全文获取类型
收费全文 | 334815篇 |
免费 | 3211篇 |
国内免费 | 728篇 |
专业分类
电工技术 | 5510篇 |
综合类 | 250篇 |
化学工业 | 51688篇 |
金属工艺 | 16795篇 |
机械仪表 | 11143篇 |
建筑科学 | 6576篇 |
矿业工程 | 3459篇 |
能源动力 | 6993篇 |
轻工业 | 20317篇 |
水利工程 | 5040篇 |
石油天然气 | 13319篇 |
武器工业 | 31篇 |
无线电 | 32882篇 |
一般工业技术 | 74160篇 |
冶金工业 | 56639篇 |
原子能技术 | 11122篇 |
自动化技术 | 22830篇 |
出版年
2021年 | 3181篇 |
2019年 | 3096篇 |
2018年 | 5701篇 |
2017年 | 5807篇 |
2016年 | 6285篇 |
2015年 | 3454篇 |
2014年 | 5942篇 |
2013年 | 13735篇 |
2012年 | 8926篇 |
2011年 | 11366篇 |
2010年 | 9221篇 |
2009年 | 10291篇 |
2008年 | 10404篇 |
2007年 | 10317篇 |
2006年 | 8862篇 |
2005年 | 8096篇 |
2004年 | 7518篇 |
2003年 | 7358篇 |
2002年 | 7089篇 |
2001年 | 7214篇 |
2000年 | 6856篇 |
1999年 | 6820篇 |
1998年 | 16228篇 |
1997年 | 11581篇 |
1996年 | 8730篇 |
1995年 | 6618篇 |
1994年 | 5800篇 |
1993年 | 6076篇 |
1992年 | 4746篇 |
1991年 | 4697篇 |
1990年 | 4663篇 |
1989年 | 4543篇 |
1988年 | 4552篇 |
1987年 | 4094篇 |
1986年 | 4190篇 |
1985年 | 4491篇 |
1984年 | 4279篇 |
1983年 | 4092篇 |
1982年 | 3725篇 |
1981年 | 3898篇 |
1980年 | 3813篇 |
1979年 | 4009篇 |
1978年 | 4115篇 |
1977年 | 4269篇 |
1976年 | 5251篇 |
1975年 | 3771篇 |
1974年 | 3722篇 |
1973年 | 3820篇 |
1972年 | 3469篇 |
1971年 | 3129篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
121.
S. V. Yakubovskaya L. V. Kul'bitskaya N. L. Budeiko A. A. Korbit 《Inorganic Materials》2004,40(3):221-226
The effect of the composition of sensitizing–activating solutions on the activation efficiency and the chemical coppering of diamond powders is studied. The results demonstrate that stabilizing additives improve the stability of the solutions, influence the average coppering rate, and play a key role in determining the morphology and quality of the resultant coatings. The most effective stabilizing additive is synthamid-10, which ensures the deposition of high-quality copper coatings. 相似文献
122.
The operation of a torsional oscillator for detection, of flow-driven textural transitions in, 3He-A is described. The detection technique, tracking the shift of the resonant frequency of the torsional oscillator, allows us to observe textural changes and the presence of vortices in zero magnetic field. It relies on. the anisotropic superfluid density of 3He-A and its change due to reorientation of the Î-texture caused by counterflow. 相似文献
123.
V. N. Perevezentsev M. Yu. Shcherban’ M. Yu. Murashkin R. Z. Valiev 《Technical Physics Letters》2007,33(8):648-650
The structure and mechanical properties of nanocrystalline aluminum alloy 1570 obtained by means of severe plastic deformation have been studied. Being tested in a temperature range from 300 to 400°C, the alloy exhibits high-strain-rate superplasticity. At 400°C, the superplasticity is manifested in a very broad range of strain rates, extending from 5 × 10?3 to 1 s?1. 相似文献
124.
125.
The biochemical composition can be seen as a good indicator of both the biodegradability and the methane potential of a given waste. The work presented here is an attempt to elaborate a typology of wastes and to compare it to the anaerobic degradation characteristics. The first data indicate that there is a link between the ligno-cellulosic content of the waste and the biodegradability. When dealing with application to anaerobic digestion processes, having a tool to predict the ability of the waste to be degraded could be of the greatest interest for preventing failures, estimating biogas production, methane content, or for the management of co-digestion processes. 相似文献
126.
A combination of concept (the product portfolio and the product life cycle) and empirical research (the PIMS study) can aid in clarifying the key issues involved in the selection of a firm's core strategies. Strategy control is multistage: periodic re-evaluation of strategy alternatives by use of the marketing audit; an analytical framework for control of chosen strategies by breaking down components and reporting their performance variances; and 'marketing segment' analysis for control of the detailed marketing plan.? 相似文献
127.
V. I. Gorynin 《Strength of Materials》1991,23(5):524-527
The influence of the level of defectiveness of design and service origin (grooves and cracks) of a fastener and an impact specimen on the accuracy of determination of the allowable values of the ductile-to-brittle transition temperature is investigated. An evaluation of the allowable ductile-to-brittle transition temperatures making it possible to impose more soundly based requirements for effectiveness of the material in the stages of design, production, and service in relation to the production condition of the steel, the level of defectiveness of the fastener, and the specified operating life of the threaded joint is proposed.Translated from Problemy Prochnosti, No. 5, pp. 35–37, May, 1991. 相似文献
128.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals. 相似文献
129.
The optical properties of bismuth telluride crystals doped with donor-and acceptor-type impurities are studied. The fact that energy corresponding to the resonance frequency of plasma oscillations of free charge carriers (plasmons) approaches the band-gap energy is detected in the infrared spectral region, where the main elementary excitations in the electronic system of these materials are observed. The mentioned approach of energies varies the intensity of electron-plasmon interaction, which affects the recombination processes in the materials widely used for the fabrication of thermoelectric energy converters. 相似文献
130.