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   359篇
  免费   16篇
  国内免费   3篇
测绘学   3篇
大气科学   53篇
地球物理   76篇
地质学   122篇
海洋学   34篇
天文学   43篇
综合类   1篇
自然地理   46篇
  2021年   6篇
  2020年   3篇
  2019年   7篇
  2018年   11篇
  2017年   8篇
  2016年   18篇
  2015年   14篇
  2014年   14篇
  2013年   15篇
  2012年   14篇
  2011年   17篇
  2010年   9篇
  2009年   25篇
  2008年   8篇
  2007年   9篇
  2006年   14篇
  2005年   10篇
  2004年   8篇
  2003年   10篇
  2002年   14篇
  2001年   3篇
  2000年   11篇
  1998年   11篇
  1997年   4篇
  1995年   4篇
  1994年   3篇
  1993年   5篇
  1992年   3篇
  1990年   4篇
  1989年   3篇
  1988年   4篇
  1986年   3篇
  1985年   4篇
  1984年   5篇
  1983年   4篇
  1981年   5篇
  1978年   7篇
  1977年   2篇
  1976年   4篇
  1975年   4篇
  1974年   6篇
  1973年   5篇
  1972年   2篇
  1971年   2篇
  1969年   2篇
  1968年   2篇
  1967年   2篇
  1965年   4篇
  1962年   2篇
  1959年   2篇
排序方式: 共有378条查询结果,搜索用时 15 毫秒
61.
62.
63.
Albuquerque, New Mexico is the filming location and setting of the popular television drama Breaking Bad (2008–2013). Albuquerque is not merely a passive backdrop to the action in the show but a focal point of the series. So much so that in the geographical imaginations of many, Albuquerque and Breaking Bad have become synonymous with each other. This paper critically examines the representation of urban life within the show. To do this it draws upon and expands the existing multi-disciplinary literature on cities and films/television. As well as focusing on the influence of setting and filming the show in Albuquerque on the urban diegesis (i.e. the on-screen city), it also examines three visions of Albuquerque that are projected through the show: (1) Albuquerque as a crime-ridden city; (2) Albuquerque as a spatially divided city; and (3) Albuquerque as a city to escape from.  相似文献   
64.
65.
66.
Stream temperature is a key physical water‐quality parameter, controlling many biological, chemical, and physical processes in aquatic ecosystems. Maintenance of cool stream temperatures during summer is critical for high‐quality aquatic habitat. As such, transmission of warm water from small, nonfish‐bearing headwater streams after forest harvesting could cause warming in downstream fish‐bearing stream reaches with negative consequences. In this study, we evaluate (a) the effects of contemporary forest management practices on stream temperature in small, headwater streams, (b) the transmission of thermal signals from headwater reaches after harvesting to downstream fish‐bearing reaches, and (c) the relative role of lithology and forest management practices in influencing differential thermal responses in both the headwater and downstream reaches. We measured summer stream temperatures both preharvest and postharvest at 29 sites—12 upstream sites (4 reference, 8 harvested) and 17 downstream sites (5 reference, 12 harvested)—across 3 paired watershed studies in western Oregon. The 7‐day moving average of daily maximum stream temperature (T7DAYMAX) was greater during the postharvest period relative to the preharvest period at 7 of the 8 harvested upstream sites. Although the T7DAYMAX was generally warmer in the downstream direction at most of the stream reaches during both the preharvest and postharvest period, there was no evidence for additional downstream warming related to the harvesting activity. Rather, the T7DAYMAX cooled rapidly as stream water flowed into forested reaches ~370–1,420 m downstream of harvested areas. Finally, the magnitude of effects of contemporary forest management practices on stream temperature increased with the proportion of catchment underlain by more resistant lithology at both the headwater and downstream sites, reducing the potential for the cooling influence of groundwater.  相似文献   
67.
68.
The preproposal stage of the rulemaking process is notoriously understudied, but enormously important in determining regulatory outputs. Recently, Rinfret (2011c Rinfret , S. R. 2011c . Frames of influence: U.S. environmental rulemaking case studies . Rev. Policy Res. 28 ( 3 ): 231245 .[Crossref], [Web of Science ®] [Google Scholar]) analyzed the U.S. Fish and Wildlife Service (USFWS) rulemaking process and developed a frame analysis model to interpret stakeholder influence during the preproposal stage. Rinfret argues that stakeholders use three frames to influence agency rulemaking, including an expertise, a fiscal feasibility, and an information frame. This article tests this model to determine whether it is applicable to other federal agencies such as the National Park Service (NPS). Through an analysis of stakeholder framing within the 2012 NPS Yellowstone Winter Use Rule, this research confirms that Rinfret's model is indeed applicable to the NPS process. Therefore, this research suggests that this theoretical model examining stakeholder influence is applicable to other public land agencies, and arguably can be applied across the bureaucracy.  相似文献   
69.
Agricultural intensification in South Asia has resulted in the expansion and intensification of surface irrigation over the twentieth century. The resulting changes to the surface energy balance could affect the temperature contrasts between the South Asian land surface and the equatorial Indian Ocean, potentially altering the South Asian Summer Monsoon (SASM) circulation. Prior studies have noted apparent declines in the monsoon intensity over the twentieth century and have focused on how altered surface energy balances impact the SASM rainfall distribution. Here, we use the coupled Goddard Institute for Space Studies ModelE-R general circulation model to investigate the impact of intensifying irrigation on the large-scale SASM circulation over the twentieth century, including how the effect of irrigation compares to the impact of increasing greenhouse gas (GHG) forcing. We force our simulations with time-varying, historical estimates of irrigation, both alone and with twentieth century GHGs and other forcings. In the irrigation only experiment, irrigation rates correlate strongly with lower and upper level temperature contrasts between the Indian sub-continent and the Indian Ocean (Pearson’s r = ?0.66 and r = ?0.46, respectively), important quantities that control the strength of the SASM circulation. When GHG forcing is included, these correlations strengthen: r = ?0.72 and r = ?0.47 for lower and upper level temperature contrasts, respectively. Under irrigated conditions, the mean SASM intensity in the model decreases only slightly and insignificantly. However, in the simulation with irrigation and GHG forcing, inter-annual variability of the SASM circulation decreases by ~40 %, consistent with trends in the reanalysis products. This suggests that the inclusion of irrigation may be necessary to accurately simulate the historical trends and variability of the SASM system over the last 50 years. These findings suggest that intensifying irrigation, in concert with increased GHG forcing, is capable of reducing the variability of the simulated SASM circulation and altering the regional moisture transport by limiting the surface warming and reducing land–sea temperature gradients.  相似文献   
70.
The C1XS X-ray Spectrometer on Chandrayaan-1   总被引:1,自引:0,他引:1  
The Chandrayaan-1 X-ray Spectrometer (C1XS) is a compact X-ray spectrometer for the Indian Space Research Organisation (ISRO) Chandrayaan-1 lunar mission. It exploits heritage from the D-CIXS instrument on ESA's SMART-1 mission. As a result of detailed developments to all aspects of the design, its performance as measured in the laboratory greatly surpasses that of D-CIXS. In comparison with SMART-1, Chandrayaan-1 is a science-oriented rather than a technology mission, leading to far more favourable conditions for science measurements. C1XS is designed to measure absolute and relative abundances of major rock-forming elements (principally Mg, Al, Si, Ca and Fe) in the lunar crust with spatial resolution ?25 FWHM km, and to achieve relative elemental abundances of better than 10%.  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