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   160篇
  免费   2篇
  国内免费   6篇
测绘学   16篇
大气科学   4篇
地球物理   27篇
地质学   84篇
海洋学   8篇
天文学   14篇
综合类   4篇
自然地理   11篇
  2024年   1篇
  2023年   1篇
  2022年   3篇
  2021年   10篇
  2020年   4篇
  2019年   7篇
  2018年   12篇
  2017年   10篇
  2016年   13篇
  2015年   7篇
  2014年   16篇
  2013年   17篇
  2012年   6篇
  2011年   7篇
  2010年   5篇
  2009年   6篇
  2008年   3篇
  2007年   5篇
  2006年   7篇
  2005年   2篇
  2004年   1篇
  2003年   1篇
  2002年   1篇
  2001年   4篇
  2000年   2篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1991年   1篇
  1990年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   2篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1970年   1篇
排序方式: 共有168条查询结果,搜索用时 15 毫秒
1.
Water resources for agricultural development and landscape enhancement in Kuwait are very scarce; the quality is saline (brackish), and the soil texture is sandy, incapable of holding nutrients and moisture. Most of the rainfall in Kuwait either evaporates due to the high temperatures or percolates through the soil. The rainfall is not sufficient to recharge the underground water supply. A variety of alternative water sources have been studied, including seawater desalination and wastewater treatment. Wastewater treatment proved to be convenient due to the relatively low salinity detected in the treated water. Furthermore, the amount of wastewater is expected to increase as more residential areas are connected to the sewage system as the population increases.

The development of a greenery plan for Kuwait requires intensive water management. This goal can be achieved through manpower training in landscape development, selection of plants tolerant to arid environments, usage of appropriate irrigation and drainage systems, promotion of greenery programs within public and the governmental agencies for their direct participation in urban area beautification, and extension of wastewater treatment techniques.  相似文献   

2.
In recent decades, attaining urban sustainability is the primary goal for urban planners and decision makers. Among various aspects of urban sustainability, environmental protection such as agricultural and forest conservations is very important in tropical countries like Malaysia. In this regard, compact urban development due to high density, rural development containment is known as the most sustainable urban forms. This paper attempts to propose an integrated modeling approach to predict the future land use changes by considering city compactness paradigms. First, the cellular automata (CA) were applied for calculating land use conversion. Next, weights-of-evidence (WoE) which is based on Bayes theory was utilized to calibrate CA model and to support the transitional rule assessment. Several urban-related parameters as well as compact city indicators were utilized to estimate the future land use maps. The results showed how compact development parameters and site characteristics can be combined using the WoE model to predict the probability of land use changes. The modeling approach supports the essential logic of probabilistic methods and indicates that spatial autocorrelation of various land use types and accessibility is the main drivers of urban land use changes.  相似文献   
3.
The exposed calcareous rocky area of the Abu Qir Headland,east of Alexandria,Egypt which range from coarse grains,through pebbles,cobbles,and boulders to rocky platforms,was signifi cantly colonized by sclerobionts(epibionts and endobionts).The epibiont species diversity was comparatively higher than that of endobionts.Epibiont communities included bryozoans(the anascan-grade cheilostome Bifl ustra savartii),serpulid(Hydroides elegans,Spirobranchus cf.tetraceros,Vermiliopsis striaticeps and Protula or Apomatus)and spirorbid(Spirorbis)wormtubes,and balanoid barnacles(Amphibalanus amphitrite,Balanus trigonus,and Perforatus perforatus).The cheilostome bryozoan colonies,which developed extensive sheets,proliferated on the study rocky shore either encrusting the bioeroded basement directly,or encrusting other epilithic taxa,particularly balanoid barnacles and serpulid worms.Encrusters displayed a remarkable marginal competitive interaction(overgrowth and stand-off)for space on the study rocky shore.On the other hand,endobionts were not well represented on the studied rocky shore exposure.It was possible to identify three ichnotaxa:Gastrochaenolites,Maeandropolydora,and Finichnus.The fi ndings documented represent a signifi cant contribution to our knowledge of sclerobionts composition,sequence of their colonization and/or bioerosion,and their mutual relationships on the intertidal rocky shore of the Abu Qir Headland.  相似文献   
4.
5.
