全文获取类型
收费全文 | 9004篇 |
免费 | 749篇 |
国内免费 | 485篇 |
专业分类
化学 | 1250篇 |
晶体学 | 145篇 |
力学 | 699篇 |
综合类 | 72篇 |
数学 | 6535篇 |
物理学 | 1537篇 |
出版年
2024年 | 20篇 |
2023年 | 73篇 |
2022年 | 102篇 |
2021年 | 115篇 |
2020年 | 235篇 |
2019年 | 236篇 |
2018年 | 241篇 |
2017年 | 251篇 |
2016年 | 261篇 |
2015年 | 214篇 |
2014年 | 382篇 |
2013年 | 853篇 |
2012年 | 325篇 |
2011年 | 499篇 |
2010年 | 501篇 |
2009年 | 569篇 |
2008年 | 631篇 |
2007年 | 569篇 |
2006年 | 497篇 |
2005年 | 452篇 |
2004年 | 390篇 |
2003年 | 354篇 |
2002年 | 321篇 |
2001年 | 252篇 |
2000年 | 209篇 |
1999年 | 210篇 |
1998年 | 161篇 |
1997年 | 162篇 |
1996年 | 142篇 |
1995年 | 109篇 |
1994年 | 98篇 |
1993年 | 78篇 |
1992年 | 66篇 |
1991年 | 53篇 |
1990年 | 48篇 |
1989年 | 33篇 |
1988年 | 41篇 |
1987年 | 24篇 |
1986年 | 43篇 |
1985年 | 45篇 |
1984年 | 54篇 |
1983年 | 40篇 |
1982年 | 50篇 |
1981年 | 41篇 |
1980年 | 38篇 |
1979年 | 45篇 |
1978年 | 30篇 |
1977年 | 17篇 |
1976年 | 20篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
关于非线性多目标规划问题非劣解解法的探讨 总被引:3,自引:0,他引:3
非线性多目标规划是一类复杂的规划问题,由于其往往没有最优解,因此求其非劣解具有重要的意义。本首先探讨了无约束条件下非线性多目标规划的解法,然后提出了有约束条件下非线性多目标规划的一种解法。所述方法具有一定的普遍意义。 相似文献
132.
In this paper we obtain some sufficient conditions for the existence of non-constant periodic solutions of the following planar system with six delaysOur approach is based on the continuation theorem of the coincidence degree. 相似文献
133.
This paper deals with the analysis of an M/M/c queueing system with setup times. This queueing model captures the major characteristics of phenomena occurring in production
when the system consists in a set of machines monitored by a single operator. We carry out an extensive analysis of the system
including limiting distribution of the system state, waiting time analysis, busy period and maximum queue length.
AMS subject classification: 90B22, 60K25 相似文献
134.
Yoshiyuki Hino 《Journal of Mathematical Analysis and Applications》2003,286(2):741-752
For abstract linear functional differential equations with an almost automorphic forcing term, we establish a result on the existence of almost automorphic solutions, which extends the classical theorem due to Massera on the existence of periodic solutions for linear periodic ordinary differential equations. 相似文献
135.
Vipul Dav Wolfgang G. Glasser Garth L. Wilkes 《Journal of Polymer Science.Polymer Physics》1993,31(9):1145-1161
Fibers were spun from isotropic and anisotropic dimethylacetamide solutions of cellulose esters. Take-up speeds of the dry jet/wet spinning process varied. Water served as the coagulant. The mechanical properties of the fibers increased as spinning progressed from the isotropic to the anisotropic state of the solution. A trade-off in solubility and fiber properties was noted as the butyryl acetyl ratio decreased. Whereas high butyryl content enhances both overall solubility and the formation of liquid–crystalline solutions at lower concentration, it results in lower fiber modulus and strength. Morphology of the fibers depended on the coagulation rate which was influenced by the concentration of the sppinning solution. The level of orientation and crystallinity of the fibers increased somewhat when they were spun from liquid-crystalline solutions. © 1993 John Wiley & Sons, Inc. 相似文献
136.
一类非线性算子方程的多重正解及其应用 总被引:18,自引:5,他引:13
本文利用不动点指数理论对一类非线性算子方程建立了多重正解的存在性定理,并将所获结果应用到Hammerstein积分方程和Sturm Liouvile两点边值问题,得到了新的结论,本质上改进和推广了[2,4,5,6,8-12]的工作. 相似文献
137.
1IntroductionThemethodofupperandlowersolutionshasbecomeastandardtoolforstudyingthesolvabilityoftwo-pointboundaryvalllcproblemsassociatedwitllsecond-ordernonlineardifferentialequations.Inrecent,years,Rachunkovd[1,2,3]studiedthefour--pointboundaryvalueprobl… 相似文献
138.
The constrained optimization problem with a quadratic cost functional and two quadratic equality constraints has been studied by Bar-on and Grasse, with positive-definite matrix in the objective. In this note, we shall relax the matrix in the objective to be positive semidefinite. A necessary and sufficient condition to characterize a local optimal solution to be global is established. Also, a perturbation scheme is proposed to solve this generalized problem. 相似文献
139.
140.
The solvability of a class of forward-backward stochastic differential equations (SDEs for short) over an arbitrarily prescribed time duration is studied. The authors design a stochastic relaxed control problem, with both drift and difftusion all being controlled, so that the solvability problem is converted to a problem of finding the nodal set of the viscosity solution to a certain Hamilton-Jacobi-Bellman equation. This method overcomes the fatal difficulty encountered in the traditional contraction mapping approach to the existence theorem of such SDEs. 相似文献