全文获取类型
收费全文 | 8362篇 |
免费 | 1756篇 |
国内免费 | 1264篇 |
专业分类
测绘学 | 533篇 |
大气科学 | 954篇 |
地球物理 | 2650篇 |
地质学 | 4354篇 |
海洋学 | 1365篇 |
天文学 | 77篇 |
综合类 | 463篇 |
自然地理 | 986篇 |
出版年
2024年 | 23篇 |
2023年 | 66篇 |
2022年 | 228篇 |
2021年 | 318篇 |
2020年 | 319篇 |
2019年 | 346篇 |
2018年 | 299篇 |
2017年 | 370篇 |
2016年 | 399篇 |
2015年 | 433篇 |
2014年 | 531篇 |
2013年 | 516篇 |
2012年 | 513篇 |
2011年 | 596篇 |
2010年 | 470篇 |
2009年 | 600篇 |
2008年 | 625篇 |
2007年 | 588篇 |
2006年 | 520篇 |
2005年 | 478篇 |
2004年 | 386篇 |
2003年 | 323篇 |
2002年 | 309篇 |
2001年 | 262篇 |
2000年 | 294篇 |
1999年 | 244篇 |
1998年 | 244篇 |
1997年 | 195篇 |
1996年 | 161篇 |
1995年 | 141篇 |
1994年 | 132篇 |
1993年 | 113篇 |
1992年 | 96篇 |
1991年 | 49篇 |
1990年 | 42篇 |
1989年 | 35篇 |
1988年 | 35篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
综合论述了潟湖潮汐通道口门之流速、断面面积、通道长度、延时角和饱满系数之间的关系,以及沿岸漂沙对口门的影响。对不同类型的潟湖潮汐通道,提出了中潮位射流导流堤、口门复式断面和通道分汊等治理方法及其通道口门相关尺度的具体计算。 相似文献
65.
C.G. Castro M. Nieto-Cid X.A. lvarez-Salgado F.F. Prez 《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(12):1925-1940
The short-time-scale variability of the remineralization patterns in the domain of Eastern North Atlantic Central Waters (ENACW) off the NW Iberian Peninsula is studied based on biogeochemical data (oxygen, nutrient salts, total alkalinity, pH, dissolved organic matter and fluorescence of dissolved humic substances) collected weekly between May 2001 and April 2002. The temporal variability of inorganic variables points to an intensification of remineralization during the summer and autumn, with an increase of nutrients, total inorganic carbon and fluorescence and a decrease of oxygen. During the subsequent winter mixing, there is a biogeochemical reset of the system, with lower nutrients, total inorganic carbon and fluorescence and higher oxygen. In contrast to inorganic variables, the levels of dissolved organic matter in the ENACW seem to respond to short-term events probably associated with fast sinking particles, where solubilisation of organic matter prevails over remineralization. Applying a previously published stoichiometric model, we observed a vertical fractionation of organic-matter remineralization. Although there is a preferential remineralization of proteins and P compounds in the entire domain of ENACW, the percentage was higher in the upper ENACW (σ<27.10 kg/m3) than in the lower; the percentage of N and P compounds in the oxidised organic matter was >80% for the upper ENACW and 63% for the lower. Likewise, the redissolution of calcareous structures contributes about 6% and 13% to the carbon regenerated in the upper and lower layers of ENACW, respectively. 相似文献
66.
67.
Researchonthespectralanalysisandtestmethodofperiodsignalsinmonthlymeansealevel¥MaJirui;TianSuzhen;ZhengWenzhenandChaiXinmin(R... 相似文献
68.
69.
Xavier De Montaudouin 《Journal of Sea Research》1996,36(3-4)
In Arcachon Bay, a macrotidal coastal lagoon in southwest France, growth rates of cockles Cerastoderma edule (L.) differ greatly between locations. Sampling of populations at different tidal levels showed that the mean shell length was significantly and positively correlated with immersion time, whereas no correlation was found with population density and microphytobenthos biomass. Transplants of cockles between two intertidal sites were used to examine the relative importance of habitat and site of origin for growth rate and condition index. Artifacts due to manipulation were assessed, i.e. the impact of enclosures on growth, conditon index and mortality. During a 5-mo reciprocal transplant experiment, growth rates of the transplanted cockles and the cockles already present were similar, whereas the sites of origin did not affect growth rate. Condition index, however, displayed significant differences in relation to both transplant and origin sites. During a further 6-mo experiment in which cockles were transplanted from one site to four new sites, growth was mainly influenced by tidal level. These results indicate that net growth started when cockles were immersed 30% of the time. It is concluded that, on the scale of Arcachon Bay (156 km2), differences in growth and condition between cockle populations are largely phenotypic. Tidal level (i.e. food supply and emersion stress) accounts for most of these differences, but the existence of genetically or physiologically different populations cannot be excluded. 相似文献
70.
本文利用中日黑潮联合调查研究期间1986年5—6月和1989年7—8月航次水文与生物的同步取样资料,分析了东海测区内水系组成与浮游甲藻类及浮游桡足类等分布之间的对应关系。指出了不同生态类型的生物需要不同的物理海洋环境条件。同时,某些指示生物的分布又为区分水系、了解流系情况提供了良好的示性指标,并且从某些生物数量的变化还可以判断出水系混合与变性的程度。 相似文献