全文获取类型
收费全文 | 101881篇 |
免费 | 17131篇 |
国内免费 | 22381篇 |
专业分类
测绘学 | 10629篇 |
大气科学 | 13752篇 |
地球物理 | 19750篇 |
地质学 | 53172篇 |
海洋学 | 11592篇 |
天文学 | 9913篇 |
综合类 | 7043篇 |
自然地理 | 15542篇 |
出版年
2024年 | 339篇 |
2023年 | 1052篇 |
2022年 | 2921篇 |
2021年 | 3428篇 |
2020年 | 3561篇 |
2019年 | 4004篇 |
2018年 | 3416篇 |
2017年 | 3984篇 |
2016年 | 4112篇 |
2015年 | 4631篇 |
2014年 | 5654篇 |
2013年 | 5998篇 |
2012年 | 6173篇 |
2011年 | 6679篇 |
2010年 | 5762篇 |
2009年 | 7090篇 |
2008年 | 6895篇 |
2007年 | 7413篇 |
2006年 | 7064篇 |
2005年 | 6413篇 |
2004年 | 5790篇 |
2003年 | 5299篇 |
2002年 | 4596篇 |
2001年 | 4109篇 |
2000年 | 3863篇 |
1999年 | 3487篇 |
1998年 | 3046篇 |
1997年 | 2475篇 |
1996年 | 2182篇 |
1995年 | 1861篇 |
1994年 | 1838篇 |
1993年 | 1548篇 |
1992年 | 1104篇 |
1991年 | 854篇 |
1990年 | 680篇 |
1989年 | 553篇 |
1988年 | 431篇 |
1987年 | 266篇 |
1986年 | 188篇 |
1985年 | 148篇 |
1984年 | 73篇 |
1983年 | 53篇 |
1982年 | 59篇 |
1981年 | 40篇 |
1980年 | 50篇 |
1979年 | 41篇 |
1978年 | 57篇 |
1977年 | 37篇 |
1976年 | 7篇 |
1954年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
崂山花岗岩地区含锶、偏硅酸矿泉水的形成机理 总被引:1,自引:0,他引:1
报道了崂山花岗岩地区矿泉水的特征。指出其矿泉类型为含锶、偏硅酸型,并讨论了其形成机理。 相似文献
973.
城市与工程测量EDM导线技术标准的分析 总被引:1,自引:0,他引:1
基于导线测量误差理论与电磁测距(EDM)导线的特性,分析讨论了城市与工程测量EDM导线的各项技术参数,提出了各级EDM导线技术标准的建议,通过计算验证所给出的这些技术指标是合理可靠的。 相似文献
974.
975.
热带气旋活动对中国夏季雨带类型与ENSO的响应关系 总被引:2,自引:0,他引:2
本文分析研究了热带气旋1)活动与中国夏季2)3组(包括8种)主要多雨带类型的响应关系。同时对热带气旋活动与夏季大陆气温和ENSO事件的始终时间的响应关系,也进行了探讨。分析表明,夏季中国的雨带分布特征对热带气旋活动有着十分重要的指示意义。热带气旋活动与中国大陆气温有着正相关关系,与ENSO事件的发生有着反相关关系 相似文献
976.
本文从动力学定律出发,推导了一个线性的、具有下垫面温度耦合的大气环流的统计—动力模式,并用该模式对500hPa高度场及1000hPa温度场作1~30天的平均预报试验。模式的预报结果大大优于惯性预报,但耦合与不耦合的结果差别不大。 相似文献
977.
Two processes are generally explained as causes of temporal changes in the stoichiometric silicon/nitrogen (Si/N) ratios of
sinking particles and of nutrient consumption in the surface water during the spring diatom bloom: (1) physiological changes
of diatom under the stress of photosynthesis of diatom and (2) differences of regeneration between silicon and nitrogen. We
investigated which process plays an important role in these changes using a one-dimensional ecosystem model that explicitly
represents diatom and the other non-silicious phytoplankton. The model was applied to station A7 (41°30′ N, 145°30′ E) in
the western North Pacific, where diatom regularly blooms in spring. Model simulations show that the Si/N ratios of the flux
exported by the sinking particles at 100 m depth and of nutrient consumptions in the upper 100 m surface water have their
maxima at the end of the spring diatom bloom, the values and timings of which are significantly different from each other.
Analyses of the model results show that the differences of regeneration between silicon and nitrogen mainly cause the temporal
changes of the Si/N ratios. On the other hand, the physiological changes of diatoms under stress can hardly cause these temporal
changes, because the effect of the change in the diatom's uptake ratio of silicon to nitrogen is cancelled by that in its
sinking rate. 相似文献
978.
Several large deployments of neutrally buoyant floats took place within the Antarctic Intermediate (AAIW), North Atlantic Deep Water (NADW), and the Antarctic Bottom Water (AABW) of the South Atlantic in the 1990s and a number of hydrographic sections were occupied as well. Here we use the spatially and temporally averaged velocities measured by these floats, combined with the hydrographic section data and various estimates of regional current transports from moored current meter arrays, to determine the circulation of the three major subthermocline water masses in a zonal strip across the South Atlantic between the latitudes of 19°S and 30°S. We concentrate on this region because the historical literature suggests that it is where the Deep Western Boundary Current containing NADW bifurcates. In support of this notion, we find that a net of about 5 Sv. of the 15–20 Sv that crosses 19°S does continue zonally eastward at least as far as the Mid-Atlantic Ridge. Once across the ridge it takes a circuit to the north along the ridge flanks before returning to the south in the eastern half of the Angola Basin. The data suggest that the NADW then continues on into the Indian Ocean. This scheme is discussed in the context of distributions of dissolved oxygen, silicate and salinity. In spite of the many float-years of data that were collected in the region a surprising result is that their impact on the computed solutions is quite modest. Although the focus is on the NADW we also discuss the circulation for the AAIW and AABW layers. 相似文献
979.
980.