全文获取类型
收费全文 | 6539篇 |
免费 | 1180篇 |
国内免费 | 1549篇 |
专业分类
测绘学 | 526篇 |
大气科学 | 1392篇 |
地球物理 | 1733篇 |
地质学 | 3108篇 |
海洋学 | 784篇 |
天文学 | 308篇 |
综合类 | 725篇 |
自然地理 | 692篇 |
出版年
2024年 | 43篇 |
2023年 | 126篇 |
2022年 | 316篇 |
2021年 | 354篇 |
2020年 | 290篇 |
2019年 | 318篇 |
2018年 | 351篇 |
2017年 | 322篇 |
2016年 | 392篇 |
2015年 | 349篇 |
2014年 | 401篇 |
2013年 | 372篇 |
2012年 | 326篇 |
2011年 | 378篇 |
2010年 | 361篇 |
2009年 | 398篇 |
2008年 | 379篇 |
2007年 | 335篇 |
2006年 | 255篇 |
2005年 | 265篇 |
2004年 | 200篇 |
2003年 | 197篇 |
2002年 | 201篇 |
2001年 | 199篇 |
2000年 | 203篇 |
1999年 | 287篇 |
1998年 | 255篇 |
1997年 | 209篇 |
1996年 | 218篇 |
1995年 | 160篇 |
1994年 | 165篇 |
1993年 | 166篇 |
1992年 | 134篇 |
1991年 | 71篇 |
1990年 | 63篇 |
1989年 | 51篇 |
1988年 | 43篇 |
1987年 | 23篇 |
1986年 | 26篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1958年 | 4篇 |
排序方式: 共有9268条查询结果,搜索用时 0 毫秒
891.
892.
目前 ,我国气象部门相当普遍地拥有气象卫星观测资料 ,但是 ,这些资料如何在城市气象服务以及为城市建设规划等方面的决策研究中发挥作用 ,急待进一步研究并开展工作。本文试图通过合理的反演处理 ,给出卫星观测对地面温度的测量结果 ,由此可比较细致地分析了解地面热状况及其与土地利用类型 ,地面覆盖性质等的关系。本文利用有限的 NOAA- AVHRR气象卫星遥感资料 ,采用修正的 Ulivieri分裂窗方法反演出同期的地表温度场 ,通过对北京地区的卫星观测资料进行算例分析 ,揭示出一个 2 0 0 km× 2 0 0 km范围内的地面温度分布特征。反演结果可以明显地揭示出城市热岛现象的变化规律 ,并且能较为清楚地反映出相对的高温区和低温区 相似文献
893.
一次梅雨锋暴雨过程多尺度特征的诊断分析 总被引:6,自引:2,他引:6
文中对 1998年 6月 12~ 15日长江中下游地区入汛后最强的一次梅雨锋大暴雨过程进行了诊断分析。结果表明 ,此次暴雨是在 3种不同尺度天气系统的共同作用下形成的。中高纬的双阻型和副热带高压位置偏南 ,是引发该暴雨过程的大尺度背景条件 ;天气尺度的低压槽为该阶段的连续大暴雨提供了动力条件 ,它的前部存在一个低层辐合、正涡度和高层辐散、负涡度的带状区域。α中尺度上 ,该暴雨系统的垂直结构为中低层强烈的辐合和上层的辐散 ,其中心有着强烈的上升气流 ;同时在中高层 ,系统的南侧有一个高空急流强迫产生的次级环流。这种α中尺度暴雨系统的三维结构为强暴雨的形成提供了必要的动力、水汽和不稳定性条件。 相似文献
894.
The Northward Shift of Climatic Belts in China During the Last 50 Years and the Corresponding Seasonal Responses 总被引:29,自引:0,他引:29
Along the meridian of 105°E, the Chinese region are divided into two parts, east and west. The results show that in the east part of China the temperate extratropical belt, the warm extratropical belt,and the northern subtropical belt shift northward significantly, whereas the middle subtropical belt and the southern subtropical belt have less or no change. As for the northern subtropical belt, the maximal northward shift can reach 3.7 degrees of latitude. As for the warm extratropical belt, along the meridian of 120°-125°E, the maximal northward shift can reach 3-4 degrees. In the west part of China, each climatic belt changes little. Only in the Xinjiang area are the significant northward shifts. Correspondingly, it is found that in the last 50 years the traditional seasons have changed. For Beijing, Hailar, and Lanzhou, in general, summer becomes longer and winter shorter over the last 50 years. Summer begins early and ends late with respect to early 1950s. Contrary to the summer, winter begins la 相似文献
895.
Xingwen Jiang Yueqing Li Song Yang Guangbi He 《Theoretical and Applied Climatology》2014,117(3-4):565-577
The variability of climate in the lee side of the Tibetan Plateau (TP) often exhibits unique features. In this study, the authors investigate the variations of early autumn rainfall in the lee side of the TP (LSTP). The rainfall amount and number of rain days in LSTP increase from August to September. The center of heavy and torrential rains during September is located in LSTP as well. These unique features are attributed to later withdrawal of the East Asian summer monsoon in the middle and higher troposphere compared to the lower troposphere and stronger South Asian summer monsoon and thermal forcing of the TP. The September rainfall in LSTP experienced strong interdecadal fluctuation, with overall below normal rainfall from mid-1980s to late 2000s, while there was no apparent long-term trend in the August and October rainfall amount. The above normal September rainfall is associated with an anomalous anticyclone over the western North Pacific, a weaker-than-normal ridge around the Lake Baikal, a stronger-than-normal East Asian jet stream, and warmer air over the southeastern TP. The interdecadal decrease in rainfall in September may be caused by the central equatorial Pacific warming, which induces an anomalous cyclone over the western North Pacific. The September anomalous cyclone is stronger and more westward compared to that in August and October, and thus favors the below normal rainfall in LSTP. 相似文献
896.
897.
898.
899.
The transboundary Sesan and Srepok sub-basins (2S) are the “hot-spot” areas for reservoir development in the Lower Mekong region, with 12 reservoirs built in the Vietnam territory. This study examines the impacts of reservoir operations in Vietnam and projected climate change on the downstream hydrologic regime of the 2S Rivers by jointly applying the Soil Water Assessment Tool (SWAT) and Water Evaluation and Planning (WEAP) models. Different scenarios of reservoir operation are considered and simulated to assess their impact on annual, seasonal, and monthly flow regimes under maximum hydropower capacity generation with and without taking into account the minimum flow requirement downstream near the Vietnam border with Cambodia. The precipitation and temperature projections from the high-resolution regional climate model HadGEM3-RA under two Representative Concentration Pathways, 4.5 and 8.5, of HadGEM2-AO are used as future climate change scenarios for the impact assessment. The study results show that reservoir operation leads to an increase in the dry season stream flows and a decrease in the wet season stream flows. The monthly flow regime exhibits considerable changes for both the Sesan and Srepok Rivers but with different magnitudes and patterns of increase and decrease. Climate change is likely to induce considerable changes in stream flows, though these changes are comparatively lower than those caused by reservoir operation. Climate change is likely to have both counterbalancing and reinforcing effects over the impact of reservoir operation, reducing changes during dry season but increasing changes in most of the other months. 相似文献
900.