首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   184篇
  免费   35篇
  国内免费   43篇
测绘学   20篇
大气科学   13篇
地球物理   43篇
地质学   84篇
海洋学   34篇
天文学   23篇
综合类   23篇
自然地理   22篇
  2024年   1篇
  2023年   6篇
  2022年   22篇
  2021年   24篇
  2020年   20篇
  2019年   9篇
  2018年   16篇
  2017年   16篇
  2016年   22篇
  2015年   6篇
  2014年   12篇
  2013年   15篇
  2012年   7篇
  2011年   11篇
  2010年   9篇
  2009年   6篇
  2008年   2篇
  2007年   5篇
  2006年   2篇
  2005年   2篇
  2004年   3篇
  2003年   4篇
  2002年   3篇
  2001年   5篇
  2000年   3篇
  1999年   8篇
  1998年   2篇
  1996年   1篇
  1995年   5篇
  1994年   4篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1983年   1篇
  1981年   1篇
  1978年   1篇
  1970年   1篇
  1915年   1篇
排序方式: 共有262条查询结果,搜索用时 156 毫秒
111.
Experiments were conducted to study the airborne microbial contamination generated by a wastewater treatment plant (WWTP). Aerosol samples were collected simultaneously, by sedimentation and impact methods, from the area and the surroundings of the WWTP. Total colony forming units (CFUs) of heterotrophic bacteria (HPC), as well as members of the Enterobacteriaceae, staphylococci, enterococci, actinomycetes, and microscopic fungi were determined. Bacterial (HPC) concentrations ranged between 101 and 104 CFU/m3, fungi 0 and 104 CFU/m3. Higher numbers of HPC bacteria in air samples were observed in summer, fungi in autumn. The main emission of microorganisms to atmospheric air was from the mechanical sewage treatment devices of the WWTP. The facilities of the biological sewage treatment of the plant did not generate large amounts of bioaerosols. In the air obtained from the premises of the WWTP, 25 species of the Enterobacteriaceae were isolated (Salmonella spp., Klebsiella pneumoniae, Escherichia coli). At the fence and in the surroundings only Pantoea spp. were identified. This suggests that the sewage bacteria were mainly discharged in the area of the WWTP. The presence of enteric bacteria, especially Enterobacteriaceae reflects the level of air pollution with bioaerosols from sewage and is an important factor during monitoring the quality of the air around WWTPs.  相似文献   
112.
甘肃河东地区地表湿润特征及其气候影响因子   总被引:2,自引:0,他引:2  
利用甘肃河东地区13个气象站1960-2010年的逐日气象资料,选取FAO Penman-Monteith法计算了各站的潜在蒸散量,由此得出各站点的湿润指数;然后采用线性趋势法、Morlet小波、自然正交分解(EOF)和反距离加权插值等方法,对河东地区湿润指数的时空变化特征进行分析,进而探讨对影响其变化的气象要素.结果表明:①1992年之前,甘肃河东地区地表相对湿润,1992年之后变得干旱,年地表湿润指数的年际变化率为-0.02/10a,相关系数为0.2946(P<0.05),季节上除冬季呈轻微增加外,其他各季都呈减少趋势,空间分布上表现出明显的南北差异,从南到北呈减少趋势;②年湿润指数空间异常分布主要表现为“全区一致性”和“南北反向变化”两种模态,同时也存在着19a、5a和11a左右的变化周期,并于1994年发生了由湿向干的转变;③湿润指数与降水量、相对湿度呈显著正相关,与日照时数、潜在蒸散、风速和最高气温呈显著负相关.  相似文献   
113.
Abstract

Pakistan has suffered a devastating flood disaster in 2010. In the Kabul River basin (92 605 km2), large-scale riverine and flash floods caused destructive damage with more than 1100 casualties. This study analysed rainfall–runoff and inundation in the Kabul River basin with a newly developed model that simulates the processes of rainfall–runoff and inundation simultaneously based on two-dimensional diffusion wave equations. The simulation results showed a good agreement with an inundation map produced based on MODIS for large-scale riverine flooding. In addition, the simulation identified flash flood-affected areas, which were confirmed to be severely damaged based on a housing damage distribution map. Since the model is designed to be used even immediately after a disaster, it can be a useful tool for analysing large-scale flooding and to provide supplemental information to agencies for relief operations.

