全文获取类型
收费全文 | 1667篇 |
免费 | 227篇 |
国内免费 | 341篇 |
专业分类
测绘学 | 188篇 |
大气科学 | 122篇 |
地球物理 | 594篇 |
地质学 | 640篇 |
海洋学 | 339篇 |
天文学 | 66篇 |
综合类 | 114篇 |
自然地理 | 172篇 |
出版年
2024年 | 6篇 |
2023年 | 42篇 |
2022年 | 49篇 |
2021年 | 48篇 |
2020年 | 26篇 |
2019年 | 44篇 |
2018年 | 41篇 |
2017年 | 27篇 |
2016年 | 41篇 |
2015年 | 44篇 |
2014年 | 57篇 |
2013年 | 56篇 |
2012年 | 103篇 |
2011年 | 120篇 |
2010年 | 82篇 |
2009年 | 59篇 |
2008年 | 112篇 |
2007年 | 98篇 |
2006年 | 100篇 |
2005年 | 75篇 |
2004年 | 89篇 |
2003年 | 71篇 |
2002年 | 65篇 |
2001年 | 59篇 |
2000年 | 74篇 |
1999年 | 41篇 |
1998年 | 44篇 |
1997年 | 34篇 |
1996年 | 46篇 |
1995年 | 43篇 |
1994年 | 34篇 |
1993年 | 46篇 |
1992年 | 47篇 |
1991年 | 34篇 |
1990年 | 42篇 |
1989年 | 44篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 17篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1976年 | 3篇 |
1964年 | 3篇 |
1947年 | 3篇 |
1934年 | 4篇 |
1924年 | 3篇 |
排序方式: 共有2235条查询结果,搜索用时 31 毫秒
81.
E. Puga Antonio M. alvarez- Valero J. Galindo- Zaldlvar F. Bohoyo A. Maldonado A.Maldonado L. Somoza F. J. Gonzaezz L. Somoza 蔡观强 《海洋地质》2009,(1)
本研究对来自DOVE盆地(Scotia海南部)中部火山山脊的拖网样品进行了详细的岩石学、地球化学分析,辅以K—Ar年代学分析。研究区水深2000~3000m,地理坐标范围为59°21~23′S和42°27~31′w。本研究的目的在于,通过比较研究区火成岩和形成Scotia、Antartic—Phoenix洋中脊及南设得兰群岛的火山岩之间的地球化学特征和同位素特征,厘定研究区岩浆形成的地球动力学背景以及岩浆作用的绝对年龄。 相似文献
82.
Ugolini A Ungherese G Somigli S Galanti G Baroni D Borghini F Cipriani N Nebbiai M Passaponti M Focardi S 《Marine environmental research》2008,65(4):349-357
The present paper assesses the use of the supralittoral amphipod Talitrus saltator as a bioindicator of the effects of human trampling on the supralittoral sandy band. Samplings in delimited areas were carried out at sites subjected to different human impact. The results showed a strong negative correlation between the number of swimmers and the sandhopper population density, while there was no clear relationship between sandhopper abundance and the other factors considered: granulometry, compactness and organic carbon content of the sand, and trace metal contents in the sand and sandhoppers. A field test of trampling conducted in a confined space showed its direct negative effect on sandhopper survival. However, trace metal analysis confirmed the ability of T. saltator to bioaccumulate some elements (Hg, Zn, Cu, Cd). Our study demonstrates that T. saltator is a good bioindicator of human impact in the supralittoral zone of sandy shores. 相似文献
83.
