全文获取类型
| 收费全文 | 74篇 |
| 免费 | 9篇 |
| 国内免费 | 1篇 |
专业分类
| 测绘学 | 10篇 |
| 地球物理 | 17篇 |
| 地质学 | 41篇 |
| 海洋学 | 13篇 |
| 天文学 | 2篇 |
| 自然地理 | 1篇 |
出版年
| 2024年 | 1篇 |
| 2012年 | 3篇 |
| 2011年 | 4篇 |
| 2009年 | 2篇 |
| 2008年 | 4篇 |
| 2007年 | 2篇 |
| 2006年 | 1篇 |
| 2005年 | 3篇 |
| 2004年 | 7篇 |
| 2003年 | 2篇 |
| 2002年 | 2篇 |
| 2001年 | 2篇 |
| 2000年 | 3篇 |
| 1999年 | 2篇 |
| 1998年 | 2篇 |
| 1997年 | 10篇 |
| 1996年 | 4篇 |
| 1995年 | 6篇 |
| 1994年 | 5篇 |
| 1993年 | 3篇 |
| 1992年 | 4篇 |
| 1991年 | 3篇 |
| 1990年 | 6篇 |
| 1989年 | 2篇 |
| 1982年 | 1篇 |
排序方式： 共有84条查询结果，搜索用时 46 毫秒
61.
Siberia contains several key reference sections for studies of biological and environmental evolution across the Proterozoic-Phanerozoic transition. The Platonovskaya Formation, exposed in the Turukhansk region of western Siberia, is an uppermost Proterozoic to Cambrian succession whose trace and body fossils place broad limits on the age of deposition, but do not permit detailed correlation with boundary successions elsewhere. In contrast, a striking negative carbon isotopic excursion in the lower part of the Platonovskaya Formation permits precise chemostratigraphic correlation with upper-most Yudomian successions in Siberia, and possibly worldwide. In addition to providing a tool for correlation, the isotopic excursion preserved in the Platonovskaya and contemporaneous successions documents a major biogeochemical event, likely involving the world ocean. The excursion coincides with the palaeontological breakpoint between Ediacaran- and Cambrian-style assemblages, suggesting a role for biogeochemical change in evolutionary events near the Proterozoic Cambrian boundary. 相似文献
62.
Circulating c-reactive protein (CRP) levels can be used as a bioindicator of the acute phase inflammatory response and as a possible biomarker of inflammation and neurogenic stress in vertebrates. Currently, there are no data describing the ranges of CRP levels in sharks living in different habitats, especially habitats of differing degrees of pollution. Developing antibodies against CRP is a first and critical step towards developing sensitive methods for quantifying CRP, and thus inflammatory and stress responses in sharks. Sharpnose shark, Rhizoprionodon terraenovae, serum C-reactive protein was purified sequentially over AH-sepharose 4B-PC and sepharose CL-4B columns and used to immunize balb/c mice for generating stocks of polyclonal anti-sera. Serum samples from 131 sharpnose sharks were collected from three different geographical regions along the coast of SC and GA, USA between June and November 2002. Total CRP concentrations were quantified by ELISA and found to be highest in the sharpnose shark population collected in the summer from Charleston, SC, compared to Beaufort, SC and Brunswick, GA. Seasonal comparisons indicated a higher CRP concentration in the summer of the Charleston, SC population compared to the fall. These data suggest that sharks living in the Charleston, SC harbor estuary may be exposed to a suite of pathogens or other stressors that are different than those found in the Beaufort, SC and Brunswick, GA estuaries. These data support the use of CRP as a bioindicator of health status in elasmobranchs. 相似文献
63.
The purpose of these studies was to evaluate if there were relationships between lysosomal destabilization or glutathione concentrations and gamete viability of oysters, Crassostrea virginica. Oysters were collected from field sites during the peak spawning period (May-June) during 2001 and 2002. Lysosomal destabilization rates and glutathione concentrations of hepatopancreas tissues (e.g. digestive gland) were determined. Eggs and sperm from the same adults were also used to conduct embryo development assays with reference seawater collected from a clean site, site water, and also a range of Cd concentrations (the Cd exposures were used to determine if there were differences in susceptibility to pollutants). Baseline embryo development success (e.g. percent normal development when the assays were conducted with reference seawater or site water) was related to lysosomal destabilization, but not glutathione status. However, the susceptibility of embryos to metal toxicity was related to glutathione status, i.e., sensitivity to Cd exposures increased with decreasing glutathione levels. These studies support the hypotheses that there are linkages between embryo development success and susceptibility to pollutant stress and cellular biomarker responses. These kinds of effects on reproductive success could lead to subtle but significant long-term effects on recruitment and viability of oyster populations. 相似文献
64.
65.
66.
Silicified carbonates of the late Mesoproterozoic to early Neoproterozoic Society Cliffs Formation, Baffin Island, contain distinctive microfabrics and microbenthic assemblages whose paleo-environmental distribution within the formation parallels the distribution of these elements through Proterozoic time. In the Society Cliffs Formation, restricted carbonates--including microdigitate stromatolites, laminated tufa, and tufted microbial mats--consist predominantly of synsedimentary cements; these facies and the cyanobacterial fossils they contain are common in Paleoproterozoic successions but rare in Neoproterozoic and younger rocks. Less restricted tidal-flat facies in the formation are composed of laminated microbialites dominated by micritic carbonate lithified early, yet demonstrably after compaction; these strata contain cyanobacteria that are characteristic in Neoproterozoic rocks. Within the formation, the facies-dependent distribution of microbial populations reflects both the style and timing of carbonate deposition because of the strong substrate specificity of benthic cyanobacteria. A reasonable conclusion is that secular changes in microbenthic assemblages through Proterozoic time reflect a decrease in the overall representation of rapidly lithified carbonate substrates in younger peritidal environments, as well as concomitant changes in the taphonomic window of silicification through which early life is observed. 相似文献
67.
瑞典中部西Ｂｅｒｇｓａｌｇｅｎ加斯博大理岩夹于变化火山岩中，其中分布有反应矽卡碉，钙－硅酸盐带及交代渗滤矽卡岩。它都是在Ｂｅｒｇｓｌａｇｅｎ较老花岗岩套的高位非造山ＯｓｔｒＨｏｊｄｅｎ花岗岩影响下形成的。反应矽卡岩和钙－硅酸盐带是在花岗岩定位前或定位时，由于大现岩与穿插其中的变火山岩、变石透镜体的变质作用形成的。它们由酸盐、磁铁矿、滑石、金云母、透闪石、透辉石、粒硅镁石、镁橄榄石、斜硅镁石、晶石及 相似文献
68.
69.
70.