全文获取类型
收费全文 | 42771篇 |
免费 | 7009篇 |
国内免费 | 5106篇 |
专业分类
化学 | 30357篇 |
晶体学 | 537篇 |
力学 | 2563篇 |
综合类 | 400篇 |
数学 | 4711篇 |
物理学 | 16318篇 |
出版年
2024年 | 142篇 |
2023年 | 916篇 |
2022年 | 1468篇 |
2021年 | 1606篇 |
2020年 | 1738篇 |
2019年 | 1767篇 |
2018年 | 1454篇 |
2017年 | 1356篇 |
2016年 | 2053篇 |
2015年 | 2103篇 |
2014年 | 2523篇 |
2013年 | 3115篇 |
2012年 | 3761篇 |
2011年 | 3857篇 |
2010年 | 2600篇 |
2009年 | 2431篇 |
2008年 | 2737篇 |
2007年 | 2490篇 |
2006年 | 2245篇 |
2005年 | 1935篇 |
2004年 | 1458篇 |
2003年 | 1247篇 |
2002年 | 1188篇 |
2001年 | 910篇 |
2000年 | 858篇 |
1999年 | 933篇 |
1998年 | 732篇 |
1997年 | 704篇 |
1996年 | 657篇 |
1995年 | 573篇 |
1994年 | 550篇 |
1993年 | 478篇 |
1992年 | 368篇 |
1991年 | 364篇 |
1990年 | 325篇 |
1989年 | 238篇 |
1988年 | 199篇 |
1987年 | 165篇 |
1986年 | 132篇 |
1985年 | 111篇 |
1984年 | 90篇 |
1983年 | 57篇 |
1982年 | 68篇 |
1981年 | 44篇 |
1980年 | 28篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1970年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Zhong Hong YAN Chun Hao YANG Xi Han WU Yu Yuan XIEDivision of Chemistry Shanghai Second Medical University Shanghai Sate Key Laboratory of Drug Research Shanghai Institute of Materia Medica Shanghai Institutesfor Biological Sciences Shanghai 《中国化学快报》2004,(4)
The first and facile synthesis of (±)syringaresinol was described. 相似文献
32.
Zhao Zheng Zhang Jian-hua Jiang Ya-ling 《International Journal of Theoretical Physics》1997,36(6):1359-1368
The Hawking effect of a nonuniformly rectilinearly accelerating Kinnersley black hole is studied. Its horizons are rotationally
symmetric. Its Hawking temperature depends not only on the time, but also on the polar angle. When a Kinnersley black hole
touches its Rindler horizon, the Hawking temperature at the contact point is reduced to zero. But at the opposite pole of
the black hole, the Hawking temperature increases rapidly. A jet appears as a tail of the accelerating black hole. 相似文献
33.
报道了KDP晶体中的三倍频产生的实验研究,计算了比较了直接三倍频过程和级联过程对KDP晶体三阶有效非线性系数的贡献,并探讨了KDP作为非线性晶体材料三阶非线性系数测量基准的可行性。 相似文献
34.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献
35.
OU型Markov过程的不变测度及弱对偶性 总被引:1,自引:1,他引:0
本文研究OU型Markov过程的不变测度、参考测度和弱对偶半群的存在性问题,并得出了不变测度的唯一性。 相似文献
36.
The thermal and thermo-elastic-plastic response of newly developed ceramic-metalfunctionally graded materials under a thermal shock load is studied.The materials are heated at the ce-ramic surface with a sudden high-intensity heat flux input,and cooled at the metal surface with aflowing liquid nitrogen.Emphasis is placed on two aspects:(1)the influence of the graded composi-tion of the materials on the temperature and stress response;and(2)the optimum design of the gradedcomposition from a unified viewpoint of the heat insulation property and stress relaxation property.Moreover,a comparison between the thermoelastic stress and the thermo-elastic-plastic stress is alsomade to indicate the plasticity effect. 相似文献
37.
38.
39.
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
40.