全文获取类型
收费全文 | 7824篇 |
免费 | 178篇 |
国内免费 | 97篇 |
专业分类
化学 | 4824篇 |
晶体学 | 82篇 |
力学 | 186篇 |
数学 | 1837篇 |
物理学 | 1170篇 |
出版年
2020年 | 82篇 |
2019年 | 68篇 |
2018年 | 85篇 |
2017年 | 50篇 |
2016年 | 153篇 |
2015年 | 129篇 |
2014年 | 127篇 |
2013年 | 431篇 |
2012年 | 350篇 |
2011年 | 397篇 |
2010年 | 248篇 |
2009年 | 217篇 |
2008年 | 349篇 |
2007年 | 355篇 |
2006年 | 422篇 |
2005年 | 406篇 |
2004年 | 357篇 |
2003年 | 289篇 |
2002年 | 261篇 |
2001年 | 91篇 |
2000年 | 66篇 |
1999年 | 77篇 |
1998年 | 74篇 |
1997年 | 90篇 |
1996年 | 139篇 |
1995年 | 101篇 |
1994年 | 95篇 |
1993年 | 83篇 |
1992年 | 92篇 |
1991年 | 87篇 |
1990年 | 74篇 |
1989年 | 68篇 |
1988年 | 59篇 |
1987年 | 79篇 |
1986年 | 69篇 |
1985年 | 110篇 |
1984年 | 138篇 |
1983年 | 101篇 |
1982年 | 106篇 |
1981年 | 123篇 |
1980年 | 138篇 |
1979年 | 110篇 |
1978年 | 116篇 |
1977年 | 98篇 |
1976年 | 101篇 |
1975年 | 114篇 |
1974年 | 101篇 |
1973年 | 105篇 |
1972年 | 55篇 |
1971年 | 46篇 |
排序方式: 共有8099条查询结果,搜索用时 15 毫秒
1.
2.
Extremes - We propose a new test statistic $$\mathrm {MR}_{\gamma ,n}$$ for detecting a changed segment in the mean, at unknown dates, in a regularly varying sample. Our model supports several... 相似文献
3.
4.
Na Shao Xueyang Liu Dr. Valérie Monnier Dr. Laurence Charles Dr. Jean Rodriguez Dr. Cyril Bressy Dr. Adrien Quintard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(5):e202103874
Elaboration of enantioenriched complex acyclic stereotriads represents a challenge for modern synthesis even more when fluorinated tetrasubstituted stereocenters are targeted. We have been able to develop a simple strategy in a sequence of two unprecedented steps combining a diastereoselective aldol-Tishchenko reaction and an enantioselective organocatalyzed kinetic resolution. The aldol-Tishchenko reaction directly generates a large panel of acyclic 1,3-diols possessing a fluorinated tetrasubstituted stereocenter by condensation of fluorinated ketones with aldehydes under very mild basic conditions. The anti 1,3-diols featuring three contiguous stereogenic centers are generated with excellent diastereocontrol (typically >99 : 1 dr). Depending upon the precursors both diastereomers of stereotriads are accessible through this flexible reaction. Furthermore, from the obtained racemic scaffolds, development of an organocatalyzed kinetic resolution enabled to generate the desired enantioenriched stereotriads with excellent selectivity (typically er >95 : 5). 相似文献
5.
Gabrielle A. Leith Allison M. Rice Brandon J. Yarbrough Anna A. Berseneva Richard T. Ly Charles N. Buck III Dr. Denis Chusov Amy J. Brandt Prof. Dr. Donna A. Chen Benjamin W. Lamm Prof. Dr. Morgan Stefik Kenneth S. Stephenson Dr. Mark D. Smith Prof. Dr. Aaron K. Vannucci Dr. Perry J. Pellechia Prof. Dr. Sophya Garashchuk Prof. Dr. Natalia B. Shustova 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(15):6056-6062
The effect of donor (D)–acceptor (A) alignment on the materials electronic structure was probed for the first time using novel purely organic porous crystalline materials with covalently bound two- and three-dimensional acceptors. The first studies towards estimation of charge transfer rates as a function of acceptor stacking are in line with the experimentally observed drastic, eight-fold conductivity enhancement. The first evaluation of redox behavior of buckyball- or tetracyanoquinodimethane-integrated crystalline was conducted. In parallel with tailoring the D-A alignment responsible for “static” changes in materials properties, an external stimulus was applied for “dynamic” control of the electronic profiles. Overall, the presented D–A strategic design, with stimuli-controlled electronic behavior, redox activity, and modularity could be used as a blueprint for the development of electroactive and conductive multidimensional and multifunctional crystalline porous materials. 相似文献
6.
7.
8.
9.
10.
Transition Metal Chemistry - (η5-Dp)Ru(PPh3)2H (Dp?=?C8H9?, 1,2-dihydropentalenyl) was synthesized in 90% yield by reaction of (η5-Dp)Ru(PPh3)2Cl with sodium formate.... 相似文献