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   8394篇
  免费   188篇
  国内免费   11篇
化学   4997篇
晶体学   72篇
力学   114篇
数学   1271篇
物理学   2139篇
  2021年   88篇
  2020年   113篇
  2019年   128篇
  2018年   150篇
  2017年   154篇
  2016年   233篇
  2015年   226篇
  2014年   246篇
  2013年   508篇
  2012年   381篇
  2011年   450篇
  2010年   342篇
  2009年   296篇
  2008年   380篇
  2007年   303篇
  2006年   335篇
  2005年   249篇
  2004年   241篇
  2003年   187篇
  2002年   207篇
  2001年   143篇
  2000年   146篇
  1999年   154篇
  1998年   110篇
  1997年   90篇
  1996年   113篇
  1995年   96篇
  1994年   108篇
  1993年   97篇
  1992年   91篇
  1991年   78篇
  1990年   94篇
  1989年   67篇
  1988年   64篇
  1987年   55篇
  1985年   83篇
  1984年   83篇
  1983年   75篇
  1982年   80篇
  1981年   73篇
  1980年   66篇
  1979年   69篇
  1978年   74篇
  1977年   78篇
  1976年   92篇
  1975年   76篇
  1974年   62篇
  1973年   61篇
  1972年   54篇
  1969年   53篇
排序方式: 共有8593条查询结果,搜索用时 15 毫秒
991.
If X is a convex surface in a Euclidean space, then the squared intrinsic distance function dist2(x, y) is DC (d.c., delta-convex) on X×X in the only natural extrinsic sense. An analogous result holds for the squared distance function dist2(x,F) from a closed set FX. Applications concerning r-boundaries (distance spheres) and ambiguous loci (exoskeletons) of closed subsets of a convex surface are given.  相似文献   
992.
In this paper, an asymptotic one dimensional model for a clamped curved rod is rigorously derived as a limit of respective three dimensional models. The rod is made of isotropic elastic, heat conductive linearly responding material. Asymptotic analysis is used with respect to the thickness of domains.  相似文献   
993.
We introduce a new class of the so‐called regularly varying sequences with respect to τ and state its properties. This class, on one hand, generalizes regularly varying sequences. On the other hand, it refines them and makes it possible to do a more sophisticated analysis in applications. We show a close connection with regular variation on time scales; thanks to this relation, we can use the existing theory on time scales to develop discrete regular variation with respect to τ. We reveal also a connection with generalized regularly varying functions. As an application, we study asymptotic behavior of solutions to linear difference equations; we obtain generalization and extension of known results. The theory also yields, in some way, a new view on the tests for convergence and divergence of series; we establish the statement that generalizes Raabe test and Bertrand test.  相似文献   
994.
Erdoğan  E.  Sánchez Pérez  E. A.  Gök  Ö. 《Positivity》2019,23(3):671-696
Positivity - This paper deals with bilinear operators acting in pairs of Banach function spaces that factor through the pointwise product. We find similar situations in different contexts of the...  相似文献   
995.
Methodology and Computing in Applied Probability - The paper concerns a method for assessing similarity of realisations of random sets based on a construction of their morphological skeletons and a...  相似文献   
996.
997.
An extension of the hard disc equation of state to planar hard dumbells is proposed and the determination of the characteristic geometric measures of dumbells with the reduced length L* ? ?2 is discussed. The second and third virial coefficients following from the proposed equation of state are evaluated and compared with the exact Monte Carlo data. Compressibility factors for four different elongations are calculated and compared with pseudoexperimental data and with results of other methods.  相似文献   
998.
The acetone molecule is investigated in its ground state and valence 1,3n-π*, 1,3π-π*, and 1,3σ-π* excited states and Rydberg 1,3n-3s, 1,3π-3?, 1,3n-3py and 1,3π-3py states using the CASSCF, CASPT2, and CCSD(T) methods. Equilibrium geometries of excited states are obtained and their changes with respect to the ground state are discussed. For most excited states the C2v symmetry of the ground state is lowered to the Cs symmetry. A series of valence vertical and adiabatic excitation energies is presented along with excitation energies for Rydberg states. The main body of the paper contains Finite-Field Perturbation Theory (FFPT) calculations of electric properties of the vertically as well as geometry relaxed excited states. Dipole moments of valence excited states decrease significantly upon excitation, being about one half of the ground state dipole moment. Polarizabilities usually change upon excitation much less (increase by about 30%) but hyperpolarizabilities are enhanced up to one or two orders of magnitude. The orientation of the dipole moment is reversed in some vertically excited Rydberg states. Properties of the ground and excited states are discussed considering alterations of the electronic structure and shifts in the geometry.  相似文献   
999.
1000.
A flexible framework for Group Decision Support on PCs in Microsoft Windows environment is presented. WINGDSS does not replace human judgment but highly supports the entire process of decision making, from problem structuring to post-decision analysis. The latest version of WINGDSS is a modular, open system with a dynamical connection to relational databases, an interpreter for defining problem specific evaluation procedures, a lot of interactive features from setting up the tree of criteria until the sensitivity analysis on individual/group ranking. By providing tools for recursively redefining the decision problem, WINGDSS helps the decision makers in achieving a result satisfactory to the whole group.Research supported in part by the Hungarian Foundation for Scientific Research, Grant No. 2568 and by the Hungarian National Committee for Technical Research and Development, Grant No. 93-97-67-0553.  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