全文获取类型
收费全文 | 3459篇 |
免费 | 337篇 |
国内免费 | 302篇 |
专业分类
测绘学 | 817篇 |
大气科学 | 164篇 |
地球物理 | 411篇 |
地质学 | 864篇 |
海洋学 | 190篇 |
天文学 | 206篇 |
综合类 | 320篇 |
自然地理 | 1126篇 |
出版年
2024年 | 27篇 |
2023年 | 45篇 |
2022年 | 173篇 |
2021年 | 164篇 |
2020年 | 153篇 |
2019年 | 202篇 |
2018年 | 118篇 |
2017年 | 186篇 |
2016年 | 183篇 |
2015年 | 144篇 |
2014年 | 150篇 |
2013年 | 215篇 |
2012年 | 182篇 |
2011年 | 168篇 |
2010年 | 137篇 |
2009年 | 158篇 |
2008年 | 182篇 |
2007年 | 193篇 |
2006年 | 160篇 |
2005年 | 149篇 |
2004年 | 168篇 |
2003年 | 135篇 |
2002年 | 118篇 |
2001年 | 87篇 |
2000年 | 93篇 |
1999年 | 70篇 |
1998年 | 58篇 |
1997年 | 49篇 |
1996年 | 38篇 |
1995年 | 32篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 17篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有4098条查询结果,搜索用时 687 毫秒
941.
网络地图人性化界面设计 总被引:10,自引:0,他引:10
目前网络地图发展迅猛,但界面设计缺少理论指导,仍存在着许多问题.文中首先研究了网络地图的特点和界面内容,对目前网络地图界面设计中存在的突出问题进行归纳.接着提出了基于认知心理学理论的一般性网络地图界面设计原则.最后,对网络地图的用户层次进行分类,举例说明上述设计原则在人性化网络地图界面设计中的应用. 相似文献
942.
As the Mississippi River plays a major role in fulfilling various water demands in North America, accurate prediction of river flow and sediment transport in the basin is crucial for undertaking both short‐term emergency measures and long‐term management efforts. To this effect, the present study investigates the predictability of river flow and suspended sediment transport in the basin. As most of the existing approaches that link water discharge, suspended sediment concentration and suspended sediment load possess certain limitations (absence of consensus on linkages), this study employs an approach that presents predictions of a variable based on history of the variable alone. The approach, based on non‐linear determinism, involves: (1) reconstruction of single‐dimensional series in multi‐dimensional phase‐space for representing the underlying dynamics; and (2) use of the local approximation technique for prediction. For implementation, river flow and suspended sediment transport variables observed at the St. Louis (Missouri) station are studied. Specifically, daily water discharge, suspended sediment concentration and suspended sediment load data are analysed for their predictability and range, by making predictions from one day to ten days ahead. The results lead to the following conclusions: (1) extremely good one‐day ahead predictions are possible for all the series; (2) prediction accuracy decreases with increasing lead time for all the series, but the decrease is much more significant for suspended sediment concentration and suspended sediment load; and (3) the number of mechanisms dominantly governing the dynamics is three for each of the series. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
943.
LI Guowu YANG Guangming MA Zhengsheng SHI Nicheng XIONG Ming FAN Haifu SHENG Ganfu China University of Geosciences 《《地质学报》英文版》2005,79(3):325-331
1 Introduction Chevkinite groups can be assigned to the chevkinite-(Ce) subgroup and perrierite-(Ce) subgroup in accord with the angle β : β ≈ 100o for the chevkinite subgroup and β ≈ 113o for the perrierite subgroup. Chevkinite-(Ce), polykovite-(Ce) and Maoniupingite (new mineral No. 017 of 2003) belong to the former subgroup, while renjeite and matsubaraite belong to the latter group. As strontio-chevkinite is a Sr-analogue of perrierite, usually the natural chevkinite-(Ce) group min… 相似文献
944.
945.
946.
947.
Ivan J. Townshend 《GeoJournal》2006,66(1-2):103-120
The privatization of urban space, as represented in the trend towards a wide variety of common interest developments and increasing
prevalence of gated communities, is an international phenomenon. Recent research has not systematically explored the ways
in which these types of developments are collectively re-shaping the public and private realms of the city at large. This
empirical study of community areas in a Canadian city describes a number of historical private neighbourhood development trends
and their convergence in space and time. Based on the empirical generalizations, a conceptual model is developed to illustrate
how the trends may have combined to produce a new geography or ecology of space privatization within the city, one in which
the older public city is being circumscribed and bounded by new territories of multi-tiered privatization. 相似文献
948.
In the course of the last 50 years, the landscape in Israel has undergone major changes, due to accelerated urbanization following population growth. These processes had increased the pressure on the open land, especially in areas of urban expansion. Recognizing that Governments and local Municipalities had failed to stop the consequent loss of public open spaces, not only in Israel but worldwide, had lead recently many communities to adopt new solutions in the form of private open spaces. In this article we present a “step ahead of time”: a case of privately owned land, set aside as public green area during the 1920s in a neighborhood called “Ahuza Herbert Samuel” (Herbert Samuel, the first High Commissioner of Palestine under the British Mandate), located in the City of Haifa, in Northern Israel. The roots of this unique phenomenon during the 1920s could be linked to several sources of influence: Colonial town planning concepts, the emergence of garden cities and garden suburbs and most importantly to concepts brought in by the leaders of the immigrant community coming from Rumania. Photogrammetric and GIS analysis of this phenomenon had revealed that it had prevailed throughout 75 years of constant and massive increase in the demand for built-up areas in Israel in general and in Ahuza neighborhood in particular. The success in preserving these open areas gains current relevance in view of recent trends in the Western world of allocating privately owned green areas for public use. 相似文献
949.
In Korea most of the old mine workings were worked with room and pillar method or sublevel caving method and today they possess
great possibility of surface subsidence especially for shallow depth mines. In most of the cases, mine roadways, rooms and
pillars are irregular in shape and information about the local geology is uncertain. For these reasons, it is difficult to
standardize the estimating method of subsidence especially sinkhole type over abandoned mine area. This paper describes the
application procedure for the fuzzy reasoning techniques to analyze the possibility of sinkhole occurrences over abandoned
mines. This technique is implemented in software which can simplify the analysis procedure and present the possibility of
sinkhole subsidence without having precise information about local geological/mining conditions. This technique has been applied
to forecast sinkhole possibilities at Bonghwa site where a massive sinkhole has already been occurred. 相似文献
950.
一种城市形态中的空间可视分析方法 总被引:4,自引:0,他引:4
空间可视分析是空间句法的重要依据,是进行城市空间形态分析的新方法。在视域的行为指导原理上,采用可视集中性的概念来进行可视分析,进而通过可视分析各参数的具体量化,包括视域面积、视线长度等,将其应用到具体的城市街道形态中,分析各参数量化大小的分布情况。研究城市形态中可视分析通过“视域法则”影响人的行为,从而潜在决定城市内有关行人等基础设施的布局情况,现实中的设施分布也证明了这种分析的正确性。以武汉市中南地区为分析实例,说明上述各过程,验证城市形态对空间设施分布的影响。 相似文献