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   793417篇
  免费   8720篇
  国内免费   2233篇
化学   411684篇
晶体学   11300篇
力学   38371篇
综合类   26篇
数学   105218篇
物理学   237771篇
  2021年   7037篇
  2020年   7666篇
  2019年   8576篇
  2018年   11193篇
  2017年   11161篇
  2016年   16317篇
  2015年   9583篇
  2014年   15297篇
  2013年   35808篇
  2012年   27619篇
  2011年   33345篇
  2010年   24297篇
  2009年   24062篇
  2008年   31260篇
  2007年   30995篇
  2006年   28638篇
  2005年   25610篇
  2004年   23740篇
  2003年   21151篇
  2002年   20935篇
  2001年   22661篇
  2000年   17507篇
  1999年   13676篇
  1998年   11574篇
  1997年   11280篇
  1996年   10802篇
  1995年   9775篇
  1994年   9692篇
  1993年   9361篇
  1992年   10126篇
  1991年   10484篇
  1990年   10149篇
  1989年   9815篇
  1988年   9678篇
  1987年   9517篇
  1986年   9042篇
  1985年   11691篇
  1984年   12087篇
  1983年   9923篇
  1982年   10302篇
  1981年   9897篇
  1980年   9298篇
  1979年   9996篇
  1978年   10300篇
  1977年   10177篇
  1976年   10066篇
  1975年   9547篇
  1974年   9417篇
  1973年   9590篇
  1972年   6914篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
We establish a relation between stable distributions in probability theory and the fractional integral. Moreover, it turns out that the parameter of the stable distribution coincides with the exponent of the fractional integral. It follows from an analysis of the obtained results that equations with the fractional time derivative describe the evolution of some physical system whose time degree of freedom becomes stochastic, i.e., presents a sum of random time intervals subject to a stable probability distribution. We discuss relations between the fractal Cantor set (Cantor strips) and the fractional integral. We show that the possibility to use this relation as an approximation of the fractional integral is rather limited.  相似文献   
992.
For Hermitian adjoint differential operators, we consider the structure of Darboux–Bäcklund-type transformations in the class of parametrically dependent Hilbert spaces. By using the proposed new method, we obtain the corresponding integro-differential symbols of the operators of transformations in explicit form and consider the problem of their application to the construction of two-dimensional Lax-integrable nonlinear evolution equations and their Darboux–Bäcklund-type transformations.  相似文献   
993.
994.
995.
Applied Magnetic Resonance - We examined by electron spin resonance (ESR) spectroscopy the thermal decay of radicals as induced by γ-irradiation on pepper. Upon irradiation, the satellite...  相似文献   
996.
A nonlinear (in the cubic approximation) relaxation equation of state is derived for a rod containing cracks partially filled with an incompressible viscous liquid. The nonlinear effects of the self-action and interaction of low-and high-frequency longitudinal elastic waves propagating in such a rod are studied for the cases of identical and size-varied cracks. Linear and nonlinear acoustic parameters characterizing the self-action and interaction of elastic waves in a cracked rod are determined.  相似文献   
997.
The structure of neutron-rich beryllium isotopes has been investigated using different heavy-ion-induced transfer reactions. In neutron transfer reactions, the population of final states shows a strong sensitivity to the chosen core nucleus, i.e., the target nuclei 9Be or 10Be, respectively. Molecular rotational bands up to high excitation energies are observed with 9Be as the core due to its pronounced 2α-cluster structure, whereas only a few states at low excitation energies are populated with 10Be as the core. For 11Be, a detailed investigation has been performed for the three states at 3.41, 3.89, and 3.96 MeV, which resulted in the most probable spin-parity assignments 3/2+, 5/2?, and 3/2?, respectively. Furthermore, we have studied particle-hole states of 16C using the 13C(12C, 9C)16C reaction and found 14 previously unknown states. Using the 12C(12C, 9C)15C reaction, five new states were observed for 15C.  相似文献   
998.
Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies ranging from 40 to 180 keV. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
999.
We investigate analytically and numerically the influence of the type of the photorefractive nonlinear response on the periodic states (attractors) which occur during feedback controlled 2W-coupling and correspond to almost 100% diffraction efficiency of the dynamic index grating. In addition to the case of the local response typical, for example, for LiNbO3 crystals we consider the cases of nonlocal (diffusive) response (BaTiO3, SBN) and resonant response (DC-biased BSO, BTO, and BGO crystals). It is shown that the conditions for the transition to the periodic states and their apparent characteristics are strongly different for the two limiting cases above. Received 16 July 2002 / Received in final form 29 October 2002 Published online 4 March 2003  相似文献   
1000.
The uptake of technetium on bentonite materials has been studied from the point of view of the characterization of long-term radioactive elements behavior in nuclear waste repository. It is generally known that bentonite materials show an excellent cation-exchange capacity and on the other hand a poor uptake of anions. The aim of our research has been to find out the conditions suitable for technetium sorption on selected bentonite under oxidizing conditions. The influence of the addition of different materials (e.g., activated carbon, graphite, Fe2+, Fe) with bentonite, the effect of solid:aqueous phase ratio and a pH value on the percentage of technetium uptake and on the K d values were tested.This revised version was published online in November 2005 with corrections to the Cover Date.  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