全文获取类型
收费全文 | 280746篇 |
免费 | 4255篇 |
国内免费 | 1327篇 |
专业分类
电工技术 | 5374篇 |
技术理论 | 3篇 |
综合类 | 1554篇 |
化学工业 | 46542篇 |
金属工艺 | 16589篇 |
机械仪表 | 11869篇 |
建筑科学 | 6294篇 |
矿业工程 | 4713篇 |
能源动力 | 4834篇 |
轻工业 | 13086篇 |
水利工程 | 4617篇 |
石油天然气 | 14508篇 |
武器工业 | 186篇 |
无线电 | 23263篇 |
一般工业技术 | 67213篇 |
冶金工业 | 33790篇 |
原子能技术 | 11383篇 |
自动化技术 | 20510篇 |
出版年
2021年 | 4039篇 |
2020年 | 3152篇 |
2019年 | 3632篇 |
2018年 | 6487篇 |
2017年 | 6835篇 |
2016年 | 7199篇 |
2015年 | 4322篇 |
2014年 | 6981篇 |
2013年 | 12418篇 |
2012年 | 9571篇 |
2011年 | 11086篇 |
2010年 | 9140篇 |
2009年 | 9811篇 |
2008年 | 9908篇 |
2007年 | 9464篇 |
2006年 | 7896篇 |
2005年 | 6841篇 |
2004年 | 6409篇 |
2003年 | 6147篇 |
2002年 | 6007篇 |
2001年 | 5629篇 |
2000年 | 5569篇 |
1999年 | 4913篇 |
1998年 | 7713篇 |
1997年 | 6298篇 |
1996年 | 4843篇 |
1995年 | 4022篇 |
1994年 | 3769篇 |
1993年 | 3882篇 |
1992年 | 3408篇 |
1991年 | 3501篇 |
1990年 | 3559篇 |
1989年 | 3453篇 |
1988年 | 3356篇 |
1987年 | 3313篇 |
1986年 | 3204篇 |
1985年 | 3352篇 |
1984年 | 3281篇 |
1983年 | 3167篇 |
1982年 | 3018篇 |
1981年 | 3065篇 |
1980年 | 3089篇 |
1979年 | 3282篇 |
1978年 | 3500篇 |
1977年 | 3469篇 |
1976年 | 3920篇 |
1975年 | 3217篇 |
1974年 | 3302篇 |
1973年 | 3352篇 |
1972年 | 2990篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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
12.
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
13.
声波测井换能器的激发响应由换能器振动时所表现出来的动态阻抗和激发电路参数决定。而换能器的动态(阻抗)参数随压电晶体及其装配方式(力学边界条件)改变。为了测量换能器动态参数的影响,采用声波测井仪器常用的压电晶体和升压变压器,通过改变激发脉冲宽度和直流电压进行了实验,结果发现:在换能器两端的瞬态响应中,一共有三个二阶网络响应,分别对应于不同的频率。最低的一个影响声波测井波形的基线、与换能器主频接近的一个决定激发效率以及电路与压电晶体之间的匹配关系,是激发电路设计中比较关键的,其参数可以通过导纳圆测量仪器得到。 相似文献
14.
The problem of synthesis of an isotropic reradiator providing for the transparency of a circular perfectly conducting cylinder illuminated by a TE-polarized plane wave is investigated. A general solution to the problem of diffraction from the cylinder with a reradiator is obtained, and a system of nonlinear equations for the synthesis problem is derived. Numerical solution of the synthesis problem is illustrated by a number of examples. 相似文献
15.
V. N. Durcheva S. M. Puchkova 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):71-78
Operation of the dam in a transitional mode is described.
__________
Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, January 2006, pp. 8–15. 相似文献
16.
V. O. Yablonskii 《Chemical and Petroleum Engineering》2006,42(11-12):611-617
A mathematical model for separation of suspensions with a non-Newtonian disperse medium by dual-stage pressurized flotation in a cylindrical-conical hydrocyclone is developed. A system of differential equations of the convective diffusion and movement of a complex of particles-bubbles is solved by a numerical method. The concentration field is modeled, and integral separation indicators are determined. Values of structural parameters of the hydrocyclone for which the separation indicators depend heavily on the taper angle of the conical section of the housing and the rheological properties of the disperse medium are established. It is demonstrated that dual-stage pressurized flotation makes it possible to reduce considerably the residual concentration of solid-phase particles as compared with single-stage flotation. 相似文献
17.
网络安全事件的关联分析方法的比较研究 总被引:2,自引:0,他引:2
随着当前攻击手段和技术的日益复杂化,一次入侵事件往往需要多个步骤才能完成,这些步骤都是彼此相关的。但是传统的入侵检测集中于检测底层的入侵或异常,所检测到的结果也仅仅是一次完整入侵的一部分,所以不能将不同的报警结合起来以发现入侵的逻辑步骤或者入侵背后的攻击策略。关联分析技术将不同分析器上产生的报警进行融合与关联分析,极大地减少了报警的数量,降低了入侵检测的误报率,并且适当的减少了入侵检测的漏报率。文中在对网络安全事件关联分析方法的系统结构进行分析后,着重介绍了当前比较流行的几种网络安全事件关联分析方法,最后对各种方法进行了比较研究。 相似文献
18.
19.
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
20.