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   2800篇
  免费   167篇
  国内免费   112篇
化学   933篇
晶体学   31篇
力学   39篇
综合类   11篇
数学   933篇
物理学   1132篇
  2023年   10篇
  2022年   21篇
  2021年   40篇
  2020年   32篇
  2019年   44篇
  2018年   41篇
  2017年   60篇
  2016年   51篇
  2015年   48篇
  2014年   49篇
  2013年   172篇
  2012年   89篇
  2011年   201篇
  2010年   193篇
  2009年   392篇
  2008年   339篇
  2007年   271篇
  2006年   201篇
  2005年   132篇
  2004年   70篇
  2003年   80篇
  2002年   73篇
  2001年   51篇
  2000年   54篇
  1999年   45篇
  1998年   47篇
  1997年   30篇
  1996年   15篇
  1995年   30篇
  1994年   43篇
  1993年   45篇
  1992年   13篇
  1991年   9篇
  1990年   4篇
  1989年   5篇
  1988年   17篇
  1987年   9篇
  1986年   6篇
  1985年   7篇
  1984年   5篇
  1982年   5篇
  1981年   3篇
  1980年   7篇
  1979年   7篇
  1978年   4篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1968年   1篇
排序方式: 共有3079条查询结果,搜索用时 328 毫秒
21.
22.
We estimate the concentration functions of n-fold convolutions of one-dimensional probability measures. The Kolmogorov–Rogozin inequality implies that for nondegenerate distributions these functions decrease at least as O(n –1/2). On the other hand, Esseen(3) has shown that this rate is o(n –1/2) iff the distribution has an infinite second moment. This statement was sharpened by Morozova.(9) Theorem 1 of this paper provides an improvement of Morozova's result. Moreover, we present more general estimates which imply the rates o(n –1/2).  相似文献   
23.
Least-squares finite difference (LSFD) method, one of mesh-free methods, is used to solve slider air bearings problem through discritizing the generalized Reynolds equation into nonlinear systems of algebraic equations. Two approximation schemes for the linearization of these equations are presented and compared. And, some new techniques to search supporting points for the reference node in the mesh-free method were proposed and explored. Therefore, these improvements eliminate some potential limitation of the LSFD method previously published and further facilitate its employment in complex slider models. Advanced step slider as an example of negative pressure sliders is simulated and verified using the improved LSFD mesh-free method in head disk systems.  相似文献   
24.
Epitaxial and c-axis oriented double perovskite Sr2CrWO6 thin films were prepared on SrTiO3 (100) and LaAlO3 (100) substrates by pulsed-laser deposition. Structural, magnetic and transport properties were found to be sensitive to the gas conditions employed during the deposition. A small amount of oxygen along with Ar during the deposition was found to be essential for B-site ordering; such films displayed lattice parameters close to the bulk value and display ferromagnetic metallic behavior. The Curie temperature observed above 500 K in these films is higher than bulk Sr2CrWO6 samples. Films grown without oxygen were observed to have long c-parameter and no B-site ordering; they were non-magnetic and semiconducting.  相似文献   
25.
Simultaneous imaging of laser-induced fluorescence of toluene and 3-pentanone was used to determine the local absolute oxygen and residual gas concentrations present within an engine. The technique utilizes the different sensitivities of the laser-excited molecules to quenching by molecular oxygen as a means to determine quantitative images of in-cylinder oxygen concentrations. The difference in the amount of oxygen available between two operating conditions was investigated. Results are in agreement with measurements in the exhaust gas. Received: 4 June 2002 / Published online: 8 August 2002  相似文献   
26.
基于零点的函数K图和dj图的转换   总被引:9,自引:7,他引:2       下载免费PDF全文
介绍了函数的最大项展开式和CRM展开式及其图形表示,提出函数K图和dj图的零点的概念,并以此为基础讨论了基于零点的函数K图和dj图之间的转换方法。  相似文献   
27.
The low-energy excitation spectra of metal dimers are determined by solving exactly a realistic many-body Hamiltonian with inter- and intra-atomic Coulomb interactions. Our results for Cu2 and Ag2 are in very good agreement with the excitation energies derived from recent photodetachment experiments. The characteristics of the many-body excited states in these clusters are briefly discussed.  相似文献   
28.
For semi-interpenetrating polymer networks (semi-IPNs) based on an incompatible polyurethane network/linear polymethylmethacrylate pair formed in situ in the presence of 3d metal chelates, we have studied the effect of the system composition on the kinetics of formation of the components and the nature of complex formation between the metal compound and the polymer matrix. The ratio of the system components has been shown to have an effect on the selection of the macroligand in formation of complexes of the metal chelate with the polar groups of the semi-IPN, where the general character of the kinetic behavior for the formation of the network and the linear polymer is preserved. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 6, pp. 351–356, November–December, 2006.  相似文献   
29.
徐志栋  冯殿忠 《合成化学》1998,6(3):332-334
首次合成了喹喔啉-2,3-二甲酰胺(Qxda)与3d过渡金属的三种固体配合物:M(Qxda)2cl2(M=Co(I),Ni(I),Cu(Ⅱ)。通过元素分析,摩尔电导,红外光谱,电子光谱,磁化率,热分析等手段对配合物的组成和性质进行了研究。  相似文献   
30.
Designing peptide inhibitors of the p53-MDM2 interaction against cancer is of wide interest. Computational modeling and virtual screening are a well established step in the rational design of small molecules. But they face challenges for binding flexible peptide molecules that fold upon binding. We look at the ability of five different peptides, three of which are intrinsically disordered, to bind to MDM2 with a new Bayesian inference approach (MELD × MD). The method is able to capture the folding upon binding mechanism and differentiate binding preferences between the five peptides. Processing the ensembles with statistical mechanics tools depicts the most likely bound conformations and hints at differences in the binding mechanism. Finally, the study shows the importance of capturing two driving forces to binding in this system: the ability of peptides to adopt bound conformations (ΔGconformation) and the interaction between interface residues (ΔGinteraction).  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