全文获取类型
收费全文 | 6586篇 |
免费 | 1109篇 |
国内免费 | 848篇 |
专业分类
化学 | 4602篇 |
晶体学 | 47篇 |
力学 | 479篇 |
综合类 | 49篇 |
数学 | 790篇 |
物理学 | 2576篇 |
出版年
2024年 | 15篇 |
2023年 | 156篇 |
2022年 | 194篇 |
2021年 | 218篇 |
2020年 | 259篇 |
2019年 | 277篇 |
2018年 | 204篇 |
2017年 | 194篇 |
2016年 | 290篇 |
2015年 | 319篇 |
2014年 | 324篇 |
2013年 | 383篇 |
2012年 | 568篇 |
2011年 | 629篇 |
2010年 | 418篇 |
2009年 | 342篇 |
2008年 | 440篇 |
2007年 | 406篇 |
2006年 | 376篇 |
2005年 | 353篇 |
2004年 | 295篇 |
2003年 | 204篇 |
2002年 | 182篇 |
2001年 | 148篇 |
2000年 | 116篇 |
1999年 | 152篇 |
1998年 | 112篇 |
1997年 | 121篇 |
1996年 | 130篇 |
1995年 | 119篇 |
1994年 | 83篇 |
1993年 | 74篇 |
1992年 | 62篇 |
1991年 | 65篇 |
1990年 | 72篇 |
1989年 | 54篇 |
1988年 | 41篇 |
1987年 | 27篇 |
1986年 | 37篇 |
1985年 | 27篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1971年 | 2篇 |
1959年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有8543条查询结果,搜索用时 31 毫秒
31.
戴滨林 《数学物理学报(A辑)》2007,27(5):935-940
该文对高维非初等Mò'bius变换群进行了研究,得到了一些重要性质,给出了几个关于离散准则和代数收敛性的定理. 相似文献
32.
The atomic structures of indium (In) on silicon (Si) (1 0 0)-(2 × 1) surface are investigated by the local density approximation using first-principles pseudopotentials. Total energy optimizations show that the energetically favored structure is the parallel ad-dimer model. The adsorption energy of In on ideal Si(1 0 0)-(1 × 1) surface is significantly higher than that on reconstructed Si(1 0 0)-(2 × 1) surface, suggesting that In adsorption does not break the Si-Si dimer bond of the substrate. When Si surface contains single dimer vacancy defects, In chain will be interrupted, leading to disconnected In nanowires. Displacive adsorption of In on Si(1 0 0) is also considered, and the calculation suggests that interdiffusion of In into Si substrate will not be favorable under equilibrium conditions. 相似文献
33.
In this paper,the concept of the infinitesimal realization factor is extended to the parameter-dependent performance functions in closed queueing networks. Then the concepts of realization matrix (its elements are called realization factors) and performance potential are introduced,and the relations between infinitesimal realization factors and these two quantities are discussed. This provides a united framework for both IPA and non IPA approaches. Finally,another physical meaning of the service rate is given. 相似文献
34.
制备了纯的、掺0.005、0.01、0.2和0.5wt%Cr2O3的钛酸锶单晶.测量了不同退火条件下的室温透射光谱及6.5K以上的荧光光谱.对晶体的氧化和还原热处理诱导吸收及退火和掺杂浓度对晶体发光的影响进行了较为详细的研究. 相似文献
35.
36.
37.
Wen-Rong Dai 《Journal of Differential Equations》2007,235(1):127-165
In this paper, we study the global existence and the asymptotic behavior of classical solution of the Cauchy problem for quasilinear hyperbolic system with constant multiple and linearly degenerate characteristic fields. We prove that the global C1 solution exists uniquely if the BV norm of the initial data is sufficiently small. Based on the existence result on the global classical solution, we show that, when the time t tends to the infinity, the solution approaches a combination of C1 traveling wave solutions. Finally, we give an application to the equation for time-like extremal surfaces in the Minkowski space-time R1+n. 相似文献
38.
Thurston proposed that conformal mappings can be approximated by circle packing isomorphisms and the approach can be implemented efficiently. Based on the circle packing methods the rate of convergence of approximating solutions for quasiconformai mappings in the plane is discussed. 相似文献
39.
Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - (4.9 - x) AlF3(x=0, 0.5, 1.0, 1.5, 2.0) in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3+: ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3+ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3+ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions. 相似文献
40.