全文获取类型
收费全文 | 27335篇 |
免费 | 1439篇 |
国内免费 | 2427篇 |
专业分类
化学 | 4062篇 |
晶体学 | 73篇 |
力学 | 1580篇 |
综合类 | 220篇 |
数学 | 13606篇 |
物理学 | 1395篇 |
综合类 | 10265篇 |
出版年
2024年 | 56篇 |
2023年 | 234篇 |
2022年 | 308篇 |
2021年 | 357篇 |
2020年 | 528篇 |
2019年 | 593篇 |
2018年 | 616篇 |
2017年 | 641篇 |
2016年 | 650篇 |
2015年 | 577篇 |
2014年 | 1115篇 |
2013年 | 1817篇 |
2012年 | 1605篇 |
2011年 | 1467篇 |
2010年 | 1239篇 |
2009年 | 1606篇 |
2008年 | 1757篇 |
2007年 | 1996篇 |
2006年 | 1796篇 |
2005年 | 1448篇 |
2004年 | 1284篇 |
2003年 | 1321篇 |
2002年 | 1113篇 |
2001年 | 866篇 |
2000年 | 885篇 |
1999年 | 753篇 |
1998年 | 707篇 |
1997年 | 614篇 |
1996年 | 527篇 |
1995年 | 442篇 |
1994年 | 347篇 |
1993年 | 309篇 |
1992年 | 330篇 |
1991年 | 288篇 |
1990年 | 224篇 |
1989年 | 155篇 |
1988年 | 137篇 |
1987年 | 108篇 |
1986年 | 72篇 |
1985年 | 68篇 |
1984年 | 60篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
青少年心理问题是社会高度现代化后带来的副产品。日本是亚洲第一个高度现代化的国家,青少年心理问题尤为突出。该文从日本青少年心理问题引发的社会现象入手,剖析其原因,找出解决途径。当前,我国正处于现代化的初级阶段,青少年心理问题层出不穷,有必要学习日本的经验,采取一些防治措施,以达到未雨绸缪之功效。 相似文献
82.
A direct central collision of two identical bodies of revolution is studied. A nonstationary mixed boundary-value problem with an unknown moving boundary is formulated. Its solution is represented by a series in term of Bessel functions. An infinite system of Volterra equations of the second kind for the unknown expansion coefficients is derived by satisfying the boundary conditions. The basic characteristics of the collision process are determined depending on the curvature of the frontal surface of the bodies 相似文献
83.
We consider the problem of determining the dielectric permittivity for a nonconducting and nonmagnetic medium. As information we take the traces of the tangential components of the electromagnetic field on the lateral surface of a cylindrical domain. These traces correspond to a solution to some direct problem for the Maxwell system. The impulse source of the current flux lies outside the domain in which the coefficient is sought. The main result of the article is a stability estimate for a solution to the inverse problem in question. 相似文献
84.
Banach空间二阶周期边值问题解的存在性 总被引:2,自引:0,他引:2
利用一些比较结果,讨论了Banach空间中二阶周期边值问题解的存在性,获得了若干解的存在性与唯一性结果。 相似文献
85.
Xian Xu 《Journal of Mathematical Analysis and Applications》2004,291(2):673-689
In this paper, some multiplicity results for positive solutions of some singular semi-positone three-point boundary value problem be obtained by using the fixed point index method. 相似文献
86.
Zhimin He 《Journal of Mathematical Analysis and Applications》2004,296(1):97-109
In this paper, by means of a new twin fixed-point theorem in a cone, the existence of at least two positive solutions of m-point boundary value problem for second order dynamic equations on time scales is considered. 相似文献
87.
We consider the Maxwell-Cattaneo system of equations for generalized heat conduction where the temperature and heat flux satisfy a nonstandard auxiliary condition which prescribes a combination of their values initially and at a later time. We obtain L2 bounds for the temperature and heat flux by means of Lagrange identities. These bounds extend the range of validity for the parameter in the nonstandard condition under a constraint on the coefficients in the differential equations. 相似文献
88.
Nguyen Minh Chuong Bui Kien Cuong 《Proceedings of the American Mathematical Society》2004,132(12):3589-3597
A class of Cauchy problems for interesting complicated periodic pseudodifferential equations is considered. By the Galerkin-wavelet method and with weak solutions one can find sufficient conditions to establish convergence estimates of weak Galerkin-wavelet solutions to a Cauchy problem for this class of equations.
89.
In this work, the NP-hard maximum clique problem on graphs is considered. Starting from basic greedy heuristics, modifications and improvements are proposed and combined in a two-phase heuristic procedure. In the first phase an improved greedy procedure is applied starting from each node of the graph; on the basis of the results of this phase a reduced subset of nodes is selected and an adaptive greedy algorithm is repeatedly started to build cliques around such nodes. In each restart the selection of nodes is biased by the maximal clique generated in the previous execution. Computational results are reported on the DIMACS benchmarks suite. Remarkably, the two-phase procedure successfully solves the difficult Brockington-Culberson instances, and is generally competitive with state-of-the-art much more complex heuristics. 相似文献
90.