全文获取类型
收费全文 | 54968篇 |
免费 | 1964篇 |
国内免费 | 187篇 |
专业分类
电工技术 | 601篇 |
综合类 | 638篇 |
化学工业 | 9537篇 |
金属工艺 | 702篇 |
机械仪表 | 1151篇 |
建筑科学 | 1270篇 |
矿业工程 | 403篇 |
能源动力 | 714篇 |
轻工业 | 5154篇 |
水利工程 | 712篇 |
石油天然气 | 117篇 |
武器工业 | 4篇 |
无线电 | 2279篇 |
一般工业技术 | 4992篇 |
冶金工业 | 21889篇 |
原子能技术 | 222篇 |
自动化技术 | 6734篇 |
出版年
2024年 | 96篇 |
2023年 | 366篇 |
2022年 | 1021篇 |
2021年 | 1132篇 |
2020年 | 431篇 |
2019年 | 469篇 |
2018年 | 915篇 |
2017年 | 1168篇 |
2016年 | 1575篇 |
2015年 | 1206篇 |
2014年 | 976篇 |
2013年 | 1257篇 |
2012年 | 2919篇 |
2011年 | 3344篇 |
2010年 | 1365篇 |
2009年 | 1406篇 |
2008年 | 1194篇 |
2007年 | 1184篇 |
2006年 | 996篇 |
2005年 | 3637篇 |
2004年 | 2810篇 |
2003年 | 2280篇 |
2002年 | 1068篇 |
2001年 | 871篇 |
2000年 | 363篇 |
1999年 | 737篇 |
1998年 | 6247篇 |
1997年 | 3905篇 |
1996年 | 2595篇 |
1995年 | 1515篇 |
1994年 | 1120篇 |
1993年 | 1152篇 |
1992年 | 307篇 |
1991年 | 347篇 |
1990年 | 339篇 |
1989年 | 306篇 |
1988年 | 323篇 |
1987年 | 250篇 |
1986年 | 237篇 |
1985年 | 201篇 |
1984年 | 94篇 |
1983年 | 102篇 |
1982年 | 142篇 |
1981年 | 191篇 |
1980年 | 209篇 |
1979年 | 78篇 |
1978年 | 117篇 |
1977年 | 621篇 |
1976年 | 1326篇 |
1975年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Motivated by a study of similar problems stated for factors of words, we study forbidden subwords of a language or a word. A procedure for obtaining the set of all words avoiding a given set of subwords is presented. On the other hand, an algorithm for computing the set of minimal forbidden subwords for a word is given. The case of a two-letter alphabet appears to be particularly interesting and it is considered separately. 相似文献
92.
93.
E Persson M Ljunggren J la Cour Jansen R Strube L J?nsson 《Water science and technology》2006,53(12):139-147
A Discfilter with 10 and 18 microm filter openings, respectively, was placed in parallel to a flotation plant for separation of biological flocs from a post-denitrifying Kaldnes Moving Bed Process, the last treatment step at the municipal wastewater treatment plant at Sj?unda, Malm?, Sweden. The effluent concentrations from the 10 and 18 microm filter were 2-5 and 2-8 mg SS L(-1), respectively, which is comparable to, or better than, the flotation plant. Comparison with experiences from activated sludge plants shows that the Discfilter works especially well after the Kaldnes process. Particle size distribution (PSD) studies show that particles larger than the filter openings of 10 and 18 microm are separated with approximately 90% efficiency, whereas most of the smaller particles pass the filter. This fact indicates that the major particle separation mechanism is physical blocking. These findings point to the possibility of improving the prediction of the separation efficiency by combining measurements of turbidity and suspended solids with particle size analysis. 相似文献
94.
