全文获取类型
收费全文 | 25278篇 |
免费 | 3749篇 |
国内免费 | 5437篇 |
专业分类
测绘学 | 2169篇 |
大气科学 | 3779篇 |
地球物理 | 5246篇 |
地质学 | 12811篇 |
海洋学 | 3927篇 |
天文学 | 2183篇 |
综合类 | 1730篇 |
自然地理 | 2619篇 |
出版年
2024年 | 115篇 |
2023年 | 362篇 |
2022年 | 1104篇 |
2021年 | 1368篇 |
2020年 | 1200篇 |
2019年 | 1346篇 |
2018年 | 1548篇 |
2017年 | 1490篇 |
2016年 | 1500篇 |
2015年 | 1295篇 |
2014年 | 1476篇 |
2013年 | 1709篇 |
2012年 | 1732篇 |
2011年 | 1826篇 |
2010年 | 1724篇 |
2009年 | 1606篇 |
2008年 | 1618篇 |
2007年 | 1529篇 |
2006年 | 1385篇 |
2005年 | 932篇 |
2004年 | 739篇 |
2003年 | 749篇 |
2002年 | 836篇 |
2001年 | 781篇 |
2000年 | 636篇 |
1999年 | 554篇 |
1998年 | 414篇 |
1997年 | 416篇 |
1996年 | 340篇 |
1995年 | 334篇 |
1994年 | 282篇 |
1993年 | 240篇 |
1992年 | 199篇 |
1991年 | 142篇 |
1990年 | 118篇 |
1989年 | 127篇 |
1988年 | 97篇 |
1987年 | 68篇 |
1986年 | 67篇 |
1985年 | 49篇 |
1984年 | 45篇 |
1983年 | 41篇 |
1982年 | 41篇 |
1981年 | 30篇 |
1980年 | 26篇 |
1979年 | 34篇 |
1978年 | 20篇 |
1976年 | 17篇 |
1975年 | 22篇 |
1973年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Microbial degradation technologies have been developed to restore ground water quality in aquifers polluted by organic contaminants effectively in recent years. However, in course of the degradation, the formation of biofilms in ground water remediation technology can be detrimental to the effectiveness of a ground water remediation project. Several alternatives are available to a remedial design engineer, such as Permeable Reactive Barriers (PRBs) and in -situ bioremediation, Hydrogen Releasing Compounds (HRCs) barrier, Oxygen Releasing Compounds (ORCs) barrier etc. which are efficient and cost- effective technologies. Excessive biomass formation renders a barrier ineffective in degrading the contaminants, Efforts are made to develop kinetics models which accurately determine bio - fouling and bio - filn formation and to control excessive biomass formation. 相似文献
3.
自从在活动星系核NGC4945的视线方向上发现第一个河外H2O超脉泽源以来,迄今为止已发现了19个河外H2O超脉泽源,对与活动星系核成协和河外H2O超脉泽源及分子谱线的观测和研究是探测和研究活动星系核核区中央源,拱核气体和尘埃环性质的非常有效的工具,主要评述对河外H2O超脉泽源及与其相关分子谱线的搜索,观测和理论研究现状。 相似文献
4.
私营企业主是我们社会主义市场经济的建设者 ,是否“合法”是我们正确解读私营企业主的关键。我国目前的私营企业主分为两类三种。合法经营的私营企业主中的优秀分子是吸收入党的主要对象 相似文献
5.
ZHANGPing-yu MAYan-ji YUZhen-han 《中国地理科学(英文版)》2002,12(4):315-320
Manzhouli is the largest land port city on the Sino-Russia border, transit cargo through the land port amount-ed to 5.95 million tons, transit tourists were 304 500 in 2000. It stands at the joint place of China, Mongolia and Russi-a, faces to Siberia area of Russia, receives direct support from the Northeast China and Bohai Sea Rim Area, and possess-es priorities in geographical location, land port infrastructure, water resources, coal resources, tourist resources andgreat potentiality in economic cooperation with Russia. The future urban function is a key port on the First Eurasia Continen-tal Bridge. Manzhouli Port will keep its first place between China and Russia land transport, and it is forecasted that thetransit amount through Manzhouli Port will go up to 10 million tons in 2005 and 20 million tons in 2010. It will be construct-ed to be a trade center of the peripheral area extending to Russia and Mongolia, a key export-oriented processing industri-al zone supported by industries such as export processing industries, export agriculture, trade services, technology trad-ing and the other service industries. It keeps being a well-known touring city for trade, shopping, sightseeing, vocation,local food, recreation and cultural events. To build Manzhouli Export Processing Industry Zone will improve city econom-ic structure, and the main sectors are organic food processing, livestock products processing, garment and furniture indus-try. Moreover, Manzhouli Export Processing Industry Zone will eventually be upgraded to be a border free trade zone.The city functional transition will inevitably affect urban spatial restructure and its expansion. The city space transforma-tion will develop as such: one development axis of No. 301 highway paralleling with Bin - Zhou(Harbin - Manzhouli) rail-way which cuts through central part of Manzhouli City, and links Zhalainuocr District with central city; three urban unitsincluding central city, Zhalainuocr District and Manzhouli Interchange Trade Zone; cohesion with Aoerjin and Cuogangpastures; regional dual-nuclei structure of Hailaer City and Manhzouli City; and the Manzhouli-Zabaykalsk Free TradeZone. 相似文献
6.
Grid method is employed for sampling covering soil at the test field,which is reclamation area filled by coal mining wastes for cropland in the Fushun coal mine,Liaoning Province,the Northeast China.The soil samples are taken at different locations,including three kinds of covering soil,three different depths of soil layers and four different covering ages of covering soil.The spatial-temporal variation of heavy metal element content in reclamation soil is stud-ied.The results indicate that the content of heavy metal elements is decreasing year after year,the determinant reason why the content of heavy metal elements at 60cm depth layer is higher than that at 30cm depth layer and surface is fertiliz-er and manure application;the metal elements mainly come from external environment;there is no metal pollution coming from mother material (coal mining wastes)in plough layer of covering soil. 相似文献
7.
高速滑坡问题是当前工程地质和环境地质学界极为关注的问题。本文对诸如滑体高速滑动所对应的时空界限、滑体滑动过程所产生的热效应以及空气浮托力等高速滑坡产生机制问题进行了初步探讨。 相似文献
8.
A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems, one EA type and two EB type eclipsing binaries (one of them could be a W UMa system), and seven pulsating stars including three candidates of δScuti stars. 相似文献
9.
10.
ENVIRONMENTAL SUSTAINABILITY AND SCENARIOS OF URBANIZATION IN ARID AREA——A Case Study in Wuwei City of Gansu Province 总被引:1,自引:0,他引:1
YOUFei LIYu DONGSuo-cheng 《中国地理科学(英文版)》2005,15(2):120-130
1IN T R O D U C T IO N The western China isfacinggrowing problems of eco- logicaland economic development. The disparitiebse- tween the socio-economy of the western and eastern China were enlarging, and the major ecologicalprob- lems stilelvolve as past(H… 相似文献