全文获取类型
收费全文 | 14172篇 |
免费 | 892篇 |
国内免费 | 1414篇 |
专业分类
化学 | 923篇 |
晶体学 | 12篇 |
力学 | 634篇 |
综合类 | 168篇 |
数学 | 6541篇 |
物理学 | 1138篇 |
综合类 | 7062篇 |
出版年
2024年 | 23篇 |
2023年 | 139篇 |
2022年 | 184篇 |
2021年 | 191篇 |
2020年 | 219篇 |
2019年 | 269篇 |
2018年 | 264篇 |
2017年 | 305篇 |
2016年 | 304篇 |
2015年 | 338篇 |
2014年 | 618篇 |
2013年 | 711篇 |
2012年 | 689篇 |
2011年 | 779篇 |
2010年 | 666篇 |
2009年 | 855篇 |
2008年 | 819篇 |
2007年 | 988篇 |
2006年 | 955篇 |
2005年 | 814篇 |
2004年 | 715篇 |
2003年 | 745篇 |
2002年 | 646篇 |
2001年 | 574篇 |
2000年 | 498篇 |
1999年 | 472篇 |
1998年 | 408篇 |
1997年 | 394篇 |
1996年 | 323篇 |
1995年 | 220篇 |
1994年 | 242篇 |
1993年 | 182篇 |
1992年 | 158篇 |
1991年 | 144篇 |
1990年 | 118篇 |
1989年 | 106篇 |
1988年 | 94篇 |
1987年 | 57篇 |
1986年 | 39篇 |
1985年 | 40篇 |
1984年 | 31篇 |
1983年 | 20篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 24篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1974年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
软件补偿方法具有效果好、精确度高、成本低的优点。介绍了在研制多点巡回检测仪中采用的几种软件补偿方法:前向通道特性补偿使放大器等元件不因外界条件的变化而受到任何影响;引线电阻的补偿可实现引线电阻对系统无任何影响;热电阻、热电偶的非线性度补偿效果明显,节省开销。 相似文献
62.
钟怀杰 《福建师范大学学报(自然科学版)》1993,9(3):10-14
讨论一般巴拿赫空间上非紧的黎斯算子存在问题,说明各经典巴拿赫空间上确有这种非平凡的黎斯算子,给出一类空间,其上的根算子理想与严格奇异算子理想是不重合的。 相似文献
63.
Browder-Petryshyn 型的严格伪压缩映射的粘滞迭代逼近方法 总被引:1,自引:0,他引:1
主要研究Browder-Petryshyn型的严格伪压缩映射的粘滞迭代逼近过程,证明了Browder-Petryshyn型的严格伪压缩映射的不动点集F(T)是闭凸集.在q-一致光滑且一致凸的Banach空间中,对于严格伪压缩映射T,利用徐洪坤在2004年引进的粘滞迭代得到的序列弱收敛于T的某个不动点.同时证明了Hilbert空间中Browder-Petryshyn型的严格伪压缩映射的相应迭代序列强收敛到T的某个不动点,其结果推广与改进了徐洪坤2004年的相应结果. 相似文献
64.
The estimation-valued property of B-valued asymptotic martingale 总被引:2,自引:0,他引:2
KONG Fanliang 《自然科学进展(英文版)》2006,16(7):773-776
In this paper, with the Doob decomposition of B-valued asymptotic martingale, we study the estimation-valued property of B-valued asymptotic martingale in Banach space B,which has the Radon-Nikodym Property and is dual-separable, and give a series of result and proof. 相似文献
65.
Alex Hellsten 《Archive for Mathematical Logic》2006,45(6):705-714
We extract some properties of Mahlo’s operation and show that some other very natural operations share these properties. The weakly compact sets form a similar hierarchy as the stationary sets. The height of this hierarchy is a large cardinal property connected to saturation properties of the weakly compact ideal. 相似文献
66.
Dmitry I. Belov Ronald D. Armstrong 《Computational Optimization and Applications》2006,33(2-3):319-332
This paper introduces a novel approach for extracting the maximum number of non-overlapping test forms from a large collection
of overlapping test sections assembled from a given item bank. The approach involves solving maximum set packing problems
(MSPs). A branch-and-bound MSP algorithm is developed along with techniques adapted from constraint programming to estimate
lower and upper bounds on the optimal MSP solution. The algorithm is general and can be applied in other applications including
combinatorial auctions. The results of computer simulations and experiments with an operational item bank are presented.
An erratum to this article is available at . 相似文献
67.
D. V. Artamonov 《Mathematical Notes》2007,81(5-6):573-589
A natural criterion for dimensional full-valuedness of locally compact spaces with finitely generated local homology is given. 相似文献
68.
Brian Lucena 《Discrete Applied Mathematics》2007,155(8):1055-1065
One consequence of the graph minor theorem is that for every k there exists a finite obstruction set Obs(TW?k). However, relatively little is known about these sets, and very few general obstructions are known. The ones that are known are the cliques, and graphs which are formed by removing a few edges from a clique. This paper gives several general constructions of minimal forbidden minors which are sparse in the sense that the ratio of the treewidth to the number of vertices n does not approach 1 as n approaches infinity. We accomplish this by a novel combination of using brambles to provide lower bounds and achievable sets to demonstrate upper bounds. Additionally, we determine the exact treewidth of other basic graph constructions which are not minimal forbidden minors. 相似文献
69.
Many recent algorithmic approaches involve the construction of a differential equation model for computational purposes, typically
by introducing an artificial time variable. The actual computational model involves a discretization of the now time-dependent differential system, usually
employing forward Euler. The resulting dynamics of such an algorithm is then a discrete dynamics, and it is expected to be
“close enough” to the dynamics of the continuous system (which is typically easier to analyze) provided that small – hence
many – time steps, or iterations, are taken. Indeed, recent papers in inverse problems and image processing routinely report
results requiring thousands of iterations to converge. This makes one wonder if and how the computational modeling process
can be improved to better reflect the actual properties sought.
In this article we elaborate on several problem instances that illustrate the above observations. Algorithms may often lend
themselves to a dual interpretation, in terms of a simply discretized differential equation with artificial time and in terms
of a simple optimization algorithm; such a dual interpretation can be advantageous. We show how a broader computational modeling
approach may possibly lead to algorithms with improved efficiency.
AMS subject classification (2000) 65L05, 65M32, 65N21, 65N22, 65D18 相似文献
70.
对覆盖广义Rough集中的隶属关系、隶属函数进行了定义,并利用隶属函数定义了集合的Rough包含与Rough相等,得到一些与Pawlak的Rough集不同的性质。 相似文献