全文获取类型
收费全文 | 9770篇 |
免费 | 2167篇 |
国内免费 | 2128篇 |
专业分类
测绘学 | 930篇 |
大气科学 | 1271篇 |
地球物理 | 3572篇 |
地质学 | 4753篇 |
海洋学 | 1417篇 |
天文学 | 526篇 |
综合类 | 828篇 |
自然地理 | 768篇 |
出版年
2024年 | 72篇 |
2023年 | 171篇 |
2022年 | 312篇 |
2021年 | 375篇 |
2020年 | 407篇 |
2019年 | 471篇 |
2018年 | 339篇 |
2017年 | 392篇 |
2016年 | 405篇 |
2015年 | 478篇 |
2014年 | 532篇 |
2013年 | 647篇 |
2012年 | 618篇 |
2011年 | 618篇 |
2010年 | 502篇 |
2009年 | 619篇 |
2008年 | 539篇 |
2007年 | 735篇 |
2006年 | 657篇 |
2005年 | 540篇 |
2004年 | 511篇 |
2003年 | 459篇 |
2002年 | 416篇 |
2001年 | 362篇 |
2000年 | 383篇 |
1999年 | 362篇 |
1998年 | 319篇 |
1997年 | 303篇 |
1996年 | 277篇 |
1995年 | 210篇 |
1994年 | 225篇 |
1993年 | 191篇 |
1992年 | 139篇 |
1991年 | 96篇 |
1990年 | 98篇 |
1989年 | 94篇 |
1988年 | 68篇 |
1987年 | 40篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1954年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A moving particle image velocimetry (PIV) system was successfully developed and used in a large towing tank for ship model tests to observe velocity fields near ship models. The experimental method involved adjustable optical devices for various test conditions and a special particle-seeding device. The streamwise and cross-streamwise flow fields of a yacht model and a tanker model were measured. Ship type, bottom shape, and towing speed were found to be the causes of problems affecting optical access and image quality. Possible solutions, deeper optical ducts, dark painting color, and pre-processed analysis method, were proposed and discussed. 相似文献
72.
73.
-The hydrodynamic forces on a smooth inclined circular cylinder exposed to oscillating flow were experimentally investigated at Reynolds number (Re) in the range 40000-200000 and Keulegan-Capenter number (KC) in the interval from 5-40. In the test, Re number and KC number were varied systematically. The inertia force coefficient (Cu) and the drag force coefficient (CD) in Morison equation were determined from the measured loads and the water particle kinematics. In this analysis a modified form of Morison equation was used since it uses the normal velocity and acceleration. Thus, the applicability of the Cross Flow Principle was assumed. This principle, simply stated, is as follows: the force acting in the direction normal to the axis of a cylinder placed at some oblique angle with the direction of flow is expressed in terms of the normal component of flow only, and the axial component is disregarded. Both the total in-line force coefficient (CF) and transverse force (lift) coefficient (Cf) were analyzed 相似文献
74.
对冲绳海槽1984-1990年的实测热流值,利用数字滤波方法计算,得到反映该区深部地壳热状态的区域热流值为80-160mW/m^2,用B样条函数法对其作数值模拟,计算出海槽地温场模式,并以此研究冲绳海槽海底高热流的形成机制,得出冲绳海槽热流值的区域性变化与綦中地质构造格局呈正相关,高热流是该区现代构造活动所致,其明显特征是地壳减薄,地幔上拱等结论。 相似文献
75.
76.
从1989年4月~1990年10月,我科在69例病人中使用CHIMEHERB人工皮,覆盖治疗了供皮区,Ⅱ°烧伤创面、脱痂创面的残余肉芽创面.临床应用表明:CHIMEHERB人工皮能加快创面的愈合,是目前较好的一种创面覆盖物,用人工皮覆盖创面2~3天后,人工皮干燥,不需再换药,可减轻病人的痛苦. 相似文献
77.
78.
海中悬移质是决定海洋光学性质、海洋水质,河口海岸带演变动力过程的重要环境参数。本文利用模拟遥感反射比数据集建立人工神经网络反演悬移质浓度,并利用东中国海现场同步数据对该算法进行验证。 相似文献
79.
A comparison of two three-dimensional numerical modeling systems for tidal elevations and velocities in the coastal waters is presented. The two modeling systems are: (1) the Princeton Ocean Model (POM) and (2) the MIKE 3 flow model. The model performance results for Singapore's coastal waters show that the predicted tidal elevations from the two hydrodynamic modeling systems are almost identical and are in very good agreement with field measurement data. The simulated tidal current velocities match well with field measurement data at the selected stations, but it seems that the POM provides the slightly better simulation, compared to the MIKE 3 flow model. The depth profiles of the velocities obtained from the two modeling systems may be greatly different at some time, due to the vertical diffusion coefficient calculated from different turbulent sub-models in the two modeling systems. The POM generally predicts larger peak tidal velocities. The maximum speed differences for the model results from the two modeling systems occur in the top and differ from time to time and from location to location, reaching up to 20%. 相似文献
80.
There is the natural habitat of polyps of the common jellyfish Aurelia aurita in the Taniyama area, Kagoshima Bay. We examined the attachment substrata, density, colony structure and strobilation of
the polyps. The polyps were observed only on the horizontal undersurface of floating piers. They attached specifically to
Mytilus shells, solitary ascidians, calcareous polychaete tubes, muddy amphipod tubes and the gap space that fouling animals peeled
off the substrata. The polyp colonies were distributed in patches. Spatial distribution patterns of the polyps within their
colonies were uniform. Strobilation occurred during late December to March, when water temperatures were 16–17°C, and a large
number of ephyrae were released. An increase in man-made structures such as floating piers in coastal areas may lead to bloomings
of Aurelia aurita medusae.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献