全文获取类型
收费全文 | 45819篇 |
免费 | 4345篇 |
国内免费 | 6326篇 |
专业分类
测绘学 | 3028篇 |
大气科学 | 6377篇 |
地球物理 | 10281篇 |
地质学 | 22252篇 |
海洋学 | 4246篇 |
天文学 | 2519篇 |
综合类 | 4048篇 |
自然地理 | 3739篇 |
出版年
2024年 | 102篇 |
2023年 | 384篇 |
2022年 | 1034篇 |
2021年 | 1220篇 |
2020年 | 992篇 |
2019年 | 1130篇 |
2018年 | 5650篇 |
2017年 | 4927篇 |
2016年 | 3656篇 |
2015年 | 1364篇 |
2014年 | 1436篇 |
2013年 | 1510篇 |
2012年 | 2292篇 |
2011年 | 3933篇 |
2010年 | 3319篇 |
2009年 | 3496篇 |
2008年 | 2890篇 |
2007年 | 3410篇 |
2006年 | 951篇 |
2005年 | 1003篇 |
2004年 | 931篇 |
2003年 | 984篇 |
2002年 | 858篇 |
2001年 | 638篇 |
2000年 | 751篇 |
1999年 | 1038篇 |
1998年 | 899篇 |
1997年 | 832篇 |
1996年 | 795篇 |
1995年 | 734篇 |
1994年 | 638篇 |
1993年 | 535篇 |
1992年 | 446篇 |
1991年 | 315篇 |
1990年 | 249篇 |
1989年 | 213篇 |
1988年 | 204篇 |
1987年 | 117篇 |
1986年 | 117篇 |
1985年 | 78篇 |
1984年 | 59篇 |
1983年 | 61篇 |
1982年 | 59篇 |
1981年 | 61篇 |
1980年 | 59篇 |
1979年 | 32篇 |
1978年 | 17篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1958年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
DharmalingamVENUGOPAL 《山地科学学报》2004,1(1):74-80
The Nilgiri Mountains of south India is considered unique by anthropologists, geologists, climatologists, botanists as well as tourists. It has remained a subject of constant study and research over the last two centuries. Man-nature balance had continued undisturbed in the Nilgiris for thousands of years until the early 19th century when it became a British colony attracting, in due course, various developmental activities. Subsequently, the Nilgiris and its popular hill stations emerged as favourite places for the British population in India for rest and recuperation, game and for raising commercial plantations. In the process, the traditional indigenous crops were replaced by “English“ vegetables and the natural forests gave way to commercial plantations of coffee, tea and other exotic species of trees. 相似文献
82.
高从堦 《中国海洋湖沼学报》2003,21(1):40-45
Seawater desalination has been people‘s fond dream since ancient times,the dream is now becoming a reality.This paper presents a brief development history of reverse osmosis.Much attention was paid to innovative development in mebranes,modules.equipments and applied technology,including asymmetric and composite membranes,spiral-wound element and hollow fiber module,energy recovery equipments and different technological processes.The extension of reverse osmosis,such as desalination,pre-concentration,integrated processes and nanofiltration,is also briefly mentioned. 相似文献
83.
84.
本文论述了保安地区火山岩的地质、岩石、副矿物、岩石化学、微量元素、稀土元素、稳定同位素、火山岩相及火山机构等特征。并对其演化规律、形成机制与成矿作用的关系,作了初步探讨。 相似文献
85.
Pavlova viridis sp. nov. is described on the basis of light and electron microscope observations. The material was collected from the coast
of haiyang county of Shandong, China. It is characterized by 1) yellowish green to green chloroplast, 2) rudimentary short
flagellum 0.3 μm long and hook-shaped, 3) long flagellum with small spherical knob-scales, 4) absence of pyrenoid and stigma,
and 5) marine habitat. This new species andP. salina seem to be most closely related to each other but their colour, the insertion of their three appendages, the shape of their
knob scales, and their cell periplasts are quite different from one another.
Contribution No. 1879 from the Institute of Oceanology, Academia Sinica 相似文献
86.
资源环境领域的信息化与本土化 总被引:2,自引:2,他引:0
陈述彭 《地球信息科学学报》2001,3(2):37-40
本文重点论述了资源环境领域的深层研究问题;同时提出用信息化推动现代化的观点,进而对地球信息科学与数字地球的战略进行了概要地分析。 相似文献
87.
INTRODUCTIONTheSubeiShoalandtheChangjiangRiverestuarineareainthewestoftheHuanghaiandEastChinaSeasisoneofthemarginalseasintheworld ,wheresuspendedmatterisextremelyhigh .Here ,notonlyistheretheTaiwanWarmCurrentoneoftheKuroshio’sbranchesintheEastChinaSea,butalsotheHuanghaiCoastalCurrent,andChangjiangDilutedWater.Sothestrongmixingbetweenthecoastalandoffshorewaterscomplicatessuspendedmatterdistributioninthisarea.HowthesuspendedmatterdischargedfromtheChangjiangRiverandtheabandonedHuan… 相似文献
88.
FUZZY COMPREHENSIVE EVALUATION OF CONTAINER TRANSPORTATION MODES ALONG THE CHANGJIANG RIVER MAIN LINE AND ITS DELTA AREA 总被引:1,自引:0,他引:1
ZHANGShi-yu XIAOHan-liang 《中国地理科学(英文版)》2003,13(3):259-261
The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in Chi-na. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifi-cally in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line. 相似文献
89.
WANGWei-wu ZHULi-zhong WANGRen-chao SHIYong-jung 《中国地理科学(英文版)》2003,13(1):39-47
Urban heat environmental quality(UHEQ) is affected by the interacting of weather condition and underlying surface framework of urban area .In the last two decades,many researchers from domestic and overseas have studied many problems at the aspect of urban heat environment such as urban heat islands ,urban air temperature and their rela-tion with urban land cover,city population,air pollution etc,In the recent years,Hangzhou,acting as a center city of Zhejiang Province in China,its urbanization quantum and quantity have both changed greatly,in particular ,representing as business affairs building,resident real property and all kins of specialty market having arisen in built-up zone,Based on Landsat TM images data in 1991 and 1999,urban underlying surface temperature value and Normalized Difference Vegetation Index (NDVI) were calculated using image interpreting and supervised classification technique by remote sensing software ERDAS image 8.4,The relation model between urban underlying surface temperature (UUST )and urban air temperature was setup according to the certain correlation patten .Reference to the relational standard of assessing human comfort and other meteorology data of Hangzhou City in summer,the spatial distribution characteristic and the spatial varia-tion degree of human comfort of heat environmental quality are estimated and mapped on a middle scale,that is ,in six districts of Hangzhou City .Then the paper reveals the main characteristic of spatial variation from 1991 to 1999.Lastly,the change mechanism is analyzed and discussed from the viewpoint of city planning,construction and environmental protec-tion. 相似文献
90.
This paper is a continuation of previous research, which obtained a convenient solution for arbitrary surface fluxes before ponding. By means of Fourier Transformation this has been extended to derive analytical solutions of a linearized Richards' equation for arbitrary input fluxes after surface saturation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献