首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   87183篇
  免费   1193篇
  国内免费   545篇
测绘学   1799篇
大气科学   5736篇
地球物理   16768篇
地质学   31377篇
海洋学   8017篇
天文学   20135篇
综合类   229篇
自然地理   4860篇
  2022年   628篇
  2021年   1072篇
  2020年   1137篇
  2019年   1274篇
  2018年   2590篇
  2017年   2390篇
  2016年   2776篇
  2015年   1399篇
  2014年   2658篇
  2013年   4561篇
  2012年   2904篇
  2011年   3745篇
  2010年   3452篇
  2009年   4339篇
  2008年   3786篇
  2007年   3901篇
  2006年   3610篇
  2005年   2574篇
  2004年   2499篇
  2003年   2324篇
  2002年   2321篇
  2001年   1993篇
  2000年   1992篇
  1999年   1567篇
  1998年   1616篇
  1997年   1494篇
  1996年   1269篇
  1995年   1271篇
  1994年   1074篇
  1993年   1021篇
  1992年   959篇
  1991年   995篇
  1990年   967篇
  1989年   846篇
  1988年   771篇
  1987年   898篇
  1986年   787篇
  1985年   969篇
  1984年   1105篇
  1983年   1055篇
  1982年   967篇
  1981年   923篇
  1980年   817篇
  1979年   777篇
  1978年   752篇
  1977年   635篇
  1976年   642篇
  1975年   629篇
  1974年   603篇
  1973年   671篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
461.
The authors propose a series of general methodological guidelines for animal habitat mapping. These include the use of “summary” indicators (of aggregate effects of environmental conditions on animal populations) as indices for mapping, the combination of laboratory and field work at all but the smallest scales of mapping, and explicit recognition (based on extensive studies of ecological characteristics and life cycles of species being mapped) that habitat boundaries in many cases vary dramatically from vegetation and landscape-geological boundaries. Habitat maps of two study areas are compared with vegetation and landscape maps at identical scales to demonstrate these differences. Translated from: Vestnik Moskovskogo Universiteta, geografiya, 1985, No. 3, pp. 95-101.  相似文献   
462.
The author outlines general principles and methods of predictive or forecast mapping in the USSR, more specifically the use of maps in support of geographic forecasting, i.e., prediction of relationships involved in matter, energy, and other flows of ecosystem components. Maps are employed in all stages of geographic forecasting, particularly to identify spatial patterns which can be extrapolated in space or time and used to predict distributions that are difficult or impossible to determine directly, as well as to graphically portray these expected distributions. A scheme for classifying forecast maps in terms of their orientation in time and space is presented. Translated from: Prognoznoye blogeograficheskoye kartografirovaniye: regional'nyy aspekt, Moscow: Nauka, 1985, pp. 6-24.  相似文献   
463.
The author surveys the use of remote sensing imagery in the study of mass exchange in glaciers, i.e., glacier dynamics resulting from phase changes in the water which they contain. A program of research now underway at the Institute of Geography (USSR Academy of Sciences) in conjunction with the “Priroda” Remote Sensing Center (Moscow) focuses on improving methods of data collection and mapping of glacier dynamics from space imagery, and particularly on identifying natural glacioclimatic zones believed to represent specific mass exchange conditions or regimes. The boundary of glacier nourishment separating areas of accumulation and ablation represents a key glacioclimatic indicator of mass exchange on satellite imagery and aerial photography. Translated from: Geodeziya i kartografiya, 1986, No. 5, pp. 26–31.  相似文献   
464.
A method of complex image processing, i.e., the simultaneous use of various kinds of remote sensing imagery in the mapping and study of geographic features, is outlined. It features the use of computerized techniques (a) to identify shots or frames of auxiliary types of imagery containing the same specific geographic features identified on the principal type of imagery [this through the scanning of code lines containing information about the coordinates of imaging, flight direction and altitude of the plane or sensing platform, etc.], and (b) to precisely locate the features of interest within these shots or frames. Translated from: Izvestiya vysshykh uchebnykh zavededeniy, Geodeziya i aerofotos'yemka, 1986, No. 1, pp. 86–91.  相似文献   
465.
Principles are outlined for the use of sub-satellite soil, air, water, and vegetation samples as an auxiliary source of information in remote sensing studies of vegetation stress caused by air pollution. More specifically, procedures for satellite-synchronous aerial overflights, vegetation transects, water quality measurements, and soil tests are described as a basis for delineating boundaries between areas of vegetation stress and unpolluted areas in an industrialized area in the central Urals. Translated from: Kosmicheskiy monitoring biosfery, Yu. A. Izrael', V. V. Bugrovskiy, and Yu. V. Novikov, eds. Leningrad: Gidrometeoizdat, 1985, pp. 93-99.  相似文献   
466.
Results of experiments in the measurement of heat flux at the ocean-atmosphere boundary layer are described. More specifically, an algorithm is presented for the calculation of the different components of total heat flux (from the ocean into the atmosphere) based on estimates of water temperature, wind velocity, and cloud cover obtained from remote sensing imagery. Use of the algorithm yields values for total heat flux which, when averaged over a ten-day period, are only 10% less accurate than those obtained according to traditional methods (research vessels, buoys, offshore platforms). Translated from: Izvestiya vysshykh uchebnykh zavedeniy, Geodezlya i aerofotos”yemka, 1986, No. 5, pp. 117-120.  相似文献   
467.
468.
A paper devoted to the transformation of cartographic images based on nontraditional systems of scaling (travel time, transport effort, cost, etc.) describes the results of work to develop a more effective algorithm for such transformations, i.e., one which the authors claim provides for the more accurate determination of “transformed” line lengths than possible with earlier methods. Translated from: Izvestiya AN SSSR, seriya geograficheskaya, 1987, No. 4, pp. 105-111.  相似文献   
469.
Principles and objectives governing Soviet thematic mapping of nearby planets are outlined, types of information sources for such mapping categorized, and the suitability of different types of information sources for thematic mapping are evaluated. This is followed by a classification of thematic planetary maps according to type. The need for a standardized, systems approach to the determination of map scales, compilation and generalization, symbolization, and map design is emphasized as an essential prerequisite for the development of complex atlases of individual planets, atlases of “comparative planetology,” and the establishment of “planetary information systems.” Translated by Jay Mitchell; PlanEcon, Inc.; Washington, DC 20005 from: Vestnik Moskovskogo Universiteta, geografiya, 1987, No. 6, pp. 60-67.  相似文献   
470.
An effort is made at developing a theory of map readability, defined as the process of the user's representation of the information of the map in his/her own mind. This can be estimated quantitatively by surrogate measures, which include the speed of map comprehension and accuracy of map interpretation. Levels of psychological representation of map information are incorporated to determine at what stage particular aspects of map knowledge are understood. Thus what readability entails, and the approaches used to measure it (what types of things are comprehended, how fast, and how accurately) will depend upon the level of representation. Translated from: Vestnik Leningradskogo Universiteta, seriya 7 [geologiya, geografiya], 1988, No. 1, pp. 32-37.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号