全文获取类型
收费全文 | 89035篇 |
免费 | 2273篇 |
国内免费 | 1937篇 |
专业分类
化学 | 32099篇 |
晶体学 | 1008篇 |
力学 | 7399篇 |
综合类 | 151篇 |
数学 | 33404篇 |
物理学 | 19184篇 |
出版年
2023年 | 197篇 |
2022年 | 335篇 |
2021年 | 357篇 |
2020年 | 495篇 |
2019年 | 485篇 |
2018年 | 10760篇 |
2017年 | 10599篇 |
2016年 | 6565篇 |
2015年 | 1496篇 |
2014年 | 996篇 |
2013年 | 1294篇 |
2012年 | 4859篇 |
2011年 | 11538篇 |
2010年 | 6436篇 |
2009年 | 6812篇 |
2008年 | 7431篇 |
2007年 | 9467篇 |
2006年 | 857篇 |
2005年 | 1850篇 |
2004年 | 1927篇 |
2003年 | 2294篇 |
2002年 | 1326篇 |
2001年 | 476篇 |
2000年 | 522篇 |
1999年 | 317篇 |
1998年 | 286篇 |
1997年 | 238篇 |
1996年 | 279篇 |
1995年 | 216篇 |
1994年 | 138篇 |
1993年 | 158篇 |
1992年 | 100篇 |
1991年 | 109篇 |
1990年 | 90篇 |
1989年 | 92篇 |
1988年 | 106篇 |
1987年 | 71篇 |
1986年 | 81篇 |
1985年 | 81篇 |
1984年 | 70篇 |
1983年 | 60篇 |
1982年 | 66篇 |
1981年 | 56篇 |
1980年 | 71篇 |
1979年 | 67篇 |
1978年 | 60篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 43篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Zygmunt Bak 《Czechoslovak Journal of Physics》2002,52(1):A25-A28
We consider RKKY interaction in a quasi 2D system with nonparabolic dispersion. In our paper we calculate the RKKY range function assuming the in-layer confinement via effective dimensionality approach. We show, that indirect magnetic exchange in our system can be modelled by the effective spectral dimension which equals one. 相似文献
42.
具Hardy-Sobolev临界指数的奇异椭圆方程多解的存在性 总被引:1,自引:0,他引:1
运用变分方法研究了下面问题-Δpu=μupx(s)s-2u f(x,u),x∈Ω,u=0,x∈Ω,多重解的存在性,其中Ω是一个具有光滑边界的有界区域. 相似文献
43.
44.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
45.
J Ashenfelter 《Pramana》2002,59(5):713-717
The ESTU began operation in 1988 and achieved the design voltage of 20 MV in 1990. Since that time, improvements to the gas
handling system, negative ion injector, accelerator terminal and control system have greatly increased its capability and
reliability. Today, the ESTU can efficiently produce an extensive assortment of stable ions at wide-ranging energies in support
of low-energy nuclear physics. 相似文献
46.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
47.
48.
Bo Jin Xi Wang Jing Chen Feng Zhang Xinli Cheng Zhijun Chen 《Applied Surface Science》2006,252(16):5627-5631
The oxidation of SiGe film epitaxial grown on top of SOI wafers has been studied. These SiGe/SOI samples were oxidized at 700, 900, 1100 °C. Germanium atoms were rejected from SiGe film to SOI layer. A new Si1−xGex (x is minimal) layer formed at SiGe/Si interface. As the germanium atoms diffused, the new Si1−xGex (x is minimal) layer moved to Si/SiO2 interface. Propagation of threading dislocation in SiGe film to SOI substrate was hindered by the new SiGe/Si interface. Strain in SOI substrate transferred from SiGe film was released through dislocation nucleation and propagation inner. The relaxation of SiGe film could be described as: strain relaxed through strain equalization and transfer process between SiGe film and SOI substrates. Raman spectroscopy was used to characterize the strain of SiGe film. Microstructure of SiGe/SOI was observed by transmission electron microscope (TEM). 相似文献
49.
50.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献