全文获取类型
收费全文 | 7571篇 |
免费 | 700篇 |
国内免费 | 602篇 |
专业分类
化学 | 504篇 |
晶体学 | 6篇 |
力学 | 509篇 |
综合类 | 118篇 |
数学 | 5627篇 |
物理学 | 2109篇 |
出版年
2024年 | 8篇 |
2023年 | 63篇 |
2022年 | 91篇 |
2021年 | 90篇 |
2020年 | 153篇 |
2019年 | 168篇 |
2018年 | 155篇 |
2017年 | 182篇 |
2016年 | 207篇 |
2015年 | 166篇 |
2014年 | 305篇 |
2013年 | 643篇 |
2012年 | 349篇 |
2011年 | 418篇 |
2010年 | 353篇 |
2009年 | 470篇 |
2008年 | 507篇 |
2007年 | 497篇 |
2006年 | 502篇 |
2005年 | 389篇 |
2004年 | 348篇 |
2003年 | 343篇 |
2002年 | 327篇 |
2001年 | 264篇 |
2000年 | 254篇 |
1999年 | 254篇 |
1998年 | 209篇 |
1997年 | 155篇 |
1996年 | 151篇 |
1995年 | 90篇 |
1994年 | 98篇 |
1993年 | 76篇 |
1992年 | 59篇 |
1991年 | 49篇 |
1990年 | 54篇 |
1989年 | 36篇 |
1988年 | 48篇 |
1987年 | 30篇 |
1986年 | 26篇 |
1985年 | 47篇 |
1984年 | 42篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 23篇 |
1980年 | 20篇 |
1979年 | 24篇 |
1978年 | 13篇 |
1977年 | 17篇 |
1976年 | 11篇 |
1974年 | 9篇 |
排序方式: 共有8873条查询结果,搜索用时 15 毫秒
1.
2.
Rong Yin Jihui Zhang Xudong Shang 《Mathematical Methods in the Applied Sciences》2020,43(15):8736-8752
This paper is dedicated to studying the following Schrödinger–Poisson system Under some different assumptions on functions V(x), K(x), a(x) and f(u), by using the variational approach, we establish the existence of positive ground state solutions. 相似文献
3.
4.
5.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
6.
We employ a first-principles plane wave method with the
relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter
(HGH) scheme in the frame of DFT to calculate
the equilibrium lattice parameters and the thermodynamic properties of
AlB2 compound with hcp structure. The obtained lattice parameters are in
good agreement with the available experimental data and those calculated by
others. Through the quasi-harmonic Debye model, obtained successfully are
the dependences of the
normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized
primitive cell volume V/V0 on pressure P, the variation of the thermal
expansion α with pressure P and temperature T, as well as the Debye
temperature \ThetaD and the heat capacity CV on pressure P and
temperature T. 相似文献
7.
Zhong-Qing Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):374-403
An orthogonal system of rational functions is discussed. Some inverse inequalities, imbedding inequalities and approximation results are obtained. Two model problems are considered. The stabilities and convergences of proposed rational spectral schemes and rational pseudospectral schemes are proved. The techniques used in this paper are also applicable to other problems on the whole line. Numerical results show the efficiency of this approach. 相似文献
8.
Formalization for problems of multicriteria decision making under uncertainty is constructed in terms of guaranteed and weak
estimates. A relevant definition of the vector maximinimax value is given. Parameterization and approximation of maximum,
minimax, and maximinimax values based on the inverse logical convolution are suggested. An application for multicommodity
networks is considered.
Received: December 13, 2000 / Accepted: August 21, 2001?Published online May 8, 2002 相似文献
9.
10.
This paper is concerned with the implementation and testing of an algorithm for solving constrained least-squares problems. The algorithm is an adaptation to the least-squares case of sequential quadratic programming (SQP) trust-region methods for solving general constrained optimization problems. At each iteration, our local quadratic subproblem includes the use of the Gauss–Newton approximation but also encompasses a structured secant approximation along with tests of when to use this approximation. This method has been tested on a selection of standard problems. The results indicate that, for least-squares problems, the approach taken here is a viable alternative to standard general optimization methods such as the Byrd–Omojokun trust-region method and the Powell damped BFGS line search method. 相似文献