全文获取类型
收费全文 | 60916篇 |
免费 | 1247篇 |
国内免费 | 1834篇 |
专业分类
测绘学 | 2329篇 |
大气科学 | 4744篇 |
地球物理 | 12083篇 |
地质学 | 24762篇 |
海洋学 | 4344篇 |
天文学 | 9738篇 |
综合类 | 2359篇 |
自然地理 | 3638篇 |
出版年
2022年 | 273篇 |
2021年 | 450篇 |
2020年 | 432篇 |
2019年 | 489篇 |
2018年 | 5526篇 |
2017年 | 4774篇 |
2016年 | 3534篇 |
2015年 | 939篇 |
2014年 | 1114篇 |
2013年 | 1915篇 |
2012年 | 2290篇 |
2011年 | 4381篇 |
2010年 | 3493篇 |
2009年 | 4219篇 |
2008年 | 3496篇 |
2007年 | 4006篇 |
2006年 | 1767篇 |
2005年 | 1429篇 |
2004年 | 1550篇 |
2003年 | 1432篇 |
2002年 | 1250篇 |
2001年 | 908篇 |
2000年 | 884篇 |
1999年 | 691篇 |
1998年 | 748篇 |
1997年 | 700篇 |
1996年 | 577篇 |
1995年 | 566篇 |
1994年 | 486篇 |
1993年 | 422篇 |
1992年 | 420篇 |
1991年 | 386篇 |
1990年 | 466篇 |
1989年 | 378篇 |
1988年 | 356篇 |
1987年 | 445篇 |
1986年 | 348篇 |
1985年 | 438篇 |
1984年 | 543篇 |
1983年 | 456篇 |
1982年 | 460篇 |
1981年 | 427篇 |
1980年 | 445篇 |
1979年 | 367篇 |
1978年 | 349篇 |
1977年 | 343篇 |
1976年 | 322篇 |
1975年 | 299篇 |
1974年 | 313篇 |
1973年 | 344篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
211.
212.
213.
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
214.
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
215.
216.
Infiltration experiments have been performed at three sites along a well-known catena under virgin tropical rain forest using a portable sprinkling infiltrometer. Experimentally determined infiltration curves are presented. Infiltration curves are also simulated on the basis of the Mein-Larson equation. The parameters for this model have been obtained from the infiltration curves (saturated conductivity) and simple soil moisture determinations (fillable porosity). The agreement between experimentally determined and modelled infiltration is reasonable, provided (a) saturated conductivity as derived from the experimental data is corrected, (b) a storage parameter, also derived from the experimental data, is added to the Mein-Larson model, and (c) the decline in soil porosity with depth is either small or occurs abruptly at shallow depth. Comparison of observed infiltration rates with rainfall intensity shows that Horton Overland Flow has to occur naturally at least on the middle and lower section of the catena. Despite the fact that most parameters can be estimated in principle from basic soil data, it remains advisable to obtain sprinkling infiltrometer field measurements, because of soil variability due to dynamic surface conditions, macroporosity, air entrapment, and irregularity of the wetting front. 相似文献
217.
218.
219.
INTRODUCTIONTheSubeiShoalandtheChangjiangRiverestuarineareainthewestoftheHuanghaiandEastChinaSeasisoneofthemarginalseasintheworld ,wheresuspendedmatterisextremelyhigh .Here ,notonlyistheretheTaiwanWarmCurrentoneoftheKuroshio’sbranchesintheEastChinaSea,butalsotheHuanghaiCoastalCurrent,andChangjiangDilutedWater.Sothestrongmixingbetweenthecoastalandoffshorewaterscomplicatessuspendedmatterdistributioninthisarea.HowthesuspendedmatterdischargedfromtheChangjiangRiverandtheabandonedHuan… 相似文献
220.
B. R. Johnson M. E. Abroe P. Ade J. Bock J. Borrill J. S. Collins P. Ferreira S. Hanany A. H. Jaffe T. Jones A. T. Lee L. Levinson T. Matsumura B. Rabii T. Renbarger P. L. Richards G. F. Smoot R. Stompor H. T. Tran C. D. Winant 《New Astronomy Reviews》2003,47(11-12):1067
We discuss MAXIPOL, a bolometric balloon-borne experiment designed to measure the E-mode polarization anisotropy of the cosmic microwave background radiation (CMB) on angular scales of 10′ to 2°. MAXIPOL is the first CMB experiment to collect data with a polarimeter that utilizes a rotating half-wave plate and fixed wire-grid polarizer. We present the instrument design, elaborate on the polarimeter strategy and show the instrument performance during flight with some time domain data. Our primary dataset was collected during a 26 h turnaround flight that was launched from the National Scientific Ballooning Facility in Ft. Sumner, New Mexico in May 2003. During this flight five regions of the sky were mapped. Data analysis is in progress. 相似文献