全文获取类型
收费全文 | 4631篇 |
免费 | 160篇 |
国内免费 | 31篇 |
专业分类
化学 | 2906篇 |
晶体学 | 22篇 |
力学 | 109篇 |
数学 | 671篇 |
物理学 | 1114篇 |
出版年
2023年 | 36篇 |
2022年 | 35篇 |
2021年 | 76篇 |
2020年 | 94篇 |
2019年 | 112篇 |
2018年 | 68篇 |
2017年 | 79篇 |
2016年 | 144篇 |
2015年 | 85篇 |
2014年 | 116篇 |
2013年 | 237篇 |
2012年 | 263篇 |
2011年 | 310篇 |
2010年 | 167篇 |
2009年 | 111篇 |
2008年 | 225篇 |
2007年 | 277篇 |
2006年 | 244篇 |
2005年 | 232篇 |
2004年 | 178篇 |
2003年 | 152篇 |
2002年 | 92篇 |
2001年 | 75篇 |
2000年 | 69篇 |
1999年 | 42篇 |
1998年 | 34篇 |
1997年 | 61篇 |
1996年 | 48篇 |
1995年 | 57篇 |
1994年 | 51篇 |
1993年 | 56篇 |
1992年 | 60篇 |
1991年 | 41篇 |
1990年 | 42篇 |
1989年 | 33篇 |
1988年 | 36篇 |
1987年 | 28篇 |
1985年 | 51篇 |
1984年 | 40篇 |
1982年 | 35篇 |
1981年 | 50篇 |
1980年 | 34篇 |
1979年 | 44篇 |
1978年 | 42篇 |
1977年 | 40篇 |
1976年 | 44篇 |
1975年 | 34篇 |
1974年 | 31篇 |
1973年 | 43篇 |
1972年 | 31篇 |
排序方式: 共有4822条查询结果,搜索用时 31 毫秒
101.
102.
Markus Bursch Lukas Kunze Dr. Amol M. Vibhute Dr. Andreas Hansen Prof. Dr. Kana M. Sureshan Dr. Peter G. Jones Prof. Dr. Stefan Grimme Prof. Dr. Daniel B. Werz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(14):4627-4639
The noncovalent interactions between azides and oxygen-containing moieties are investigated through a computational study based on experimental findings. The targeted synthesis of organic compounds with close intramolecular azide–oxygen contacts yielded six new representatives, for which X-ray structures were determined. Two of those compounds were investigated with respect to their potential conformations in the gas phase and a possible significantly shorter azide–oxygen contact. Furthermore, a set of 44 high-quality, gas-phase computational model systems with intermolecular azide–pnictogen (N, P, As, Sb), –chalcogen (O, S, Se, Te), and –halogen (F, Cl, Br, I) contacts are compiled and investigated through semiempirical quantum mechanical methods, density functional approximations, and wave function theory. A local energy decomposition (LED) analysis is applied to study the nature of the noncovalent interaction. The special role of electrostatic and London dispersion interactions is discussed in detail. London dispersion is identified as a dominant factor of the azide–donor interaction with mean London dispersion energy-interaction energy ratios of 1.3. Electrostatic contributions enhance the azide–donor coordination motif. The association energies range from −1.00 to −5.5 kcal mol−1. 相似文献
103.
104.
Alexandru Vlasceanu Dr. Søren L. Broman Anne S. Hansen Anders B. Skov Prof. Dr. Martina Cacciarini Prof. Dr. Anders Kadziola Prof. Dr. Henrik G. Kjaergaard Prof. Dr. Kurt V. Mikkelsen Prof. Dr. Mogens Brøndsted Nielsen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(31):10796-10800
The conversion and efficient storage of solar energy is recognized to hold significant potential with regard to future energy solutions. Molecular solar thermal batteries based on photochromic systems exemplify one possible technology able to harness and apply this potential. Herein is described the synthesis of a macrocycle based on a dimer of the dihydroazulene/vinylheptafulvene (DHA/VHF) photo/thermal couple. By taking advantage of conformational strain, this DHA–DHA macrocycle presents an improved ability to absorb and store incident light energy in chemical bonds (VHF–VHF). A stepwise energy release over two sequential ring‐closing reactions (VHF→DHA) combines the advantages of an initially fast discharge, hypothetically addressing immediate energy consumption needs, followed by a slow process for consistent, long‐term use. This exemplifies another step forward in the molecular engineering and design of functional organic materials towards solar thermal energy storage and release. 相似文献
105.
106.
107.
Anaí Duarte Wilson Cunico Claudio M.P. Pereira Alex F.C. Flores Rogério A. Freitag Geonir M. Siqueira 《Ultrasonics sonochemistry》2010,17(2):281-283
An ultrasound-enhanced method has been developed for the synthesis of a variety of thioesters from benzoyl chlorides and 2-mercaptobenzoxa(thia)zoles. Applying this methodology, 14 compounds were synthesized in excellent yields. 相似文献
108.
Kevin D. Altria Nigel R. Barker Mairwen Hayworth Alex D. Henderson 《Chromatographia》2011,74(11-12):783-787
Two independent and orthogonal analytical methods are required when performing identity testing of pharmaceutical products during routine release testing. A microemulsion electrokinetic chromatography method has been developed and validated for routine use as an identity test to release various pharmaceutical products including tablets, capsules and creams. Implementation of the method involved optimisation of parameters to achieve reliable routine operation. Rinsing procedures, in particular, were found to be essential to obtain consistent profiles and migration times. The method has replaced, and offers the potential to replace, a number of methods including HPLC and IR due to the considerable cost and time savings obtained through its use. This method has been successfully approved by the US FDA as a part of 2 New Drug Applications, is registered in Japan, and is in routine QA use within a factory environment. 相似文献
109.
Alex S Powlesland Maria Marcela Barrio José Mordoh Paul G Hitchen Anne Dell Kurt Drickamer Maureen E Taylor 《BMC biochemistry》2011,12(1):13
Background
The Lewisx trisaccharide, also referred to as the CD15 antigen, is a diagnostic marker used to distinguish Hodgkin's lymphoma from other lymphocytic cancers. However, the role of such fucosylated structures remains poorly understood, in part because carriers of Lewisx structures on Hodgkin's Reed-Sternberg cells have not been identified. 相似文献110.
Laura Sinatra Jan J. Bandolik Dr. Martin Roatsch Melf Sönnichsen Dr. Clara T. Schoeder Dr. Alexandra Hamacher Andrea Schöler Prof. Dr. Arndt Borkhardt Prof. Dr. Jens Meiler Dr. Sanil Bhatia Prof. Dr. Matthias U. Kassack Prof. Dr. Finn K. Hansen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(50):22681-22687