全文获取类型
收费全文 | 10044篇 |
免费 | 1782篇 |
国内免费 | 1536篇 |
专业分类
化学 | 7370篇 |
晶体学 | 268篇 |
力学 | 451篇 |
综合类 | 130篇 |
数学 | 1195篇 |
物理学 | 3948篇 |
出版年
2024年 | 39篇 |
2023年 | 164篇 |
2022年 | 355篇 |
2021年 | 349篇 |
2020年 | 378篇 |
2019年 | 454篇 |
2018年 | 339篇 |
2017年 | 340篇 |
2016年 | 462篇 |
2015年 | 551篇 |
2014年 | 656篇 |
2013年 | 785篇 |
2012年 | 955篇 |
2011年 | 929篇 |
2010年 | 755篇 |
2009年 | 746篇 |
2008年 | 811篇 |
2007年 | 719篇 |
2006年 | 621篇 |
2005年 | 485篇 |
2004年 | 429篇 |
2003年 | 312篇 |
2002年 | 284篇 |
2001年 | 232篇 |
2000年 | 162篇 |
1999年 | 160篇 |
1998年 | 115篇 |
1997年 | 97篇 |
1996年 | 113篇 |
1995年 | 100篇 |
1994年 | 84篇 |
1993年 | 75篇 |
1992年 | 64篇 |
1991年 | 44篇 |
1990年 | 39篇 |
1989年 | 25篇 |
1988年 | 36篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1959年 | 1篇 |
1957年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
K. W. Cheah L. C. Ho J. B. Xia J. Li W. H. Zheng W. R. Zhuang Q. M. Wang 《Applied Physics A: Materials Science & Processing》1995,60(6):601-606
Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100–150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of andX band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers. 相似文献
182.
Cr1-x
Fe
x
and Mn1-x
Fe
x
films were prepared at room temperature by thermal coevaporation at a deposition rate of about 25 Å/min. It was found that an amorphous phase can be obtained for Cr1-x
Fe
x
(0.25<x<0.60) films, while a metastable-Mn-type phase was observed for Mn1-x
Fe
x
(x<0.70) films. The influence of the structure on the magnetic properties has been studied. The amorphization ability of the two systems was discussed in terms of thermodynamic considerations. 相似文献
183.
184.
Daoxing Xia 《Proceedings of the American Mathematical Society》1996,124(6):1743-1753
The generalized cyclic cohomology is introduced which is associated with -deformed commutators . Some formulas related to the trace of the product of -deformed commutators are established. The Chern character of odd dimension associated with -deformed commutators is studied.
185.
186.
187.
188.
189.
Supported iron tetrasulfophthalocyanine can efficiently catalyze the degradation of organic pollutants by H2O2 under visible light irradiation in an aqueous solution, and the catalyst can be easily recycled without apparent loss of activity. 相似文献
190.
A sensitive bioassay for estimating the activity of Trichosanthin was developed by using intraoocyte microinjection as the technique and germinal vescicle breakdown as a marker. The GVBD inhibitory activity assay was million-fold more sensitive than the routinely used abortifacient activity assay. The detectable amount of Trichosanthin ranged from 0.5 to 100 pg. Since the least detectable dose was 0.5 pg, it made the assay suitable to analyse the microquantity of pure Trichosanthin used for studying the structure and function of the drug. 相似文献