全文获取类型
收费全文 | 133篇 |
免费 | 0篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 1篇 |
地球物理 | 59篇 |
地质学 | 53篇 |
海洋学 | 15篇 |
天文学 | 2篇 |
综合类 | 2篇 |
自然地理 | 2篇 |
出版年
2019年 | 1篇 |
2018年 | 1篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 1篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 10篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 15 毫秒
1.
Boon JP van Zanden JJ Lewis WE Zegers BN Goksøyr A Arukwe A 《Marine environmental research》2002,54(3-5):719-724
The short-term effects of the commercial PBDE flame retardant mixtures Penta-BDE and cta-BDE on the expression of cytochrome P450 1A (CYP1A), vitellogenin (Vtg) and zona radiata proteins (Zrp) were investigated in juvenile salmon (Salmo salar). For this purpose, groups of fish were dosed twice (oral intake at days I and 4) with 10 and 50 mg/kg body weight of both commercial mixtures. The fishes were sacrificed at day 7 (n = 5 for each group) and 14 (n = 6 for each group), and blood, liver, fillet, and brain were collected. Blanks and positive controls were also part of the experiment. The expressions of Vtg, Zrp, and CYPIA were measured with several techniques (EROD, ELISA, Western, Northern and Slot Blot). The values in the groups of fish treated with Penta-BDE or Octa-BDE did not significantly differ from the reference group for any of the parameters tested. In contrast, the positive control groups treated with estradiol-17beta for Vtg and Zrp expression, and beta-naphthoflavone for CYP1A expression did show a significant response, indicating the potential sensitivity of the fishes for the parameters measured. Since the results of the chemical analyses showed concentrations of a number of PBDE congeners in liver, fillet, and brain that were about three orders of magnitude above those of fish from the North Sea, it is concluded that the short-term toxicity of both commercial PBDE mixtures for these endpoints was low. 相似文献
2.
Organochlorine concentrations were measured in white-sided dolphins, pilot whales, and their prey from the Gulf of Maine and used to identify species, tissue, and gender differences, and trophic transfer trends, in bioaccumulation. Polychlorinated biphenyl concentrations ([PCB]) in dolphin blubber (13 +/- 7.1 micrograms/g fresh wt.) were twice those in pilot whales, but pesticide concentrations (20 +/- 13 micrograms/g fresh) were similar between species. 4,4'-DDE, trans-non-achlor, Cl6(153) and Cl6(138) concentrations were highest. Skin tissues had more recalcitrant organochlorines than the internal organs. Male dolphins bioaccumulated higher concentrations of nonmetabolizable PCBs and hexachlorocyclohexane (HCH) isomers, whereas pilot whales had no gender-related differences in bioaccumulation. Pilot whales, mackerel, and herring had proportionately higher concentrations of DDTs, whereas [PCB] were higher in dolphins and squid. Although these odontocetes feed at the same trophic level and store a similar suite of contaminants, dolphins bioaccumulated higher and potentially hazardous 4,4'-DDE and PCB concentrations from food in their more geographically restricted range. 相似文献
3.
Hidore JJ 《The Journal of geography》1978,77(6):214-220
A serious problem associated with the population explosion in Africa is the widespread degradation of vegetation and soils. Various factors such as climate, animal overgrazing, overcultivation, fires, and soil erosion contribute to the social and economic impact in some areas. An increase of droughts due to lack of precipitation has damaged grasslands. In addition, increased animal population due to animal disease control, increased water supply, and social custom of measuring wealth in terms of herd size cause near wastelands from overgrazing. Also, overcultivation of commercial crops due to an increasing population has accelerated soil erosion by allowing shorter fallow periods, which causes lower crop yields and soil deterioration. Firing woodlands and grasslands to suppress new woody growth is damaging soil as well as encouraging the growth of coarse grasses that have little value for grazing animals. The barren land due to firing causes soil erosion both by water and wind; a total estimated drift of dust from western Africa is 60 million tons/year. These conditions indicate that deterioration will continue resulting in lower carrying capacities and lower productivity from cultivated land. 相似文献
4.
5.
6.
Franco JL Posser T Mattos JJ Sánchez-Chardi A Trevisan R Oliveira CS Carvalho PS Leal RB Marques MR Bainy AC Dafre AL 《Marine environmental research》2008,66(1):88-89
The aim of this study was to investigate biochemical changes in juvenile carp (Cyprinus carpio) exposed to zinc chloride (10, 30 and 100 microM) for a period of 48 h. Zinc exposure caused a concentration-dependent reduction in glutathione reductase (GR) activity in gills, liver and brain. Gill glutathione S-transferase (GST) was reduced when animals were exposed to the highest concentration of 100 microM zinc. The phosphorylation of p38(MAPK) increased in the brain of fish exposed to zinc 100 microM, while phosphorylation of the extracellular signal-regulated protein kinase 1/2 (ERK1/2) and c-Jun N-terminal protein kinase 1/2 (JNK1/2) remained unchanged. Expression of proteins HSP60 and HSP70 were not affected by zinc exposure. Considering the significant concentration-dependent inhibition of GR in all tissues analyzed, this enzyme could be a potential biomarker of exposure to zinc, which has to be confirmed. 相似文献
7.
8.
9.
10.
试验区面积约一千多平方公里,属大陆性半沙漠干旱气候的中低山丘陵地带,由于水源缺乏,草木难生,岩石裸露地表,是开展遥感地质工作的适宜区域。我们选用了1:2.5万的黑白航空照片和MSS多波段黑白、假彩色合成卫星照片进行了地质解译;并应用了IPOS101数字图象处理系统(简称S101系统)多种方法处理合成的彩色卫星照片进行了矿化预测,从而为普查找矿提供了依据,收到了较好的效果。 相似文献