全文获取类型
收费全文 | 350647篇 |
免费 | 2687篇 |
国内免费 | 420篇 |
专业分类
电工技术 | 5618篇 |
综合类 | 193篇 |
化学工业 | 55796篇 |
金属工艺 | 19796篇 |
机械仪表 | 12929篇 |
建筑科学 | 6380篇 |
矿业工程 | 4489篇 |
能源动力 | 6172篇 |
轻工业 | 17213篇 |
水利工程 | 5687篇 |
石油天然气 | 16551篇 |
武器工业 | 31篇 |
无线电 | 30198篇 |
一般工业技术 | 83514篇 |
冶金工业 | 51393篇 |
原子能技术 | 13618篇 |
自动化技术 | 24176篇 |
出版年
2021年 | 3526篇 |
2019年 | 3467篇 |
2018年 | 6756篇 |
2017年 | 6982篇 |
2016年 | 7450篇 |
2015年 | 3890篇 |
2014年 | 6829篇 |
2013年 | 14279篇 |
2012年 | 9743篇 |
2011年 | 12190篇 |
2010年 | 9955篇 |
2009年 | 11032篇 |
2008年 | 11169篇 |
2007年 | 10847篇 |
2006年 | 9048篇 |
2005年 | 8052篇 |
2004年 | 7824篇 |
2003年 | 7603篇 |
2002年 | 7399篇 |
2001年 | 7276篇 |
2000年 | 7092篇 |
1999年 | 6555篇 |
1998年 | 13029篇 |
1997年 | 9985篇 |
1996年 | 7465篇 |
1995年 | 5912篇 |
1994年 | 5394篇 |
1993年 | 5593篇 |
1992年 | 4643篇 |
1991年 | 4736篇 |
1990年 | 4862篇 |
1989年 | 4672篇 |
1988年 | 4560篇 |
1987年 | 4433篇 |
1986年 | 4362篇 |
1985年 | 4564篇 |
1984年 | 4408篇 |
1983年 | 4292篇 |
1982年 | 4020篇 |
1981年 | 4211篇 |
1980年 | 4142篇 |
1979年 | 4426篇 |
1978年 | 4735篇 |
1977年 | 4800篇 |
1976年 | 5758篇 |
1975年 | 4340篇 |
1974年 | 4390篇 |
1973年 | 4467篇 |
1972年 | 4054篇 |
1971年 | 3689篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The Magnitogorsk Metallurgical Combine has conducted a study of the effect of technological factors on the hydrogen content
of chromium-nickel-molybdenum steel after vacuum degassing. It was established that the most important factor is the hydrogen
content of the steel before the degassing operation. The study also determined the effects of the circulation coefficient,
the duration of the degassing operation, and the vacuum used in the treatment.
__________
Translated from Metallurg, No. 7, pp. 68–69, July, 2006. 相似文献
12.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended. 相似文献
13.
Yu. I. Golovin D. V. Lopatin R. K. Nikolaev A. V. Umrikhin 《Technical Physics Letters》2004,30(5):426-428
The effect of crystal orientation on the photogeneration of free charge carriers was studied for C60 single crystals in a weak magnetic field. The photoconductivity sharply depends on the orientation of magnetic field with
respect to the crystallographic directions, showing a 5–8% increase for seven axes of the C60 crystal. 相似文献
14.
Korolev I. A. Alekseenko N. N. Porodnov B. T. Sapunov V. A. Savel'ev D. V. 《Measurement Techniques》2003,46(9):865-871
The design of a sylphon bellows sensor and the basic circuits of an LC-generator and of a microprocessor unit are presented. An analytical pressure–frequency conversion function and a special method of adjusting the sensor ensure an error of less than 0.05%. The dynamic range is up to 105. The instruments developed cover the ranges 103, 104, and 105 Pa. 相似文献
15.
The application of barrier discharges at atmospheric pressure in air expands on the market of plasma technology, because it is an ecological and cost‐effective alternative to other processes of surface treatment. These plasmas usually consist of a multitude of spatially and temporally localized filaments, whose distribution should be as even as possible for homogeneous treatment. This holds especially for the plasma treatment of sensitive goods such as wool or other textiles. In equipment for continuous pass of material the barrier arrangements often consist of a system cylinder – cylinder or cylinder – plane, whereby the gap width changes locally. Space distribution and intensity of filaments has been investigated by means of short‐time photography and spatially resolved measurement of current distribution and energy distribution derived from it. The local dependency found can be explained by means of a capacitive equivalent circuit. 相似文献
16.
17.
Quasi-static stress fields for a crack inclined to the property gradation in functionally graded materials 总被引:3,自引:0,他引:3
Summary. Quasi-static stress fields for a crack inclined to the direction of property gradation in functionally graded materials (FGMs)
are obtained through an asymptotic analysis coupled with Westergaard's stress function approach. The elastic modulus of the
FGM is assumed to vary exponentially along the gradation direction. The mode mixity due to the inclination of the property
gradient is accommodated in the analysis through superposition of opening and shear modes. The first four terms in the expansion
of the stress field are derived to explicitly bring out the influence of nonhomogeneity on the structure of the stress field.
Using these stress field contours of constant maximum shear stress, constant maximum principal stress, constant first stress
invariant and constant out of plane displacement are generated, and the effect of inclination of the property gradation direction
on these contours is discussed.
Received September 22, 2002
Published online: May 20, 2003
The financial support of National Science Foundation (NSF) under grant no. CMS 99000138 is gratefully acknowledged. 相似文献
18.
V. N. Tsygankov V. V. Safonov A. I. Kozlov V. P. Gavrilov 《Inorganic Materials》2003,39(10):1076-1078
The GeO2–NiO system is studied in the stability range of Ni2GeO4 by temperature-dependent resistivity measurements, in combination with x-ray diffraction, differential thermal analysis, and thermogravimetry. The resistivity of the starting mixtures and heat-treated samples is measured in the composition range 55–90 mol % NiO. The effect of air humidity on the resistivity of the samples is examined. 相似文献
19.
The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture. 相似文献
20.
Thomy V. Dubois L. Vanoverschelde C. Sozanski J.P. Pribetich J. 《IEEE sensors journal》2004,4(6):772-778
This paper describes a novel planar antenna sensor created for the purpose of noninvasive temperature measurements using microwave radiometry. In order to improve radiometric measurements in industrial applications, a new generation of sensors is introduced, composed of a metallic sheet. Simulations based upon the method of moments is used both to design and to determine their electromagnetic performances. This paper also describes a radiometric device using these sensors to measure and control the temperature of food products during deep freezing processes. The results and discussions are presented. 相似文献