全文获取类型
收费全文 | 2504篇 |
免费 | 49篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 136篇 |
综合类 | 2篇 |
化学工业 | 445篇 |
金属工艺 | 89篇 |
机械仪表 | 55篇 |
建筑科学 | 49篇 |
能源动力 | 91篇 |
轻工业 | 167篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 259篇 |
一般工业技术 | 470篇 |
冶金工业 | 538篇 |
原子能技术 | 85篇 |
自动化技术 | 165篇 |
出版年
2023年 | 13篇 |
2022年 | 11篇 |
2021年 | 42篇 |
2020年 | 20篇 |
2019年 | 19篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 37篇 |
2015年 | 31篇 |
2014年 | 53篇 |
2013年 | 129篇 |
2012年 | 74篇 |
2011年 | 106篇 |
2010年 | 86篇 |
2009年 | 71篇 |
2008年 | 88篇 |
2007年 | 102篇 |
2006年 | 86篇 |
2005年 | 81篇 |
2004年 | 71篇 |
2003年 | 68篇 |
2002年 | 63篇 |
2001年 | 63篇 |
2000年 | 53篇 |
1999年 | 73篇 |
1998年 | 225篇 |
1997年 | 155篇 |
1996年 | 92篇 |
1995年 | 70篇 |
1994年 | 56篇 |
1993年 | 58篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 20篇 |
1986年 | 24篇 |
1985年 | 26篇 |
1984年 | 18篇 |
1983年 | 18篇 |
1982年 | 27篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 19篇 |
1976年 | 29篇 |
1975年 | 7篇 |
1974年 | 6篇 |
排序方式: 共有2559条查询结果,搜索用时 15 毫秒
1.
2.
N Usui S Kamata S Ishikawa T Sawai H Okuyama K Imura A Okada 《Canadian Metallurgical Quarterly》1996,31(2):258-262
Bone marrow examination revealed a lipid-laden histiocytosis in seven patients undergoing long-term total parenteral nutrition necessitated by extensive short-bowel surgical resection. Clinical abnormalities occurred during this treatment which required bone marrow examination. These included hepatosplenomegaly and peripheral blood cytopenia; the median time to the detection of these abnormalities was 64 months. The most striking change within the bone marrow was the presence of many pigment-laden histiocytes which had the typical morphology of sea-blue histiocytes seen in the so-called idiopathic sea-blue histiocyte syndrome. The occurrence of sea-blue histiocytosis in the bone marrow in association with long-term parenteral nutrition for short-bowel syndrome has not, to our knowledge, been reported previously and should now be considered in the differential diagnosis of bone marrow sea-blue histiocytosis. 相似文献
3.
Michio Kumagai Kanako Ishikawa Jiao Chunmeng 《Lakes & Reservoirs: Research and Management》2002,7(4):345-348
We have examined two aspects of the dynamics and biogeochemical significance of the physical environment in Lake Biwa. One is the horizontal distribution of cyanobacteria as it relates to the ‘first gyre’ in the north basin of Lake Biwa. We could easily measure the first gyre using a vessel‐mounted acoustic doppler currents profiler. We were able to quantify the dynamics of the horizontal and vertical structure of currents and water temperature of this gyre. The first gyre did not remain at a fixed position; it moved north and south according to the growth of the gyre. This may play a role in the redistribution of cyanobacteria from place to place in the north basin. The second important environmental dynamic we measured was oxygen consumption rates from 1994 to 2000. We found that the minimum oxygen concentration in the hypolimnion has a clear inverse relationship with the apparent oxygen consumption rates in the 80–85 m depth layer. As a reduction in oxygen concentration in the hypolimnion can have a serious impact on benthic organisms, we concluded that the Lake Biwa environment should be monitored carefully and systematically. 相似文献
4.
5.
The so called Geographical Information System (GIS) is one of the basic tools for wide range of public health applications. We had developed a general purpose GIS and applied it to represent geographical distribution of patients of the bacterium E. coli O-157 which bursted out in Japan last early summer particularly at Sakai City in Osaka Prefecture. The patient record have been supplied from the Food Safety Office of the Ministry of Health and Welfare. These records were handled by EXCEL. The basic geographical data was constructed from the map data provided by Japan Geographical Survey Institute, and ArcView 2 was used as the map system. The maps were converted to Graphics Interchange Format (GIF) files and put on our Web server. 相似文献
6.
