全文获取类型
收费全文 | 331963篇 |
免费 | 3522篇 |
国内免费 | 943篇 |
专业分类
化学 | 166757篇 |
晶体学 | 5397篇 |
力学 | 15552篇 |
综合类 | 7篇 |
数学 | 38511篇 |
物理学 | 110204篇 |
出版年
2021年 | 3150篇 |
2020年 | 3347篇 |
2019年 | 3789篇 |
2018年 | 5214篇 |
2017年 | 5459篇 |
2016年 | 7410篇 |
2015年 | 4183篇 |
2014年 | 7074篇 |
2013年 | 15983篇 |
2012年 | 12520篇 |
2011年 | 14985篇 |
2010年 | 11094篇 |
2009年 | 10998篇 |
2008年 | 13376篇 |
2007年 | 13342篇 |
2006年 | 12277篇 |
2005年 | 10674篇 |
2004年 | 9958篇 |
2003年 | 8807篇 |
2002年 | 8762篇 |
2001年 | 10463篇 |
2000年 | 7715篇 |
1999年 | 6019篇 |
1998年 | 4998篇 |
1997年 | 4845篇 |
1996年 | 4505篇 |
1995年 | 3892篇 |
1994年 | 3841篇 |
1993年 | 3726篇 |
1992年 | 4130篇 |
1991年 | 4331篇 |
1990年 | 4123篇 |
1989年 | 4029篇 |
1988年 | 3792篇 |
1987年 | 3950篇 |
1986年 | 3695篇 |
1985年 | 4657篇 |
1984年 | 4710篇 |
1983年 | 3897篇 |
1982年 | 3999篇 |
1981年 | 3723篇 |
1980年 | 3661篇 |
1979年 | 3945篇 |
1978年 | 3919篇 |
1977年 | 3923篇 |
1976年 | 3890篇 |
1975年 | 3688篇 |
1974年 | 3627篇 |
1973年 | 3659篇 |
1972年 | 2611篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
841.
A new approach to identify the independent amplitudes along with their partial wave multipole expansions, for photo-and electro-production
is suggested, which is generally applicable to mesons with arbitrary spin-parity. These amplitudes facilitate direct identification
of different resonance contributions.
相似文献
842.
I. A. Anoshko V. S. Ermachenko L. E. Sandrigailo 《Journal of Applied Spectroscopy》2007,74(1):102-106
We present the results of a spectroscopic study of a nonequilibrium plasma in a Hall accelerator, in particular for such an
important parameter as the electron temperature. For the studied conditions, we used the semicoronal equilibrium model, which
relates the intensity ratios for two successive ionization steps for the same element.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 93–96, January–February, 2007. 相似文献
843.
844.
Gary S. Nichol William Clegg 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(10):o609-o612
The title compound [systematic name: ammonium pyrimidine‐2,4‐5,6(1H,3H)‐tetrone 5‐oximate], NH4+·C4H2N3O4−, crystallizes from water in the triclinic space group P and is ismorphous with a known rubidium complex [Gillier (1965). Bull. Soc. Chim. Fr. pp. 2373–2384]. The principal feature of the structure is hydrogen bonding; each ammonium H atom acts as a bifurcated donor and three of the four violurate O atoms are bifurcated acceptors, with the fourth acting as a trifurcated acceptor. The pattern of hydrogen bonding around the cation is very similar to the rubidium coordination environment in the related structure. The violurate anions pack as hydrogen‐bonded crinkled tapes, which are linked and separated by the ammonium cations to give a compact three‐dimensional structure. 相似文献
845.
Maravanji S. Balakrishna Tristram Chivers Masood Parvez 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o617-o619
In both title structures, C40H32N4Si and C40H32N4Si·3C4H8O, the angles around the Si atom deviate significantly from the tetrahedral value [104.34 (7)–116.63 (7)° in the nonsolvate and 99.91 (15)–116.85 (15)° in the solvate]. The amino H atoms in the solvated structure are involved in hydrogen bonding with two of the tetrahydrofuran solvent molecules. 相似文献
846.
The phase transitions and phase state of hydroxypropylcellulose mixtures with ethanol and acetic acid under static conditions and in the shear field have been studied by the turbidity-point method and polarization microscopy with the use of a polarization-photoelectric setup and a modified plastoviscometer. The deformation of solutions leads to a decrease in the temperature of mesomorphic phase formation and to a change in the type of liquid crystals from cholesteric to nematic. 相似文献
847.
S. V. Valueva L. N. Borovikova V. V. Koreneva Ya. I. Nazarkina A. I. Kipper V. V. Kopeikin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(7):1170-1173
Nanostructures formed during the reduction of ionic selenium in the selenite-ascorbate redox system in an aqueous solution of bovine serum albumin (BSA) were studied using static and dynamic light scattering and flow birefringence. It was established that this process results in the formation of stable aggregates of selenium nanoparticles that adsorb BSA molecules. It was found that highly-ordered superhigh-molecular-weight spherical nanostructures with high density and unique morphology are formed. Experiments with a cell culture of promyelocytic leukemia HL-60 showed that BSA adsorbed on selenium nanoparticles can inhibit the growth of tumor cells and deactivate free radicals with an efficiency comparable with that of sodium selenite. 相似文献
848.
Received December 31, 2001 / Published online May 21, 2002 相似文献
849.
850.
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature. 相似文献