全文获取类型
收费全文 | 10639篇 |
免费 | 1969篇 |
国内免费 | 2864篇 |
专业分类
测绘学 | 960篇 |
大气科学 | 2266篇 |
地球物理 | 2492篇 |
地质学 | 5531篇 |
海洋学 | 1410篇 |
天文学 | 346篇 |
综合类 | 979篇 |
自然地理 | 1488篇 |
出版年
2024年 | 35篇 |
2023年 | 141篇 |
2022年 | 413篇 |
2021年 | 537篇 |
2020年 | 362篇 |
2019年 | 520篇 |
2018年 | 589篇 |
2017年 | 518篇 |
2016年 | 611篇 |
2015年 | 543篇 |
2014年 | 614篇 |
2013年 | 631篇 |
2012年 | 695篇 |
2011年 | 744篇 |
2010年 | 715篇 |
2009年 | 661篇 |
2008年 | 570篇 |
2007年 | 651篇 |
2006年 | 548篇 |
2005年 | 522篇 |
2004年 | 436篇 |
2003年 | 363篇 |
2002年 | 528篇 |
2001年 | 443篇 |
2000年 | 420篇 |
1999年 | 449篇 |
1998年 | 281篇 |
1997年 | 294篇 |
1996年 | 246篇 |
1995年 | 260篇 |
1994年 | 213篇 |
1993年 | 211篇 |
1992年 | 149篇 |
1991年 | 119篇 |
1990年 | 91篇 |
1989年 | 71篇 |
1988年 | 66篇 |
1987年 | 55篇 |
1986年 | 32篇 |
1985年 | 22篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 20篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1958年 | 15篇 |
1947年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 739 毫秒
961.
962.
1997年4-6月云南省地震局对滇西南重点监视区做了短临预报,但这期间未发生所预期的地震。而滇西南地区6级地震的背景和省内的前兆异常变化是明显的。为此,认为前兆异常是区域应力场增强的结果。异常与地震是相互伴生的兄弟关系,不是父子间因果关系,是造成地震虚报的主要原因。 相似文献
963.
在发现类星体的方法中,最有效的4 种方法是:颜色方法,无缝光谱方法,射电方法和X射线方法。覆盖的波段为:射电波段,光学波段和X 射线波段。我们将4 种方法联合在一起,应用于4 个UKSchmidt 天区。其目的是尽量减少选择效应,建立更完备的类星体巡天样本。本工作从1002 天区入手。已完成了X 射线选和部分光学选的分光观测工作。发现了一颗B= 15 .0 的亮类星体和一个Seyfert 对,其强X 射线辐射,是迄今首次观测到的。 相似文献
964.
Nans Addor Hong X. Do Camila Alvarez-Garreton Gemma Coxon Keirnan Fowler Pablo A. Mendoza 《水文科学杂志》2020,65(5):712-725
ABSTRACTLarge-sample hydrology (LSH) relies on data from large sets (tens to thousands) of catchments to go beyond individual case studies and derive robust conclusions on hydrological processes and models. Numerous LSH datasets have recently been released, covering a wide range of regions and relying on increasingly diverse data sources to characterize catchment behaviour. These datasets offer novel opportunities, yet they are also limited by their lack of comparability, uncertainty estimates and characterization of human impacts. This article (i) underscores the key role of LSH datasets in hydrological studies, (ii) provides a review of currently available LSH datasets, (iii) highlights current limitations of LSH datasets and (iv) proposes guidelines and coordinated actions to overcome these limitations. These guidelines and actions aim to standardize and automatize the creation of LSH datasets worldwide, and to enhance the reproducibility and comparability of hydrological studies. 相似文献
965.
利用地面常规观测、NCEP/NCAR0.25°×0.25°再分析及风廓线雷达等资料,诊断分析了2018年10月17—18日乌鲁木齐极端暴雪天气过程的锋面特征。结果表明:在欧洲高压脊衰退,中亚长波槽分段东移的背景下,天山北坡强烈锋生并持续近30小时,此次锋生是热力和动力共同作用的,天山附近锋面呈带状准垂直分布,动力锋生激发的次级环流使垂直运动维持发展,为大暴雪提供动力条件; 400~600 hPa西南和地面~850 hpa西北路径输送的水汽,在600~800 hPa强烈辐合,为乌鲁木齐暴雪提供充沛水汽。风廓线雷达监测资料水平风向风速的垂直变化、Cn2能够反映锋生和水汽的演变特征,也从观测事实上证实了锋面对动力抬升及水汽辐合的重要作用。 相似文献
966.