N Mamiya JR Goldenring Y Tsunoda IM Modlin K Yasui N Usuda T Ishikawa A Natsume H Hidaka 《Canadian Metallurgical Quarterly》1993,195(2):608-615
A novel Ca2+/calmodulin-dependent protein kinase II (CaM Kinase II) inhibitor, KN-93 potently inhibits gastric acid secretion from parietal cells. As previously reported (1), treatment of parietal cells with a selective inhibitor of CaM kinase II, KN-62 resulted in the inhibition of cholinergic-stimulated rabbit parietal cell secretion, whereas it failed to inhibit the histamine and forskolin response. In contrast effects of carbachol, histamine and forskolin were significantly inhibited by KN-93 with an IC50 of 0.15, 0.3 and 1 microM, respectively; these effects occurred without any changes in intracellular cyclic AMP and Ca2+ levels. In the present study we investigated the mechanism by which KN-93 acts upon the acid-secreting machinery of gastric parietal cells. Neither redistribution of the proton pump activity nor the morphological transformation were affected by KN-93. The drug only weakly inhibited the H+, K(+)-ATPase activity but strongly dissipated the proton gradient formed in the gastric membrane vesicles and reduced the volume of luminal space. Thus KN-93 acts at pH gradient formation whereas KN-62 acts only at CaM Kinase II. 相似文献
7.
Toru Ikegami Hideyuki Negishi Dai Kitamoto Keiji Sakaki Tomohiro Imura Masayoshi Okamoto Yasushi Idemoto Nobuyuki Koura Tsuneji Sano Kenji Haraya Hiroshi Yanagishita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(4):381-387
In order to produce highly concentrated bioethanol by pervaporation using an ethanol‐permselective silicalite membrane, techniques to suppress adsorption of succinic acid, which is a chief by‐product of ethanol fermentation and causes the deterioration in pervaporation performance, onto the silicalite crystals was investigated. The amount adsorbed increased as the pH of the aqueous succinic acid solution decreased. The pervaporation performance also decreased with decreasing pH when the ternary mixtures of ethanol/water/succinic acid were separated. Using silicalite membranes individually coated with two types of silicone rubber, pervaporation performance was significantly improved in the pH range of 5 to 7, when compared with that of non‐coated silicalite membranes in ternary mixtures of ethanol/water/succinic acid. Moreover, when using a silicalite membrane double‐coated with the two types of silicone rubber, pervaporation performance was stabilized at lower pH values. In the separation of bioethanol by pervaporation using the double‐coated silicalite membrane, removal of accumulated substances having an ultraviolet absorption maximum at approximately 260 nm from the fermentation broth proved to be vital for efficient pervaporation. Copyright © 2005 Society of Chemical Industry 相似文献
8.
A novel dynamic survivable routing in WDM optical networks with/without sparse wavelength conversion
Vinh Trong Le Xiaohong Jiang Son Hong Ngo Susumu Horiguchi Yasushi Inoguchi 《Optical Switching and Networking》2006,3(3-4):173-190
In this paper, we study the dynamic survivable routing problem, both in optical networks without wavelength conversion and in optical networks with sparse wavelength conversion, and propose a novel hybrid algorithm for it based on the combination of mobile agents technique and genetic algorithms (GA). By keeping a suitable number of mobile agents in the network to cooperatively explore the network states and continuously report cycles (that are formed by two disjoint-link routes) into the routing tables, our new hybrid algorithm can promptly determine the first population of cycles for a new request based on the routing table of its source node, without the time consuming process associated with current GA-based lightpath protection schemes. We further improve the performance of our algorithm by introducing a more advanced fitness function that is suitable for both the above networks. Extensive simulation studies on the ns-2 network simulator show that our hybrid algorithm achieves a significantly lower blocking probability than the conventional survivable routing algorithms for all the cases we studied. 相似文献
9.
10.
Usami K. Igarashi M. Minami F. Ishikawa T. Kanzawa M. Ichida M. Nogami K. 《Solid-State Circuits, IEEE Journal of》1998,33(3):463-472
This paper describes an automated design technique to reduce power by making use of two supply voltages. The technique consists of structure synthesis, placement, and routing. The structure synthesizer clusters the gates off the critical paths so as to supply the reduced voltage to save power. The placement and routing tool assigns either the reduced voltage or the unreduced one to each row so as to minimize the area overhead. The reduced supply, voltage is also exploited in a clock tree to reduce power. Combining these techniques together, we applied it to a media processor chip. The combined technique reduced the power by 47% in random-logic modules and by 73% in the clock tree, while keeping the performance 相似文献