全文获取类型
收费全文 | 152132篇 |
免费 | 14115篇 |
国内免费 | 8452篇 |
专业分类
化学 | 76983篇 |
晶体学 | 1458篇 |
力学 | 11274篇 |
综合类 | 397篇 |
数学 | 40120篇 |
物理学 | 44467篇 |
出版年
2024年 | 183篇 |
2023年 | 1665篇 |
2022年 | 2021篇 |
2021年 | 2795篇 |
2020年 | 3375篇 |
2019年 | 3177篇 |
2018年 | 12434篇 |
2017年 | 12096篇 |
2016年 | 9456篇 |
2015年 | 4482篇 |
2014年 | 4662篇 |
2013年 | 5989篇 |
2012年 | 10838篇 |
2011年 | 17375篇 |
2010年 | 10351篇 |
2009年 | 10376篇 |
2008年 | 11344篇 |
2007年 | 12973篇 |
2006年 | 4320篇 |
2005年 | 4667篇 |
2004年 | 4085篇 |
2003年 | 4010篇 |
2002年 | 2958篇 |
2001年 | 1936篇 |
2000年 | 1765篇 |
1999年 | 1840篇 |
1998年 | 1594篇 |
1997年 | 1499篇 |
1996年 | 1549篇 |
1995年 | 1211篇 |
1994年 | 1041篇 |
1993年 | 898篇 |
1992年 | 762篇 |
1991年 | 677篇 |
1990年 | 582篇 |
1989年 | 473篇 |
1988年 | 412篇 |
1987年 | 348篇 |
1986年 | 316篇 |
1985年 | 258篇 |
1984年 | 191篇 |
1983年 | 145篇 |
1982年 | 123篇 |
1981年 | 107篇 |
1980年 | 112篇 |
1979年 | 77篇 |
1978年 | 64篇 |
1977年 | 58篇 |
1976年 | 46篇 |
1973年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 299 毫秒
981.
Michael J. Puls 《Archiv der Mathematik》2007,88(6):500-506
Let p be a real number greater than one. In this paper we study the vanishing and nonvanishing of the first L
p
-cohomology space of some groups that have one end. We also make a connection between the first L
p
-cohomolgy space and the Floyd boundary of the Cayley graph of a group. We apply the result about Floyd boundaries to show
that there exists a real number p such that the first L
p
-cohomology space of a nonelementary hyperbolic group does not vanish.
Received: 4 August 2006 Revised: 2 November 2006 相似文献
982.
This paper is concerned with the spectral analysis of a one-velocity transport operator with Maxwell boundary condition in
L
1-space. After a detailed spectral analysis it is shown that the associated Cauchy problem is governed by a C
0-semigroup. Next, we discuss the irreducibility of the transport semigroup. In particular, we show that the transport semigroup
is irreducible. Finally, a spectral decomposition of the solutions into an asymptotic term and a transient one which will
be estimated for smooth initial data is given. 相似文献
983.
984.
985.
We give some sufficient conditions for proper lower semicontinuous functions on metric spaces to have error bounds (with exponents).
For a proper convex function f on a normed space X the existence of a local error bound implies that of a global error bound. If in addition X is a Banach space, then error bounds can be characterized by the subdifferential of f. In a reflexive Banach space X, we further obtain several sufficient and necessary conditions for the existence of error bounds in terms of the lower Dini
derivative of f.
Received: April 27, 2001 / Accepted: November 6, 2001?Published online April 12, 2002 相似文献
986.
Shengqiang Liu Lansun ChenYoulin Jiang 《Journal of Mathematical Analysis and Applications》2002,271(1):124-138
In this paper, a two-species competitive model with stage structure is presented and studied. Results on the global extinction and permanence are given, which generalize the well-known three theorems for the two species competitive system and, moreover, they confirm the negative effect of stage structure on the permanence of populations as well as estimate the degree of such effect. Conclusions in this paper suggest that for a competitive community stage structure is also one of the important reasons that cause permanence and extinction. 相似文献
987.
In a recent paper [17] we proposed a stochastic algorithm which generates optimal probabilities for the decompression of
an image represented by the fixed point of an IFS system (SAOP). We show here that such an algorithm is in fact a non trivial
example of Generalized Random System with Complete Connections. We also exhibit a generalization which could represent the
solution to the inverse problem for an image with grey levels, if a fixed set of contraction maps is available.
Received: 1 July 2002 相似文献
988.
一类随机环境中的随机游动 总被引:5,自引:2,他引:3
在Solomn的模型的基础上对一类随机环境中随机游动进行了讨论,并得出了一个常返性准则和一些极限性质。 相似文献
989.
990.
甲基红染料掺杂的聚乙烯醇薄膜光存储特性的实验研究 总被引:1,自引:0,他引:1
用2倍频小型YAG激光(532nm)作为写入光和擦除光,用He-Ne激光器623.8nm线作为读出光,用CCD作为探测器,研究了不同写入光功率下,甲基红/聚乙烯醇(MR/PVA)薄膜光栅生长的动力学过程和不同擦除光功率下,光栅擦除的动力学过程.结合光栅生长曲线的波动现象,对光存储机制进行了新的探讨.实验发现,两写入光和读出光的功率配比为1:1:1时,可获得最大衍射效率,提出读出光对写入过程具有双重作用的物理模型,对此实验结果给出了合理的解释. 相似文献