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   10324篇
  免费   258篇
  国内免费   30篇
化学   5954篇
晶体学   213篇
力学   223篇
数学   1694篇
物理学   2528篇
  2023年   46篇
  2022年   187篇
  2021年   206篇
  2020年   140篇
  2019年   190篇
  2018年   193篇
  2017年   184篇
  2016年   338篇
  2015年   274篇
  2014年   366篇
  2013年   788篇
  2012年   516篇
  2011年   583篇
  2010年   451篇
  2009年   421篇
  2008年   506篇
  2007年   483篇
  2006年   425篇
  2005年   360篇
  2004年   326篇
  2003年   320篇
  2002年   235篇
  2001年   196篇
  2000年   182篇
  1999年   138篇
  1998年   146篇
  1997年   118篇
  1996年   111篇
  1995年   149篇
  1994年   93篇
  1993年   75篇
  1992年   98篇
  1991年   75篇
  1990年   91篇
  1989年   90篇
  1988年   86篇
  1987年   73篇
  1986年   88篇
  1985年   131篇
  1984年   150篇
  1983年   82篇
  1982年   80篇
  1981年   87篇
  1980年   101篇
  1979年   69篇
  1978年   74篇
  1977年   82篇
  1976年   67篇
  1975年   65篇
  1974年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C 1 transformation.  相似文献   
12.
JPC – Journal of Planar Chromatography – Modern TLC - Flavonoid glycosides are much more polar than their aglycones and the two groups of compounds are difficult to separate by planar...  相似文献   
13.
The paper presents a procedure for constructing smooth actions of finite perfect groups on spheres with fixed point sets having certain prescribed properties (Theorem A); in particular, having any prescribed configuration of Chern and Pontryagin numbers (Corollary C). The main ingredients used are equivariant thickening and equivariant surgery.  相似文献   
14.
An effective algorithm to construct the Darboux matrix based on the dressing method is proposed. Our approach consists in representing the linear problem as a system of algebraic constraints on two matrices. The Darboux matrix is determined from the requirement that the Darboux-Bäcklund transformation preserves these constraints. A non-isospectral deformation of the derivative nonlinear Schrödinger equation is discussed as an example.  相似文献   
15.
The disintegration of bromhexin tablets was monitored by magnetic resonance imaging. The fast imaging method FLASH with spoiling gradients was used to obtain images of the tablets in short time intervals. The rate of the disintegration depends on the preparation method, kind and percentage of the carrier (polyethylene glycol, lactose). Solid dispersion with slow evaporation of solvent yields materials with decreased dissolution rate. Increasing molecular mass of polyethylene glycol and its percentage content also hampers disintegration.  相似文献   
16.
Supported by SFB 170 “Geometrie und Analysis” at the University of G?ttingen  相似文献   
17.
The aim of this paper is to introduce the notions of floor and ceiling functions related to graph edge-decompositions intot mutually isomorphic parts. It is shown that, given any natural numbert, uniform and extremal t-packing andt-covering exist for each complete graph and each complete bipartite graph. Extremal in this context means that both a remainder and a surplus are absolutely minimum. In proofs, decompositions of multigraphs into matchings are involved. Open problems and conjectures are stated.  相似文献   
18.
Finitely generated linear semigroups over a field K that have intermediate growth are considered. New classes of such semigroups are found and a conjecture on the equivalence of the subexponential growth of a finitely generated linear semigroup S and the nonexistence of free noncommutative subsemigroups in S, or equivalently the existence of a nontrivial identity satisfied in S, is stated. This ‘growth alternative’ conjecture is proved for linear semigroups of degree 2, 3 or 4. Certain results supporting the general conjecture are obtained. As the main tool, a new combinatorial property of groups is introduced and studied.  相似文献   
19.
Hyperfine Interactions - Rotational J=1→J=0 transitions in muonic molecule, (3Heμd) J ++, in [(3Heμd)++,2e]–D and [(3Heμd)++,e]+–D collisions are considered. The...  相似文献   
20.
Tunable properties of light propagation in photonic crystal fibers filled with liquid crystals, called photonic liquid crystal fibers (PLCFs) are presented. The propagation properties of PLCFs strongly depend on contrast between refractive indices of the solid core (pure silica glass) and liquid crystals (LCs) filing the holes of the fiber. Due to relatively strong thermo-optical effect, we can change the refractive index of the LC by changing its temperature. Numerical analysis of light propagation in PLCF, based on two simulation methods, such as finite difference (FD) and multipole method (MM) is presented. The numerical results obtained are in good agreement with our earlier experimental results presented elsewhere [1].  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