全文获取类型
收费全文 | 57234篇 |
免费 | 21816篇 |
国内免费 | 46215篇 |
专业分类
测绘学 | 3693篇 |
大气科学 | 25218篇 |
地球物理 | 17929篇 |
地质学 | 46532篇 |
海洋学 | 17966篇 |
天文学 | 2114篇 |
综合类 | 6918篇 |
自然地理 | 4895篇 |
出版年
2024年 | 241篇 |
2023年 | 756篇 |
2022年 | 1555篇 |
2021年 | 2027篇 |
2020年 | 2974篇 |
2019年 | 6317篇 |
2018年 | 6805篇 |
2017年 | 6446篇 |
2016年 | 6689篇 |
2015年 | 5682篇 |
2014年 | 5589篇 |
2013年 | 5974篇 |
2012年 | 5633篇 |
2011年 | 5461篇 |
2010年 | 5375篇 |
2009年 | 4789篇 |
2008年 | 3889篇 |
2007年 | 3926篇 |
2006年 | 3479篇 |
2005年 | 3252篇 |
2004年 | 3342篇 |
2003年 | 3057篇 |
2002年 | 2798篇 |
2001年 | 2598篇 |
2000年 | 2406篇 |
1999年 | 2829篇 |
1998年 | 2640篇 |
1997年 | 2739篇 |
1996年 | 2168篇 |
1995年 | 2113篇 |
1994年 | 1869篇 |
1993年 | 1736篇 |
1992年 | 1427篇 |
1991年 | 1079篇 |
1990年 | 927篇 |
1989年 | 812篇 |
1988年 | 712篇 |
1987年 | 544篇 |
1986年 | 436篇 |
1985年 | 329篇 |
1984年 | 344篇 |
1983年 | 211篇 |
1982年 | 254篇 |
1981年 | 177篇 |
1980年 | 142篇 |
1979年 | 125篇 |
1978年 | 61篇 |
1977年 | 50篇 |
1972年 | 45篇 |
1971年 | 53篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
1 Introduction IL-1βis a pleiotropic proinlammatory cytokine with a wide spectrum of inflammatory, metabolic, hematopoietic and immunological activities and is re- sponsible for the symptoms of sickness during the host response to infection (Dinarello, 1… 相似文献
973.
974.
In this paper, the theoretical analysis and experimental studies are employed to investigate the reflection characteris-tics of partial standing waves caused by wave overtopping and sloping top of structures. Based on the principle of conser-vation of wave energy flux, the third-order Stokes wave theory is used to formulate the reflection coefficient at wave overtopping; the calculation results are regressed into an applied expression. A series of experiments of wave reflection for a vertical-wall structure with chamfered and overhanging upper sections are carried out to investigate the influence of top slope on wave reflection. The regularity of variation of wave reflection in this case is analysed based on the experimental results. 相似文献
975.
INTRODUCTIONTheDenglouCape ,inthesouthwestoftheLeizhouPeninsula ,isatthenorthmarginoftropicalzone .SeveralresearchesandcartographiesoftheregionalgeomorphologyandQuater narygeology ,whichwerecarriedoutinthepast,allincludethisarea (MGL ,SCSIO ,CAS ,1 978;GPCSGRCZT… 相似文献
976.
977.
福建红树林区海藻的分布及季节变化 总被引:5,自引:0,他引:5
主要研究了福建省3个红树林区的海藻不同滩面分布的情况、海藻种类组成的季节变化以及不同季节的海藻群落类型.研究表明:(1)福建红树林区海藻在不同滩面分布表现出,红藻较喜荫蔽潮湿的环境,而绿藻适生在光照条件较好生境.(2)由福建红树林区各门海藻种类组成的季节变化来看,蓝藻种数在一年四季没有明显变化规律,红藻四季种数变化幅度不大,而绿藻在不同季节种数有明显变化,春季种数最多,进入夏季后种数逐渐减少,到秋、冬季后种数又开始上升,到第2年春季又达到最多.(3)不同季节福建红树林区海藻群落类型中,优势种主要是红藻,以及一些绿藻. 相似文献
978.
Wang Tan K. McIntosh Kirk Nakamura Yosio Liu Char-Shine Chen How-Wei 《Marine Geophysical Researches》2001,22(4):265-287
A wide-angle seismic survey, combining ocean-bottom seismometers (OBS) and multi-channel seismic (MCS) profiling, was implemented
in the southwestern Ryukyu subduction zone during August and September 1995. In this paper, we present the data analysis of
eight OBSs and the corresponding MCS line along profile EW9509-1 from this experiment. Seismic data modeling includes identification
of refracted and reflected arrivals, initial model building from velocity analysis of the MCS data, and simultaneous and layer-stripping
inversions of the OBS and MCS arrivals. The velocity-interface structure constructed along profile EW9509-1 shows that the
northward subduction of the Philippine Sea Plate has resulted in a northward thickening of the sediments of the Ryukyu Trench
and the Yaeyama accretionary wedge north of the trench. The boundary between the subducting oceanic crust and the overriding
continental crust (represented by a velocity contour of 6.75 km/s) and a sudden increase of the subducting angle (from 5 degrees
to 25 degrees) are well imaged below the Nanao Basin. Furthermore, velocity undulation and interface variation are found within
the upper crust of the Ryukyu Arc. Therefore, the strongest compression due to subduction and a break-off of the slab may
have occurred and induced the high seismicity in the forearc region.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
979.
- The dynamic response behaviors of upright breakwaters under broken wave impact are analysed based on the mass-damper-spring dynamic system model. The effects of the mass, damping, stiffness, natural period, and impulse duration (or oscillation period) on the translation, rotation, sliding force, overturning moment, and corresponding dynamic amplifying factors are studied. It is concluded that the ampli-ying factors only depend on the ratio of the system natural period to impulse duration (or oscillation period) under a certain damping ratio. Moreover, the equivalent static approach to breakwater design is also discussed. 相似文献
980.