全文获取类型
收费全文 | 661396篇 |
免费 | 35737篇 |
国内免费 | 19864篇 |
专业分类
电工技术 | 30058篇 |
技术理论 | 48篇 |
综合类 | 30262篇 |
化学工业 | 107243篇 |
金属工艺 | 39168篇 |
机械仪表 | 36453篇 |
建筑科学 | 36637篇 |
矿业工程 | 17530篇 |
能源动力 | 15106篇 |
轻工业 | 37797篇 |
水利工程 | 12342篇 |
石油天然气 | 39046篇 |
武器工业 | 3764篇 |
无线电 | 65601篇 |
一般工业技术 | 106800篇 |
冶金工业 | 52889篇 |
原子能技术 | 15521篇 |
自动化技术 | 70732篇 |
出版年
2023年 | 6811篇 |
2022年 | 13872篇 |
2021年 | 19399篇 |
2020年 | 14619篇 |
2019年 | 12764篇 |
2018年 | 16946篇 |
2017年 | 18720篇 |
2016年 | 17862篇 |
2015年 | 19516篇 |
2014年 | 25987篇 |
2013年 | 34717篇 |
2012年 | 34576篇 |
2011年 | 38854篇 |
2010年 | 33923篇 |
2009年 | 33336篇 |
2008年 | 32838篇 |
2007年 | 31156篇 |
2006年 | 29792篇 |
2005年 | 26023篇 |
2004年 | 19313篇 |
2003年 | 17206篇 |
2002年 | 16172篇 |
2001年 | 14740篇 |
2000年 | 14583篇 |
1999年 | 14350篇 |
1998年 | 14726篇 |
1997年 | 12312篇 |
1996年 | 10564篇 |
1995年 | 8715篇 |
1994年 | 7501篇 |
1993年 | 6410篇 |
1992年 | 5435篇 |
1991年 | 5013篇 |
1990年 | 4792篇 |
1989年 | 4413篇 |
1988年 | 4145篇 |
1987年 | 3814篇 |
1986年 | 3596篇 |
1985年 | 3584篇 |
1984年 | 3464篇 |
1983年 | 3316篇 |
1981年 | 3135篇 |
1980年 | 3178篇 |
1979年 | 3304篇 |
1978年 | 3511篇 |
1977年 | 3483篇 |
1976年 | 3940篇 |
1975年 | 3214篇 |
1974年 | 3302篇 |
1973年 | 3350篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
J Comas I Rodríguez-Roda M Poch K V Gernaey C Rosen U Jeppsson 《Water science and technology》2006,53(4-5):303-311
Wastewater treatment plant operators encounter complex operational problems related to the activated sludge process and usually respond to these by applying their own intuition and by taking advantage of what they have learnt from past experiences of similar problems. However, previous process experiences are not easy to integrate in numerical control, and new tools must be developed to enable re-use of plant operating experience. The aim of this paper is to investigate the usefulness of a case-based reasoning (CBR) approach to apply learning and re-use of knowledge gained during past incidents to confront actual complex problems through the IWA/COST Benchmark protocol. A case study shows that the proposed CBR system achieves a significant improvement of the benchmark plant performance when facing a high-flow event disturbance. 相似文献
3.
In this paper, implementation of the Benchmark Simulation Model No 2 (BSM2) within Matlab-Simulink is presented. The BSM2 is developed for plant-wide WWTP control strategy evaluation on a long-term basis. It consists of a pre-treatment process, an activated sludge process and sludge treatment processes. Extended evaluation criteria are proposed for plant-wide control strategy assessment. Default open-loop and closed-loop strategies are also proposed to be used as references with which to compare other control strategies. Simulations indicate that the BM2 is an appropriate tool for plant-wide control strategy evaluation. 相似文献
4.
Intensive use of the benchmark simulation model No. 1 (BSM1), a protocol for objective comparison of the effectiveness of control strategies in biological nitrogen removal activated sludge plants, has also revealed a number of limitations. Preliminary definitions of the long-term benchmark simulation model No. 1 (BSM1_LT) and the benchmark simulation model No. 2 (BSM2) have been made to extend BSM1 for evaluation of process monitoring methods and plant-wide control strategies, respectively. Influent-related disturbances for BSM1_LT/BSM2 are to be generated with a model, and this paper provides a general overview of the modelling methods used. Typical influent dynamic phenomena generated with the BSM1_LT/BSM2 influent disturbance model, including diurnal, weekend, seasonal and holiday effects, as well as rainfall, are illustrated with simulation results. As a result of the work described in this paper, a proposed influent model/file has been released to the benchmark developers for evaluation purposes. Pending this evaluation, a final BSM1_LT/BSM2 influent disturbance model definition is foreseen. Preliminary simulations with dynamic influent data generated by the influent disturbance model indicate that default BSM1 activated sludge plant control strategies will need extensions for BSM1_LT/BSM2 to efficiently handle 1 year of influent dynamics. 相似文献
5.
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
6.
World oil production and reserve additions heavily depend on giant oilfields. Currently, there are more than 4,000 producing oilfields in the world, producing around 68 million barrels of oil per day. Most oilfields in the world are minor ones, with oil production below 20,000 barrels per day; only 3% (about 120) oilfields in the world produce over 100,000 barrels per day with overall daily production exceeding 32 million barrels, which accounts for 47% of the total world oil supply . The scales of the oilfields heavily influence economic indices like investment, production and life spans of the oilfields. Therefore, giant oilfields have always been the dream of oil finders and targets of geologists' researches . 相似文献
7.
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
8.
9.
H. L. Du S. R. Rose Z. D. Xiang P. K. Datta X. Y. Li 《Materialwissenschaft und Werkstofftechnik》2003,34(4):421-426
The oxidation/sulphidation behaviour of a Ti‐46.7Al‐1.9W‐0.5Si alloy with a TiAl3 diffusion coating was studied in an environment of H2/H2S/H2O at 850oC. The kinetic results demonstrate that the TiAl3 coating significantly increased the high temperature corrosion resistance of Ti‐46.7Al‐1.9W‐0.5Si. The SEM, EDX, XRD and TEM analysis reveals that the formation of an Al2O3 scale on the surface of the TiAl3‐coated sample was responsible for the enhancement of the corroison resistance. The Ti‐46.7Al‐1.9W‐0.5Si alloy was also modified by Nb ion implantation. The Nb ion implanted and as received sampels were subjected to cyclic oxidation in an open air at 800oC. The Nb ion implantation not only increased the oxidation resistance but also substantially improved the adhesion of scale to the substrate. 相似文献
10.
为了分析多水库系统中两座水库之间灌溉用水的分配问题,建立了基到动态规划的神经网络模型。为了研究从一座上游水库取水在下游两座之库之间进行水量分配的问题,提出了3个状态变量和4个决策变量的改进的动态规划算法。采用神经网络模型,用3个状态变量动态规划算法得出调度原则,就所研究的多水库系统实例来说,新的动态规划神经网络模型的性能很好,将该模型的性能与临时凑合的标准调度原则和以前推荐使用的约束动态规划神经网络模型进行了比较。 相似文献