全文获取类型
收费全文 | 32938篇 |
免费 | 5047篇 |
国内免费 | 2573篇 |
专业分类
化学 | 6144篇 |
晶体学 | 82篇 |
力学 | 3624篇 |
综合类 | 735篇 |
数学 | 18801篇 |
物理学 | 11172篇 |
出版年
2024年 | 64篇 |
2023年 | 318篇 |
2022年 | 637篇 |
2021年 | 749篇 |
2020年 | 905篇 |
2019年 | 855篇 |
2018年 | 828篇 |
2017年 | 1149篇 |
2016年 | 1288篇 |
2015年 | 1010篇 |
2014年 | 1781篇 |
2013年 | 2587篇 |
2012年 | 1793篇 |
2011年 | 2023篇 |
2010年 | 1786篇 |
2009年 | 2095篇 |
2008年 | 2159篇 |
2007年 | 2297篇 |
2006年 | 1958篇 |
2005年 | 1707篇 |
2004年 | 1621篇 |
2003年 | 1438篇 |
2002年 | 1372篇 |
2001年 | 1092篇 |
2000年 | 1002篇 |
1999年 | 961篇 |
1998年 | 792篇 |
1997年 | 723篇 |
1996年 | 574篇 |
1995年 | 519篇 |
1994年 | 364篇 |
1993年 | 287篇 |
1992年 | 253篇 |
1991年 | 237篇 |
1990年 | 178篇 |
1989年 | 123篇 |
1988年 | 140篇 |
1987年 | 103篇 |
1986年 | 92篇 |
1985年 | 115篇 |
1984年 | 102篇 |
1983年 | 57篇 |
1982年 | 72篇 |
1981年 | 78篇 |
1980年 | 62篇 |
1979年 | 65篇 |
1978年 | 32篇 |
1977年 | 34篇 |
1976年 | 31篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
On Quantum Team Games 总被引:2,自引:0,他引:2
E. Ahmed M. F. Elettreby A. S. Hegazi 《International Journal of Theoretical Physics》2006,45(5):880-886
Recently Liu and Simaan (2004) convex static multi-team classical games have been introduced. Here they are generalized to both nonconvex, dynamic and quantum games. Puu's incomplete information dynamical systems are modified and applied to Cournot team game. The replicator dynamics of the quantum prisoner's dilemma game is also studied. 相似文献
52.
设f是非常数亚纯函数,g是f的线性微分多项式.a和b是f的两个不同的小函数.本文证明如果f和g几乎CM分担a和b,则f≡g;此外,若f是非常数整函数,且f和f(k)(k≥1)IM分担a和b,b-a≠Peλz,测f≡g. 相似文献
53.
方程w"-w+f(t,w)=O的Dirichlet边值问题的正解存在性与多解性 总被引:1,自引:0,他引:1
姚庆六 《应用泛函分析学报》2002,4(1):4-9
考察了下列常微分方程的Dirichlet边值问题的正解[w″(t)-w(t) f(t,w(t))=0,0≤t≤1 w(0)=w(1)=0建立了n正解的存在性,其中n是一个任意的自然数。 相似文献
54.
Johannes Elschner Rainer Hinder Gunther Schmidt 《Advances in Computational Mathematics》2002,16(2-3):139-156
This paper is devoted to the numerical study of diffraction by periodic structures of plane waves under oblique incidence. For this situation Maxwell's equations can be reduced to a system of two Helmholtz equations in R
2 coupled via quasiperiodic transmission conditions on the piecewise smooth interfaces between different materials. The numerical analysis is based on a strongly elliptic variational formulation of the differential problem in a bounded periodic cell involving nonlocal boundary operators. We obtain existence and uniqueness results for discrete solutions and provide the corresponding error analysis. 相似文献
55.
新颖外燃式湿空气燃气轮机循环及性能研究 总被引:2,自引:0,他引:2
本文首先提出一种新型的高效燃煤燃气轮机循环一外燃式湿空气透平循环动力系统。由于外燃的特点,作功工质为洁净湿空气,从而可以实现水的回收,是对常规HAT循环的突破;另外洁净湿空气排放不受通常烟气露点限制,从而可回收利用湿空气降温时的低温凝结潜热,提高了加湿能力,从而提高系统性能。揭示了新型循环的基本规律;推导出具有湿化特点的约束方程和系统性能简明表达式,指明影响系统性能的关键因素。在透平初温为850℃的工况下,系统热效率高达48.11%。基于能量品位梯级利用原理和系统集成方法论,通过探索充分而合理利用中低温余热的有效途径,开拓洁净煤燃气轮机总能系统的新方向。 相似文献
56.
Several a priori tests of a systematic stochastic mode reduction procedure recently devised by the authors [Proc. Natl. Acad. Sci. 96 (1999) 14687; Commun. Pure Appl. Math. 54 (2001) 891] are developed here. In this procedure, reduced stochastic equations for a smaller collections of resolved variables are derived systematically for complex nonlinear systems with many degrees of freedom and a large collection of unresolved variables. While the above approach is mathematically rigorous in the limit when the ratio of correlation times between the resolved and the unresolved variables is arbitrary small, it is shown here on a systematic hierarchy of models that this ratio can be surprisingly big. Typically, the systematic reduced stochastic modeling yields quantitatively realistic dynamics for ratios as large as 1/2. The examples studied here vary from instructive stochastic triad models to prototype complex systems with many degrees of freedom utilizing the truncated Burgers–Hopf equations as a nonlinear heat bath. Systematic quantitative tests for the stochastic modeling procedure are developed here which involve the stationary distribution and the two-time correlations for the second and fourth moments including the resolved variables and the energy in the resolved variables. In an important illustrative example presented here, the nonlinear original system involves 102 degrees of freedom and the reduced stochastic model predicted by the theory for two resolved variables involves both nonlinear interaction and multiplicative noises. Even for large value of the correlation time ratio of the order of 1/2, the reduced stochastic model with two degrees of freedom captures the essentially nonlinear and non-Gaussian statistics of the original nonlinear systems with 102 modes extremely well. Furthermore, it is shown here that the standard regression fitting of the second-order correlations alone fails to reproduce the nonlinear stochastic dynamics in this example. 相似文献
57.
Capillary Electrophoresis Chiral Separation for Enantiomeric Purity Determination of a Basic Drug in Pharmaceutical Formulations 总被引:1,自引:0,他引:1
Capillary electrophoresis using a running buffer composed of β-cyclodextrin as the chiral selector and ethanolamine mesylate at pH 9.6 is being used to monitor the stereochemical stability of a hydrophobic drug, containing two chiral centers, in two different formulated self-emulsifying drug delivery system (SEDDS) products. The separation takes place in less than 25 min. Strategies for enhancing the method reproducibility and detection sensitivity in the lower potency formulation are presented. The results demonstrating the specificity, assay precision, recovery, linearity and range achieved during the method validation experiments are presented in this paper.Presented at: CE in the Biotechnology and Pharmaceutical Industries: 7th Symposium on the Practical Applications for the Analysis of Proteins, Nucleotides and Small Molecules, Montreal, Canada, August 12–16, 2005. 相似文献
58.
59.
60.
光学系统是自动生化分析仪的核心部件,其性能的好坏将直接影响整机性能。根据生化分析的检测要求,通过理论分析和实验对该仪器光学系统的各个部分进行了研究和设计。实现了两种设计方案,通过实验分析选择了较优的方案。 相似文献