全文获取类型
收费全文 | 2003篇 |
免费 | 521篇 |
国内免费 | 1093篇 |
专业分类
测绘学 | 138篇 |
大气科学 | 2130篇 |
地球物理 | 308篇 |
地质学 | 543篇 |
海洋学 | 241篇 |
天文学 | 7篇 |
综合类 | 106篇 |
自然地理 | 144篇 |
出版年
2024年 | 31篇 |
2023年 | 51篇 |
2022年 | 81篇 |
2021年 | 106篇 |
2020年 | 112篇 |
2019年 | 131篇 |
2018年 | 111篇 |
2017年 | 98篇 |
2016年 | 99篇 |
2015年 | 98篇 |
2014年 | 159篇 |
2013年 | 130篇 |
2012年 | 154篇 |
2011年 | 144篇 |
2010年 | 144篇 |
2009年 | 167篇 |
2008年 | 109篇 |
2007年 | 193篇 |
2006年 | 195篇 |
2005年 | 165篇 |
2004年 | 153篇 |
2003年 | 169篇 |
2002年 | 125篇 |
2001年 | 114篇 |
2000年 | 127篇 |
1999年 | 101篇 |
1998年 | 79篇 |
1997年 | 60篇 |
1996年 | 57篇 |
1995年 | 37篇 |
1994年 | 48篇 |
1993年 | 20篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1982年 | 1篇 |
排序方式: 共有3617条查询结果,搜索用时 15 毫秒
1.
After the survey of pollution sources, a study on surface water quality assessment and forecast is given by means of grey
system method, fuzzy mathematical method and multiple-index method. Based on it, aquatic environment quality features, treatment
measures and environmental strategies of the area are proposed. The quality of aquatic environment of 5 rivers in the Tumen
River area is studied. The results show that the pollution of surface water is serious; water quality of most rivers is between
grade IV and V except the Hunchun River, being higher than grade IV standard; pollution levels of most rivers have been basically
controlled except the of Burhatong River, which is deteriorating gradually. Pollutants of the rivers are comparatively regular,
mainly are SS, COD, BOD, AR-OH, NH3-N. The main pollution trades are chemical fibre industry, pulp and paper making industry and mining industry. If the growth
rate of gross industrial product is higher than 25 percent under the encouraging-model of regional exploitation, the pollutants’
load will overtake the bearing capacity of aquatic environment. Thus some protection program against pollution must be worked
out in order to achieve the harmonious development of economy society and environment.
A project from “Studies on Earlier Stage of Regional Development” of the Chinese Academy of Sciences 相似文献
2.
利用西安数字地震遥测台网记录的数字地震资料,采用P波初动半周期残差法求得1998年7月临猗5.0级地震前后不同路径的Q(品质因子)值变化,发现在地震发生前Q值为87~203,震后Q值为67~164,震前震中区附近出现明显的高Q值异常。结果表明,地震前的高Q值异常可以作为地震预测的一种手段。 相似文献
3.
David P. Bacon Nash’at N. Ahmad Thomas J. Dunn Michael C. Monteith Ananthakrishna Sarma 《Natural Hazards》2008,44(3):317-327
By definition, a crisis is a situation that requires assistance to be managed. Hence, response to a crisis involves the merging
of local and non-local emergency response personnel. In this situation, it is critical that each participant: (1) know the
roles and responsibilities of each of the other participants; (2) know the capabilities of each of the participants; and (3)
have a common basis for action. For many types of natural disasters, this entails having a common operational picture of the unfolding events, including detailed information on the weather, both current and forecasted, that may impact on either
the emergency itself or on response activities. The Consequences Assessment Tool Set (CATS) is a comprehensive package of
hazard prediction models and casualty and damage assessment tools that provides a linkage between a modeled or observed effect
and the attendant consequences for populations, infrastructure, and resources, and, hence, provides the common operational
picture for emergency response. The Operational Multiscale Environment model with Grid Adaptivity (OMEGA) is an atmospheric
simulation system that links the latest methods in computational fluid dynamics and high-resolution gridding technologies
with numerical weather prediction to provide specific weather analysis and forecast capability that can be merged into the
geographic information system framework of CATS. This paper documents the problem of emergency response as an end-to-end system
and presents the integrated CATS–OMEGA system as a prototype of such a system that has been used successfully in a number
of different situations. 相似文献
4.
5.
6.
7.
8.
9.
本文探讨东海区近海强风预报模式,首先介绍建立预报模式的思路和步骤,及使用说明,为了验证强风预报模式和判别条件,用1986、1987上日本传真天气图进行试报,准确和基本准确度为91.1%,并给出了1989、1995年随船试验预报结果,准确和基本准确率为90%以上。 相似文献
10.
本文结合实际应用介绍一种人工智能系统。系统的重要特点是,根据预报指标经验知识的产生过程的机理性知识所设计成功的系统主程序之一的“预报指标自动归纳程序”,能够通过对多因子历史资料的分析归纳,自动生成含有较全面知识规则的规则库。有关专家只须凭感性经验提供可能因子和原始资料,系统便能帮助升华出理性的经验规则,自动建成某一专项业务的应用预报系统。对这种“母系统”的反复使用,就可以根据不同类别的资料生成相应的多种应用系统。既适用于气象上风雨暑寒各类天气预报,也适用于其他某些专业,如水文、地震等的定性预报或分析。 本文除简单介绍系统的构造、功能、设计原理之外,还给出一个应用实例,介绍了如何使用本系统去产生应用性系统的具体方法步骤。 相似文献