全文获取类型
收费全文 | 319419篇 |
免费 | 3261篇 |
国内免费 | 1770篇 |
专业分类
化学 | 156617篇 |
晶体学 | 4236篇 |
力学 | 16392篇 |
综合类 | 72篇 |
数学 | 59245篇 |
物理学 | 87888篇 |
出版年
2020年 | 2122篇 |
2019年 | 2426篇 |
2018年 | 13427篇 |
2017年 | 13370篇 |
2016年 | 10715篇 |
2015年 | 3794篇 |
2014年 | 4846篇 |
2013年 | 10688篇 |
2012年 | 12704篇 |
2011年 | 20905篇 |
2010年 | 13582篇 |
2009年 | 13739篇 |
2008年 | 16627篇 |
2007年 | 18680篇 |
2006年 | 9911篇 |
2005年 | 9849篇 |
2004年 | 9019篇 |
2003年 | 8409篇 |
2002年 | 7439篇 |
2001年 | 7264篇 |
2000年 | 5902篇 |
1999年 | 4134篇 |
1998年 | 3630篇 |
1997年 | 3534篇 |
1996年 | 3352篇 |
1995年 | 2805篇 |
1994年 | 2877篇 |
1993年 | 2729篇 |
1992年 | 2936篇 |
1991年 | 3018篇 |
1990年 | 2806篇 |
1989年 | 2717篇 |
1988年 | 2658篇 |
1987年 | 2601篇 |
1986年 | 2619篇 |
1985年 | 3430篇 |
1984年 | 3487篇 |
1983年 | 2896篇 |
1982年 | 3174篇 |
1981年 | 2905篇 |
1980年 | 2725篇 |
1979年 | 2885篇 |
1978年 | 3106篇 |
1977年 | 3105篇 |
1976年 | 3130篇 |
1975年 | 2848篇 |
1974年 | 2958篇 |
1973年 | 3009篇 |
1972年 | 2354篇 |
1971年 | 1871篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
A. R. Volkov B. V. Shul'gin T. I. Polupanova V. N. Lebedev A. A. Nagornyi V. L. Petrov Yu. F. Kargin 《Journal of Applied Spectroscopy》1991,54(6):585-590
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 6, pp. 970–975, June, 1991. 相似文献
43.
In a twisted nematic liquid crystal cell we report and study the self-transparency effect induced by the creation of an isotropic droplet. A simple theoretical model is presented and good agreement with experimental data is found. In a two beams configuration transistor-like behavior is observed and theoretically discussed. 相似文献
44.
45.
I. L. Davies K. E. Markides M. L. Lee M. W. Raynor K. D. Bartle 《Journal of separation science》1989,12(4):193-207
Although coupled liquid chromatographygas chromatography (LC-GC) was first demonstrated ten years ago, only in the last few years has there been a sudden surge of interest in the technique. Approximately 70% of the total number of LC-GC applications have been published in the last two years (1987–88) alone. This review categorizes LC-GC publications into four main application areas: fossil fuels, foods, environmental samples, biologiical/pharmaceutical samples, and miscellaneous samples. Multidimensional separations carried out using other coupled-column chromatographic techniques (such as supercritical fluid chromatography (SFC) with GC, and on-line trace enrichment-GC) have also been included in this review. 相似文献
46.
47.
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
48.
The direct regioselective C–H arylation of 3-methoxythiophene and 3,4-ethylenedioxythiophene (EDOT) was performed successfully under ‘Heck-type’ experimental conditions. This novel synthetic methodology has been used to prepare in a more simple way a series of oligothiophenes interesting for the electronic industry to build new synthetic organic materials. 相似文献
49.
(S)-2-[2-(p-Tolylsulfinyl)phenyl]acetaldehyde reacts with different O-silylated ketenethioacetals in the presence of Yb(OTf)3 yielding β-hydroxythioesters in high yields and diastereoselectivities. The obtained compounds were readily transformed into β-hydroxyacids and their corresponding diols. These Mukaiyama aldol reactions are a direct evidence of the ability of the sulfinyl group to control 1,5- and 1,6-asymmetric induction processes. 相似文献
50.
S. N. Solov’ev K. A. Minasyan A. A. Korunov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):663-664
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol. 相似文献