全文获取类型
收费全文 | 527108篇 |
免费 | 26010篇 |
国内免费 | 13111篇 |
专业分类
电工技术 | 21893篇 |
技术理论 | 56篇 |
综合类 | 19806篇 |
化学工业 | 82806篇 |
金属工艺 | 25831篇 |
机械仪表 | 26528篇 |
建筑科学 | 29693篇 |
矿业工程 | 11701篇 |
能源动力 | 14301篇 |
轻工业 | 32828篇 |
水利工程 | 6933篇 |
石油天然气 | 25786篇 |
武器工业 | 2606篇 |
无线电 | 63195篇 |
一般工业技术 | 76062篇 |
冶金工业 | 63357篇 |
原子能技术 | 6715篇 |
自动化技术 | 56132篇 |
出版年
2023年 | 5485篇 |
2022年 | 9571篇 |
2021年 | 13748篇 |
2020年 | 10710篇 |
2019年 | 9240篇 |
2018年 | 11245篇 |
2017年 | 12408篇 |
2016年 | 11375篇 |
2015年 | 13631篇 |
2014年 | 18394篇 |
2013年 | 26923篇 |
2012年 | 24458篇 |
2011年 | 28358篇 |
2010年 | 23973篇 |
2009年 | 23926篇 |
2008年 | 23904篇 |
2007年 | 23394篇 |
2006年 | 23751篇 |
2005年 | 21284篇 |
2004年 | 15437篇 |
2003年 | 14103篇 |
2002年 | 12926篇 |
2001年 | 12660篇 |
2000年 | 12802篇 |
1999年 | 14973篇 |
1998年 | 23575篇 |
1997年 | 16967篇 |
1996年 | 14199篇 |
1995年 | 11040篇 |
1994年 | 9312篇 |
1993年 | 8041篇 |
1992年 | 5840篇 |
1991年 | 5187篇 |
1990年 | 4685篇 |
1989年 | 4226篇 |
1988年 | 3774篇 |
1987年 | 2895篇 |
1986年 | 2820篇 |
1985年 | 2932篇 |
1984年 | 2545篇 |
1983年 | 2257篇 |
1982年 | 2089篇 |
1981年 | 2165篇 |
1980年 | 1916篇 |
1979年 | 1720篇 |
1978年 | 1682篇 |
1977年 | 2051篇 |
1976年 | 2751篇 |
1975年 | 1437篇 |
1974年 | 1381篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
The aim of this study was to evaluate the use of total coliforms (TC) and faecal coliforms (FC) using a membrane filtration method for precise monitoring of faecal pollution in Korean surface water. The samples were collected in Korea from both main rivers and their tributaries. Presumptive TC * FC were enumerated. The ratios of presumptive FC to TC were not constant, but varied widely, and TC were difficult to enumerate because of overgrowth by background colonies. For FC this was not the case. Seven hundred and three purified strains of presumptive TC * FC and their background colonies were biotyped using API 20E. Among 272 presumptive TC, non-faecal related species, Aeromonas hydrophila dominated (34.6%) and E. coli accounted for only 5.1%. In contrast, E. coli made up 89% of the 209 presumptive FC. Furthermore, of 164 background colonies on Endo Agar LES, 54.9% was A. hydrophila, while background colonies on m-FC Agar were few (58 strains), and despite their atypical colony appearance, most of them were biotyped as enteric bacteria. These results reveal that the detection of FC rather than TC using m-FC Agar is more appropriate for faecal pollution monitoring in eutrophicated surface water located in a temperate region. 相似文献
15.
For realizing a naturalistic collaboration between the human and the robot, we have to establish the intention sharing from the series of motion data that are observed and exchanged between the human and the machine. In a word, this is a problem to detect "meanings" out of the digitized data stream. In this paper, we propose a novel approach based on semiosis, and present a method of interpreting bodily motions using recurrent neural networks called Elman networks. We made some experiments using the raw data acquired while a human performs a simple task of fetching objects by stretching and folding his/her arm, and demonstrate that the network can learn invariant features of the generalized motion concepts, classify the motion by referring to self-organized memory structure, and understand a task structure of the observed human bodily motion. These capabilities are essential for machine intelligence to establishing the human-robot shared autonomy, a new style of human-machine collaboration proposed in the area of robotics. 相似文献
16.
