全文获取类型
收费全文 | 385133篇 |
免费 | 13447篇 |
国内免费 | 6334篇 |
专业分类
电工技术 | 12202篇 |
技术理论 | 9篇 |
综合类 | 8805篇 |
化学工业 | 62883篇 |
金属工艺 | 22790篇 |
机械仪表 | 18460篇 |
建筑科学 | 13639篇 |
矿业工程 | 7289篇 |
能源动力 | 7392篇 |
轻工业 | 18972篇 |
水利工程 | 6806篇 |
石油天然气 | 20283篇 |
武器工业 | 1073篇 |
无线电 | 35349篇 |
一般工业技术 | 81465篇 |
冶金工业 | 39373篇 |
原子能技术 | 13510篇 |
自动化技术 | 34614篇 |
出版年
2022年 | 6275篇 |
2021年 | 8517篇 |
2020年 | 6486篇 |
2019年 | 6279篇 |
2018年 | 9554篇 |
2017年 | 10271篇 |
2016年 | 10091篇 |
2015年 | 8202篇 |
2014年 | 11753篇 |
2013年 | 17835篇 |
2012年 | 15809篇 |
2011年 | 17968篇 |
2010年 | 14973篇 |
2009年 | 15597篇 |
2008年 | 15603篇 |
2007年 | 14743篇 |
2006年 | 12959篇 |
2005年 | 11219篇 |
2004年 | 9638篇 |
2003年 | 9386篇 |
2002年 | 9353篇 |
2001年 | 8740篇 |
2000年 | 8140篇 |
1999年 | 7151篇 |
1998年 | 9436篇 |
1997年 | 7674篇 |
1996年 | 6110篇 |
1995年 | 5123篇 |
1994年 | 4647篇 |
1993年 | 4537篇 |
1992年 | 4070篇 |
1991年 | 4039篇 |
1990年 | 4096篇 |
1989年 | 3937篇 |
1988年 | 3741篇 |
1987年 | 3681篇 |
1986年 | 3500篇 |
1985年 | 3617篇 |
1984年 | 3516篇 |
1983年 | 3409篇 |
1981年 | 3303篇 |
1980年 | 3336篇 |
1979年 | 3565篇 |
1978年 | 3783篇 |
1977年 | 3772篇 |
1976年 | 4225篇 |
1975年 | 3521篇 |
1974年 | 3591篇 |
1973年 | 3613篇 |
1972年 | 3305篇 |
排序方式: 共有10000条查询结果,搜索用时 0 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.
Xue‐Yong Liu Xiao‐Bin Ding Zhao‐Hui Zheng Yu‐Xing Peng Albert S
C Chan C
W Yip Xin‐Ping Long 《Polymer International》2003,52(2):235-240
Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe3O4 magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g?1. © 2003 Society of Chemical Industry 相似文献
14.
番禺30-1砂岩强水驱气藏储层非均质性研究 总被引:7,自引:5,他引:2
针对垂向非均质性严重且边底水能量强的番禺30-1气田面临的潜在开发问题,通过岩心分析及测井二次解释,对其夹层特征及储层非均质性等进行了研究,划分出19个流动单元并定量描述了各流动单元的特征参数,建立了该气田的精细地质模型。综合评价表明,新建的地质模型具有较高的精度,为该气藏合理开发提供了坚实的地质基础。 相似文献
15.
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
16.
杨宇 《中国室内装饰装修天地》2006,(7):54-61
华风气象影视大楼总面积4万平方米,根据空间功能不同分为办公大楼和商务写字楼两部分,办公大楼是集演播室、制作机房、办公室为一体的九层综合性建筑。设计师杨宇在刚接触到这个项目的时候,面对的是一个既成事实的建筑。 相似文献
17.
18.
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
19.
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
20.
首次对茂金属聚丙烯(miPP)/齐格勒-纳塔聚丙烯(ziPP)共混体系的流动性进行了系统的研究。研究发现,在miPP/ziPP共混体系中,miPP含量的变化改变了共混体系的相结构,这种相结构会随着温度和剪切速率的变化而产生明显的变化,从而改变了体系的流动性能,且该共混体系在不同剪切速率下的流动曲线可以分别通过两个模型进行模拟。 相似文献