全文获取类型
收费全文 | 831篇 |
免费 | 73篇 |
国内免费 | 221篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 104篇 |
地球物理 | 404篇 |
地质学 | 334篇 |
海洋学 | 131篇 |
天文学 | 35篇 |
综合类 | 38篇 |
自然地理 | 62篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 15篇 |
2017年 | 4篇 |
2016年 | 13篇 |
2015年 | 20篇 |
2014年 | 37篇 |
2013年 | 30篇 |
2012年 | 49篇 |
2011年 | 53篇 |
2010年 | 18篇 |
2009年 | 24篇 |
2008年 | 52篇 |
2007年 | 41篇 |
2006年 | 42篇 |
2005年 | 51篇 |
2004年 | 56篇 |
2003年 | 43篇 |
2002年 | 36篇 |
2001年 | 38篇 |
2000年 | 40篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 9篇 |
1995年 | 17篇 |
1994年 | 24篇 |
1993年 | 28篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 30篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 27篇 |
1984年 | 16篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1978年 | 4篇 |
1973年 | 3篇 |
1940年 | 4篇 |
1938年 | 2篇 |
1937年 | 3篇 |
1925年 | 2篇 |
排序方式: 共有1125条查询结果,搜索用时 156 毫秒
101.
对西澳大利亚东部金矿田省太古宙花岗岩—绿岩地壳发展的几个不同模式作了系统的阐述。由于缺少以下几个方面资料,引起了许多争论: 1)绿岩和花岗岩的连续出露。 2)具有充分的区域的综合性多学科研究。 3)在对岩套研究中,用几种同位素方法进行补充的地质年代和岩石成因方面的研究。 4)标准地区的详细地球物理资料。 相似文献
102.
103.
积温作为农作物对热量需要的指标,得到了广泛应用,但因不稳定,目前仍有争论。为检查积温不稳定的原因,以春小麦列宁格勒卡品种()为研究对象,作了以下试验: 相似文献
104.
105.
Mountain Water Tower and Ecological Risk Estimation of the Mesta-Nestos Transboundary River Basin (Bulgaria-Greece) 总被引:2,自引:1,他引:1
K. Grunewald J. Scheithauer J.-M. Monger N. Nikolova 《山地科学学报》2007,4(3):209-220
The Mesta-Nestos river basin in Bulgaria and Greece is a case study for transboundary decision-making support in south-eastern Europe and a show-case for the development of methodologies and information-gathering for the integrated regional planning of water resources. Land-use conflicts in this water-scarce region cover a wide spectrum of activities like agricultural irrigation,drinking water production,diversions for industrial water,and risk of pollution from mining,to name a few examples. Measurements of the water quality were carried out in the upper basin. Results will be illustrated by the example of the environmental situation in the alpine region of the Pirin National Park as well as in the Razlog Basin with a stronger anthropogenic impact and pollution around a former uranium mine near the village of Ele?nica. The social and economic development of this transboundary region is a recently established priority for the future. It will mean an increase in water usage and more stress for the water resources if regional impacts of global climate change are verified. Problem-focused management of the catchment area as a whole on the basis of proved geo-data sets is needed for the future. 相似文献
106.
ZHAO Xiaoxia Michael G FOX David C. LASENBY Alexis C. ARMIT Dolly N. KOTHAWALA 《中国海洋湖沼学报》2007,25(2):215-220
The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas. 相似文献
107.
TOKPOHOZIN N. B. KOUNOUHEWA B. AVOSSEVOU G. Y. H. HOUEKPOHEHAM A. AWANOU C. N. 《海洋学报(英文版)》2015,34(2):137-142
Under the action of marine currents, non-cohesive sediments evolve by bed-load, by saltation or suspension depending on their granulometry. Several authors have considered that the movement of sediment... 相似文献
108.
