全文获取类型
收费全文 | 1795篇 |
免费 | 258篇 |
国内免费 | 235篇 |
专业分类
测绘学 | 81篇 |
大气科学 | 79篇 |
地球物理 | 406篇 |
地质学 | 1280篇 |
海洋学 | 176篇 |
天文学 | 22篇 |
综合类 | 98篇 |
自然地理 | 146篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 37篇 |
2021年 | 18篇 |
2020年 | 45篇 |
2019年 | 43篇 |
2018年 | 29篇 |
2017年 | 74篇 |
2016年 | 77篇 |
2015年 | 59篇 |
2014年 | 135篇 |
2013年 | 100篇 |
2012年 | 84篇 |
2011年 | 146篇 |
2010年 | 118篇 |
2009年 | 127篇 |
2008年 | 104篇 |
2007年 | 116篇 |
2006年 | 108篇 |
2005年 | 92篇 |
2004年 | 105篇 |
2003年 | 85篇 |
2002年 | 82篇 |
2001年 | 53篇 |
2000年 | 65篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 43篇 |
1996年 | 47篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 24篇 |
1992年 | 28篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 6篇 |
1988年 | 12篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 13篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2288条查询结果,搜索用时 31 毫秒
991.
992.
通过对储层物性数据资料的分析和整理,研究了孔南地区上石盒子组碎屑岩储集层特征及其控制因素。结果表明:研究区上石盒子组碎屑岩储层为低孔低渗储层,渗透率与孔隙度呈正相关性。储层孔隙的连通性好,属于孔隙型储层。孔隙类型以次生粒间溶孔为特征。晚成岩期,岩屑、填隙物、长石颗粒以及高岭石发生溶蚀,产生了大量的次生孔隙,改善了储层物性。沉积条件、压实作用、胶结作用和溶蚀作用是控制储层性质的主要因素。 相似文献
993.
运用对比分析法,以控煤构造样式为主线,系统总结了吉林省南部和北部煤田构造特征的异同。南部地区以挤压型构造为主,发育逆冲断裂组合为代表的挤压型控煤构造样式组合,煤田构造变形复杂,煤系赋存范围较小;北部地区则以伸展型构造为特征,控煤构造样式以断裂断块组合为主,煤系分布范围相对较大。吉林省南、北煤田构造特征的上述差异与其所处的大地构造位置和所经历的构造演化历程有关。 相似文献
994.
鄂西渝东区建南气田及周缘志留系为一套海相致密碎屑岩沉积.沉积厚度1 000~1 450m,为南方海相地层的重要油气勘探层系之一.据对该区志留系砂岩储层野外露头剖面和岩心的观察以及薄片分析,志留系砂岩主要岩石类型为富石英的长石石英砂岩和岩屑石英砂岩,粒度以极细粒为主,少部分为细粒,成分成熟度和结构成熟度较高.储层类型主要... 相似文献
995.
996.
997.
T.K. Al-Ameri 《Marine and Petroleum Geology》2011,28(4):880-894
This work presents new insights of the generation, quality and migration pathways of the hydrocarbons in the East Baghdad Oil Field.The Khasib and Tannuma formations in East Baghdad are considered as oil reservoirs according to their high porosity (15-23%) and permeability (20-45 mD) in carbonate rocks. The hydrocarbons are trapped by structural anticline closure trending NW-SE. Gas chromatography analysis on these oil reservoirshave shown biomarkers of abundant ranges of n-alkanes of less than C22 (C17-C21) with C19 and C18 peaks. This suggests mainly liquid oil constituents of paraffinic hydrocarbons from marine algal source of restricted palaeoenvironments in the reservoir. The low non aromatic C15 + peaks are indicative for slight degradation and water washing. Oil biomarkers of Pr./Ph. = 0.85, C31/C30 < 1.0, location in triangle of C27-C29 sterane, C28/C29 of 0.6 sterane, Oleanane of 0.01 and CPI = 1.0, indicate an anoxic marine environment with carbonate deposits of Upper Jurassic to Early Cretaceous age. Four Miospores, seven Dinoflagellates and one Tasmanite species confirm affinity to the upper most Jurassic to Lower Cretaceous Chia Gara and Ratawi Formations.The recorded palynomorphs from the Khasib and Tannuma Formations are of light brown color of TAI = 2.8-3.0 and comparable to the mature palynomorphs that belong to the Chia Gara and the Lower part of Ratawi Formations.The Chia Gara Formation generated oil during Upper Cretaceous to Early Palaeogene and accumulated in structural traps of Cretaceous age, such as the Khasib and Tannuma reservoirs. The Chia Gara Formation generated and expelled high quantities of oil hydrocarbons according to their TOC wt% of 0.5-8.5 with S2 = 2.5-18.5 mg Hc/g Rock, high hydrogen index of the range 150-450 mg Hc/g Rock, good petroleum potential of 4.5-23.5 mg Hc/g Rock, mature (TAI = 2.8-3.0 and Tmax = 428-443C), kerogen type II and palynofacies parameters of up to 100% AOM (Amorphous Organic Matters). This includes algae deposits in a dysoxic-anoxic to suboxic-anoxic environment.Alternative plays are discussed according to the migration pathways. 相似文献
998.
This paper describes and analyzes the application of the precautionary principle in the regulation of operational discharges from offshore petroleum activities. Norway implemented a zero discharge policy in line with international agreements. However, companies are obliged to follow considerably stricter requirements in the Barents Sea compared to other parts of the Norwegian Continental Shelf. This paper follows the development of the zero discharge measure and analyzes what it implies for activities in the Barents Sea. Several “uncertainties of precaution” are discussed, which relate to technological issues, monitoring, compliance and unintended environmental consequences. Precautionary action should be scrutinized for its proportionality: how do the benefits of the measure relate to the technological, financial and environmental costs? It is concluded that the most (cost-) effective solutions that could lead to the lowest total environmental harm are not always the solutions that are most politically feasible. 相似文献
999.
1000.
It has been long believed there should be some relations between traffic system and urbanization,but the in-teraction between them,especially on the regional level,has been not in consideration due to the difficulty in quantitative analysis.Based on the development of Jilin Province during 1981-2003,the paper analyzed the relation with the grey-relation model which was adjusted to fit specific problem,and came to some conclusions.Firstly,there exists ob-vious and strong correlation between traffic system and urbanization.Secondly,urbanization responds to the develop-ment of traffic system mainly on the level of urbanization,such as population and developed area,however,less on urbanization quality.Thirdly,traffic system influences urbanization as a whole except for several peculiar factors,which means we should optimize the whole traffic system to promote urbanization.Based on those conclusions,the paper illustrated the mechanism of traffic system,promoting urbanization scale and urbanization quality. 相似文献