全文获取类型
收费全文 | 333002篇 |
免费 | 24006篇 |
国内免费 | 12559篇 |
专业分类
电工技术 | 17911篇 |
技术理论 | 56篇 |
综合类 | 19686篇 |
化学工业 | 56539篇 |
金属工艺 | 18546篇 |
机械仪表 | 21176篇 |
建筑科学 | 25715篇 |
矿业工程 | 10960篇 |
能源动力 | 9762篇 |
轻工业 | 18632篇 |
水利工程 | 5254篇 |
石油天然气 | 22975篇 |
武器工业 | 2599篇 |
无线电 | 36631篇 |
一般工业技术 | 39801篇 |
冶金工业 | 18379篇 |
原子能技术 | 3216篇 |
自动化技术 | 41729篇 |
出版年
2024年 | 1289篇 |
2023年 | 5210篇 |
2022年 | 8869篇 |
2021年 | 12543篇 |
2020年 | 9824篇 |
2019年 | 8010篇 |
2018年 | 9199篇 |
2017年 | 10376篇 |
2016年 | 9278篇 |
2015年 | 12219篇 |
2014年 | 15866篇 |
2013年 | 19180篇 |
2012年 | 20165篇 |
2011年 | 22443篇 |
2010年 | 19199篇 |
2009年 | 18330篇 |
2008年 | 17974篇 |
2007年 | 17395篇 |
2006年 | 18278篇 |
2005年 | 16131篇 |
2004年 | 10344篇 |
2003年 | 9127篇 |
2002年 | 8132篇 |
2001年 | 7473篇 |
2000年 | 8003篇 |
1999年 | 9653篇 |
1998年 | 8157篇 |
1997年 | 6770篇 |
1996年 | 6362篇 |
1995年 | 5339篇 |
1994年 | 4378篇 |
1993年 | 3089篇 |
1992年 | 2492篇 |
1991年 | 1961篇 |
1990年 | 1504篇 |
1989年 | 1232篇 |
1988年 | 1019篇 |
1987年 | 681篇 |
1986年 | 535篇 |
1985年 | 342篇 |
1984年 | 243篇 |
1983年 | 204篇 |
1982年 | 196篇 |
1981年 | 129篇 |
1980年 | 130篇 |
1979年 | 67篇 |
1978年 | 33篇 |
1977年 | 38篇 |
1976年 | 55篇 |
1975年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
阐述了邢台矿区的水文地质特征,影响下组煤开采的主要充水因素,重点总结了公司下组煤带压开采的实践经验、技术路线和关键的防治水技术。 相似文献
133.
Transformations in machining. Part 1. enhancement of wavelet transformation neural network (WT-NN) combination with a preprocessor 总被引:2,自引:0,他引:2
X. Wang P. Chen I.N. Tansel Yenilmez A 《International Journal of Machine Tools and Manufacture》2006,46(1):36-42
Properly selected transformation methods obtain the most significant characteristics of metal cutting data efficiently and simplify the classification. Wavelet Transformation (WT) and Neural Networks (NN) combination was used to classify the experimental cutting force data of milling operations previously. Preprocessing (PreP) of the approximation coefficients of the WT is proposed just before the classification by using the Adaptive Resonance Theory (ART2) type NNs. Genetic Algorithm (GA) was used to estimate the weights of each coefficient of the PreP. The WT-PreP-NN (ART2) combination worked at lower vigilances by creating only a few meaningful categories without any errors. The WT-NN (ART2) combination could obtain the same error rate only if very high vigilances are used and many categories are allowed. 相似文献
134.
Ten-user truly asynchronous gigabit OCDMA transmission experiment with a 511-chip SSFBG en/decoder 总被引:8,自引:0,他引:8
Hamanaka T. Xu Wang Naoya Wada Nishiki A. Kitayama K. 《Lightwave Technology, Journal of》2006,24(1):95-102
A ten-user truly asynchronous gigabit coherent-optical-code-division-multiple-access (OCDMA) transmission was experimentally demonstrated without using any timing coordination. The enabling technologies are a record-length 511-chip superstructured-fiber-Bragg-grating (SSFBG) en/decoder and a supercontinuum (SC)-based optical-thresholding technique to significantly suppress the signal interference beat noise as well as the multiple-access-interference (MAI) noise. 相似文献
135.
136.
137.
Yang Lüyun 《中国稀土学报(英文版)》2006,24(Z2)
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm. 相似文献
138.
A shortcut model is developed for predicting the HETP of a structured packed distillation column operating at elevated pressure. The proposed model incorporates the geometrical parameters of the packing, physical properties of the vapor and liquid phases, and the hydrodynamics of the two‐phase flow. The proposed model is tested and validated by comparing the predicted results with the present experimental data and some published HETP data. The results show that the proposed model can predict the experimental data with a deviation smaller than 20 %. 相似文献
139.
In order to meet increasingly stringent discharge standards, new applications and control strategies for the sustainable removal of nitrogen from wastewater have to be implemented. In the past years, numerous studies have been carried out dealing with the application of fuzzy logic to improve the control of the activated sludge process. In this paper, fuzzy control strategies of predenitrification systems are presented that could lead to better effluent quality and, in parallel, to a reduction of chemicals consumption. Extensive experimental investigations on lab scale plant studies have shown that there was excellent correlation between nitrate concentration and ORP value at the end of the anoxic zone. Results indicated that ORP could be used as an on-line fuzzy control parameter of nitrate recirculation and external carbon addition. The optimal value of ORP to control nitrate recirculation and external carbon addition was - 86 +/- 2 mV and - 90 +/- 2 mV, respectively. The results obtained with real wastewater also showed the good performance and stability of the fuzzy controllers independently from external disturbances. The integrated control structure of nitrate recirculation and external carbon addition in the predenitrification system is also presented. 相似文献
140.