全文获取类型
收费全文 | 445180篇 |
免费 | 4100篇 |
国内免费 | 648篇 |
专业分类
电工技术 | 7551篇 |
综合类 | 340篇 |
化学工业 | 71967篇 |
金属工艺 | 21665篇 |
机械仪表 | 15354篇 |
建筑科学 | 9034篇 |
矿业工程 | 4519篇 |
能源动力 | 8484篇 |
轻工业 | 32628篇 |
水利工程 | 6032篇 |
石油天然气 | 15372篇 |
武器工业 | 55篇 |
无线电 | 41078篇 |
一般工业技术 | 96700篇 |
冶金工业 | 71736篇 |
原子能技术 | 14687篇 |
自动化技术 | 32726篇 |
出版年
2021年 | 4239篇 |
2019年 | 4089篇 |
2018年 | 7532篇 |
2017年 | 7775篇 |
2016年 | 8226篇 |
2015年 | 4636篇 |
2014年 | 8060篇 |
2013年 | 18398篇 |
2012年 | 11956篇 |
2011年 | 15420篇 |
2010年 | 12392篇 |
2009年 | 13729篇 |
2008年 | 14237篇 |
2007年 | 14093篇 |
2006年 | 11962篇 |
2005年 | 10489篇 |
2004年 | 10241篇 |
2003年 | 9916篇 |
2002年 | 9908篇 |
2001年 | 9625篇 |
2000年 | 9442篇 |
1999年 | 8853篇 |
1998年 | 18663篇 |
1997年 | 13815篇 |
1996年 | 10629篇 |
1995年 | 8471篇 |
1994年 | 7705篇 |
1993年 | 7718篇 |
1992年 | 6379篇 |
1991年 | 6194篇 |
1990年 | 6452篇 |
1989年 | 6261篇 |
1988年 | 6018篇 |
1987年 | 5631篇 |
1986年 | 5583篇 |
1985年 | 6138篇 |
1984年 | 5927篇 |
1983年 | 5565篇 |
1982年 | 5251篇 |
1981年 | 5347篇 |
1980年 | 5274篇 |
1979年 | 5381篇 |
1978年 | 5569篇 |
1977年 | 5881篇 |
1976年 | 7093篇 |
1975年 | 5031篇 |
1974年 | 5038篇 |
1973年 | 5153篇 |
1972年 | 4494篇 |
1971年 | 4143篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
G. I. Glazov A. M. Garaiev R. V. Timerkhanov 《Chemistry and Technology of Fuels and Oils》2003,39(1-2):26-53
A series of small–capacity units has recently been constructed in regions of oil field development and crude oil and gas condensate production to satisfy the requirements for such petroleum products as naphtha, diesel fuel, kerosene, and boiler fuel and to reduce costs for delivery of these products. There are almost no data in the technical literature, particularly in periodicals, on the construction and operation of small–capacity units. We attempt to generalize the experience of Orgeneftekhimzavody Trust in this area. We hope that this experience will be useful to specialists in the development and management of small–capacity plants. 相似文献
22.
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
23.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献
24.
A. V. Butko A. A. Klimov S. A. Nikitov Yu. A. Filimonov 《Journal of Communications Technology and Electronics》2006,51(8):944-947
The magneto-optical Kerr effect for red (628 nm) and green (532 nm) light is used to study magnetization processes in 2D magnonic crystals obtained by etching pits with the diameter D ≈ 32 μm to a depth of t ≤ 2 μm in a 16.1-μm-thick film of yttrium iron garnet (YIG). Hysteresis loops obtained in the case of the inplane crystal magnetization at 628 nm are characterized by lower saturation fields H s and higher remanent magnetizations than those obtained at 532 nm, a result that is attributed to different absorption coefficients of the YIG film at these wavelengths. This difference between the magnetization curves reflects the fact that the magnonic-crystal surface probed with the green light makes a greater contribution to the magneto-optical Kerr effect. Therefore, the green light is more sensitive to the demagnetizing fields, which govern magnetization processes in the magnonic crystals. 相似文献
25.
26.
S. V. Doronin 《Chemical and Petroleum Engineering》2006,42(7-8):461-464
Current features are considered in the calculation of carrying capacities for constructions in engineering plant (EP). Methods
and algorithms are described for EP calculations with comprehensive incorporation of the effects from technological and working
defects on the behavior of structures under standard and emergency conditions.
__________
Translated from Khimicheskoe i Neftegazovoe Mashinostroenie, No. 8, pp. 38–40, August, 2006. 相似文献
27.
Phase equilibria involving spinel solid solutions, delafossite, and hematite in the Fe–Cu–O system are studied by emf measurements in solid-electrolyte galvanic cells. The results demonstrate that, above 1250 K, Fe3O4 and CuFe2O4 form a continuous series of solid solutions. At lower temperatures, the solid solution disproportionates with the formation of delafossite and Fe2O3, and two spinel solid solutions appear: one based on Fe3O4 and the other based on Cu2FeO4. The compositions of the spinel phases in equilibrium with delafossite and Fe2O3 are determined in the range 1100–1250 K. 相似文献
28.
V. N. Pavlechko 《Journal of Engineering Physics and Thermophysics》2004,77(1):115-120
Relations for determining a motive force in a complex model of mass transfer as applied to concurrent, countercurrent, and cross motion of the vapor and liquid phases have been introduced. These forces have been compared for different forms of organization of the flow, and their comparison with similar quantities from the known Murphree and Hausen models is presented. 相似文献
29.
Thomas S. Lowry John C. Bright Murray E. Close Christina A. Robb Paul A. White Stewart G. Cameron 《国际水资源开发杂志》2003,19(4):579-592
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps. 相似文献
30.
Introduces the current issue of the American Psychologist, which examines the ramifications of the Brown vs. Board of Education decision and its sequelae over the last 50 years, with a special focus on the mixed role of psychological research and practice. Despite the great strides toward a more just society since May 17, 1954, inequities remain in schooling, in social relations, and in economic opportunity. How will history judge American psychology 50 years from now vis-a-vis the possibilities it helped create via Brown? The articles in this special issue suggest several important directions of research and action our field will need to take if the verdict of history is to be a positive one. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献