全文获取类型
收费全文 | 647篇 |
免费 | 134篇 |
国内免费 | 187篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 57篇 |
地球物理 | 121篇 |
地质学 | 415篇 |
海洋学 | 171篇 |
天文学 | 3篇 |
综合类 | 52篇 |
自然地理 | 139篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 24篇 |
2021年 | 33篇 |
2020年 | 34篇 |
2019年 | 33篇 |
2018年 | 24篇 |
2017年 | 33篇 |
2016年 | 55篇 |
2015年 | 37篇 |
2014年 | 45篇 |
2013年 | 46篇 |
2012年 | 32篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 49篇 |
2008年 | 43篇 |
2007年 | 47篇 |
2006年 | 49篇 |
2005年 | 30篇 |
2004年 | 34篇 |
2003年 | 25篇 |
2002年 | 33篇 |
2001年 | 21篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 16篇 |
1997年 | 21篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有968条查询结果,搜索用时 78 毫秒
101.
102.
雷州半岛人工增雨研究与应用 总被引:3,自引:0,他引:3
通过对雷州半岛云水资源气候分布、云的宏观动力学和微观物理学、降水形成机制、人工增雨机制、冷云催化剂与暧云催化剂、播云方式与催化方法的研究和对外场试验的总结,表明:雷州半岛空中具有丰富的云水资源。有暖云降水机制、冷云降水机制和混态云“播种一供水”降水增强机制。人工增雨可进行静力催化和动力催化,使用的冷云催化剂为冰核和致冷剂,暖云催化剂为吸湿性巨核。适宜的人工增雨作业工具为飞机、火箭、地面蚶丙酮溶液燃烟发生器、气球携带AgI焰弹、增雨炮艇等。37高炮不适宜在雷州半岛使用。 相似文献
103.
104.
M.?D.?Rodríguez-AlonsoEmail author M.?Peinado M.?López-Plaza P.?Franco A.?Carnicero J.?C.?Gonzalo 《International Journal of Earth Sciences》2004,93(5):897-920
Petrographic, geochemical and field studies in low grade metamorphic areas (Ciudad Rodrigo-Hurdes-Sierra de Gata domain, CRHSG, central-western Spain) show that Neoproterozoic-Lowermost Cambrian series in the Central Iberian Zone (CIZ) record two kinds of provenance sources including: (1) detrital material derived from recycled orogens and (2) a Cadomian coeval juvenile contribution that governs their isotopic signature. Evidence of magmatism contemporaneous with Neoproterozoic-Cambrian sedimentation is provided by the presence of coherent, massive volcanic rocks (metabasalts, metaandesites, and metarhyolites), volcaniclastic shales, sandstones, conglomerates and breccias. The appearance of volcanogenic lithic fragments and crystals mixed in different proportions with siliciclastic constituents and also present within calcareous components in the sedimentary succession, reinforces this evidence. Although most of the selected volcanic and volcaniclastic samples appear to show tholeiitic affinity, some of them display calc-alkaline affinity. Different trace element ratios, such as Sm/Nd, Nb/Yb and Ta/Yb, suggest a magmatic evolution in the same tectonic setting. The geochemical results reported here support the existence of an active geodynamic setting as a direct contributor to the synsedimentary and magmatic content of the Neoproterozoic–Lowermost Cambrian successions in the CIZ. In particular, the relatively high Nd (T) values and the high range of f Sm/Nd ratios are consistent with an active margin during the Neoproterozoic–Early Cambrian. The existence of tectonic activity is also confirmed by the presence of synsedimentary deformation and volcanic rocks. All of these traits favour a geodynamic model in which the Iberian Cadomian segment represented in the CIZ would have been part of an active northern margin of Gondwana, with an associated magmatic arc and related basins during Neoproterozoic–Lower Cambrian times. A proposed link between the Ossa Morena and the Central Iberian Zones might account for late Cadomian pull-apart basins developed on both sides of the magmatic arc, sharing the same scenario and involving similar magmatic activity during the Neoproterozoic–Cambrian transition.
相似文献
M. D. Rodríguez-AlonsoEmail: Phone: +34-923-294498Fax: +34-923-294514 |
105.
