全文获取类型
收费全文 | 8362篇 |
免费 | 807篇 |
国内免费 | 1篇 |
出版年
2021年 | 105篇 |
2020年 | 70篇 |
2019年 | 96篇 |
2018年 | 90篇 |
2017年 | 75篇 |
2016年 | 121篇 |
2015年 | 229篇 |
2014年 | 235篇 |
2013年 | 318篇 |
2012年 | 397篇 |
2011年 | 393篇 |
2010年 | 266篇 |
2009年 | 232篇 |
2008年 | 357篇 |
2007年 | 312篇 |
2006年 | 304篇 |
2005年 | 319篇 |
2004年 | 326篇 |
2003年 | 281篇 |
2002年 | 290篇 |
2001年 | 166篇 |
2000年 | 136篇 |
1999年 | 153篇 |
1998年 | 113篇 |
1997年 | 103篇 |
1996年 | 107篇 |
1995年 | 76篇 |
1994年 | 79篇 |
1993年 | 86篇 |
1992年 | 135篇 |
1991年 | 117篇 |
1990年 | 131篇 |
1989年 | 114篇 |
1988年 | 105篇 |
1987年 | 101篇 |
1986年 | 104篇 |
1985年 | 126篇 |
1984年 | 102篇 |
1983年 | 103篇 |
1982年 | 97篇 |
1981年 | 89篇 |
1980年 | 94篇 |
1979年 | 68篇 |
1978年 | 79篇 |
1977年 | 89篇 |
1976年 | 64篇 |
1974年 | 92篇 |
1973年 | 68篇 |
1972年 | 82篇 |
1971年 | 66篇 |
排序方式: 共有9170条查询结果,搜索用时 15 毫秒
21.
Arash Masbough Kevin Frankowski Ken J. Hall Sheldon J.B. Duff 《Ecological Engineering》2005,25(5):552
Percolation of rainfall through woodwaste piles leaches natural chemicals from the wood residuals that can have adverse impacts on the environment. A study was conducted on a woodwaste storage site, adjacent to the Lower Fraser River, near Mission, BC, Canada. The objective of this research was to evaluate the effectiveness of constructed wetland for treatment of this woodwaste leachate. The leachate was characterized by high oxygen demand, tannin and lignin, and volatile fatty acids (VFAs), but low pH and nutrients. Diluted leachate passed through six pilot-scale wetland cells, four planted with cattail (Typha latifolia) and two unplanted controls, with a hydraulic retention time of 7 days and an average depth of 40 cm. Nutrient addition and pH adjustments were made to improve contaminant removal. Reductions in contaminants were consistently achieved, with average removals for BOD, COD, VFAs and tannin and lignin of 60, 50, 69 and 42%, respectively. Climatic conditions had an impact on the performance of the constructed wetland. Further operation of the system will help to elucidate the seasonal fluctuations. Aging of the constructed wetland system increased the treatment performance. 相似文献
22.
23.
G R Guy J Gordon R H Michell G Brown 《Biochemical and biophysical research communications》1985,131(1):484-491
Resting human tonsillar B cells were stimulated to divide by heat killed Staphylococcus aureus Cowan strain 1 which was shown to induce hydrolysis of phosphatidylinositol 4, 5-bisphosphate known to give rise to diacylglycerol and an increase in cytosolic free calcium. Addition of the diacylglycerols, 1-oleoyl-2 acetyl glycerol or sn-1, 2-dioctanoylglycerol, together with the calcium ionophore ionomycin to B cell cultures induced marked cell proliferation whereas these agents were ineffective when used alone. Both diacylglycerols were shown to compete with [3H] phorbol 12,13 dibutyrate in binding to protein kinase C. These data support the hypothesis that synergism between cytosolic calcium and endogenous diacylglycerol, which activates protein kinase C, is involved in signal transduction in the proliferation of human B cells. 相似文献
24.
25.
26.
Z discs were isolated from Lethocerus flight muscle by removing the contractile proteins from myofibrils with a solution of high ionic strength. The protein composition of the Z discs was analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis; the major proteins were alpha-actinin, actin and tropomyosin. Z lines were selectively removed from intact myofibrils by digestion with crude lipase and chymotrypsin, but not by purified lipase. 相似文献
27.
28.
29.
30.