全文获取类型
收费全文 | 684篇 |
免费 | 111篇 |
国内免费 | 132篇 |
专业分类
测绘学 | 26篇 |
大气科学 | 46篇 |
地球物理 | 176篇 |
地质学 | 397篇 |
海洋学 | 24篇 |
天文学 | 20篇 |
综合类 | 73篇 |
自然地理 | 165篇 |
出版年
2024年 | 1篇 |
2023年 | 11篇 |
2022年 | 26篇 |
2021年 | 43篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 47篇 |
2017年 | 36篇 |
2016年 | 44篇 |
2015年 | 46篇 |
2014年 | 43篇 |
2013年 | 41篇 |
2012年 | 42篇 |
2011年 | 44篇 |
2010年 | 30篇 |
2009年 | 24篇 |
2008年 | 32篇 |
2007年 | 31篇 |
2006年 | 28篇 |
2005年 | 17篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 17篇 |
2000年 | 24篇 |
1999年 | 38篇 |
1998年 | 31篇 |
1997年 | 34篇 |
1996年 | 18篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有927条查询结果,搜索用时 15 毫秒
921.
Nie Pin 《中国海洋湖沼学报》2000,18(1):54-60
This paper deals with the proportional distribution, niche breadth and niche overlap of two metazoan parasites (copepods species,Ergasilus anchoratus Markewitsch, 1946 andPseudergasilus parasiluri Yamaguti, 1936) and monogeneans (in the genusSilurodiscoides Gussev, 1976) found on gills of the fish,Silurus asotus L. from Jiangkou Reservoir in Jiangxi Province, China.E. anchoratus was the common and dominant metazoan parasite on gills of the fish in this locality as indicated by the higher infection
levels, and distributed almost evenly on gill arches without any observed gill-arch preference, as shown by the wide proportional
distribution and broad niche breadth.P. parasiluri and monogeneans inSilurodiscoides were found also without any significant gill-arch preference although they had a rather narrow niche breadth. The observed
significant overlap betweenP. parasiluri andSilurodiscoides spp. may be simply due to the lower infection levels of the parasites. The observed pattern of unrestricted distributions
of the parasitic copepods on gills of the fish may be accounted for, at least in part, by the moving ability of the copepods,
and may also indicate that the parasite does not exhibit any feature of gill-arch preference. However, further experimental
research is needed to verify the microhabitat distribution of the parasites.
Project 39370122 supported by NSFC. 相似文献
922.
Acidrainhasbeenaglobalenvironmentalprob-lem.SouthChinaandthesouthwestpartarethetwomainacidrainareasinChinawiththerangeof'pHvariationfrom4.5to4.O,andseientificstudiesonacidrainfocusontheseareas(WANGetal.,l997).Inre-centyears,however,inthenorthpartofChinaacidrainoccurred'notunusuallyandevenmoreseriouslysuchasincitiesofTumenandHunchuninJilinProvince.Itisessentialtodelveintothetemporalandspatialvariationsofatmosphericprecipitationacidityandthevariationscausesintheseareastoprovidesci-entificba… 相似文献
923.
综合功能区划的区域实践——以东北地区为例 总被引:1,自引:0,他引:1
我国“‘十一五’规划纲要”提出的按照主体功能区的划分对国土的开发和利用进行规划的 空间发展观对我国社会经济发展空间组织的影响将是深远的。本研究基于对东北地区空间发展 的总体情况的概观, 结合利用GIS 数据库分析所获的区域开发综合评价结果, 遵循一定的区划原 则, 获得了东北地区未来振兴的主体功能区划分的初步方案, 对于东北地区振兴规划的编制, 尤 其是空间总体布局的确立提供了重要的科学支撑, 同时本研究所遵循的“全局判断———分区评 价———方案确定”的基本框架对于其他区域主体功能区的划分具有借鉴意义。 相似文献
924.
水样的处理方法对水氡观测影响的探讨 总被引:1,自引:1,他引:0
同一口井的水氡观测,对水样采取不同的处理方法,观测值出现不同的结果.为研究其变化机理,对水样采取急剧降温的处理,与日常恒温处理的观测值进行对比分析,得出水样的不同处理方法对水氡观测有直接的影响及其影响的机理. 相似文献
925.
Understanding the driving forces of regional air pollution and its mechanism has gained much attention in academic research,which can provide scientific policy-making basis for economy-environment sustainability in China.Being an important energy and industrial base,the North China Plain region has been experiencing severe air pollution.Therefore,understanding the relationship between industrialization and air quality in this region is of great importance for air quality improvement.In this study,the average annual concentrations of SO2,NO2 and PM10 in 47 sample cities at and above the prefecture level in the North China Plain region from 2007 to 2016 were used to illustrate the spatiotemporal characteristics of air pollution within this region.Furthermore,panel data model,panel vector autoregression model,and impulse response function were used to explore the correlation and driving mechanism between energy-intensive industries and regional air quality.The results show that:first,overall air quality improved in the study area between 2007 and 2016,with a significant greater fall in concentration of SO2 than that of NO2 and PM10;second,provincial border areas suffered from severe air pollution and showed an apparent spatial agglomeration trend of pollution;and third,the test results from different models all proved that energy-intensive industries such as the chemical,non-metallic mineral production,electric and thermal power production and supply industries,had a significant positive correlation with concentrations of air pollutants,and indicated an obvious short-term impulse response effect.It concludes that upgradation of industrial structure,especially that of energy-intensive industries,plays a very important role in the improvement of regional air quality,which is recommended to be put in top priority for authorities.Therefore,policies as increasing investments in technological innovation in energy-intensive industries,deepening cooperation in environmental governance between different provinces and cities,and strengthening supervision and entry restrictions are suggested. 相似文献
926.
927.
Nie Gui-Bo Li Dong-fang Zhi Xu-dong Wang Fu-yang Zhang Chen-xiao 《Bulletin of Earthquake Engineering》2022,20(11):6327-6348
Bulletin of Earthquake Engineering - Single-layer reticulated domes with high capacity and attractive shapes are widely used in many modern facilities, ranging from industrial architecture to... 相似文献