全文获取类型
收费全文 | 20964篇 |
免费 | 3737篇 |
国内免费 | 3122篇 |
专业分类
化学 | 15888篇 |
晶体学 | 240篇 |
力学 | 1178篇 |
综合类 | 208篇 |
数学 | 2627篇 |
物理学 | 7682篇 |
出版年
2024年 | 63篇 |
2023年 | 427篇 |
2022年 | 764篇 |
2021年 | 781篇 |
2020年 | 962篇 |
2019年 | 882篇 |
2018年 | 777篇 |
2017年 | 725篇 |
2016年 | 983篇 |
2015年 | 1110篇 |
2014年 | 1288篇 |
2013年 | 1558篇 |
2012年 | 1879篇 |
2011年 | 1969篇 |
2010年 | 1454篇 |
2009年 | 1313篇 |
2008年 | 1394篇 |
2007年 | 1277篇 |
2006年 | 1176篇 |
2005年 | 998篇 |
2004年 | 824篇 |
2003年 | 791篇 |
2002年 | 873篇 |
2001年 | 588篇 |
2000年 | 465篇 |
1999年 | 421篇 |
1998年 | 287篇 |
1997年 | 254篇 |
1996年 | 299篇 |
1995年 | 222篇 |
1994年 | 195篇 |
1993年 | 141篇 |
1992年 | 138篇 |
1991年 | 122篇 |
1990年 | 109篇 |
1989年 | 73篇 |
1988年 | 57篇 |
1987年 | 41篇 |
1986年 | 41篇 |
1985年 | 37篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1959年 | 1篇 |
1957年 | 3篇 |
1935年 | 1篇 |
1931年 | 1篇 |
1930年 | 3篇 |
1922年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
1引言 2006年3月 高等学校计算数学学报 设f(x)为卜1,1}上的连续函数,则以第二类Chebyshev多项式认(x)(Un(eoso)= 烈共坐)的全部零点{ 乙工工1口 式为 其中 k x无=Cos了一下丁7r 了L十1 犷_,为插值结点组的了的Gr如wald插值多项 G。(,,x)=艺了(x、)‘孟(x), n. 11 一一 k 相似文献
72.
Yan Shun MA Qing Hua MENG Hong Yu SHI Yuan De LONG Tian Bao HUANG 《中国化学快报》2006,17(6):807-808
Dencichine (β-N-oxalyl-L-α, β-diaminopropionic acid, L-ODAP), a nonprotein amino acid, is a haemostatic agent present in important Chinese medicinal herbs such as Panax notoginseng, as well as other Panax species1. It was first isolated from the seeds … 相似文献
73.
YBa2Cu3O7-δ and Tl2Ba2CaCu2O8 thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate
quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed. 相似文献
74.
75.
Jun Xiang Ge 《International Journal of Infrared and Millimeter Waves》1994,15(10):1681-1688
In 1991, we developed a new type of quasi-optical power combiner, called a compound quasi-optical power combiner, at Ka-band. In this paper, the circuit of such a compound quasi-optical power combiner is analysed. Its equivalent circuit model is proposed. The circuit equations, the balance condition, the injection locking and the stabilized condition of the compound quasi-optical power combiner are studed by the equivalent circuit model. As an example, a compound quasi-optical power combiner which consists of two single—cavity, two—device power combiners is analysed 相似文献
76.
低功率泵浦Ti:Al2O3自锁模激光器 总被引:2,自引:0,他引:2
本文报道了低功率泵浦的Ti:Al2O3激光器实现了稳定的自锁模运转,锁模脉冲宽度为180fs。分析了激光器的结构及工作特性。 相似文献
77.
设A是希尔伯特空间H上的自伴算子代数,α是A上的*-自同态.如果存在单位向量e∈H,使得对任意α∈A和单位向量h∈H,有lim_(n→∞)〈α~n(a)h,h〉=〈αe,e〉成立,那么称α是A上的σ-弱混合的*-自同态.本文研究了这一有趣性质,并得到了一个*-自同态是σ-弱混合的充分条件. 相似文献
78.
In this paper, a projection method is presented for solving the flow problems in domains with moving boundaries. In order to track the movement of the domain boundaries, arbitrary‐Lagrangian–Eulerian (ALE) co‐ordinates are used. The unsteady incompressible Navier–Stokes equations on the ALE co‐ordinates are solved by using a projection method developed in this paper. This projection method is based on the Bell's Godunov‐projection method. However, substantial changes are made so that this algorithm is capable of solving the ALE form of incompressible Navier–Stokes equations. Multi‐block structured grids are used to discretize the flow domains. The grid velocity is not explicitly computed; instead the volume change is used to account for the effect of grid movement. A new method is also proposed to compute the freestream capturing metrics so that the geometric conservation law (GCL) can be satisfied exactly in this algorithm. This projection method is also parallelized so that the state of the art high performance computers can be used to match the computation cost associated with the moving grid calculations. Several test cases are solved to verify the performance of this moving‐grid projection method. Copyright © 2004 John Wiley Sons, Ltd. 相似文献
79.
The central zinc(II) atom in the title complex is tetrahedrally coordinated by four nitrogen atoms derived from 4‐methyl‐5‐imidazolecarboxyaldehyde ligands with Zn? N in the range 2.007(3) to 2.026(4) Å. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
80.
Triterpenoid Constituents of Huperzia miyoshiana 总被引:1,自引:0,他引:1
Thirteen triterpenoids, including three new ones, miyoshianois A (1), B (2) and C (3), were isolated from Huperzia miyoshiana. The structures of these new compounds were established as 3-O-dihydroferuloyltohogenol (1), 16-oxo-3β,21β-dihydrox-y-serrat-14-en-24-ferulate (2) and 16-oxo-3a, 21β-dihydroxy-serrat-14-en-24-ferulate (3), respectively, on the basis of their spectroscopic analysis. 相似文献