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   616篇
  免费   10篇
  国内免费   9篇
化学   346篇
晶体学   5篇
力学   23篇
数学   87篇
物理学   174篇
  2021年   6篇
  2020年   8篇
  2019年   8篇
  2018年   3篇
  2016年   11篇
  2015年   7篇
  2014年   6篇
  2013年   33篇
  2012年   31篇
  2011年   33篇
  2010年   17篇
  2009年   20篇
  2008年   27篇
  2007年   27篇
  2006年   30篇
  2005年   32篇
  2004年   28篇
  2003年   22篇
  2002年   20篇
  2001年   13篇
  2000年   11篇
  1999年   5篇
  1997年   10篇
  1996年   15篇
  1995年   14篇
  1994年   18篇
  1993年   11篇
  1992年   12篇
  1991年   11篇
  1990年   11篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   4篇
  1985年   4篇
  1984年   12篇
  1983年   10篇
  1982年   7篇
  1981年   5篇
  1980年   7篇
  1979年   8篇
  1978年   10篇
  1977年   13篇
  1976年   6篇
  1975年   6篇
  1974年   5篇
  1973年   11篇
  1969年   2篇
  1966年   3篇
  1965年   2篇
排序方式: 共有635条查询结果,搜索用时 437 毫秒
41.
A convenient laboratory scale preparation of cyanogen has been developed. This new method generates cyanogen from the pyrolysis of diacetyl-glyoxime which can be easily prepared from glyoxime.  相似文献   
42.
Journal of Fluorescence - Graphene oxide is well known for its adsorption properties with aromatic compounds. In this study, graphene oxide and eco-friendly ternary CuInS2/ZnS QDs were used to...  相似文献   
43.
Hepatitis C is a global health problem. While many drug companies have active R&D efforts to develop new drugs for treating Hepatitis C virus (HCV), most target the viral enzymes. The HCV glycoprotein E2 has been shown to play an essential role in hepatocyte invasion by binding to CD81 and other cell surface receptors. This paper describes the use of AutoDock to identify ligand binding sites on the large extracellular loop of the open conformation of CD81 and to perform virtual screening runs to identify sets of small molecule ligands predicted to bind to two of these sites. The best sites selected by AutoLigand were located in regions identified by mutational studies to be the site of E2 binding. Thirty-six ligands predicted by AutoDock to bind to these sites were subsequently tested experimentally to determine if they bound to CD81-LEL. Binding assays conducted using surface Plasmon resonance revealed that 26 out of 36 (72 %) of the ligands bound in vitro to the recombinant CD81-LEL protein. Competition experiments performed using dual polarization interferometry showed that one of the ligands predicted to bind to the large cleft between the C and D helices was also effective in blocking E2 binding to CD81-LEL.  相似文献   
44.
The magnetic field distribution around the vortices in TmNi2B2C in the paramagnetic phase was studied experimentally as well as theoretically. The vortex form factor, measured by small-angle neutron scattering, is found to be field independent up to 0.6Hc2 followed by a sharp decrease at higher fields. The data are fitted well by solutions to the Eilenberger equations when paramagnetic effects due to the exchange interaction with the localized 4f Tm moments are included. The induced paramagnetic moments around the vortex cores act to maintain the field contrast probed by the form factor.  相似文献   
45.
46.
An efficient stereoselective synthesis of C4-12 fragment of the cembranoids, sarcophytonolides E-G and L and C5-11 fragment of sarcophytonolide L is described. The C4-12 building block is efficiently assembled starting from chiral pool material (R)-carvone employing the Baeyer-Villiger oxidation, modified Knoevenagel condensation and asymmetric dihydroxylation as the key steps. The synthesis of C5-11 fragment is based on orthoester Johnson-Claisen rearrangement as the key step.  相似文献   
47.
The -th local cohomology module of a finitely generated graded module over a standard positively graded commutative Noetherian ring , with respect to the irrelevant ideal , is itself graded; all its graded components are finitely generated modules over , the component of of degree . It is known that the -th component of this local cohomology module is zero for all > 0$">. This paper is concerned with the asymptotic behaviour of as .

The smallest for which such study is interesting is the finiteness dimension of relative to , defined as the least integer for which is not finitely generated. Brodmann and Hellus have shown that is constant for all (that is, in their terminology, is asymptotically stable for ). The first main aim of this paper is to identify the ultimate constant value (under the mild assumption that is a homomorphic image of a regular ring): our answer is precisely the set of contractions to of certain relevant primes of whose existence is confirmed by Grothendieck's Finiteness Theorem for local cohomology.

Brodmann and Hellus raised various questions about such asymptotic behaviour when f$">. They noted that Singh's study of a particular example (in which ) shows that need not be asymptotically stable for . The second main aim of this paper is to determine, for Singh's example, quite precisely for every integer , and, thereby, answer one of the questions raised by Brodmann and Hellus.

  相似文献   

48.
This article describes the roadside traffic noise surveys conducted in heavily built-up urban areas in Hong Kong. Noise measurements were carried out along 18 major roads in 1999. The measurement data included L10, L50, L90, Leq, Lmax, the number of light vehicles, the number of heavy vehicles, the total traffic flow, and the average speed of vehicles. Statistical analysis using the analysis of variance (ANOVA) and Tukey test (p<0.05) reveals that the total traffic flow and the number of heavy vehicles are the most significant factors of urban traffic noise. Multiple regression was used to derive a set of empirical formulas for predicting L10 noise level due to road traffic. The accuracy of these empirical formulas is quantified and compared to that of another widely used prediction model in Hong Kong--the Calculation of Road Traffic Noise. The applicability of the selected multiple regression model is validated by the noise measurements performed in the winter of 2000.  相似文献   
49.
Summary In this paper we study the Dirichlet problem for the minimal surface equation in a open set Ω without any assumption about the regularity of ϖΩ. We prove an existence theorem using only the pseudoconvexity of Ω.
Riassunto In questo lavoro studiamo il problema di Dirichlet per l'equazione delle superfici minime in un aperto Ω diR n sulla cui frontiera non si fa nessuna ipotesi di regolarità. Si ottiene un teorema di esistenza usando la sola pseudoconvessità di Ω.
  相似文献   
50.
Summary In this note we discuss the invariant properties of the group of homographies which leave a third order differential element E3 invariant.  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