Fluid evolution in the Rushan lode gold deposit of Jiaodong Peninsula, eastern China 总被引:2,自引:0,他引:2
Fang-Fang Hu Hong-Rui Fan Ming-Guo Zhai Cheng-Wei Jin 《Journal of Geochemical Exploration》2006,89(1-3):161
The Rushan gold deposit in the Jiaodong Peninsula is currently the largest lode gold in China. Gold occurs mainly in pyrite- and polymetallic sulfide–quartz vein/veinlet stockworks. Fluid inclusions in the deposit are divided into three main types, namely CO2–H2O, H2O–CO2 ± CH4 and aqueous ones. Microthermometric data show that the pre-gold fluids were CO2-dominant (XCO2 up to 0.53), and the total homogenization temperatures fall in the range of 298377 °C. These fluids, modified by fluid/wallrock reactions, gradually evolved into fluids with less CO2 (XCO2 = 0.010.19) in the main ore-forming stage, and the total homogenization temperatures range from 170 to 324 °C. Hydrogen and oxygen stable isotope data suggest that ore-forming fluids were mixture of magmatic and meteoritic origin. Co-occurrence of gold and sulfides implies that gold was most likely transported in the form of gold–sulfide complexes. The wide distribution of CO2 inclusions means that the pH variation during gold transportation was controlled by CO2 buffering. 相似文献
106.
4—5月南亚高压在中南半岛上空建立的年际变化特征及其与亚洲南部夏季风的关系 总被引:3,自引:0,他引:3
利用1979--2008年NCEP/NCAR逐日再分析资料和向外长波辐射资料讨论了4-5月南亚高压在中南半岛上空建立的年际变化特征及其与亚洲南部夏季风的关系。发现南亚高压建立偏早年其建立过程时间长,中南半岛高空反气旋环流强,建立开始前位于菲律宾群岛以东洋面上空的反气旋环流中心位置较为偏西;偏晚年南亚高压建立过程时间短,中南半岛高空反气旋环流弱,建立开始前西太平洋上空无闭合的反气旋性环流中心。南亚高压建立的早晚与中南半岛地区对流建立发展关系密切,当中南半岛地区对流建立发展较早时,南亚高压建立较早;反之,对流建立发展偏晚时,南亚高压建立偏晚。南亚高压建立早晚年,亚洲南部夏季风的爆发存在明显差异。南亚高压建立偏早年,孟加拉湾东部一中南半岛夏季风和南海夏季风爆发早;建立偏晚年,孟加拉湾东部一中南半岛夏季风和南海夏季风爆发晚,因此南亚高压在中南半岛上空建立的早晚对后期亚洲南部夏季风的爆发具有较好的指示意义。 相似文献
107.
利用卫星云图、 多普勒天气雷达资料、 常规观测资料和MM5模式模拟结果, 分析了2005年12月4日典型冷涡造成山东半岛暴雪的云带变化、 对流单体的生成与发展、 低空急流特征及雷达强回波带的变化特征。结果表明: 冬季冷涡携带强冷空气南下, 经过渤海暖湿下垫面后影响山东半岛时, 卫星云图上从渤海到山东半岛可以清楚地分析出造成暴雪的西南-东北向结构特征的横向云带; 雷达图上, 在渤海到山东半岛形成一强降雪回波带, PPI径向速度图上可清楚地分析出暴雪区的低空急流和中尺度对流的低空辐合, 雷达径向速度垂直剖面反映暴雪产生在零速度线附近和低空急流的存在; MM5模式模拟结果显示: 暴雪发生时山东半岛在1.5 km存在低空急流, 水平风的时间-高度垂直剖面反映暴雪发生时干冷空气经过暖湿的渤海海面在700 hPa以下出现暖平流, 垂直上升运动和散度的低层辐合、 高层辐散与雷达图像反映的强降雪回波是相对应的。 相似文献
108.
