全文获取类型
收费全文 | 3166篇 |
免费 | 147篇 |
国内免费 | 277篇 |
专业分类
测绘学 | 206篇 |
大气科学 | 37篇 |
地球物理 | 472篇 |
地质学 | 594篇 |
海洋学 | 188篇 |
天文学 | 3篇 |
综合类 | 93篇 |
自然地理 | 1997篇 |
出版年
2024年 | 1篇 |
2023年 | 29篇 |
2022年 | 125篇 |
2021年 | 110篇 |
2020年 | 136篇 |
2019年 | 138篇 |
2018年 | 137篇 |
2017年 | 158篇 |
2016年 | 135篇 |
2015年 | 115篇 |
2014年 | 151篇 |
2013年 | 285篇 |
2012年 | 245篇 |
2011年 | 144篇 |
2010年 | 112篇 |
2009年 | 132篇 |
2008年 | 132篇 |
2007年 | 159篇 |
2006年 | 145篇 |
2005年 | 140篇 |
2004年 | 122篇 |
2003年 | 95篇 |
2002年 | 86篇 |
2001年 | 53篇 |
2000年 | 75篇 |
1999年 | 66篇 |
1998年 | 55篇 |
1997年 | 38篇 |
1996年 | 38篇 |
1995年 | 32篇 |
1994年 | 33篇 |
1993年 | 23篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 3篇 |
1981年 | 1篇 |
排序方式: 共有3590条查询结果,搜索用时 15 毫秒
1.
INTRODUCTIONTriploidanimalsareusefulbecausetheyaresterile ,characterizedbypositivegrowthinthere productiveseason ,usefulfortesting ,forintroductionofnon nativespecies ,andforprotectionofde velopedstrains.Theinductionoftriploidyhadbeenreportedinmanyaquaculturespecies .Triploidshavebeensuccessfullyinducedinshrimpusingtemperatureshockorchemicalshock (CB ,6 DMAP)in 4species :Sicyoniaingentis (Xiangetal.,1 991 ) ,Fenneropenaeuschinensis (Xiangetal.,1 992 ;Daietal.,1 993;Baoetal.,1 993;Li… 相似文献
2.
Erica Schoenberger 《The Professional geographer》1991,43(2):180-189
The open-ended corporate interview as a qualitative research method is proposed as a valuable component of an evidentiary strategy in economic geography. It is argued to be more sensitive than other survey methods to historical, institutional, and strategic complexity. The corporate interview method is particularly appropriate in periods of economic and social change that challenge traditional analytical categories and theoretical principles. Some problems inherent to the method, and strategies for minimizing their impact on the research project, are described. 相似文献
3.
4.
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
5.
Variables related to urban park awareness are identified and methods for relaxing assumptions of perfect information in park use models are discussed. Park awareness is related to park characteristics (age and degree of development of the park), population characteristics (race, age, length of residence, recreation participation), and distance. Park attributes are stronger predictors of both park awareness and use than is distance. These findings parallel similar research on the cognitive aspects of shopping decisions. 相似文献
6.
Based on our detailed structural characterization, we examine possible relationships between thrust faults and strike-slip faults and thrust-cored folds and depositional units in the Silla Syncline, a 4 km wide fold composed of fine-grained mudstone, coarse sandstone and conglomerate deposits of the Cerro Toro Formation in the Magallanes foreland basin, Chilean Patagonia. The syncline is bounded on its western flank by an asymmetric anticline and on its eastern flank by a broad zone of thrust faults and associated folds, which are oriented sub-parallel to the syncline axis. Deposition of the coarse-grained units of the Silla Syncline appears to have taken place in this structurally defined trough controlled primarily by thrust fault related growth structures flanking the syncline.The syncline and surrounding area have also been deformed by two sets of strike-slip faults, one right-lateral and one left-lateral. The strike-slip and thrust faulting operated contemporaneously for much of their active periods, although it appears that thrust faulting, confined within the fine-grained units, initiated slightly earlier than strike-slip faulting. In addition, younger igneous intrusions at high angle to bedding generally localize along the strike-slip faults. The cross-cutting relationships among the intrusions, strike-slip faults, and flexural slip faults show that all these structures were active during the same period, which extends beyond mid-Miocene.These conclusions support the premise that structures in deep-water sediments are important for understanding not only the deformation of a foreland basin, but also its depositional architecture. 相似文献
7.
Federico Caprotti 《Geoforum》2008,39(2):942-957
This paper investigates the Italian fascist regime’s use of internal colonisation as part of a wider ruralisation policy aimed at promoting population growth, curbing rural-urban migration, staunching emigration, and halting the spread of industrial urbanisation. By focusing on the case study of the Pontine Marshes, the paper demonstrates how, through targeted selection procedures aimed at displacing defined social and political undesirables, migrants were chosen and effectively coerced into migrating to the “fascist” landscape of the marshes. The area, reclaimed and developed in the 1930s, was celebrated as a sign of the regime’s engineering and social success. The paper utilises Antonio Gramsci’s thought on hegemony, and argues that the overt use of coercion hints at the fact that fascism, although ideologically totalitarian and hegemonic, was contested. Although statisticians, demographers and state bureaucrats were organised and institutionalised in the construction of hegemony based on consent, fascism based itself more in coercion than in passive consent in the case of internal colonisation. 相似文献
8.
9.
10.
Full-rangenonlinearanalysisoffatiguebehaviorsofreinforcedconcretestructuresbyfiniteelementmethod¥SongYupu;ZhaoShunbo;WangRuim... 相似文献