The diel vertical migration(DVM) of zooplankton and the influence of upwelling on zooplankton biomass were examined using water column data of current velocity and mean volume backscattering strength(MVBS)collected by moored acoustic Doppler current profilers(ADCPs) deployed in the southeastern Chukchi Sea during the 5th Chinese National Arctic Research Expedition(CHINARE) in summer 2012, combined with the satellite observational data such as sea surface temperature(SST), wind, and chlorophyll a(Chl a). Hourly acoustic data were continuously collected for 49-d in the mooring site. Spectral analysis indicated that there were different migrating patterns of zooplankton, even though precisely classifying the zooplankton taxa was not available. The prevailing 24-h cycle corresponded to the normal DVM with zooplankton swimming upwards at sunrise and returning to deep waters at sunset. There was a clear DVM in the upper 17 m of the water column during the period with distinct day-night cycles, and no active DVM throughout the water column when the sun above the horizon(polar day), suggesting that light intensity was the trigger for DVM. Also there was a second migrating pattern with 12-h cycle. The upwelling event occurring in the northwest of Alaskan coastal area had important influence on zooplankton biomass at the mooring site. During the upwelling, the SST close to the mooring site dropped significantly from maximal 6.35°C to minimal 1.31°C within five days. Simultaneously, there was a rapid increase in the MVBS and Chl a level, suggesting the aggregation of zooplankton related to upwelling. 相似文献
109.
Mesoscale surface circulation and variability of Southern Indian Ocean derived by combining satellite altimetry and drifter observations 总被引:1,自引:1,他引:0
BENNY N. Peter SHENBAKAVALLI Ranjan MAZLAN Hashim MOHD Nadzri Re MOHD Razali Mahmud 《海洋学报(英文版)》2015,34(9):12-22
High resoultion Eulerian mean velocity field has been derived by combining the satellite tracked surface drifter data with satellite altimetry and ocean surface winds. The drifter data used in this study includes Argos and surface drifter data from Global Drifter Program. Maps of Sea Level Anomaly(MSLA) weekly files with a resolution of(1/3)° in both Latitude and Longitude for the period 1993–2012 have been used. The Ekman current is computed using ocean surface mean wind fields from scatterometers onboard ERS 1/2,Quikscat and ASCAT. The derived mean velocity field exhibits the broad flow of Antarctic Circumpolar Current with speeds up to 0.6 m/s.Anomalous field is quite significant in the western part between 20° and 40°E and in the eastern part between 80°E and 100°E with velocity anomaly up to 0.3 m/s. The estimated mean flow pattern well agrees with the dynamic topography derived from in-situ observations. Also,the derived velocity field is consistent with the in-situ ADCP current measurements. Eddy kinetic energy illustrates an increasing trend during 1993–2008 and is in phase coherence with the Southern Annular Mode by three month lag. Periodic modulations are found in the eddy kinetic energy due the low frequency Antarctic Circumpolar Wave propagation. 相似文献
110.
Occurrence and fate of polycyclic aromatic hydrocarbons in the coastal surface microlayer 总被引:2,自引:0,他引:2
Polycyclic aromatic hydrocarbons (PAHs) were measured in the coastal sea surface microlayer (SML), the sub-surface waters (SSW) and the overlying atmosphere in order to investigate the influence of the SML on contaminant enrichment and air-sea exchange. Samples were collected at two contrasting locations of the NW Mediterranean, one urban influenced (off Barcelona, Spain) and another comparatively clean (off Banyuls-sur-Mer, France). Statistical data analysis confirmed the accumulation of PAHs in the SML with respect to the SSW (20.3+/-9.1 vs. 13.1+/-10.0 ng L(-1) in the dissolved phase; 709+/-207 vs. 158+/-111 ng g(-1) in the particulate phase). This accumulation was higher at the contaminated location (Barcelona station) compared with the more pristine one, with PAH enrichments 1.5 and 4.5 times higher for the dissolved and particulate phases, respectively, indicating that the enrichment of PAHs in the SML is dominated by particle transport processes. 相似文献