全文获取类型
收费全文 | 3661篇 |
免费 | 433篇 |
国内免费 | 464篇 |
专业分类
测绘学 | 1481篇 |
大气科学 | 278篇 |
地球物理 | 670篇 |
地质学 | 1053篇 |
海洋学 | 428篇 |
天文学 | 84篇 |
综合类 | 358篇 |
自然地理 | 206篇 |
出版年
2024年 | 10篇 |
2023年 | 28篇 |
2022年 | 76篇 |
2021年 | 113篇 |
2020年 | 137篇 |
2019年 | 129篇 |
2018年 | 85篇 |
2017年 | 192篇 |
2016年 | 173篇 |
2015年 | 176篇 |
2014年 | 280篇 |
2013年 | 228篇 |
2012年 | 309篇 |
2011年 | 269篇 |
2010年 | 193篇 |
2009年 | 202篇 |
2008年 | 189篇 |
2007年 | 241篇 |
2006年 | 207篇 |
2005年 | 192篇 |
2004年 | 161篇 |
2003年 | 143篇 |
2002年 | 102篇 |
2001年 | 109篇 |
2000年 | 87篇 |
1999年 | 74篇 |
1998年 | 61篇 |
1997年 | 70篇 |
1996年 | 56篇 |
1995年 | 54篇 |
1994年 | 55篇 |
1993年 | 40篇 |
1992年 | 28篇 |
1991年 | 12篇 |
1990年 | 13篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1979年 | 3篇 |
1954年 | 1篇 |
排序方式: 共有4558条查询结果,搜索用时 15 毫秒
31.
32.
冲绳海槽浮岩包裹体的测温试验 总被引:3,自引:2,他引:3
对浮岩中斜长石斑晶中的包裹体及玻璃基质中的包裹体首先进行双面光薄片的镜下观察,然后进行了系统的均化法与爆裂法测温试验。观察与试验结果表明:(1)斜长石中的包裹体均为玻璃质+气泡的两相包裹体,未发现气—液包裹体。固化包裹体为玻璃质,非晶质的固化包裹体外即是大量的气泡,特别是基质当中气泡更为发育,说明熔浆中含有丰富的挥发性组分,同时也说明包裹体形成于较浅的地质条件下。(2)长石中包裹体的均化温度不受包裹体特征不同的影响,均化温度分布范围从910—1250℃,峰值明显,计算的均化温度为Tz=(1081.4±177.9)℃,但还存在有高于1250℃的均化温度峰。包裹体均化法测试结果说明浮岩中斜长石的形成过程至少有两个阶段:第一阶段的岩浆温度在1200—1300℃左右,在此温度下形成的是An值较高的基性斜长石,同时结晶的还有辉石等矿物,斜长石结晶第二个阶段时的熔浆温度在1100℃以下,这一阶段持续的时间长,跨越的温度范围大,应是岩浆在近地表和岩浆喷出过程中的岩浆快速冷却期,同时伴随有矿物大规模晶出。(3)包裹体中的气相部分均聚合成圆形或近圆形,说明温度下降速度较快。斑晶斜长石中部分包裹体与基质玻璃中包裹体的形成温度是连续变化的,这一事实应该与冲绳海槽特殊的地质条件有关 相似文献
33.
文中简述了当今悬沙测试技术的进展,提出了六个悬沙测试领域需要统一认识的基本问题,对悬沙测试技术的近期发展趋势作了简短的展望。 相似文献
34.
35.
An experimental set-up is developed and proved to be effective for laboratory study of an underwater towed system. The experimental technique gives a practical method for monitoring the kinematic and dynamic performance of an underwater towed system in a ship towing tank. Both the theoretical and experimental results in the investigation indicate that the hydrodynamic response of a towed vehicle to the wave induced motion of a towing ship can be significantly reduced by applying a two-part tow method. A comparison of the numerical and experimental results in the investigation demonstrates that the numerical simulation results are close to the experimental data, overall agreement between experimental and theoretical results is satisfactory. The results qualitatively verify the mathematical model of a two-part underwater towed system proposed by Wu and Chwang [Wu, J., Chwang, A.T., 2000. A hydrodynamic model of a two-part underwater towed system. Ocean Engineering 27 (5), 455–472]. 相似文献
36.
37.
The accuracy of the manufacturer’s fall-rate equation for the T-5 Model of expendable bathythermograph (XBT) has been investigated based on about 300 collocated pairs of XBT-CTD (Conductivity-Temperature-Depth profiler) measurements in various climatological regions. We found that the equation systematically overestimates depth by about 5% for the T-5 produced by Tsurumi Seiki, Co. Ltd. (TSK), but almost no bias is associated with the T-5 produced by Sippican, Inc., in USA. The cause of this difference is not clear, because the two manufacturers’ T-5 probes are reported to have identical shape and weight in water. We propose a new fall-rate equation for the TSK T-5: z(t) = 6.54071t - 0.0018691t
2, where z(t) is depth in meters at time, t, in seconds. 相似文献
38.
39.
The accuracy of temperature measurement by the expendable bathythermograph (XBT) is examined for five types of recorders by
comparison with co-located CTD measurements and statistical analysis of temperature profiles including an isothermal layer.
A positive temperature error increasing downward is occasionally detected for two types of Japanese recorder which have been
commonly used among Japanese oceanographic institutions and marine observatories. This error resembles to that reported by
Bailey et al. (1989) and Wright (1991) for a different type of recorders, although its cause is not clearly understood. The irregular
occurrence of the error suggests that the problem is not solely due to the recorders but rather by some inconsistency of the
whole measuring system including them, an XBT probe and sea water. The error is estimated to increase at a rate of O (0.1°C/100 m), and it could be close to 1°C at the deepest part of the profiles (760 m for Tsurumi T-7).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
40.