全文获取类型
收费全文 | 2814篇 |
免费 | 153篇 |
国内免费 | 734篇 |
专业分类
测绘学 | 120篇 |
大气科学 | 270篇 |
地球物理 | 1147篇 |
地质学 | 1157篇 |
海洋学 | 317篇 |
天文学 | 148篇 |
综合类 | 326篇 |
自然地理 | 216篇 |
出版年
2023年 | 24篇 |
2022年 | 24篇 |
2021年 | 21篇 |
2020年 | 27篇 |
2019年 | 25篇 |
2018年 | 36篇 |
2016年 | 37篇 |
2015年 | 25篇 |
2014年 | 59篇 |
2013年 | 36篇 |
2012年 | 111篇 |
2011年 | 146篇 |
2010年 | 53篇 |
2009年 | 88篇 |
2008年 | 127篇 |
2007年 | 170篇 |
2006年 | 158篇 |
2005年 | 161篇 |
2004年 | 163篇 |
2003年 | 150篇 |
2002年 | 145篇 |
2001年 | 153篇 |
2000年 | 208篇 |
1999年 | 67篇 |
1998年 | 63篇 |
1997年 | 102篇 |
1996年 | 53篇 |
1995年 | 84篇 |
1994年 | 74篇 |
1993年 | 115篇 |
1992年 | 83篇 |
1991年 | 116篇 |
1990年 | 81篇 |
1989年 | 89篇 |
1988年 | 71篇 |
1987年 | 66篇 |
1986年 | 50篇 |
1985年 | 72篇 |
1984年 | 73篇 |
1983年 | 33篇 |
1982年 | 36篇 |
1981年 | 28篇 |
1980年 | 41篇 |
1979年 | 8篇 |
1959年 | 8篇 |
1958年 | 9篇 |
1947年 | 7篇 |
1939年 | 7篇 |
1926年 | 7篇 |
1924年 | 8篇 |
排序方式: 共有3701条查询结果,搜索用时 15 毫秒
91.
92.
西班牙的Cabo de Gata Nijar天然公园提供了某些使其具有重要地质生态和环境意义的独特特征。作为该公园环境和采矿活动(直到十几年前才停下来)产生影响研究的优先步骤,确定了矿山和废物遗弃场地的位置,对岩性作了鉴定。为了达到这个目的,采用了不同的遥感技术来建立高分辨率的图像文件,图像文件将成为该区地质和环境填图的根据:因为从前的采矿活动牵涉到当地的环境,所以特别注意这些区域。由于具有不同空间/频谱分辨率的遥感图像日益加大的可用性,因此它们已成为很有用的工具。上述的是SPOT全色和陆地卫星专题成像仪多频图像的情形,它们是地质和环境研究中最常使用的基于遥感的两种图像。在为数众多阐述组合遥感图像资料的技术中,本文利用SPOT全色和陆地卫星TM资料研究那些基于亮度一色相一彰度(饱和度)、主要成分分析、高通滤波器和颜色正规化的变换。该研究的目标是:分析和对比一些最常使用的方法;选择最适合用于详细地质.环境研究的方法;将该方法用于Cabo de Gata Nijar地区一国家最具特色的一个天然公园场地。 相似文献
93.
Tanlu Fault Zone (TFZ) is a large NE trending deep fracture system in East China and is about 2500 km long. It extends from the south of Lujiang to Tancheng, and passes through the Bohai Sea and continues to the north, where it branches into Yilan ?Shulan Fault and Dunhua ?Mishan Fault. TFZ is a long lasting huge deep - rooted lithospherical fault system with different characteristics in different parts and at different periods of its evolution. TFZ also controls the distribution and occur-rences of many superlarge, large, middle and small sized gold ore deposits, e. g. Jiapigou, Haigou, Xiaoxihancha and Ciwei-gou gold deposits in Northeast China; Linglong, Jiaojia, Sanshandao, Taishang, Xincheng, Rushan, and Pengjiakuang gold deposits in Jiaodong Peninsula of Shandong Province; and Guilaizhuang and Yinan in Western Shandong Province. 相似文献
94.
