全文获取类型
收费全文 | 111141篇 |
免费 | 2017篇 |
国内免费 | 743篇 |
专业分类
电工技术 | 1806篇 |
综合类 | 76篇 |
化学工业 | 18343篇 |
金属工艺 | 4167篇 |
机械仪表 | 3365篇 |
建筑科学 | 3624篇 |
矿业工程 | 618篇 |
能源动力 | 2914篇 |
轻工业 | 9248篇 |
水利工程 | 1277篇 |
石油天然气 | 2426篇 |
武器工业 | 46篇 |
无线电 | 9695篇 |
一般工业技术 | 22618篇 |
冶金工业 | 19028篇 |
原子能技术 | 2887篇 |
自动化技术 | 11763篇 |
出版年
2022年 | 1024篇 |
2021年 | 1657篇 |
2020年 | 1244篇 |
2019年 | 1386篇 |
2018年 | 2322篇 |
2017年 | 2256篇 |
2016年 | 2584篇 |
2015年 | 1684篇 |
2014年 | 2582篇 |
2013年 | 5913篇 |
2012年 | 4015篇 |
2011年 | 4883篇 |
2010年 | 3993篇 |
2009年 | 4158篇 |
2008年 | 4385篇 |
2007年 | 4306篇 |
2006年 | 3754篇 |
2005年 | 3337篇 |
2004年 | 2999篇 |
2003年 | 2894篇 |
2002年 | 2748篇 |
2001年 | 2372篇 |
2000年 | 2222篇 |
1999年 | 2159篇 |
1998年 | 4277篇 |
1997年 | 3193篇 |
1996年 | 2494篇 |
1995年 | 2086篇 |
1994年 | 1853篇 |
1993年 | 1866篇 |
1992年 | 1487篇 |
1991年 | 1340篇 |
1990年 | 1482篇 |
1989年 | 1440篇 |
1988年 | 1260篇 |
1987年 | 1229篇 |
1986年 | 1188篇 |
1985年 | 1347篇 |
1984年 | 1189篇 |
1983年 | 1076篇 |
1982年 | 963篇 |
1981年 | 972篇 |
1980年 | 927篇 |
1979年 | 915篇 |
1978年 | 865篇 |
1977年 | 997篇 |
1976年 | 1135篇 |
1975年 | 772篇 |
1974年 | 722篇 |
1973年 | 708篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Ifechukwu E. Adieze Justina C. Orji Rose N. Nwabueze G.O.C. Onyeze 《The International journal of environmental studies》2013,70(3):490-500
Responses to hydrocarbon stress of four tropical plants Panicum maximum, Zea mays, Centrosema sp. and Pueraria sp. grown in crude oil contaminated soils (1%, 5% and 10% w/w) were evaluated in a green house. Plants’ percentage survival, shoot heights, biomass development, and phytotoxicity susceptibility were used as indicators of growth, stress response and hydrocarbon tolerance. Relative to control, shoot heights and biomass of plants reduced with increasing hydrocarbon concentration, but 1% w/w oil-in-soil, stimulated shoot heights (5.9% and 6.4%) and weights (21.9% and 2.3%) in P. maximum and Centrosema sp. respectively. P. maximum tolerated the contaminant stress with biomass yields of 113% and 57% of control respectively in 1% and 10% w/w oil-in-soil. All the plants had 100% survival in 1% w/w, but considerably reduced survival in 10% w/w oil-in-soil. These results show that P. maximum has great potential for phytoremediation of petroleum contaminated soil. 相似文献
42.
Martin A. Stapanian David W. Shea 《The International journal of environmental studies》2013,70(1-2):45-56
The effects of Lignosite#rm lignosulfonate, a refined lignosulfonate product that is obtained from the sulfite pulping process, on growth and survival of plants were investigated. Following applications of 0, 7500, 15,000 and 22,500 cm3#shm2 to 32 plots within a forest plantation, the following were monitored: (1) live aboveground biomass of vascular plants, (2) growth of Douglar fir (Pseudotsuga menziesii) and (3) lignosulfonate migration through the soil profile. Live aboveground biomass of woody vegetation was not affected, and that of herbaceous plants was significantly decreased only at the two greatest application rates. Growth of the Douglas fir trees was not significantly affected. Lignosulfonates disappeared from the soil profile at the same rate regardless of initial concentration. Although it is not practical to use this material as a herbicide in western Washington, land application of lignosulfonates may be environmentally more attractive than traditional disposal methods. 相似文献
43.
44.
45.
46.
47.
48.
49.
David Cushman Coyle 《Journal of the American Planning Association. American Planning Association》2013,79(2):35-37
Your City Tomorrow. By Guy Greer. Macmillan Company. 1947. 210 pages. $2.50. The Case for Regional Planning with Special Reference to New England. By the Directive Committee on Regional Planning, Yale University. Yale University Press. 1947. 94 pages with color illustrations. $10.00. American Planning: Past-Present-Future. By Cleveland Rodgers. Harper and Bros. 1947. 290 pages. $3.00. Public Control of Highway Access and Roadside Development. Reported by David R. Levin. United States Government Printing Office. 1947. 154 pages. 35 cents. Metropolis in Maps. Bureau of Research Municipal Government, Graduate School of Public Administration, Harvard University. Social Housing and its Advancement in Zurich, 1942-45 (Der Sociale Wohnbau und Seine Foerdenrng in Zurich) Published by Hochbauamt der Stadt Zurich, Switzerland. 113 pages with plans, photographs, tables. $5.00. Obtainable through the Architectural Publishing Book Company, New York City 相似文献
50.
David Stocker et al. 《Vernacular Architecture》2013,44(1):40-65
Based on research undertaken by RUBL, a new building-recording group in Lincolnshire, this contribution originates in the observation that there are a very few standing timber-framed buildings in the county’s Middle Trent Valley. The paper is the first from a larger project exploring this absence. It addresses the suggestion that, although there were once similar numbers of vernacular buildings of this type as elsewhere in the north-east Midlands, this part of Lincolnshire was so greatly affected by a great rebuilding following enclosure between c. 1750 and c. 1850 that virtually all earlier box-framed structures were replaced in brick. Preliminary survey by the group suggests that this may be true, but it also reveals that some members of this earlier generation of box-framed buildings may survive disarticulated, as re-used timbers in those enclosure-period farmsteads that replaced them. Consequently, the group has undertaken a detailed analysis of the timbers re-used in the enclosure-period farmhouse at Thorpe-on-the-Hill in order to assess techniques for reconstructing the frames of predecessor buildings. Following extensive recording work, the outlines of two closely connected predecessor structures have been reconstructed and dated - through techniques including dendrochronology - to the mid-fifteenth and early sixteenth centuries. It is suggested that they were both ranges from the previous Manor Farm House, which occupied the same footprint as that still standing. 相似文献