全文获取类型
收费全文 | 2047篇 |
免费 | 340篇 |
国内免费 | 88篇 |
专业分类
测绘学 | 126篇 |
大气科学 | 84篇 |
地球物理 | 160篇 |
地质学 | 1060篇 |
海洋学 | 322篇 |
天文学 | 1篇 |
综合类 | 214篇 |
自然地理 | 508篇 |
出版年
2024年 | 7篇 |
2023年 | 29篇 |
2022年 | 27篇 |
2021年 | 45篇 |
2020年 | 35篇 |
2019年 | 33篇 |
2018年 | 28篇 |
2017年 | 31篇 |
2016年 | 45篇 |
2015年 | 44篇 |
2014年 | 101篇 |
2013年 | 70篇 |
2012年 | 79篇 |
2011年 | 90篇 |
2010年 | 101篇 |
2009年 | 126篇 |
2008年 | 100篇 |
2007年 | 97篇 |
2006年 | 91篇 |
2005年 | 94篇 |
2004年 | 122篇 |
2003年 | 162篇 |
2002年 | 162篇 |
2001年 | 147篇 |
2000年 | 91篇 |
1999年 | 91篇 |
1998年 | 99篇 |
1997年 | 39篇 |
1996年 | 40篇 |
1995年 | 29篇 |
1994年 | 47篇 |
1993年 | 44篇 |
1992年 | 32篇 |
1991年 | 49篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2475条查询结果,搜索用时 31 毫秒
1.
2.
PRELIMINARY STUDY ON THE FLOODING AND DROUGHT CLAMITY DURING PAST 1500 YEARS IN THE HAI′AN REGION,JIANGSU PROVINCE 总被引:1,自引:0,他引:1
Collection and arrangement of the historical records of climatic changes and environment evolution,espectial-lyin the aspect of calamities,are made on the history documents of past 1500 years about Haiˊan region,Jiangsu Province.There existed two obvious flooding-drought frequently-occurring periods:one was from 1550 AD to 1850 AD and another was 100 AD to 1200AD.The period of 1550 AD to1850 AD is interrupted by two relatively arid and cold climatic periods:one was from 1630 AD to 1700 AD and another was 1750 AD to 1820 AD.The main characteristic of the calamity periods is that they occurred by turns,and sometimes,both drought and flooding occurred in the same year.The instability of the climatic changes in the Little Ice Age may be the main reason of the frequently-occurring flooding and drought in Haiˊan region.Research results also show that the frequently-occurring periods of flooding and drought is in close relationship with the solar activity,and therefore,occurrence of the flooding and drought may be in relation with the intensity of the solar activity.This hypothesis may need further study in the future. 相似文献
3.
MENGLi-li 《中国地理科学(英文版)》2003,13(2):190-192
The exploitation and utilization of the tour resources of tournament athletics, including skiling, boat sail-ing, archery, ice engraving, snow engraving, has become a new trend of the development of Chinese tourism. Due tothe unique cold climate and superior geographic location, Harbin is a promising city for developing tour resources of tourna-ment athletics. Based on the analysis of the superiority and peculiarity of Harbin, the speculation on development of tour resources of tournament athletics in Harbin is proposed as follows : 1 ) Harbin should develop its special tour resources of tournament athletics associated with needs of market; 2) Harbin should take the advantages of rich resources and devel-op ice and snow entertainment in winter and travel for sight-seeing and spending summer;, 3) the adjustment of the layoutof ice and snow resources should be based on the idea of taking Harbin as the center and all-side opening at the largescale in the way of radiation; 4) tourism should be developed by the combined efforts of various departments to make feasi-ble plan, and the organizers should pay much attention to ensuring the safetv of tourists. 相似文献
4.
5.
随着经济的发展,人民生活质量的提高和法制观念的增强,砖瓦窑业生产存在的许多问题也显得日益突出.分析了目前全省砖瓦窑业存在的6个方面的主要问题,并有针对性地提出了对策与建议. 相似文献
6.
系统介绍了江苏省同位素地质年龄数据库的建库工作及取得的主要成果,并针对同位素地质年龄数据库、工作指南和同位素地质测年工作等方面存在的问题提出了对策和建议。 相似文献
7.
8.
LIUXin-wei CHENBai-ming ZHANGDing-xiang 《中国地理科学(英文版)》2004,14(3):209-214
Efficiency and sustainability of grain production are now important in China. In this study, the grain production systems of Jiangsu and Shaanxi Provinces were compared, to analyze their efficiency and sustainability in terms of utilization of natural resources, inputs of purchased energy and materials, and outputs. Flows of energy and materials between environment and human society were identified, and the natural and human work involved in generating inputs as materials or energy were valued in terms of equivalent amount of solar energy required for their production using emergy method. The results showed environmental resources were continually playing a less important role in the systems, when inorganic subsidiary emergy inputs increased drastically while organic ones decreased or increased little. Deterioration of input emergy structure affected the systems‘ efficiency and sustainability, resulting in emergy investment ratios and environmental loading ratios increasing while yield ratios and sustainability indices decreasing. In general, efficiency and sustainability of grain production in Jiangsu are worse than those in Shaanxi. This analysis also suggested that inorganic subsidiary emergy should be introduced properly, and peasants in Jiangsu should utilize natural conditions wisely while those in Shaanxi pay enough attention to soil and surface water conservation. 相似文献
9.
10.
江苏省国土资源厅矿产资源储量处 《江苏国土资源》2003,(3):17-19
介绍了2001年度全省矿产资源储量和矿业建设基本情况,在此基础上,对主要矿产品及其制品进出口贸易、供需形势等情况进行了研究分析。 相似文献