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   835篇
  免费   34篇
  国内免费   2篇
测绘学   31篇
大气科学   61篇
地球物理   162篇
地质学   227篇
海洋学   59篇
天文学   230篇
综合类   6篇
自然地理   95篇
  2024年   7篇
  2021年   11篇
  2020年   11篇
  2019年   14篇
  2018年   13篇
  2017年   19篇
  2016年   16篇
  2015年   10篇
  2014年   30篇
  2013年   21篇
  2012年   23篇
  2011年   27篇
  2010年   42篇
  2009年   31篇
  2008年   39篇
  2007年   47篇
  2006年   34篇
  2005年   27篇
  2004年   39篇
  2003年   36篇
  2002年   33篇
  2001年   18篇
  2000年   16篇
  1999年   21篇
  1998年   21篇
  1997年   13篇
  1996年   17篇
  1995年   11篇
  1994年   8篇
  1992年   10篇
  1990年   8篇
  1989年   13篇
  1988年   7篇
  1987年   7篇
  1986年   10篇
  1985年   8篇
  1984年   15篇
  1983年   10篇
  1982年   14篇
  1981年   6篇
  1980年   5篇
  1979年   15篇
  1978年   6篇
  1977年   14篇
  1976年   6篇
  1975年   11篇
  1974年   7篇
  1973年   8篇
  1971年   4篇
  1967年   5篇
排序方式: 共有871条查询结果,搜索用时 937 毫秒
731.
In this paper, we trace the history of tropical architecture beyond its supposed founding moment, that is, its institutionalization and naming‐as‐such, in the mid‐twentieth century. We note that many of the planning principles, spatial configurations and environmental technologies of tropical architecture could be traced to knowledge and practices from the eighteenth century onwards, and we explore three pre‐1950s moments of ‘tropical architecture’ in the British empire through building types such as the bungalow, military barrack and labourers' housing in the tropics. Unlike the depoliticized technical discourse of tropical architecture in the mid‐twentieth century, this earlier history shows that so‐called tropical architecture was inextricably entangled with medical and racial discourses, biopolitics and the political economy of colonialism. We argue that tropical architecture should not be understood as an entity with a fixed essence that is overdetermined by a timeless and unchanging external tropical nature. Rather, tropical architecture should be understood as a set of shifting discourses that privilege tropical nature, especially climate, in various ways as the prime determinant of built form according to different constellations of sociocultural and technoscientific conditions. We thus see ‘tropical architecture’ not as a depoliticized entity but as a power‐knowledge configuration inextricably linked to asymmetrical colonial power relations.  相似文献   
732.
Dhofar 280 recorded a complex history on the Moon revealed by high‐resolution 40Ar‐39Ar dating. Thermal resetting occurred less than 1 Ga ago, and the rock was exposed to several impact events before and afterwards. The cosmic ray exposure (CRE) age spectrum indicates a 400 ± 40 Ma CRE on the lunar surface. A unique feature of this lunar sample is a partial loss of cosmogenic 38Ar, resulting in a (low‐temperature) CRE age plateau of about 1 Ma. This was likely caused by the same recent impact event that reset the (low‐temperature) 40Ar‐39Ar age spectrum and preceded the short transit phase to Earth of ≤1 Ma. Dhofar 280 may be derived from KREEP‐rich lunar frontside terrains, possibly associated with the Copernicus crater or with a recent impact event on the deposits of the South Pole–Aitken basin. Although Dhofar 280 is paired with Dhofar 081, their irradiation and thermal histories on the Moon were different. An important trapped Ar component in Dhofar 280 is “orphan” Ar with a low 40Ar/36Ar ratio. It is apparently a mixture of two components, one endmember with 40Ar/36Ar = 17.5 ± 0.2 and a second less well‐constrained endmember with 40Ar/36Ar ≤10. The presence of two endmembers of trapped Ar, their compositions, and the breccia ages seem to be incompatible with a previously suggested correlation between age or antiquity and the (40Ar/36Ar)trapped ratio (Eugster et al. 2001; Joy et al. 2011a). Alternatively, “orphan” Ar of this impact melt breccia may have an impact origin.  相似文献   
733.
We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan??s global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments??2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector??AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan??s atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel ??gravity battery?? climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14?km altitude and descend down to 3.5?km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini??s discoveries and can likely do so within a New Frontiers budget.  相似文献   
734.
