全文获取类型
收费全文 | 2116篇 |
免费 | 75篇 |
国内免费 | 26篇 |
专业分类
化学 | 1232篇 |
晶体学 | 9篇 |
力学 | 59篇 |
数学 | 388篇 |
物理学 | 529篇 |
出版年
2021年 | 21篇 |
2020年 | 27篇 |
2019年 | 25篇 |
2018年 | 16篇 |
2017年 | 22篇 |
2016年 | 57篇 |
2015年 | 46篇 |
2014年 | 51篇 |
2013年 | 83篇 |
2012年 | 127篇 |
2011年 | 154篇 |
2010年 | 73篇 |
2009年 | 68篇 |
2008年 | 107篇 |
2007年 | 119篇 |
2006年 | 137篇 |
2005年 | 135篇 |
2004年 | 83篇 |
2003年 | 92篇 |
2002年 | 94篇 |
2001年 | 34篇 |
2000年 | 35篇 |
1999年 | 21篇 |
1998年 | 28篇 |
1997年 | 24篇 |
1996年 | 22篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 26篇 |
1992年 | 27篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 25篇 |
1982年 | 20篇 |
1981年 | 25篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 21篇 |
1977年 | 16篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1966年 | 8篇 |
排序方式: 共有2217条查询结果,搜索用时 15 毫秒
81.
82.
83.
Rubber covered cylinders in rolling contact are studied in two cases; rolling over a flat surface and rolling over a groove. In the first case, two different finite element procedures are compared for the purpose of investigating if computational savings can be made when taking amplitude dependent effects into account by using a modified viscoelastic steady state rolling procedure. This procedure is compared with using a more expensive overlay method with an elastoplastic-viscoelastic material model. The two procedures and material models are shown two give equal results in the flat surface case. For the case of rolling over a groove, it is shown how the non-linear dynamic material characteristics of the rubber layer influence the rolling contact. The groove filling capacity of the rubber is shown to be strongly dependent on the material model. It is shown that amplitude dependent rubber materials have better ability to fill out contact surface irregularities such as a groove. 相似文献
84.
Modification of σ‐Donor Properties of Terminal Carbide Ligands Investigated Through Carbide–Iodine Adduct Formation 下载免费PDF全文
Anders Reinholdt Prof. Dr. Tom Vosch Prof. Dr. Jesper Bendix 《Angewandte Chemie (International ed. in English)》2016,55(40):12484-12487
The terminal carbide ligands in [(Cy3P)2X2Ru≡C] complexes (X=halide or pseudohalide) coordinate molecular iodine, affording charge‐transfer complexes rather than oxidation products. Crystallographic and vibrational spectroscopic data show the perturbations of iodine to vary with the auxiliary ligand sphere on ruthenium, demonstrating the σ‐donor properties of carbide complexes to be tunable. 相似文献
85.
Jon E. Carlé Martin Helgesen Natalia K. Zawacka Morten V. Madsen Eva Bundgaard Frederik C. Krebs 《Journal of Polymer Science.Polymer Physics》2014,52(13):893-899
Two low‐band gap polymer series based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and dithienylbenzothiadiazole, with different numbers of fluorine substituents on the 2,3,1‐benzothiadiazole unit, have been synthesized and explored in a comparative study of the photochemical stability and operational lifetime in flexible large area roll‐coated bulk heterojunction solar cells. The two polymer series have different side chains on the BDT unit, namely 2‐hexyldecyloxy (BDTHDO) ( P1–P3 ) or 2‐hexyldecylthiophene (BDTTHD) ( P4–P6 ). The photochemical stability clearly shows that the stability enhances along with the number of fluorine atoms incorporated on the polymer backbone. Fabrication of the polymer solar cells based on the materials was carried out in ambient atmosphere on a roll coating/printing machine employing flexible and indium‐tin‐oxide‐free plastic substrates. Solar cells based on the P4–P6 series showed the best performance, reaching efficiencies up to 3.8% for an active area of 1 cm2, due to an enhanced current compared to P1–P3 . Lifetime measurements, carried out according to international summit on OPV stability (ISOS), of encapsulated devices reveals an initial fast decay for P1–P6 in the performance followed by a much slower decay rate, still retaining 40–55% of their initial performance after 250 h of testing under ISOS‐L‐1 conditions. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 893–899 相似文献
86.
87.
88.
Dr. Karin Mannerstedt Dr. Narendra Kumar Mishra Dr. Ebbe Engholm Dr. Morten Lundh Dr. Charlotte S. Madsen Dr. Philip J. Pedersen Dr. Priska Le-Huu Dr. Søren L. Pedersen Dr. Nina Buch-Månson Dr. Björn Borgström Dr. Thomas Brimert Dr. Lisbeth N. Fink Dr. Keld Fosgerau Prof. Niels Vrang Prof. Knud J. Jensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(9):3166-3176
A glucose responsive insulin (GRI) that responds to changes in blood glucose concentrations has remained an elusive goal. Here we describe the development of glucose cleavable linkers based on hydrazone and thiazolidine structures. We developed linkers with low levels of spontaneous hydrolysis but increased level of hydrolysis with rising concentrations of glucose, which demonstrated their glucose responsiveness in vitro. Lipidated hydrazones and thiazolidines were conjugated to the LysB29 side-chain of HI by pH-controlled acylations providing GRIs with glucose responsiveness confirmed in vitro for thiazolidines. Clamp studies showed increased glucose infusion at hyperglycemic conditions for one GRI indicative of a true glucose response. The glucose responsive cleavable linker in these GRIs allow changes in glucose levels to drive the release of active insulin from a circulating depot. We have demonstrated an unprecedented, chemically responsive linker concept for biopharmaceuticals. 相似文献
89.