全文获取类型
收费全文 | 15723篇 |
免费 | 2578篇 |
国内免费 | 1697篇 |
专业分类
化学 | 11601篇 |
晶体学 | 194篇 |
力学 | 846篇 |
综合类 | 72篇 |
数学 | 1543篇 |
物理学 | 5742篇 |
出版年
2024年 | 60篇 |
2023年 | 319篇 |
2022年 | 560篇 |
2021年 | 560篇 |
2020年 | 635篇 |
2019年 | 639篇 |
2018年 | 579篇 |
2017年 | 507篇 |
2016年 | 736篇 |
2015年 | 777篇 |
2014年 | 979篇 |
2013年 | 1208篇 |
2012年 | 1401篇 |
2011年 | 1478篇 |
2010年 | 1060篇 |
2009年 | 906篇 |
2008年 | 1047篇 |
2007年 | 953篇 |
2006年 | 839篇 |
2005年 | 727篇 |
2004年 | 544篇 |
2003年 | 458篇 |
2002年 | 426篇 |
2001年 | 305篇 |
2000年 | 305篇 |
1999年 | 252篇 |
1998年 | 224篇 |
1997年 | 197篇 |
1996年 | 183篇 |
1995年 | 144篇 |
1994年 | 185篇 |
1993年 | 129篇 |
1992年 | 125篇 |
1991年 | 96篇 |
1990年 | 90篇 |
1989年 | 85篇 |
1988年 | 45篇 |
1987年 | 31篇 |
1986年 | 34篇 |
1985年 | 29篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
It is well known that the mathematical models provide very important information for the research of human immunodeficiency virus-type 1 and hepatitis C virus (HCV). However, the infection rate of almost all mathematical models is linear. The linearity shows the simple interaction between the T cells and the viral particles. In this paper, we consider the classical mathematical model with saturation response of the infection rate. By stability analysis we obtain sufficient conditions on the parameters for the global stability of the infected steady state and the infection-free steady state. We also obtain the conditions for the existence of an orbitally asymptotically stable periodic solution. Numerical simulations are presented to illustrate the results. 相似文献
72.
湿度对绝缘体表面电导和气体电导有一定的影响,但通常在湿度传感器的研究中忽略了气体电导的贡献。本文通过特殊设计装置来区分表面电导和气体电导,并分别从实验和理论上进行了定性的研究。 相似文献
73.
HypersurfacewithConstantMainCurvatureSymmetricFunctions¥WuBaoqiang;SongHongzao(XuzhouTeachersCollege,221009)(HenanUniversity,... 相似文献
74.
讨论了横向位移双曝光散斑图维纳谱的信息分布,并由此导出杨氏纹图的一般表达式。讨论了条纹可见度与应变,面内转动,照明光束直径与条纹图图空间坐标的关系,指出了在条纹可见度影响下最大可见条纹数目。还讨论了散斑衬比与衍射晕的关系。 相似文献
75.
Haishan Bu Yanwan Pang Dandan Song Tongyin Yu T. M. Voll George Czornyj B. Wunderlich 《Journal of Polymer Science.Polymer Physics》1991,29(2):139-152
Various approaches to the preparation and verification of single-molecule single crystals are discussed for polyethylene and poly (oxyethylene). Analytic tools are electron microscopy, electron diffraction, and differential scanning calorimetry. The main difficulty in producing a single-molecule single crystal is to keep crystals from joining during growth. 相似文献
76.
Xiaodong Xu Pingxin Song Guoqing Zhou Jun Xu Peizhen Deng 《Solid State Communications》2004,129(11):717-720
Cr4+:YbAG (Cr4+:Yb3Al5O12) crystal with a size up to Φ24 mm×30 mm was grown by the Czochralski method. In the absorption spectrum, there are two absorption bands at 939 and 969 nm, respectively, which are suitable for InGaAs diode laser pumping, and there is an absorption band at 1030 nm, which is suitable for passive Q-switched laser output at 1.03 μm. A broad emission spectrum from 970 to 1100 nm was exhibited from 940 nm wavelength pumping. This crystal is promising as a self-Q-switched laser crystal used for compact, efficient, highly stable, passive self-Q-switched thin chip solid-state lasers. 相似文献
77.
We demonstrated a unified two-band broadband light source based on erbium-doped fiber. The proposed scheme generates high output power at both bands and saves doped-fiber and pump lasers. 相似文献
78.
This paper deals with a model of time-dependent double diffusive convection in Darcy flow. In particular it is concerned with the spatial decay of solutions when the flow is confined to a semi-infinite cylinder. Decay bounds for an energy expression are derived. 相似文献
79.
We prove some basic properties of Donaldson’s flow of surfaces in a hyperkähler 4-manifold. When the initial submanifold is symplectic with respect to one Kähler form and Lagrangian with respect to another, we show that certain kinds of singularities cannot form, and we prove a convergence result under a condition related to one considered by M.-T. Wang for the mean curvature flow. 相似文献
80.
Approximation of signals from local averages 总被引:4,自引:0,他引:4
This work is concerned with approximation of a signal from local averages. It improves a result of Butzer and Lei [P.L. Butzer, J. Lei, Approximation of signals using measured sampled values and error analysis, Commun. Appl. Anal. 4 (2000) 245–255]. 相似文献