全文获取类型
收费全文 | 626189篇 |
免费 | 7309篇 |
国内免费 | 2194篇 |
专业分类
电工技术 | 10766篇 |
综合类 | 2742篇 |
化学工业 | 92021篇 |
金属工艺 | 28034篇 |
机械仪表 | 20960篇 |
建筑科学 | 13471篇 |
矿业工程 | 4332篇 |
能源动力 | 15755篇 |
轻工业 | 41325篇 |
水利工程 | 7547篇 |
石油天然气 | 13372篇 |
武器工业 | 34篇 |
无线电 | 72470篇 |
一般工业技术 | 128669篇 |
冶金工业 | 102176篇 |
原子能技术 | 13529篇 |
自动化技术 | 68489篇 |
出版年
2021年 | 5216篇 |
2020年 | 3981篇 |
2019年 | 5079篇 |
2018年 | 22277篇 |
2017年 | 21280篇 |
2016年 | 18779篇 |
2015年 | 6360篇 |
2014年 | 9821篇 |
2013年 | 26137篇 |
2012年 | 17994篇 |
2011年 | 28874篇 |
2010年 | 23717篇 |
2009年 | 23277篇 |
2008年 | 24884篇 |
2007年 | 25500篇 |
2006年 | 16296篇 |
2005年 | 15633篇 |
2004年 | 14725篇 |
2003年 | 14668篇 |
2002年 | 13402篇 |
2001年 | 12974篇 |
2000年 | 12208篇 |
1999年 | 12498篇 |
1998年 | 31699篇 |
1997年 | 21903篇 |
1996年 | 16864篇 |
1995年 | 12491篇 |
1994年 | 11020篇 |
1993年 | 11191篇 |
1992年 | 8201篇 |
1991年 | 7863篇 |
1990年 | 7689篇 |
1989年 | 7355篇 |
1988年 | 7146篇 |
1987年 | 6236篇 |
1986年 | 6152篇 |
1985年 | 6910篇 |
1984年 | 6391篇 |
1983年 | 5863篇 |
1982年 | 5323篇 |
1981年 | 5387篇 |
1980年 | 5125篇 |
1979年 | 5056篇 |
1978年 | 5079篇 |
1977年 | 5630篇 |
1976年 | 7045篇 |
1975年 | 4473篇 |
1974年 | 4232篇 |
1973年 | 4364篇 |
1972年 | 3733篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
M Burkhardt T Kupper S Hean R Haag P Schmid M Kohler M Boller 《Water science and technology》2007,56(12):63-67
There is increasing concern about diffuse pollution of aquatic systems by biocides used in urban areas. We investigated sources and pathways of biocides significant for the pollution of storm water runoff. Main sources seem to be building envelopes, i.e. facades (paints, plasters) and roof sealing membranes. First results from a defined urban catchment drained by a separated sewer system without any agricultural activities reveal a substantial occurrence. Even after the first flush, concentrations of terbutryn, carbendazim, mecoprop as well as Irgarol 1051 and its metabolite exceeded the Swiss water quality standard of 0.1 microg/L. In laboratory experiments, leaching of mecoprop used as a root protection agent in bitumen sheets for roof waterproofing was determined. The concentrations differed in 16 different sheets two orders of magnitude, depending on the product composition. Using optimized products, it is expected to be the most efficient and sustainable way to reduce the environmental impact. To understand transport dynamics and environmental risk, further storm water events will be analyzed. Based on the ongoing project URBIC, first measures will be proposed to limit the release to surface and ground water. 相似文献
992.
993.
P M Reid A E Wilkinson K C Leung M N Jones 《Computer applications in the biosciences》1989,5(2):133-135
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River. 相似文献
994.
995.
996.
From the results reported here it is suggested that policy decisions about the potential contribution of decentralized energy supply systems to UK industrial energy requirements should be based on the suitability of individual sectors rather than averaged over all sectors. The suitability of decentralized energy sources is evaluated, based on a themodynamic match between source and demand. This suitability criterion is used to identify the most appropriate sector in manufacturing industries for the adoption of decentralized energy supply, leaving aside economic cost considerations and individual site requirements. 相似文献
997.
Survival of rotavirus on lettuce, radishes, and carrots was studied to evaluate the potential of rotavirus transmission by vegetables irrigated with wastewater. The vegetables were contaminated with rotavirus SA-11 and stored at 4°C and room temperature in covered and uncovered containers to simulate post harvest conditions. Virus decay rates were greater on radishes and carrots than lettuce. Decay rates of rotavirus on lettuce, radish, and carrot ranged from ?0·057 to ?0·479 (log10 pfu/day). Rotavirus SA-11 survived on lettuce, radish, and carrot for 25 to 30 days at 4°C but at room temperature survival was very different for the various vegetables varying from 5 to 25 days. Greatest survival was always observed on the lettuce. These data suggest that rotaviruses can survive long enough on contaminated vegetables as to be transmitted by this vehicle. 相似文献
998.
P. V. Prosuntsov S. V. Reznik 《Journal of Engineering Physics and Thermophysics》1985,49(6):1458-1462
A method is proposed for determining the thermophysical properties of translucent scattering materials in the nonsteady heating regime.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 6, pp. 977–982, December, 1985. 相似文献
999.
1000.