全文获取类型
收费全文 | 5881篇 |
免费 | 141篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 182篇 |
综合类 | 9篇 |
化学工业 | 1443篇 |
金属工艺 | 144篇 |
机械仪表 | 121篇 |
建筑科学 | 337篇 |
矿业工程 | 22篇 |
能源动力 | 138篇 |
轻工业 | 649篇 |
水利工程 | 63篇 |
石油天然气 | 8篇 |
无线电 | 401篇 |
一般工业技术 | 771篇 |
冶金工业 | 1068篇 |
原子能技术 | 80篇 |
自动化技术 | 595篇 |
出版年
2021年 | 81篇 |
2020年 | 57篇 |
2019年 | 68篇 |
2018年 | 58篇 |
2017年 | 72篇 |
2016年 | 98篇 |
2015年 | 77篇 |
2014年 | 124篇 |
2013年 | 238篇 |
2012年 | 175篇 |
2011年 | 267篇 |
2010年 | 168篇 |
2009年 | 180篇 |
2008年 | 212篇 |
2007年 | 186篇 |
2006年 | 184篇 |
2005年 | 157篇 |
2004年 | 148篇 |
2003年 | 119篇 |
2002年 | 133篇 |
2001年 | 87篇 |
2000年 | 98篇 |
1999年 | 107篇 |
1998年 | 192篇 |
1997年 | 156篇 |
1996年 | 116篇 |
1995年 | 114篇 |
1994年 | 100篇 |
1993年 | 91篇 |
1992年 | 74篇 |
1991年 | 69篇 |
1990年 | 79篇 |
1989年 | 79篇 |
1988年 | 68篇 |
1987年 | 69篇 |
1986年 | 65篇 |
1985年 | 88篇 |
1984年 | 76篇 |
1983年 | 88篇 |
1982年 | 75篇 |
1981年 | 66篇 |
1980年 | 63篇 |
1979年 | 63篇 |
1978年 | 69篇 |
1977年 | 81篇 |
1976年 | 94篇 |
1975年 | 60篇 |
1974年 | 66篇 |
1973年 | 64篇 |
1972年 | 52篇 |
排序方式: 共有6031条查询结果,搜索用时 31 毫秒
101.
Oligobutadiene-based prepolymers and polyurethanes (PU) were prepared from hydroxyl terminated polybutadiene (HTPB), three diisocyanates (aromatic, alicyclic and aliphatic) and two chain extenders (containing hydroxyl or amino groups). The free NCO content in the prepolymers varied systematically and the characteristic of these products were interpreted in terms of NCO group reactivity, propagation reactions and HTPB functionality. The mechanical properties of the polyurethane elastomers derived from the prepolymers were discussed in terms of hard and soft segment structures. 相似文献
102.
Nuclear magnetic resonance spectroscopy has been used to study the dissociation and reaction of N,N′-(2-propyloximino)-4,4′-methylenebis(phenylcarbamate), as a crosslinking agent for polymers containing labile hydrogens. The crosslinking of poly(acrylic acid), polyacrylamide, and poly(vinyl alcohol) was found to result upon heating each to 150°C for 10 min with this component at 2–10 wt %. 相似文献
103.
Walter J. Thomas Mohamed A. El-Sawy Edward W. Palmer 《Chemical Engineering Communications》1982,16(1):53-78
Two published theoretical models are examined and applied to experimental results for absorption and desorption. The system used was CO2/H2O and studies were made for liquid film flow down inclined planes. Experimental results give “Reduced” values of mass ransfer rates.
Interferometric studies give interfacial concentration, penetration and film depths, and take-up of carbon dioxide. In the case of desorption the interferograms are distorted by “deflections.”
All the experimental values for absorption and desorption differ from those calculated from theoretical models.
Desorption is not a mirror image of absorption, and it is approximately 75% of the transfer rate of absorption over a wide operating range.
A comparison is made of the behaviour of static pools and flowing liquid films. 相似文献
Interferometric studies give interfacial concentration, penetration and film depths, and take-up of carbon dioxide. In the case of desorption the interferograms are distorted by “deflections.”
All the experimental values for absorption and desorption differ from those calculated from theoretical models.
Desorption is not a mirror image of absorption, and it is approximately 75% of the transfer rate of absorption over a wide operating range.
A comparison is made of the behaviour of static pools and flowing liquid films. 相似文献
104.
105.
Electrochemical dressing of fine-grained metal-bonded diamond grinding wheels enables to grind hard and brittle materials
in the ductile mode. Optical surfaces can be manufactured by grinding, which reduces the need for subsequent, time-consuming
polishing work. When using metal-bonded grinding wheels, the emerging oxides regulate the electrochemical dissolution. Bronze-bonded
grinding wheels are more suitable for grinding cemented carbides and ceramics than iron-bonded grinding wheels, as it is easier
to modify their chemical composition to suit a specific grinding task. They can also be sintered at lower temperatures, which
reduces the risk of thermal damage to the diamond. In this paper, the dissolution and the oxidation of different bronze alloys
are characterized for the electrochemical dressing process. The relevant evaluation criteria are the oxide layer thickness,
the electrical behavior and the different emerging bronze alloy oxides.
This work is funded by the German Research Association DFG within the Transregional Collaborative Research Center SFB/TR4
“Process Chains for the Replication of Complex Optical Elements”. 相似文献
106.
We present a model of spatial navigation based on the non-convergent dynamics of brain activity. The system includes a hippocampal module that processes global spatial information and a cortical module that deals with local sensory information. We test the model using several spatial navigation paradigms: goal finding, shortcutting and detouring. Computer simulations show that the performance of the agent qualitatively matches that of animals and related models. This new approach provides a novel interpretation of how the brain accomplishes spatial navigation. 相似文献
107.
108.
109.
110.
Barton B Rhinow D Walter A Schröder R Benner G Majorovits E Matijevic M Niebel H Müller H Haider M Lacher M Schmitz S Holik P Kühlbrandt W 《Ultramicroscopy》2011,111(12):1696-1705
We report the implementation of an electrostatic Einzel lens (Boersch) phase plate in a prototype transmission electron microscope dedicated to aberration-corrected cryo-EM. The combination of phase plate, Cs corrector and Diffraction Magnification Unit (DMU) as a new electron-optical element ensures minimal information loss due to obstruction by the phase plate and enables in-focus phase contrast imaging of large macromolecular assemblies. As no defocussing is necessary and the spherical aberration is corrected, maximal, non-oscillating phase contrast transfer can be achieved up to the information limit of the instrument. A microchip produced by a scalable micro-fabrication process has 10 phase plates, which are positioned in a conjugate, magnified diffraction plane generated by the DMU. Phase plates remained fully functional for weeks or months. The large distance between phase plate and the cryo sample permits the use of an effective anti-contaminator, resulting in ice contamination rates of <0.6 nm/h at the specimen. Maximal in-focus phase contrast was obtained by applying voltages between 80 and 700 mV to the phase plate electrode. The phase plate allows for in-focus imaging of biological objects with a signal-to-noise of 5-10 at a resolution of 2-3 nm, as demonstrated for frozen-hydrated virus particles and purple membrane at liquid-nitrogen temperature. 相似文献