Editor Z.W. Kundzewicz

Citation Sayama, T., Ozawa, G., Kawakami, T., Nabesaka, S. and Fukami, K., 2012. Rainfall–runoff–inundation analysis of the 2010 Pakistan flood in the Kabul River basin. Hydrological Sciences Journal, 57 (2), 298–312.  相似文献   
114.
跨国公司在华R&D机构的空间集聚研究   总被引:4,自引:0,他引:4  
跨国公司RD全球化的实质是RD资源的全球配置与RD功能的空间扩张,它有着深刻的地理意义与充分的空间表现,因此引起了地理学家的热烈讨论。通过全国范围内外资RD活动的统计调查及对近百家机构的深度访谈,在对已有的研究视角进行分析归类的基础上,分别以区域、省份及城市为基地地域单元,系统考察了外资在华RD的空间分布及其变动趋势。发现我国外资RD机构的空间分布极不均衡,地区差距非常大,形成了三大明显的地理集中区,且高度聚集在少数全国性或区域性经济中心城市。行业上的空间差异也十分显著,不同行业的外资RD区位重点不同,不同母国外资RD的行业空间分布也存在差异。其空间变动则呈现出区域范围不断拓展、核心区域向长三角地区集中以及"R"高度集中而"D"趋向分散的态势。  相似文献   
115.
This paper presents a combined validation method of radar-sensed rainfall, using rain gauge data and hydrologic closure, with an application to the Rio Escondido basin (North-East of Mexico). The space–time scaling behavior of rainfall between rain gauge and radar scales is compared with the intrinsic variability of rainfall, for a statistical validation of space–time variability. For hydrological validation purposes, the CEQUEAU model is used to perform rainfall-runoff routing. It provides a basin-wide water balance, to be compared with the measured water flow at the Villa de Fuentes hydrometric station, for mean-value gauging closure. A good qualitative agreement in terms of hydrograph shape and timing is obtained between the simulated and the observed water flows, and a multiplicative correction factor of an initially proposed Z–R relationship is adopted for the watershed under study, which agrees approximately with other authors’ findings about that relationship. The results are considered particularly useful as a validation-and-correction methodology of radar rainfall estimates for areas sparsely covered by rain gauges.  相似文献   
116.
介绍CCD引张线仪的测量原理、安装要求、监测成果等。在亭子口水利枢纽工程中的实测结果验证了仪器设备运行稳定,可靠性高,无漂移。  相似文献   
117.
长江口崇明东滩不同植被带沉积速率研究   总被引:1,自引:0,他引:1  
利用2007年丰水期、枯水期在崇明东滩芦苇带、藨草带和光滩采集的6根沉积物柱状样,研究了沉积物的粒度特征和过剩的210Pb和228Th及7Be活度的垂向分布特征,探讨了由陆地向海洋不同植被间的沉积物粒度变化规律。依据恒定比活度沉积速率模型,估算了不同时间尺度的崇明东滩芦苇带、藨草带和光滩的表观沉积速率。结果表明:3种核素示踪的崇明东滩的表观沉积速率都随潮滩植被的不同从陆到海方向逐渐降低,同时依过剩的210Pb和228Th,7Be的次序而增大。由过剩的210Pb和228Th计算的夏季沉积速率比冬季的稍高,而由7Be计算的夏季表观沉积速率则明显高于冬季的。结合沉积物粒度的时空分布和这些核素的大气通量,对利用这些核素测定潮滩沉积速率的影响因素进行了探讨。  相似文献   
118.
本文阐述了新一代中国数字地震台网(NCDSN)产出的地震观测数据如何在中国数字地震台网数据管理中心(CDSN DMC)进行光盘数据的安全备份。对数字地震观测数据的重要性和地震数据备份存储的特殊性;刻录盘的选择,备份数据的容量、速度的选取以及刻录盘的标识、存储等方面进行了论述。  相似文献   
119.
Uptake and biological effects of synthetic glucocorticoids (GCs) were analyzed using common carp (Cyprinus carpio). Fish were exposed to clobetasol propionate (CP) or clobetasone butyrate (CB) individually or in mixture at 1 μg L−1 for 21 days. Bioconcentration factor (BCF) of CB was calculated as 100, and BCF of CP was less than 16. No effects were found in fish erythrocyte and leukocyte numbers and serum glucose levels after exposure to the selected GCs. On the other hand, serum concentrations of free amino acids significantly increased in GC-exposed groups. Thus, exposures to synthetic GCs at relatively low concentrations seemed to cause enhancement of protein degradation and subsequent increase of serum free amino acids without a corresponding increase in serum glucose levels, an effect which might be related to partial induction of gluconeogenesis by GC.  相似文献   
120.
“2002.3”华北地区强沙尘暴天气的螺旋度分析   总被引:1,自引:1,他引:0  
利用MM5非静力中尺度模式和螺旋度计算结果,对2002年3月18-22日华北地区发生的一次强沙尘暴过程进行了分析研究,重点分析了北京及周边地区水平与垂直方向螺旋度和完全螺旋度的结构变化及演变特征,结果表明:螺旋度的演变与强沙尘暴天气的发生、发展有较好的对应关系,将中尺度模式和螺旋度计算结合起来可以有效提高沙尘暴天气的预报准确度。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号