全文获取类型
收费全文 | 917篇 |
免费 | 98篇 |
国内免费 | 125篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 42篇 |
地球物理 | 101篇 |
地质学 | 173篇 |
海洋学 | 619篇 |
天文学 | 1篇 |
综合类 | 52篇 |
自然地理 | 135篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 19篇 |
2020年 | 21篇 |
2019年 | 39篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 24篇 |
2015年 | 33篇 |
2014年 | 35篇 |
2013年 | 47篇 |
2012年 | 36篇 |
2011年 | 42篇 |
2010年 | 38篇 |
2009年 | 47篇 |
2008年 | 49篇 |
2007年 | 49篇 |
2006年 | 51篇 |
2005年 | 38篇 |
2004年 | 55篇 |
2003年 | 39篇 |
2002年 | 34篇 |
2001年 | 30篇 |
2000年 | 31篇 |
1999年 | 33篇 |
1998年 | 33篇 |
1997年 | 20篇 |
1996年 | 8篇 |
1995年 | 23篇 |
1994年 | 16篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 19篇 |
1983年 | 29篇 |
1982年 | 32篇 |
1981年 | 36篇 |
1980年 | 1篇 |
排序方式: 共有1140条查询结果,搜索用时 31 毫秒
101.
历年影响广西沿海的热带气旋及其灾害成因分析 总被引:1,自引:0,他引:1
通过对1950-2012年影响广西沿海的热带气旋的统计分析发现,影响广西沿海的热带气旋数量年际变化明显,最多的年份达9个,最少的年份为0个;热带气旋季节分布具有明显规律性,每年的7、8、9三个月为影响高峰月,其次为6、10月;热带气旋从菲律宾以东洋面进入南海后穿过海南省和雷州半岛再次登陆广西沿海的次数最多,该类热带气旋引起的风暴增水平均值为111.2 cm,到达非登陆台风增水的2.6倍。风暴潮灾害的形成与强台风天气系统、全日大潮、河流下泄洪水直接有关。强台风产生巨浪及降雨,使入海河口水位上升,与风暴潮叠加后产生明显的增水,造成巨大的潮灾。 相似文献
102.
An account is given of a Geologists’ Association meeting in the Isle of Purbeck held on 28th–30th September 2012 and the stratigraphy and structures of the rocks examined during the weekend are described. Uppermost Jurassic Stage nomenclature and recent changes to stratigraphical nomenclature in the uppermost part of the Kimmeridge Clay Formation are discussed and the conclusion reached that the long-established divisions (Members) of this Formation are both readily recognisable and have nomenclatorial priority. The recent change to the position of Pallasioides-Rotunda zonal boundary ignores the ammonite fauna and is inappropriate. For the Lulworth district the stratigraphy of the uppermost Jurassic (Portlandian) through Lower and Upper Cretaceous formations are described and their associated structures discussed. The coastal evolution of the Lulworth coast is briefly discussed. 相似文献
103.
为探究江苏中部沿海双凸型剖面演变特性,在江苏盐城川东港南侧潮间带布设了10个水准观测站,2012年9月至2013年11月对该潮滩剖面演变过程开展了现场观测.结果表明:该潮滩剖面呈现出双凸型特征,平均高、低潮位线附近的滩涂形成淤积率较高的地形凸点;潮间上带受潮流影响小,滩面高程相对稳定;平均高、低潮位之间的区域滩面高程季节性变化明显,总体呈现冲刷状态;潮间下带冲刷显著,滩面坡度增大.全剖面自岸向海呈现"稳定—淤积—稳定—淤积—冲刷"的双凸型剖面特征. 相似文献
104.
Lapo Ragionieri Stefano Cannicci Christoph D. Schubart Sara Fratini 《Estuarine, Coastal and Shelf Science》2010
Most marine organisms are characterized by at least one planktonic phase during their life history, potentially allowing interconnection of populations separated by several hundred kilometers. For many years, the idea that marine species are genetically homogenous throughout their range of distribution, due to passive larval transport, has been a paradigm. Nowadays, a growing number of studies underline the existence of boundaries in the marine realm and highlight how larval dispersal is a complex process depending on biotic as well as abiotic factors. Marine fragmented habitats, such as atolls, mangroves and estuaries, are optimal systems for investigating the marine dispersion process under a metapopulation approach, since populations can be geographically defined a priori as opposed to those occupying open marine environments. Within this frame, the present paper investigates the population genetic structure and the demographic history of the mangrove crab Neosarmatium meinerti within the western Indian Ocean by partial sequences of the mitochondrial DNA cytochrome oxidase subunit I. A total of 167 specimens were sampled from six mangrove sites distributed along the East African coast, from Kenya to South Africa, also including a mangrove forest located on Mahé Island, Seychelles. A sharp genetic break between the mainland and the Seychelles is recorded, revealing the existence of two historically distinct groups that can be defined as independent evolutionary units. Gene flow along the East African coast appears to be high enough to form a single metapopulation, probably by means of stepping stone populations. Otherwise, this mainland metapopulation is currently under expansion through a gradual moving front from the subtropical toward the equatorial populations. 相似文献
105.
