全文获取类型
收费全文 | 860篇 |
免费 | 159篇 |
国内免费 | 253篇 |
专业分类
测绘学 | 73篇 |
大气科学 | 150篇 |
地球物理 | 341篇 |
地质学 | 490篇 |
海洋学 | 95篇 |
天文学 | 27篇 |
综合类 | 44篇 |
自然地理 | 52篇 |
出版年
2022年 | 13篇 |
2021年 | 11篇 |
2019年 | 14篇 |
2018年 | 12篇 |
2016年 | 14篇 |
2015年 | 14篇 |
2014年 | 18篇 |
2013年 | 13篇 |
2012年 | 23篇 |
2011年 | 42篇 |
2010年 | 21篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 36篇 |
2006年 | 48篇 |
2005年 | 34篇 |
2004年 | 38篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 35篇 |
2000年 | 71篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 30篇 |
1996年 | 14篇 |
1995年 | 21篇 |
1994年 | 26篇 |
1993年 | 44篇 |
1992年 | 14篇 |
1991年 | 29篇 |
1990年 | 15篇 |
1989年 | 24篇 |
1988年 | 9篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 16篇 |
1982年 | 20篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 50篇 |
1978年 | 32篇 |
1977年 | 35篇 |
1976年 | 47篇 |
1975年 | 29篇 |
1974年 | 24篇 |
1966年 | 7篇 |
1965年 | 9篇 |
1960年 | 14篇 |
1959年 | 25篇 |
1958年 | 11篇 |
排序方式: 共有1272条查询结果,搜索用时 15 毫秒
2.
MohammedHazaea HUKe MohammedMattash CHENBing M.O.AI-JabaliAref MohammedAbdussalam 《东北亚地学研究》2004,7(2):181-184
The chemical composition of several thermal springs around Changbaishan area has been investigated. Cenozoic basaltic rocks are widely distributed in Northeast China and geothermal characteristics have been described. About one hundred hot springs exist around Changhaishan Volcano at the border between China and D.P.R.Korea with high temperature about 82~C. The pH values of the spring water range from 6.9 to 7.1 and the total flow rate is about 4.8 L/sec. The chemical composition of the thermal springs is sodium carbonate; the high-mineral contents of thermal water are believed to have medicinal properties. Bathhouses are already built along the hot springs to take the advantage of the supposed healing properties. The high quality of those hot springs is believed to be utilitized for mineral water. The chemical equilibrium temperatures were estimated at about 160℃ based on the Na-K-Ca geochemical thermometer. 相似文献
3.
O.V.Chumak 《中国天文和天体物理学报》2003,3(2):175-182
We present a study of the relationship between integral area and corresponding total magnetic flux for solar active regions. It is shown that some of these relationships are satisfied to simple power laws. Fractal examination showed that some of these power laws can not be justified inside the simple models of stationary magnetic flux tube aggregation. All magnetic fluxes and corresponding areas were calculated using the data measured with the Solar Magnetic Field Telescope of the Huairou Solar Observing Station in Beijing. 相似文献
4.
5.
6.
中国科学院海洋研究所情报组 《海洋科学》1977,1(1):55-58
六十年代以来,海洋地质工作的发展达到了空前的程度,达些成就的取得主要是由于许多国家使用了多种新式仪器和新技术,通过大范围的海底调查取得的。所以有的人把这一历史阶段内的海底研究称为海洋地质工作上的革命时期。这一时期内的重大发现之一便是洋底的年龄比海水本身的年龄还要小,就是所谓的海底扩张说。这个学说引起了全世界地球科学工作者的密切注意。 相似文献
7.
Leaños-Castañeda O Gold-Bouchot G Van Der Kraak G Lister A Ceja-Moreno V Simá-Alvarez R 《Marine environmental research》2004,58(2-5):337-342
The objective of this study was to determine if tamoxifen or an aromatase inhibitor (4-hydroxyandrostenedione; 4-OHA) affected plasma concentrations of o,p' -DDT and its metabolites, o,p'-DDD and o,p'-DDE, in mature tilapia. Male and female tilapia were injected 6 times intraperitoneally with o,p'-DDT (40 mg/kg) alone or in combination with 4-OHA (2 mg/kg) over a 12 day period. An additional group of male fish was injected with tamoxifen (5 mg/kg) plus o,p'-DDT. At the end of the treatment period, plasma samples were extracted and analyzed by GC/ECD. Females injected only with o,p'-DDT had significantly higher levels of o,p'-DDT compared with males. Interestingly, females and males treated concomitantly with o,p'-DDT and 4-OHA or tamoxifen had significantly lower concentrations of plasma o,p'-DDT (about 50%) compared with fish treated with only o,p'-DDT. These initial results suggest that an interaction between endocrine-active compounds occurs in vivo in tilapia and may involve alterations in metabolism of o,p'-DDT. 相似文献
8.
9.
10.