全文获取类型
收费全文 | 7372篇 |
免费 | 658篇 |
国内免费 | 183篇 |
专业分类
测绘学 | 282篇 |
大气科学 | 743篇 |
地球物理 | 2583篇 |
地质学 | 2846篇 |
海洋学 | 529篇 |
天文学 | 643篇 |
综合类 | 198篇 |
自然地理 | 389篇 |
出版年
2022年 | 11篇 |
2021年 | 57篇 |
2020年 | 41篇 |
2019年 | 43篇 |
2018年 | 515篇 |
2017年 | 450篇 |
2016年 | 387篇 |
2015年 | 234篇 |
2014年 | 220篇 |
2013年 | 274篇 |
2012年 | 769篇 |
2011年 | 537篇 |
2010年 | 225篇 |
2009年 | 274篇 |
2008年 | 231篇 |
2007年 | 227篇 |
2006年 | 190篇 |
2005年 | 905篇 |
2004年 | 955篇 |
2003年 | 710篇 |
2002年 | 202篇 |
2001年 | 106篇 |
2000年 | 80篇 |
1999年 | 48篇 |
1998年 | 33篇 |
1997年 | 49篇 |
1996年 | 30篇 |
1995年 | 17篇 |
1994年 | 26篇 |
1993年 | 17篇 |
1992年 | 14篇 |
1991年 | 18篇 |
1990年 | 24篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1980年 | 9篇 |
1978年 | 10篇 |
1976年 | 8篇 |
1975年 | 15篇 |
1974年 | 14篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1970年 | 7篇 |
1965年 | 7篇 |
排序方式: 共有8213条查询结果,搜索用时 187 毫秒
991.
992.
PAR E.GHERZI 《地质学报》1925,4(2):81-86
Hest bien clair que toute reponse a cette question, sera du plus haut interet pour les geologues de la Chine, vu que les resultats de la geodesie semblent bien indiquer que la croute terrestre est divisee en plusieurs blocs independants, juxtaposes et equilibres isostatiquement. 相似文献
993.
Mr.T.F.Hou,geologist of the National Geological Survey of Chinabrought back in 1931 from Liaoning province,a specimen of subbituminous coalin which are included patches or aggregates of small oolites.This interestingspecimen was given to the writer for microscopical investigation.Both polished 相似文献
994.
995.
David Serrano Giné Joan Jurado Rota María Yolanda Pérez Albert Carla Bonfill Cerveró 《The Professional geographer》2018,70(3):412-422
The aim of this article is to introduce the Beach Crowding Index (BCI), a procedure to assess the social carrying capacity of vulnerable beaches. The study uses the people at one time (PAOT) approach and data gathered weekly throughout the bathing season regarding the number of beachgoers in 100 m2 cells of the beach to assess how many beachgoers it can comfortably hold. The procedure is based on fieldwork, interviews with beachgoers, and geographic information system (GIS) analysis and has been tested on four beaches in protected areas on the Spanish Mediterranean coast. On a scale from 0 to 4, minimum scores throughout the bathing season are 0.7 and maximum 3.7, although results showed wide variation between the beaches, the section of the beach, and the time of day. This study suggests that determining the location of beachgoers and collecting a long-term series of data is fundamental to assessing social carrying capacity and that the BCI procedure can be used for a large number of applications. 相似文献
996.
Gregor Muri Branko Čermelj Radojko Jaćimović Tina Ravnikar Andrej Šmuc Janja Turšič Polona Vreča 《Journal of Paleolimnology》2018,59(4):411-426
Increased eutrophication was recently observed in the 5th (5J) and 6th (6J) Triglav Lakes, two remote Slovenian mountain lakes. Sediment phosphorus (P) pools were analysed and potential external P sources affecting the lakes (atmospheric deposition, terrestrial export and nearby hut) evaluated, to assess the effects of internal and external changes on the lakes. A sequential extraction procedure was used to quantify five P fractions from the sediments: adsorbed (NH4Cl–P), redox-sensitive (BD–P), aluminium- (NaOH–P) and calcium- (HCl–P) bound, and refractory organic (Res–P) P. Total phosphorus (TP) contents in surface sediment of 5J and 6J were 1430 and 641 µg P g?1 dry weight sediment (dw), respectively. TP varied with depth in 5J sediments, but displayed no discernible pattern, whereas it decreased steadily downcore in 6J. Contents of all P forms were distinctly higher in 5J than 6J, but their rank order and relative abundances were similar in the two lakes. Res–P was the most abundant P fraction, followed by HCl–P. Together, the two P forms accounted for nearly 80 and 90% of TP in 5J and 6J sediments, respectively. BD–P and NaOH–P were less abundant, with each fraction accounting for 3 to 9% of TP, whereas NH4Cl–P was least abundant. Atmospheric deposition and terrestrial export were substantial sources of P for the lakes. Delivery of the former was estimated to be at least 7.5 mg P m?2 yr?1 and the latter around 20 mg P m?2 yr?1. We concluded that P was not retained in the catchment effectively, likely because of only slightly acidic soil pH (5.9), relatively low aluminium content and high organic matter content (53%) in soils, resulting in higher vulnerability of the studied lakes to eutrophication. The mountain hut could also be a significant source of P for the lakes. Each year, it could potentially contribute ~12 kg of soluble P to the environment, but the true impact of the hut on lake trophic status remains unclear. 相似文献
997.
