全文获取类型
收费全文 | 4433篇 |
免费 | 113篇 |
国内免费 | 56篇 |
专业分类
测绘学 | 152篇 |
大气科学 | 376篇 |
地球物理 | 970篇 |
地质学 | 1626篇 |
海洋学 | 412篇 |
天文学 | 794篇 |
综合类 | 13篇 |
自然地理 | 259篇 |
出版年
2023年 | 12篇 |
2022年 | 39篇 |
2021年 | 52篇 |
2020年 | 61篇 |
2019年 | 56篇 |
2018年 | 131篇 |
2017年 | 130篇 |
2016年 | 163篇 |
2015年 | 100篇 |
2014年 | 145篇 |
2013年 | 214篇 |
2012年 | 184篇 |
2011年 | 261篇 |
2010年 | 197篇 |
2009年 | 275篇 |
2008年 | 223篇 |
2007年 | 184篇 |
2006年 | 204篇 |
2005年 | 207篇 |
2004年 | 289篇 |
2003年 | 222篇 |
2002年 | 146篇 |
2001年 | 104篇 |
2000年 | 112篇 |
1999年 | 83篇 |
1998年 | 92篇 |
1997年 | 61篇 |
1996年 | 33篇 |
1995年 | 38篇 |
1994年 | 40篇 |
1993年 | 34篇 |
1992年 | 41篇 |
1991年 | 23篇 |
1990年 | 35篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 16篇 |
1984年 | 21篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 22篇 |
1978年 | 22篇 |
1977年 | 21篇 |
1976年 | 15篇 |
1975年 | 19篇 |
1974年 | 16篇 |
1973年 | 15篇 |
1971年 | 13篇 |
排序方式: 共有4602条查询结果,搜索用时 15 毫秒
101.
102.
Osborne Alfred R. Resio Donald T. Costa Andrea Ponce de León Sonia Chirivì Elisabetta 《Ocean Dynamics》2019,69(2):187-219
Ocean Dynamics - We analyze surface wave data taken in Currituck Sound, North Carolina, during a storm on 4 February 2002. Our focus is on the application of nonlinear Fourier analysis (NLFA)... 相似文献
103.
Stefano De Santis Paolo Casadei Gerardo De Canio Gianmarco de Felice Marialaura Malena Marialuisa Mongelli Ivan Roselli 《地震工程与结构动力学》2016,45(2):229-251
An innovative solution for the seismic protection of existing masonry structures is proposed and investigated through shake table tests on a natural scale wall assemblage. After a former test series carried out without reinforcement, the specimen was retrofitted using Steel Reinforced Grout. The strengthening system comprises horizontal strips of ultra‐high strength steel cords, externally bonded to the masonry with hydraulic lime mortar, and connectors to transversal walls, applied within the thickness of the plaster layer. In order to assess the seismic performance of the retrofitted wall, natural accelerograms were applied with increasing intensity up to failure. Test results provide a deep understanding of the effectiveness of mortar‐based composites for improving the out‐of‐plane seismic capacity of masonry walls, in comparison with traditional reinforcements with steel tie‐bars. The structural implications of the proposed solution in terms of dynamic properties and damage development under earthquake loads are also discussed.Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
104.
105.
Melchor Gonzlez-Dvila J. Magdalena Santana-Casiano Demetrio de Armas Jos Escnez Miguel Suarez-Tangil 《Marine Chemistry》2006,99(1-4):177
Measurements of surface partial pressure of CO2 and water column alkalinity, pHT, nutrients, oxygen, fluorescence and hydrography were carried out, south of the Canary Islands during September 1998. Cyclonic and anticyclonic eddies were alternatively observed from the northwestern area to the central area of the Canary Islands. Nutrient pumping and vertical uplifting of the deep chlorophyll maximum by cyclonic eddies were also ascertained by upward displacement of dissolved inorganic carbon. A model was applied to determine the net inorganic carbon balance in the cyclonic eddy. The fluxes were determined considering both the diffusive and convective contributions from the upward pumping and the corresponding horizontal transport of water outside the area. An increase in the total inorganic carbon concentration in the upper layers inside the eddy field of 133 mmol C m− 2 d− 1 was determined. The upward flux of inorganic carbon decreased the effect of the increased primary production on the carbon dioxide chemistry. The reduced fCO2 inside the cyclonic eddy, 15 μatm lower than that observed in non-affected surface water, was explained by thermodynamic aspects, biological activity, eddy upward pumping and diffusion and air–sea water exchange effects. 相似文献
106.
