全文获取类型
收费全文 | 335670篇 |
免费 | 4386篇 |
国内免费 | 1006篇 |
专业分类
化学 | 177253篇 |
晶体学 | 5155篇 |
力学 | 14189篇 |
综合类 | 10篇 |
数学 | 39069篇 |
物理学 | 105386篇 |
出版年
2020年 | 2751篇 |
2019年 | 2802篇 |
2018年 | 3593篇 |
2017年 | 3430篇 |
2016年 | 5668篇 |
2015年 | 3870篇 |
2014年 | 5528篇 |
2013年 | 14844篇 |
2012年 | 11298篇 |
2011年 | 13833篇 |
2010年 | 9092篇 |
2009年 | 8668篇 |
2008年 | 12580篇 |
2007年 | 12689篇 |
2006年 | 12193篇 |
2005年 | 11117篇 |
2004年 | 10068篇 |
2003年 | 8901篇 |
2002年 | 8656篇 |
2001年 | 9545篇 |
2000年 | 7509篇 |
1999年 | 5854篇 |
1998年 | 4838篇 |
1997年 | 4824篇 |
1996年 | 4670篇 |
1995年 | 4418篇 |
1994年 | 4096篇 |
1993年 | 4068篇 |
1992年 | 4477篇 |
1991年 | 4295篇 |
1990年 | 4220篇 |
1989年 | 3995篇 |
1988年 | 4076篇 |
1987年 | 4060篇 |
1986年 | 3781篇 |
1985年 | 5107篇 |
1984年 | 5381篇 |
1983年 | 4503篇 |
1982年 | 4887篇 |
1981年 | 4716篇 |
1980年 | 4606篇 |
1979年 | 4669篇 |
1978年 | 4889篇 |
1977年 | 4812篇 |
1976年 | 4882篇 |
1975年 | 4585篇 |
1974年 | 4442篇 |
1973年 | 4745篇 |
1972年 | 2954篇 |
1971年 | 2302篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
72.
73.
74.
75.
Cover Picture: Coordination Chemistry of N‐Heterocyclic Nitrenium‐Based Ligands (Chem. Eur. J. 19/2015)
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)
76.
Ajeel Raheem K. Salim W. S.-I. W. 《Journal of Thermal Analysis and Calorimetry》2021,144(4):1161-1173
Journal of Thermal Analysis and Calorimetry - Over the last few decades, tremendous consideration is drawn towards corrugation surfaces because of their advantages over the improvement in thermal... 相似文献
77.
78.
Mathematical Notes - We study the multiplicity of weak solutions to the boundary-value problem $$\begin{alignedat}{2} - M\biggl(\iint_{\mathbb R^{2N}}|u(x)-u(y)|^2 K(x-y)\,d x\,d y\biggr)\mathscr... 相似文献
79.
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
80.
Optics and Spectroscopy - A cell with a submicron thickness was used to measure the broadening and shift of the D1 and D2 lines of Rb atoms by neon. The resolution of hypefine components... 相似文献