砬子山岩体出露于华北地台抚顺—清原古隆起带与吉黑地槽的相接部位。砬子山岩体是由石英闪长岩、似斑状石英二长岩、二长花岗岩和碱长花岗岩构成的杂岩体。4个岩性不同的侵入体构成连续的中-酸性钙碱岩石序列。岩体的地质特征、地球化学特征表明4个侵入体是同源岩浆不同演化阶段的产物。岩浆的演化机制为深部岩浆分异作用,岩浆则是来源于下部地壳。 相似文献
967.
Chen Hong-Fei Xu Wen-Yao Chen Geng-Xiong Hong Ming-Hua Peng Feng-Lin 《Solar physics》2001,204(1-2):339-349
In this paper geomagnetic disturbances at middle and low latitudes are discussed by using geomagnetic data of the magnetic
storm of 15–16 July 2000. This storm is a response to the solar Bastille Day flare on 14 July. Generally, the geomagnetic
disturbances at middle and low latitudes during a storm are mainly caused by three magnetospheric–ionospheric current systems,
such as the ring current system (RC), the partial ring current and its associated region II field-aligned currents (PR), and
the region I field-aligned currents (FA). Our results show that: (1) The northward turning of IMF-Bz started the sudden commencement of the storm, and its southward turning caused the main phase of the storm. (2) The PR- and
FA-currents varied violently in the main phase. In general, the field of the FA-current was stronger than that of the PR-current.
(3) In the first stage of the recovery phase, the RC-field gradually turned anti-parallel to the geomagnetic axis from a 15°
deviation, and the local time (Λ) pointed by the RC-field stayed at 16:00. After that, Λ rotated with the stations, and the
RC-field was not anti-parallel to the geomagnetic axis, but 5°–10° deviated. These facts suggest that the warped tailward
part of the ring current decays faster than the symmetric ring current. 相似文献
968.
Horizontal and vertical distribution of PCBs and chlorinated pesticides in sediments from Masan Bay,Korea 总被引:1,自引:0,他引:1
Horizontal and vertical distributions of organochlorine compounds (OCs) were determined in sediments from Masan Bay. The concentrations of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethanes (DDTs), HCB, hexachlorocyclohexanes (HCHs) and chlordane related compounds (CHLs) in sediments were in the range of 1.24-41.4, 0.28-89.2, 0.02-0.59, nd-1.03, and nd-2.56 ng/g, respectively. The spatial distribution of OCs showed a negative gradient from the inner of the bay to outer part of the bay, indicating that the source of OCs was probably located inside the bay. Compositional pattern of PCB congeners showed a relatively high concentration of high-chlorinated congeners in the inner part of the bay and a relatively low concentration of low-chlorinated congeners in the outer part. In sediment core from Masan Bay maximum concentrations of PCBs and DDTs are observed in the subsurface samples and correspond to an age of early 1980s and late 1960s. The concentration profiles of PCBs and DDTs in sediments of Masan Bay appear to correspond to use of PCBs and DDTs in Korea. 相似文献
969.
Sea ice thickness measurement and its underside morphology analysis using radar penetration in the Arctic Ocean 总被引:5,自引:0,他引:5
Sea ice, as an important component of the Arctic climate system, has drawn significant sci-entific interest. Sea ice thickness and its morphology have dramatic impacts on ocean-atmos- phere-ice interactions[1—4], which directly affect the exchange proces… 相似文献
970.
Sea surface height and transport stream function of the South China Sea from a variable-grid global ocean circulation model 总被引:8,自引:0,他引:8
The study on the South China Sea (SCS) circulation has a history of more than 40 years. Nevertheless, the SCS circulation is not fully understood compared with the Bohai Sea, Yellow Sea and East China Sea (ECS). Many numerical studies on the SCS circulati… 相似文献