全文获取类型
收费全文 | 2444篇 |
免费 | 51篇 |
国内免费 | 16篇 |
专业分类
化学 | 1776篇 |
晶体学 | 29篇 |
力学 | 42篇 |
数学 | 420篇 |
物理学 | 244篇 |
出版年
2022年 | 15篇 |
2021年 | 19篇 |
2020年 | 41篇 |
2019年 | 40篇 |
2018年 | 28篇 |
2017年 | 15篇 |
2016年 | 48篇 |
2015年 | 57篇 |
2014年 | 55篇 |
2013年 | 81篇 |
2012年 | 138篇 |
2011年 | 146篇 |
2010年 | 81篇 |
2009年 | 69篇 |
2008年 | 141篇 |
2007年 | 117篇 |
2006年 | 125篇 |
2005年 | 128篇 |
2004年 | 113篇 |
2003年 | 120篇 |
2002年 | 85篇 |
2001年 | 38篇 |
2000年 | 37篇 |
1999年 | 21篇 |
1998年 | 20篇 |
1997年 | 32篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 20篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 19篇 |
1988年 | 27篇 |
1987年 | 32篇 |
1986年 | 21篇 |
1985年 | 45篇 |
1984年 | 39篇 |
1983年 | 43篇 |
1982年 | 49篇 |
1981年 | 39篇 |
1980年 | 41篇 |
1979年 | 23篇 |
1978年 | 30篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 22篇 |
1974年 | 14篇 |
1973年 | 15篇 |
排序方式: 共有2511条查询结果,搜索用时 15 毫秒
991.
992.
Dr. Cher Hon Lau Dr. Xavier Mulet Dr. Kristina Konstas Dr. Cara M. Doherty Dr. Marc‐Antoine Sani Prof. Frances Separovic Dr. Matthew R. Hill Dr. Colin D. Wood 《Angewandte Chemie (International ed. in English)》2016,55(6):1998-2001
The loss of internal pores, a process known as physical aging, inhibits the long‐term use of the most promising gas‐separation polymers. Previously we reported that a porous aromatic framework (PAF‐1) could form a remarkable nanocomposite with gas‐separation polymers to stop aging. However, PAF‐1 synthesis is very onerous both from a reagent and reaction‐condition perspective, making it difficult to scale‐up. We now reveal a highly dispersible and scalable additive based on α,α′‐dichloro‐p‐xylene (p‐DCX), that inhibits aging more effectively, and crucially almost doubles gas‐transport selectivity. These synergistic effects are related to the intimately mixed nanocomposite that is formed though the high dispersibility of p‐DCX in the gas‐separation polymer. This reduces particle‐size effects and the internal free volume is almost unchanged over time. This study shows this inexpensive and scalable polymer additive delivers exceptional gas‐transport performance and selectivity. 相似文献
993.
Claire L. Hobday Ross J. Marshall Colin F. Murphie Jorge Sotelo Tom Richards David R. Allan Tina Düren Franois‐Xavier Coudert Ross S. Forgan Carole A. Morrison Stephen A. Moggach Thomas D. Bennett 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(7):2447-2451
Whilst many metal–organic frameworks possess the chemical stability needed to be used as functional materials, they often lack the physical strength required for industrial applications. Herein, we have investigated the mechanical properties of two UiO‐topology Zr‐MOFs, the planar UiO‐67 ([Zr6O4(OH)4(bpdc)6], bpdc: 4,4′‐biphenyl dicarboxylate) and UiO‐abdc ([Zr6O4(OH)4(abdc)6], abdc: 4,4′‐azobenzene dicarboxylate) by single‐crystal nanoindentation, high‐pressure X‐ray diffraction, density functional theory calculations, and first‐principles molecular dynamics. On increasing pressure, both UiO‐67 and UiO‐abdc were found to be incompressible when filled with methanol molecules within a diamond anvil cell. Stabilization in both cases is attributed to dynamical linker disorder. The diazo‐linker of UiO‐abdc possesses local site disorder, which, in conjunction with its longer nature, also decreases the capacity of the framework to compress and stabilizes it against direct compression, compared to UiO‐67, characterized by a large elastic modulus. The use of non‐linear linkers in the synthesis of UiO‐MOFs therefore creates MOFs that have more rigid mechanical properties over a larger pressure range. 相似文献
994.
