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   1166篇
  免费   60篇
  国内免费   11篇
测绘学   33篇
大气科学   191篇
地球物理   293篇
地质学   502篇
海洋学   36篇
天文学   122篇
综合类   6篇
自然地理   54篇
  2023年   6篇
  2022年   3篇
  2021年   28篇
  2020年   27篇
  2019年   26篇
  2018年   42篇
  2017年   35篇
  2016年   66篇
  2015年   52篇
  2014年   65篇
  2013年   84篇
  2012年   66篇
  2011年   81篇
  2010年   63篇
  2009年   69篇
  2008年   60篇
  2007年   44篇
  2006年   55篇
  2005年   52篇
  2004年   32篇
  2003年   24篇
  2002年   27篇
  2001年   22篇
  2000年   16篇
  1999年   20篇
  1998年   15篇
  1997年   12篇
  1996年   12篇
  1995年   8篇
  1994年   6篇
  1993年   9篇
  1992年   6篇
  1991年   5篇
  1990年   8篇
  1989年   5篇
  1988年   4篇
  1987年   3篇
  1986年   4篇
  1985年   4篇
  1984年   7篇
  1983年   3篇
  1981年   5篇
  1978年   3篇
  1962年   3篇
  1957年   3篇
  1935年   3篇
  1931年   3篇
  1926年   2篇
  1925年   2篇
  1916年   2篇
排序方式: 共有1237条查询结果,搜索用时 31 毫秒
121.
Air pressure field and circulation pattern frequencies were investigated to (1) locate and compare positions of the underlying pressure fields, (2) analyse the spatial dimension of affected areas, (3) create schematic maps of important circulation types and (4) compare the classification types in their response to the data. Two manual classifications were used, selected for the length of their time series and their applicability to a larger region: the Grosswetterlagen classification (GWLc) and the Vangengeim–Girs classification (VGc). Their time series were correlated with a global set of gridded monthly sea-level pressure data. Results show the different conceptual orientation of VGc (hemispheric) and GWLc (continental). The highest correlation values and the largest affected areas are visible in winter, where patterns frequently extended into northern Africa and western Asia. Schematic maps, illustrating the average location of main pressure centres, are provided for basic classes of both classifications. Re-arranging GWLc subtypes increases the classifications comparability with the VGc. Analysis of moving correlation coefficients reveals high fluctuations in the relation of both classifications over time.  相似文献   
122.
The Place of the Old Synagogue is a popular place in the city center of Freiburg, a medium-sized city in southwest Germany. It is going to be redesigned soon. In this paper the impact of urban street design and surface material on human thermal comfort is analyzed using the example of the Place of the Old Synagogue. The models SkyHelios, RayMan, and ENVI-met were applied to quantify and qualify the changes. All three models are freely available. Their combination allows analysis of development in long-term conditions, as well as changes in spatial distribution of thermal comfort, as well as of heat stress in summer. Results show that the models can provide valuable information. About the Place of the Old Synagogue, quantitative results show that the period with heat stress will become longer, while the intensity of heat stress increases. The spatial results show that the most significant changes are due to changes in shading. Nevertheless, an increase in thermal stress up to 10 °C is calculated for areas, where ground coverage changes from grass to pavement.  相似文献   
123.
Air temperature variations in Europe and northern Asia are strongly affected by atmospheric circulation. A large-scale study of temperature signals is presented, using a newly available global gridded daily temperature dataset. Major types of European Grosswetterlagen (large-scale weather patterns) and the Russian Vangengeim–Girs classification are compared in their spatial applicability to air temperatures within the past 110 years (1901–2010). The consistency of spatial patterns in the three most recent decades (1981–2010) is investigated, and temperature changes are interpreted against the backdrop of changes in character and frequency of circulation patterns. Both classifications largely explain the observed temperature variability. Spatial patterns are large-scale and strong in both regions, especially in winter. Both spatial extent and signal magnitude show a distinct seasonality with maximum values in winter and minimum ones in summer. Spatial patterns show little changes in Europe; yet the ability to explain temperature variability in northern Asia decreased within 1981–2010. European winter warming corresponds to increased maritime and to decreased continental air mass inflow, superimposed on the general warming trend. Northern Asian winter warming is partly explainable by circulation changes in January and February, but to a lesser extend in December. These results may be used to advance input variables of global climate models and to improve their performance in the European–Northern Asian area.  相似文献   
124.
ABSTRACT

The continuous submission and scaling-up of Nationally Determined Contributions (NDCs) constitutes a key feature of the Paris Agreement. In their NDCs, states propose governance mechanisms for implementation of climate action, in turn distinguishing appropriate roles for the state in climate governance. Clarity on Parties’ suggested roles for the state makes explicit assumptions on the premise of climate policy, in turn contributing to enhanced transparency in negotiations on the scaling-up of NDCs. This also speaks to ongoing debates on roles for the state in climate governance literature. This article identifies the governance mechanisms proposed by states in their NDCs and the roles for the state envisioned by those governance mechanisms, and also examines how cross-national patterns of roles for the state break or converge with conventional patterns of international politics. The analysis shows that states propose a plurality of roles, which to different extents may be complementary or conflictual. We conclude that income, region, and the Annexes under the United Nations Framework Convention on Climate Change (UNFCCC) are important for understanding suggested roles for the state, but that there are nuances to be further explored. We argue that this paper has three key findings: i) a majority of states rely on market mechanisms to implement their NDCs while rules on implementation and assessment of market mechanisms are still an outstanding issue in the negotiations, meaning that resolving this issue will be essential; ii) the process for evaluating and assessing qualitative governance mechanisms needs to be specified; and iii) increased awareness of differing views on the state’s roles makes explicit different perspectives on what constitutes an ambitious and legitimate contribution to combating climate change.