This paper presents an analysis of the data collected in the ambient vibration test of the International Guadiana cable-stayed Bridge, which links Portugal and Spain, based on different output-only identification techniques: peak-picking, frequency domain decomposition, covariance-driven stochastic subspace identification, and data-driven stochastic subspace identification. The purpose of the analysis is to compare the performance of the four techniques and evaluate their efficiency in dealing with specific challenges involved in the modal identification of the tested cable-stayed bridge, namely the existence of closely spaced modes, the perturbation produced by the local vibration of stay-cables, and the variation of modal damping coefficients with wind velocity. The identified natural frequencies and mode shapes are compared with the corresponding modal parameters provided by a previously developed numerical model. Additionally, the variability of some modal damping coefficients is related with the variation of the wind characteristics and associated with a component of aerodynamic damping. 相似文献
95.
Andreja ?gajnar Gotvajn Jana Zagorc-Kon?an Tatjana Ti?ler 《Canadian Metallurgical Quarterly》2007,133(1):89-94
The preoxidation of a highly polluted waste pharmaceutical fermentation broth using wet air oxidation (WAO) has been studied as a possible method for the effective removal of organics. The applied (pre)treatment method should enhance the biotreatability of the pharmaceutical fermentation broth in terms of reduced initial toxicity and higher biodegradability. Preliminary experiments in the pilot biological treatment plant were successful only at low organic loads, whereas the system collapses at higher ones. The characterization of the fermentation broth was started by common physicochemical analysis, whereas several bioassays were used to determine its impact on biological treatment plants and the environment. Toxicity prior to and after WAO was determined using the acute Vibrio fischeri test, measurement of inhibition of O2 consumption, and the Daphnia magna acute test. Ready biodegradability of the treated and untreated broth has also been assessed. WAO experiments were accomplished in the 2?L batch reactor at different temperatures (240/280°C) and operating pressures. WAO experiments confirmed reduction of the toxicity toward microorganisms, whereas oxidized wastewater was more toxic to daphnids. Biodegradability of the oxidized broth has also been enhanced. Further work has been focused on designing appropriate combination of WAO and biological processes. 相似文献
96.
Sinéad C. Mac Namara Maria M. Garlock David P. Billington 《Canadian Metallurgical Quarterly》2007,21(2):152-156
Steam generator replacement at nuclear power plants requires large construction openings in nuclear containment structures. This study examines the effects of such openings placed in a 61?cm (2?ft) thick dome of a shield building. The dome is cast in two layers, and the limiting cases of the two layers acting as one and the lower layer carrying the entire load are considered. Without openings, the stresses due to dead load in the structure are very low when compared to the material strength. With openings, the loads are easily redistributed around the opening, and the maximum stresses for the conservative case are between three and four and one-half times larger than in the original structure with no openings. The extent of the affected area around the holes is relatively small. Smooth corners in the openings are necessary to avoid high local stress concentrations. 相似文献
97.
Bonto-Kane Maria Vicente A. Chin Alvin Mc Carthy Sheila Srikulwong Mayuree Timmins Paul J. 《Pervasive Computing, IEEE》2007,6(4)
Pervasive computing is as much about the user as it is about the technology. So, the Fifth International Conference on Pervasive Computing emphasized desirability rather than just feasibility. Featured themes included user benefits, human-computer interaction, group and social interactions, context awareness, finding and positioning people and objects, and personal privacy. 相似文献
98.
99.
100.
Here we are presenting the case of a 70-years-old woman who has hepatic cirrhosis anti-HCV and insulin-dependent diabetes mellitus, without relevant epidemiologic ascendants or previous transfusions and HBV, HIV negatives. On admission to our hospital she showed signs of autoimmune hemolytic anaemia (AHA) which was confirmed by positive direct Coombs test and an improvement in blood test after corticoid treatment. Having discarded other possible causes such as drugs infectious diseases or essential mixed cryoglobulinemia (CME), we put forward the possible association between AHA and infection by HCV, where AHA was an extrahepatic immunological manifestation of HCV. This fact has never been brought to light in previous medical literature. 相似文献