The paper presents contributions to the widespread resilience paradigm from a social science perspective. Certain aspects of social systems, especially their symbolic dimension of meaning, need to be taken into account in the endeavor to research coupled social–ecological systems. Due to the symbolic dimension, disasters are defined as the failure of future expectations, and social resilience is defined as the social system property of avoiding or withstanding disasters. In relation to this, three capacities of social systems (adaptive, coping, and participative) that constitute resilience are presented. The adaptive capacity is the property of a system in which structures are modified to prevent future disasters, whereas the coping capacity is the system’s property of coping with calamitous processes that occurred in the past. The participative capacity is a measure of the system’s ability to change its own structures with regard to interventions by other systems, decreasing the system’s resilience. The concept of resilience provides important epistemological and political insights and can help overcome an orientation tied together with the concept of vulnerability that blocks social capacities for the mitigation of disasters.  相似文献   
735.
This paper advocates the use of Bronfenbrenner’s bioecological theory as a framework to analyse resilience at diverse scales. Bronfenbrenner’s bioecological theory can be employed to (a) benchmark social resilience, (b) target the priority interventions required and (c) measure progress arising from these interventions to enhance resilience to natural disasters. First, the paper explores resilience to natural disasters in the context of climatic change as building resilience is seen as a way to mitigate impacts of natural disasters. Second, concepts of resilience are systematically examined and documented, outlining resilience as a trait and resilience as a process. Third, issues arising in relation to the measurement of resilience are discussed. Fourth, Bronfenbrenner’s bioecological systems theory is described and proffered to model and assess resilience at different scales. Fifth, studies are described which have supported the use of the bioecological systems theory for the study of resilience. Sixth, an example of the use of Bronfenbrenner’s theory is offered and the paper concludes with suggestions for future research using Bronfenbrenner’s theory.  相似文献   
736.
The design of new map projections has up until now required mathematical and cartographic expertise that has limited this activity to a small group of specialists. This article introduces the background mathematics for a software-based method that enables cartographers to easily design new small-scale world map projections. The software is usable even by those without mathematical expertise. A new projection is designed interactively in an iterative process that allows the designer to graphically and numerically assess the graticule, the representation of the continents, and the distortion properties of the new projection. The method has been implemented in Flex Projector, a free and open-source application enabling users to quickly create new map projections and modify existing projections. We also introduce new tools that help evaluate the distortion properties of projections, namely a configurable acceptance index to assess areal and angular distortion, a derived acceptance visualization, and interactive profiles through the distortion space of a projection. To illustrate the proposed method, a new projection, the Cropped Ginzburg VIII projection, is presented.  相似文献   
737.
Chris King 《Geology Today》2006,22(6):227-231
In the UK, the National Science week aims to bring exciting science to the public. As explained on the British Association (BA) website: 'National Science Week aims to celebrate science and its importance to our lives, giving people from everywhere in the UK the chance to participate in science activities and experiments and to engage in science discussions in their local area. … We encourage individuals and organisations to take part …' The Prime Minister has said: 'National Science Week is so important. It encourages people to engage with science through informative and fun events, and provides scientists with an opportunity to talk to people about their research and gain an understanding of the public's views.' Science Week provides a wonderful opportunity for geoscientists to bring their science to the public in ways that will inform and inspire. It takes a day, some preparation, and a willingness to 'be in the front line' of interaction with people of all ages. It needs an engaging jargon-free approach and activities that will 'draw in the punters' and provide them with experiences that they won't easily forget. This article shows ways in which it can be delivered.  相似文献   
738.
A Cosmological model with a viscous fluid in Kaluza-Klein metric is obtained assuming a time-dependent equation of state. The solution is in fact a generalization of an earlier work by Hajj and Boutros for a perfect fluid. It is also found that dimensional reduction of the extra space takes place such that the five-dimensional universe naturally evolves into an effective four-dimensional one. The dynamical behavior of the model is examined and it is also found that with a decrease in extra space the observable 3D space entropy increases thus accounting for the large value of entropy observable at present.  相似文献   
739.
Alcock  C.  Dave  R.  Giammarco  J.  Goldader  J.  Lehner  M.  King  S.-K.  Lee  T.  Wang  A.  Wang  S.-Y.  Wen  C.-Y.  Chen  W. P.  Cook  K.  Marshall  S.  Porrata  R.  Byun  Y.-I.  de Pater  I.  Rice  J.  Lissauer  J. 《Earth, Moon, and Planets》2003,92(1-4):459-464
The Taiwanese–American Occultation Survey (TAOS) seeks to determinethe number and size spectrum for small (~3 km) bodies in the KuiperBelt. This will be accomplished by searching for the brief occultations of brightstars (R~14) by these objects. We have designed and built a specialpurpose photometric monitoring system for this purpose. TAOS comprisesfour 50 cm telescopes, each equipped with a 2048×2048 pixel CCDcamera, in a compact array located in the central highlands of Taiwan. TAOSwill monitor up to 3,000 stars at 5 Hz. The system will go into scientificoperation at the end of 003.  相似文献   
740.
Amber (Part 2)     
R. J King 《Geology Today》2007,23(2):74-77
  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