全文获取类型
收费全文 | 2426篇 |
免费 | 137篇 |
国内免费 | 204篇 |
专业分类
化学 | 470篇 |
晶体学 | 2篇 |
力学 | 159篇 |
综合类 | 7篇 |
数学 | 1718篇 |
物理学 | 411篇 |
出版年
2024年 | 4篇 |
2023年 | 37篇 |
2022年 | 49篇 |
2021年 | 49篇 |
2020年 | 36篇 |
2019年 | 68篇 |
2018年 | 38篇 |
2017年 | 42篇 |
2016年 | 64篇 |
2015年 | 40篇 |
2014年 | 106篇 |
2013年 | 237篇 |
2012年 | 112篇 |
2011年 | 170篇 |
2010年 | 131篇 |
2009年 | 207篇 |
2008年 | 172篇 |
2007年 | 203篇 |
2006年 | 178篇 |
2005年 | 123篇 |
2004年 | 128篇 |
2003年 | 106篇 |
2002年 | 66篇 |
2001年 | 63篇 |
2000年 | 60篇 |
1999年 | 44篇 |
1998年 | 48篇 |
1997年 | 40篇 |
1996年 | 42篇 |
1995年 | 16篇 |
1994年 | 24篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有2767条查询结果,搜索用时 0 毫秒
121.
We introduce the concept of Toeplitz-Kre?n-Cotlar triplet on ordered groups and we prove a general dilation result and a general representation result for the positive definite case.This general result includes and extends previous generalizations of the Kre?n extension theorem, the Sz.-Nagy and Foias commutant lifting theorem and the generalized Herglotz-Bochner-Weil theorem. 相似文献
122.
This paper presents sufficient conditions for the existence and multiplicity of positive solutions to the one-dimensional p-Laplacian differential equation (?p′(u′))+a(t)f(u,u′)=0, subject to some boundary conditions. We show that it has at least one or two or three positive solutions under some assumptions by applying the fixed point theorem. 相似文献
123.
Cornel Pasnicu 《Journal of Mathematical Analysis and Applications》2006,323(2):1213-1224
Let A be the C∗-algebra associated to an arbitrary continuous field of C∗-algebras. We give a necessary and sufficient condition for A to have the ideal property and, if moreover A is separable, we give a necessary and sufficient condition for A to have the projection property. Some applications of these results are given. We also prove that “many” crossed products of commutative C∗-algebras by discrete, amenable groups have the projection property, generalizing some of our previous results. 相似文献
124.
This paper proposes two optimization models for the periodic inspection of a system with “hard-type” and “soft-type” components. Given that the failures of hard-type components are self-announcing, the component is instantly repaired or replaced, but the failures of soft-type components can only be detected at inspections. A system can operate with a soft failure, but its performance may be reduced. Although a system may be periodically inspected, a hard failure creates an opportunity for additional inspection (opportunistic inspection) of all soft-type components. Two optimization models are discussed in the paper. In the first, soft-type components undergo both periodic and opportunistic inspections to detect possible failures. In the second, hard-type components undergo periodic inspections and are preventively replaced depending on their condition at inspection. Soft-type and hard-type components are either minimally repaired or replaced when they fail. Minimal repair or replacement depends on the state of a component at failure; this, in turn, depends on its age. The paper formulates objective functions for the two models and derives recursive equations for their required expected values. It develops a simulation algorithm to calculate these expected values for a complex model. Several examples are used to illustrate the models and the calculations. The data used in the examples are adapted from a real case study of a hospital’s maintenance data for a general infusion pump. 相似文献
125.
In this paper we study a particular class of positive projections defined on an adapted subalgebra of continuous real-valued
functions. Among other things, we characterize the existence of such projections in terms of representing measures concentrated
on the Choquet boundary and we show their strong connection with the abstract Dirichlet problem. Finally we show how to construct
Korovkin subsets for such projections.
Mathematics Subject classification (2000): Primary:47B38, 47B65, 31C99. Secondary 46E25, 41A36. 相似文献
126.
本文研究具有p-Laplacian算子的奇异多点边值问题{(Фp(u'))'+q(t)f(t,u)=0,0〈t〈1;u(0)=∑n i=1 αiu(ηi),u(i)∑n i=1 βiu(ηi)正解的存在性,其中f(t,u)可以在u=0奇异,q(t)可以在t=0或t=1奇异. 相似文献
127.
Zhengqiu Zhang 《Journal of Mathematical Analysis and Applications》2005,302(2):291-305
By using the continuation theorem of coincidence degree theory, the existence of a positive periodic solution for the predator-prey system with stage-structures for predator and prey is established. 相似文献
128.
By using fixed point theorem, we study the following equation g(u′′(t))+a(t)f(u)=0 subject to boundary conditions, where g(v)=|v|p−2v with p>1; the existence of at least three positive solutions is proved. 相似文献
129.
Pairwise linear discriminant analysis can be regarded as a process to generate rankings of the populations. But in general, not all rankings are generated. We give a characterization of generated rankings. We also derive some basic properties of this model. 相似文献
130.
Existence, Multiplicity and Infinite Solvability of Positive Solutions for One-Dimensional p-Laplacian 总被引:5,自引:0,他引:5
Qing Liu YAO 《数学学报(英文版)》2005,21(4):691-698
The existence, multiplicity and infinite solvability of positive solutions are established for some two-point boundary value problems of one-dimensional p-Laplacian. In this paper, by multiplicity we mean the existence of m solutions, where m is an arbitrary natural number. 相似文献