全文获取类型
收费全文 | 250183篇 |
免费 | 3038篇 |
国内免费 | 897篇 |
专业分类
化学 | 128905篇 |
晶体学 | 4092篇 |
力学 | 11142篇 |
综合类 | 1篇 |
数学 | 28294篇 |
物理学 | 81684篇 |
出版年
2020年 | 2142篇 |
2019年 | 2417篇 |
2018年 | 2940篇 |
2017年 | 2875篇 |
2016年 | 4475篇 |
2015年 | 2899篇 |
2014年 | 4563篇 |
2013年 | 11038篇 |
2012年 | 8577篇 |
2011年 | 10551篇 |
2010年 | 7369篇 |
2009年 | 7233篇 |
2008年 | 9657篇 |
2007年 | 9669篇 |
2006年 | 9129篇 |
2005年 | 8299篇 |
2004年 | 7610篇 |
2003年 | 6694篇 |
2002年 | 6610篇 |
2001年 | 7364篇 |
2000年 | 5634篇 |
1999年 | 4480篇 |
1998年 | 3790篇 |
1997年 | 3684篇 |
1996年 | 3539篇 |
1995年 | 3242篇 |
1994年 | 3158篇 |
1993年 | 3243篇 |
1992年 | 3334篇 |
1991年 | 3487篇 |
1990年 | 3248篇 |
1989年 | 3181篇 |
1988年 | 3204篇 |
1987年 | 3068篇 |
1986年 | 2907篇 |
1985年 | 3959篇 |
1984年 | 4141篇 |
1983年 | 3307篇 |
1982年 | 3546篇 |
1981年 | 3473篇 |
1980年 | 3349篇 |
1979年 | 3455篇 |
1978年 | 3565篇 |
1977年 | 3458篇 |
1976年 | 3537篇 |
1975年 | 3245篇 |
1974年 | 3225篇 |
1973年 | 3260篇 |
1972年 | 2286篇 |
1971年 | 1892篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse. 相似文献
52.
Algebras and Representation Theory - We introduce and study the category of twisted modules over a triangular differential graded bocs. We show that in this category idempotents split, that it... 相似文献
53.
Annals of Operations Research - The vehicle routing problem is a traditional combinatorial problem with practical relevance for a wide range of industries. In the literature, several specificities... 相似文献
54.
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust... 相似文献
55.
Kozetozhets I. V. Panasyuk G. P. Semenov E. A. Buzanov G. A. Avdeeva V. V. Danchevskaya M. N. Tsvetov N. S. Shapovalov S. S. Vasilev M. G. 《Russian Journal of General Chemistry》2022,91(1):S98-S105
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an... 相似文献
56.
Gary W. Breton Lauren A. Hahn Kenneth L. Martin 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(9):1208-1212
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided. 相似文献
57.
Avramenko Andriy A. Shevchuk Igor V. Dmitrenko Nataliia P. Skitsko Ivan F. 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12709-12719
Journal of Thermal Analysis and Calorimetry - The paper focuses on the analytical analysis of the propagation of a normal shock wave in an adiabatic gas flow with nanoparticles. A modified... 相似文献
58.
Mathematical Notes - 相似文献
59.
Back Cover: Reactions of Group 4 Metallocenes with Monosubstituted Acetonitriles: Keteniminate Formation versus CC Coupling (Chem. Eur. J. 8/2015) 下载免费PDF全文
60.
E. V. Shadrina O. N. Malinkina T. G. Khonina A. B. Shipovskaya V. I. Fomina E. Yu. Larchenko N. A. Popova I. G. Zyryanova L. P. Larionov 《Russian Chemical Bulletin》2015,64(7):1633-1639
The biomimetic sol—gel synthesis of silicon—chitosan-containing glycerohydrogels was carried out using silicon tetraglycerolate as a precursor. It was found that chitosan accelerates gel formation in weakly acidic media. In more acidic media, the kinetics of the process changes according to the curve with a maximum, which can be attributed to different mechanisms of silanol condensation before and after the isoelectric point. The investigated silicon—chitosan-containing glycerohydrogels exhibit antibacterial, anti-inflammatory, and wound healing activity. The synthesized hybrid glycerohydrogels are promising materials for biomedical applications. 相似文献