全文获取类型
收费全文 | 60719篇 |
免费 | 7283篇 |
国内免费 | 5223篇 |
专业分类
电工技术 | 6792篇 |
技术理论 | 1篇 |
综合类 | 6804篇 |
化学工业 | 5403篇 |
金属工艺 | 4434篇 |
机械仪表 | 3793篇 |
建筑科学 | 4444篇 |
矿业工程 | 2493篇 |
能源动力 | 2679篇 |
轻工业 | 2543篇 |
水利工程 | 2189篇 |
石油天然气 | 7139篇 |
武器工业 | 786篇 |
无线电 | 6617篇 |
一般工业技术 | 6588篇 |
冶金工业 | 2291篇 |
原子能技术 | 958篇 |
自动化技术 | 7271篇 |
出版年
2024年 | 334篇 |
2023年 | 1170篇 |
2022年 | 1848篇 |
2021年 | 2197篇 |
2020年 | 2182篇 |
2019年 | 1900篇 |
2018年 | 1654篇 |
2017年 | 2175篇 |
2016年 | 2270篇 |
2015年 | 2387篇 |
2014年 | 3308篇 |
2013年 | 3578篇 |
2012年 | 4204篇 |
2011年 | 4552篇 |
2010年 | 3400篇 |
2009年 | 3542篇 |
2008年 | 3246篇 |
2007年 | 4073篇 |
2006年 | 3861篇 |
2005年 | 3295篇 |
2004年 | 2887篇 |
2003年 | 2447篇 |
2002年 | 2041篇 |
2001年 | 1743篇 |
2000年 | 1559篇 |
1999年 | 1371篇 |
1998年 | 1036篇 |
1997年 | 905篇 |
1996年 | 808篇 |
1995年 | 659篇 |
1994年 | 586篇 |
1993年 | 416篇 |
1992年 | 318篇 |
1991年 | 254篇 |
1990年 | 240篇 |
1989年 | 223篇 |
1988年 | 157篇 |
1987年 | 79篇 |
1986年 | 65篇 |
1985年 | 41篇 |
1984年 | 43篇 |
1983年 | 23篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1975年 | 7篇 |
1959年 | 11篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Christine Di Massimo Paul A. Lant Aidan Saunders Gary A. Montague Ming T. Tham A. Julian Morris 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(3):265-277
The last decade has seen the development of a number of approaches for estimating those variables which are difficult to measure on-line in industrial process situations. Whilst a range of techniques is available, a common element is the use of process knowledge in the form of a system model. In the case of bioprocess systems, although a large range of models has been presented in the literature, their use in estimation schemes on an industrial scale has been limited. A number of reasons can be identified for their low level of utilisation. Of particular significance is the uncertainty which exists in quantifying system performance and the process-model mismatch which inevitably results. The level of ‘pre-defined model’ uncertainty, together with the knowledge gained during the course of the fermentation, serves to dictate estimator structure. The paper considers a range of estimation strategies and contrasts, through industrial applications, their performance characteristics and utility. 相似文献
112.
An 8-valued commutative ring is developed to process colored images. Algebraic operators are defined to perform a number of operations such as the extraction of the primary colors and contours of different colors. 相似文献
113.
An implementation for a fast public-key cryptosystem 总被引:9,自引:0,他引:9
In this paper we examine the development of a high-speed implementation of a system to perform exponentiation in fields of the form GF(2
n
). For sufficiently large n, this device has applications in public-key cryptography. The selection of representation and observations on the structure of multiplication have led to the development of an architecture which is of low complexity and high speed. A VLSI implementation has being fabricated with measured throughput for exponentiation for cryptographic purposes of approximately 300 kilobits per second. 相似文献
114.
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
115.
116.
介绍了骑马岭水电站砂石加工系统的料源规划、系统规划设计、系统工艺流程及环保措施。该加工系统采用的典型的二段破碎工艺,对中小型水电站混凝土骨料生产系统的设计具有一定的参考价值。同时,该加工系统在废水处理水回收利用及细砂与石粉回收、防尘、降低噪声,以及固体废弃物处置等方面,均采取了相应的环保措施,以减少其对施工人员和周围环境的影响。 相似文献
117.
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
118.
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
119.
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
120.
Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high‐copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion producsts, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas‐atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe‐cut powder based amalgam. In addition to different volume fraction of the Ag‐Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed. 相似文献