全文获取类型
收费全文 | 18892篇 |
免费 | 1926篇 |
国内免费 | 2737篇 |
专业分类
测绘学 | 2101篇 |
大气科学 | 1905篇 |
地球物理 | 2455篇 |
地质学 | 6058篇 |
海洋学 | 2074篇 |
天文学 | 188篇 |
综合类 | 2405篇 |
自然地理 | 6369篇 |
出版年
2024年 | 85篇 |
2023年 | 282篇 |
2022年 | 431篇 |
2021年 | 442篇 |
2020年 | 384篇 |
2019年 | 544篇 |
2018年 | 301篇 |
2017年 | 250篇 |
2016年 | 315篇 |
2015年 | 410篇 |
2014年 | 1662篇 |
2013年 | 1064篇 |
2012年 | 1319篇 |
2011年 | 1352篇 |
2010年 | 1203篇 |
2009年 | 1394篇 |
2008年 | 1150篇 |
2007年 | 1009篇 |
2006年 | 873篇 |
2005年 | 1191篇 |
2004年 | 957篇 |
2003年 | 1080篇 |
2002年 | 885篇 |
2001年 | 764篇 |
2000年 | 591篇 |
1999年 | 562篇 |
1998年 | 447篇 |
1997年 | 388篇 |
1996年 | 342篇 |
1995年 | 284篇 |
1994年 | 307篇 |
1993年 | 203篇 |
1992年 | 231篇 |
1991年 | 225篇 |
1990年 | 182篇 |
1989年 | 189篇 |
1988年 | 44篇 |
1987年 | 28篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1975年 | 5篇 |
1959年 | 8篇 |
1943年 | 5篇 |
1941年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Distribution characteristics of heavy metals in surface sediments and core sediments of the Shenzhen Bay in Guangdong Province, China 总被引:1,自引:1,他引:0
The concentration of zinc, chromium, cadmium, nickel, lead and copper was measured on both surface sediments and core sediments in the Shenzhen Bay. The average contents of all metals have exceeded the background values in the coastal zone of Guangdong Province. Cadmium is a heavy pollution matter which indicates a strong pollution level according to the ecological risk coefficient method. The ecological risk index of the whole area is 299 which belongs to middle and strong level. The area with strong pollution level is the near shore area closing to the inside of Shenzhen Bay, Shakou area is in the middle level while the weak pollution level occurs in Shenzhenhe Estuary according to ecological risk index. The four sediment cores can be divided into two parts based on lead-210 dating, sediments size analysis and economic development period in surrounding areas since 1950 with strong human intervention. The sediment size, deposition rate and human activities have positive relationship with the contents of heavy metals which directly impact the pollution level of heavy metals in sediments in Shenzhen Bay. 相似文献
912.
Multivariate analysis of fluorescence and source identification of dissolved organic matter in Jiaozhou Bay, China 总被引:1,自引:0,他引:1
Hierarchical clustering analysis and principal component analysis (PCA) methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy (EEMs) data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter (DOM). The distribution of different water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay. 相似文献
913.
Nine species of Prionospio complex are recorded from China’s waters, including one new species and six newly recorded species. Prionospio (Prionospio) pacifica sp. nov., is characterized by having first and forth pairs of branchiae pinnate, second and third pairs of apinnate, ventral crest on Setiger 9 and dorsal crests on Setigers 10—25. Apoprionospio kirrae (Wilson, 1990), Prionospio (Aquilaspio) convexa Imajima, 1990, Prionospio (Minuspio) multibranchiata Berkeley, 1927, Prionospio (Prionospio) bocki Sderstrm, 1920, Prionospio (Prionospio) dubia Maciolek, 1985 and Prionospio (Prionospio) paradisea Imajima, 1990 are recorded for the first time from China’s waters. 相似文献
914.
Based on a synthesis of zircon inheritance from Mesozoic igneous rocks in the eastern portion of the North China Craton (NCC) , it is proposed that inherited zircons with Neoproterozoie ages identified from these rocks are of a heterogenous derivation from the Yangtze/South China block, rather than from the NCC itself. The mechanism that introduces these zircons incorporated into the NCC is likely by tectonic underplating during the Triassic continental subduction of the Yangtze block beneath the NCC. Tectonic addition of abundant crustal materials represented by the heterogenous zircons into the NCC, probably along Moho or weak interfaces within the NCC's crust, led to the crustal thickening in the NCC. These heterogenous materials, either as (partial) source rocks or as contaminants of the magmas generated during an extension environment following the crustal thickening, were reworked and therefore have significant contribution to petrogenesis of the Mesozoic igneous rocks. The crustal thickening resulted from the tectonic underplating, as indicated by the distribution extent of the heterogenous zircons, is spatially similar to that of the lithospheric thinning, with both mainly occurring in the eastern segment of the NCC. This is probably suggestive of an intrinsic relation between the thickening and thinning events during the Mesozoic evolution of the NCC. 相似文献
915.
《地球信息科学学报》2009,(3):F0003-F0003
中国地理学会期刊出版年会于2009年4月29日至5月3日在湖南省衡阳师范学院隆重召开。本次年会由中国地理学会编辑出版工作委员会与衡阳师范学院共同主办、衡阳师范学院资源环境与旅游管理系承办。来自全国各地30余家地理学期刊和出版社的代表,以及高等院校的师生约300余人参加了此次年会。 相似文献
916.
一个由国际矿业企业工作委员会与中外商通咨询服务有限公司联合组织的“中国矿业投资考察团”正紧锣密鼓组建中,将参加2009年2月初的第14届非洲国际矿业大会。是什么吸引了如此多的中国企业—— 相似文献
917.
矿产资源虽然在人类社会发展及进化过程中具有重要的基础支撑作用,但是由于各国资源禀赋、工业化进程及产业结构等方面存在差异,进而导致各类矿产的生产与消费在不同的历史时期存在很大的差别.我国大宗矿产非常紧缺,抓住全球矿产品供需形势变化所带来的战略机遇,对优化我国矿产资源配置及提高资源安全保障能力等方面具有重要的现实意义. 相似文献
918.
920.