全文获取类型
收费全文 | 10941篇 |
免费 | 1891篇 |
国内免费 | 1214篇 |
专业分类
化学 | 7741篇 |
晶体学 | 88篇 |
力学 | 712篇 |
综合类 | 88篇 |
数学 | 1219篇 |
物理学 | 4198篇 |
出版年
2024年 | 34篇 |
2023年 | 244篇 |
2022年 | 393篇 |
2021年 | 418篇 |
2020年 | 442篇 |
2019年 | 421篇 |
2018年 | 400篇 |
2017年 | 319篇 |
2016年 | 570篇 |
2015年 | 497篇 |
2014年 | 619篇 |
2013年 | 819篇 |
2012年 | 1020篇 |
2011年 | 995篇 |
2010年 | 688篇 |
2009年 | 676篇 |
2008年 | 693篇 |
2007年 | 602篇 |
2006年 | 575篇 |
2005年 | 467篇 |
2004年 | 365篇 |
2003年 | 281篇 |
2002年 | 242篇 |
2001年 | 204篇 |
2000年 | 244篇 |
1999年 | 271篇 |
1998年 | 218篇 |
1997年 | 188篇 |
1996年 | 218篇 |
1995年 | 166篇 |
1994年 | 140篇 |
1993年 | 102篇 |
1992年 | 111篇 |
1991年 | 65篇 |
1990年 | 84篇 |
1989年 | 57篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 40篇 |
1985年 | 43篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
71.
本文对Brauer第24问题[1]作了推广.利用Dade关于循环块的理论得到如下结果:设G是有限群,P是G的循环Sylowp子群.设|P|=pa,a为正整数.令Pi为P中唯一的pi阶子群,1ia.则|Cl(G)|=|Cl(NG(Pi))|的充分必要条件为PiG. 相似文献
72.
Cao Xuan Chuan 《International Journal of Theoretical Physics》1998,37(9):2439-2448
It is shown that in the case of shapeinvariance, with the use of the mixing functionformalism, exact solvability of the Schrodinger equationcan be obtained without recourse to the technique ofsupersymmetrization. Some consequences of the method are outlinedand illustrated by specific examples. 相似文献
73.
Y.Y. Sun I. Rusakova R.L. Meng Y. Cao P. Gautier-Picard C.W. Chu 《Physica C: Superconductivity and its Applications》1994,230(3-4):435-442
We have carried out a systematic structural, electric, and magnetic study on Y---Pd---B---C samples with different compositions with emphasis on the as-cast and annealed YPd5B3C0.3 which was first reported to superconduct at 23 K by Cava et al. We found that the tetragonal body-centered YPd2B2C with lattice parameters a=3.71 Å and c=10.81 Å is the phase responsible for the 23 K superconductivity and that YPd2B2C is metastable, which is consistent with the suggestion made by Cava et al. [1]: it is not stable at high temperatures nor stabilizable by Ni doping, although its isostructural compound, YNi2B2C, exists. Two new phases with Y:Pd ratios of 1:7 and 2:3, respectively, have also bee detected. 相似文献
74.
本文推导了两种非标准色传感器在测色时引入的误差公式,并对其进行分析。最后通过计算8个样品的颜色对分析结果给于验证。 相似文献
75.
The article referenced above was first published online on 7 August 2007 with incorrect pagination; the pagination has now been corrected online and in print. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
76.
Zhigang Zhang Jianping Deng Weiguo Zhao Jianmin Wang Wantai Yang 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):500-508
A novel chiral N‐propargylsulfamide monomer ( 1a ) and its enantiomer ( 1b ) were synthesized and polymerized with (nbd)Rh+B?(C6H5)4 as a catalyst providing poly(1) (poly( 1a ) and poly( 1b )) in high yields (≥99%). Poly(1) could take stable helices in less polar solvents (chloroform and THF), demonstrated by strong circular dichroism signals and UV–vis absorption peaks at about 415 nm and the large specific rotations; but in more polar solvents including DMF and DMSO, poly(1) failed to form helix. Quantitative evaluation with anisotropy factor showed that the helical screw sense had a relatively high thermal stability. These results together with the IR spectra measured in solvents showed that hydrogen bonding between the neighboring sulfamide groups is one of the main driving forces for poly(1) to adopt stable helices. In addition, copolymerization of monomer 1a and monomer 2 was conducted, the solubility of poly(1) was improved drastically. However, the copolymerization had adverse effects on the formation of stable helices in the copolymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 500–508, 2007 相似文献
77.
78.
A simple and rapid method is developed to determine the high acidity and the basicity of solutions by chronopotentiometry with a platinum working electrode. The acidity range from 5.0 mol/l H+ to 1.0 mol/l OH− can be measured by the adjustment of deposition potential and time. The response mechanism to acidity and basicity has been explored. The transition potential plateau in chronopotentiograms is caused from the oxidation of hydrogen adsorbed on electrode surface. 相似文献
79.
80.
负关联噪声驱动下单模激光的定态分析 总被引:2,自引:1,他引:1
研究了负关联的加法和乘法高斯白噪声驱动下单模激光损失模型的定态情况。文中推导了负关联情况下,定态时的激光场幅的几率分布,光强的平均值,光强的协方差以及光强的偏斜率。并和文献〔1,2〕中正关联时的定态分析作了比较,发现了有意义的新现象。 相似文献