全文获取类型
收费全文 | 580篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 59篇 |
大气科学 | 35篇 |
地球物理 | 69篇 |
地质学 | 206篇 |
海洋学 | 18篇 |
天文学 | 187篇 |
综合类 | 2篇 |
自然地理 | 19篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 36篇 |
2017年 | 26篇 |
2016年 | 34篇 |
2015年 | 17篇 |
2014年 | 29篇 |
2013年 | 27篇 |
2012年 | 21篇 |
2011年 | 17篇 |
2010年 | 24篇 |
2009年 | 21篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1976年 | 3篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 5篇 |
排序方式: 共有595条查询结果,搜索用时 500 毫秒
81.
Photometric observations of primary minimum inU, B, andV filters have been discussed. The amplitude of variation in all the three filters is 0
m
.66. We do not find variations in the period and its revised value is 1d.0047115. 相似文献
82.
Self-similar flows of a perfect gas behind the cylindrical shock wave propagating exponentially in an atmosphere whose density varies inversely as the fourth power of shock radius are investigated. The effects of radiation flux has also been taken into consideration. The total energy of the wave is constant. 相似文献
83.
R. K. Srivastava 《Astrophysics and Space Science》1987,132(1):125-139
The colour indices and the spectrum-luminosity classification of the eclipsing binary system IZ Persei have been presented for the first time. The colour indices of the system appear reddened. Applying the interstellar reddening corrections, the spectral-luminosity classes of the primary and the secondary components of IZ Per come out to be B2.5III-V and B5III-V, respectively. The averageB-V andU-B colour excesses come out to be 0
m
.4 and 0
m
.2, respectively. The colour indices show continuous variation throughout the cycle, and indicate the presence of intrinsic variability. Tentative analysis suggests that the primary component of IZ Per is a Beta Canis Majoris-type variable. The possibility of a shell has also been discussed. 相似文献
84.
Photometric observations of CU Eridani, recently classified as non-variable, indicate it to be a variable star. 相似文献
85.
Srivastava R 《Ground water》2004,42(3):457-8; discussion 458
86.
Anirudh Pradhan G. S. Khadekar Deepak Srivastava 《Astrophysics and Space Science》2006,305(4):415-421
Implications of cosmological model with a cosmological term of the form , where β is a constant, are analyzed in multidimensional space time. The proper distance, the luminosity distance-redshift, the angular diameter distance-redshift, and look back time-redshift for the model are presented. It has been shown that models are found to be compatible with the present observations. This work, has thus generalized to higher dimensions the well-known result in four dimensional space time. It is found that the difference is significant at least in the principal to the anologous situation in four dimensional space time. 相似文献
87.
We carried out simultaneous measurements of drop size distribution (DSD) and stable oxygen and hydrogen isotopic compositions (??18O and ??D) of rain at the National Atmospheric Research Laboratory (NARL), Gadanki (13.5°N, 79.2°E), southern India, during September?COctober 2006, with the aim of understanding microphysical processes leading to rain formation. The MST radar at NARL was operated continuously during rain events, while rain samples were collected at very short time intervals (<1?h), to capture small changes (>0.2?? and >2??) in their ??18O and ??D. The slope of the local meteoric water line (??D?C??18O line), was 8.07?±?0.47, similar to that of global meteoric water line, confirming that the precipitation occurred under isotopic equilibrium, and was unaffected by some anomalous process; further, the evaporation of rain drops at the cloud base was insignificant. Whenever the isotopic variations were larger during a rain event (>2??) there was a significant negative correlation between the ??18O and DSD. The possible explanation is that larger drops are mostly associated with convective rather than stratiform rain, and 18O (and D) depletion in convective rain is relatively more. Bin-resolved microphysical models incorporating water isotopologues could benefit by considering drop size spectra, which could improve the match with stable isotope observations of precipitation. 相似文献
88.
Dhruvesh P Patel Mrugen B Dholakia N. Naresh Prashant K. Srivastava 《Journal of the Indian Society of Remote Sensing》2012,40(2):299-312
Geo-visualization concept has been used for positioning water harvesting structures in Varekhadi watershed consisting of 26
mini watersheds, falling in Lower Tapi Basin (LTB), Surat district, Gujarat state. For prioritization of the mini watersheds,
morphometric analysis was utilized by using the linear parameters such as bifurcation ratio (Rb), drainage density (Dd), stream frequency (Fu), texture ratio (T), length of overland flow (Lo) and the shape parameter such as form factor (Rf), shape factor (Bs), elongation ratio (Re), compactness constant (Cc) and circularity ratio (Rc). The different prioritization ranks were assigned after evaluation of the compound factor. 3 Dimensional (3D) Elevation
Model (DEM) from Shuttle Radar Topography Mission (SRTM) and DEM from topo contour were analyzed in ArcScene 9.1 and the fly
tool was utilized for the Geo-visualization of Varekhadi mini watersheds as per the priority ranks. Combining this with soil
map and slope map, the best feasibility of positioning check dams in mini-watershed no. 1, 5 and 24 has been proposed, after
validation of the sites. 相似文献
89.
Granulometric analysis of nineteen sediment samples has been carried out for their statistical and textural parameters. The
samples are collected from the northern and southern margins of Schirmacher Oasis extending below the polar ice sheet and
grading to coastal area respectively and main rocky land of Schirmacher including lakes. The analysis shows that most of the
sediments are of medium grain size and fall in poor to very poor sorted category.
An attempt has been made to interpret the depositional set-up by plotting the scatter patterns between various textural parameters,
including C-M plot and arithmetic log-probability curves. The influence of physical parameters viz. low to high velocity winds,
ice and meltwater on sediment characteristics has been discussed. 相似文献
90.
Xiushu QIE Shanfeng YUAN Zhixiong CHEN Dongfeng WANG Dongxia LIU Mengyu SUN Zhuling SUN Abhay SRIVASTAVA Hongbo ZHANG Jingyu LU Hui XIAO Yongheng BI Liang FENG Ye TIAN Yan XU Rubin JIANG Mingyuan LIU Xian XIAO Shu DUAN Debin SU Chengyun SUN Wenjing XU Yijun ZHANG Gaopeng LU Da-Lin ZHANG Yan YIN Ye YU 《中国科学:地球科学(英文版)》2021,64(1):10-26
The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model. 相似文献