全文获取类型
收费全文 | 2741篇 |
免费 | 487篇 |
国内免费 | 392篇 |
专业分类
测绘学 | 102篇 |
大气科学 | 381篇 |
地球物理 | 936篇 |
地质学 | 1090篇 |
海洋学 | 432篇 |
天文学 | 3篇 |
综合类 | 147篇 |
自然地理 | 529篇 |
出版年
2024年 | 18篇 |
2023年 | 60篇 |
2022年 | 129篇 |
2021年 | 144篇 |
2020年 | 145篇 |
2019年 | 151篇 |
2018年 | 138篇 |
2017年 | 118篇 |
2016年 | 148篇 |
2015年 | 127篇 |
2014年 | 211篇 |
2013年 | 243篇 |
2012年 | 162篇 |
2011年 | 175篇 |
2010年 | 153篇 |
2009年 | 146篇 |
2008年 | 168篇 |
2007年 | 142篇 |
2006年 | 169篇 |
2005年 | 107篇 |
2004年 | 97篇 |
2003年 | 87篇 |
2002年 | 74篇 |
2001年 | 64篇 |
2000年 | 58篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 26篇 |
1996年 | 57篇 |
1995年 | 44篇 |
1994年 | 43篇 |
1993年 | 31篇 |
1992年 | 25篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1978年 | 1篇 |
排序方式: 共有3620条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
P Thoya S Pérez-Jorge GM Okemwa H Mwamlavya A Tuda N Wambiji 《African Journal of Marine Science》2020,42(1):23-33
Ringnet fishing began in the early 20th century and is practised worldwide, mainly to target nearshore pelagic species. The method was introduced to Kenya’s coastal waters by migrant fishers from Tanzania. However, the impacts of this fishing gear remain poorly assessed. We assessed the spatial distribution of ringnet fishing effort and its possible effects on ecosystem components, such as coral reefs, marine megafauna and marine protected areas, on the south coast of Kenya. We tracked 89 ringnet fishing trips made from December 2015 to January 2016 and used spatial multicriteria analysis to determine hotspots of possible environmental risks. The results showed that habitat type and bathymetric profile influenced the spatial distribution of ringnet fishing effort. Mixed seagrass and coral habitats had the highest concentration of the effort. Most of the habitats in the study area were moderately exposed to the impacts of the ringnet fishery. The study identifies high-risk areas that require spatial measures to minimise possible environmental risks of the gear both to habitats and to endangered sea turtles. 相似文献
15.
16.
17.
18.
Predation by the big brackish-water isopod Saduria entomon on two age-classes (juveniles and adults) of the small deposit-feeding amphipod Monoporeia (syn. Pontoporeia) affinis was studied at different oxygen conditions (normoxia>11 mg/l O2, and moderate hypoxia 4 mg/l O2). Vulnerability of juvenile and adult M. affinis was studied in single and mixed age-class treatments. The proportions of juveniles and adults were varied at one total numerical density. The predatory effects were measured as numbers of individuals consumed and of total biomass intake (mg ash-free dry weight). The highest predation rate (in numbers) was detected in the single-prey treatment with juvenile M. affinis, both in normoxia and moderate hypoxia. No preference for any of the two size classes was found in the treatment with equal numbers of adults and juveniles. In normoxia, the total number of prey consumed decreased with increasing proportions of adults, while intake increased in terms of biomass. In moderate hypoxia, high proportions of adults reduced the predation rate of S. entomon to such an extent that also the intake in terms of biomass was significantly negatively affected. 相似文献
19.
采用金属潜在生态危害系数和危害指数的评估方法,评价了大亚湾海域重金属对海洋生态系统的潜在危害。结果表明,大亚湾海域重金属潜在生态危害轻微,而养殖海区和近岸海区的重金属潜在生态危害则相对较重,大亚湾海域重金属的潜在生态危害较珠江口外浅海轻。 相似文献
20.
人工鱼礁工程的风险评估 总被引:1,自引:0,他引:1
对台风暴潮影响下的嵊泗海域人工鱼礁工程做了风险评估,考虑了台风暴潮中出现的大浪和风暴潮减水对鱼礁联合作用的危害。风险评估分为危险灾害识别、失效概率计算、失效后果评估、风险准则评定和风险管理决策几个主要的步骤。在失效概率的计算中采用基于应用设计点的重点抽样法随机模拟的技术,这一随机模拟技术可以广泛的应用与海洋工程结构的风险评估当中。 相似文献