全文获取类型
收费全文 | 7449篇 |
免费 | 1920篇 |
国内免费 | 3664篇 |
专业分类
测绘学 | 53篇 |
大气科学 | 842篇 |
地球物理 | 1641篇 |
地质学 | 8441篇 |
海洋学 | 909篇 |
天文学 | 118篇 |
综合类 | 394篇 |
自然地理 | 635篇 |
出版年
2024年 | 49篇 |
2023年 | 145篇 |
2022年 | 304篇 |
2021年 | 329篇 |
2020年 | 373篇 |
2019年 | 463篇 |
2018年 | 417篇 |
2017年 | 402篇 |
2016年 | 444篇 |
2015年 | 474篇 |
2014年 | 537篇 |
2013年 | 538篇 |
2012年 | 588篇 |
2011年 | 562篇 |
2010年 | 488篇 |
2009年 | 642篇 |
2008年 | 519篇 |
2007年 | 601篇 |
2006年 | 581篇 |
2005年 | 475篇 |
2004年 | 477篇 |
2003年 | 447篇 |
2002年 | 399篇 |
2001年 | 345篇 |
2000年 | 358篇 |
1999年 | 349篇 |
1998年 | 289篇 |
1997年 | 255篇 |
1996年 | 239篇 |
1995年 | 188篇 |
1994年 | 180篇 |
1993年 | 155篇 |
1992年 | 112篇 |
1991年 | 64篇 |
1990年 | 71篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 28篇 |
1986年 | 13篇 |
1985年 | 15篇 |
1984年 | 11篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1979年 | 5篇 |
1954年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
Based on the high temperature data of June to August in 1961-2000 in North China, the high temperature weather processes are investigated, and a more complete data set for severe high temperature processes is created. The climatic characteristics of adverse high temperature weather in Beijing, Tianjin, Shijiazhuang, Jinan and Taiyuan are analyzed respectively. The major features of the East-Asia Subtropical High and Transformed Continental High are discussed. The outcomes indicate that the influence of both East Asia Subtropical High and Transformed Continental High on these weather events varies, by a larger margin, from one city to another over North China and they are also closely related to the relative humidity. It is found that the behaviours of East-Asia Subtropical High and Transformed Continental High are the major important systems that give rise to the summer high temperature weather over the region. Based on these findings, the 5-day, 10-day and monthly assessment models for such high impact events have been developed. The assessment outcomes prove to be useful in assessing severe high-temperature events in major cities of North China. 相似文献
142.
Christine S McCulloch 《Area》2006,38(1):24-33
Public participation in transparent decisionmaking has been proposed as a panacea for environmental protection. Bargaining theory suggests drawbacks to transparency such as hardening of attitudes and intransigence. Yet achievement of consensus on environmental values for integrated water resource management demands public involvement. Historical study of attempts to prevent reservoir construction in upland valleys designated for protection of nature suggests that 'closed-door' bargaining proved more effective for environmentalists than open, public debate. Records now open for analysis of disputes over Teesdale and Farndale, 1950–1970, allow comparisons to be made between behind-the-scenes deliberations and 'open-door' public discussion. The ambition of progressing from public participation to devolution of environmental decisionmaking and responsibility to the local scale demands more conceptualization of the process of decisionmaking on water resource development. 相似文献
143.
144.
Brian Murton 《New Zealand geographer》2006,62(1):25-38
Abstract: This paper examines how the cultural politics of resource management were played out on the North Kaipara beach between about 1900 and 1971 between Māori and the representative of the Crown, the Marine Department. Particular attention is devoted to how, after regulations were introduced to protect toheroa, the giant surf clam, Māori struggled to assert their rights through a range of transgressions. The paper argues that this illustrates how cultural politics works both from the top down (the Marine Department's implementation of policy) and the bottom up (Māori resistance). It concludes that through an examination of this particular 'culture war', the foreshore emerges as a contested domain where politics, culture and epistemology are inseparable. 相似文献
145.
146.
Fred J. Anderson 《Environmental Geology》2006,49(7):1034-1042
Several unfavorable environmental and engineering geologic conditions exist in Fargo, North Dakota. Dominantly, the behavior
of smectitic clays within the proglacial Lake Agassiz sediments of the Sherack and Brenna Formations creates subsoil instability
beneath engineered structures in the Fargo area and slope instability within cutbank meanders of the Red River of the North.
Unfavorable engineering geologic conditions encountered include: the elastic deformation of clayey glaciolacustrine soils,
shrink-swell properties, inadequate bearing capacities, and mass movements. These conditions are responsible for structural
failures including the Fargo Grain Elevator in 1955 and the Northern Pacific railroad grade. Bank failures along the Red River
are common due to the inherent instability of Brenna Formation smectitic clays which are subject to plastic deformation in
the subsurface, with resultant block failure of overlying Sherack Formation. Recent alluvial sediments due to typical fluvial
action and the continued seasonal saturation of cutbank meanders within the floodplain also add to soil instability. 相似文献
147.
