全文获取类型
收费全文 | 110394篇 |
免费 | 9366篇 |
国内免费 | 5182篇 |
专业分类
电工技术 | 6344篇 |
技术理论 | 12篇 |
综合类 | 10327篇 |
化学工业 | 16825篇 |
金属工艺 | 1898篇 |
机械仪表 | 3061篇 |
建筑科学 | 15381篇 |
矿业工程 | 5888篇 |
能源动力 | 6150篇 |
轻工业 | 5869篇 |
水利工程 | 22780篇 |
石油天然气 | 8634篇 |
武器工业 | 373篇 |
无线电 | 3527篇 |
一般工业技术 | 5317篇 |
冶金工业 | 4262篇 |
原子能技术 | 1541篇 |
自动化技术 | 6753篇 |
出版年
2024年 | 341篇 |
2023年 | 1191篇 |
2022年 | 2376篇 |
2021年 | 2900篇 |
2020年 | 3192篇 |
2019年 | 2701篇 |
2018年 | 2623篇 |
2017年 | 3245篇 |
2016年 | 3695篇 |
2015年 | 3657篇 |
2014年 | 6802篇 |
2013年 | 6775篇 |
2012年 | 8279篇 |
2011年 | 8336篇 |
2010年 | 6165篇 |
2009年 | 6480篇 |
2008年 | 5794篇 |
2007年 | 7534篇 |
2006年 | 7018篇 |
2005年 | 6308篇 |
2004年 | 5031篇 |
2003年 | 4587篇 |
2002年 | 3973篇 |
2001年 | 3251篇 |
2000年 | 2709篇 |
1999年 | 2101篇 |
1998年 | 1489篇 |
1997年 | 1228篇 |
1996年 | 950篇 |
1995年 | 874篇 |
1994年 | 678篇 |
1993年 | 515篇 |
1992年 | 416篇 |
1991年 | 308篇 |
1990年 | 217篇 |
1989年 | 246篇 |
1988年 | 158篇 |
1987年 | 153篇 |
1986年 | 117篇 |
1985年 | 112篇 |
1984年 | 110篇 |
1983年 | 67篇 |
1982年 | 36篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1979年 | 29篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1966年 | 10篇 |
1964年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
湛江电厂1号发电机定子冷却水处理方式的改造 总被引:1,自引:0,他引:1
简述发电机铜导线腐蚀机理,湛江电厂1号发电机定子冷却处理方式改造前后各自的特点。比较新旧两种方式水质处理效果、安全性、经济性。采用超净化装置后,解决了原来处理方式的所有缺点,水质达到质量标准, 创造良好的经济效益,值得推广改造和借鉴。 相似文献
132.
The logarithmic model is often used to describe the relationships between factors.It often gives good statistical characteristics.Yet,in the process of modeling of soil and water conservation,we find out that this“good”model cannot guarantee good result.In this paper we make an inquiry into the intrinsic reasons.It is shown that the logarithmic model has the property of enlarging or reducing model errors,and the disadvantages of the logarithmic model are analyzed. 相似文献
133.
通过阴离子型端丙烯酸酯基聚氨酯(UAA)与N-异丙基丙烯酰胺(NIPAAm)的共聚交联反应,制备了pH/温度敏感性水凝胶,分析了水凝胶的结构形态及溶胀水的状态.结果表明,凝胶相结构均匀,随聚氨酯含量的降低,凝胶的骨架变得松散,并且孔道结构增大,导致溶胀凝胶中不可冻结水含量及凝胶强度的降低. 相似文献
134.
张朝晖 《重庆理工大学学报(自然科学版)》2003,17(6):75-79
分析了中国水资源的特点和基本概况,探讨了水资源利用而应采取的全方位措施.即增强忧患意识,改变思想观念,保护自然资源,优化生态环境. 相似文献
135.
液位测控系统的可靠性设计 总被引:1,自引:0,他引:1
以系统的可靠性为目标对液位测控系统进行综合设计和技术改进。通过对软、硬件功能的合理分配和对关键技术难点解决方案的选择,以及兼容设计、降额设计、抗干扰设计等可靠性保障技术的应用提高了小型液位测控系统的技术指标和可靠性指标。同时,本文也为其它小型智能化仪表的可靠性保障设计提供了一种思路和方法。 相似文献
136.
