全文获取类型
收费全文 | 330190篇 |
免费 | 10859篇 |
国内免费 | 1713篇 |
专业分类
化学 | 175610篇 |
晶体学 | 4931篇 |
力学 | 17262篇 |
综合类 | 3篇 |
数学 | 43725篇 |
物理学 | 101231篇 |
出版年
2021年 | 3222篇 |
2020年 | 4595篇 |
2019年 | 6694篇 |
2018年 | 7194篇 |
2017年 | 7041篇 |
2016年 | 11189篇 |
2015年 | 6909篇 |
2014年 | 10167篇 |
2013年 | 15967篇 |
2012年 | 12821篇 |
2011年 | 13730篇 |
2010年 | 12648篇 |
2009年 | 12787篇 |
2008年 | 13582篇 |
2007年 | 12766篇 |
2006年 | 11259篇 |
2005年 | 10083篇 |
2004年 | 9659篇 |
2003年 | 8966篇 |
2002年 | 9927篇 |
2001年 | 8967篇 |
2000年 | 7275篇 |
1999年 | 4816篇 |
1998年 | 4289篇 |
1997年 | 4141篇 |
1996年 | 3734篇 |
1995年 | 3296篇 |
1994年 | 3358篇 |
1993年 | 3374篇 |
1992年 | 3379篇 |
1991年 | 3786篇 |
1990年 | 3787篇 |
1989年 | 3794篇 |
1988年 | 3545篇 |
1987年 | 3628篇 |
1986年 | 3320篇 |
1985年 | 3850篇 |
1984年 | 4083篇 |
1983年 | 3488篇 |
1982年 | 3686篇 |
1981年 | 3372篇 |
1980年 | 3132篇 |
1979年 | 3621篇 |
1978年 | 3686篇 |
1977年 | 3856篇 |
1976年 | 3928篇 |
1975年 | 3674篇 |
1974年 | 3527篇 |
1973年 | 3688篇 |
1972年 | 3178篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
V. A. Bespalov V. M. Glazov E. A. Il’ichev Yu. A. Klimov S. V. Kuklev A. E. Kuleshov R. M. Nabiev G. N. Petrukhin B. G. Potapov G. S. Rychkov D. S. Sokolov V. V. Fandeev E. A. Fetisov S. S. Yakushov 《Technical Physics》2015,60(4):553-560
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied. 相似文献
62.
63.
Iodine(III)‐Catalyzed Rearrangements of Imides: A Versatile Route to α,α‐Dialkylated α‐Hydroxy Carboxylamides
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Anna Ulmer Dr. Maciej Stodulski Stefanie V. Kohlhepp Christoph Patzelt Dr. Alexander Pöthig Dr. Wolfgang Bettray Dr. Tanja Gulder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1444-1448
A tertiary hydroxy group α to a carboxyl moiety comprises a key structural motif in many bioactive substances. With the herein presented metal‐free rearrangement of imides triggered by hypervalent λ3‐iodane, an easy and selective way to gain access to such a compound class, namely α,α‐disubstituted‐α‐hydroxy carboxylamides, was established. Their additional methylene bromide side chain constitutes a useful handle for rapid diversification, as demonstrated by a series of further functionalizations. Moreover, the in situ formation of an iodine(III) species under the reaction conditions was proven. Our findings clearly corroborate that hypervalent λ3‐benziodoxolones are involved in these organocatalytic reactions. 相似文献
64.
65.
66.
67.
A (di)graph is supereulerian if it contains a spanning eulerian sub(di)graph. This property is a relaxation of hamiltonicity. Inspired by this analogy with hamiltonian cycles and by similar results in supereulerian graph theory, we analyze a number of sufficient Ore type conditions for a digraph to be supereulerian. Furthermore, we study the following conjecture due to Thomassé and the first author: if the arc‐connectivity of a digraph is not smaller than its independence number, then the digraph is supereulerian. As a support for this conjecture we prove it for digraphs that are semicomplete multipartite or quasitransitive and verify the analogous statement for undirected graphs. 相似文献
68.
Unexpected benzimidazole ring formation from a quinoneimide species in the presence of ammonium acetate as supporting electrolyte used in the coupling of electrochemistry with mass spectrometry
下载免费PDF全文
![点击此处可从《Rapid communications in mass spectrometry : RCM》网站下载免费的PDF全文](/ch/ext_images/free.gif)
69.
Vyacheslav V. Sentyurin Oleg A. Levitskiy Tatiana V. Magdesieva 《Current Opinion in Electrochemistry》2020
This mini-review highlights key structural features that should be taken into account when creating ambipolar redox-active closed-shell metal-free molecules. This type of compound is strongly required for the fabrication of all-organic ‘poleless’ batteries and semiconductors. The suggested strategies aimed at stabilization of both oxidized (cationic) and reduced (anionic) redox-states are based on the comprehensive analysis of the most successful structures taken from the recent publications. 相似文献
70.