全文获取类型
收费全文 | 849537篇 |
免费 | 89161篇 |
国内免费 | 591篇 |
出版年
2018年 | 12218篇 |
2017年 | 11611篇 |
2016年 | 13457篇 |
2015年 | 14570篇 |
2014年 | 16816篇 |
2013年 | 23819篇 |
2012年 | 28498篇 |
2011年 | 32548篇 |
2010年 | 22903篇 |
2009年 | 21228篇 |
2008年 | 28281篇 |
2007年 | 30090篇 |
2006年 | 23139篇 |
2005年 | 23165篇 |
2004年 | 22687篇 |
2003年 | 21934篇 |
2002年 | 21050篇 |
2001年 | 38486篇 |
2000年 | 38759篇 |
1999年 | 30533篇 |
1998年 | 10437篇 |
1997年 | 10865篇 |
1996年 | 10221篇 |
1995年 | 9854篇 |
1994年 | 9579篇 |
1993年 | 9386篇 |
1992年 | 24852篇 |
1991年 | 24108篇 |
1990年 | 23467篇 |
1989年 | 22857篇 |
1988年 | 21208篇 |
1987年 | 19797篇 |
1986年 | 18336篇 |
1985年 | 18159篇 |
1984年 | 15087篇 |
1983年 | 12587篇 |
1982年 | 9555篇 |
1981年 | 8517篇 |
1980年 | 7972篇 |
1979年 | 13517篇 |
1978年 | 10510篇 |
1977年 | 9447篇 |
1976年 | 8554篇 |
1975年 | 9530篇 |
1974年 | 10139篇 |
1973年 | 10052篇 |
1972年 | 9428篇 |
1971年 | 8586篇 |
1970年 | 6999篇 |
1969年 | 6743篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
The occurrence of microfloral components on medicated and non-medicated swine and chicken feed pellets and crumbles, produced in a Manitoba feed mill between June 1991 and October 1992, was determined. Addition of medicates to feeds generally decreased bacterial incidence and increased that of Eurotium spp. fungi. The effect was less pronounced when copper sulphate was added to medicated swine feeds.Contribution No. 1662. 相似文献
992.
A. A. Romanyukha M. O. Degteva V. P. Kozheurov A. Wieser P. Jacob E. A. Ignatiev M. I. Vorobiova 《Radiation and environmental biophysics》1996,35(4):305-310
During 1949–1956, about 76 × 106 m3 of radioactive liquid waste containing a total activity of 1017 Bq was discharged into the Techa River by the first Russian industrial nuclear facility Mayak. As a consequence, the population living in the river valley received considerable internal and external radiation doses. The results of a first application of electron paramagnetic resonance (EPR) of tooth enamel for a retrospective individual dose evaluation of the residents of the Techa riverside are presented. Three main contributions to the dose absorbed in tooth enamel have been considered: external exposure mainly from the Techa River sediments, internal exposure mainly due to 90Sr; and background radiation including all other sources of exposure except the Techa River. The teeth of 86 inhabitants of the town Kamensk-Uralskii were analysed to determine the age-dependent contribution of the background radiation to the enamel dose. For 22 residents of the middle and lower Techa riverside, measurements of the 90Sr whole-body content and EPR measurements of the absorbed dose in enamel were used to establish a correlation between these two quantities. Finally, absorbed doses in the enamel of five residents of the upper Techa riverside were determined by the EPR method. Contributions of the background radiation and the internal 90Sr contamination were subtracted to determine the external exposure of the residents. 相似文献
993.
994.
995.
996.
997.
998.
John W. Duggan M.S. Clifford J. Bruell Ph.D. David K. Ryan Ph.D. 《Soil & Sediment Contamination》1994,3(2):159-182
In this article the conditions that govern surfactant‐enhanced emulsification and mobilization of petroleum hydrocarbons in soil are reviewed. The effect of soil properties, groundwater constituents, and differing surfactant solutions on the emulsification process is discussed. A constant head soil flushing apparatus used to characterize surfactant‐enhanced mobilization of m‐xylene is described. Data showing the effect of surfactant‐enhanced mobilization on m‐xylene removal efficiency in washed sand is presented. Flushing solutions were used at concentrations from below to well above the critical micelle concentration (CMC) of the surfactants used. Removal efficiencies are shown to vary with surfactant concentration and with surfactant type. Flushing solutions of anionic, nonionic, and anionic/nonionic surfactant mixtures were evaluated. 相似文献
999.
1000.