全文获取类型
收费全文 | 4838篇 |
免费 | 1253篇 |
国内免费 | 1777篇 |
专业分类
测绘学 | 836篇 |
大气科学 | 827篇 |
地球物理 | 899篇 |
地质学 | 3196篇 |
海洋学 | 907篇 |
天文学 | 56篇 |
综合类 | 493篇 |
自然地理 | 654篇 |
出版年
2024年 | 47篇 |
2023年 | 148篇 |
2022年 | 347篇 |
2021年 | 434篇 |
2020年 | 345篇 |
2019年 | 397篇 |
2018年 | 381篇 |
2017年 | 325篇 |
2016年 | 334篇 |
2015年 | 405篇 |
2014年 | 356篇 |
2013年 | 417篇 |
2012年 | 438篇 |
2011年 | 444篇 |
2010年 | 403篇 |
2009年 | 386篇 |
2008年 | 366篇 |
2007年 | 339篇 |
2006年 | 289篇 |
2005年 | 233篇 |
2004年 | 195篇 |
2003年 | 129篇 |
2002年 | 127篇 |
2001年 | 117篇 |
2000年 | 110篇 |
1999年 | 73篇 |
1998年 | 54篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 31篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1976年 | 2篇 |
1957年 | 2篇 |
1954年 | 5篇 |
排序方式: 共有7868条查询结果,搜索用时 15 毫秒
251.
The resolution of ocean reanalysis datasets is generally low because of the limited resolution of their associated numerical models. Low-resolution ocean reanal... 相似文献
252.
253.
Accurate estimates of precipitation are fundamental for hydrometeorological and ecohydrological studies, but are more difficult in high mountainous areas because of the high elevation and complex terrain. This study compares and evaluates two kinds of precipitation datasets, the reanalysis product downscaled by the Weather Research and Forecasting(WRF) output, and the satellite product,the Tropical Rainfall Measuring Mission(TRMM) Multisatellite Precipitation Analysis(TMPA) product, as well as their bias-corrected datasets in the Middle Qilian Mountain in Northwest China. Results show that the WRF output with finer resolution performs well in both estimating precipitation and hydrological simulation, while the TMPA product is unreliable in high mountainous areas. Moreover,bias-corrected WRF output also performs better than bias-corrected TMPA product. Combined with the previous studies, atmospheric reanalysis datasets are more suitable than the satellite products in high mountainous areas. Climate is more important than altitude for the ‘falseAlarms' events of the TRMM product. Designed to focus on the tropical areas, the TMPA product mistakes certain meteorological situations for precipitation in subhumid and semiarid areas, thus causing significant ‘falseAlarms' events and leading to significant overestimations and unreliable performance. Simple linear bias correction method, only removing systematical errors, can significantly improves the accuracy of both the WRF output and the TMPA product in arid high mountainous areas with data scarcity. Evaluated by hydrological simulations, the bias-corrected WRF output is more reliable than the gauge dataset. Thus, data merging of the WRF output and gauge observations would provide more reliable precipitation estimations in arid high mountainous areas. 相似文献
254.
255.
256.
Analyzing raw material's structure and performance of bentonite from Panzhihua in Sichuan, the authors think that it is adequate for agglomerant of iron smelting. According to its composition and property we have researched the purification and modification of I/S bentonite under conditions of different dispersants and sodium agent. XRD test result reveals that the essential minerals of Panzhihua bentonite are I/S mixed-layer ones, and FTIR analysis shows that when adding 1 5% sodium pyrophosphate to the bentonite slurry during purification, the composition of quartz in bentonite decreases to less than 4% and I/S is more than 90%. The optimized modification technic conditions are Na2CO3 (4%) and CMC-Na (3%) as modified agents, the clay and water are 10 vs. 1, and the temperature is 75℃. It is 40 min for stirring time and reacting time is 4 h. Under the conditions we can get the modified I/S bentonite with colloid index more than 500 ml/15 g. 相似文献
257.
258.
259.
以IGRF全球地磁位模型为基础,设计地磁测量参考场计算软件,实现地磁场参数长波分量的时间域与空间域离散点计算,为野外磁力测量相关数据采集与仪器配置提供先验信息,使数据采集的作业效率及可靠性大大提高。 相似文献
260.
人工藻礁是进行藻场建设的重要手段,但由于海胆等食藻类生物的摄食,将会影响藻类的生长,从而影响人工藻场的建设效果.为解决人工藻场建设中海胆的食害问题,从礁体自身设计出发,实验设计了8种不同形状的藻礁,选用光棘球海胆和中间球海胆为实验对象,观察比较了不同形状藻礁对海胆攀爬的阻碍效果,实验发现:侧周面为锯齿形或侧周面缠挂多孔柔性材料的礁型可有效阻止海胆攀爬,起到防止海胆摄食礁顶藻类的目的.研究结果为人工藻礁的设计提供了参考依据. 相似文献