全文获取类型
收费全文 | 7507篇 |
免费 | 550篇 |
国内免费 | 38篇 |
专业分类
化学 | 5672篇 |
晶体学 | 41篇 |
力学 | 191篇 |
综合类 | 1篇 |
数学 | 1166篇 |
物理学 | 1024篇 |
出版年
2022年 | 43篇 |
2021年 | 62篇 |
2020年 | 75篇 |
2019年 | 145篇 |
2018年 | 87篇 |
2017年 | 79篇 |
2016年 | 237篇 |
2015年 | 265篇 |
2014年 | 259篇 |
2013年 | 456篇 |
2012年 | 368篇 |
2011年 | 402篇 |
2010年 | 322篇 |
2009年 | 320篇 |
2008年 | 393篇 |
2007年 | 332篇 |
2006年 | 329篇 |
2005年 | 278篇 |
2004年 | 317篇 |
2003年 | 261篇 |
2002年 | 328篇 |
2001年 | 184篇 |
2000年 | 176篇 |
1999年 | 92篇 |
1998年 | 89篇 |
1997年 | 96篇 |
1996年 | 108篇 |
1995年 | 79篇 |
1994年 | 86篇 |
1993年 | 85篇 |
1992年 | 90篇 |
1991年 | 71篇 |
1990年 | 69篇 |
1989年 | 61篇 |
1988年 | 56篇 |
1987年 | 52篇 |
1986年 | 53篇 |
1985年 | 67篇 |
1984年 | 82篇 |
1983年 | 75篇 |
1982年 | 83篇 |
1981年 | 81篇 |
1980年 | 83篇 |
1979年 | 93篇 |
1978年 | 82篇 |
1977年 | 88篇 |
1976年 | 81篇 |
1975年 | 81篇 |
1974年 | 77篇 |
1973年 | 54篇 |
排序方式: 共有8095条查询结果,搜索用时 15 毫秒
951.
Jean Van Schaftingen 《Journal of Functional Analysis》2006,236(2):490-516
The function spaces Dk(Rn) are introduced and studied. The definition of these spaces is based on a regularity property for the critical Sobolev spaces Ws,p(Rn), where sp=n, obtained by J. Bourgain, H. Brezis, New estimates for the Laplacian, the div-curl, and related Hodge systems, C. R. Math. Acad. Sci. Paris 338 (7) (2004) 539-543 (see also J. Van Schaftingen, Estimates for L1-vector fields, C. R. Math. Acad. Sci. Paris 339 (3) (2004) 181-186). The spaces Dk(Rn) contain all the critical Sobolev spaces. They are embedded in BMO(Rn), but not in VMO(Rn). Moreover, they have some extension and trace properties that BMO(Rn) does not have. 相似文献
952.
Jean Olbregts 《国际化学动力学杂志》1993,25(2):125-135
Although hydrogen abstraction from 1,1,1,2-tetrachloroethane should produce only one kind of radical, CCl3CHCl, the presence of small amounts of trichloroethene, as impurity as well as product of reaction, induces the formation of the a priori unexpected CHCl2CCl2 radicals. The importance of this radical in the reaction pathways of the chlorination and the chlorine induced dehydrochlorination of CCl3CH2Cl, under different experimental conditions, is computed and discussed. For example, at 380 K, and for small partial pressures of chlorine (2 torr), the CHCl2CCl2 radicals account for more than 70% of the formation of the reaction products after only 2% reaction. The major role of trace quantities in long chain radical reactions is emphasized. © 1993 John Wiley & Sons, Inc. 相似文献
953.
E. I. Klimova C. Alvarez Toledano M. Martinez Garcia L. Gomez Lara N. N. Meleskonkova I. G. Bolesov 《Russian Chemical Bulletin》1996,45(3):613-619
Crystalline 3-ferrocenyl-3-phenylcyclopropene was obtained by dehydrobromination of 2-bromo-l-ferrocenyl-l-phenylcyclopropane with potassiumtert-butoxide in dimethyl sulfoxide. The compound synthesized undergoes catalytic hydrogenation to l-ferrocenyl-I-phenylcyclopropane, reacts with 1,3-diphenylisobenzofuran to give the expected product of stereospecific [4+2[-cycloaddition and 3-ferrocenylindene, and also undegoes opening of the small ring on treatment with superacids to give 3-ferrocenylindene as the major product. The data of single crystal X-ray diffraction analysis of 1-ferrocenyl-l-phenylcyclopropane and the diene adduct of 3-ferrocenyl-3-phenylcyclopropene with 1,3-diphenylisobenzofuran are given. 相似文献
954.
Juan C. Lpez Georges Wlodarczak Jean Demaison 《Journal of Molecular Spectroscopy》1996,180(2):337-344
The millimeter-wave spectrum of 2,3-dihydrofuran in the ground and five ring-puckering excited states has been measured in the frequency range 100–250 GHz. The ground and first ring-puckering excited states have been fitted to a two-state Hamiltonian including Coriolis coupling interaction. The determined energy difference of 18.684(7) cm−1between these states and theaandbtype coupling parameters are consistent with the ring-puckering potential function and the previously observed dependence of the centrifugal distortion constants ΔJK, ΔK, and δK. A small ring-puckering dependence of the quartic centrifugal distortion constants ΔJand δJhas been also observed. This dependence is well accounted for in terms of the ring-puckering potential function and the vibrational dependence of the rotational constants. 相似文献
955.
Octaethyltetraoxaporphyrin-Dikation – Pendant des Octaethylporphyrins in der Tetraoxaporphyrin-Reihe
956.
957.
958.
This paper deals with the existence of solutions to the periodic and the Sturm-Liouville boundary value problems for second order ordinary differential equations with singular nonlinearity. The results are obtained by use of some continuation theorems in the absence of a priori bounds of Capietto-Mawhin-Zanolin. 相似文献
959.
S. Laha Y. C. Chen P. Gupta C. E. Simien Y. N. Martinez P. G. Mickelson S. B. Nagel T. C. Killian 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):51-56
A study of ion equilibration in annular regions of ultracold strontium plasmas is reported. Plasmas are formed by photoionizing
laser-cooled atoms with a pulsed dye laser. The experimental probe is spatially-resolved absorption spectroscopy using the
2S1/2-2P1/2 transition of the Sr+ ion. The kinetic energy of the ions is calculated from the Doppler broadening of the spectrum, and it displays clear oscillations
during the first microsecond after plasma formation. The oscillations, which are a characteristic of strong coulomb coupling,
are fit with a simple phenomenological model incorporating damping and density variation in the plasma. 相似文献
960.