全文获取类型
收费全文 | 1946篇 |
免费 | 67篇 |
国内免费 | 13篇 |
专业分类
化学 | 1316篇 |
晶体学 | 54篇 |
力学 | 48篇 |
数学 | 233篇 |
物理学 | 375篇 |
出版年
2023年 | 12篇 |
2022年 | 46篇 |
2021年 | 48篇 |
2020年 | 48篇 |
2019年 | 38篇 |
2018年 | 40篇 |
2017年 | 47篇 |
2016年 | 67篇 |
2015年 | 42篇 |
2014年 | 62篇 |
2013年 | 137篇 |
2012年 | 110篇 |
2011年 | 122篇 |
2010年 | 77篇 |
2009年 | 60篇 |
2008年 | 83篇 |
2007年 | 93篇 |
2006年 | 97篇 |
2005年 | 82篇 |
2004年 | 80篇 |
2003年 | 59篇 |
2002年 | 49篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 17篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 27篇 |
1979年 | 20篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1976年 | 18篇 |
1974年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有2026条查询结果,搜索用时 296 毫秒
171.
[reaction: see text] Lewis acid-promoted addition of allyltri-n-butylstannane to o-quinonediimines afforded tetrahydroquinoxaline derivatives or allylated amides depending on the nature of the substituent on imine nitrogen. 相似文献
172.
Prakash TP Püschl A Lesnik E Mohan V Tereshko V Egli M Manoharan M 《Organic letters》2004,6(12):1971-1974
[structure: see text] Oligonucleotides with a novel 2'-O-[2-(guanidinium)ethyl] (2'-O-GE) modification have been synthesized using a novel protecting group strategy for the guanidinium group. This modification enhances the binding affinity of oligonucleotides to RNA as well as duplex DNA (DeltaT(m) 3.2 degrees C per modification). The 2'-O-GE modified oligonucleotides exhibited exceptional resistance to nuclease degradation. The crystal structure of a palindromic duplex formed by a DNA oligonucleotide with a single 2'-O-GE modification was solved at 1.16 A resolution. 相似文献
173.
Bruhat-Chevalley Order in Reductive Monoids 总被引:1,自引:1,他引:0
Mohan S. Putcha 《Journal of Algebraic Combinatorics》2004,20(1):33-53
174.
The ionization of real hydrogen atom is studied under the action of a two-color pulsed laser field of duration 2.12 fs consisting
of a fundamental frequencyω and one of its harmonics. We study the effect of phase difference (φ betweenω and its harmonic on the ionization probability. It is found that ionization can be switched on and off by varying the relative
phaseφ betweenω and its harmonic. 相似文献
175.
176.
We obtained a long-time-storage mechanism for spectral features in thulium ions doped into YAG by applying a magnetic field that splits the electronic ground state. We show experimentally that the storage time can be more than 30 s, which is 3 orders of magnitude longer than that of the metastable state that normally is used for information storage in this material. Level splitting and storage lifetimes for various magnetic field strengths of as much as 5 T were investigated. This storage mechanism will be relevant in the many coherent transient-based signal-processing schemes in which Tm:YAG is being used, and we demonstrate long-time storage in a basic data storage application. 相似文献
177.
Long wave evolution on free falling viscous films is described using a new evolution equation. The scaling proposed here brings in the viscous and pressure correction terms that are missing in the existing long-wave equations. Small amplitude expansion of the equation gives a dissipative form of the Kuromoto-Sivashinsky equation. Improved accuracy of the new equation over existing equations is demonstrated by comparison of neutral curves with Orr-Sommerfeld equations and experimental data. 相似文献
178.
The roots of Decalepis hamiltonii and Hemidesmus indicus are aromatic and possess the crystalline compound 2-hydroxy-4-methoxybenzaldehyde as the major compound (> 90%) in their volatile oils. A gas chromatographic procedure was developed for the assay of 2-hydroxy-4-methoxybenzaldehyde in both fresh and dried roots of different origin. Benzyl butyrate was used as the internal standard. Among the methods tried, steam hydrodistillation was suitable for extraction of the volatile oils. The quantity of this aromatic compound varied from 0.03 to 0.54%. 相似文献
179.
Chavan SP Sharma P Sivappa R Bhadbhade MM Gonnade RG Kalkote UR 《The Journal of organic chemistry》2003,68(17):6817-6819
Introduction of natural menthol as the chiral auxiliary in a gamma-Br-alpha,beta-unsaturated ester leads to enantioselective generation of three chiral centers in a single step on reaction with a glycine anion equivalent to provide L-CCG-I in 94% ee. 相似文献
180.
Anthracene anions bound to a liquid-liquid interface and charged by photochemically reduced Keggin ions when exposed to aqueous chloroaurate ions result in the formation of high concentration of thin, gold nanosheets at the interface. 相似文献