2016年   17篇
  2015年   18篇
  2014年   22篇
  2013年   65篇
  2012年   56篇
  2011年   73篇
  2010年   44篇
  2009年   55篇
  2008年   70篇
  2007年   77篇
  2006年   66篇
  2005年   66篇
  2004年   53篇
  2003年   47篇
  2002年   37篇
  2001年   31篇
  2000年   33篇
  1999年   18篇
  1998年   10篇
  1997年   15篇
  1996年   32篇
  1995年   32篇
  1994年   33篇
  1993年   25篇
  1992年   24篇
  1991年   17篇
  1990年   17篇
  1989年   21篇
  1988年   17篇
  1987年   16篇
  1986年   28篇
  1985年   14篇
  1984年   21篇
  1983年   16篇
  1982年   9篇
  1981年   20篇
  1980年   15篇
  1979年   12篇
  1978年   13篇
  1977年   18篇
  1976年   13篇
  1975年   22篇
  1974年   13篇
  1973年   13篇
  1972年   10篇
排序方式: 共有1493条查询结果,搜索用时 15 毫秒
11.
12.
13.
A linear projection R on a Jordan*-triple A is said to be structuralprovided that, for all elements a, b and c in A, the equality{Rab Rc} = R{a Rbc} holds. A subtriple B of A is said to becomplemented if A = B + Ker(B), where Ker(B) = {aA: {B a B}= 0}. It is shown that a subtriple of a JBW*-triple is complementedif and only if it is the range of a structural projection. A weak* closed subspace B of the dual E* of a Banach space Eis said to be an N*-ideal if every weak* continuous linear functionalon B has a norm preserving extension to a weak* continuous linearfunctional on E* and the set of elements in E which attain theirnorm on the unit ball in B is a subspace of E. It is shown thata subtriple of a JBW*-triple A is complemented if and only ifit is an N*-ideal, from which it follows that complemented subtriplesof A are weak* closed, and structural projections on A are weak*continuous and norm non-increasing. It is also shown that everyN*-ideal in A possesses a triple product with respect to whichit is a JBW*-triple which is isomorphic to a complemented subtripleof A.  相似文献   
14.
15.
Micellar electrokinetic chromatography (MEKC) of highly hydrophobic compounds is generally difficult using sodium dodecyl sulfate micellar solutions. The polymeric surfactant, polysodium undecyl sulfate (poly-SUS) has been used to separate moderately to highly hydrophobic polychlorinated biphenyl (PCB) congeners by MEKC in the absence of cyclodextrins. Parameters such as concentration of acetonitrile (ACN), polymeric surfactant concentration, and the effect of pH were examined. Optimum MEKC conditions to get baseline resolution of nine PCBs was 7.5 mM borate in 40% (v/v) ACN fraction buffered at pH 9.2 using 0.5% (w/v) poly-SUS. The applied voltage was 30 kV and the temperature was maintained at 25 degrees C. Elution order for each PCB congener was found to be dependent on the degree of chlorination and hydrophobic character.  相似文献   
16.
Nonlinear-response theory of nonequilibrium molecular-dynamics simulation algorithms is considered under the imposition of an arbitrary steady-state flow field. It is demonstrated that the SLLOD and DOLLS algorithms cannot be used for general flows, although the SLLOD algorithm is rigorous for planar Couette flow. Following the same procedure used to establish SLLOD as the valid algorithm for planar Couette flow [D. J. Evans and E. P. Morriss, Phys. Rev. A 30, 1528 (1984)], it is demonstrated that the p-SLLOD algorithm is valid for arbitrary flows and produces the correct nonlinear response of the viscous pressure tensor.  相似文献   
17.
Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na2PdCl4 afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC6H4C(O)H) with H2NC6H4Bpin (pin=1,2-O2C2Me4) afforded the boron-containing Schiff bases, 2-HOC6H4C(H)=NC6H4Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na2PdCl4 afforded complexes of the type PdL2 (4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus.  相似文献   
18.
Amidoalkylation of three benzoheterocycles, benzimidazole-2-one, 1,3-dihydrobenzo[c]-thiophene 2,2-dioxide and 1,3-dihydro-2,1,3-benzothiadiazole using N-acylhippuric acids was successful. The corresponding phenylglycine analogs were prepared by removal of the N-acyl protecting group.  相似文献   
19.
20.
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