全文获取类型
收费全文 | 27276篇 |
免费 | 883篇 |
国内免费 | 369篇 |
专业分类
化学 | 19243篇 |
晶体学 | 167篇 |
力学 | 611篇 |
综合类 | 30篇 |
数学 | 3565篇 |
物理学 | 4912篇 |
出版年
2023年 | 150篇 |
2022年 | 142篇 |
2021年 | 677篇 |
2020年 | 459篇 |
2019年 | 519篇 |
2018年 | 421篇 |
2017年 | 354篇 |
2016年 | 761篇 |
2015年 | 733篇 |
2014年 | 788篇 |
2013年 | 1617篇 |
2012年 | 1481篇 |
2011年 | 1690篇 |
2010年 | 1116篇 |
2009年 | 1077篇 |
2008年 | 1476篇 |
2007年 | 1500篇 |
2006年 | 1251篇 |
2005年 | 1206篇 |
2004年 | 1103篇 |
2003年 | 1029篇 |
2002年 | 1044篇 |
2001年 | 605篇 |
2000年 | 531篇 |
1999年 | 415篇 |
1998年 | 339篇 |
1997年 | 304篇 |
1996年 | 296篇 |
1995年 | 308篇 |
1994年 | 296篇 |
1993年 | 244篇 |
1992年 | 224篇 |
1991年 | 246篇 |
1990年 | 236篇 |
1989年 | 222篇 |
1988年 | 192篇 |
1987年 | 182篇 |
1986年 | 176篇 |
1985年 | 275篇 |
1984年 | 305篇 |
1983年 | 196篇 |
1982年 | 243篇 |
1981年 | 201篇 |
1980年 | 203篇 |
1979年 | 178篇 |
1978年 | 167篇 |
1977年 | 199篇 |
1976年 | 174篇 |
1975年 | 140篇 |
1973年 | 128篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Reza Kordnezhadian Bing-Yu Li Armir Zogu Dr. Joachim Demaerel Prof. Dr. Wim M. De Borggraeve Dr. Ermal Ismalaj 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(60):e202201491
Pentafluorosulfanyl (SF5)-containing compounds and corresponding analogs are a highly valuable class of fluorine-containing building blocks owing to their unique properties. The reason for that is the set of peculiar and tremendously beneficial characteristics they can impart on molecules once introduced onto them. Despite this, their application in distinct scientific fields remains modest, given the extremely harsh reaction conditions needed to access such compounds. The recent synthetic approaches via S−F, and C−SF5 bond formation as well as the use of SF5-containing building blocks embody a “stairway-to-heaven” loophole in the synthesis of otherwise-inaccessible chemical scaffolds only a few years ago. Herein, we report and evaluate the properties of the SF5 group and analogs, by summarizing synthetic methodologies available to access them as well as following applications in material science and medicinal chemistry since 2015. 相似文献
3.
Journal of Fourier Analysis and Applications - We develop a theory of Sobolev orthogonal polynomials on the Sierpiński gasket ( $$SG$$ ), which is a fractal set that can be viewed as a limit... 相似文献
4.
5.
6.
Synthesis of Highly Substituted γ‐Butyrolactones by a Gold‐Catalyzed Cascade Reaction of Benzyl Esters 下载免费PDF全文
Maria Camila Blanco Jaimes Alexander Ahrens Daniel Pflästerer Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):427-433
Easily accessible benzylic esters of 3‐butynoic acids in a gold‐catalyzed cyclization/rearrangement cascade reaction provided 3‐propargyl γ‐butyrolactones with the alkene and the carbonyl group not being conjugated. Crossover experiments showed that the formation of the new C?C bond is an intermolecular process. Initially propargylic–benzylic esters were used, but alkyl‐substituted benzylic esters worked equally well. In the case of the propargylic–benzylic products, a simple treatment of the products with aluminum oxide initiated a twofold tautomerization to the allenyl‐substituted γ‐butyrolactones with conjugation of the carbonyl group, the olefin, and the allene. The synthetic sequence can be conducted stepwise or as a one‐pot cascade reaction with similar yields. Even in the presence of the gold catalyst the new allene remains intact. 相似文献
7.
8.
9.
The Effect of the Spacer of Bis(biurea) Ligands on the Structure of A2L3‐type (A=anion) Phosphate Complexes 下载免费PDF全文
Prof. Biao Wu Dr. Shaoguang Li Prof. Yibo Lei Prof. Huaiming Hu Dr. Nader de Sousa Amadeu Prof. Dr. Christoph Janiak Dr. Jennifer S. Mathieson Dr. De‐Liang Long Prof. Leroy Cronin Prof. Xiao‐Juan Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2588-2593
By tuning the length and rigidity of the spacer of bis(biurea) ligands L, three structural motifs of the A2L3 complexes (A represents anion, here orthophosphate PO43?), namely helicate, mesocate, and mono‐bridged motif, have been assembled by coordination of the ligand to phosphate anion. Crystal structure analysis indicated that in the three complexes, each of the phosphate ions is coordinated by twelve hydrogen bonds from six surrounding urea groups. The anion coordination properties in solution have also been studied. The results further demonstrate the coordination behavior of phosphate ion, which shows strong tendency for coordination saturation and geometrical preference, thus allowing for the assembly of novel anion coordination‐based structures as in transition‐metal complexes. 相似文献
10.