全文获取类型
收费全文 | 7522篇 |
免费 | 1314篇 |
国内免费 | 1191篇 |
专业分类
化学 | 6091篇 |
晶体学 | 81篇 |
力学 | 400篇 |
综合类 | 83篇 |
数学 | 793篇 |
物理学 | 2579篇 |
出版年
2024年 | 30篇 |
2023年 | 149篇 |
2022年 | 324篇 |
2021年 | 334篇 |
2020年 | 361篇 |
2019年 | 413篇 |
2018年 | 306篇 |
2017年 | 286篇 |
2016年 | 404篇 |
2015年 | 418篇 |
2014年 | 459篇 |
2013年 | 588篇 |
2012年 | 709篇 |
2011年 | 669篇 |
2010年 | 415篇 |
2009年 | 426篇 |
2008年 | 459篇 |
2007年 | 368篇 |
2006年 | 360篇 |
2005年 | 321篇 |
2004年 | 278篇 |
2003年 | 245篇 |
2002年 | 328篇 |
2001年 | 268篇 |
2000年 | 168篇 |
1999年 | 150篇 |
1998年 | 129篇 |
1997年 | 74篇 |
1996年 | 83篇 |
1995年 | 63篇 |
1994年 | 64篇 |
1993年 | 51篇 |
1992年 | 78篇 |
1991年 | 49篇 |
1990年 | 50篇 |
1989年 | 32篇 |
1988年 | 22篇 |
1987年 | 24篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
1959年 | 2篇 |
1957年 | 2篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
讨论了浅海中波导的声波散射问题,我们将该问题归结为一个第一类边界积分方程,利用正同化方法求解,并证明了该方法的收敛性,数值例子表明了该方法的简单与有效性。 相似文献
2.
Jie Xue Liang Chen Li Zhou Zhifeng Jia Yanping Wang Xinyuan Zhu Deyue Yan 《Journal of Polymer Science.Polymer Physics》2006,44(15):2050-2057
α‐Cyclodextrin (α‐CD) has been complexed with various poly(ethylene glycol) (PEG) derivatives in aqueous solution. It has been found that the end groups of PEG derivatives affect the complexation kinetics greatly, but have only a little influence on the thermodynamic behavior. By increasing the hydrophobicity of end groups, the complexation speeds up rapidly. On the other hand, the bulky end groups slow down the threading of polymeric guests into the cavity of CD. By changing the hydrophobicity and the size of end groups, the complexation rate can be adjusted in the range of several orders of magnitudes, which should be quite useful in the design of new supramolecular systems. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2050–2057, 2006 相似文献
3.
Based on solving the couple mode equation numerically, the characterization of the signal power on the gate power was analyzed. And the relationship of the tolerance of the grating period and the bulk temperature on the interaction length was analyzed. 相似文献
4.
Protein Conformation of a Lattice Model Using Tabu Search 总被引:1,自引:0,他引:1
We apply tabu search techniques to the problem of determining the optimal configuration of a chain of protein sequences on a cubic lattice. The problem under study is difficult to solve because of the large number of possible conformations and enormous amount of computations required. Tabu search is an iterative heuristic procedure which has been shown to be a remarkably effective method for solving combinatorial optimization problems. In this paper, an algorithm is designed for the cubic lattice model using tabu search. The algorithm has been tested on a chain of 27 monomers. Computational results show that our method outperforms previously reported approaches for the same model. 相似文献
5.
Hui-Zhen Li Cheng-tian Xue 《International Journal of Infrared and Millimeter Waves》1991,12(12):1437-1449
This paper describes a global optimization design of quasi-optics power combiner of solid-state millimeterwave resonator. It is operated in the frequency range from 50 to 300 GHz using GaAs Gunn diodes. It is shown that sourcearrays containing N2 (N=3,5,...2K+1, where k is positive integer) individual elements. It is very efficient power transfer of energy from the source-array to the fractional power of the fundamental beam mode etc.. The RF output power exceeded the sum of the individual diodes to be threefold to sevenfold. And this data is the global optimization solution. 相似文献
6.
7.
All-optical wavelength conversion of 10-Gb/s signal based on four-wave mixing is experimentally demonstrated in a 30-m-long dispersion-flattened microstructure fiber with small positive dispersion. For an average pump power of 26 dBm, the conversion efficiency was around -19.5 dB with the fluctuation less than ±1.4 dB, covering a conversion bandwidth of 20 nm. The eye diagram of the converted signal shows good eye opening. 相似文献
8.
Hyperfine Interactions - Nanowires of metal, alloy, compound, and ferrite have been electrodeposited in anodic aluminium oxide templates. The structure and magnetic properties of the nanowires are... 相似文献
9.
Chemisorption of polybenzimidazole on silver and copper etched with nitric acid has been observed by surface-enhanced Raman scattering (SERS). The polymer is found to react chemically with silver, forming a complexed film on the surface. The SERS spectra show that polybenzimidazole film inhibits oxidation of the metal at high temperature, unlike chemisorbed benzimidazole, benzotriazole, and poly(4-vinyl pyridine). © 1992 John Wiley & Sons, Inc. 相似文献
10.
Hui-Zhen Li Cheng-tian Xue Xiang-wen Chen 《International Journal of Infrared and Millimeter Waves》1991,12(12):1425-1436
This paper describes a global optimization design for quasi-optics power combiner of solid-state millimeter-wave sources. The operating frequency is about 100 GHz and the oscillating sources are GaAs Gunn diodes. The source-array plane is a matrix consisting of NxN (N=3,5, ..., 2k+1, where k is positive integer) diodes. The radio frequency power of the combiner is from threefold to sevenfold larger than the sum total of the single diodes power. The global optimums of the array and the location in the cuvity of the suorce-array plane will be given by a global optimizition method. 相似文献