INTRODUCTIONThemonsoonhasacirculationfeaturethatisplanetaryinscaleandanidentifiablesignalregardingitssubsequentintensitysomeninemonthspriortotheactivestageofthesummermonsoon(WebsterandYang,1992).Furthermore,themagnitudeofthemonsoonvariabilityissubstantia… 相似文献
106.
China's eastern coastal area marine hazards (storm surge, erosion and deposition by tidal currents and seawater intrusion)
and the history, present situation, experiences and problems of inhabitants in their fight against marine hazards are discussed
in this paper, which also suggests counter-measures against, and scientific and rational management of, coastal area marine
hazards in order to protect the coastal and estuarine ecosystems. 相似文献
107.
沙质海岸强浪作用下沿岸输沙问题研究 总被引:1,自引:0,他引:1
在沙质海岸上修建导流堤、丁坝等会引起局部海域水沙动力条件的改变和海床冲淤调整,因此准确预测沿岸输沙率是海岸工程建设前进行优化设计的基础条件之一.首先构建了刻画高强度推移质输沙过程中固-液混合体运动的理论模型,通过寻求模型的特解并推导成1D沿岸输沙率公式.该公式适宜计算强浪作用下的推移质输沙率,已得到了大型波浪水槽、往复流水道和海滩现场实测输沙率资料的良好验证.通过与物理模型试验实测输沙量结果的比较,进一步表明该公式能够较好地预测沙质海岸在寒潮大风浪(或台风浪)作用下的高强度输沙量(骤淤量). 相似文献
108.
采用实时荧光定量PCR法,在对白斑综合症多发的虾蟹混养塘内三疣梭子蟹体内病毒含量进行定量跟踪检测的基础上,结合电子显微镜及病理切片,对室内经口服、注射两种回感模式处理已感染白斑综合症病毒的濒死三疣梭子蟹体内病毒含量进行实验验证,并观察其体内主要器官组织的病理改变。结果表明,受白斑综合症病毒感染的三疣梭子蟹存活与死亡取决于蟹体内病毒含量,当病毒含量≥109拷贝/ml时均进入濒死或死亡阶段,其主要器官组织均有明显的病理改变。 相似文献
109.
110.
Andrei A. Andreev William F. Manley
lafur Inglfsson Steve L. Forman 《Global and Planetary Change》2001,31(1-4)
New pollen and radiocarbon data from an 8.6-m coastal section, Cape Shpindler (69°43′N; 62°48′E), Yugorski Peninsula, document the latest Pleistocene and Holocene environmental history of this low Arctic region. Twelve AMS 14C dates indicate that the deposits accumulated since about 13,000 until 2000 radiocarbon years BP. A thermokarst lake formed ca. 13,000–12,800 years BP, when scarce arctic tundra vegetation dominated the area. By 12,500 years BP, a shallow lake existed at the site, and Arctic tundra with Poaceae, Cyperaceae, Salix, Saxifraga, and Artemisia dominated nearby vegetation. Climate was colder than today. Betula nana became dominant during the Early Preboreal period about 9500 years BP, responding to a warm event, which was one of the warmest during the Holocene. Decline in B. nana and Salix after 9500 years BP reflects a brief event of Preboreal cooling. A subsequent increase in Betula and Alnus fruticosa pollen percentages reflects amelioration of environmental conditions at the end of Preboreal period (ca. 9300 years BP). A decline in arboreal taxa later, with a dramatic increase in herb taxa, reflects a short cold event at about 9200 years BP. The pollen data reflect a northward movement of tree birch, peaking at the middle Boreal period, around 8500 years BP. Open Betula forest existed on the Kara Sea coast of the Yugorski Peninsula during the Atlantic period (8000–4500 years BP), indicating that climate was significantly warmer than today. Deteriorating climate around the Atlantic–Subboreal boundary (ca. 4500 years BP) is recorded by a decline in Betula percentages. Sedimentation slowed at the site, and processes of denudation and/or soil formation started at the beginning of the Subatlantic period, when vegetation cover on Yugorski Peninsula shifted to near-modern assemblages. 相似文献