全文获取类型
收费全文 | 1189篇 |
免费 | 205篇 |
国内免费 | 345篇 |
专业分类
测绘学 | 114篇 |
大气科学 | 86篇 |
地球物理 | 194篇 |
地质学 | 938篇 |
海洋学 | 136篇 |
天文学 | 5篇 |
综合类 | 99篇 |
自然地理 | 167篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 29篇 |
2021年 | 41篇 |
2020年 | 41篇 |
2019年 | 56篇 |
2018年 | 43篇 |
2017年 | 59篇 |
2016年 | 46篇 |
2015年 | 74篇 |
2014年 | 73篇 |
2013年 | 89篇 |
2012年 | 92篇 |
2011年 | 85篇 |
2010年 | 87篇 |
2009年 | 93篇 |
2008年 | 81篇 |
2007年 | 81篇 |
2006年 | 83篇 |
2005年 | 73篇 |
2004年 | 68篇 |
2003年 | 62篇 |
2002年 | 48篇 |
2001年 | 54篇 |
2000年 | 40篇 |
1999年 | 46篇 |
1998年 | 25篇 |
1997年 | 34篇 |
1996年 | 22篇 |
1995年 | 22篇 |
1994年 | 19篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 12篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1739条查询结果,搜索用时 15 毫秒
991.
992.
在云南保山-腾冲高速公路建设中,遇到了与膨胀性硅藻土相关的边坡稳定问题。通过对云南腾冲五合乡、芒棒乡、团田乡多个地质剖面现场调查和室内物质成分、微观结构分析、力学性质测试表明,云南腾冲新近纪芒棒组硅藻土是一种富含膨胀性黏土矿物的黏土质硅藻土,在性状上属于膨胀性极软岩。天然硅藻土具有很强的结构性,导致其物理性质与力学性质的关系与传统岩土力学规律极不相符,如孔隙比高达2.20~2.78、液性指数为0.66~2.73的天然硅藻土单轴抗压强度竟高达1.09~2.11 MPa。综合研究表明,云南保山-腾冲高速公路建设中黏土质硅藻土边坡的滑坡灾害、风化剥落灾害与其工程特性密切相关。 相似文献
993.
<正>Exploration practices show that the Jurassic System in the hinterland region of the Junggar Basin has a low degree of exploration but huge potential,however the oil/gas accumulation rule is very complicated,and it is difficult to predict hydrocarbon-bearing properties.The research indicates that the oil and gas is controlled by structure facies belt and sedimentary system distribution macroscopically,and hydrocarbon-bearing properties of sand bodies are controlled by lithofacies and petrophysical facies microscopically.Controlled by ancient and current tectonic frameworks,most of the discovered oil and gas are distributed in the delta front sedimentary system of a palaeo-tectonic belt and an ancient slope belt.Subaqueous branch channels and estuary dams mainly with medium and fine sandstone are the main reservoirs and oil production layers,and sand bodies of high porosity and high permeability have good hydrocarbon-bearing properties;the facies controlling effect shows a reservoir controlling geologic model of relatively high porosity and permeability.The hydrocarbon distribution is also controlled by relatively low potential energy at the high points of local structure macroscopically, while most of the successful wells are distributed at the high points of local structure,and the hydrocarbon-bearing property is good at the place of relatively low potential energy;the hydrocarbon distribution is in close connection with faults,and the reservoirs near the fault in the region of relatively low pressure have good oil and gas shows;the distribution of lithologic reservoirs at the depression slope is controlled by the distribution of sand bodies at positions of relatively high porosity and permeability.The formation of the reservoir of the Jurassic in the Junggar Basin shows characteristics of favorable facies and low-potential coupling control,and among the currently discovered reservoirs and industrial hydrocarbon production wells,more than 90%are developed within the scope of faciespotential index FPI0.5,while the FPI and oil saturation of the discovered reservoir and unascertained traps have relatively good linear correlation.By establishing the relation model between hydrocarbonbearing properties of traps and FPI,totally 43 favorable targets are predicted in four main target series of strata and mainly distributed in the Badaowan Formation and the Sangonghe Formation,and the most favorable targets include the north and east of the Shinan Sag,the middle and south of the Mobei Uplift,Cai-35 well area of the Cainan Oilfield,and North-74 well area of the Zhangbei fault-fold zone. 相似文献
994.
以过硫酸钾为引发剂,通过水溶液聚合法制得了丙烯酸和丙烯酰胺的聚合物A。用聚合物A作为有机改性剂,采用混炼挤压法制备得到样品。用X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)等方法对其结构形貌进行研究。结果表明,其晶面间距由原来的1.269 nm增大到1.322 nm,有机基团进入层间,并且仍保持层状结构,成功制备出了有机改性膨润土。用有机改性膨润土配制钻井液,当其质量分数为4%时,浆液的粘度为5.5 mPa.s,滤失量为13 mL,润滑系数为0.13。与普通钠基膨润土钻井液相比,有机改性膨润土钻井液的滤失量和润滑系数均有较大幅度降低,并且改善了钻井液的流变性。 相似文献
995.
房产测量是一种法定测绘,主要为房屋各项管理工作提供服务。房产测绘预算面积与实测面积可能存在面积不一致,通过房产测绘成果质量、分摊方案、政策等方面进行分析,探讨其原因及解决方法。 相似文献
996.
With the aid of geophysical measurements, including seventeen two-dimensional(2 D) seismic lines and the well logging curves of well FGY1, the structure and reservoir characteristics of the Upper Ordovician–Lower Silurian strata in the Fenggang block, northern Guizhou Province, were analyzed thoroughly to identify desert areas and favorable intervals. The results show that Longmaxi-Wufeng is the most prospect-rich formation, consisting of a thick succession of overmature black shale, this formation remaining partially in the Suiyang, Fenggang and Jianchaxi synclines. The Longmaxi-Wufeng shale, especially the lower member, was deposited in a reducing low-energy environment with relatively high U content and a low Th/U value. In this shale, the organic matter type(sapropelic and humic-sapropelic), total organic carbon(TOC) content, gas content, gas adsorption capacity, vitrinite reflectance and brittle mineral content are profitable for shale gas preservation and development. The fractures of this shale were closed because of its high overburden pressure. The gas adsorption capacity of this shale increases with increasing TOC content and Ro. In the Longmaxi-Wufeng Formation at well FGY1, the most favorable intervals are in the depth ranges of 2312.4–2325.1 m and 2325.8–2331.1 m. 相似文献
997.
998.
999.
1000.
基于贵州地区煤层气富集成藏条件,结合统计资料和实验测试数据成果.从含气性、储层物性及成藏规律三个方面探讨了贵州中、西部地区煤层气藏特征。结果表明:贵州中、西部地区2000m以浅煤层气资源量约31511亿m^3,资源丰度高,一般〉2亿m^3/km^2,最高可达7.15亿m^3/km^2,主要集中分布在六盘水煤田、织纳煤田及黔北煤田煤,且以富甲烷(〉8m^3/t)为主,500m以深范围内煤层气CH4含量〉80%;不同地区不同煤层的孔裂隙发育、渗透性、吸附能力、解析能力、储层压力及储层压力系数等差别较大,地域、层域差异明显,煤储层原地应力较高,原地应力梯度普遍〉1.5MPa/100m;区内煤系地层“广覆式”生烃.沉积构造史控制着气田的分布,并以大型向斜或复向斜为煤层气富集主要场所。 相似文献