全文获取类型
收费全文 | 40533篇 |
免费 | 4875篇 |
国内免费 | 3237篇 |
专业分类
电工技术 | 4874篇 |
技术理论 | 1篇 |
综合类 | 4337篇 |
化学工业 | 3179篇 |
金属工艺 | 3129篇 |
机械仪表 | 2933篇 |
建筑科学 | 2767篇 |
矿业工程 | 1696篇 |
能源动力 | 1785篇 |
轻工业 | 1209篇 |
水利工程 | 1302篇 |
石油天然气 | 5287篇 |
武器工业 | 601篇 |
无线电 | 5147篇 |
一般工业技术 | 4624篇 |
冶金工业 | 1454篇 |
原子能技术 | 732篇 |
自动化技术 | 3588篇 |
出版年
2024年 | 204篇 |
2023年 | 641篇 |
2022年 | 1126篇 |
2021年 | 1298篇 |
2020年 | 1338篇 |
2019年 | 1168篇 |
2018年 | 1050篇 |
2017年 | 1496篇 |
2016年 | 1555篇 |
2015年 | 1657篇 |
2014年 | 2296篇 |
2013年 | 2314篇 |
2012年 | 2955篇 |
2011年 | 3180篇 |
2010年 | 2363篇 |
2009年 | 2380篇 |
2008年 | 2143篇 |
2007年 | 2723篇 |
2006年 | 2571篇 |
2005年 | 2151篇 |
2004年 | 1847篇 |
2003年 | 1675篇 |
2002年 | 1348篇 |
2001年 | 1114篇 |
2000年 | 1088篇 |
1999年 | 930篇 |
1998年 | 719篇 |
1997年 | 641篇 |
1996年 | 563篇 |
1995年 | 448篇 |
1994年 | 398篇 |
1993年 | 263篇 |
1992年 | 204篇 |
1991年 | 166篇 |
1990年 | 157篇 |
1989年 | 161篇 |
1988年 | 93篇 |
1987年 | 43篇 |
1986年 | 29篇 |
1985年 | 22篇 |
1984年 | 28篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1959年 | 9篇 |
1958年 | 3篇 |
1955年 | 3篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
求文针对我国天然气凝液如何利用问题,结合新技术进展,进行了初步探讨,认为原料较多的场合,应以催化脱氢或芳构化作为当前的主要加工方向。对原料较少的场合,也提出一些看法。 相似文献
92.
H. Wolf F. Wagner Th Wichert R. Grill E. Belas Isolde Collaboration 《Journal of Electronic Materials》2006,35(6):1350-1353
Anomalous diffusion profiles of Ag in single crystalline CdTe were observed using the radiotracer 111Ag. The diffusion anneals were performed at 800 K under Cd or Te vapor and in vacuum with low Ag concentrations. The measured
Ag profiles directly reflect the distribution of the self-interstitials and vacancies of the Cd sublattice and are the result
of chemical self-diffusion which describes the variation of the deviation from stoichiometry of the binary crystal as a function
of depth and time. It turned out that the spread of the Ag dopant essentially is determined by the drift of the charged defects
within the electric field caused by the distribution of the extrinsic and intrinsic defects. 相似文献
93.
1. Introduction Side-wall acoustic logging tools, such as the Segmented Bond Tool (SBT) from Baker Atlas and the tools for open hole measurements, utilize acoustic transducers mounted on six pads to make compensated acoustic velocity and attenuation measurements which are not affected by mud weight, gas cut, fast formation effects, casing surface conditions or reasonable tool de- centralizing. Studies on the wave fields generated by these tools are very important to tool design and data int… 相似文献
94.
T. Brard F. H. Cornet 《International Journal of Rock Mechanics and Mining Sciences》2003,40(7-8):1121-1140
When they occur, borehole breakouts are considered strong markers of principal stress directions at depth. An innovative processing method for automatically identifying breakouts from ultrasonic borehole wall images has been developed. It has been applied to data sets from two deep, sub-vertical wells (GPK1 and GPK2) at the Soultz geothermal site in eastern France. In well GPK1, below 3 km depth, compression breakouts, with a 95°±7° azimuth, increasingly occur with depth. They result from time dependent compression failure at sub-critical stress levels and are indicators of the minimum horizontal principal stress orientation. However, in the uppermost logged section of well GPK2 (1.6–2.9 km depth), continuous borehole elongations share roughly the same azimuth with so called drilling-induced fractures (164°±18° and 175°±17° azimuth, respectively). Both features concomitantly vanish with depth, together with the amplitude of the thermal perturbation induced by drilling. It is proposed that these latter borehole elongations result from a pervasive, cooling-induced, tensile micro-cracking process prior to macroscopic failure localization. They are termed thermal elongations and are indicators of the maximum horizontal principal stress orientation. Had a simple logging caliper tool been used for this work, these thermal elongations might have been confused with classical compression breakouts. A simple criterion for differentiating compression breakouts from thermal elongation is proposed. 相似文献
95.
L. X. Che R. Q. Yang Y. Gu T. K. Xia 《The International Journal of Advanced Manufacturing Technology》2006,31(5-6):614-620
This paper presents a method of calculating the insulating safety distances for hot-line working robots at high voltage when dielectric is adulterated with conducts. Also, finite element method is adopted to calculate the electric field strength to find whether it is beyond the critical. The above methods have been applied to analyze the insulating safety of the robot for hot-line sweeping post insulators in a 220 KV substation. They have also been testified by experimentations. 相似文献
96.
97.
茨21-133井CO2吞吐技术初步试验 总被引:1,自引:0,他引:1
茨榆坨油田茨13块原油属于普通稠油,1993年开始蒸汽吞吐采油,从第二轮开始效果明显变差,注汽返排率低,有效周期短,产量下降快,套管变形井增多。针对这些问题,在该区块茨21—133井进行CO2吞吐采油工艺现场试验,获得成功,增油效果明显。 相似文献
98.
99.
100.
论述了PROFIBUS-DP现场总线技术在大庆石化分公司腈纶厂纺丝线电气控制系统改造中的成功实现,分析了PROFIBUS-DP的通讯原理,阐述了SIEMENS S7-300PLC对纺丝电控系统中24台MASTERDRIVES VC型变频器进行启动、停止以及速度给定的控制。 相似文献