全文获取类型
收费全文 | 3362篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 45篇 |
综合类 | 1篇 |
化学工业 | 351篇 |
金属工艺 | 71篇 |
机械仪表 | 112篇 |
建筑科学 | 148篇 |
矿业工程 | 5篇 |
能源动力 | 62篇 |
轻工业 | 145篇 |
水利工程 | 15篇 |
石油天然气 | 12篇 |
无线电 | 306篇 |
一般工业技术 | 444篇 |
冶金工业 | 1448篇 |
原子能技术 | 21篇 |
自动化技术 | 212篇 |
出版年
2019年 | 16篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 20篇 |
2014年 | 26篇 |
2013年 | 85篇 |
2012年 | 35篇 |
2011年 | 69篇 |
2010年 | 51篇 |
2009年 | 61篇 |
2008年 | 65篇 |
2007年 | 73篇 |
2006年 | 63篇 |
2005年 | 74篇 |
2004年 | 49篇 |
2003年 | 51篇 |
2002年 | 69篇 |
2001年 | 50篇 |
2000年 | 57篇 |
1999年 | 99篇 |
1998年 | 472篇 |
1997年 | 273篇 |
1996年 | 202篇 |
1995年 | 128篇 |
1994年 | 113篇 |
1993年 | 121篇 |
1992年 | 40篇 |
1991年 | 45篇 |
1990年 | 36篇 |
1989年 | 48篇 |
1988年 | 54篇 |
1987年 | 51篇 |
1986年 | 50篇 |
1985年 | 40篇 |
1984年 | 37篇 |
1983年 | 31篇 |
1982年 | 32篇 |
1981年 | 34篇 |
1980年 | 42篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 57篇 |
1976年 | 96篇 |
1975年 | 34篇 |
1974年 | 28篇 |
1973年 | 34篇 |
1972年 | 23篇 |
1971年 | 18篇 |
1970年 | 20篇 |
排序方式: 共有3398条查询结果,搜索用时 15 毫秒
91.
Dr. Travis Coyle Dr. Liang Wu Dr. Aleksandra W. Debowski Prof. Gideon J. Davies Dr. Keith A. Stubbs 《Chembiochem : a European journal of chemical biology》2019,20(11):1365-1368
The sugar fucose plays a myriad of roles in biological recognition. Enzymes hydrolyzing fucose from glycoconjugates, α-l -fucosidases, are important targets for inhibitor and probe development. Here we describe the synthesis and evaluation of novel α-l -fucosidase inhibitors, with X-ray crystallographic analysis using an α-l -fucosidase from Bacteroides thetaiotamicron helping to lay a foundation for future development of inhibitors for this important enzyme class. 相似文献
92.
O. L. Davies 《技术计量学》2013,55(1):49-61
In establishing an economical testing program the costs of routine analytical tests must be weighed against losses due to shipping material which is either above or below stated specifications. A method for obtaining an optimum sampling and testing procedure is described and examples given. 相似文献
93.
Juan M. Jiménez Varesh Prasad Michael D. Yu Christopher P. Kampmeyer Abdul-Hadi Kaakour Pei-Jiang Wang Sean F. Maloney Nathan Wright Ian Johnston Yi-Zhou Jiang Peter F. Davies 《Journal of the Royal Society Interface》2014,11(94)
Drug eluting stents are associated with late stent thrombosis (LST), delayed healing and prolonged exposure of stent struts to blood flow. Using macroscale disturbed and undisturbed fluid flow waveforms, we numerically and experimentally determined the effects of microscale model strut geometries upon the generation of prothrombotic conditions that are mediated by flow perturbations. Rectangular cross-sectional stent strut geometries of varying heights and corresponding streamlined versions were studied in the presence of disturbed and undisturbed bulk fluid flow. Numerical simulations and particle flow visualization experiments demonstrated that the interaction of bulk fluid flow and stent struts regulated the generation, size and dynamics of the peristrut flow recirculation zones. In the absence of endothelial cells, deposition of thrombin-generated fibrin occurred primarily in the recirculation zones. When endothelium was present, peristrut expression of anticoagulant thrombomodulin (TM) was dependent on strut height and geometry. Thinner and streamlined strut geometries reduced peristrut flow recirculation zones decreasing prothrombotic fibrin deposition and increasing endothelial anticoagulant TM expression. The studies define physical and functional consequences of macro- and microscale variables that relate to thrombogenicity associated with the most current stent designs, and particularly to LST. 相似文献
94.
Nicholas T. Kirkland Mark P. Staiger David Nisbet Chris H.J. Davies Nick Birbilis 《JOM Journal of the Minerals, Metals and Materials Society》2011,63(6):28-34
Magnesium (Mg) and its alloys provide numerous benefits as a resorptive biomaterial and present the very real possibility
of replacing current metallic implant materials in a variety of roles. The development of suitable biodegradable implant alloys
is a multidisciplinary challenge, since alloy design must be confined to a range of alloying additions that are biologically
nontoxic, whilst still providing the requisite mechanical properties. This leaves a small number of compatible elements that
can provide benefits when alloyed with Mg, including calcium (Ca) and zinc (Zn). To date, although a range of different Mg
alloys have been investigated both in vitro and in vivo, little work has been performed to characterize the relationship between
the composition of Mg alloys, their corrosion and resulting mechanical properties over time. Consequently it is crucial to
understand how these properties may be related if alloys are to be successfully screened for implantation in the body. 相似文献
95.
