全文获取类型
收费全文 | 340207篇 |
免费 | 4392篇 |
国内免费 | 1366篇 |
专业分类
化学 | 180257篇 |
晶体学 | 4699篇 |
力学 | 14314篇 |
综合类 | 19篇 |
数学 | 45000篇 |
物理学 | 101676篇 |
出版年
2020年 | 2015篇 |
2019年 | 1989篇 |
2018年 | 3117篇 |
2017年 | 3280篇 |
2016年 | 4559篇 |
2015年 | 3777篇 |
2014年 | 4898篇 |
2013年 | 14608篇 |
2012年 | 13494篇 |
2011年 | 15486篇 |
2010年 | 9738篇 |
2009年 | 9545篇 |
2008年 | 12915篇 |
2007年 | 13212篇 |
2006年 | 12806篇 |
2005年 | 15263篇 |
2004年 | 13710篇 |
2003年 | 10967篇 |
2002年 | 9173篇 |
2001年 | 10320篇 |
2000年 | 7808篇 |
1999年 | 6245篇 |
1998年 | 4989篇 |
1997年 | 4811篇 |
1996年 | 4833篇 |
1995年 | 4417篇 |
1994年 | 4173篇 |
1993年 | 3974篇 |
1992年 | 4550篇 |
1991年 | 4400篇 |
1990年 | 4115篇 |
1989年 | 3907篇 |
1988年 | 4190篇 |
1987年 | 3831篇 |
1986年 | 3717篇 |
1985年 | 5357篇 |
1984年 | 5425篇 |
1983年 | 4406篇 |
1982年 | 4775篇 |
1981年 | 4817篇 |
1980年 | 4565篇 |
1979年 | 4694篇 |
1978年 | 4697篇 |
1977年 | 4672篇 |
1976年 | 4657篇 |
1975年 | 4545篇 |
1974年 | 4400篇 |
1973年 | 4574篇 |
1972年 | 2607篇 |
1971年 | 1906篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
L. V. Giurgiu M. N. Grecu X. Filip O. Raita Al. Darabont D. Gavre J. Blasco 《Applied magnetic resonance》2003,24(3-4):351-360
We report an electron paramagnetic resonance (EPR) investigation of the spin dynamics in the paramagnetic regime of the colossal magnetoresistive manganites La2/3Ca1/3Mn1?x Me x O3 (Me=Al, In;x≤0.05). The temperature dependences of the EPR linewidth and integral intensity have been analyzed in terms of the bottleneck spin relaxation and small-polaron hopping models. The exchange coupling integral between Mn3+ and Mn4+ ions and the polaron activation energy decrease with increasing doping level. A discussion is given concerning the factors which could explain the observed changes. 相似文献
992.
993.
David J. Aitken Dominique Guillaume Henri-Philippe Husson Angle Chiaroni Claude Riche 《Journal of heterocyclic chemistry》1991,28(3):705-709
The title compound, containing a new heterocyclic skeleton, was identified by X-ray crystallography as the product of condensation of (R)-phenylglycinol with an excess of formaldehyde. The molecule adopts a rigid double twist-chair conformation in both solid and solution states. 相似文献
994.
E. Beinrohr M. Németh P. Tsch?pel G. T?lg 《Fresenius' Journal of Analytical Chemistry》1992,344(3):93-99
Summary Flow-through electrochemical cells with porous working electrodes made of crushed reticulated vitreous carbon and plated with mercury were used for absolute analysis of trace amounts of lead by anodic stripping coulometry with collection (ASCWC) in a flow system. The role of mercury coating, flow rate and pH were investigated. The coulombic content of the collection peak corresponded to the theoretical values calculated by Faraday's law in a concentration range from about 10–9 to 10–6 mol/l. The relative error and the relative standard deviation was +0.15% and 0.8%, respectively for 2×10–6 mol/l analyte concentration. The absolute detection limit (3 s) was 0.1 ng of Pb, the linear response range 7×104.
One leave from: Department of Analytical Chemistry, Slovak Technical University, CS-812 37 Bratislava, Czechoslovakia 相似文献
995.
996.
Július Korbaš 《Acta Mathematica Hungarica》2004,105(1-2):129-137
We prove new results about the vector field problem on the real flag manifolds O(n)/O(1) x O(1) x O(n - 2). For some infinite families of these manifolds, we completely solve the vector field problem. 相似文献
997.
We investigate a new parallel all-optical clock recovery scheme based on heterodyne beats of an optical sideband-filtered signal. The oscillating clock signal is recovered when the filtered sideband is combined with a stable local oscillator. The filtering is performed with an optical resonator, which by nature provides possibility for multiwavelength operation. The local oscillator could be realized by a multiwavelength laser, whose emission wavelengths are injection seeded with carrier wavelengths of the input data. The output signal of such a configuration benefits from a reduced bit-pattern effect and a stable offset level. The sideband filtering is demonstrated for 23 simultaneous channels at 100 GHz DWDM grid, each hosting a data stream of 10 Gbit/s. 相似文献
998.
Celik Tarimci Anda? Karamustafa Kutalmi? Güven Mehmet Kabak Akgül Ye?ilada 《Analytical sciences》2003,19(9):1347-1348
The crystal structure of 1-[3-(3,4-dimethoxyphenyl)-2-propenoyl]pyrrolidine (C15H19NO3) (I) has been determined by X-ray analysis. It crystallizes orthorhombic space group Pbca with a = 24.295(3), b = 15.086(3), c = 7.552(3)A, V = 2768(1)A3, Z = 8, Dcalc = 1.254 g/cm3, mu = (Mo K(alpha)) = 0.87 cm(-1). The title compound has analgesic activity of cycloaliphatic amine part. The molecule is deviated from planar configuration. 相似文献
999.
1000.