全文获取类型
收费全文 | 674篇 |
免费 | 93篇 |
国内免费 | 128篇 |
专业分类
化学 | 361篇 |
晶体学 | 22篇 |
力学 | 54篇 |
综合类 | 17篇 |
数学 | 72篇 |
物理学 | 369篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 25篇 |
2021年 | 22篇 |
2020年 | 20篇 |
2019年 | 10篇 |
2018年 | 16篇 |
2017年 | 30篇 |
2016年 | 24篇 |
2015年 | 24篇 |
2014年 | 34篇 |
2013年 | 59篇 |
2012年 | 65篇 |
2011年 | 66篇 |
2010年 | 56篇 |
2009年 | 55篇 |
2008年 | 55篇 |
2007年 | 58篇 |
2006年 | 54篇 |
2005年 | 49篇 |
2004年 | 32篇 |
2003年 | 14篇 |
2002年 | 24篇 |
2001年 | 22篇 |
2000年 | 18篇 |
1999年 | 12篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有895条查询结果,搜索用时 661 毫秒
811.
A new acyclic sesquiterpene oligoglycoside, named mukurozioside A, was isolated from pericarps of Sapindun mukurossi. On the basis of chemical and spectral evidence, the structure of mukurozioside A has been established as:11(S)-2,6(E,E)-dodecadiene-3,7,11-trimethyl-1,12-diol-1,12-bis-O-α-L-rhamnopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→3)]-6-O-acetyl-β-D-Glucopyranoside(1). 相似文献
812.
813.
研究了稀土元素La3+、Gd3+、Yb3+、Lu3+、Y3+及Sc3+对Eu-2-(2-二苯乙酰基)-1,3-茚二酮-阳离子表面活性剂体系的荧光增强效应,结果表明,在上述增强离子存在下,体系的荧光强度分别增加10、130、30、50、52和20倍,利用标准加入法测定了混合稀土氧化物中的铕,铕浓度在1.0×10-10~6.0×10-7mol/L范围内与荧光强度呈线性关系,最低检出限为6.0×10-12mol/L. 相似文献
814.
The adsorption and photochemical reduction process of Cu(Ⅱ) at the surface of nanocrystalline TiO2 was investigated using in situ quartz crystal microbalance(QCM). It was found that the adsorption of Cu(Ⅱ) onto active sites of nanocrystalline fit the pseudo-second-order reaction better than the pseudo-first-order reaction, and that the rate constant of the reaction was estimated to be about 0.09 g·mmol2·min2. In addition, it was also found that the adsorption amount of Cu(Ⅱ) at the surface of TiO2 was affected by pH、concentration and coexisting anions, and the saturated amount of adsorbed Cu(Ⅱ) was approximately 1.5 mmol·g-1 at pH 4. During UV illumination, the frequency of QCM decreased gradually, which meant the photoreduction deposition of Cu(Ⅱ) from the solution, moreover, the rate of photodeposition of Cu(Ⅱ) increased with increasing pH of solution, and the rate of photoreduction enhanced obviously when the organics were introduced. 相似文献
815.
新生儿呼吸困难56例病因分析 总被引:1,自引:0,他引:1
对56例新生儿呼吸困难病因进行了分析。结果表明,该病多数由肺部疾病或颅内疾病引起,也有代谢性酸中毒或先天性疾病引起的。 相似文献
816.
相分离聚合法:(Ⅰ)羧酸型共聚功能微球的合成 总被引:1,自引:0,他引:1
Crosslinked functional microspheres with Carboxylic group have been synthesized by the method of Phaseseparated polymerization from monomers of methacrylic acid and other vinyl-type monomers. The effects of reaction condition such as comonomer, crosslinking agent, initiator and polymerization temperature, as well as polymerization time on the morphological structure of microspheres formed have been studied. The functional polymeric microspheres with good spherical form, diameter near 5 micrometers, narrow dispersion in diameter and contained carboxylic group can be synthesized stably. 相似文献
817.
818.
The vaporization behavior of boron phosphate has been studied by using Knudsen effusion mass spectrometry. The vapor over BPO(4) consists of B(2)O(3), P(4)O(10), PO(2), BPO(4) (platinum cell) and B(2)O(3), PO, PO(2), BPO(3), BPO(4) (molybdenum cell). Standard enthalpies of formation and atomization (kJ/mol) were derived for BPO(4) (g) (-1000 +/- 15 and 2863 +/- 16) and for BPO(3) (g) (-731 +/- 15 and 2347 +/- 16), respectively. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
819.
Microwave-Controlled Light-Pulse Propagation in a Driven A-Type Atomic System with Two-Folded Levels
The temporal and spatial dynamics of one weak probe laser pulse, propagating through a A-type atomic medium with two-folded levels under the resonant excitation of one microwave driving field and one strong control field, is investigated in this paper. By numerically solving coupled Bloch-Maxwell equations, it is found that, in the absence of the microwave driving field, the atomic medium is transparent to the probe pulse at line center, which propagates over sufficiently long distances. By contrast, when the microwave driving field is applied, the probe pulse at line center can be rapidly absorbed on propagation. This substantial reduction of probe transmittance caused by the microwave driving field may lead to potential applications in designing a new kind of optical switching. 相似文献
820.
SI Zhihuai LI Hexian WANG Guochang** YUAN Jialong HE Binglin The State Key Laboratory of Functional Polymer Materials for Adsorption Separation Institute of Polymer Chemistry Nankai University Tianjin China 《Chinese Journal of Reactive Polymers》2001,(2)
1. INTRODUCTION The association of amphiphilic block copolymers has been the subject of numerous studies for several decades due to the academic interest and industrial applications [1~7]. It is well-known that block copolymers exhibit interesting domain structures in the solid state and form micelle-like aggregates in selective solvent [8]. They have found many potential applications in drug delivery [9], extraction of proteins [10], corrosion protection [11] as well as removal of aromat… 相似文献