Fuzzy logic for signal prediction in nuclear systems 总被引:2,自引:0,他引:2
In this paper, we present a fuzzy logic-based algorithm which allows to build a predictive model of an evolving signal. The if-then rules are inferred from the available input-output data. The errors of the model predictions with respect to the measured plant signals can then be used to detect, in real-time, any deviation of the process due either to a component's failure or to an operator's action. Applications of the approach are presented with respect to a chaotic time series of literature and to the water level in the steam generator of a PWR. 相似文献
137.
J. Pohlus 《Progress in Nuclear Energy》2003,43(1-4):27-34
The nuclear reactor core design and the nuclear fuel management have been changed remarkable during the last few years. This development was initiated by increasing costs for the fuel recycling and nuclear waste storage. The fuel material, the fuel pellet fabrication, the fuel assembly structure and the core composition have been varied to get an effective fuel exploitation. Based on advanced core process conditions the reactor power and the fuel burn-up have been increased at German plants in recent years. Improved dynamic process monitoring procedures are required to get more information about the varied core process behaviour during the reactor operation. Since several years ISTec has been performed investigations to the process monitoring based on process signal measurements in German nuclear power plants. Using the standard instrumentation of the plants process signals have been measured and analysed by means of the digital data acquisition system SIGMA. The measured time signals are influenced by core process transients, global and local process fluctuations and by signal line transfer functions. Advanced time series analysis methods have been applied to separate different process effects in the multiple signal matrix. The separation of different process influences can improve significantly the information about the process condition in the reactor core. 相似文献
138.
TiO2 fims have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures
from 0. 10 Pa.to 0.65 Pa. The transmittance (UV-vis) and photoluminescence (PL) spectra of the films were recorded. The results
of the UV-vis spectra show that the deposition rate of the films decreased at oxygen partial pressure P(O2)≥0.15 Pa, the band gap increased from 3.48 eV to 3.68eV for direct transition and from 3.27 eV to 3.34 eV for indirect transition
with increasing the oxygen partial pressure. The PL spectra show convincingly that the transition for films was indirect,
and there were some oxygen defect energy levels at the band gap of the films. With increasing the O2 partial pressure, the defect energy levels decreased. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy
levels at 2.63 eV and 2.41 eV, corresponding to 0.72 eV and 0.94 eV below the conduction band for a band gap of 3.35 eV, respectively.
For the films sputtered at 0.10 Pa and 0.15 Pa, there was an energy band formed between 3.12 eV and 2.06 eV, corresponding
to 0.23 eV and 1.29 eV below the conduction band.
ZHAO Qing-nan : Born in 1963
Funded by Natural Science Foundation of Hubei Province, China. 相似文献
139.
A comparison of 18 winter seasons of in situ and passive microwave-derived snow water equivalent estimates in Western Canada 总被引:1,自引:0,他引:1
The Meteorological Service of Canada (MSC) has developed an operational snow water equivalent (SWE) retrieval algorithm suite for western Canada that can be applied to both Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) data. Separate algorithms derive SWE for open environments, deciduous, coniferous, and sparse forest cover. A final SWE value represents the area-weighted average based on the proportional land cover within each pixel. The combined SSM/I and SMMR time series of dual polarized, multichannel, spaceborne passive microwave brightness temperatures extends back to 1978, providing a lengthy time series for algorithm assessment. In this study, 5-day average (pentad) passive microwave-derived SWE imagery for 18 winter seasons (December, January, February 1978/79 through 1995/96) was compared to SWE estimates taken from a distributed network of surface measurements throughout western Canada.Results indicated both vegetative and snowpack controls on the performance of MSC algorithms. In regions of open and low-density forest cover, the in situ and passive microwave SWE data exhibited both strong agreement and similar levels of interannual variability. In locations where winter season SWE typically exceeded 75 mm, and/or dense vegetative cover was present, dataset agreement weakened appreciably, with little interannual variability in the passive microwave SWE retrievals. These results have important implications for extending the SWE monitoring capability of the MSC algorithm suite to northern regions such as the Mackenzie River basin. 相似文献
140.