全文获取类型
收费全文 | 1076篇 |
免费 | 34篇 |
国内免费 | 29篇 |
专业分类
测绘学 | 560篇 |
大气科学 | 27篇 |
地球物理 | 30篇 |
地质学 | 149篇 |
海洋学 | 36篇 |
天文学 | 2篇 |
综合类 | 120篇 |
自然地理 | 215篇 |
出版年
2023年 | 3篇 |
2022年 | 36篇 |
2021年 | 34篇 |
2020年 | 28篇 |
2019年 | 24篇 |
2018年 | 17篇 |
2017年 | 65篇 |
2016年 | 36篇 |
2015年 | 47篇 |
2014年 | 49篇 |
2013年 | 56篇 |
2012年 | 132篇 |
2011年 | 66篇 |
2010年 | 52篇 |
2009年 | 38篇 |
2008年 | 61篇 |
2007年 | 62篇 |
2006年 | 53篇 |
2005年 | 44篇 |
2004年 | 39篇 |
2003年 | 41篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 29篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有1139条查询结果,搜索用时 31 毫秒
1.
结合临沂市几年来开展集体建设用地使用权流转的实践和探索,对开展集体建设用地使用权流转的背景、概念及范围进行了论述。认为在计划经济条件下形成的农民集体所有建设用地使用权不能流转的制度已与当前农村经济,特别是小城镇的建设发展严重不适应,允许集体建设用地使用权流转已势在必行。开展集体建设用地使用权流转对保护土地所有者和失地农民的权益,推动小城镇建设健康发展,规范土地市场具有重要意义。 相似文献
2.
Thilde Langevang 《Geoforum》2008,39(6):2039-2047
Studies have shown that the life experiences and future prospects of young people in many parts of the world today are more complex and less predictable than those of past generations. This has led to a recognition of the need to reconsider the conceptual frameworks applied in youth studies. Thus far, research within geography has mainly focused on young people’s paths to adulthood in the Global North or on particularly vulnerable children’s lives in the Global South. In this paper an approach based on the ‘social navigation’ of ‘vital conjunctures’ is adopted to explore the complex ways in which young people in Ghana navigate their way through life in a city marked by economic hardship and neo-liberal reform. The stories of three young people are presented to show the variety of life conditions, the complex social positions they occupy and their various and shifting future imaginations. The actions of these young people are steered by prevailing cultural ideals and social expectations of what a desirable and respectable future entails and by the actual space of possibility in the urban space they move through. It is argued that achieving respectable adulthoods in present-day Accra is a complicated and convoluted journey involving the careful management of social relationships. 相似文献
3.
0421号热带风暴“海马(Haima)”于2004年9月13日12:00在浙江省温州市沿海登陆,登陆后迅速减弱为热带低压,20:00在浙江境内消失.本研究采用物理量诊断分析法,探讨该热带风暴登陆前后涡度场、湿焓场变化对其移向和强度的影响.结果表明,该热带风暴登陆后,涡度(ξ)明显减弱.涡度局地变化(ξ/t)值分布显示,风暴移动方向的后方,涡度减弱的趋势比前方涡度增大的趋势更剧烈;风暴有向其外围(ξ/t)正值中心(即涡度增幅最大)移动的趋势.该热带风暴登陆前、后,湿焓都增大,但登陆后湿焓增大趋势已大大减弱;风暴有向湿焓局地变化(E/t)正值中心移动的趋势,即向能量增强最大的方向移动. 相似文献
4.
This paper addresses an important problem in ship control application—the robust stabilization of underactuated ships on a linear course with comfort. Specifically, we develop a multivariable controller to stabilize ocean surface ships without a sway actuator on a linear course and to reduce roll and pitch simultaneously. The controller adapts to unknown parameters of the ship and constant environmental disturbances induced by wave, ocean current and wind. It is also robust to time-varying environmental disturbances, time-varying change in ship parameters and other motions of the ship such as surge and heave. The roll and pitch can be made arbitrarily small while the heading angle and sway are kept to be in reasonably small bounds. The controller development is based on Lyapunov’s direct method and backstepping technique. A Lipschitz continuous projection algorithm is used to update the estimate of the unknown parameters to avoid the parameters’ drift due to time-varying environmental disturbances. Simulations on a full-scale catamaran illustrate the effectiveness of our proposed controller. 相似文献
5.
The 2002 Reform of the Common Fisheries Policy (CFP) was claimed to be a radical overhaul of a failing system. Several EU fish stocks—particularly North Sea cod—had reached dangerously low levels, and there was widespread dissatisfaction with the way in which the CFP was operating. The European Commission took the opportunity of the legal requirement to review some features of the CFP (principally access provisions) in 2002, to undertake a broader reappraisal of the CFP. One of the features of this reappraisal was an attempt to improve the CFP's system of governance by increasing the amount of stakeholder participation, decentralisation, transparency, accountability, effectiveness and coherence. In this paper, the conclusion is reached that this attempt to improve the quality of governance in the 2002 CFP reform package has been more rhetorical than real. 相似文献
6.
厦门嵩屿附近海底的冲淤变化 总被引:2,自引:0,他引:2
本文通过地形剖面测量比较、浅地层剖面勘探,结合水文泥沙测验和沉积物粒径资料,分析嵩屿附近海域在各历史时期和九江洪水期、枯水期的中淤变鼓水道近十几年来淤积速度加快。其主要原因是该海域动力要素明显减弱,携沙能力降低;其次,九龙江大量的泥沙主要集中在洪水期较短的时间内泄出河口,伴随涨潮流进入嵩鼓水道淤积。 相似文献
7.
高校GIS专业课程设置的探索 总被引:8,自引:4,他引:4
通过对高校地理信息系统(简称GIS)专业基础理论、基本方法、应用技术、与学科最新发展前沿的深入分析,结合GIS专业学生的知识结构体系,提出了一种新的GIS专业基础课和专业课的设置,在对GIS人才的特点和能力培养途径提出了自己建议的同时,对课程内容及教学形式等相关问题进行了相应地探讨。 相似文献
8.
9.
10.
从国库集中收付改革的内容、要求,地质勘查单位的现状出发,探讨了国库集中收付改革与深化地质勘查单位改革之间存在的问题,指出国库集中收付制度虽然能够使事业单位的财政收支得到有效监管,但因地质勘查单位具有事业与企业的双重职能,现行的国库集中收付制度不利于地勘单位的深化改革。为有效解决这一矛盾.提出了在国库单一账户体系外,建立地质勘查单位改革性基本账户的建议。 相似文献