全文获取类型
收费全文 | 22130篇 |
免费 | 4142篇 |
国内免费 | 5868篇 |
专业分类
化学 | 16999篇 |
晶体学 | 728篇 |
力学 | 1224篇 |
综合类 | 562篇 |
数学 | 2842篇 |
物理学 | 9785篇 |
出版年
2024年 | 63篇 |
2023年 | 296篇 |
2022年 | 819篇 |
2021年 | 782篇 |
2020年 | 889篇 |
2019年 | 844篇 |
2018年 | 862篇 |
2017年 | 1016篇 |
2016年 | 952篇 |
2015年 | 1163篇 |
2014年 | 1437篇 |
2013年 | 1863篇 |
2012年 | 1882篇 |
2011年 | 2062篇 |
2010年 | 1833篇 |
2009年 | 1815篇 |
2008年 | 1984篇 |
2007年 | 1766篇 |
2006年 | 1599篇 |
2005年 | 1315篇 |
2004年 | 1046篇 |
2003年 | 866篇 |
2002年 | 898篇 |
2001年 | 827篇 |
2000年 | 799篇 |
1999年 | 480篇 |
1998年 | 285篇 |
1997年 | 213篇 |
1996年 | 248篇 |
1995年 | 157篇 |
1994年 | 187篇 |
1993年 | 128篇 |
1992年 | 118篇 |
1991年 | 100篇 |
1990年 | 81篇 |
1989年 | 70篇 |
1988年 | 63篇 |
1987年 | 52篇 |
1986年 | 41篇 |
1985年 | 39篇 |
1984年 | 33篇 |
1983年 | 30篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 12篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
Hui Li 《Tetrahedron letters》2006,47(20):3485-3488
A general entry to C(1) aryl-substituted glycals from the corresponding sugar lactones is described. This approach features one-pot access to aryl glycals. A variety of aryllithium reagents can be used and the method is compatible with various 2-deoxysugar lactones. 相似文献
132.
0IntroductionThe solid-state chemistry of manganese!car-boxylate coordination polymers has received growingattention over the past few years,owing to their fasci-nating network topologies and potential application inthe field of molecular magnetism and bi… 相似文献
133.
0IntroductionRareearthsarenowappliedwidelyinChina,whichcanimprovecropsyieldsandthetheirqualit-ies犤1犦.Thebeneficialeffectsmaybeduetothestimu-latoryeffectsoftheseelementsonthenutrientuptakebyplantsorontheincreasingofchlorophyllsynthesisintheplants犤2犦.Whilealotofresearcheshavebeendoneontheimprovednutritionofcropsafterapplica-tionofrareearths,muchlessattentionhasbeenpaidtothedeteriorationofsoilqualityduetotheapplicationofrareearthsforyears犤3犦.Scientistshavediscoveredthataccumula… 相似文献
134.
A procedure for the Raman spectra calculation of vitreous and molten silicates was presented in this paper. It includes molecular dynamics MD simulation for the generation of equilibrium configurations, Wilson's GF matrix method for the calculations of eigenfrequencies and corresponding vectors, electro-optical parameters method (EOPM) for the Raman intensity calculations, and the bond polarizability model (BPM) for the determination of polarizability and polarizability derivative. One of the most important characteristics of this procedure is the achievement of the partial Raman spectra of five tetrahedral units, as well as the total spectral envelope. In this paper, the calculation was carried out for the vitreous and molten calcium silicates with different compositions and at various temperatures. It is worthwhile to note that the calculation is based on statistical configurations distribution in the space and so it is not needed to artificially adjust the full width at half maximum (FWHM) of spectra. It was also tested through the good agreement of the calculated spectra with the experimental, including some regularity of spectral properties. According to the calculation, the symmetrical stretching of whole tetrahedral units, to which the stretching of Si-O(nb) bond gives the main contribution to intensity, is proven to be the dominance in the high-frequency range (800-1200 cm(-1)) and the symmetrical bending of Si-O(b)-Si, to which the stretching of Si-O(b) bond exhibits the main contribution, is the dominance in the medium-frequency range (400-700 cm(-1)). As the first theoretical results, the Raman scattering coefficient of each Q(i) was found little change along with the variation of composition and temperature. 相似文献
135.
136.
Jin Hui YANG Jiu Gao YU Xiao Fei MA 《中国化学快报》2006,17(1):133-136
TPS was a biodegradable material based on starch. Starch was an inexpensive and natural renewable polysaccharide, which was widely investigated as the substitute of petroleum-derived plastics. Native starch commonly existed in granule structure with about… 相似文献
137.
138.
139.
Study on the Phase Diagram of CsCl-CeCl3-HCl(11%)-H2O System and the Properties of the Compounds 总被引:2,自引:0,他引:2
The equilibrium solubility of CsCl-CeCl3-HCl(11%)-H2O qua-ternary system at 25℃ has been determined by the physicchemical analysis method ,and the phase diagram was plotted, Two new double salts 3CsCl.CeCl3.3H2O and CsCl.CeCl3.4H2O obtained from the complicated system were identified and characterized by XRD,TG-DTA ,DSC,UV and fluorescence spectroscopy, Studies on the fluorescence excitation and emission show that 3CsCl.CeCl3.3H2O and CsCl.CeCl3.4H2O have upconversion luminescence of infrared-visible range,and the upconversion emission intensity increases with the increase of ratio of CeCl3 in CsCl. 相似文献
140.