全文获取类型
收费全文 | 1172篇 |
免费 | 52篇 |
专业分类
化学 | 1013篇 |
晶体学 | 11篇 |
力学 | 7篇 |
数学 | 64篇 |
物理学 | 129篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 8篇 |
2021年 | 109篇 |
2020年 | 35篇 |
2019年 | 31篇 |
2018年 | 38篇 |
2017年 | 35篇 |
2016年 | 78篇 |
2015年 | 45篇 |
2014年 | 56篇 |
2013年 | 98篇 |
2012年 | 82篇 |
2011年 | 96篇 |
2010年 | 69篇 |
2009年 | 50篇 |
2008年 | 72篇 |
2007年 | 70篇 |
2006年 | 41篇 |
2005年 | 48篇 |
2004年 | 36篇 |
2003年 | 26篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
排序方式: 共有1224条查询结果,搜索用时 500 毫秒
31.
A simple optical method for quantitative comparison of the effectiveness of epoxy cure accelerators, used for speeding up the crosslinking process of epoxy resins with cyclic anhydrides, is described. Fluorescent molecular probes and a miniature fiber optic spectrometer have been applied for measurement of the cure kinetics of a model epoxy resin/anhydride composition in the presence of various cure accelerators. A quantitative index of accelerator performance has been determined for several of the most common accelerators. 相似文献
32.
Stanisław Leśniak Adam M. Pieczonka Szymon Jarzyński Katarzyna Justyna Michał Rachwalski 《Tetrahedron: Asymmetry》2013,24(20):1341-1344
A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%. 相似文献
33.
Nikola Toljic Kaz Adamiak G.S. Peter Castle Hong-Hsiang Kuo Hua-Tzu Fan 《Journal of Electrostatics》2012,70(6):499-504
In this paper, a full three dimensional FLUENT numerical model of the electrostatic coating process with the embedded moving mesh capability and piecewise linear type target motion is presented. The model includes target geometries that do not exhibit symmetry. All the dominant mechanical and electrical phenomena are taken into account. Mechanical phenomena include shaping air effects, downdraft effects and the motion of the polydispersed particles. Electrical phenomena include the particle space charge distribution, corona discharge and the electrohydrodynamic flow effects. It was demonstrated that the numerical model can accurately mimic the type of the motion used in real world applications. 相似文献
34.
When exposed to a corona discharge, a dielectric droplet spreads over a grounded substrate. In the present work, the spreading of dielectric liquids subjected to a short-term exposure is investigated. A simple theoretical model was developed to find the spreading law at the very beginning of exposure. The asymptotic approximation for the surface charge density and the interfacial pressure showed that the droplet spreading immediately after the exposure obeys t1/2 law. The high speed imaging of the spreading revealed the same trend as predicted by the theoretical model. 相似文献
35.
36.
Related to his S-glued sum construction, the skeleton S(L) of a finite lattice L was introduced by C. Herrmann in 1973. Our theorem asserts that if D is a finite distributive lattice and its second skeleton, S(S(D)), is the trivial lattice, then D is characterized by its weighted double skeleton, introduced by the second author in 2006. The assumption on the second skeleton is essential. 相似文献
37.
38.
39.
Prof. Juliusz Pernak Michał Niemczak Prof. Łukasz Chrzanowski Łukasz Ławniczak Przemysław Fochtman Katarzyna Marcinkowska Prof. Tadeusz Praczyk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(34):12012-12021
This study focused on the synthesis and subsequent characterization of herbicidal ionic liquids based on betaine and carnitine, two derivatives of amino acids, which were used as cations. Four commonly used herbicides (2,4‐D, MCPA, MCPP and Dicamba) were used as anions in simple (single anion) and oligomeric (two anions) salts. The obtained salts were subjected to analyzes regarding physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles and solubility) as well as evaluation of their herbicidal activity under greenhouse and field conditions, toxicity towards rats and biodegradability. The obtained results suggest that the synthesized herbicidal ionic liquids displayed low toxicity (classified as category 4 compounds) and showed similar or improved efficacy against weed compared to reference herbicides. The highest increase was observed during field trials for salts containing 2,4‐D as the anion, which also exhibited the highest biodegradability (>75 %). 相似文献
40.
Katarzyna Skrzypek Milou Groot Nibbelink Jolanda Liefers‐Visser Alexandra M. Smink Eleftheria Stoimenou Marten A. Engelse Eelco J. P. de Koning Marcel Karperien Paul de Vos Aart van Apeldoorn Dimitrios Stamatialis 《Macromolecular bioscience》2020,20(8)
Macroencapsulation of islets of Langerhans is a promising strategy for transplantation of insulin‐producing cells in the absence of immunosuppression to treat type 1 diabetes. Hollow fiber membranes are of interest there because they offer a large surface‐to‐volume ratio and can potentially be retrieved or refilled. However, current available fibers have limitations in exchange of nutrients, oxygen, and delivery of insulin potentially impacting graft survival. Here, multibore hollow fibers for islets encapsulation are designed and tested. They consist of seven bores and are prepared using nondegradable polymers with high mechanical stability and low cell adhesion properties. Human islets encapsulated there have a glucose induced insulin response (GIIS) similar to nonencapsulated islets. During 7 d of cell culture in vitro, the GIIS increases with graded doses of islets demonstrating the suitability of the microenvironment for islet survival. Moreover, first implantation studies in mice demonstrate device material biocompatibility with minimal tissue responses. Besides, formation of new blood vessels close to the implanted device is observed, an important requirement for maintaining islet viability and fast exchange of glucose and insulin. The results indicate that the developed fibers have high islet bearing capacity and can potentially be applied for a clinically applicable bioartificial pancreas. 相似文献