全文获取类型
收费全文 | 34088篇 |
免费 | 3623篇 |
国内免费 | 3741篇 |
专业分类
化学 | 25860篇 |
晶体学 | 440篇 |
力学 | 1756篇 |
综合类 | 238篇 |
数学 | 4361篇 |
物理学 | 8797篇 |
出版年
2024年 | 51篇 |
2023年 | 351篇 |
2022年 | 1039篇 |
2021年 | 1238篇 |
2020年 | 1208篇 |
2019年 | 1106篇 |
2018年 | 989篇 |
2017年 | 1193篇 |
2016年 | 1337篇 |
2015年 | 1198篇 |
2014年 | 1535篇 |
2013年 | 2331篇 |
2012年 | 1843篇 |
2011年 | 2115篇 |
2010年 | 1760篇 |
2009年 | 2197篇 |
2008年 | 2035篇 |
2007年 | 2020篇 |
2006年 | 1834篇 |
2005年 | 1698篇 |
2004年 | 1704篇 |
2003年 | 1347篇 |
2002年 | 1625篇 |
2001年 | 973篇 |
2000年 | 789篇 |
1999年 | 655篇 |
1998年 | 565篇 |
1997年 | 521篇 |
1996年 | 539篇 |
1995年 | 496篇 |
1994年 | 482篇 |
1993年 | 335篇 |
1992年 | 349篇 |
1991年 | 212篇 |
1990年 | 166篇 |
1989年 | 171篇 |
1988年 | 183篇 |
1987年 | 139篇 |
1986年 | 102篇 |
1985年 | 94篇 |
1984年 | 90篇 |
1983年 | 31篇 |
1982年 | 88篇 |
1981年 | 110篇 |
1980年 | 123篇 |
1979年 | 125篇 |
1978年 | 98篇 |
1977年 | 74篇 |
1976年 | 67篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 92 毫秒
61.
62.
采用甚高频等离子体增强化学气相沉积技术制备了系列微晶硅薄膜太阳电池,指出了气体总流量和背反射电极的类型对电池性能参数的影响.电池的I-V测试结果表明:随反应气体总流量的增加,对应电池的短路电流密度、开路电压和填充因子都有很大程度的提高,结果使得电池的光电转换效率得以提高.另外,ZnO/Ag/Al背反射电极能明显提高电池的短路电流密度,进而也提高了电池的光电转换效率.对气体总流量和背反射电极类型影响电池效率的原因进行了分析.
关键词:
微晶硅薄膜太阳电池
气体流量
ZnO/Ag/Al背反射电极 相似文献
63.
基于校园网的实验管理系统的设计 总被引:2,自引:1,他引:1
主要讨论了应用实验室管理系统的必要性,并从用户需求分析、系统总体设计、功能模块的设计等方面对B/S实验室管理系统的开发进行了详细的阐述。 相似文献
64.
Piotr Garbaczewski 《Journal of statistical physics》2006,123(2):315-355
We analyze the functioning of Gibbs-type entropy functionals in the time domain, with emphasis on Shannon and Kullback-Leibler entropies of time-dependent continuous probability distributions. The Shannon entropy validity is extended to probability distributions inferred from L
2(R
n
) quantum wave packets. In contrast to the von Neumann entropy which simply vanishes on pure states, the differential entropy quantifies the degree of probability (de)localization and its time development. The associated dynamics of the Fisher information functional quantifies nontrivial power transfer processes in the mean, both in dissipative and quantum mechanical cases.
PACS NUMBERS: 05.45.+b, 02.50.-r, 03.65.Ta, 03.67.-a 相似文献
65.
All-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity
Fei Wang 《Optics Communications》2006,257(2):334-339
A novel scheme for all-optical frequency multiplication/recovery based on a semiconductor optical amplifier ring cavity is proposed and investigated numerically. The results show, for a 2.5 GHz driving pulse train, it can be generated 5-25 GHz repetition rate pulse trains with low clock amplitude jitter, polarization independence and high peak power. Furthermore, the extraction of the clock signal from a pseudorandom bit sequence signal can be realized based on the proposed scheme. 相似文献
66.
We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.
67.
By using the quasi-Lyapunov function, some sufficient conditions of global exponential stability for impulsive systems are established, which is the basis for the following discussion. Then, by employing Riccati inequality and Hamilton-Jacobi inequality approach, some sufficient conditions of robust exponential stability for uncertain linear/nonlinear impulsive systems are derived, respectively. Finally, some examples are given to illustrate the applications of the theory. 相似文献
68.
Dan Voiculescu 《Reports on Mathematical Physics》2005,55(1):127-133
This short note summarizes the circumstances of the birth of free probability theory andsome of the recent achievements. 相似文献
69.
A localH-theorem is derived for a recently proposed extension of Enskog kinetic theory to a dense model fluid composed of particles with interactions extending beyond a hard core.On leave from: Katedra Fizyki, Uniwersytetu Szczecinskiego, 70-451 Szczecin, Poland. 相似文献
70.
MATLAB/SIMULINK在电力系统仿真中的应用 总被引:2,自引:0,他引:2
介绍了Matlab/Simulink仿真工具在电力系统仿真中的应用方法. 相似文献