全文获取类型
收费全文 | 48467篇 |
免费 | 1790篇 |
国内免费 | 2519篇 |
专业分类
测绘学 | 2184篇 |
大气科学 | 4203篇 |
地球物理 | 9626篇 |
地质学 | 17907篇 |
海洋学 | 4672篇 |
天文学 | 10142篇 |
综合类 | 562篇 |
自然地理 | 3480篇 |
出版年
2022年 | 488篇 |
2021年 | 633篇 |
2020年 | 633篇 |
2019年 | 699篇 |
2018年 | 1106篇 |
2017年 | 1017篇 |
2016年 | 1413篇 |
2015年 | 1101篇 |
2014年 | 1370篇 |
2013年 | 2639篇 |
2012年 | 1652篇 |
2011年 | 2201篇 |
2010年 | 1838篇 |
2009年 | 2509篇 |
2008年 | 2249篇 |
2007年 | 2144篇 |
2006年 | 2058篇 |
2005年 | 1791篇 |
2004年 | 1692篇 |
2003年 | 1552篇 |
2002年 | 1519篇 |
2001年 | 1345篇 |
2000年 | 1291篇 |
1999年 | 1108篇 |
1998年 | 997篇 |
1997年 | 989篇 |
1996年 | 860篇 |
1995年 | 758篇 |
1994年 | 663篇 |
1993年 | 598篇 |
1992年 | 585篇 |
1991年 | 558篇 |
1990年 | 552篇 |
1989年 | 485篇 |
1988年 | 465篇 |
1987年 | 538篇 |
1986年 | 495篇 |
1985年 | 582篇 |
1984年 | 639篇 |
1983年 | 623篇 |
1982年 | 582篇 |
1981年 | 521篇 |
1980年 | 483篇 |
1979年 | 440篇 |
1978年 | 438篇 |
1977年 | 398篇 |
1976年 | 362篇 |
1975年 | 372篇 |
1974年 | 362篇 |
1973年 | 370篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
J. García-Abdeslem J.M. Romo E. Gómez-Treviño J. Ramírez-Hernández F.J. Esparza-Hernández C.F. Flores-Luna 《Geophysical Prospecting》2005,53(6):755-765
The subsurface geometry of the Sebastián Vizcaíno Basin is obtained from the 2D inversion of gravity data, constrained by a density-versus-depth relationship derived from an oil exploration deep hole. The basin accumulated a thick pile of marine sediments that evolved in the fore-arc region of the compressive margin prevalent along western North America during Mesozoic and Tertiary times. Our interpretation indicates that the sedimentary infill in the Sebastián Vizcaíno Basin reaches a maximum thickness of about 4 km at the centre of a relatively symmetric basin. At the location of the Suaro-1 hole, the depth to the basement derived from this work agrees with the drilled interface between calcareous and volcaniclastic members of the Alisitos Formation. A sensitivity analysis strongly suggests that the assumed density function leads to a nearly unique solution of the inverse problem. 相似文献
93.
94.
95.
96.
97.
The Karst Feature Database (KFD) of Minnesota is a relational GIS-based Database Management System (DBMS). Previous karst feature datasets used inconsistent attributes to describe karst features in different areas of Minnesota. Existing metadata were modified and standardized to represent a comprehensive metadata for all the karst features in Minnesota. Microsoft Access 2000 and ArcView 3.2 were used to develop this working database. Existing county and sub-county karst feature datasets have been assembled into the KFD, which is capable of visualizing and analyzing the entire data set. By November 17 2002, 11,682 karst features were stored in the KFD of Minnesota. Data tables are stored in a Microsoft Access 2000 DBMS and linked to corresponding ArcView applications. The current KFD of Minnesota has been moved from a Windows NT server to a Windows 2000 Citrix server accessible to researchers and planners through networked interfaces. 相似文献
98.
The summer weather characteristics of the Grove Mountain, East Antarctica, are presented based on the data obtained by Chinese National Antarctic Expedition (CHINARE) in January 1999. The result shows that the pattern of daily variation of temperature and the prevailing wind direction in Grove is similar to that of Zhongshan Station. However, the daily range of temperature and strong wind frequency are much higher than those of Zhongshan Station. The change of wind direction is close to the weather system that impacted the Grove Mountain. The warm and wet air from northern parts often causes the precipitation. The clear weather appears when controlled by eastern winds in January. 相似文献
99.
高速远程崩滑动力学的研究现状及发展趋势 总被引:11,自引:0,他引:11
高速远程崩滑动力学机理的研究,一直是国内外工程地质与山地灾害领域崩塌、滑坡灾害研究的前沿热点问题。对这一研究领域,最近几十年来所取得的研究成果、研究现状及发展趋势进行了述评。厘定了高速远程崩滑的定义;详细地阐述了国内外众多典型重大高速远程崩滑灾害事件的几何学、运动学特征;概述了迄今为止所提出的高速远程崩滑形成的各种动力学机理;分析与讨论了高速远程崩滑动力学机理研究的发展趋势与动向;提出了今后进一步研究的总体思路、目标与应重点解决的关键问题。 相似文献
100.
In 1958, researchers from the University of Chicago documented increases in the number of structures in the floodplains of 17 American cities, a phenomenon attributed to the prevalence of flood control structures. Because federal policies have shifted to managing floodplains, this paper updates the 1958 study for nine of the cities. Several trends are apparent. Development pressures determine flood-plain encroachment; floodplain management regulations have been implemented where it was easiest to do so. Further, structural measures continue to dominate. Thus, while many local officials are becoming more aware of advantages of flood-plain regulation, implementation and enforcement are inconsistent and uneven. 相似文献