全文获取类型
收费全文 | 2475篇 |
免费 | 57篇 |
国内免费 | 9篇 |
专业分类
化学 | 1582篇 |
晶体学 | 14篇 |
力学 | 39篇 |
数学 | 423篇 |
物理学 | 483篇 |
出版年
2021年 | 36篇 |
2020年 | 27篇 |
2019年 | 24篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 50篇 |
2015年 | 31篇 |
2014年 | 37篇 |
2013年 | 137篇 |
2012年 | 112篇 |
2011年 | 123篇 |
2010年 | 75篇 |
2009年 | 56篇 |
2008年 | 106篇 |
2007年 | 107篇 |
2006年 | 116篇 |
2005年 | 130篇 |
2004年 | 98篇 |
2003年 | 85篇 |
2002年 | 81篇 |
2001年 | 34篇 |
2000年 | 29篇 |
1999年 | 23篇 |
1998年 | 25篇 |
1997年 | 26篇 |
1996年 | 34篇 |
1995年 | 37篇 |
1994年 | 30篇 |
1993年 | 30篇 |
1992年 | 35篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 25篇 |
1988年 | 29篇 |
1986年 | 23篇 |
1985年 | 56篇 |
1984年 | 49篇 |
1983年 | 36篇 |
1982年 | 49篇 |
1981年 | 46篇 |
1980年 | 53篇 |
1979年 | 33篇 |
1978年 | 41篇 |
1977年 | 39篇 |
1976年 | 29篇 |
1975年 | 30篇 |
1974年 | 28篇 |
1973年 | 26篇 |
1972年 | 16篇 |
1969年 | 14篇 |
排序方式: 共有2541条查询结果,搜索用时 958 毫秒
121.
Mark P. Waller Thomas Dresselhaus Jack Yang 《Journal of computational chemistry》2013,34(16):1420-1428
Here, we present just a collection of beans (JACOB): an integrated batch‐based framework designed for the rapid development of computational chemistry applications. The framework expedites developer productivity by handling the generic infrastructure tier, and can be easily extended by user‐specific scientific code. Paradigms from enterprise software engineering were rigorously applied to create a scalable, testable, secure, and robust framework. A centralized web application is used to configure and control the operation of the framework. The application‐programming interface provides a set of generic tools for processing large‐scale noninteractive jobs (e.g., systematic studies), or for coordinating systems integration (e.g., complex workflows). The code for the JACOB framework is open sourced and is available at: www.wallerlab.org/jacob . © 2013 Wiley Periodicals, Inc. 相似文献
122.
123.
124.
Abstract It is shown that the McMillan parameter M = T SAN/T N1 (where T SAN and T NI are respectively the temperatures of the smectic A to nematic (SAN) and the nematic to isotropic (NI) phase transitions) is useful in analysing the crossover between second and first order behaviour of the SNN transition in the nO.m homologous liquid crystal series (the 4-n-alkoxybenzylidene-4′-n-alkylanilines). Using a phase diagram of orientational ordering versus M for this series, as obtained in this work (from E.S.R. and D.S.C), a symmetric tricritical point with mean field exponent β2 = 1 is demonstrated. In a preliminary study of E.S.R. linewidth parameters B and C of nitroxide spin probes dissolved in members of the nO.m series exhibiting a first order SAN transition, critical-type divergences are observed near this transition. In the case where M is closer to 0.959 (the value at the tricritical point), these divergences appear similar to those previously observed in related nO.m members with a second order SAN transition; however, they are considerably enhanced for an M value closer to unity (i.e. more removed from the tricritical point). This indicates the importance of coupling between orientational and positional order parameters in the observed critical-type divergences. 相似文献
125.
126.
Charles E. Carraher Jr. Van R. Foster H. Michael Molloy Michael L. Taylor Thomas O. Tiernan Jack A. Schroeder 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1):231-241
The synthesis of polymers derived from the condensation of dipyridine manganese II dichloride with 1,3-di-4-piperidylpro-pane is described. Structural analysis of the polyamines is detailed utilizing results based on infrared, thermal, elemental and solution analyses. 相似文献
127.
128.
129.
Exploring Regioselective Bond Cleavage and Cross‐Coupling Reactions using a Low‐Valent Nickel Complex 下载免费PDF全文
Addison N. Desnoyer Florian W. Friese Weiling Chiu Marcus W. Drover Dr. Brian O. Patrick Prof. Dr. Jennifer A. Love 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(12):4070-4077
Recently, esters have received much attention as transmetalation partners for cross‐coupling reactions. Herein, we report a systematic study of the reactivity of a series of esters and thioesters with [{(dtbpe)Ni}2(μ‐η2:η2‐C6H6)] (dtbpe=1,2‐bis(di‐tert‐butyl)phosphinoethane), which is a source of (dtbpe)nickel(0). Trifluoromethylthioesters were found to form η2‐carbonyl complexes. In contrast, acetylthioesters underwent rapid Cacyl?S bond cleavage followed by decarbonylation to generate methylnickel complexes. This decarbonylation could be pushed backwards by the addition of CO, allowing for regeneration of the thioester. Most of the thioester complexes were found to undergo stoichiometric cross‐coupling with phenylboronic acid to yield sulfides. While ethyl trifluoroacetate was also found to form an η2‐carbonyl complex, phenyl esters were found to predominantly undergo Caryl?O bond cleavage to yield arylnickel complexes. These could also undergo transmetalation to yield biaryls. Attempts to render the reactions catalytic were hindered by ligand scrambling to yield nickel bis(acetate) complexes, the formation of which was supported by independent syntheses. Finally, 2‐naphthyl acetate was also found to undergo clean Caryl?O bond cleavage, and although stoichiometric cross‐coupling with phenylboronic acid proceeded with good yield, catalytic turnover has so far proven elusive. 相似文献
130.