Pedro S.B.REYES Mauricio E.VALAREZO Jenry CóRDOVA Fran?ois A.MICHAUD Camilo ZAPATA 《山地科学学报》2018,15(5):966-975
The longitudinal profile of a river channel can be described in function of mathematical expressions. The logarithmic fit is the most used method to describe the relative equilibrium of a channel elevation profile. Rivers showing zones of high channel gradient and convex-upward profiles can be evaluated in function of the offset distance with respect to the logarithmic curve. The Jama River profile has been constructed using differential GPS data for the downstream reach and 4-m-grid DEM data base for the remaining headward profile. The resulting longitudinal profile shows a prominent knickpoint of about 80 m in elevation characterized by sharp local convexity. The offset distance in vertical direction from the logarithmic plot is interpreted as the successive accumulation of multiple uplift episodes associated with the Jama Fault System activity. The horizontal offset is suggested to represent the remaining retreated distance for the upstream propagation of the Jama knickpoint. The highly resistant Cretaceous rocks outcropping along the Jama knickpoint reach acts as an inflection point between two subprofiles that show well-fitted logarithmic curves, thereby representing a temporary partitioned equilibrium along the Jama River profile. 相似文献
95.
KONG Desen LUAN Maotian and WANG Weiming School of Civil Engineering Harbin Institute of Technology Harbin P.R.China School of Civil Architectural Engineering Shandong University of Science Technology Qingdao P.R.China Institute of Geotechnical Engineering Dalian University of Technology Dalian P.R.China 《中国海洋大学学报(英文版)》2006,(1)
The study on the earthquake-resistant performance of a pile-soil-structure interaction system is a relatively complicated and primarily important issue in civil engineering practice. In this paper, a computational model and computation procedures for pile-supported structures, which can duly consider the pile-soil interaction effect, are established by the finite element method. Numerical implementation is made in the time domain. A simplified approximation for the seismic response analysis of pile-soil-structure systems is briefly presented. Then a comparative study is performed for an engineering example with numerical results computed respectively by the finite element method and the simplified method. Through comparative analysis, it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method. The numerical results and findings will offer instructive guidelines for earthquake-resistant analysis and design of pile-supported structures. 相似文献
96.
SUN Jilin ) )* XU Delong ) and GU Dejun ) ) Physical Oceanography Laboratory Ocean-Atmosphere Interaction Climate Laboratory Ocean University of China Qingdao P.R.China) Institute of Tropical Meteorology Guangzhou P.R.China 《中国海洋大学学报(英文版)》2006,5(3):200-206
1Introduction Theglobalclimatechangehasbeenoneoftheprob lemschallengingtheworldinrecentyears.TheweatherandclimateonEarthhasbeeninvariationontimescalesfromseasonaltomillennialorevenlonger.ResearchesonvariationsofweatherandclimateintheNorthernHemispherehave… 相似文献
97.
Synthesis, Characterization and Antibacterial Activity of New Ln(Ⅲ ) Complexes with an Unsymmetrical Schiff Base Ligand 总被引:1,自引:0,他引:1
BI Caifeng* YAN Liangliang FAN Yuhua ZHANG Xia and WANG Aidong College of Chemistry Chemical Engineering Ocean University of China Qingdao P.R.China 《中国海洋大学学报(英文版)》2006,5(3):235-238
1Introduction SomeSchiffbasecomplexesderivedfromaminoacidsareparticularlyactiveinbiologycatalysisandmaterial.Thestudyofthemisfocusofthestudyof coordinationchemistry.Recently,studiesofsuchmetalcomplexesofmono Schiffbaseshavebeenre ported(Fanetal.,2003a,b;L… 相似文献
98.
Juana P Moiwo 《东北亚地学研究》2006,9(1):80-93
IntroductionNever before hasit beensotrue than now,thatlandis ali mitedresource.Population growth and as-sociated human activities,especially agricultureacross the world have not only led to land degrada-tion,but soil loss at rates that have pushed arablesoils to frontier thresholds.In the absence of arablesoil,the human environment would cease to groworeven demise(Ramet al.,2006).Studies haveshownthat in many regions of the world,runoff andsoil erosion differ withland-use type.Judson(1965)re… 相似文献
99.
迄今为止,所有成功的超高频调制光波测距仪均采用频偏法进行同步检测来实现距离测量。本文针对频偏法存在的问题,提出相位偏移法进行同步检测,并介绍实现相位偏移法的具体方案。 相似文献
100.
KANG Shi chang QIN Da he YAO Tan dong PAUL A. Mayewski SALLIE Whitlow 《中国地理科学(英文版)》2000,10(3):218-225
Investigations of atmospheric composition in the Himalayas has been limited in both temporal and spatial scales, mainly due to difficult logistics. Ideal sites for monitoring atmospheric composition and its evolution should be free from local pollution and representative of the remote troposphere (HUEBERT et al., 1980). As the Himalayas are far removed from highly industrialized regions they provide suitable locations to monitor the chemistry of the remote troposphere and to study the evolu… 相似文献