全文获取类型
收费全文 | 14953篇 |
免费 | 2041篇 |
国内免费 | 2468篇 |
专业分类
化学 | 2678篇 |
晶体学 | 137篇 |
力学 | 699篇 |
综合类 | 788篇 |
数学 | 12051篇 |
物理学 | 3109篇 |
出版年
2024年 | 55篇 |
2023年 | 305篇 |
2022年 | 281篇 |
2021年 | 288篇 |
2020年 | 290篇 |
2019年 | 356篇 |
2018年 | 195篇 |
2017年 | 396篇 |
2016年 | 420篇 |
2015年 | 538篇 |
2014年 | 890篇 |
2013年 | 626篇 |
2012年 | 823篇 |
2011年 | 790篇 |
2010年 | 784篇 |
2009年 | 821篇 |
2008年 | 1076篇 |
2007年 | 933篇 |
2006年 | 934篇 |
2005年 | 992篇 |
2004年 | 817篇 |
2003年 | 839篇 |
2002年 | 683篇 |
2001年 | 700篇 |
2000年 | 630篇 |
1999年 | 502篇 |
1998年 | 481篇 |
1997年 | 444篇 |
1996年 | 435篇 |
1995年 | 445篇 |
1994年 | 324篇 |
1993年 | 252篇 |
1992年 | 295篇 |
1991年 | 266篇 |
1990年 | 222篇 |
1989年 | 172篇 |
1988年 | 45篇 |
1987年 | 35篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1959年 | 9篇 |
1936年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
61.
62.
ZHANG Yongqian 《数学年刊B辑(英文版)》2005,26(3):379-392
This paper studies the asymptotic behaviour of steady supersonic flow past a piece-wise smooth corner or bend. Under the hypothese that both vertex angle and the total variation of tangent along the boundary are small, it is shown that the solution can be obtained by a modified Glimm scheme, and that the asymptotic behaviour of the solution is determined by the velocity of incoming flow and the limit of the tangent of the boundary at infinity. 相似文献
63.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
64.
65.
66.
We propose a novel coupled quantum well structure, i.e. a quasi-symmetric coupled quantum well (QSCQW). Based on the demands of optical switching devices for quantum well materials, the QSCQW configuration is further optimized. Consequently, in the case of low applied electric field 25kV/cm and low absorption loss 100cm^-1, a large field-induced refractive index change (for TE mode, n = 0.0106; for TM mode, n = 0.0115) is obtained in the QSCQW structure at the operation wavelength 1550hm. The value is in one or two order of magnitude larger than that in a rectangular quantum well and about 50% larger than that of five-step asymmetric coupled quantum well structure under the same working conditions. The refractive index change obtained with the optimized QSCQW under so low absorption loss and applied electric field is very attractive for semiconductor optical switching devices. This manifests that the QSCQW structure has a great potential for applications in ultra-fast and low-voltage optical switches and in travelling wave modulators. 相似文献
67.
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
68.
We present a compact improved model of the magnetically insulated line oscillator with new-type beam dump and other novel features. In the experiments, high-power microwave of the TM01 mode is generated from the device with a frequency range of 1.73-1.78 GHz and a peak power level of above 2 GW, when the diode voltage is taken in the range 520-540kV, and the diode current is in the range 58-62kA. This confirms the simulation results. 相似文献
69.
On Best Approximations from RS-sets in Complex Banach Spaces 总被引:2,自引:0,他引:2
ChongLI 《数学学报(英文版)》2005,21(1):31-38
The concept of an RS-set in a complex Banach space is introduced and the problem of best approximation from an RS-set in a complex space is investigated. Results consisting of characterizations, uniqueness and strong uniqueness are established, 相似文献
70.
具P-Laplacian算子型周期边值问题解的存在性 总被引:8,自引:0,他引:8
本文利用拓扑度理论和一些分析技巧讨论了具p—Laplacian算子型周期边值问题(φp(χ’))’+d/dt gradF(χ)+gradG(χ)=e(t),χ(0)=χ(T),χ’(0)=χ’(T)解的存在性,在对阻尼项d/dtgradF(χ)没有任何限制的前提下,给出了解存在的充分条件. 相似文献