全文获取类型
收费全文 | 175157篇 |
免费 | 15806篇 |
国内免费 | 12284篇 |
专业分类
化学 | 91801篇 |
晶体学 | 1917篇 |
力学 | 12987篇 |
综合类 | 904篇 |
数学 | 43162篇 |
物理学 | 52476篇 |
出版年
2024年 | 316篇 |
2023年 | 1899篇 |
2022年 | 3361篇 |
2021年 | 3580篇 |
2020年 | 3702篇 |
2019年 | 3650篇 |
2018年 | 12954篇 |
2017年 | 12659篇 |
2016年 | 10070篇 |
2015年 | 5518篇 |
2014年 | 5969篇 |
2013年 | 7739篇 |
2012年 | 12402篇 |
2011年 | 18990篇 |
2010年 | 11601篇 |
2009年 | 12031篇 |
2008年 | 12999篇 |
2007年 | 14316篇 |
2006年 | 5747篇 |
2005年 | 5933篇 |
2004年 | 5141篇 |
2003年 | 4792篇 |
2002年 | 3706篇 |
2001年 | 2614篇 |
2000年 | 2404篇 |
1999年 | 2264篇 |
1998年 | 1931篇 |
1997年 | 1672篇 |
1996年 | 1748篇 |
1995年 | 1436篇 |
1994年 | 1336篇 |
1993年 | 1163篇 |
1992年 | 983篇 |
1991年 | 855篇 |
1990年 | 727篇 |
1989年 | 622篇 |
1988年 | 499篇 |
1987年 | 465篇 |
1986年 | 419篇 |
1985年 | 390篇 |
1984年 | 263篇 |
1983年 | 240篇 |
1982年 | 198篇 |
1981年 | 162篇 |
1980年 | 135篇 |
1979年 | 110篇 |
1978年 | 97篇 |
1977年 | 81篇 |
1975年 | 78篇 |
1973年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Qipeng Guo Fei Chen Ke Wang Ling Chen 《Journal of Polymer Science.Polymer Physics》2006,44(21):3042-3052
An amphiphilic poly(ethylene oxide)‐block‐poly(dimethylsiloxane) (PEO–PDMS) diblock copolymer was used to template a bisphenol A type epoxy resin (ER); nanostructured thermoset blends of ER and PEO–PDMS were prepared with 4,4′‐methylenedianiline (MDA) as the curing agent. The phase behavior, crystallization, hydrogen‐bonding interactions, and nanoscale structures were investigated with differential scanning calorimetry, Fourier transform infrared spectroscopy, transmission electron microscopy, and small‐angle X‐ray scattering. The uncured ER was miscible with the poly(ethylene oxide) block of PEO–PDMS, and the uncured blends were not macroscopically phase‐separated. Macroscopic phase separation took place in the MDA‐cured ER/PEO–PDMS blends containing 60–80 wt % PEO–PDMS diblock copolymer. However, the composition‐dependent nanostructures were formed in the cured blends with 10–50 wt % PEO–PDMS, which did not show macroscopic phase separation. The poly(dimethylsiloxane) microdomains with sizes of 10–20 nm were dispersed in a continuous ER‐rich phase; the average distance between the neighboring microdomains was in the range of 20–50 nm. The miscibility between the cured ER and the poly(ethylene oxide) block of PEO–PDMS was ascribed to the favorable hydrogen‐bonding interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3042–3052, 2006 相似文献
12.
13.
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
14.
从点电荷的电势计算公式出发推导出了瓣形均匀带电面在其直径处的电势分布.进一步讨论了均匀带电半球面在其底面以及均匀带电球面内部和外部的电势分布. 相似文献
15.
Chunguang Du Hongyi Chen Shiqun Li 《量子光学学报》2006,12(B08):70-71
Recently, research on left-handed materials (LHMs) has attracted considerable attentions. The LHMs are a kind of metameterial which have negative permittivity and negative permeability, which lead to negative refractive index in a frequency range. The LHMs that have been available so far are in the microwave range and are usually composed of classical particles, such as split-ring resonators. Some quantum phenomena such as spontaneous emission of atoms in the LHMs which are considered to be 'classical background' have also been investigated. Many potential applications of LHMs have been proposed, such as superlenses which, in principle, can achieve arbitrary subwavelength resolution. 相似文献
16.
17.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
18.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
19.
20.
Claudia-Elisabeth Wulz 《Czechoslovak Journal of Physics》2002,52(3):C155-C170
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described. 相似文献