第三节 常见氧化物膜目前研究最多的氧化物膜可谓二氧化硅和二氧化钛膜 ,这两种薄膜也是接受呈色离子、制备彩色镀膜常用的基体膜 ,所以 ,有必要将它们单独列出 ,加以讨论。1 二氧化钛膜在所有高折射率材料中 ,由钛的化合物制备的氧化物膜具有特殊的实际意义。因此 ,对二氧化 相似文献
17.
对在实际组网中选择合理的ASON架构和保护方式作了相应分析,并为搭建可向ASON平滑演进的传统网络时需注意的问题提供了参考意见, 相似文献
18.
J.M. Roth T.G. Ulmer N.W. Spellmeyer S. Constantine M.E. Grein 《Photonics Technology Letters, IEEE》2004,16(9):2009-2011
We demonstrate a novel 40-GHz mode-locked fiber laser that utilizes a single active device to provide both gain and mode-locking. The laser produces pulses as short as 2.2 ps, is tunable over a 27-nm band centered at 1553 nm, and exhibits long-term stability without cavity-length feedback control. The pulse train at 1556 nm was used in a 40-Gb/s transmission experiment over 45 km with a low 0.4-dB power penalty. 相似文献
19.
T A Elmitwalli R Raimundo K Kujawa-Roelevel G Zeeman 《Water science and technology》2006,53(9):177-184
The post-treatment of domestic sewage pretreated in a 6 m3 UASB was investigated in two high-rate anaerobic filter (AF) reactors operated in parallel. The difference between the two AF reactors was only the addition of cationic polymer to the second reactor (AF + P). The reactors were operated at low temperatures, ranged between 13 and 20 degrees C. The media in each AF reactor consisted of vertical sheets of reticulated-polyurethane foam (RPF) with knobs. The results demonstrated that the AF + P reactor (HRT = 3 h) with cationic polymer addition (2 mg/L) was an efficient system for post-treatment. The removal efficiencies for total, suspended, colloidal and dissolved COD were, respectively, 41, 86 and 76 and 12% in the AF + P reactor and they were, respectively, 80, 97, 77 and 66% in the UASB + (AF + P) system. The removal of total, suspended and colloidal COD in the UASB + (AF + P) system were significantly higher than those achieved in the UASB + AF system. As hardly any nutrient was removed in the UASB + (AF + P) system, the effluent after pathogen removal is a valuable product for irrigation and fertilisation to close the water and nutrients cycle. 相似文献
20.
N. Jongen M. Donnet P. Bowen J. Lemaître H. Hofmann R. Schenk C. Hofmann M. Aoun‐Habbache S. Guillemet‐Fritsch J. Sarrias A. Rousset M. Viviani M.T. Buscaglia V. Buscaglia P. Nanni A. Testino J.R. Herguijuela 《化学工程与技术》2003,26(3):303-305
The synthesis of powders with controlled shape and narrow particle size distributions is still a major challenge for many industries. A continuous Segmented Flow Tubular Reactor (SFTR) has been developed to overcome homogeneity and scale‐up problems encountered when using batch reactors. Supersaturation is created by mixing the co‐reactants in a micromixer inducing precipitation; the suspension is then segmented into identical micro‐volumes by a non‐miscible fluid and sent through a tube. These micro‐volumes are more homogeneous when compared to large batch reactors leading to narrower size distributions, better particle morphology, polymorph selectivity and stoichiometry. All these features have been demonstrated on single tube SFTR for different chemical systems. To increase productivity for commercial application the SFTR is being “scaled‐out” by multiplying the number of tubes running in parallel instead of scaling‐up by increasing their size. The versatility of the multi‐tube unit will allow changes in type of precipitate with a minimum of new investment as new chemistry can be researched, developed and optimised in a single tube SFTR and then transferred to the multi‐tube unit for powder production. 相似文献