全文获取类型
收费全文 | 37962篇 |
免费 | 991篇 |
国内免费 | 1073篇 |
专业分类
测绘学 | 963篇 |
大气科学 | 2944篇 |
地球物理 | 7824篇 |
地质学 | 13983篇 |
海洋学 | 3407篇 |
天文学 | 8212篇 |
综合类 | 250篇 |
自然地理 | 2443篇 |
出版年
2022年 | 294篇 |
2021年 | 483篇 |
2020年 | 462篇 |
2019年 | 499篇 |
2018年 | 935篇 |
2017年 | 895篇 |
2016年 | 1078篇 |
2015年 | 748篇 |
2014年 | 1067篇 |
2013年 | 1903篇 |
2012年 | 1364篇 |
2011年 | 1844篇 |
2010年 | 1605篇 |
2009年 | 2053篇 |
2008年 | 1732篇 |
2007年 | 1799篇 |
2006年 | 1720篇 |
2005年 | 1244篇 |
2004年 | 1159篇 |
2003年 | 1052篇 |
2002年 | 1018篇 |
2001年 | 855篇 |
2000年 | 833篇 |
1999年 | 680篇 |
1998年 | 724篇 |
1997年 | 701篇 |
1996年 | 579篇 |
1995年 | 566篇 |
1994年 | 483篇 |
1993年 | 425篇 |
1992年 | 422篇 |
1991年 | 390篇 |
1990年 | 461篇 |
1989年 | 377篇 |
1988年 | 358篇 |
1987年 | 440篇 |
1986年 | 349篇 |
1985年 | 431篇 |
1984年 | 538篇 |
1983年 | 458篇 |
1982年 | 455篇 |
1981年 | 407篇 |
1980年 | 423篇 |
1979年 | 365篇 |
1978年 | 347篇 |
1977年 | 341篇 |
1976年 | 310篇 |
1975年 | 298篇 |
1974年 | 315篇 |
1973年 | 340篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
321.
J. I. Rostovceva A. N. Stafeev T. V. Sukhanova I. V. Latysheva V. L. Kosorukov 《Moscow University Geology Bulletin》2016,71(4):281-289
Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes. 相似文献
322.
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
323.
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
324.
325.
Fokin P. A. Zakrevskaya E. Yu. Sahakyan L. G. Grigoryan T. E. 《Lithology and Mineral Resources》2021,56(5):438-459
Lithology and Mineral Resources - Nummulite facies are known to be a good indicator of Eocene shallow-water paleoenvironments. Nummulitic limestones are widespread in the Lower Eocene of... 相似文献
326.
Astronomy Reports - An algorithm has been developed for finding the global minimum of a multidimensional error function by fitting model spectral maps into observed ones. Principal component... 相似文献
327.
328.
Oceanology - A new area of oceanography, operational oceanography, involves a comprehensive assessment and forecast of the variability of the state of the marine environment. This requires... 相似文献
329.
The onset of the confinement transition in the early universe is studied within the Friedmann model. Exploiting a bag model equation of state for the deconfined matter, which is generalized to include also metastable states, the possibility of a mini-inflationary epoch is demonstrated. A criterion of metastability is derived to estimate parameters of this mini-inflation. 相似文献
330.
Michael J. Steventon Christopher A.‐L. Jackson David M. Hodgson Howard D. Johnson 《Basin Research》2019,31(3):600-620
Strain style, magnitude and distribution within mass‐transport complexes (MTCs) are important for understanding the process evolution of submarine mass flows and for estimating their runout distances. Structural restoration and quantification of strain in gravitationally driven passive margins have been shown to approximately balance between updip extensional and downdip contractional domains; such an exercise has not yet been attempted for MTCs. We here interpret and structurally restore a shallowly buried (c. 1,500 mbsf) and well‐imaged MTC, offshore Uruguay using a high‐resolution (12.5 m vertical and 15 × 12.5 m horizontal resolution) three‐dimensional seismic‐reflection survey. This allows us to characterise and quantify vertical and lateral strain distribution within the deposit. Detailed seismic mapping and attribute analysis shows that the MTC is characterised by a complicated array of kinematic indicators, which vary spatially in style and concentration. Seismic‐attribute extractions reveal several previously undocumented fabrics preserved in the MTC, including internal shearing in the form of sub‐orthogonal shear zones, and fold‐thrust systems within the basal shear zone beneath rafted‐blocks. These features suggest multiple transport directions and phases of flow during emplacement. The MTC is characterised by a broadly tripartite strain distribution, with extensional (e.g. normal faults), translational and contractional (e.g. folds and thrusts) domains, along with a radial frontally emergent zone. We also show how strain is preferentially concentrated around intra‐MTC rafted‐blocks due to their kinematic interactions with the underlying basal shear zone. Overall, and even when volume loss within the frontally emergent zone is included, a strain difference between extension (1.6–1.9 km) and contraction (6.7–7.3 km) is calculated. We attribute this to a combination of distributed, sub‐seismic, ‘cryptic’ strain, likely related to de‐watering, grain‐scale deformation and related changes in bulk sediment volume. This work has implications for assessing MTCs strain distribution and provides a practical approach for evaluating structural interpretations within such deposits. 相似文献