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   53349篇
  免费   1827篇
  国内免费   170篇
化学   35187篇
晶体学   398篇
力学   955篇
综合类   4篇
数学   9079篇
物理学   9723篇
  2023年   349篇
  2022年   550篇
  2021年   741篇
  2020年   784篇
  2019年   862篇
  2018年   941篇
  2017年   888篇
  2016年   1802篇
  2015年   1490篇
  2014年   1606篇
  2013年   3326篇
  2012年   3409篇
  2011年   3646篇
  2010年   2248篇
  2009年   2031篇
  2008年   3210篇
  2007年   3161篇
  2006年   2854篇
  2005年   2658篇
  2004年   2246篇
  2003年   1848篇
  2002年   1587篇
  2001年   1040篇
  2000年   938篇
  1999年   713篇
  1998年   548篇
  1997年   538篇
  1996年   662篇
  1995年   487篇
  1994年   502篇
  1993年   481篇
  1992年   449篇
  1991年   399篇
  1990年   369篇
  1989年   314篇
  1988年   308篇
  1987年   292篇
  1986年   316篇
  1985年   409篇
  1984年   411篇
  1983年   268篇
  1982年   313篇
  1981年   313篇
  1980年   317篇
  1979年   229篇
  1978年   231篇
  1977年   224篇
  1976年   200篇
  1975年   169篇
  1973年   165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Book Review     
Structural Chemistry -  相似文献   
52.
Paramagnetic pyrroline and 1,2,3,6-tetrahydropyridine derivatives of BODIPY and their diamagnetic analogs have been synthesized and characterized as novel redox double sensor and cation sensitive reagents.  相似文献   
53.
Summary He present work deals with estimations of the n-th linear polarization constant c(H)n of an n-dimensional real Hilbert space H. We provide some new lower bounds on the value of sup║y║=11,y> ... n,y>│, where x1, ... ,xn are unit vectors in H. In particular, the results improve an earlier estimate of Marcus. However, the intriguing conjecture c(H) n= nn/2 remains open.  相似文献   
54.
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities. We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary of the restricted region, indicating the occurrence of a phase transition. Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002  相似文献   
55.
56.
We describe a general method that enables us to obtain all the singular terms of helicity amplitudes of n-parton processes at one loop. The algorithm uses helicity amplitudes at tree level and simple color algebra. We illustrate the method by calculating the singular part of the one-loop helicity amplitudes of all 2 → 3 parton subprocesses. The results are used to derive the soft gluon limit of the cross sections of all 2 → 4 parton scattering subprocesses which provide a useful initial condition for the angular ordering approximation to coherent multiple soft gluon emission, incorporated in existing Monte Carlo simulation programs.  相似文献   
57.
The article referenced above was first published online on 30 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
58.
We investigate the existence and stability of solutions for higher-order two-point boundary value problems in case the differential operator is not necessarily positive definite, i.e. with superlinear nonlinearities. We write an abstract realization of the Dirichlet problem and provide abstract existence and stability results which are further applied to concrete problems.  相似文献   
59.
The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, aij, and three expressions of the crossed terms of the repulsive parameter, bij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of aij and bij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations.  相似文献   
60.
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