全文获取类型
收费全文 | 140223篇 |
免费 | 18483篇 |
国内免费 | 11410篇 |
专业分类
化学 | 85909篇 |
晶体学 | 1572篇 |
力学 | 8638篇 |
综合类 | 618篇 |
数学 | 21465篇 |
物理学 | 51914篇 |
出版年
2024年 | 401篇 |
2023年 | 2273篇 |
2022年 | 3902篇 |
2021年 | 4285篇 |
2020年 | 4566篇 |
2019年 | 4422篇 |
2018年 | 4913篇 |
2017年 | 4905篇 |
2016年 | 6105篇 |
2015年 | 5777篇 |
2014年 | 6826篇 |
2013年 | 8900篇 |
2012年 | 13017篇 |
2011年 | 12575篇 |
2010年 | 8644篇 |
2009年 | 8061篇 |
2008年 | 7513篇 |
2007年 | 6920篇 |
2006年 | 6367篇 |
2005年 | 9127篇 |
2004年 | 7420篇 |
2003年 | 5063篇 |
2002年 | 3086篇 |
2001年 | 2403篇 |
2000年 | 1989篇 |
1999年 | 2344篇 |
1998年 | 2036篇 |
1997年 | 1866篇 |
1996年 | 2014篇 |
1995年 | 1631篇 |
1994年 | 1577篇 |
1993年 | 1252篇 |
1992年 | 1285篇 |
1991年 | 1173篇 |
1990年 | 962篇 |
1989年 | 711篇 |
1988年 | 581篇 |
1987年 | 458篇 |
1986年 | 433篇 |
1985年 | 384篇 |
1984年 | 285篇 |
1983年 | 190篇 |
1982年 | 167篇 |
1981年 | 133篇 |
1980年 | 89篇 |
1979年 | 75篇 |
1976年 | 115篇 |
1975年 | 70篇 |
1974年 | 85篇 |
1973年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
By constructing close-one-cochain density Ω^12n in the gauge group space we get the Wess-Zumino-Witten (WZW) effective Lagrangian on high-dimensional noncommutative space.Especially consistent anomalies derived from this WZW effective action in noncommutative four-dimensional space coincide with those obtained by L.Bonora etc.(het-th/0002210). 相似文献
92.
Several α-ketoalcohols of synthetic value were resolved using lipase as a catalyst. Lipoprotein lipase (LPL) provided the best rate of hydrolysis and kinetic differentiation. One of these optically pure α-ketoalcohol was converted to (5)-ibuprofen in good optical purity. The stereospecific inversion of (R)-alcohol to (S)-alcohol is described. 相似文献
93.
94.
The structural stability of heat-treated CoN/CN soft X-ray multilayers fabricated by dual-facing-target sputtering has been investigated by using complementary measurement techniques. The high temperature annealing results imply that the destructive threshold of the Co/C multilayers is improved by 100–200 degrees centigrade through doping with N. The low-angle X-ray diffraction of CoN/CN soft X-ray multilayers indicates that the period expansion of the multilayers is only 4 % at 400°C, and the interface pattern still exists even if they were annealed at 700°C. The Raman spectra analyses give the evidence that the formation of the sp3 bonding in the CN sublayers can be suppressed effectively by doping N with atoms, and thus the period expansion resulting from the changes in the density of CN layers can be decreased considerably. The X-ray photoelectron spectra analyses present the information of the existence of the strong covalent bonding betweenC andN atoms, and the ionic bonding between Co and N atoms, which can slow down the tendency of the structural relaxation. The interstitial N atoms decrease the mobility of Co atoms, and thus the fcc-Co and hcp-Co coexist even though the annealing temperature is much higher than the phase transformation temperature of 420°C, leading to the suppression of the grain growth. 相似文献
95.
97.
98.
谐振子薛定谔方程的简单解法 总被引:2,自引:0,他引:2
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。 相似文献
99.
High-level ab initio calculations are carried out to study the relative stability of the two hydrogen bonded structures of water-hydrogen sulfide complex, one with water as the proton donor (A) and the other with hydrogen sulfide as the proton donor (B). The results show that structure A is considerably more stable than B at the correlated level, which is in contrast with previous results obtained from Hartree-Fock calculations. 相似文献