全文获取类型
收费全文 | 5249篇 |
免费 | 625篇 |
国内免费 | 1202篇 |
专业分类
测绘学 | 329篇 |
大气科学 | 635篇 |
地球物理 | 1817篇 |
地质学 | 2573篇 |
海洋学 | 793篇 |
天文学 | 176篇 |
综合类 | 232篇 |
自然地理 | 521篇 |
出版年
2024年 | 18篇 |
2023年 | 60篇 |
2022年 | 84篇 |
2021年 | 104篇 |
2020年 | 89篇 |
2019年 | 102篇 |
2018年 | 121篇 |
2017年 | 71篇 |
2016年 | 127篇 |
2015年 | 129篇 |
2014年 | 166篇 |
2013年 | 160篇 |
2012年 | 247篇 |
2011年 | 294篇 |
2010年 | 161篇 |
2009年 | 177篇 |
2008年 | 271篇 |
2007年 | 294篇 |
2006年 | 308篇 |
2005年 | 327篇 |
2004年 | 290篇 |
2003年 | 268篇 |
2002年 | 206篇 |
2001年 | 183篇 |
2000年 | 222篇 |
1999年 | 175篇 |
1998年 | 170篇 |
1997年 | 210篇 |
1996年 | 179篇 |
1995年 | 175篇 |
1994年 | 194篇 |
1993年 | 184篇 |
1992年 | 202篇 |
1991年 | 187篇 |
1990年 | 152篇 |
1989年 | 114篇 |
1988年 | 103篇 |
1987年 | 92篇 |
1986年 | 67篇 |
1985年 | 71篇 |
1984年 | 60篇 |
1983年 | 30篇 |
1982年 | 31篇 |
1981年 | 28篇 |
1980年 | 41篇 |
1979年 | 9篇 |
1964年 | 9篇 |
1959年 | 11篇 |
1958年 | 17篇 |
1957年 | 10篇 |
排序方式: 共有7076条查询结果,搜索用时 750 毫秒
41.
Seasonal and annual variations of marine sinking particulate flux during 1993~1996 in the central South China Sea 总被引:1,自引:0,他引:1
CHEN Ronghu WIESNER M G ZHENG Yulong CHENG Xinrong JIN Haiyan ZHAO Qingying ZHENG Lianfu 《海洋学报(英文版)》2007,26(3):33-43
A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species (Globigerinoides sacculifer, G. ruber, Globigerinita glutinata, Neogloboquadrina dutertrei) and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution. 相似文献
42.
Horiguchi T Li Z Uno S Shimizu M Shiraishi H Morita M Thompson JA Levings CD 《Marine environmental research》2004,57(1-2):75-88
Gastropods and bivalves were collected at 15 sites at Vancouver and Victoria, Canada between 24 May and 7 June, 1999, to establish tissue concentrations of butyltin and phenyltin compounds, to record imposex symptoms in gastropods, and to assess the present status of organotin contamination around Vancouver. No neogastropods (such as Nucella lima) were found around Vancouver. Neogastropod populations could have been extirpated by severe TBT contamination in Vancouver, as relatively high concentrations of TBT were detected in tissues of Mytilus trossulus from Vancouver, and the neogastropods distributed in Vancouver might be sensitive to TBT. Recovery from imposex, however, was observed in neogastropod populations from three sites at Victoria and Mission Point. TBT contamination has continued around Vancouver, arising from continuous use of TBT in antifouling paints for vessels larger than 25 m in length; however, TBT has decreased around Victoria and Mission Point. Different patterns of TBT accumulation in tissue were observed among the bivalve species from Vancouver. The highest TBT concentration detected in Tresus capax suggested some possible adverse effects. TBT was the most predominant butyltin component in almost all bivalve specimens surveyed, suggesting a low rate of TBT metabolism. Phenyltin compounds were not detected in any molluscan specimens in this study. 相似文献
43.
Regoli F Nigro M Chierici E Cerrano C Schiapparelli S Totti C Bavestrello G 《Marine environmental research》2004,58(2-5):637-640
The role of endosymbiotic diatoms as pro-oxidant stressors in porifera has been investigated in the Antarctic sponge Haliclona dancoi in which the presence of diatoms is influenced by marked seasonal variations during the austral summer. Both chlorophaeopigments and frustules were absent in sponge tissues sampled in early November at the beginning of the summer and increased from the mid of December with slightly shifted temporal trends. The efficiency of antioxidant defenses in the sponge showed a marked response to symbionts with clearly enhanced values corresponding to the peak of diatoms. 相似文献
44.
45.
O′Brien方法广泛应用于砂质海岸潮汐汊道的P-A关系研究。本文运用该方法求得东海沿岸11个潮汐汉道的P-A关系为:A=2.55×10~(-4)P~(0.92),lgA与lgP之间的线性相关系数为0.97。此结果的分析表明,东海沿岸潮汐汊道已接近于动态平衡;在细粒沉积物为主要物源的浙闽强潮基岩海岸,O′Brien方法也是适用的。 相似文献
46.
本文从单位时间和单位体积内通过光合作用转变为有机碳的重量出发,介绍了一个测定有机物初级生产力的新的海洋学方法。为了使对此感兴趣的人都能够参照他们各自的需要来应用或改进这一同位素定量方法,我们简短地对操作方法和历史作了一般的评价之后,还作了相当详尽的叙述。 相似文献
47.
北海盆地第三纪深海扇的定量分析T.Reynolds深海扇内富存有大量的碳氢化合物。因此,无论是从扇容积作为石油储层还是在生产期提供水的补给方面来说,它们的规模、几何形态、砂的体积、纯砂体积与总体积之比以及砂的连通性都是石油工业的关键问题。但是,至今深... 相似文献
48.
49.
Regoli F Gorbi S Frenzilli G Nigro M Corsi I Focardi S Winston GW 《Marine environmental research》2002,54(3-5):419-423
An integrate approach will be discussed for investigations on oxidative stress in xenobiotic toxicity. While the analysis of individual antioxidants is useful for their sensitivity and to understand the mode of action of a stressor, the integration with the analysis of the total antioxidant capacity provides a more holistic assessment of the overall biological significance of such variations. TOSC has a greater predictive value on the health condition of the organisms and allows to discriminate the different role of specific ROS in oxidative stress syndrome. 相似文献
50.