根据影响沙漠、沙质荒漠化土地的地质地貌、植被、气候和人类活动等特征,通过确定地域分异、发生学、多级序列等区划原则,建立了以地质地貌类型组合、气候为沙漠、沙质荒漠化土地区(Ⅰ级区)划分和以沙质荒漠化土地类型空间分布特征为沙漠、沙质荒漠化土地亚区(Ⅱ级区)划分的指标体系。采用遥感方法,将中国北方沙漠、沙质荒漠化土地划分为贺兰山以西干旱沙漠、沙质荒漠化区;贺兰山-大兴安岭干旱、半干旱沙漠、沙质荒漠化区和大兴安岭以东半干旱、半湿润沙质荒漠化区等3个区和17个亚区。并对沙漠、沙质荒漠化土地区进行了现状分析。 相似文献
148.
邢台矿区山字型构造的发现及其地质意义 总被引:1,自引:0,他引:1
邢台山字型构造位于河北省邯邢煤田内,其前弧向ES突出,脊柱呈ES-WN走向。分别分析了山字型构造脊柱及其东、西翼反射弧构造形迹特征,对研究区找矿具有重要意义。 相似文献
149.
A. M. Larin E. B. Sal’nikova A. B. Kotov L. B. Makar’ev S. Z. Yakovleva V. P. Kovach 《Stratigraphy and Geological Correlation》2006,14(5):463-474
Early Proterozoic granitoids are of a limited occurrence in the Baikal fold area being confined here exclusively to an arcuate belt delineating the outer contour of Baikalides, where rocks of the Early Precambrian basement are exposed. Geochronological and geochemical study of the Kevakta granite massif and Nichatka complex showed that their origin was related with different stages of geological evolution of the Baikal fold area that progressed in diverse geodynamic environments. The Nichatka complex of syncollision granites was emplaced 1908 ± 5 Ma ago, when the Aldan-Olekma microplate collided with the Nechera terrane. Granites of the Kevakta massif (1846 ± 8 Ma) belong to the South Siberian postcollision magmatic belt that developed since ~1.9 Ga during successive accretion of microplates, continental blocks and island arcs to the Siberian craton. In age and other characteristics, these granites sharply differ from granitoids of the Chuya complex they have been formerly attributed to. Accordingly, it is suggested to divide the former association of granitoids into the Chuya complex proper of diorite-granodiorite association ~2.02 Ga old (Neymark et al., 1998) with geochemical characteristics of island-arc granitoids and the Chuya-Kodar complex of postcollision S-type granitoids 1.85 Ga old. The Early Proterozoic evolution of the Baikal fold area and junction zone with Aldan shield lasted about 170 m.y. that is comparable with development periods of analogous structures in other regions of the world. 相似文献
150.
Structural controls on Tertiary orogenic gold mineralization during initiation of a mountain belt, New Zealand 总被引:3,自引:2,他引:3
Two types of structurally controlled hydrothermal mineralization have occurred during folding of fissile schist in southern New Zealand: fold-related mineralization and normal fault-related mineralization. Both types have the same mineralogy and textures, and are dominated by quartz–ankerite veins and silicified breccias with ankeritic alteration. Most mineralized zones are thin (centimetre scale), although host schist is commonly impregnated with ankerite up to 20 m away. Thick (up to 5 m wide) mineralized zones are generally gold-bearing and contain pyrite and arsenopyrite with stibnite pods locally. Some of these auriferous zones have been extensively mined historically despite rugged topography and difficult access. Mineralization occurred during regional tectonic compression in the initial stages of development of the Southern Alps mountain belt at the Pacific–Australian plate boundary in the Miocene. Most of the gold-bearing deposits occur in east to south-east, striking normal faults that cut across mesoscopic folds in a belt that coincides with the southern termination of a regional-scale north trending antiform. Mineralized zones have similar structural control and relative timing to a nearby swarm of Miocene lamprophyre dykes and carbonatites. Limited stable isotopic data (C and O) and trace element geochemistry suggest that there was probably no genetic link between the igneous activity and gold mineralization. However, these two types of fluid flow have been controlled by the same tectonically created crustal plumbing system. This Miocene hydrothermal activity and gold deposition demonstrates that orogenic (mesothermal) mineralization can occur during the inception of an orogenic belt, not just in the latter stages as is commonly believed. These Miocene structures have been preserved in the orogen because the locus of uplift has moved northwards, so the early-formed gold deposits have not yet been structurally overprinted or eroded. 相似文献