全文获取类型
收费全文 | 126634篇 |
免费 | 2149篇 |
国内免费 | 1742篇 |
专业分类
测绘学 | 2973篇 |
大气科学 | 8901篇 |
地球物理 | 25329篇 |
地质学 | 46082篇 |
海洋学 | 11364篇 |
天文学 | 27668篇 |
综合类 | 471篇 |
自然地理 | 7737篇 |
出版年
2022年 | 848篇 |
2021年 | 1409篇 |
2020年 | 1492篇 |
2019年 | 1623篇 |
2018年 | 3241篇 |
2017年 | 3018篇 |
2016年 | 3615篇 |
2015年 | 2039篇 |
2014年 | 3524篇 |
2013年 | 6510篇 |
2012年 | 3999篇 |
2011年 | 5321篇 |
2010年 | 4740篇 |
2009年 | 6008篇 |
2008年 | 5262篇 |
2007年 | 5346篇 |
2006年 | 5100篇 |
2005年 | 3745篇 |
2004年 | 3652篇 |
2003年 | 3433篇 |
2002年 | 3327篇 |
2001年 | 2852篇 |
2000年 | 2849篇 |
1999年 | 2305篇 |
1998年 | 2385篇 |
1997年 | 2245篇 |
1996年 | 1966篇 |
1995年 | 1959篇 |
1994年 | 1673篇 |
1993年 | 1579篇 |
1992年 | 1519篇 |
1991年 | 1469篇 |
1990年 | 1506篇 |
1989年 | 1298篇 |
1988年 | 1248篇 |
1987年 | 1485篇 |
1986年 | 1277篇 |
1985年 | 1625篇 |
1984年 | 1862篇 |
1983年 | 1760篇 |
1982年 | 1583篇 |
1981年 | 1517篇 |
1980年 | 1428篇 |
1979年 | 1322篇 |
1978年 | 1286篇 |
1977年 | 1163篇 |
1976年 | 1156篇 |
1975年 | 1086篇 |
1974年 | 1103篇 |
1973年 | 1188篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
The first find of srilankite (very rare Zr and Ti oxide, Ti2ZrO6) in the Urals and the third find in Russia is reported. Srilankite forms very small (0.5–20 μm) inclusions in some rutile grains. These minerals are observed in the rare rock variety, corundum-bearing spinel–saphirine hornblendite forming a block in serpentinized amphibolizied peridotite of the Ilmeny–Vishnevogorsk Complex, near the village of Taiginka, Chelyabinsk oblast. Srilankite has not been observed in such an association yet. The composition of the host rock provides evidence for its deep (the lowermost crust of the Earth) origin. Srilankites of the Urals are distinguished from all others by the high concentrations of UO2, ThO2, HfO2, and Nb2O5, which provides additional evidence for their crustal origin. Srilankite may indicate high-temperature and high-pressure conditions of rock formation. 相似文献
982.
The atmospheric disturbances caused by the first rocket launch from the Vostochnyi Cosmodrome on April 28, 2016, were registered 10–24 min after the launch using the signals of the GPS/GLONASS global navigation satellite systems. The analysis of the spatial distribution of the disturbances allowed the conclusion that the launch vehicle moved northwest from the cosmodrome, which corresponds to a trajectory of the satellite movement to the orbit with an inclination of 98º. 相似文献
983.
Kevin Stanley L. Kurt Kreuger Priyasree Bhowmik Narjes Shojaati Alexa Elliott 《International journal of geographical information science》2016,30(9):1853-1872
ABSTRACTIn the past decade society has entered a technological period characterized by handheld computing that supports input and processing from numerous sensors. Today’s mobile phones offer the ability to integrate input from sensors monitoring various external and internal sources (e.g., accelerometer, magnetometer, microphone, GPS, wireless Internet, and Bluetooth). Furthermore, these raw inputs can be integrated and processed in ways that can offer novel representations of human behaviour. As a result, new opportunities to examine and better understand human spatial behaviour are available; one such application is the constant monitoring of a group of people over an extended period of time. Such a research setting lends itself to natural experiments that emerge as a result of regular and on-going observations. We report here on the observation of a natural experiment that took place in the context of a month-long monitoring study of 28 participants using mobile phone-based ubiquitous sensor monitoring. The implications for public health and transportation planning are discussed. 相似文献
984.
985.
Richard L. Church 《International journal of geographical information science》2016,30(3):535-553
ABSTRACTThe efficiency of public investments and services has been of interest to geographic researchers for several decades. While in the private sector inefficiency often leads to higher prices, loss of competitiveness, and loss of business, in the public sector inefficiency in service provision does not necessarily lead to immediate changes. In many cases, it is not an entirely easy task to analyze a particular service as appropriate data may be difficult to obtain and hidden in detailed budgets. In this paper, we develop an integrative approach that uses cyber search, Geographic Information System (GIS), and spatial optimization to estimate the spatial efficiency of fire protection services in Los Angeles (LA) County. We develop a cyber-search process to identify current deployment patterns of fire stations across the major urban region of LA County. We compare the results of our search to existing databases. Using spatial optimization, we estimate the level of deployment that is needed to meet desired coverage levels based upon the location of an ideal fire station pattern, and then compare this ideal level of deployment to the existing system as a means of estimating spatial efficiency. GIS is adopted throughout the paper to simulate the demand locations, to conduct location-based spatial analysis, to visualize fire station data, and to map model simulation results. Finally, we show that the existing system in LA County has considerable room for improvement. The methodology presented in this paper is both novel and groundbreaking, and the automated assessments are readily transferable to other counties and jurisdictions. 相似文献
986.
Factors controlling typhoons and storm rain on the Korean Peninsula during the Little Ice Age 总被引:1,自引:0,他引:1
987.
988.
989.
990.