全文获取类型
收费全文 | 1350篇 |
免费 | 29篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 106篇 |
地球物理 | 289篇 |
地质学 | 461篇 |
海洋学 | 113篇 |
天文学 | 250篇 |
综合类 | 3篇 |
自然地理 | 130篇 |
出版年
2020年 | 17篇 |
2019年 | 11篇 |
2018年 | 21篇 |
2017年 | 15篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 56篇 |
2012年 | 45篇 |
2011年 | 57篇 |
2010年 | 48篇 |
2009年 | 57篇 |
2008年 | 59篇 |
2007年 | 60篇 |
2006年 | 49篇 |
2005年 | 44篇 |
2004年 | 65篇 |
2003年 | 49篇 |
2002年 | 50篇 |
2001年 | 28篇 |
2000年 | 26篇 |
1999年 | 21篇 |
1998年 | 13篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 27篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1984年 | 35篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 21篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 16篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1972年 | 9篇 |
1970年 | 13篇 |
排序方式: 共有1382条查询结果,搜索用时 0 毫秒
111.
Marine mussels accumulate the carcinogen benzo(a)pyrene from contaminated environments. Baseline studies in California indicate that levels of the carcinogen in mussels are at or near zero, except in areas of human activity. This finding runs counter to previous suggestions that benzo(a)pyrene is widely distributed in marine organisms. 相似文献
112.
113.
114.
The number of bacteria in sediments of a North Carolina salt marsh was determined by direct counts with epifluorescent illumination and acridine orange stain. Cell number decreased from 8.36–10.90×109 cells/cm3 of sediment at the surface to 2.19–2.58×109 cells/cm3 of sediment at a depth of 20 cm. No significant difference was found among four stations located on a transect which crossed the marsh and spanned subtidal to intertidal sediments. 相似文献
115.
A reevaluation of the entropy and Gibbs free energy of formation of Al3+(aq) yields ?308 ± 15 J/K·mol and 489.4 ± 1.4kj/mol for S0298 and respectively. The standard electrode potential for aluminum is 1.691 ± 0.005 volts. 相似文献
116.
117.
Direct observations or deduced analysis indicate clearly that formation of intense fluxes of relativistic electrons is an important ingredient in the evolution of numerous active magnetized plasma systems. Examples of relativistic electron energization include the recovery phase of a planetary magnetic storm, post solar flare coronal activity and the afterglow of gamma ray bursts. It is suggested that there exists a universal mechanism, which may explain electron energization at the vastly different magnetized plasma environments. The favorite configuration consists of an inhomogeneous magnetic field anchored at a given magnetic structure and excitation of whistler waves due to external injection of low-energy non-isotropic electrons. The energization proceeds as a bootstrap process due to interaction with the propagating whistler waves along the inhomogeneous magnetic field. 相似文献
118.
119.
120.
Fine‐scale diet of the Australian sea lion (Neophoca cinerea) using DNA‐based analysis of faeces
下载免费PDF全文
![点击此处可从《Marine Ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Kristian J. Peters Kathy Ophelkeller Nathan J. Bott Bruce E. Deagle Simon N. Jarman Simon D. Goldsworthy 《Marine Ecology》2015,36(3):347-367
We applied DNA‐based faecal analysis to determine the diet of female Australian sea lions (n = 12) from two breeding colonies in South Australia. DNA dietary components of fish and cephalopods were amplified using the polymerase chain reaction and mitochondrial DNA primers targeting the short (~100 base pair) section of the 16S gene region. Prey diversity was determined by sequencing ~50 amplicons generated from clone libraries developed for each individual. Faecal DNA was also combined and cloned from multiple individuals at each colony and fish diversity determined. Diets varied between individuals and sites. Overall, DNA analysis identified a broad diversity of prey comprising 23 fish and five cephalopod taxa, including many species not previously described as prey of the Australian sea lion. Labridae (wrasse), Monacanthidae (leatherjackets) and Mullidae (goat fish) were important fish prey taxa. Commonly identified cephalopods were Octopodidae (octopus), Loliginidae (calamary squid) and Sepiidae (cuttlefish). Comparisons of fish prey diversity determined by pooling faecal DNA from several samples provided a reasonable but incomplete resemblance (55–71%) to the total fish diversity identified across individual diets at each site. Interpretation of diet based on the recovery of prey hard‐parts identified one cephalopod beak (Octopus sp.) and one fish otolith (Parapriacanthus elongatus). The present study highlights the value of DNA‐based analyses and their capabilities to enhance information of trophic interactions. 相似文献