全文获取类型
收费全文 | 2351篇 |
免费 | 68篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
综合类 | 5篇 |
化学工业 | 954篇 |
金属工艺 | 39篇 |
机械仪表 | 41篇 |
建筑科学 | 196篇 |
矿业工程 | 6篇 |
能源动力 | 65篇 |
轻工业 | 188篇 |
水利工程 | 13篇 |
石油天然气 | 2篇 |
武器工业 | 4篇 |
无线电 | 124篇 |
一般工业技术 | 308篇 |
冶金工业 | 124篇 |
原子能技术 | 32篇 |
自动化技术 | 299篇 |
出版年
2022年 | 22篇 |
2021年 | 52篇 |
2020年 | 29篇 |
2019年 | 27篇 |
2018年 | 34篇 |
2017年 | 25篇 |
2016年 | 63篇 |
2015年 | 56篇 |
2014年 | 54篇 |
2013年 | 103篇 |
2012年 | 89篇 |
2011年 | 120篇 |
2010年 | 99篇 |
2009年 | 101篇 |
2008年 | 96篇 |
2007年 | 82篇 |
2006年 | 89篇 |
2005年 | 80篇 |
2004年 | 63篇 |
2003年 | 44篇 |
2002年 | 51篇 |
2001年 | 45篇 |
2000年 | 51篇 |
1999年 | 63篇 |
1998年 | 52篇 |
1997年 | 56篇 |
1996年 | 52篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 28篇 |
1992年 | 40篇 |
1991年 | 40篇 |
1990年 | 31篇 |
1989年 | 40篇 |
1988年 | 26篇 |
1987年 | 31篇 |
1986年 | 29篇 |
1985年 | 23篇 |
1984年 | 30篇 |
1983年 | 27篇 |
1982年 | 17篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 19篇 |
1977年 | 22篇 |
1976年 | 18篇 |
1975年 | 18篇 |
1974年 | 21篇 |
1973年 | 19篇 |
排序方式: 共有2421条查询结果,搜索用时 16 毫秒
101.
102.
M. Masudul Hassan Marco Mueller Diana J. Tartakowska Manfred H. Wagner 《应用聚合物科学杂志》2011,120(3):1843-1849
Rice straw (Rs)/polypropylene (PP) composites were prepared in the different ratio of 5 : 95, 10 : 90, 15 : 85, 20 : 80, 25 : 75, and 30 : 70 (Rs wt % : PP wt %) by an injection molding process. This work investigated the tensile strength (TS), bending strength (BS), and impact strength (IS) of the composites. From the results, it is observed that Rs20 : PP80 mixture composite showed better performance with mechanical properties (TS = 26.2 MPa, BS = 58 N/mm2, and IS = 1.7 KJ/mm2) among the composites prepared. Two hybrid composites were also fabricated using 20% Rs, 10% seaweed with 70% PP and 20% Rs, 30% seaweed with 70% PP. In between the two hybrid composites, superior mechanical behavior showed by the hybrid composite in ratio of Rs20 : Sw10 : PP70 with enhanced results such as TS = 28 MPa, BS = 68 N/mm2, and IS = 2.5 KJ/mm2. Water uptake, simulating weathering, and soil degradation test of different composites were also performed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
103.
104.
The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) ( 1 ) reacts with YCl3 in tetrahydrofuran to give the tris-allyl complex Y(CH2CHCHSiMe3)3 ( 2 ), while K(CH2CHCHSiMe2tBu) ( 3 ) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{η2-NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) ( 5 ), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis-allyl complex {1,3-C3H3(SiMe3)2}2Sc(μ-Cl)2Li(THF)2 ( 6 ), while the analogous reaction of K{1,3-C3H3(SiMe3)2} ( 7 ) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d6 show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. 相似文献
105.
Manfred Held 《Propellants, Explosives, Pyrotechnics》2002,27(4):244-246
The momentum equation used by the author to describe the transferred momentum in the near field of detonating high explosive charges can be very well applied to the test results of steel disks at very near distances to detonating high explosive cylinders of the publication of Weaver and Walters(1). 相似文献
106.
Four double-base rocket propellants and a single-base gun propellant were tested to find out stabilizer consumption molar mass degradation, and heat generation between 50 °C and 90 °C and between 40 °C and 110 °C, respectively. Stabilizer depletion was measured by high performance liquid chromatography (HPLC), molar mass degradation by gel permeation chromatography (GPC), and heat generation by microcalorimetry. The conditioning times at different temperatures were determined with one of the rocket propellants, and the influence of the long-term storage on heat generation at 60 °C for 2191 dys was investigated. A correlated experiment between stabilizer consumption and heat generation showed that heat production does not increase substantially until the stabilizer has been consumed almost completely. The experimental data of molar mass degradation are described by a kinetic model based on statistical chain scission, and the stabilizer decrease by a first order reaction. For the gun propellant the Arrhenius plots of the reaction rate constants show two temperatures of teh stabilizer consumption, molar mass degradation and heat generation were determined. 相似文献
107.