The use of glass fibre reinforced polyester composites raises many health and safety and environmental questions. One alternative is the development of high performance bio-based bio-composites with low environmental impact. Improved understanding of interfacial properties is essential to optimise the mechanical properties and durability of these materials, but so far few data are available. The present work describes the interfacial characterization of Flax fibre/Poly(lactic) acid (PLLA) system at the micro-scale using the microbond test. Different thermal treatments have been carried out (cooling rate and annealing) in order to evaluate the influence of matrix and interfacial morphologies as well as residual stress on interfacial properties. Micromechanical models have been used to determine the interfacial shear strength. When cooling rate is slow, improved interfacial properties are observed. 相似文献
96.
Low Loss,High NA Chalcogenide Glass Fibers for Broadband Mid‐Infrared Supercontinuum Generation 下载免费PDF全文
Bin Zhang Wei Guo Yi Yu Chengcheng Zhai Sisheng Qi Anping Yang Lei Li Zhiyong Yang Rongping Wang Dingyuan Tang Guangming Tao Barry Luther‐Davies 《Journal of the American Ceramic Society》2015,98(5):1389-1392
High‐purity Ge–As–Se and Ge–As–S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step‐index fibers with a small core (~5.5 μm) and large numerical aperture (~1.3) were fabricated. When a 13.5‐cm‐long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 μm, supercontinuum spanning from ~1.8 to ~9.8 μm with a dynamic range of ±10 dB and an average power of ~3 mW was generated. 相似文献
97.
Information and communication technology (ICT) is becoming increasingly important in construction although the rate of adoption is considered slow and the industry faces specific implementation challenges. Mainstream information systems research has shown that individuals’ beliefs and expectations of the consequences of ICT use predict subsequent usage. We describe the development of scales to measure beliefs about the consequences of building information modelling (BIM) and their use in a survey of employees of a large construction contracting organization in the United Kingdom. Scales for performance expectancy, effort expectancy, social influence, facilitating conditions, compatibility, and attitude toward using technology were adapted from existing measures. In an analysis of responses from 762 construction employees the scales showed acceptable measurement properties. Expectations about the consequences of BIM use were broadly favourable although there is a need for more data for comparisons. The structure of the responses showed that expectations that BIM would enhance job performance were strongly related to expectations that BIM use was compatible with preferred and existing ways of working. Results also suggest that social influence is complex and may be multidimensional. 相似文献
98.
High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber 下载免费PDF全文
Bin Zhang Yi Yu Chengcheng Zhai Sisheng Qi Yuwei Wang Anping Yang Xin Gai Rongping Wang Zhiyong Yang Barry Luther‐Davies 《Journal of the American Ceramic Society》2016,99(8):2565-2568
An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy. 相似文献
99.
Bare, cylindrical, explosive charges produce secondary shock waves in the direction of least presented area. Whilst the source of these shock waves was explored in the 1940’s, no attempt was made to predict them. This paper describes the detonation of bare, cylindrical charges of PE4 (RDX binder 88/12 %), mass 0.2 to 0.46 kg and with a length to diameter ratio of 4 to 1. High speed camera footage showed (i) the formation of the separate, primary, shock waves from the sides and ends of the charge, (ii) Mach reflection of these separate shock waves, giving rise to reflected, secondary shock waves, and (iii) the secondary shock waves catching and merging with the primary shock wave. In the axial direction, the secondary shock wave’s peak overpressure and impulse exceeded that of the primary shock wave for scaled distances, Z=R/M1/3 ≥3.9 m kg−1/3, where M is the mass in kg and R the distance from the charge in m. It was found possible to predict the primary peak overpressure, P, at all distances in the axial direction, for a constant length to diameter ratio, using P=3075 Z−3−1732 Z−2+305 Z−1. Close in the primary peak overpressure is proportional to M/R3 in the axial direction. It was not possible to predict the secondary peak overpressure with the data obtained. The total impulse from both shock waves, I, in the axial direction can be predicted using I=746(M2/3/R)3−708(M2/3/R)2+306(M2/3/R). 相似文献
100.
Pierre Yves Le Gac Morgane Broudin Gérard Roux Jacques Verdu Peter Davies Bruno Fayolle 《Polymer》2014
Tensile properties and crack propagation properties, especially critical strain energy release rate in mode I, GIC, have been used to investigate fracture properties of elastomers and their relationships with microstructure. These investigations were mainly based on a series of comparisons: first, the behaviour of polychloroprene rubber (CR), undergoing stress hardening due to strain induced crystallization (SIC) and oxidative crosslinking (OCL) was compared with that of chlorinated polyethylene (CPE), which undergoes SIC but not OCL, and with a polyurethane based on hydroxyl terminated polybutadiene (PU) which undergoes OCL but not SIC. Comparisons were also made on CR between fracture behaviour at ambient temperature, where SIC occurs and at 100 °C where there is no SIC. Finally, oxidative crosslinking was used to vary in a continuous way the crosslink density in CR and PU, in order to evaluate the role of crosslinking in fracture behaviour. 相似文献