995.
996.
Hydrocarbon solubility,permeability, and competitive sorption effects in polymer of intrinsic microporosity (PIM‐1) membranes
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Colin A. Scholes Jianyong Jin Geoff W. Stevens Sandra E. Kentish 《Journal of Polymer Science.Polymer Physics》2016,54(3):397-404
The sorption and permeation of pentane, hexane, and toluene through highly permeable polymer of intrinsic microporosity (PIM‐1) membranes were investigated. It was established that the hydrocarbons sorbed strongly within the micro‐void regions of the PIM‐1 membrane. The sorption concentration was similar for the paraffins, pentane and hexane, but greater for aromatic toluene at high vapor activities. The magnitude of the hydrocarbon permeability was associated with the critical temperature of the hydrocarbon. The PIM‐1 membrane displayed selectivity for the three hydrocarbons over CO2. As a consequence, the presence of the three hydrocarbons dramatically reduced the permeability of CO2 and N2 under mixed gas–vapor conditions to 68%–95% below the dry gas value. For all three hydrocarbons the N2 permeability was more strongly impacted than CO2 permeability, and hence the ideal CO2/N2 selectivity of PIM‐1 increased. It was determined that CO2 and N2 solubility decreased because of hydrocarbon competitive sorption while CO2 and N2 diffusivity also decreased because of anti‐plasticization, which was due to the presence of hydrocarbon clusters within the membrane structure. There was a clear correlation between the magnitude of anti‐plasticization and the critical temperature of the hydrocarbon. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 397–404 相似文献
997.
The crystallographic community is in many ways an exemplar of the benefits and practices of sharing data. Since the inception of the technique, virtually every published crystal structure has been made available to others. This has been achieved through the establishment of several specialist data centres, including the Cambridge Crystallographic Data Centre, which produces the Cambridge Structural Database. Containing curated structures of small organic molecules, some containing a metal, the database has been produced for almost 50 years. This has required the development of complex informatics tools and an environment allowing expert human curation. As importantly, a financial model has evolved which has, to date, ensured the sustainability of the resource. However, the opportunities afforded by technological changes and changing attitudes to sharing data make it an opportune moment to review current practices. 相似文献
998.
Isabelle Sordat-Diserens Andrew Marston Matthias Hamburger Kurt Hostettmann Colin Rogers 《Helvetica chimica acta》1989,72(5):1001-1007
Three novel prenylated xanthones, 1–3 , have been isolated from the root bark of Garcinia gerrardii HARVEY ex T. R. SIM (G. natalensis SCHLECHTER ; G. transvaalensis BURTT DAVY ; Guttiferae). Structure elucidation was achieved by a combination of one- and two-dimensional NMR spectroscopic techniques, including long-range HETCOR, mass spectroscopy, and chemical methods. Garcigerrin A ( 1 ) and B ( 2 ) are pyrano derivatives of 3 . They all show a rare 1,4,5 oxygenation pattern of the xanthone nucleus. Xanthone 3 is fungicidal against Cladosporium cucumerinum. 相似文献
999.
Co-oligomerisations of F-but-2-yne (1) with F-propene, -2-butene, and -cyclopentene have been investigated and some interesting cyclic products have been identified. 相似文献
1000.
Vladimir Diakiw James S. Shannon Michael J. Lacey Colin G. MacDonald 《Journal of mass spectrometry : JMS》1979,14(1):58-58
Skeletal rearrangements are reported of protonated molecular ions in the chemical ionization mass spectra of allyl cyclohexyl ether, benzyl cyclohexyl ether, t-butyl cyclohexyl ether and dibenzyl ether. 相似文献