全文获取类型
收费全文 | 1642篇 |
免费 | 266篇 |
国内免费 | 573篇 |
专业分类
测绘学 | 113篇 |
大气科学 | 271篇 |
地球物理 | 158篇 |
地质学 | 434篇 |
海洋学 | 1215篇 |
天文学 | 16篇 |
综合类 | 165篇 |
自然地理 | 109篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 90篇 |
2021年 | 79篇 |
2020年 | 80篇 |
2019年 | 93篇 |
2018年 | 86篇 |
2017年 | 81篇 |
2016年 | 73篇 |
2015年 | 97篇 |
2014年 | 112篇 |
2013年 | 137篇 |
2012年 | 116篇 |
2011年 | 96篇 |
2010年 | 69篇 |
2009年 | 94篇 |
2008年 | 121篇 |
2007年 | 117篇 |
2006年 | 120篇 |
2005年 | 127篇 |
2004年 | 98篇 |
2003年 | 87篇 |
2002年 | 70篇 |
2001年 | 74篇 |
2000年 | 63篇 |
1999年 | 52篇 |
1998年 | 38篇 |
1997年 | 22篇 |
1996年 | 19篇 |
1995年 | 28篇 |
1994年 | 16篇 |
1993年 | 18篇 |
1992年 | 10篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1979年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有2481条查询结果,搜索用时 93 毫秒
991.
太平洋-印度洋暖池次表层水温与南海夏季风爆发 总被引:3,自引:0,他引:3
为探索太平洋—印度洋热带海域次表层水温对南海季风的影响,用Argo剖面浮标等实测资料,分析了太平洋—印度洋暖池次表层水温异常对南海夏季风爆发的影响。结果表明:冬季,太—印暖池次表层水温偏暖(冷)时,翌年南海夏季风爆发时间偏早(晚)是主要现象。太—印暖池次表层水温偏暖,可能引起Walker环流加强,西太平洋副热带高压偏弱,中心位置偏北偏东,南海和西太平洋上空对流层下层有气旋性距平环流出现,有利于低空西到西南气流的加强,导致南海夏季风爆发偏早;太—印暖池次表层水温偏冷,可能引起Walker环流东移并减弱,西太平洋副热带高压偏强,中心位置偏南偏西,南海和西太平洋上空对流层下层有反旋性距平环流出现,不利于低空西到西南气流的加强,导致南海夏季风爆发偏晚。结论:冬季,太—印暖池次表层水温偏暖(冷),翌年南海夏季风爆发时间偏早(晚)是主要现象。 相似文献
992.
Marcus Silva Moacyr Araujo Jacques Servain Pierrick Penven Carlos A.D. Lentini 《Ocean Modelling》2009,30(4):256-269
The southwestern tropical Atlantic (05°S–25°S/20°W–47°W), where part of the South Equatorial Current (SEC) enters at its eastern border, is of particular interest as it is fed by many western boundary currents along the eastern Brazilian continental shelf. However, the long-term variability of the dynamics in this region, which are also important as they contribute to the climate over northeastern Brazil, is largely unknown. We use the Regional Ocean Model System (ROMS) here for the first time in this area to simulate the ocean circulation with an isotropic horizontal grid resolution of 1/12° and 40 terrain-following layers. As a primary evaluation of the ROMS configuration, we explore surface and vertical thermal structures, the surface mixed layer, and mass transports within the upper levels. Interannual variability results are compared with the first two-year series of observed thermal profiles derived from the three PIRATA-SWE moorings. The simulated thermal structure in the upper ocean layers agrees well with in-situ data. ROMS simulations point out a broad and relatively weak SEC flow composed of a sequence of more or less defined near-surface cores. The westward SEC transport for the upper 400 m along the PIRATA-SWE section, calculated from the ROMS simulation for 2005–2007, shows an average volume transport of 14.9 Sv, with a maximum observed in JFM (15.7 Sv), and a minimum during MJJ (13.8 Sv). ROMS results indicate that the 2005–2007 seasonal near-surface westward SEC transport is modulated by the zonal wind variability. Three zonal sections extending from the American continent to the PIRATA buoy sites confirm that stronger northward NBUC transport and decreasing BC transport were achieved during May 2006 and May 2007, i.e. at the time the sSEC bifurcation reaches its southernmost position. On the other hand, the maximum southward BC flow was verified during January 2006, January 2007 and March 2007, with a minimum northward NBUC flow in December 2005 and October/December 2006, corresponding to the period when the sSEC bifurcation reaches its lowest latitude (OND). Sea Surface Height (SSH) and the surface Eddy Kinetic Energy (EKE) derived from simulations and AVISO Rio05 product point out the highest surface meso-scale activity (EKE 50 cm2 s−2) along the cSEC and NBUC/BC patches. Preliminary results provide additional ingredients in the complexity of the SEC divergence region and encourage us to conduct a more detailed exploration of the dynamics of this region using the ROMS. This also shows the need to continue, extend, and vertically upgrade the observational PIRATA-SWE array system, especially with more levels of salinity measurements and the installation of current measurements. 相似文献
993.
994.
