全文获取类型
收费全文 | 29306篇 |
免费 | 1131篇 |
国内免费 | 1944篇 |
专业分类
测绘学 | 1589篇 |
大气科学 | 3103篇 |
地球物理 | 5930篇 |
地质学 | 13995篇 |
海洋学 | 1436篇 |
天文学 | 1963篇 |
综合类 | 2556篇 |
自然地理 | 1809篇 |
出版年
2024年 | 33篇 |
2023年 | 103篇 |
2022年 | 238篇 |
2021年 | 289篇 |
2020年 | 232篇 |
2019年 | 254篇 |
2018年 | 4980篇 |
2017年 | 4250篇 |
2016年 | 2837篇 |
2015年 | 491篇 |
2014年 | 413篇 |
2013年 | 329篇 |
2012年 | 1274篇 |
2011年 | 2986篇 |
2010年 | 2282篇 |
2009年 | 2577篇 |
2008年 | 2115篇 |
2007年 | 2578篇 |
2006年 | 236篇 |
2005年 | 375篇 |
2004年 | 534篇 |
2003年 | 518篇 |
2002年 | 373篇 |
2001年 | 175篇 |
2000年 | 215篇 |
1999年 | 255篇 |
1998年 | 204篇 |
1997年 | 188篇 |
1996年 | 177篇 |
1995年 | 158篇 |
1994年 | 110篇 |
1993年 | 128篇 |
1992年 | 81篇 |
1991年 | 63篇 |
1990年 | 30篇 |
1989年 | 56篇 |
1988年 | 45篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 29篇 |
1980年 | 28篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1976年 | 8篇 |
1969年 | 3篇 |
1958年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
ZHANGJin MAZongjin RENWenjun LEIYongliang 《大地构造与成矿学(英文版)》2003,27(1):165-178
There are many thrust-related structures occurring in the Paleozoic strata of the Niushou Mountain in the central part of Ningxia Hui Autonomous Region. The fault-related folds are the typical structures in this area. Based on the analysis about these structures and their relationships, the processes by which these structures of the Miboshan Formation were formed are reconstructed, and the strata underwent about three stages of deformation: (1) horizontal shortening, (2) folding, and (3) thrusting. And the fact that the Niushou Mountain is the leading edge of an old thrust sheet was proved, the Niushou Mountain, the Daluo Mountain and the Xiaoluo Mountain together constitute the front part of this old thrust zone, so the Niushou Mountain and the Ordovician strata in the central and southern parts of Ningxia now are likely allochthons. In the period from middle Ordovician to Devonian, the areas of the central and southern Ningxia belonged to the back-arc foreland basin of North Qilianshan orogen, which was adjacent to the continent in the north. In the later part of the early Paleozoic period, the Niushou Mountain was formed after the closure of the back-arc foreland basin. 相似文献
53.
54.
中强地震前山东地下流体地震前兆模糊分维特征研究 总被引:6,自引:0,他引:6
采用模糊集理论与分形理论相结合的模糊分维方法,计算山东地下流体在1983年菏泽5.9级地震和1995年苍山5.2级地震前的变化。分析结果认为,模糊分维值反映了地震前兆时序观测资料的结构变化特征,具有一定的物理意义,为从复杂的地下流体前兆观测值中提取地震异常信息提供了新的方法,但对某些台、测项而言、必须具体分析其模糊分维变化特征及其震前异常变化特征。 相似文献
55.
56.
DYNAMIC VARIATIONS OF WATER QUALITY IN TAIHU LAKE AND MULTIVARIATE ANALYSIS OF ITS INFLUENTIAL FACTORS 总被引:1,自引:0,他引:1
Cai Qiming Gao Xiyun Chen Yuwei Ma Shengwei Nanjing Institute of Geography Limnology CAS Nanjing People''s Republic of ChinaMartin Dokulil Institute of Limnology Austria 《地理学报(英文版)》1997,(3)
LakeTaihuisalargeshallowlakeinChina,whichpalysanimportantroleinwater-quantityregulation,watersupply,cultivationetc.Withrapiddevelopmentofagricultureandindustryinthearea,alargenumberofpollutantshavebeendischargedintothelake,leadingtoanincreaseinnutrients… 相似文献
57.
Application of discovery process models in estimating petroleum resources at the play level in China
Discovery process modeling has gained wide acceptance in the Chinese exploration community. In recent years, a variety of
discovery process models have been applied to the prediction of undiscovered petroleum resources at the play level in sedimentary
basins in China. However, challenging problems have been encountered, particularly when one method alone has been applied
to small plays in nonmarine sedimentary basins or in plays with an unusual order of discovery wells. This paper presents results
gotten by using the lognormal discovery process model of the Geological Survey of Canada and the geoanchored method for three
petroleum plays in basins with different geologic settings. Although the predicted shapes of the parentsize distributions
which use these two models, were not always similar, the expected values of the total resources and the number of fields (pools)
to be discovered are comparable. The combined use of two discovery process models in the same play compensates for the weaknesses
in one method compared with the other and vice versa. Thus, more reliable estimates are the result. 相似文献
58.
着重介绍了CuInSe2的结构和光、电学特性;讨论了多各上薄膜沉积技术;评价了主要的合成装置及其作途;综述了制备CuInSe2太阳电池器件的工艺和材料,提出了一种能成功地生产大面积太阳电池薄膜的经济有铲的沉积技术。 相似文献
59.
丰城洛市地区推,滑覆构造特征及其成因探讨 总被引:2,自引:0,他引:2
介绍了洛市地区推、滑覆构造特征、运动学标志及其形成时期、成因模式。 相似文献
60.
In this paper,the Gutenberg-Richter model is used to generate seismic events.The events that satisfy the random distribution are also generated.With those events,the natural probability distribution of Load and Unload Response Ratio(LURR),which measures quantitatively the degree of instability of a nonlinear system,is discussed.The study is based on stress energy release,which is chosen as the response of nonlinear system F3.The comparative results from the observation catalogue and generating data are also studied.It is revealed that the natural probability of LURR is mostly stable when the sample number is sufficient.The lower the natural probability of LURR,the more the precursory is information it may contain.The influence of Y3 resulting from the sample number and the magnitude range of events is also discussed. 相似文献