全文获取类型
收费全文 | 8343篇 |
免费 | 1431篇 |
国内免费 | 866篇 |
专业分类
化学 | 5936篇 |
晶体学 | 58篇 |
力学 | 508篇 |
综合类 | 69篇 |
数学 | 1182篇 |
物理学 | 2887篇 |
出版年
2024年 | 16篇 |
2023年 | 164篇 |
2022年 | 185篇 |
2021年 | 295篇 |
2020年 | 395篇 |
2019年 | 312篇 |
2018年 | 294篇 |
2017年 | 266篇 |
2016年 | 397篇 |
2015年 | 420篇 |
2014年 | 463篇 |
2013年 | 587篇 |
2012年 | 761篇 |
2011年 | 827篇 |
2010年 | 532篇 |
2009年 | 498篇 |
2008年 | 535篇 |
2007年 | 489篇 |
2006年 | 474篇 |
2005年 | 343篇 |
2004年 | 294篇 |
2003年 | 197篇 |
2002年 | 210篇 |
2001年 | 138篇 |
2000年 | 162篇 |
1999年 | 172篇 |
1998年 | 159篇 |
1997年 | 167篇 |
1996年 | 147篇 |
1995年 | 131篇 |
1994年 | 114篇 |
1993年 | 110篇 |
1992年 | 75篇 |
1991年 | 66篇 |
1990年 | 66篇 |
1989年 | 41篇 |
1988年 | 38篇 |
1987年 | 32篇 |
1986年 | 14篇 |
1985年 | 24篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1916年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
We study the following nonlinear Schrodinger system where P(τ) and Q(τ) are positive radial functions,μ 0,v 0,and β∈ R is a coupling constant.This type of system arises,particularly,in models in Bose-Einstein condensates theory.Applying a finite reduction method,we construct an unbounded sequence of nonradial positive vector solutions of segregated type when β is in some suitable interval,which gives an answer to an interesting problem raised by Peng and Wang in Remark 4.1(Arch.Ration.Mech.Anal.,208(2013),305-339). 相似文献
993.
The stereoselective synthesis of C12 oxygenated marine scalaranic sesterterpene 16-deacetoxy-12-epi-scalarafuran acetate and its 14-epimer were described. A highly stereoselective intramolecular Diels-Alder addition was designed as the key step to construct the ring D, and the absolute configurations of natural 16-deacetoxy-12-epi-scalarafuran acetate was supported by the X-ray diffraction analysis of single crystal of corresponding 16-deacetoxy-12-epi-scalarafuran. 相似文献
994.
Yan YangMeng Gao Liu-Ming WuCong Deng Dong-Xue ZhangYang Gao Yan-Ping ZhuAn-Xin Wu 《Tetrahedron》2011,67(29):5142-5149
The convergent and linear domino reactions have been first integrated, for the first time, to provide an efficient synthesis of indole-furan conjugates from indoles, methyl ketones, and 1,3-dicarbonyl compounds. 相似文献
995.
Daowan LaiYongxin Li Minjuan XuZhiwei Deng Leen van OfwegenPeiyuan Qian Peter ProkschWenhan Lin 《Tetrahedron》2011,67(33):6018-6029
Chemical examination of a Chinese soft coral Sinularia rigida resulted in the isolation and characterization of 19 new cembrane-type diterpenoids, designated as sinulariols A-S (1-19). Their structures were determined on the basis of extensive spectroscopic (2D NMR, IR, and MS) analysis in association with modified Mosher’s method. All compounds featured unusual 19-oxygenated functionalities, which are rarely found from cembranoid family. The biogenetic transformation of the isolated compounds is postulated. Part of the isolated cembranoids showed significant anti-fouling activity. 相似文献
996.
Two new complexes, {[Co(INAIP) · H2O] · 2H2O}n ( 1 ), and {[Cu(INAIP)] · H2O}n ( 2 ) [H2INAIP = 5‐(isonicotinamido)isophthalic acid] were synthesized under hydrothermal conditions, and characterized by single‐crystal X‐ray structure determination, thermogravimetric analysis, X‐ray powder diffraction, and magnetic studies. In complex 1 both CoII atoms and INAIP2– ligands act as four‐connected node, whereas in 2 both CuII atoms and INAIP2– ligands act as three‐connected node. 相似文献
997.
Submicron-sized P(St-NaSS) latexes were prepared via a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate(NaSS) in the presence of anionic surfactant,in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time.The hydrodynamic diameter of the latex particles was measured by dynamic light scattering(DSL) method,and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis.Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96%in the absence of crosslinker,and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h.The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge.The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol%DVB of total NaSS and St were used in the recipe,and the monomer feeding time was 3 h in copolymerization,the NaSS unit content of the purified copolymer reached 7.31 mol%. 相似文献
998.
Ma M He Z Yang J Chen F Wang K Zhang Q Deng H Fu Q 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):13072-13081
In this Article, the morphological evolution in the blend thin film of polystyrene (PS)/poly(ε-caprolactone) (PCL) was investigated via mainly AFM. It was found that an enriched two-layer structure with PS at the upper layer and PCL at the bottom layer was formed during spinning coating. By changing the solution concentration, different kinds of crystal morphologies, such as finger-like, dendritic, and spherulitic-like, could be obtained at the bottom PCL layer. These different initial states led to the morphological evolution processes to be quite different from each other, so the phase separation, dewetting, and crystalline morphology of PS/PCL blend films as a function of time were studied. It was interesting to find that the morphological evolution of PS at the upper layer was largely dependent on the film thickness. For the ultrathin (15 nm) blend film, a liquid-solid/liquid-liquid dewetting-wetting process was observed, forming ribbons that rupture into discrete circular PS islands on voronoi finger-like PCL crystal. For the thick (30 nm) blend film, the liquid-liquid dewetting of the upper PS layer from the underlying adsorbed PCL layer was found, forming interconnected rim structures that rupture into discrete circular PS islands embedded in the single lamellar PCL dendritic crystal due to Rayleigh instability. For the thicker (60 nm) blend film, a two-step liquid-liquid dewetting process with regular holes decorated with dendritic PCL crystal at early annealing stage and small holes decorated with spherulite-like PCL crystal among the early dewetting holes at later annealing stage was observed. The mechanism of this unusual morphological evolution process was discussed on the basis of the entropy effect and annealing-induced phase separation. 相似文献
999.
1000.