IMPACTS OF TWO TROPICAL CYCLONES EXPERIENCING EXTRATROPICAL TRANSITION DURING NORTHWARD PROGRESSION
ON THE RAINFALL OF LIAODONG PENINSULA 总被引:2,自引:1,他引:1
Both of Typhoon Winnie (9711) and Matsa (0509) underwent an extratropical transition (ET)
process when they moved northward after landfall and affected Liaodong Peninsula. However, Matsa
produced half as much rainfall as Winnie, although it struck Liaodong Peninsula directly while Winnie
passed through the Bohai Sea. The relations between the ET processes and the precipitation over Liaodong
Peninsula are examined. The result shows that the precipitation difference between Winnie and Matsa was
closely related to the interactions between the westerly systems and typhoons during their ET processes.
Winnie was captured by the upper westerly trough and then coupled with it when moving to the
mid-latitudes, and the positive anomaly of moist potential vorticity (MPV) was transported downward from
the upper troposphere over the remnant circulation of the tropical cyclone (TC). It was favorable to the
interaction between tropical warm and wet air and westerly cold air, causing convective cloud clusters to
form and develop. The rain belt composed of several meso-β cloud clusters over the Liaodong Peninsula,
resulting in heavy rainfall. On the other hand, Matsa did not couple with any upper trough during its ET
process and the positive anomaly of MPV in the upper troposphere and its downward transfer were weak.
Only one meso-β cloud cluster occurred in Matsa’s rain belt during its ET process that tended to lessen
rainfall over Liaodong Peninsula. 相似文献
109.
This paper is focused on the study of rainfall yield characteristics of electrical storms observed over the Northern Iberian Peninsula during 1992–1996. To this aim Principal Components Analysis (PCA) and Self-Organizing Maps (SOM) method have been used. The SOM method is a group of artificial neural networks based on the topological properties of the human brain. Results clearly suggest that there exist three different meteorological patterns that are linked to the characteristics of electrical events found in the study area. In winter, most of the electrical events are formed under oceanic advection (NW air fluxes). On these cases, mean rainfall yield estimates reach values of 700 104 m3 per cloud to ground lightning flash (CG flash). During summer most frequent electrical storms are associated to local instability shooting by surface heating with advection of humidity coming from the Iberian Peninsula. Under these meteorological situations, rain is scarcer if compared with oceanic events but lightning CG counts reach the maximum values found in the area (about 10 CG counts per 20 × 20 km2 and day) giving this way the smallest rainfall yield with a mean value of 15 104 m3 per CG flash. Iberian air fluxes associated with cold air in upper parts of the atmosphere represent the third meteorological pattern found. This pattern is most common in spring and autumn but is not unusual in the rest of the seasons. In those cases mean rainfall yield in the area is about 150 104 m3 per CG flash. In all electrical episodes K instability index is greater than 15 °C but in the most lightning producing events, this index reaches in the area values greater than 24 °C. PCA results pointed out that there exists a relationship between rain and CG counts expressed by the first principal component computed from standardized data. However, we must notice that no event is solely linked to this axis, since a seasonal influence which decreases lightning production when rain increases is always present. Results found are of great interest for short term forecasting of flashfloods in mountainous areas like the Spanish Basque Country region. 相似文献
110.
山东半岛一次强暴雨的分析和数值模拟 总被引:4,自引:3,他引:1
利用T213资料、常规观测资料和多普勒雷达资料,对2004年8月5日发生在山东半岛东部的一次大暴雨过程进行了数值模拟和分析,在模拟结果比较成功的基础上,利用细网格模拟资料重点分析了高、低空急流和850 hPa低压与暴雨的关系,以及山东半岛地形的动力作用。结果表明:暴雨强回波从南向北传播时强度逐渐增强,反映了中尺度对流系统的结构和发展;对流云团首先在低空急流中心左前方生成,与副热带高压边缘的西南暖湿气流有关,中尺度高空急流是伴随对流由强高空出流而形成,高、低空急流的耦合作用有利于强对流天气的维持和发展;在副热带高压西侧边界层激发出一个中β尺度低压,该低压形成后与暴雨区相伴移动,且移动路径与山东半岛东部地形分布有关,山东半岛地形对西南暖湿气流阻挡和绕流的动力作用是导致威海附近强暴雨的原因之一。 相似文献