全文获取类型
收费全文 | 630篇 |
免费 | 14篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 43篇 |
地球物理 | 132篇 |
地质学 | 197篇 |
海洋学 | 80篇 |
天文学 | 117篇 |
综合类 | 3篇 |
自然地理 | 66篇 |
出版年
2021年 | 5篇 |
2020年 | 9篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 18篇 |
2013年 | 34篇 |
2012年 | 11篇 |
2011年 | 26篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 25篇 |
2007年 | 18篇 |
2006年 | 12篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 26篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 27篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1971年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有653条查询结果,搜索用时 0 毫秒
651.
RW Jabado SM Al Ghais W Hamza DP Robinson AC Henderson 《African Journal of Marine Science》2016,38(2):217-232
Landing site and market surveys of sharks landed along the Arabian Gulf coast of the United Arab Emirates were undertaken between October 2010 and September 2012 to obtain biological data from this artisanal fishery. Data were collected on the size and sex of 12 482 individuals representing 30 species. Maximum sizes of Carcharhinus sorrah, C. amblyrhynchoides and Hemipristis elongata were extended by at least 300?mm total length (TL) compared with published global maxima. The size at 50% maturity was determined for males of five species and this indicated that the males of smaller shark species (<1 000 mm maximum TL) in the fishery were largely mature. For many species, including Loxodon macrorhinus and Mustelus mosis, overall sex ratios were male-biased, indicating that sexual segregation is likely in those species. Furthermore, sex ratios for several species, such as Rhizoprionodon acutus, showed differences across seasons. Overall, the landings contained a high proportion of juveniles, causing concerns about the sustainability of this fishery. Biological parameters of a number of species differed from those recorded earlier for the region, demonstrating a need for additional local data collection to support the development of management measures. 相似文献
652.
The California spiny or red rock lobster, Panulirus interruptus, is an ecologically and economically important species that has been exploited since the 1800s. No previous study in California has assessed the impacts of the recreational or commercial lobster harvest. Before the 2003–04 commercial and recreational lobster seasons, we conducted a fishery‐independent trap survey at Santa Catalina Island to document the impact of the lobster fisheries on the size structure, abundance, and sex ratios of mature P. interruptus (>65 mm carapace length (CL)). We concurrently sampled a predominantly commercially fished area, a recreationally fished area, and a 23‐year‐old invertebrate no‐take (INT) reserve. Relative to the INT reserve, legal‐size lobsters in the recreational area were similar in CL, but 31% less abundant. Legal‐size lobsters in the commercial area were 8% smaller and 70% less abundant than those in the INT reserve. The sex ratio of legal‐size lobsters, although near 50:50 in the recreational and INT reserve areas, was male‐dominated (67:33) in the commercial area. Differences in CPUE and mean CL of sub‐legal lobsters in the recreational and commercial areas suggest that factors in addition to harvesting pressure may affect these populations. Total biomass of mature lobsters in the recreational and commercial areas was 92% and 45%, respectively, of biomass in the INT reserve. Fecundity in the recreational and commercial areas was 83% and 42%, respectively, of fecundity in the INT reserve. This study provides preliminary data for future ecological studies and fisheries management evaluations. 相似文献
653.