全文获取类型
收费全文 | 8345篇 |
免费 | 468篇 |
国内免费 | 63篇 |
专业分类
化学 | 6124篇 |
晶体学 | 62篇 |
力学 | 209篇 |
综合类 | 1篇 |
数学 | 882篇 |
物理学 | 1598篇 |
出版年
2023年 | 47篇 |
2022年 | 61篇 |
2021年 | 162篇 |
2020年 | 170篇 |
2019年 | 183篇 |
2018年 | 153篇 |
2017年 | 141篇 |
2016年 | 314篇 |
2015年 | 284篇 |
2014年 | 331篇 |
2013年 | 544篇 |
2012年 | 618篇 |
2011年 | 675篇 |
2010年 | 431篇 |
2009年 | 365篇 |
2008年 | 539篇 |
2007年 | 495篇 |
2006年 | 439篇 |
2005年 | 453篇 |
2004年 | 377篇 |
2003年 | 323篇 |
2002年 | 271篇 |
2001年 | 149篇 |
2000年 | 139篇 |
1999年 | 81篇 |
1998年 | 55篇 |
1997年 | 65篇 |
1996年 | 90篇 |
1995年 | 60篇 |
1994年 | 58篇 |
1993年 | 74篇 |
1992年 | 65篇 |
1991年 | 49篇 |
1990年 | 51篇 |
1989年 | 59篇 |
1988年 | 36篇 |
1987年 | 41篇 |
1986年 | 33篇 |
1985年 | 40篇 |
1984年 | 34篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 34篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 19篇 |
1977年 | 25篇 |
1976年 | 26篇 |
1975年 | 20篇 |
1974年 | 23篇 |
排序方式: 共有8876条查询结果,搜索用时 31 毫秒
91.
Joël J. E. Moreau Luc Vellutini Catherine Bied Michel Wong Chi Man 《Journal of Sol-Gel Science and Technology》2004,32(1-3):63-67
The acid-hydrolysis of an organo-bridged bisdiethoxysilylated molecular precursor bearing urea groups, (EtO)2MeSi(CH2)3NHCONH(CH2)12NHCONH(CH2)3SiMe(OEt)2, has been performed in pure aqueous medium. Scanning electron microscopy (SEM) analysis of the resulting insoluble solid revealed plate-like forms with a lamellar structure as determined by powder X-ray diffraction (PXRD) studies with a sharp peak at 28.5 Å. The solid state 29Si MAS-NMR spectrum of this bridged siloxane hybrid is consistent with a moderately condensed material with complete preservation of the Si–C bonds throughout the hybrid network. In comparison, the classical sol–gel hydrolysis-condensation of the molecular precursor in ethanol with stoichiometric amount of water and fluoride anion as catalyst produced an amorphous featureless solid. 相似文献
92.
Sodium hexafluoromanganate(III) has been synthesized by heating equimolecular quantities of Na2MnF5 and NaF in argon atmosphere. The compound is monoclinic witha=5.56 (1) Å,b=5.84 (1) Å,c=8.10 (2) Å, =90.7 (2) andZ=2. It is a high spin complex with
eff
and the deformation of the octahedra is evident from its IR-spectra. Two enantiotropic transitions (at 562 and 653°C) and the melting point at 800°C have been observed.
8. Mitt.: Mh. Chem.106, 483 (1975). 相似文献
8. Mitt.: Mh. Chem.106, 483 (1975). 相似文献
93.
Alves Lourdes A. Felipe Maria G. A. Silva JoÃo B. Almeida E. Silva Silvio S. Prata Arnaldo M. R. 《Applied biochemistry and biotechnology》1998,70(1):89-98
Applied Biochemistry and Biotechnology - In order to remove or reduce the concentrations of toxic substances present in the sugarcane bagasse hemicellulose hydrolysate for xyloseto-xylitol... 相似文献
94.
Tae Oan Ahn Jung Ho Kim Jong Chan Lee Han Mo Jeong Jong-Yoon Park 《Journal of polymer science. Part A, Polymer chemistry》1993,31(2):435-441
A macro-azoinitiator containing polyarylate segment and azo group was prepared by the solution polycondensation of azobiscyanopentanoyl chloride and hydroxy-terminated polyarylates having viscosity-average molecular weights of 6200, 8100, and 12 400. These macro-azoinitiators were used in the radical polymerization of styrene to synthesize polyarylate-polystyrene block copolymers. Thermal properties measured by the differential scanning calorimetry indicated the phase separated morphology of the block copolymers except at low molecular weight of the block constituents. © 1993 John Wiley & Sons, Inc. 相似文献
95.
96.
97.
98.
99.
Summary Real hypersurfaces of an almost Hermitian manifold naturally admit an almost contact metric structure and the (f, g, u, v, w, , , )-structure is defined on submanifolds of codimension 3 of an almost Hermitian manifold. We study the so-called semi-invariant submanifolds of a complex space form with almost contact metric compound structure which is a general notion of (f, g, u, v, w, , , )-structure.Dedicated to professor Eulyong Pak on his 60th birthdayThis research was partially supported by Korean Science and Engineering Foundation Grant. 相似文献
100.
Kwak WJ Han CK Chang HW Kim HP Kang SS Son KH 《Chemical & pharmaceutical bulletin》2003,51(3):333-335
A new triterpenoid saponin, loniceroside C was isolated from the aerial parts of Lonicera japonica. Its structure was established to be 3-O-beta-D-glucopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl (1-->2)-[beta-D-xylopyranosyl(1-->6)]-beta-D-glucopyranosyl ester by spectroscopic techniques and chemical transformations. Loniceroside C showed in vivo antiinflammatory activity against mouse ear edema provoked by croton oil. 相似文献