全文获取类型
收费全文 | 53848篇 |
免费 | 12584篇 |
国内免费 | 19643篇 |
专业分类
测绘学 | 9952篇 |
大气科学 | 7050篇 |
地球物理 | 10053篇 |
地质学 | 36312篇 |
海洋学 | 10130篇 |
天文学 | 659篇 |
综合类 | 4175篇 |
自然地理 | 7744篇 |
出版年
2024年 | 673篇 |
2023年 | 1729篇 |
2022年 | 3493篇 |
2021年 | 4241篇 |
2020年 | 3399篇 |
2019年 | 4015篇 |
2018年 | 3358篇 |
2017年 | 3191篇 |
2016年 | 3404篇 |
2015年 | 3879篇 |
2014年 | 3704篇 |
2013年 | 4409篇 |
2012年 | 5088篇 |
2011年 | 4948篇 |
2010年 | 4933篇 |
2009年 | 4637篇 |
2008年 | 4419篇 |
2007年 | 4135篇 |
2006年 | 4046篇 |
2005年 | 3284篇 |
2004年 | 2404篇 |
2003年 | 1731篇 |
2002年 | 1814篇 |
2001年 | 1681篇 |
2000年 | 1333篇 |
1999年 | 596篇 |
1998年 | 217篇 |
1997年 | 152篇 |
1996年 | 124篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 79篇 |
1992年 | 96篇 |
1991年 | 35篇 |
1990年 | 58篇 |
1989年 | 39篇 |
1988年 | 42篇 |
1987年 | 48篇 |
1986年 | 68篇 |
1985年 | 40篇 |
1984年 | 54篇 |
1983年 | 40篇 |
1982年 | 39篇 |
1981年 | 16篇 |
1979年 | 47篇 |
1978年 | 23篇 |
1976年 | 13篇 |
1973年 | 12篇 |
1957年 | 19篇 |
1954年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
Application of LICOM to the numerical study of the water exchangebetween the South China Sea and its adjacent oceans 总被引:8,自引:1,他引:8
1 IntroductionThe South China Sea (SCS) is the largestmarginal sea in the western Pacific (see Fig. 1). It con-nects with the SCS through the Taiwan Strait, with thePacific through the Luzon Strait, with the Sulu Seathrough the Mindoro and Balabac Straits and with theJava Sea and Andaman Sea through the Sunda Shelf(For convenience, here we refer to the section at 1.5°N,Fig. 2). It is shown that the seasonal SCS circulation ismostly affected by the summer/winter monsoon, andthe no… 相似文献
142.
143.
Using 203HgCl2 as a tracer, uptake and combination of inorganic mercury in Tilapia mossambica (petres) and its transfer between different tissues of the fish were studied. The results demonstrate that gill is the main tissue uptaking mercury directly from seawater and that the mercury in gill, skin, digestive tube and fin would be transferred to the other tissues. The result of gel chromatography with Sephadex G-75 shows that most of mercury in gill filaments, liver, and digestive tube are bound in high molecules (MW-70000) and not in metallothionein, but in kidney and bile mercury binding proteins are similar to metallothionein and are accounted for up to 60% and 46% respectively. 相似文献
144.
AN ECOSYSTEM MODEL ANALYSIS OF THE EFFECT OF MINE TAILINGS ON THE EUPHOTIC ZONE OF A PELAGIC ECOSYSTEM 总被引:1,自引:0,他引:1
A computer analysis was performed on experimental results obtained when mine tailings were added to seawater. The Mixed Upper-Layer Ecotrophie Simulation (MULES) model was tested by changing the extinction coefficient and the abundance of heterotrophic zooflagellates. Increasing the extinction coefficient resulted in a delay of phytoplankton growth, an increase in zooplankton standing stock and better growth of autotrophic flagellates compared with diatoms. Zooflagellates in the ecosystem influence the growth of zooplankton; secondary production by zooplankton was markedly depressed at low levels of zooflagellates. These results are believed to be of general significance for the diagnosis of suspended sediment effects on planktonic ecosystems. 相似文献
145.
146.
对单芯电缆传输这种通讯技术的原理进行了阐述;分析提出了部分电路、部件的技术指标;作为一种数据传输的手段,对单芯电缆传输技术在海洋专用CTD中的应用进行了相关论述. 相似文献
147.
Sea ice characteristics between the middle Weddell Sea and the Prydz Bay, Antarctica during the austral summer of 2003 总被引:1,自引:0,他引:1
The antarctic sea ice was investigated upon five occasions between January 4 and February 15, 2003. The investigations included: (1) estimation of sea ice distribution by ship-based observations between the middle Weddell Sea and the Prydz Bay; (2) estimation of sea ice distribution by aerial photography in the Prydz Bay; (3) direct measurements of fast ice thickness and snow cover, as well as ice core sampling in Nella Fjord; (4) estimation of melting sea ice distribution near the Zhongshan Station; and (5) observation of sea ice early freeze near the Zhongshan Station. On average, sea ice covered 14.4% of the study area. The highest sea ice concentration (80%) was observed in the Weddell Sea. First-year ice was dominant (99.7%-99.8%). Sea ice distributions in the Prydz Bay were more variable due to complex inshore topography, proximity of the Larsemann Hills, and/or grounded icebergs. The average thickness of landfast ice in NeUa Fjord was 169.5 cm. Wind-blown snow redistribution plays an important role in affecting the ice thickness in Nella Fjord. Preliminary freezing of sea ice near the Zhongshan Station follows the first two phases of the pancake cycle. 相似文献
148.
海洋环流模式中不同近似假设下的海表高度 总被引:1,自引:1,他引:1
Boussinesq近似是现代海洋环流模式中经常采用的假设,但随着海洋模式的不断发展完善以及气候研究应用的需要,有必要估算Boussinesq近似造成的模式误差。分别利用一个非Boussinesq近似的海洋模式与另一个结构相同且采用Boussinesq近似的模式计算海表高度,并同时利用模式预报的温度、盐度资料计算了比容异常高度。分析结果显示,这3种不同定义的海表高度无论空间结构,还是时间演变,都基本类似,尤其在热带海区最接近,差值≤1cm。Boussinesq近似意味着在模式中以体积守恒代替质量守恒,通常的做法是对其进行简单的质量补偿来保持质量守恒。比较说明,以质量补偿方法进行的高度订正对减小Boussinesq近似带来的误差没有本质的意义。 相似文献
149.
150.
海沧邻近海域表层沉积物中重矿物研究 总被引:3,自引:0,他引:3
对厦门海沧邻近海域表层沉积物中的重矿物(0.063~0.125mm粒级)进行了分析和研究,结果表明该粒级的重矿物共计49种,其优势和特征矿物为磁铁矿、赤铁矿、褐铁矿、绿帘石、铁铁矿、角闪石、锆石、红柱石等;重矿物的平均质量分数为9.56%;根据重矿物的分布和含量,并结合主要标志矿物的颗粒百分含量和分布特征,将该海域划分为5个矿物组合区,根据各区的矿物组合类型分析了该海域的物质来源及影响重矿物分布和组合的因素,进而探讨了九龙江河口湾和厦门西港海湾的沉积环境。 相似文献