Key policy insights
  • A majority of states (> 75%) envision the state as regulator (creating and strengthening legislation), market facilitator (creating and maintaining market structures), or facilitator (creating more favourable material conditions for climate-friendly behaviour).

  • Greater awareness of differing views on roles for the state can increase understanding of different perspectives on ambition and legitimacy of contributions, in turn facilitating trust in negotiations.

  • A distinction between substantive and procedural qualitative governance mechanisms and their function and interaction would facilitate the stocktaking dialogues.

  相似文献   
125.
Mountainous regions cover about 27 per cent of the world’s land surface and are home to some 22 per cent of the global population (UNEP 2002). A much greater number of people depend on mountain environments for a wide range of services, including clean water, energy, timber, biodiversity, recreation, and protection from environmental hazards, such as landslides and floods. At the same time, mountain areas are extremely vulnerable ecosystems and under continuous threat of environmental degrad…  相似文献   
126.
Results of a survey of instrumentation and detector systems, either currently deployed or planned for use at telescopes larger than 3.5 m, in ground based observatories world-wide, are presented. This survey revealed a number of instrumentation design trends at optical, near, and mid-infrared wavelengths. Some of the most prominent trends include the development of vastly larger optical detector systems (> 109 pixels) than anything built to date, and the frequent use of mosaics of near-infrared detectors – something that was quite rare only a decade ago in astronomy. Some future science applications for detectors are then explored, in an attempt to build a bridge between current detectors and what will be needed to support the research ambitions of astronomers in the future.  相似文献   
127.
I Zw 1 and 3C 48 are two neighboring template objects at a later stage of the hypothesized merger-driven evolutionary sequence from ultra-luminous infrared galaxies (ULIRGs) to quasi-stellar objects (QSOs). Since galaxy mergers are assumed to trigger the evolution, it is important to confirm the merger properties of transitionary objects. Using multi-wavelength observations and N-body simulations, the merger histories of I Zw 1 and 3C 48 have been investigated in two separate case studies. Here, the results from both studies are compared and their relevance for the evolutionary hypothesis is discussed.This research is partly based on observations with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) under projects 67.B-0009 and 67.B-0019.  相似文献   
128.
Sulfurous acid (H2SO3) has never been characterized or isolated on Earth. This is caused by the unfavorable conditions for H2SO3 within Earth's atmosphere due to the high temperatures, the high water content and the oxidizing environment. Kinetic investigations by means of transition state theory showed that the half-life of H2SO3 at 300 K is 1 day but at 100 K it is increased to 2.7 billion years. Natural conditions to form H2SO3 presumably require cryogenic SO2 or SO2/H2O mixtures and high energy proton irradiation at temperatures around 100 K. Such conditions can be found on the Jupiter moons Io and Europa. Therefore, we calculated IR-spectra of H2SO3 which we compared with Galileo's spectra of Io and Europa. From the available data we surmise that H2SO3 is present on Io and probably but to a smaller extent on Europa.  相似文献   
129.
We address current theories of research on morphology, environment and evolution of active galaxies in the form of a detailed case study of the nearby QSO host I Zw 1. This study is based on sub-kpc resolution 12CO(1-0) observations with the BIMA mm-interferometer and on near-infrared imaging with ISAAC at the VLT. The 12CO(1-0) maps reveal a circumnuclear molecular gas ring with a radius of 0.9 kpc. The imaging data in the J-band are analyzed with respect to a disk-bulge decomposition. Together with a model of the gas rotation curve, the radial profile of the dynamical J-band mass-to-light ratio (M/L) is discussed. The J-band images give new evidence for an interaction between I Zw 1 and its nearby companion. First results from a sequence of N-body simulations for an extensive test of the parameter space of the interaction are presented. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
130.
Ambient seismic noise measurements were conducted inside the Holweide Hospital (Cologne) for checking whether its frequencies of vibration fall into the range where soil amplification is expected. If this is the case, damage might increase in case of an earthquake due to an amplified structural response of the building. Two different techniques were used: the ratio between the horizontal and vertical components of the spectra recorded at stations located inside the building and the ratio between the corresponding components of the spectra recorded simultaneously inside the building and at a reference station placed outside. While the former method might be preferred because of less equipment involved, the latter has the advantage of producing more stable results and deleting automatically the influence of the sedimentary cover, which might obscure some eigenfrequencies of vibration of the building. An independently performed finite-element analysis of the hospital showed a good correlation between measured and calculated eigenmodes.  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