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   9238篇
  免费   372篇
  国内免费   692篇
化学   758篇
晶体学   7篇
力学   378篇
综合类   54篇
数学   7946篇
物理学   1159篇
  2023年   97篇
  2022年   80篇
  2021年   99篇
  2020年   160篇
  2019年   179篇
  2018年   223篇
  2017年   215篇
  2016年   239篇
  2015年   163篇
  2014年   357篇
  2013年   625篇
  2012年   407篇
  2011年   397篇
  2010年   379篇
  2009年   590篇
  2008年   700篇
  2007年   596篇
  2006年   533篇
  2005年   470篇
  2004年   332篇
  2003年   395篇
  2002年   366篇
  2001年   276篇
  2000年   277篇
  1999年   292篇
  1998年   232篇
  1997年   260篇
  1996年   147篇
  1995年   140篇
  1994年   115篇
  1993年   80篇
  1992年   71篇
  1991年   68篇
  1990年   72篇
  1989年   53篇
  1988年   56篇
  1987年   41篇
  1986年   40篇
  1985年   59篇
  1984年   62篇
  1983年   25篇
  1982年   45篇
  1981年   38篇
  1980年   47篇
  1979年   29篇
  1978年   36篇
  1977年   41篇
  1976年   26篇
  1974年   16篇
  1973年   16篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
201.
Using optimal exponents for B through Ne given by Dunning and those for Al through Ar by Woon and Dunning, d-type contracted polarization functions (2d/1d), (3d/1d), and (3d/2d) are generated from natural orbitals of atomic single and double excitation configuration interaction (SDCI) calculations, where the numbers before and after the slash are those of the primitive and contracted Gaussian type functions. The resulting contracted functions are tested on N2 and P2 molecules by self-consistent field and SDCI calculations, which clarify characteristics of the present polarization functions. Received: 5 June 1997 / Accepted: 20 August 1997  相似文献   
202.
Summary Adsorption properties of activated carbon cloth were investigated by gas-solid chromatography. Retention of several organic compounds was measured in the temperature range from 200 to 250°C. The gas/solid distribution coefficients and the related thermodynamic function of adsorption at zero surface coverage were determined. The obtained experimental data were used to explain the adsorbent-adsorbate interaction.  相似文献   
203.
An account is given of the use of Gaussian quadrature product formulae in the evaluation of certain six-dimensional, two-centre integrals involving one-electron Green's functions. These integrals occur in a new molecular variational principle recently proposed by Hall, Hyslop and Rees [1] from which an approximate energy may be derived which can be shown to be at least as good as that obtained from the Rayleigh-Ritz principle. Reductions in computing time are realized by removing certain singularities using a subtraction technique and also by using an empirically determined Richardson-type extrapolation formula.This paper was presented during the session on numerical integration methods for molecules of the 1970 Quantum Theory Conference in Nottingham. It has been revised in the light of the interesting discussion which followed.  相似文献   
204.
《Thermochimica Acta》2003,401(2):169-173
The heat capacity and the heat content of gallium nitride were measured by calvet calorimetry (320-570 K) and by drop calorimetry (670-1270 K), respectively. The temperature dependence of the heat capacity in the form Cpm=49.552+5.440×10−3T−2.190×106T−2+2.460×108T−3 was derived by the least squares method. Furthermore, thermodynamic functions calculated on the basis of our experimental results and literature data on the molar entropy and the heat of formation of GaN are given.  相似文献   
205.
Fisher linear discriminant analysis is a well-known technique for dimensionality reduction and classification. The method was first formulated in 1936 by Fisher. In this paper we concentrate on three different formulations of the multi-dimensional problem. We provide a mathematical explanation why two of the formulations are equivalent and prove that this equivalency can be extended to a broader class of objective functions. The second contribution is a rate of convergence of a fixed point method for solving the third model.  相似文献   
206.
207.
Let (T, ℐ, μ) be a σ-finite atomless measure space,p∈[1,∞),E a real Banach space andf a measurable function:E xT→ℝ. We denote byF the functionalF: and byDom(F) its domain, it is the set {uεL p(T,E):ū(t)=f(u),tL 1(T)}, and we prove that the sublevelsS(λ)={u:F(u)≤λ} are all connected in the subspaceDom(F) of the Banach spaceL p(T, E).  相似文献   
208.
Letf: n (–, ] be a convex polyhedral function. We show that if any standard active set method for quadratic programming (QP) findsx(t)= arg min x ¦x¦2/2+t f(x) for somet> 0, then its final working set defines a simple equality QP subproblem, whose Lagrange multiplier can be used both for testing ift is large enough forx(t) to coincide with the normal minimizer off, and for increasingt otherwise. The QP subproblem may easily be solved via the matrix factorizations used for findingx(t). This opens up the way for efficient implementations. We also give finite methods for computing the whole trajectory {x(t)} t 0, minimizingf over an ellipsoid, and choosing penalty parameters inL 1QP methods for strictly convex QP.This research was supported by the State Committee for Scientific Research under Grant 8S50502206.  相似文献   
209.
Recently, we introduced a class of generalized hypergeometric functionsI n:(b q)/α:(a p) (x, w) by using a difference operator Δ x,w , where . In this paper an attempt has been made to obtain some bilateral generating relations associated withI n ga (x, w). Each result is followed by its applications to the classical orthogonal polynomials.  相似文献   
210.
In this paper, we introduce a potential reduction method for harmonically convex programming. We show that, if the objective function and them constraint functions are allk-harmonically convex in the feasible set, then the number of iterations needed to find an -optimal solution is bounded by a polynomial inm, k, and log(1/). The method requires either the optimal objective value of the problem or an upper bound of the harmonic constantk as a working parameter. Moreover, we discuss the relation between the harmonic convexity condition used in this paper and some other convexity and smoothness conditions used in the literature.The authors like to thank Dr. Hans Nieuwenhuis for carefully reading this paper and the anonymous referees for the worthy suggestions.  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