全文获取类型
收费全文 | 48820篇 |
免费 | 933篇 |
国内免费 | 466篇 |
专业分类
测绘学 | 1118篇 |
大气科学 | 3602篇 |
地球物理 | 10263篇 |
地质学 | 17124篇 |
海洋学 | 3976篇 |
天文学 | 10676篇 |
综合类 | 79篇 |
自然地理 | 3381篇 |
出版年
2020年 | 329篇 |
2019年 | 335篇 |
2018年 | 775篇 |
2017年 | 708篇 |
2016年 | 952篇 |
2015年 | 716篇 |
2014年 | 980篇 |
2013年 | 2313篇 |
2012年 | 1191篇 |
2011年 | 1713篇 |
2010年 | 1464篇 |
2009年 | 2050篇 |
2008年 | 1846篇 |
2007年 | 1769篇 |
2006年 | 1707篇 |
2005年 | 1464篇 |
2004年 | 1528篇 |
2003年 | 1445篇 |
2002年 | 1395篇 |
2001年 | 1218篇 |
2000年 | 1166篇 |
1999年 | 1083篇 |
1998年 | 1066篇 |
1997年 | 1067篇 |
1996年 | 855篇 |
1995年 | 825篇 |
1994年 | 787篇 |
1993年 | 724篇 |
1992年 | 659篇 |
1991年 | 592篇 |
1990年 | 657篇 |
1989年 | 553篇 |
1988年 | 548篇 |
1987年 | 646篇 |
1986年 | 559篇 |
1985年 | 791篇 |
1984年 | 861篇 |
1983年 | 872篇 |
1982年 | 728篇 |
1981年 | 701篇 |
1980年 | 707篇 |
1979年 | 641篇 |
1978年 | 663篇 |
1977年 | 581篇 |
1976年 | 611篇 |
1975年 | 574篇 |
1974年 | 575篇 |
1973年 | 576篇 |
1972年 | 378篇 |
1971年 | 317篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
431.
432.
Abstract The Taiwan orogen has been the focus of a number of models of mountain building processes, but little attention has been paid to high‐pressure (HP) metamorphic rocks that are found as exotic blocks intermingled within the deepest units of the mountain belt. In this study, we re‐appraise from updated petrological and thermodynamic databases the physical conditions of HP metamorphism in Taiwan, and we combine our findings with available geochronological data to estimate the thermal history of these rocks. Our results indicate that peak metamorphic conditions of ~550 °C and 10–12 kbar have been followed by a rapid isothermal decompression, with exhumation possibly as rapid as burial. These units have subsequently been stored at a pressure of ~3 kbar for ~4–5 Myr, before their final exhumation, probably facilitated by the accretion of passive margin sequences during the Late Cenozoic collision. Therefore, HP units in Taiwan maintain a record of processes at depth from the early stages of oceanic subduction to the present arc‐continent collision. 相似文献
433.
Eduardo E. Alonso Sarah M. Springman Charles W. W. Ng 《Geotechnical and Geological Engineering》2008,26(6):817-826
Two large-scale “in situ” demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment)
involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer
water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced
by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive
cells, psychrometers, TDR’s) and a comparison of fill behaviour with modelling results. The long term performance of some
instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data
during long transient periods characterised by very large variations of suction within the bentonite. 相似文献
434.
饱和粉砂不稳定性的试验研究 总被引:3,自引:0,他引:3
通过对净砂和级配良好粉砂(含10 %粉土)进行一系列三轴固结不排水试验(CU),研究了粉土、孔隙比和围压对饱和粉砂不稳定性的影响。试验结果表明,净砂与粉砂在不排水剪切条件下均会出现应变软化现象(即不稳定性)。同一围压下脆性指数(IB)随孔隙比增加,但不稳定线的应力比随孔隙比增加而减小。引用等效粒间孔隙比(ege)后,净砂和粉砂在ege-ln p?平面上拥有基本相同的临界状态线。在临界状态理论及等效粒间孔隙比的基础上,提出在同一修正状态参数(?ge)下净砂和级配良好粉砂有相似的不稳定性。 相似文献
435.
F. Shuttleworth
J. Wardley Smith
《Marine pollution bulletin》1971,2(12):191-192436.
437.
438.
A high resolution Boomer system was used to investigate the bedrock configuration of part of Port Jackson, New South Wales. The continuous reflection profiling technique was successful in delineating a channel incised in bedrock under a thickness of up to 60 m. of unconsolidated sediment covered by up to 20 m. of water. 相似文献
439.
440.
J. W. Norman 《The Photogrammetric Record》1968,6(32):133-149
The geologist's use of air photographs and the characteristics studied by photogeologists are briefly described. The influence of photographic factors such as scale, season, time of day, film type, processing, overlap and dimensional accuracy are considered from the geologist's viewpoint. 相似文献