Almroth BC Sturve J Stephensen E Holth TF Förlin L 《Marine environmental research》2008,66(2):271-277
The use of fish in environmental monitoring has become increasingly important in recent years as anthropogenic substances, many of which function as prooxidants, are accumulating in aquatic environments. We have measured a battery of antioxidant defenses as a measure of oxidative status, as well as protein carbonylation as a measure of oxidative damage, in corkwing wrasse (Symphodus melops) captured near a disused copper mine, where water and sediment are contaminated with heavy metals, and an aluminum smelter, a site contaminated with PAHs. Results were compared to two different reference sites. Fish at the heavy metal site had lower glucose-6-phosphate dehydrogenase activity and elevated protein carbonyls (1.8 times) compared to fish from the reference site. At the PAH site, EROD was increased 2-fold, while total glutathione and methemoglobin reductase concentration, were decreased. No differences were seen in protein carbonyl levels at the PAH site. Measures of both antioxidant defenses and oxidative damage should be used when assessing effects of xenobiotics on oxidative stress in fish species. 相似文献
84.
Diagnosis of trace metal contamination in sediments: the example of Ensenada and El Sauzal, two harbors in Baja California, Mexico 总被引:1,自引:0,他引:1
Huerta-Diaz MA Delgadillo-Hinojosa F Hernández-Ayón M Segovia-Zavala JA García-Esquivel Z López-Zárate H Siqueiros-Valencia A Galindo-Bect S 《Marine environmental research》2008,66(3):345-358
Total metal concentrations in sediments from within Ensenada and El Sauzal Harbors are generally higher than at the mouths. Grain-size analyses suggested that this enrichment could be due to the presence of fine-grained sediments in the inner part of the harbors rather than to anthropogenic perturbations. The (Me/Al)(sample) ratios for Pb, Co, Ni and Fe were significantly higher for Ensenada Harbor relative to El Sauzal Harbor, whereas the ratios for Cd, Mn, Zn and Cu were statistically equivalent for both harbors. Calculated enrichment factors [EF(Me)=(Me/Al)(sample)/(Me/Al)(shale)] indicated that the metals showing slight enrichment were those associated with anthropogenic contamination (Pb, Zn), or probably related to primary productivity in the water column (Cd, Co). The levels of most of the metals were not greatly enriched, a consideration that is of the utmost importance when contamination issues are at stake. 相似文献
85.
Comet assay in phytoplankton as biomarker of genotoxic effects of environmental pollution 总被引:2,自引:0,他引:2
The alkaline comet assay was tested on different microalgae: the dinoflagellates, Karenia mikimotoi and Alexandrium minutum, and the diatom, Chaetoceros gracilis. The microalgae were exposed during their exponential growth to the model direct genotoxicant, hydrogen peroxide (1h, 5 and 100muM H2O2). Following H2O2 exposure, the comet assay was validated only for K. mikimotoi for which genotoxicity was observed from the lowest tested concentration of 5 microM with a concentration-dependent effect. C. gracilis was too small in size (4 microm) to be correctly analysed. For A. minutum, our lysis buffer was not strong enough to digest the cellulosic thecal plates. For K. mikimotoi, the comet assay was thus applied for the study of the genotoxic effects of different pesticides: epoxiconazole (as Opus formulation), chlorpyriphos-ethyl (as Dursban formulation) and endosulfan at 1, 10 and 100 microg of active substance/L for 24h. Exposure to epoxiconazole in formulation resulted in an increase in the extent of DNA strand breaks at the highest tested concentration icro/L. Endosulfan exposure resulted in DNA damage for K. mikimotoi nuclei. Genotoxicity was observed from 1 microg/L of endosulfan and was not concentration dependent. 相似文献
86.
对于测绘技术人员来说,需要编写设计书、技术总结、监测方案等测绘类文档。利用Word2003自带的绘图工具,远远不能满足要求。介绍了“利用复制+粘贴工具”、“转换图像格式”、“使用插入对象”三种方式在Word2003文档中插入AutoCAD2004图形的三种方法, 相似文献
87.
对虾传染性肌肉坏死病(infectious myonecrosis,IMN)最初于2002年8月爆发于巴西Piaui州的凡纳滨对虾(Litopenaeus vannamei)养殖场,并很快在巴西东北沿岸蔓延开来,目前已传至亚洲.2004年,经美国亚利桑那大学(University of Arizona)水产病害实验室研究,该病为一种新的对虾疾病,根据其症状,暂定名为传染性肌肉坏死病. 相似文献
88.
89.
90.