全文获取类型
收费全文 | 6878篇 |
免费 | 1126篇 |
国内免费 | 1136篇 |
专业分类
测绘学 | 1365篇 |
大气科学 | 609篇 |
地球物理 | 1513篇 |
地质学 | 3278篇 |
海洋学 | 1076篇 |
天文学 | 93篇 |
综合类 | 419篇 |
自然地理 | 787篇 |
出版年
2024年 | 13篇 |
2023年 | 70篇 |
2022年 | 202篇 |
2021年 | 261篇 |
2020年 | 249篇 |
2019年 | 280篇 |
2018年 | 229篇 |
2017年 | 280篇 |
2016年 | 271篇 |
2015年 | 275篇 |
2014年 | 425篇 |
2013年 | 407篇 |
2012年 | 510篇 |
2011年 | 479篇 |
2010年 | 432篇 |
2009年 | 431篇 |
2008年 | 394篇 |
2007年 | 534篇 |
2006年 | 482篇 |
2005年 | 396篇 |
2004年 | 367篇 |
2003年 | 359篇 |
2002年 | 272篇 |
2001年 | 238篇 |
2000年 | 241篇 |
1999年 | 195篇 |
1998年 | 186篇 |
1997年 | 125篇 |
1996年 | 126篇 |
1995年 | 89篇 |
1994年 | 81篇 |
1993年 | 51篇 |
1992年 | 52篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1973年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有9140条查询结果,搜索用时 31 毫秒
991.
侯东城 《成都信息工程学院学报》2001,16(3):203-208
网络生产力是一个复杂的系统,它包括构成要素层次,渗透性因素层次与组合性因素层次而有别于一般生产力的新质。 相似文献
992.
文章介绍了广西石油资源及消费概况 ,特别是阐明石油资源不足的事实。提出实施石油勘探的战略性转移和开源节流的政策 ,抓住有利时机 ,进入国际石油市场 相似文献
993.
Chih-Hsiang Ho 《Mathematical Geology》1992,24(7):775-787
In an important paper, Mulargia et al. (1987) address the importance of quantitative and objective identification of different regimes of a volcano. They develop a procedure based on the two-sample Kolmogorov-Smirnov (K-S) statistic. The K-S test is a general-purpose test that discriminates between two data sets as belonging to two different regimes based on their empirical distribution functions. The empirical distribution function is designed to describe the aggregate behavior of the volcanic activity, and it is constructed from the orders of the length of the collected repose times in each data set. In this article, we use the idea of statistical process control to distinguish between the variation inherent in the observed repose times and the extraordinary variation that signals a real change in the regimes. We construct a table of control limits, and we demonstrate the procedure of regime identification based on a simple control chart. It shows a point outside the control limits almost as soon as the process enters a new regime. The basis of the statistical process control mechanism is a simple Poisson process, which is state of the art. The proposed control charting procedure is an eruption by eruption procedure, which follows the original chronological order of the eruptions. This procedure is applied to the eruptive history of the Mount Etna volcano. The application shows schematically that the procedure presents a visual interpretation of the identified regimes and can be practically translated for tabular or manual use. 相似文献
994.
过去,由于气测录井技术的限制,气测数据被认为是不可靠的,其应用的范围也因此受到了制约。现在,随着气测获取及分析技术所取得的进步,可以得到更为准确的气测数据。为了能充分利用气测资料,通过分析气测数据不同比值的深度曲线图,利用曲线的形态及趋势可以划分岩性界面、划分油气水界面、判断地层流体的渐变、推测盖层的封堵效率、预测石油是否遭受了生物降解以及对不同层位的油源进行初步分析。 相似文献
995.
996.
997.
《The Professional geographer》1982,34(4):458-490
Books reviewed in this article: Aerial Photography and Remote Sensing. Terrain Analysis and Remote Sensing . JOHN R. G. TOWNSHEND , ed. Environmental Data Use in Computer-assisted Data Handling Systems: The Results of a Survey of Applications in the Pacific Northwest States . KENNETH E. GORDON . Applied Land Use: A Spatial Approach . JOHN F. LOUNSBURY , LAWRENCE M. SOMMERS , AND EDWARD A. FERNALD , eds. The Second Battle of New Orleans: A History of the Vieux Carre Riverfront-Expressway Controversy . RICHARD O. BAUMBACH , JR. AND WILLIAM E. BORAH . Cultural Environmental Archaeology . MYRA SHACKLEY . The Immoral landscape: Female Prostitution in Western Societies . RICHARD SYMANSKI . life Among the Poor in Cairo . UNNI WIKAN , translated by Ann Henning. Women, Work and Property in Northwest India . URSULA SHARMA . The Domestication of Women: Discrimination in Developing Societies . BARBARA ROGERS Economic Optimization in Locational and Transport Analysis . A. G. WILSON , J. D. COELHO , S. M. MACGILL , H. C. W. L. WILLIAMS . New Tools for Economic Development: The Enterprise Zone, Development Bank, and RFC . GEORGE STERNLIEB AND DAVID LISTOKIN , eds. Regional Wage Inflation . R. L. MARTIN , ed. Finding A Place For Energy-Siting Coal Conversion Facilities . FRANK J. CALZONETTI WITH MARK S. ECKERT . Environmental Management, Resources, and Systems Environmentalism. Second Edition . T. O'RIORDAN . Countryside Conservation . BRYN GREEN . Medical Spatial Diffusion: An Historical Geography of Epidemics in an Island Community . A. D. CLIFF , P. HAGGETT , J. K. ORD , AND G. R. VERSEY . Philosophy and Geographic Thought Order and Skepticism: Human Geography and the Dialectic of Science . RICHARD SZYMANSKI AND JOHN A. AGNEW . Measurement of Subjective Phenomena . D. F. JOHNSTON , ed. Conceptions of Space in Social Thought: A Geographic Perspective . ROBERT DAVID SACK . The Association of American Geographers: The First Seventy-five Years: 1904-1979 . PRESTON E. JAMES AND GEOFFREY J. MARTIN . The Life and Thought of Isaiah Bowman . GEOFFREY J. MARTIN . Physical River Basin Planning: Theory and Practice . SURANJIT K. SAHA AND CHRISTOPHER J. BARROW , eds. Soils and landforms: An Integration of Ceomorphology and Pedology . A. I. GERRARD Climatic Change and Society. Consequences of Increasing Atmospheric Carbon Dioxide . WILLIAM W. KELLOGG AND ROBERT SCHWARE . Political Political Redistrictings and Geographic Theory . RICHARD L. MORRILL . Population Studies in Spanish American Population History: Dell Plain Latin American Studies NO. 8 . DAVID J. ROBINSON , ed. Population Redistribution in the Midwest . CURTIS C. ROSEMAN , ANDREW J. SOFRANKO , AND JAMES D. WILLIAMS , eds. Geographical Perspectives on the Elderly . A. M. WARNES , ed. Regional Perspective On the American South . MERLE BLACK AND JOHN SHELTON REED , eds. The Prairies and Plains: Prospects for the 80s . JOHN R. ROGGE , ed. Rural Rural Settlement in an Urban World . MICHAEL BUNCE . Social Accident at Three Mile Island: The Human Dimensions . DAVID L. SILLS , C. P. WOLF , AND VIVIEN B. SHELANSKI , eds. The American Small Town: Twentieth-Century Place Images . JOHN JAKLE . Urban A House of My Own . SUSAN LOBO . The City: Patterns and Processes in the Urban Ecosystem . CHRISTOPHER H. EXLINE , GARY L. PETERS , AND ROBERT P. LARKIN . Movement in Cities . P. W. DANIELS AND A. M. WARNES . Urbanization and Urban Planning in Capitalist Society . MICHAEL DEAR AND ALLEN J. SCOT , eds. 相似文献
998.
The organizational separation of management and other quaternary activities from production operations in American manufacturing has resulted in a divergent pattern of production and headquarter locations. We examine the external control relationships that arise from this separation between headquarter location and branch plant operations in nonmetropolitan Kentucky. Although corporate headquarters have diffused to the Sunbelt, no shift was found in the corporate control of branch plants in Kentucky. Nonmetropolitan manufacturing in Kentucky was oriented toward the metropolitan centers of the traditional manufacturing belt rather than the newer corporate centers of the South. Also control relationships are more likely to be local among smaller factories. Large plants having more autonomy in production or producing finished goods were more likely to be owned by a distant firm located in a large SMSA. 相似文献
999.
Methodological Development of the Conditional Sampling Method. Part II: Quality Control Criteria of Relaxed Eddy Accumulation Flux Measurements 总被引:1,自引:1,他引:0
A.?K.?Fotiadi F.?Lohou A.?Druilhet D.?Ser?aEmail author F.?Said P.?Laville A.?Brut 《Boundary-Layer Meteorology》2005,117(3):577-603
Determination of biosphere–atmosphere exchanges requires accurate quantification of the turbulent fluxes of energy and of
a wide variety of trace gases. Relaxed Eddy Accumulation (REA) is a method that has received increasing attention in recent
years, because it does not require any rapid sensor for the scalar measurements as the Eddy Correlation method (EC) does.
As in all micrometeorological studies, REA measurements in the atmospheric surface layer are valid under some restrictive
conditions so as to be representative of a specific ecosystem. These conditions are the homogeneity of the underlying surface,
stationary and horizontally homogeneous turbulence. For most experiments these conditions are not fully satisfied. Data uncertainties
can also be related to not fulfilling the method principles or to the technical characteristics of the REA system itself.
In order to assess REA measurement quality, a methodological approach of data analysis is developed in this study. This methodological
analysis is based on the establishment of criteria for data quality control. A set of them, deduced from the mean and turbulent
flow, are called ‘Dynamic criteria’ and are designated to control the stationarity and homogeneity of the w function and the validation of Taylor’s hypothesis. A second set (‘REA operational criteria’) is designed to check the sampling
process and, more precisely, the homogeneity of the negative and positive selection process throughout the sampling period.
A third set of criteria (‘Chemical scalar criteria’) concerns the scalar measurements. Results of the criteria application
to data measured at two different experimental sites are also presented. Cut-off limits of criteria are defined based on their
statistical distribution and shown to be specific for each site. Strictness of each criterion, defined by the percentage of
flagged samples, is analysed in conjunction with the meteorological conditions and atmospheric stability. It is found that
flagged samples mainly correspond to neutral and stable nocturnal conditions. During daytime, nearly free convection conditions
can also yield poor quality data. 相似文献
1000.
LIU Xuhua WANG Jinfeng LIU Mingliang & MENG Bin . Institute of Geographic Sciences Natural Resources Research Chinese Academy of Sciences Beijing China . Graduate School of the Chinese Academy of Sciences Beijing China . College of Arts Sciences of Beijing Union University Beijing China . School of Forestry Wildlife Sciences Auburn University Auburn Alabama AL USA 《中国科学D辑(英文版)》2005,48(12):2231-2240
Along with the increasing problems of rapid popu-lation increase, resources scarcity and environment deterioration, the interaction between human devel-opment and natural environment changes, especially the Land-Use/Land-Cover, LUCC issue is becoming a frontier and hot field[1], in which investigation on the mechanisms of land use change is one of the three core issues. Deficient natural resources, in particular the shortage of cropland resource in China, are the important constraints to Ch… 相似文献