全文获取类型
收费全文 | 289篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
298篇 |
出版年
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2015年 | 4篇 |
2013年 | 9篇 |
2012年 | 5篇 |
2011年 | 13篇 |
2010年 | 19篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 26篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 7篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1959年 | 6篇 |
1958年 | 18篇 |
1957年 | 19篇 |
1956年 | 13篇 |
1955年 | 22篇 |
1954年 | 13篇 |
1953年 | 9篇 |
1952年 | 12篇 |
1951年 | 4篇 |
1950年 | 9篇 |
1949年 | 3篇 |
1948年 | 2篇 |
1947年 | 1篇 |
1946年 | 2篇 |
排序方式: 共有298条查询结果,搜索用时 15 毫秒
1.
2.
MICHAEL M. J. FISCHER 《American anthropologist》2006,108(2):440-441
Commons + Borderlands: Working Papers on Interdisciplinarity, Accountability and the Flow of Knowledge . Marilyn Strathern. Wantage, Oxfordshire: Sean Kingston Publishing, 2004. 102 pp. 相似文献
3.
KURT C. VERCAUTEREN MICHAEL J. LAVELLE NATHAN W. SEWARD JUSTIN W. FISCHER GREGORY E. PHILLIPS 《The Journal of wildlife management》2007,71(5):1594-1602
Abstract: Direct and indirect contact between wild and farmed cervids along perimeter fences may play a role in transmission of diseases like chronic wasting disease (CWD), but no studies have quantified such interactions. At 9 high-fenced commercial elk (Cervus elaphus) farms in Colorado, USA, during October 2003 to January 2005, we used animal-activated video to estimate rates of fence-line use by wild cervids, rates of direct contact between farmed and wild cervids, and probability of direct contact when wild cervids were present. We recorded 8-fold-more wild elk per unit time than mule deer (Odocoileus hemionus) at fence lines. Depending on site, we recorded 0.66 to 46.90 wild elk per 1,000 hours of camera monitoring. We documented 77 interactions between wild and farmed elk involving naso-oral contact and no contact between wild mule deer and farmed elk. Rate of direct contact ranged from 0.00 to 1.92 direct contacts per 1,000 hours of camera monitoring among sites. Given recorded presence of wild elk, estimated probability of observing direct contact during a 2-minute video recording ranged from 0.00 to 0.11 among sites. Risk of direct contact was about 3.5 times greater for single woven-wire fence compared with offset electric fence attached to a single woven-wire fence. We observed no direct contact through double woven-wire fences. Because little is currently known about infection rates associated with infection mechanisms, we cannot infer a level of CWD infection risk from our results, but some form of double fencing should reduce potential for direct and indirect transmission of disease into or out of elk farms. 相似文献
4.
5.
6.
7.
8.
9.
10.
1. Over the course of this 17‐month study, we assessed the potential loss of plankton (bacteria, algae, heterotrophic flagellates) to consumers (ciliates and rotifers) within mature biofilms established on natural substrata exposed to the main current of the River Rhine (Germany). Once a month, in flow cells in a bypass system to the River Rhine, we measured the clearance rates of the biofilm‐associated consumers on the different groups within the natural plankton. 2. Ciliates were the most dominant consumers, among which planktivorous groups, particularly peritrichs and (in spring and summer) heterotrichs dominated. Consumer biomass varied with season, with the highest density occurring directly after the appearance of the phytoplankton spring peak. 3. Clearance rates on plankton ranged from 96 to 565 L m?2 d?1 for bacteria and 66–749 L m?2 d?1 for algae, with a preference for algae in summer and for bacteria in winter. This pattern coincided with seasonal changes in the structures of the grazer communities. The consumers (both ciliates and rotifers with total standing stocks ranging between 19 and 572 mg C m?2) imported a substantial amount of organic matter (between 15 and 137 mg C m?2 d?1) into the biofilm. 4. These results highlight the potential importance of consumers in the biofilm as a trophic link between the plankton and the benthos, a function that has hitherto mostly been attributed to filter‐feeding bivalves. In contrast to bivalves, the biofilm‐dwelling consumers show a more dynamic response towards the plankton density and composition. Such dynamic components need to be considered when estimating total plankton consumption by the benthos. 相似文献