全文获取类型
收费全文 | 723篇 |
免费 | 111篇 |
国内免费 | 198篇 |
专业分类
测绘学 | 104篇 |
大气科学 | 104篇 |
地球物理 | 126篇 |
地质学 | 333篇 |
海洋学 | 69篇 |
天文学 | 119篇 |
综合类 | 48篇 |
自然地理 | 129篇 |
出版年
2024年 | 3篇 |
2023年 | 7篇 |
2022年 | 15篇 |
2021年 | 14篇 |
2020年 | 26篇 |
2019年 | 40篇 |
2018年 | 29篇 |
2017年 | 29篇 |
2016年 | 24篇 |
2015年 | 44篇 |
2014年 | 50篇 |
2013年 | 62篇 |
2012年 | 62篇 |
2011年 | 51篇 |
2010年 | 38篇 |
2009年 | 52篇 |
2008年 | 49篇 |
2007年 | 42篇 |
2006年 | 61篇 |
2005年 | 51篇 |
2004年 | 34篇 |
2003年 | 33篇 |
2002年 | 35篇 |
2001年 | 19篇 |
2000年 | 27篇 |
1999年 | 29篇 |
1998年 | 18篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1032条查询结果,搜索用时 156 毫秒
81.
Simulation of the Direct Radiative Effect of Mineral Dust and Sea Salt Aerosols in a Doubled Carbon Dioxide Climate 下载免费PDF全文
The authors examine the equilibrium climatic response to the direct radiative effect(DRE)of mineral dust and sea salt aerosols in a doubled-CO2climate with two-way coupling of aerosol-climate interactions.In response to the drier and windier conditions,dust emissions increase by 26%in the Sahara Desert and by 18%on the global scale relative to present day.Sea salt emissions increase in high latitudes(60°)but decrease in middle latitudes(30°–60°)of both hemispheres due to the poleward shift of westerlies,leading to a 3%decrease in global emissions.The burdens of dust and sea salt increase by 31%and 7%respectively,because reductions in rainfall over the tropical oceans increase the lifetime of particles in the warmer climate.The higher aerosol loading in the doubled-CO2climate reinforces aerosol DRE by0.2 W m 2,leading to an additional cooling of 0.1°C at the surface compared with the climatic effects of aerosols in present day.The additional cooling from changes in natural aerosols compensates for up to 15%of the regional warming induced by doubled CO2. 相似文献
82.
The significant periods of total solar irradiance are 35 d and 26 d in the 23rd and 24th solar activity cycles, respectively. It is inferred that the solar quasi-rotation periods are also 35 d and 26 d in the 23rd and 24th solar activity cycles, respectively. The value of total solar irradiance around the 24th solar activity minimum may be close to the value of Maunder minimum. On the timescales from one solar rotation period to several months, sunspots are the main reason to cause the variation of total solar irradiance, but not the unique one, and the variation of total solar irradiance are not correlated with the Mg II index on the timescales from a few days to one solar rotation period. 相似文献
83.
ZHENG Chun-xiao CAI Ming-sheng HU Yi-ming HUANG Yong-yi GONG Yi-zhong 《Chinese Astronomy and Astrophysics》2014
The hard X-ray imaging telescope based on the Fourier transform imaging technique is introduced. The double-layer parallel gratings are used to make the modulation and coding on the light emerging from a celestial X-ray source, the modulated light is acquired, to make the optoelectronic conversion by scintillation crystal detectors, and ?nally read out by the electronic system. The modulation collimator X-ray telescopes can be divided into two types: the spatial modulation and temporal modulation. The temporal modulation system requires the scanning motion of the detector system, but the spatial modulation system requires no motion. The technology of grating fabrication is investigated, and the basic structure design of the collimators is given. The principal compo- nents of the prototype hard X-ray imaging telescope of spatial modulation type are successfully developed, including the 8 CsI crystal detector modules (contain- ing photomultipliers or PMTs), 8-channel shaping ampli?ers (two of them are prepared for experiments), and the data acquisition system. And the preliminary test results of the electronic system are also given. 相似文献
84.
85.
86.
87.
�����Ƚ����Ƶ�ֱ����С������Բ��� 总被引:3,自引:0,他引:3
?????????????????????????????????????????????????????????????????????????伸?β????????????????????????????????????????????????????????????????????????С????????????,??Matlab?????????????????????????????????????????????????????????????????????????????Ч???á??????? 相似文献
88.
本文对四川省巴中县莲花山,从1954年开始,在调查研究和规划的基础上,根据造林地条件,提出马尾松栽培技术,取得明显成效。该经验对类似山区有借鉴参考价值。 相似文献
89.
Kang-tsung Chang 《The Professional geographer》1989,41(3):314-328
Japan is the most important foreign investor in the United States. Japanese companies are trade-oriented and have ownership-specific advantages in select industries; their US investment is aimed at protecting their market share. The distribution of Japanese plants correlates well with US manufacturing, except that the West Coast and states that aggressively sought Japanese investment have more employees in Japanese plants. Japanese presence in US manufacturing is most prominent in consumer electronics, steel, automobiles, and high-technology industries. 相似文献
90.
The Meixner functions are utilized to relate the effective rainfall, the direct runoff and the unit hydrograph through linkage equations. The linkage equations are then employed to derive the unit hydrograph for given rainfall-runoff data on a small agricultural watershed. These functions are tested with regard to their ability to reproduce and predict the direct runoff hydrograph. The Meixner functions are found to be an effective analytical tool for hydrograph synthesis. Further, they compare well with the least squares and linear programming methods of the unit hydrograph derivation. 相似文献