全文获取类型
收费全文 | 678篇 |
免费 | 141篇 |
国内免费 | 142篇 |
专业分类
测绘学 | 65篇 |
大气科学 | 62篇 |
地球物理 | 189篇 |
地质学 | 351篇 |
海洋学 | 142篇 |
天文学 | 72篇 |
综合类 | 24篇 |
自然地理 | 56篇 |
出版年
2024年 | 5篇 |
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 24篇 |
2020年 | 25篇 |
2019年 | 40篇 |
2018年 | 28篇 |
2017年 | 39篇 |
2016年 | 41篇 |
2015年 | 27篇 |
2014年 | 51篇 |
2013年 | 47篇 |
2012年 | 43篇 |
2011年 | 56篇 |
2010年 | 41篇 |
2009年 | 51篇 |
2008年 | 24篇 |
2007年 | 37篇 |
2006年 | 55篇 |
2005年 | 54篇 |
2004年 | 41篇 |
2003年 | 32篇 |
2002年 | 22篇 |
2001年 | 24篇 |
2000年 | 16篇 |
1999年 | 24篇 |
1998年 | 21篇 |
1997年 | 12篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有961条查询结果,搜索用时 15 毫秒
231.
软土深层搅拌桩的水泥土抗腐蚀性室内试验 总被引:10,自引:0,他引:10
结合深港西部通道填海区深层搅拌桩在滨海地下水环境中施工的需要,对水泥土在自来水、地下水、海水及Na2SO4溶液环境下的抗腐蚀性进行了室内研究,研究表明以纯水泥为固化剂的水泥土在腐蚀性地下水环境中的抗腐蚀性能较差,增加矿渣、粉煤灰的含量,能增强水泥土抗腐蚀性;分析了固化剂中矿渣、粉煤灰掺入量对水泥土抗压强度及抗腐蚀性的影响规律,即固化剂掺入比不变的情况下,用矿渣、粉煤灰替代部分水泥能大幅度提高水泥土的抗压强度,同时改善其抗腐蚀性;得出了抗腐蚀性能良好的水泥土配方,即矿渣、粉煤灰的质量占固化剂的40%~60%,可供同类工程借鉴. 相似文献
232.
朱国平 《中国地质灾害与防治学报》2005,16(B12):71-76
针对我国地质灾害发生量大面广的特点,介绍了岩土锚固技术在地灾防治工程施工中的应用技术措施,分析了地灾防治工程施工中遇到的特殊地质环境条件。在对复杂地层进行分析分类的基础上,分析了工程措施对造成地层复杂的影响因素,提出了克服复杂地层钻孔施工难度大应采取的施工工艺方法和技术措施,介绍了选择施工设备及机具的一般原则,对地灾防治工程施工具有一定的指导意义。 相似文献
233.
Acceleration of buoyancy-driven fractures and magmatic dikes beneath the free surface 总被引:3,自引:0,他引:3
By performing buoyancy-driven fracture experiments in brittle gelatin we observe that the ascent velocity of a fracture containing a finite volume of fluid increases when approaching the free surface. We theoretically describe this free-surface effect and quantify it by introducing an effective depth-dependent fracture toughness and developing an ascent model on the basis of linear fracture mechanics. We develop a successful inversion approach and resolve the actual and critical fracture length and the ascent velocity far away from the free surface from the observation of the fracture tip migration alone. Other parameters, as the fluid volume included in the fracture and the in situ fracture toughness, can be derived. Applying the model and inversion to the 1998 eruption at Piton de la Fournaise, Reunion Island, reveals estimates of the length and critical length of the feeding magma batch, the magma batch volume and the in situ fracture toughness. It further indicates that the ascent velocity of the magma batch was probably much smaller at greater depths and that the batch might have been initiated several months or years before the eruption. 相似文献
234.
Bujang B. K. Huat Faisal Hj. Ali F. H. Choong 《Geotechnical and Geological Engineering》2006,24(6):1527-1544
Residual soils occur in most countries of the world but those that occur in greater area and depth are usually found in the
tropical humid areas. This research examines the effects of loading rate of applied or net mean stress on the volume change
behavior of an unsaturated granitic residual soil. Three loading rates were adopted: fast, slow and extra slow loading rate.
It was observed that the loading rate of applied or net mean stress has a pronounced effect on the void ratio and degree of
saturation but has an insignificant effect on the water content of residual soils subjected to constant matric suction. 相似文献
235.
236.
由国家地震局地球物理研究所承担的“MTS-100T伺服试验机改造”课题,对震源物理实验室进行了实验系统改造。该文简要介绍了该课题所完成的主要工作及其应用情况,包括:MTS-100T伺服试验机控制系统、16通道高速数据采集系统、激光散斑图干涉仪。 相似文献
237.
The use of laboratory experiments for the study of conservative solute transport in heterogeneous porous media 总被引:4,自引:1,他引:3
Laboratory experiments on heterogeneous porous media (otherwise known as intermediate scale experiments, or ISEs) have been
increasingly relied upon by hydrogeologists for the study of saturated and unsaturated groundwater systems. Among the many
ongoing applications of ISEs is the study of fluid flow and the transport of conservative solutes in correlated permeability
fields. Recent advances in ISE design have provided the capability of creating correlated permeability fields in the laboratory.
This capability is important in the application of ISEs for the assessment of recent stochastic theories. In addition, pressure-transducer
technology and visualization methods have provided the potential for ISEs to be used in characterizing the spatial distributions
of both hydraulic head and local water velocity within correlated permeability fields. Finally, various methods are available
for characterizing temporal variations in the spatial distribution (and, thereby, the spatial moments) of solute concentrations
within ISEs. It is concluded, therefore, that recent developments in experimental techniques have provided an opportunity
to use ISEs as important tools in the continuing study of fluid flow and the transport of conservative solutes in heterogeneous,
saturated porous media.
Received, December 1996 · Revised, July 1997 · Accepted, August 1997 相似文献
238.
239.
与野外BRDF实验相比,室内实验更容易控制,具有无风、无云、光源固定和可全方位重复观测等优点,获取的反射率数据和测量的植被结构数据的精度要较野外测量的高,可用于BRDF模型验证及反演试验。 相似文献
240.
装备保障地理信息系统的设计与实现 总被引:2,自引:0,他引:2
在适应未来联合作战需要的基础上,分析了装备保障GIS在做好军事准备中的意义和影响,介绍了构建装备保障GIS的途径和方法,包括系统需求分析、总体结构设计及功能模块实现等。 相似文献