Dr. Li Di Prof. Per Artursson Dr. Alex Avdeef Prof. Leslie Z. Benet Prof. J. Brian Houston Dr. Manfred Kansy Edward H. Kerns Prof. Hans Lennernäs Dr. Dennis A. Smith Prof. Kiyohiko Sugano 《ChemMedChem》2020,15(20):1862-1874
Passive permeability is a key property in drug disposition and delivery. It is critical for gastrointestinal absorption, brain penetration, renal reabsorption, defining clearance mechanisms and drug-drug interactions. Passive diffusion rate is translatable across tissues and animal species, while the extent of absorption is dependent on drug properties, as well as in vivo physiology/pathophysiology. Design principles have been developed to guide medicinal chemistry to enhance absorption, which combine the balance of aqueous solubility, permeability and the sometimes unfavorable compound characteristic demanded by the target. Permeability assays have been implemented that enable rapid development of structure-permeability relationships for absorption improvement. Future advances in assay development to reduce nonspecific binding and improve mass balance will enable more accurately measurement of passive permeability. Design principles that integrate potency, selectivity, passive permeability and other ADMET properties facilitate rapid advancement of successful drug candidates to patients. 相似文献
108.
Polyethylene terephthalate (PET) is one of the most common thermoplastic polymers and its durability has become a major environmental concern. The current public debate on plastic debris also triggered the revision of PET recycling technologies. This Research Article focuses on the chemical recycling of PET by means of methanolysis. The process degrades PET into two main reaction products, dimethyl terephthalate (DMT) and ethylene glycol (EG). Subsequent separation by distillation combined with crystallization removes critical impurities and non-PET components from co-polymers, providing monomers of high purity needed for re-polymerization purposes. 相似文献
109.
Solid‐Phase Gene Synthesis for Mutant Library Construction: The Future of Directed Evolution? 下载免费PDF全文
Prof. Dr. Aitao Li Prof. Dr. Zhoutong Sun Prof. Dr. Manfred T. Reetz 《Chembiochem : a European journal of chemical biology》2018,19(19):2023-2032
Directed evolution of stereo‐ and regioselective enzymes as catalysts in organic chemistry and biotechnology constitutes a complementary alternative to selective transition‐metal catalysts and organocatalysts. Saturation mutagenesis at sites lining the binding pocket has emerged as a key method in this endeavor, but it suffers from amino acid bias, which reduces the quality of the library at the DNA level and, thus, at the protein level. Chemical solid‐phase gene synthesis for library construction offers a solution to this fundamental problem, and the Sloning and Twist platforms are two possible options. This concept article analyzes these approaches and compares them to traditional PCR‐based saturation mutagenesis; the superior commercial Twist technique shows almost no bias. 相似文献
110.
Jadran Vrabec Martin Bernreuther Hans‐Joachim Bungartz Wei‐Lin Chen Wilfried Cordes Robin Fingerhut Colin W. Glass Jürgen Gmehling René Hamburger Manfred Heilig Matthias Heinen Martin T. Horsch Chieh‐Ming Hsieh Marco Hülsmann Philip Jäger Peter Klein Sandra Knauer Thorsten Köddermann Andreas Köster Kai Langenbach Shiang‐Tai Lin Philipp Neumann Jürgen Rarey Dirk Reith Gábor Rutkai Michael Schappals Martin Schenk Andre Schedemann Mandes Schönherr Steffen Seckler Simon Stephan Katrin Stöbener Nikola Tchipev Amer Wafai Stephan Werth Hans Hasse 《化学,工程师,技术》2018,90(3):295-306
This article outlines advances in molecular modeling and simulation using massively parallel high‐performance computers (HPC). In the SkaSim project, partners from the HPC community collaborated with users from science and industry. The aim was to optimize the prediction of thermodynamic property data in terms of efficiency, quality and reliability using HPC methods. In this context, various topics were dealt with: atomistic simulation of homogeneous gas bubble formation, surface tension of classical fluids and ionic liquids, multicriteria optimization of molecular models, the development of the molecular simulation codes ls1 mardyn and ms2, atomistic simulation of gas separation processes, molecular membrane structure generators, transport resistors and the evaluation of predictive property data models based on specific mixture types. 相似文献