全文获取类型
收费全文 | 2298篇 |
免费 | 423篇 |
国内免费 | 527篇 |
专业分类
测绘学 | 192篇 |
大气科学 | 423篇 |
地球物理 | 545篇 |
地质学 | 1149篇 |
海洋学 | 365篇 |
天文学 | 103篇 |
综合类 | 189篇 |
自然地理 | 282篇 |
出版年
2024年 | 19篇 |
2023年 | 47篇 |
2022年 | 155篇 |
2021年 | 155篇 |
2020年 | 126篇 |
2019年 | 125篇 |
2018年 | 130篇 |
2017年 | 126篇 |
2016年 | 126篇 |
2015年 | 122篇 |
2014年 | 125篇 |
2013年 | 138篇 |
2012年 | 123篇 |
2011年 | 139篇 |
2010年 | 124篇 |
2009年 | 136篇 |
2008年 | 120篇 |
2007年 | 113篇 |
2006年 | 97篇 |
2005年 | 87篇 |
2004年 | 70篇 |
2003年 | 76篇 |
2002年 | 74篇 |
2001年 | 77篇 |
2000年 | 60篇 |
1999年 | 87篇 |
1998年 | 62篇 |
1997年 | 57篇 |
1996年 | 53篇 |
1995年 | 57篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 29篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1958年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有3248条查询结果,搜索用时 15 毫秒
851.
INTRODUCTIONTheformationofthePangaeainthePenmangreatlyreducedthedimensionofshelf,sothelateStPenmanmarinesedimentaryrecordsespeciallythatofshallowsea,arelackinginmostpartSoftheworld,exceptthatsomeareasaroundthePaleo--TethySrecordedthecontinuousdepositionacrossthePenmanandTriassicboundary(Schopf,1974).DLiringthattimeYangtzewasablockoverWhichcoveredthelargestshallowshelfofthePenman--Triassicinterval,wherethemostcompletesedimentaryrecordofthatintervalispreserVed(Yangetal.,1993).Itisund… 相似文献
852.
成象光谱图象光谱吸收鉴别模型与矿物填图研究 总被引:1,自引:0,他引:1
本文提出了一种光谱吸收鉴别模型,拟通过矿物光谱吸收特征的鉴别,在成象光谱上实现矿物直接识别与填图。该模型的核心是光谱吸收指数技术(SAI)。从理论上探讨了SAI的本质,应用Hapke光谱模型讨论了SAI与光谱吸收系数(d)以及单散射反照率(w)之间的函数关系,并从成象光谱图象辐射信息传递过程分析了图象SAI与光谱吸收深度的关系,而光谱吸收深度与岩石矿物成分含量之间具有定量关系,这显示了SAI提取矿物定量遥感信息能力。SAI已经成功地应用于FIMS、MAIS和GERIS图象处理与矿物填图,本文通过哈图、塔里木、以及澳大利亚松谷的实例研究,表明SAI是一种有效的提取矿物类型与丰度信息的方法。 相似文献
853.
854.
内蒙古苏尼特左旗古人类遗存点的发现及意义 总被引:2,自引:0,他引:2
内蒙古中北部是一个重要的古人类活动区,从1992年至1994年笔者在该区发现了13处古人类遗存点,获得了大量的石器,包括3773件打制石器和158件磨制石器。这些材料具有十分重要的研究价值。本文对石器进行了分类,并对石器的时代及当时的环境特点进行了探讨。 相似文献
855.
856.
Abstract From the determinations of surface heat flow based on silica geothermometry, residual heat flow, radiogenic heat production of rocks, thermal conductivities of rocks and so on, the temperatures at different depths of the lithosphere in Fujian Province are estimated by using a one-dimensional steady-state model. According to these and the research on geological structures, the possibility of existence of various geothermal systems in Fujian is discussed. The authors consider that in Fujian, geothermal systems related to shallow magmatism do not exist and hot dry rock systems can not be exploited for the time being. However, intermediate- and low-temperature hydrothermal systems are well developed. They are controlled by active faults and distributed widely in southeastern Fujian, but do not have an anomalous heat source. The groundwater circulates at great depths and has a temperature usually less than 150°C with less discharge but good quality. It can be used directly as a valuable geothermal water resource but not suitable to be developed as an energy source. 相似文献
857.
Recent crustal movements in eastern Taiwan were investigated based on geodetic and seismological data as a case study of the tectonics along a colliding plate boundary. Secular horizontal strain along the Longitudinal Valley, a probable arc-continent collision boundary between the Philippine Sea and Eurasion plates, is compressive with a large rate of 2 microstrains/year, and the maximum compression axis trends in NW-SE direction. This means that nearly two-thirds of the convergence rate between the two plates is consumed in the narrow zone along the valley and confirms the view that the valley is the plate boundary between the two. The amount of uplift in the Central Range, deduced from trigonometric leveling, reaches more than one meter during the past 60 years. Such active orogeny is caused by the high strain rate in this area. Horizontal displacement of the Coastal Range, a leading edge of the Philippine Sea plate, has a left-lateral component, suggesting that the boundary is a region of oblique collision and the range moves toward the north, producing subduction of the Philippine Sea plate off the Coast of northeastern Taiwan.An extensional strain pattern is found northeastern Taiwan near Hualien, in northern Taiwan near Ilan, and in southeastern Taiwan south Taitung. In northeastern Taiwan, the direction of the maximum extension axis is nearly parallel to the isodipth contours of deep-focus earthquakes that occurred under the southern part of the Ryukyu Trench. From a model calculation using a finite-element method, this pattern of strain is interpreted as an edge effect of the collision-subduction junction in northeastern Taiwan. The direction of the maximum extension in northern Taiwan forms high angles with the direction of the tectonic line near Ilan stretching from the Okinawa Trough. This fact is harmonious with the view that the Okinawa Trough is spreading. Extensional strain observed in southeastern Taiwan may be related to the eastward subduction since the area is situated on a transition zone, from collision to subduction. 相似文献
858.
本文从形态学和运动学的角度,确定并系统地研究了二十条主要活动断裂。北西向断裂以正-左行走滑型为主,北东向断裂以右行走滑-逆断层为主,两组断裂构成活动断裂网络。用 C14年龄数据计算得到了最近5990—1870年以来,各取样点地壳平均升降速率的变化范围是+3.53mm/a 至-0.65mm/a。用布仑法求得的九龙江活动断裂现代平均滑动速率是1.7mm/a。更新世至现代构造应力场的最大主压应力是以缓倾角、走向为 NW290°左右为特征的。350m 深处最大主压应力是700—760bar。两组断裂交汇形成的高渗透率带,对形成对流型中、低温热水型热田是十分有利的。此外,对该区的地震活动性亦进行了讨论。 相似文献
859.
860.