全文获取类型
收费全文 | 38673篇 |
免费 | 7403篇 |
国内免费 | 10771篇 |
专业分类
测绘学 | 1874篇 |
大气科学 | 6377篇 |
地球物理 | 6644篇 |
地质学 | 20790篇 |
海洋学 | 8817篇 |
天文学 | 363篇 |
综合类 | 3251篇 |
自然地理 | 8731篇 |
出版年
2024年 | 88篇 |
2023年 | 468篇 |
2022年 | 1328篇 |
2021年 | 1531篇 |
2020年 | 1515篇 |
2019年 | 1745篇 |
2018年 | 1581篇 |
2017年 | 1714篇 |
2016年 | 1745篇 |
2015年 | 1899篇 |
2014年 | 2503篇 |
2013年 | 2348篇 |
2012年 | 2561篇 |
2011年 | 2710篇 |
2010年 | 2228篇 |
2009年 | 2767篇 |
2008年 | 2557篇 |
2007年 | 2870篇 |
2006年 | 2736篇 |
2005年 | 2477篇 |
2004年 | 2314篇 |
2003年 | 2118篇 |
2002年 | 1913篇 |
2001年 | 1559篇 |
2000年 | 1431篇 |
1999年 | 1355篇 |
1998年 | 1072篇 |
1997年 | 1015篇 |
1996年 | 887篇 |
1995年 | 728篇 |
1994年 | 675篇 |
1993年 | 554篇 |
1992年 | 470篇 |
1991年 | 365篇 |
1990年 | 236篇 |
1989年 | 247篇 |
1988年 | 151篇 |
1987年 | 106篇 |
1986年 | 55篇 |
1985年 | 51篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 20篇 |
1977年 | 15篇 |
1954年 | 10篇 |
1877年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
北部湾北部海上油田的开发工作始于50年代,60~70年代作了大量地质工作。改革开放后,油气勘查取得突破性进展。累计发现油气构造6个,含油面积超过40km2,石油地质储量约4亿t,已开发油田2个,揭开我国南方油气资源开发序幕 相似文献
52.
LAST GLACIATION AND MAXIMUM GLACIATION IN THE QINGHAI-XIZANG (TIBET) PLATEAU: A CONTROVERSY TO M. KUHLE,S ICE SHEET HYPOTHESIS 总被引:1,自引:0,他引:1
Since the late 1950's, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3-4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively drier, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during the 相似文献
53.
54.
T. H. BELL S. E. JOHNSON B. DAVIS A. FORDE N. HAYWARD C. WILKINS 《Journal of Metamorphic Geology》1992,10(3):295-307
Extensive examination of large numbers of spatially orientated thin sections of orientated samples from orogens of all ages around the world has demonstrated that porphyroblasts do not rotate relative to geographical coordinates during highly non-coaxial ductile deformation of the matrix subsequent to their growth. This has been demonstrated for all tectonic environments so far investigated. The work also has provided new insights and data on metamorphic, structural and tectonic processes including: (1) the intimate control of deformation partitioning on metamorphic reactions; (2) solutions to the lack of correlation between lineations that indicate the direction of movement within thrusts and shear zones, and relative plate motion; and (3) a possible technique for determining the direction of relative plate motion that caused orogenesis in ancient orogens. 相似文献
55.
APPLICATION OF ANALYTIC HIERARCHY PROCESS TO ASSESSING THE ECOLOGICAL VULNERABILITY OF WETLANDS IN THE JIANGHAN PLAIN 总被引:5,自引:1,他引:4
WANGXue-lei NINGLong-mei HUWang-bin 《中国地理科学(英文版)》2003,13(3):272-276
Wetlands in the Jianghan Plain are important components of wetland types in lake area in the middle and lower reaches the Changjiang (Yangtze) River and they fulfill many uses and functions related to hydrology,waste assimilation, ecosystem productivity and biodiversity. Owing to natural factors and human activities, especially excessive reclamation from lakes, the shrinking process of the lakes has been accelerated. Wetland ecosystem has shown the characteristics of vulnerability. According to the analysis of wetland ecological function in the Jianghan Plain, this paper presented an index system related to productivity, stability and environmental capacity. By using the method of Analytic Hierarchy Process, we computed the values of the relative weights of the indexes, and evaluated the vulnerability level of the wetland ecosystem by the method of multi-indexes. The case study showed that the fragile extent of wetland ecosystem in the Jianghan Plain is 5.6. This means that the wetland ecosystem in the Jiang-han Plain is laid to the state of middle vulnerability. Therefore, the wetland conservation and eco-rehabilitation in the JiangJaan Plain should be paid attention to. 相似文献
56.
JINFeng-jun 《中国地理科学(英文版)》2003,13(2):97-103
It is very important to establish cooperative mechanism to guarantee all members to develop their e-conomies in the Yellow Sea Rim. In this paper, the development strategies ofshipplng centers and transportation networkare discussed based on economic giobalization tendency. The results argue that a united transportation network should bebuilt in order to promote the economic competition of Northeast Asia in the world. As a key component of the economiccooperation, a hierarchical shipping centers network should be established with Hong Kong, Shanghai, Pusan, Koho,and Tokyo as cores. The authorities of China, Japan, R. O. Korea and D. P. B. Korea should make more efforts tobuild a set of cooperation institutions based on raising the transportation efficiency. 相似文献
57.
MEN Wu ) WEI Hao ) and LIU Guangshan ) * ) College of Oceanography Environmental Science Xiamen University State Key Laboratory of Marine Environmental Science 《中国海洋大学学报(英文版)》2006,5(3):228-234
1Introduction Therearefourradiumisotopesinnature,ofwhich224Ra,226Raand228Rahavebeenwidelyinvestigated inmarineresearch,butthespecificactivityof223Rais toolowtobemeasured,therefore,itsapplicationsarelimited(Moore,1969;Broeckeretal.,1976;KuandLin,1976;Nozak… 相似文献
58.
Pco2 of air and seawater samples from the East China Sea(ECS) were measured in situ in autumn, 1994,Ocean currents,terrestrial fluviation,biological activities,etc.,Pco2 char-acters in air and seawater were investigated,CO2 flux and its character in the East China Sea are discussed on the basis of the Pco2 profiles of air and seawater,It was clear that the nearshore was the source of CO2;and tht the oulter sea area was the sink of CO2; and that the shelf area of the EXS is a net sink for atmospheric CO2 in autumn. 相似文献
59.
SORPTION AND DESORPTION CHARACTERISTICS OF CADMIUM BY FOUR DIFFERENT SOILS IN NORTHEAST CHINA 总被引:3,自引:0,他引:3
ZHANG Lei SONG Feng-bin 《中国地理科学(英文版)》2005,15(4):343-347
1IN TR O D U C TIO NA s a persistentand toxic pollutant, cadm ium (C d) canresultin m any adverse health effects in a variety oftis-suesand organssuch asthe lung,kidney,urinary,blad-der,pancreas,breast and prostate (SA TA R U G etal.,2003).C adm ium in so… 相似文献
60.
从地形地貌特征、重磁地球物理场、深部构造与断裂构造以及地震活动、震源机制等多方面论述北东东向构造是南海北缘的主要活动构造。对于长期以来认为新华夏系北东向构造是该区主要活动构造的观点来说,这是一种新的学术思想。 相似文献