Based on the analysis of ocean dynamic condition and sediment environment, conclusions can be drawn that strong wind is an essential factor influencing sudden sedimentation in outer channel. Through theoretical analysis, it changes the complex process that wind raises wave, wave tilts sediment and current transports sediment into a comprehensive factor, and obtains mathematical formula between effective wind energy and the thickness of sudden sedimentation. The parametees in this formula are determined with field data of Huanghua Port. It may be used to predict siltation thickness and volume along the channel. By analyzing and comparing the difference in ocean hydrodynamic conditions and seabed material between Huanghua Port and Binzhou Port, the proposed formula can be used to predict sudden sedimentation in Binzhou Port and the calculated results is rehable. By predicting it on different combination plans among different recurrence in- tervals, entrance locations and channel classes, it provides references for the plane design of Binzhou Port. 相似文献
995.
Mixed and mixing layer depths simulated by an OGCM 总被引:1,自引:0,他引:1
The global distributions of the mixed layer depth h
D
, representing the depth of uniform density, and the mixing layer depth h
K
, representing the depth of active turbulent mixing, were simulated using an ocean general circulation model (OGCM), and compared
with each other, as well as with the mixed layer depth from the climatological data h
D
*. The comparison between h
D
and h
D
* suggested that the threshold density difference Δ σ
θ
should decrease from 0.09 kg m−3 to 0.02 kg m−3 with increasing latitude for consistent comparison between two mixed layer depths, due to the different nature of density
profiles depending on latitude. The comparison between h
D
and h
K
revealed that h
K
is deeper than h
D
in the region where strong subsurface shear is present, such as the equatorial ocean and the region of the western boundary
current. On the other hand, h
K
is shallower than h
D
in the high latitude ocean during convective cooling and early restratification. 相似文献
996.
有害赤潮发生频度有逐年增加的趋势, 建设赤潮的早期监测和预警系统是一个难点。文章研究表明, 珠江口赤潮前后, 叶绿素a浓度和细胞密度变化范围分别为0.9—31.1mg•m-3 和1.28×104 —1.76×106cell•L-1, 优势藻为聚生角毛藻; 高光谱辐射计获取的光漫射衰减系数、遥感反射率和荧光强度可反演叶绿素a浓度和细胞密度, 其中反演叶绿素a浓度的平均相对均方根差(RRMS)为30.6%、33.8%和77.4%, 而反演细胞密度的平均RRMS为83.6%、83.9%和136.4%。因高光谱辐射计可以获取每小时或者更短时间尺度的数据, 因此, 装备了高光谱辐射计的光学浮标可用于赤潮监测与预警系统。 相似文献
997.
文中设计的光学浮标采用了柱状浮体, 提出了自由旋转的马鞍链结构。理论计算结果表明, 该光学浮标一是初稳性高度大, 二是光学浮标重心位于浮心之下, 浮标的摇摆角较小, 抗倾斜及倾覆能力强。海上试验结果表 明, 对于风力7节、浪高3—4m以下的海况, 浮标倾角≤5°的次数占总采样次数的 54%, 浮标倾角≤10°的次数占总采样次数的83%, 浮标性能较好地满足了水下光辐射测量的技术要求。为减小阴影效应带来的光辐射测量误差, 文中采用了两种解决方法: 一是伸臂结构解决浮标体阴影的影响, 当太阳天顶角为0°时, 在近岸或者清洁水体中浮标体阴影引起的向上辐亮度测量误差分别不大于4% 和1%; 二是光纤光谱仪测量技术减少仪器自阴影的影响, 设计的光谱辐照度和辐亮度光学探头直径均为0.042m, 当水体光束衰减系数为0.12m-1, 太阳天顶角为10°时, 自阴影引起的向上辐亮度测量误差仅为1.5%。 相似文献
998.
保护窗口是深海视频采集系统的关键组件。为提高深海视频采集系统的整体性能,保障深海资源的勘探和开发利用,文章通过力学分析、理论对比和打压试验等过程,对保护窗口进行设计和优化。研究结果表明:球扇形窗口更适合全海深均匀高压环境;与主流窗口材料蓝宝石相比,我国自主研制的YAG透明陶瓷在性能和成本上具有优势;以第四强度理论作为充分准则进行设计,以第一和第二强度理论作为必要条件进行校验,结合有限元力学分析结果,外径为96mm的半球形保护窗口的最优内径为76mm;对采用该内径尺寸透明陶瓷保护窗口的深海视频采集系统进行全海深压强水下打压试验,有力证实相关理论和设计思想的合理性和可靠性。 相似文献
999.
刘勤 《广东海洋大学学报》2009,29(5):10-13
海洋社会学作为新兴的社会学分支学科发展至今已逾十年,该学科呈现出发展方向趋向以内为主的走出边缘,回归主流;方法论趋向走出应然,回归实证;操作途径趋向走出文本,回归田野。 相似文献
1000.
《中国海洋工程》2014,(5)
正Being an international journal.China Ocean Engineering takes as its prime function the integration of new research concepts,equipment,technology,materials and structures and other scientific advances within the field of estuarial,coastal,offshore,and deepwater engineering with particular reference to developments.The Journal is concerned with all engineering 相似文献