全文获取类型
收费全文 | 38704篇 |
免费 | 3245篇 |
国内免费 | 4876篇 |
专业分类
测绘学 | 2765篇 |
大气科学 | 4906篇 |
地球物理 | 8311篇 |
地质学 | 19299篇 |
海洋学 | 3153篇 |
天文学 | 2227篇 |
综合类 | 3443篇 |
自然地理 | 2721篇 |
出版年
2024年 | 146篇 |
2023年 | 440篇 |
2022年 | 823篇 |
2021年 | 1025篇 |
2020年 | 802篇 |
2019年 | 888篇 |
2018年 | 5464篇 |
2017年 | 4706篇 |
2016年 | 3397篇 |
2015年 | 1022篇 |
2014年 | 1053篇 |
2013年 | 947篇 |
2012年 | 1826篇 |
2011年 | 3556篇 |
2010年 | 2856篇 |
2009年 | 3134篇 |
2008年 | 2579篇 |
2007年 | 2984篇 |
2006年 | 664篇 |
2005年 | 759篇 |
2004年 | 804篇 |
2003年 | 784篇 |
2002年 | 683篇 |
2001年 | 498篇 |
2000年 | 482篇 |
1999年 | 601篇 |
1998年 | 531篇 |
1997年 | 475篇 |
1996年 | 462篇 |
1995年 | 355篇 |
1994年 | 351篇 |
1993年 | 319篇 |
1992年 | 276篇 |
1991年 | 224篇 |
1990年 | 182篇 |
1989年 | 156篇 |
1988年 | 137篇 |
1987年 | 64篇 |
1986年 | 77篇 |
1985年 | 46篇 |
1984年 | 38篇 |
1983年 | 21篇 |
1982年 | 40篇 |
1981年 | 35篇 |
1980年 | 42篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 11篇 |
1958年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
I.IN~crIOXLocatedinthecoddlepatofTallmBasin,withanareaof33.76X104klnZ,theTaldirnakan~isinthehinterlandofEurasia.Blockedbythehighmountainsaround,vapourofoceancanhardlyreachthedesert.APartfromthis,asthedeSertisinthesinkingcompensationareaoftheascensionalaircurrentaamstheQinghal-XIZangPlateau,itSprecipitationisrareandtheevaporationcapacityisintensealltheyearround.Allthesecontributetotheformationsofthetypifydrydesertclimate.Theacidityindexofthedesertandthearoundregionisashighasmorethan50,w… 相似文献
52.
MAO Duan-qian ZHANG Jie BAO Hao-sheng 《中国地理科学(英文版)》2005,15(3):275-280
1IN T R O D U C T IO NAn image isa setofbelief,s ideasand impressionsthatapersonholdsaboutan object(KOTLER,1991).Similar-lydefinitionistheimage of a destinationas thesum ofbelief,sideasand impressionsthatpeoplehave ofa placeor destination(CROMPTON,1979;KO… 相似文献
53.
Four bromophenols were isolated from the extract of marine red alga,Rhodomela confervoides by column chromatography and HPLC methods. By means of spectroscopic methods inclding IR, MS, 1D, and 2D-NMR techniques,
their structures were elucidated as (1) 3-bromo-4,5-dihydroxy benzoic acid methyl ester; (2) bis (2,3-dibromo-4,5-dihydroxybenzyl)
ether; (3) 3,4-dibromo-5-(methoxymethyl)-1,2-benzenediol and (4) 3-bromo-4,5-dihydroxy-benzaldehyde. Compound 1 was first
isolated from the algae in nature, and 1, 4 were found to have selective cytotoxic activities against KB, Bel 7402 and A549
cells, 2 showed powerful antibacterial activities againstStaphylococcus aurens andPseudomonas aeruginosa.
Supported by National “863” Program (No. 2004AA625030, 2001AA620503), Quingdao marine sciences project (No. 04-2-NN-26) and
Key Knowledge Innovative Project of the Chinese Academy of Sciences (KZCX3-SW-215). 相似文献
54.
EFFECT OF SULPHATE-REDUCING BACTERIA ON ELECTRO-CHEMICAL CORROSION BEHAVIOR OF 16Mn STEEL IN SEA MUD
INTRODUCTIONItwasgenerallyconsideredpreviouslythatthecorrosionofsteelinseamudwasnotserious.However,itwaslaterfoundthatthecorrosionrateofsteelinsomeseamudwashigherthanthatinseawater(King,1980;Sehmide,1982;Guoetal.,1997;Hou,1998).Therearesomereportsthatthecorrosionr… 相似文献
55.
This study on the distribution features of petroleum hydrocarbon in water and sedi-ment off the Fujian shore using data obtained from the baseline research on oceanic contamination in Fujian showed that:during the research preiod,petroleum hydrocarbon concentrations in water varied from 5.77μg/L to 37.28μg/L,averaged 14.48 μg/L;was lower in the wet seasson than in the dry season;and was highest in the Minjiang Estuary and Jiulong Estuary in both seasons ,The petorleum hydrocarbon concentrations in shore sediment varied from 14.48 mg/kg to 784.36 mg/kg,averaged 133.3 mg/kg ,and was closely related to sediment types (granularity). 相似文献
56.
Is Precipitation the Dominant Controlling Factor of High Inorganic Nitrogen Content in the Changjiang River and Its Mouth? 总被引:1,自引:1,他引:0
沈志良 《中国海洋湖沼学报》2003,21(4):368-376
The main reasons for the high content of inorganic N and its increase by several times in the Changjiang River and its mouth during the last 40 years were analysed in this work. The inorganic N in precipitation in the Changjiang River catchment mainly comes from gaseous loss of fertilizer N, N resulting from the increases of population and livestock, and from high temperature combustions of fossil fuels. N from precipitation is the first N source in the Changjiang River water and the only direct cause of high content of inorganic N in the Changjiang River and its mouth. The lost N in gaseous form and from agriculture non-point sources fertilizer comprised about 60% of annual consumption of fertilizer N in the Changjiang River catchment and were key factors controlling the high content of inorganic N in the Changjiang River mouth. The fate of the N in precipitation and other N sources in the Changjiang River catchment are also discussed in this paper. 相似文献
57.
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
58.
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
59.
60.
INTRODUCTIONTheSubeiShoalandtheChangjiangRiverestuarineareainthewestoftheHuanghaiandEastChinaSeasisoneofthemarginalseasintheworld ,wheresuspendedmatterisextremelyhigh .Here ,notonlyistheretheTaiwanWarmCurrentoneoftheKuroshio’sbranchesintheEastChinaSea,butalsotheHuanghaiCoastalCurrent,andChangjiangDilutedWater.Sothestrongmixingbetweenthecoastalandoffshorewaterscomplicatessuspendedmatterdistributioninthisarea.HowthesuspendedmatterdischargedfromtheChangjiangRiverandtheabandonedHuan… 相似文献