With the development of high-resolution multibeam echosounder systems (MBES) for surveying shallow-water areas a new tool is available to monitor rapid changes in seabed morphology as, e.g., caused by the dumping of dredge spoil in coastal waters. In this study, four data sets of repeated bathymetric surveys with a MBES were processed and analyzed. The data were collected in a 1.94-km2 dumping site in the outer Weser Estuary (German Bight). Between June and December 1998, 2.6 million m3 of dredged sediment were deposited there. The bathymetric maps generated in the course of this study reveal features such as subaqueous dunes, scour holes, and mounds of dumped dredge spoil. The mean water depth decreased by about 1 m during the dumping period. Furthermore, difference grids showing changes in sediment volume allowed a calculation of the sediment budget for the monitored area. After a time period of only 5 months, 0.5 million m3 of the originally dumped 2.6 million m3 of dredge spoil had already been removed from the dumping site. 相似文献
107.
108.
Annual Cycle of Zooplankton Biomass, Abundance and Species Composition in the Neritic Area of the Balearic Sea, Western Mediterranean 总被引:7,自引:0,他引:7
Abstract. Seasonal changes in zooplankton biomass, abundance and species composition were studied at a neritic station in the Balearic Sea between April 1993 and May 1994. Sampling was carried out every 10 days in a zone influenced by the main current circulating through the Mallorca channel. Three main peaks of zooplankton biomass and abundance were observed: (1) at the beginning of summer when the thermocline developed, (2) in autumn when the thermocline broke down, and (3) in early spring. The smaller zooplankton fraction (100–250 μm) comprised on average 32 % of the total biomass and 73 % of total abundance. Copepods were the predominant group (64 % of the total abundance) with Clausocalanus, Oithona and Paracalanus being the most abundant genera. Paracalanus parvus, Clausocalanus furcatus, Acartia clausi, Oithona plumifera, Temora stylifera, Centropages typicus and Oncaea mediterranea were found to be the most important species in the area. Other abundant groups were cladocerans (15 %) and meroplankton larvae (12 %), both of which were particularly numerous during the stratified period. The copepod community was characterized by the above‐cited perennial species, which were abundant during the cycle studied. However, the influence of the hydrological conditions of the Balearic Sea, such as the Atlantic water influx and the physical structure of the water column (stratification and mixing), promoted the observed variability in zooplankton as well as the appearance of characteristic species during the annual cycle. 相似文献
109.
This paper focuses on changing trust relationships among fishermen following new governance arrangements. The previous ‘thick’ trust relationships that characterized the Dutch fisheries industry under a neo-corporatist arrangement had resulted in an isolation of local fishermen groups vis-à-vis outsiders. However, under new governance arrangements, in particular the so-called Study Groups, these trust relationships are changing. The establishment of Study Groups, where fishermen from different localities have to cooperate on sustainability innovations in order to receive subsidies, lead to more diversity within the industry, more collaborations across localities and new forms of ‘thin’ trust. As such, these Study Groups can be understood as successful experiments in further opening up of the fisheries community. 相似文献
110.
Long-term considerations of repeated and increasing sand extraction on the Netherlands Continental Shelf (North Sea) may lead to the creation of a mega-scale extraction trench in front of the Dutch coast (length hundreds of km, width over 10 km, depth several m). We investigate the impact of such a huge topographic intervention on tidal dynamics, which is a key aspect in hydrodynamics, and indirectly also affecting morphodynamics and ecology. 相似文献