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181.
A spectrum from 1.2 to 2.5 μm of Uranus' small satellite Miranda obtained in June 1999 reveals strong water-ice signatures. It confirms the existence of a 2.0-μm water feature previously detected on Miranda and shows a strong second broad 1.5-μm water-ice absorption feature. The spectra also reveal a weak absorption band at 1.65 μm that is indicative of crystalline water ice. Reflectance models which combine the new spectra with new photometry indicate that the spectra are characteristic of a mostly water-ice surface, with a large fraction of carbonaceous or silicate contaminates, and the possible presence of ammonia hydrate, as implied by an apparent weak feature near 2.2 μm. The possible presence of other volatiles is also investigated.  相似文献   
182.
This paper provides an introduction to the set of articles presented in the focus section Women in Geography in the 21st Century. The paper argues that feminist geographers should view their professional biographies in a structure‐agency context. Such a theoretical perspective views events that are commonly thought to be unique and attributable to individual merit or foible as the outcome instead of interactions between actors and social structures. Creating genuinely equal opportunities in geography departments for women and others who are different from the able‐bodied, middle‐class, white heterosexual male model of “the geographer” depends upon challenges to and transformations of the structures which bear on the discipline, rather than solely upon individual initiative.  相似文献   
183.
The transition from the Viking Age (ca. A.D. 800–1050) to the Medieval period (ca. A.D. 1050–1500) saw the development of widening trade activities that incorporated peripheral North Atlantic polities into mainstream Europe and contributed to the intensification of marineresource exploitation and agricultural production in these localities. As yet, there is only limited understanding of these intensification processes and their interrelationships, particularly at a local, site‐based level. Through the micromorphological analysis of cultural soils and sediments at Quoygrew, Westray, Orkney, we explore the characteristics of farming and fishing activity during the Viking Age–Medieval transition period and establish their chronological relationships. The study demonstrates: (1) that intensification took place from ca. A.D. 966–1162 on an already existing Viking Age settlement, (2) that intensification of fishing activity occurred prior to the intensification of arable agriculture, and (3) that the Quoygrew site continued throughout this period as an economically diverse permanent settlement. When viewed in a wider North Atlantic context, these findings indicate that intensification of different economic activities proceeded at different rates and that intensification of specialized economic activities during the transition from the Viking Age to the Medieval period was dependent on existing knowledge of local environments. © 2005 Wiley Periodicals, Inc.  相似文献   
184.
Adaptation and transformation   总被引:1,自引:0,他引:1  
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185.
186.
The forest realm of the Gòòl‐War watershed of southeast Perak, Malaysia holds much socio‐cultural significance to the Semai Orang Asli communities living along these rivers. Notwithstanding its present‐day location within the Bukit Tapah Forest Reserve, the forest continues to be where Semai conceptions of history and lore are encoded in the geographical particulars of the landscape. A thriving forest‐dependent lifestyle maintains and transmits Semai place knowledge, observed in this research through people's command of ancestral place‐names. This paper provides an introduction to Semai toponymy and considers the implications of indigenous place‐names on the protection of indigenous homelands and ways of life.  相似文献   
187.
Nontimber forest product (NTFP) certification has potential to promote sustainable harvest and to bolster rural livelihoods. This research compares environmental and socioeconomic benefits of Brazil nut certification for 231 producers in 17 communities in the trinational border region of Bolivia, Brazil, and Peru during the 2006–2007 harvest. Specific objectives were: (1) to analyze differences in “best management practices” between certified and noncertified producers; (2) to identify socioeconomic benefits associated with certified nuts; and (3) to explore producer perceptions of nut certification. Organic and Fairtrade certification were associated with better postharvest practices and higher prices, while Forest Stewardship Council (FSC) certification was related to preharvest planning. Certification was viewed most positively in Bolivia, where producers gleaned financial and social benefits, moderately in Peru, and least positively in Brazil, where benefits were lower or nonexistent. Partnerships with cooperatives, donors, government, and nongovernmental organizations were essential to maximize conservation and development objectives.  相似文献   
188.
This paper uses a content analysis of the published literature to take stock of current understanding of key social and policy drivers of migration to cities in 11 Asian and African mega-deltas and identifies commonalities and differences among them. The analysis shows that migration to urban centers in mega-deltas is an outcome of many forces: economic policies and incentives, local and destination institutions, government policies to develop small towns, and the geographic concentration of investments. Massive influx of capital to many deltas has transformed the local economic base from a primarily agricultural one to a manufacturing and processing economy. This has created uneven spatial economic development which is the underlying driver of migration to cities in the mega-deltas regardless of geographic context or size. Going forward to 2060, one critical challenge for all the deltas is to increase the labor skill of their workforce and foster technology innovation. Continued economic growth in these regions will require substantial investments in education and capacity building and the ability of urban centers to absorb the migrant labor pool.  相似文献   
189.
Regime shifts in the marine environment have recently received much attention. To date, however, few large-scale meta-analyses have been carried out due to insufficient data coverage and integration between sustained observational datasets because of diverse methodologies used in data collection, recording and archival. Here we review the available data on regime shifts globally, followed by a review of current and planned policies with relevance to regime shifts.We then focus on the North and Baltic Seas, providing examples of existing efforts for data integration in the MarBEF Network of Excellence. Existing gaps in data coverage are identified, and the added value from meta-analyses of multiple datasets demonstrated using examples from the MarBEF integrated data project LargeNet. We discuss whether these efforts are addressing current policy needs and close with recommendations for future integrated data networks to increase our ability to understand, identify and predict recent and future regime shifts.  相似文献   
190.
This simulation research was conducted in order to develop a large-fire risk assessment system for the contiguous land area of the United States. The modeling system was applied to each of 134 Fire Planning Units (FPUs) to estimate burn probabilities and fire size distributions. To obtain stable estimates of these quantities, fire ignition and growth was simulated for 10,000 to 50,000 “years” of artificial weather. The fire growth simulations, when run repeatedly with different weather and ignition locations, produce burn probabilities and fire behavior distributions at each landscape location (e.g., number of times a “cell” burns at a given intensity divided by the total years). The artificial weather was generated for each land unit using (1) a fire danger rating index known as the Energy Release Component (ERC) which is a proxy for fuel moisture contents, (2) a time-series analysis of ERC to represent daily and seasonal variability, and (3) distributions of wind speed and direction from weather records. Large fire occurrence was stochastically modeled based on historical relationships to ERC. The simulations also required spatial data on fuel structure and topography which were acquired from the LANDFIRE project (). Fire suppression effects were represented by a statistical model that yields a probability of fire containment based on independent predictors of fire growth rates and fuel type. The simulated burn probabilities were comparable to observed patterns across the U.S. over the range of four orders of magnitude, generally falling within a factor of 3 or 4 of historical estimates. Close agreement between simulated and historical fire size distributions suggest that fire sizes are determined by the joint distributions of spatial opportunities for fire growth (dependent on fuels and ignition location) and the temporal opportunities produced by conducive weather sequences. The research demonstrates a practical approach to using fire simulations at very broad scales for purposes of operational planning and perhaps ecological research.  相似文献   
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