Ferenc?ácsEmail authorView authors OrcID profile Dominika?Takács Hajnalka?Breuer Nóra?Skarbit 《Theoretical and Applied Climatology》2018,131(3-4):899-926
We present a 1-km2 gridded German dataset of hourly surface climate variables covering the period 1995 to 2012. The dataset comprises 12 variables including temperature, dew point, cloud cover, wind speed and direction, global and direct shortwave radiation, down- and up-welling longwave radiation, sea level pressure, relative humidity and vapour pressure. This dataset was constructed statistically from station data, satellite observations and model data. It is outstanding in terms of spatial and temporal resolution and in the number of climate variables. For each variable, we employed the most suitable gridding method and combined the best of several information sources, including station records, satellite-derived data and data from a regional climate model. A module to estimate urban heat island intensity was integrated for air and dew point temperature. Owing to the low density of available synop stations, the gridded dataset does not capture all variations that may occur at a resolution of 1 km2. This applies to areas of complex terrain (all the variables), and in particular to wind speed and the radiation parameters. To achieve maximum precision, we used all observational information when it was available. This, however, leads to inhomogeneities in station network density and affects the long-term consistency of the dataset. A first climate analysis for Germany was conducted. The Rhine River Valley, for example, exhibited more than 100 summer days in 2003, whereas in 1996, the number was low everywhere in Germany. The dataset is useful for applications in various climate-related studies, hazard management and for solar or wind energy applications and it is available via doi: 10.5676/DWD_CDC/TRY_Basis_v001. 相似文献
998.
Dragana?Vujovi?Email author Nedeljko?Todorovi? 《Theoretical and Applied Climatology》2018,131(3-4):889-898
Urban/rural fog appearance during the last 27 years in the Belgrade region is analysed using hourly meteorological records from two meteorological stations: an urban station at Belgrade-Vra?ar (BV) and a rural station at Belgrade-Airport (BA). The effects of urban development on fog formation are discussed through analysis of fog frequency trends and comparison with a number of meteorological parameters. The mean annual and the mean annual minimum temperatures were greater at the urban BV station than at the rural BA station. The mean monthly relative humidity and the mean monthly water vapour pressure were greater at the rural than urban station. During the period of research (1988–2014), BA experiences 425 more days with fog than BV, which means that BV experiences fog for 62.68% of foggy days at BA. Trends in the number of days with fog were statistically non-significant. We analysed the fog occurrence during different types of weather. Fog in urban BV occurred more frequently during cyclonal circulation (in 52.75% of cases). In rural BA, the trend was the opposite and fog appeared more frequently during anticyclonic circulation (in 53.58% of cases). Fog at BV occurred most frequently in stable anticyclonic weather with light wind, when a temperature inversion existed (21.86% of cases). Most frequently, fog at BA occurred in the morning and only lasted a short time, followed by clearer skies during the anticyclonic warm and dry weather (22.55% of cases). 相似文献
999.
Yawar?HussainEmail author Frédéric?Satgé Muhammad?Babar?Hussain Hernan?Martinez-Carvajal Marie-Paule?Bonnet Martin?Cárdenas-Soto Henrique?Llacer?Roig Gulraiz?Akhter 《Theoretical and Applied Climatology》2018,131(3-4):1119-1132
The present study aims at the assessment of six satellite rainfall estimates (SREs) in Pakistan. For each assessed products, both real-time (RT) and post adjusted (Adj) versions are considered to highlight their potential benefits in the rainfall estimation at annual, monthly, and daily temporal scales. Three geomorphological climatic zones, i.e., plain, mountainous, and glacial are taken under considerations for the determination of relative potentials of these SREs over Pakistan at global and regional scales. All SREs, in general, have well captured the annual north-south rainfall decreasing patterns and rainfall amounts over the typical arid regions of the country. Regarding the zonal approach, the performance of all SREs has remained good over mountainous region comparative to arid regions. This poor performance in accurate rainfall estimation of all the six SREs over arid regions has made their use questionable in these regions. Over glacier region, all SREs have highly overestimated the rainfall. One possible cause of this overestimation may be due to the low surface temperature and radiation absorption over snow and ice cover, resulting in their misidentification with rainy clouds as daily false alarm ratio has increased from mountainous to glacial regions. Among RT products, CMORPH-RT is the most biased product. The Bias was almost removed on CMORPH-Adj thanks to the gauge adjustment. On a general way, all Adj versions outperformed their respective RT versions at all considered temporal scales and have confirmed the positive effects of gauge adjustment. CMORPH-Adj and TMPA-Adj have shown the best agreement with in situ data in terms of Bias, RMSE, and CC over the entire study area. 相似文献
1000.
Johanna?Engstr?mEmail authorView authors OrcID profile Peter?Waylen 《Theoretical and Applied Climatology》2018,131(3-4):1133-1146
The hydroclimatology of the southeastern USA (AL, GA, NC, SC, and TN) is analyzed from a holistic perspective, including multiple climate drivers. Monthly precipitation modeled by the PRISM group and runoff data (1952–2011) from 18 basins are analyzed using a single-field based principal component’s analysis. Results indicate that the Atlantic Multidecadal Oscillation and El Niño-Southern Oscillation are the main atmospheric drivers of hydroclimate variability in the region, sometimes operating at several months’ lag. Their influence is the strongest in the fall through spring, which corresponds with the dry season in the southern parts of the study area thereby increasing pressure on already limited water resources. The Arctic Oscillation, North Atlantic Oscillation, and Pacific-North American patterns vary on shorter-term bases, and also show a significant, but temporally more sporadic influence. Insight is also brought to the ongoing discussion, confirming the disassociation of the Arctic and North Atlantic Oscillation. Findings can be used in water resources forecasting, giving an indication of expected water volumes several months ahead. 相似文献