全文获取类型
收费全文 | 15426篇 |
免费 | 3498篇 |
国内免费 | 5454篇 |
专业分类
测绘学 | 705篇 |
大气科学 | 2437篇 |
地球物理 | 4174篇 |
地质学 | 11422篇 |
海洋学 | 2081篇 |
天文学 | 144篇 |
综合类 | 1492篇 |
自然地理 | 1923篇 |
出版年
2024年 | 131篇 |
2023年 | 311篇 |
2022年 | 550篇 |
2021年 | 629篇 |
2020年 | 683篇 |
2019年 | 831篇 |
2018年 | 729篇 |
2017年 | 731篇 |
2016年 | 862篇 |
2015年 | 865篇 |
2014年 | 1028篇 |
2013年 | 1112篇 |
2012年 | 1126篇 |
2011年 | 1173篇 |
2010年 | 1081篇 |
2009年 | 1105篇 |
2008年 | 1012篇 |
2007年 | 1160篇 |
2006年 | 1181篇 |
2005年 | 964篇 |
2004年 | 835篇 |
2003年 | 777篇 |
2002年 | 675篇 |
2001年 | 637篇 |
2000年 | 544篇 |
1999年 | 565篇 |
1998年 | 443篇 |
1997年 | 424篇 |
1996年 | 418篇 |
1995年 | 331篇 |
1994年 | 279篇 |
1993年 | 268篇 |
1992年 | 187篇 |
1991年 | 136篇 |
1990年 | 124篇 |
1989年 | 95篇 |
1988年 | 86篇 |
1987年 | 53篇 |
1986年 | 28篇 |
1985年 | 31篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 23篇 |
1976年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Common carp (Cyprinus carpio L.) exhibits significant morphological variability in the shape and size of the caudal fin. In this study, we used 190 progeny from two F1 parents to identify and map quantitative trait loci (QTLs) that influence caudal fin length (CFL) and the ratio (RCS) between caudal fin length and standard length (SL) based on a microsatellite genetic map of common carp. A total of 15 QTLs were detected in seven different linkage groups. One significant and eight suggestive QTLs affecting CFL were identified on LG8, LG14, LG29, LG32 and LG44, which explained 8.0%–22.1% of the phenotypic variation; six suggestive QTLs affecting RCS were detected on LG8, LG32, LG46 and LG48, which explained 7.0%–15.4% of the phenotypic variation. The QTLs for caudal fin length detected in this study may serve as a starting point for identification of genes involved in caudal fin development in common carp. 相似文献
103.
深海潜器耐压圆柱壳结构计算和校核方法研究 总被引:1,自引:0,他引:1
文中比较了中美两国潜器规范中各特征量的计算方法和校核准则,分析了异同点,并给出数值算例。针对潜器特性,对目前我国潜器规范中可能需要修改的地方进行了初步分析。 相似文献
104.
In September 2008, Hurricanes Gustav and Ike generated major storm surges which impacted the Lake Pontchartrain estuary in Louisiana. This paper presents analyses of in situ measurements acquired during these storm events. The main data used in the analyses were from three bottom mounted moorings equipped with conductivity, temperature, and depth sensors, acoustic Doppler current profilers (ADCPs), and a semi-permanent laterally mounted horizontal acoustic Doppler profiler (ADP). These moorings were deployed in the three major tidal channels that connect Lake Pontchartrain with the coastal ocean. A process similar to tidal straining was observed: the vertical shear of the horizontal velocity was negligible during the inundation stage, but a shear of 0.8 m/s over a less than 5 m water column was recorded during the receding stage, 2–3 times the normal tidal oscillations. The surge reached its peak in the Industrial Canal 1.4–2.1 h before those in the other two channels. The inward flux of water lasted for a shorter time period than that of the outward flux. The inward flux was also observed to have much smaller magnitude than the outward flux (∼960–1200 vs. 2100–3100 million m3). The imbalance was believed to have been caused by the additional water into Lake Pontchartrain through some small rivers and inundation over the land plus rainfall from the hurricanes. The flux through the Industrial Canal was 8–12%, while the flux through the other two tidal passes ranged between 17% and 70% of the total, but mostly split roughly half-half of the remaining (∼88–92% of the total). 相似文献
105.
106.
107.
108.
109.
110.