Effects of rainfall patterns on runoff and rainfall-induced erosion   总被引:3,自引:0,他引:3  
Rainfall-induced erosion involves the detachment of soil particles by raindrop impact and their transport by the combined action of the shallow surface runoff and raindrop impact.Although temporal variation in rainfall intensity(pattern)during natural rainstorms is a common phenomenon,the available information is inadequate to understand its effects on runoff and rainfall-induced erosion processes.To address this issue,four simulated rainfall patterns(constant,increasing,decreasing,and increasing-decreasing)with the same total kinetic energy were designed.Two soil types(sandy and sandy loam)were subjected to simulated rainfall using 15 cm×30 cm long detachment trays under infiltration conditions.For each simulation,runoff and sediment concentration were sampled at regular intervals.No obvious difference was observed in runoff across the two soil types,but there were significant differences in soil losses among the different rainfall patterns and stages.For varying-intensity rainfall patterns,the dominant sediment transport mechanism was not only influenced by raindrop detachment but also was affected by raindrop-induced shallow flow transport.Moreover,the efficiency of equations that predict the interrill erosion rate increased when the integrated raindrop impact and surface runoff rate were applied.Although the processes of interrill erosion are complex,the findings in this study may provide useful insight for developing models that predict the effects of rainfall pattern on runoff and erosion.  相似文献   
6.
Dammam City is one of the gorgeous coastal areas in the Arabian Gulf of Saudi Arabia.The present study aimed to ex-amine one of the copepod species infecting the rosy goatfish that represents a highly consumed fish species by the local population in the Arabian Gulf.The copepod species isolated from the infected fish specimens belong to the family Taeniacanthidae and was iden-tified as Irodes parupenei Ho and Lin(2007),primarily based on its morphological,morphometric,and ultrastructural characteris-tics,especially the structures of the dorsal cephalic area,segmentation of the first antenna,the absence of the maxilliped claw in the fe-male specimens,and the setation and spinulation of the legs 2-4 for the adult females are of great significance in the taxonomic iden-tification.The 18S rRNA gene sequence was analyzed to ensure the precise identity and exact taxonomic status of the copepod species.The result showed that this copepod species belong to Taenicanthidae and closely related to Irodes sauridi(gb|JF781550.1)in the same taxon.More details on the specificity of the goatfish for Irodes species and identifying these parasitic taxa using molecular analysis are given in the present study.  相似文献   
7.
Ibrahim  Elkhedr  Mogren  Saad  Qaysi  Saleh  Abdelrahman  Kamal  Ghrefat  Habes  Zaidi  Faisal  Hakami  Ahmed 《Natural Hazards》2021,108(3):2613-2628
Natural Hazards - The main objective of this study is to detect the subsurface extension of salt diapirs and structural deformations in the city of Jazan and its suburbs using gravity data. Salt...  相似文献   
8.
Surface modification of two algal biomasses, Nizimuddinia zanardini and Stoechospermum marginatum, using 4-phenyl-3-thiosemicarbazide ligand was performed to investigate the consequences on the adsorption of heavy metals from aqueous solution. Stabilization of amino group of 4-phenyl-3-thiosemicarbazide on the surface of biomasses was confirmed using Fourier transform infrared spectroscopy. Chemical modification was found to exert significant positive effects on biosorption. Adsorption capacities for Pb(II), Cd(II) and Cr(VI) using modified N. zanardini were observed to be 19.3, 16.75 and 15.75 mg/g, respectively, compared to 17.48, 14.18 and 11.85 mg/g for raw N. zanardini biomass. Also, adsorption of Pb(II), Cd(II) and Cr(VI) by the modified S. Marginatum was found to be 17.54, 15.62 and 14.77 mg/g, respectively, in comparison with that of the raw biomass which were 16.86, 12.9 and 11.2 mg/g. The obtained results of the equilibrium adsorption were studied through different isotherm models of Langmuir, Freundlich and Temkin, where the Langmuir model was observed to agree well with the results. Prevalent kinetic models including pseudo-second order and intra-particle diffusion were applied, and the pseudo-second order was found to describe the adsorption kinetics data adequately. Intra-particle model was also utilized in order to show penetration of metal ions, where it was realized that the biosorption took place in two or three steps including film diffusion, molecular diffusion and chemical reaction.  相似文献   
9.
10.
In spite of Jordan's insignificant natural resources and geopolitical problems, industrial development is being emphasized in Jordan since 1972. Industries are now the second largest sector of economy. Industries contributed 10% of the GDP in 1972, 19.5% in 1989 and 17.4% in 1993. This is remarkable as the national investment in industries is declining. The investments for industrial development was 30% of the total national investment in five year development plans (1976–1980), 23% in the next plan (1981–1985), and 13% in the following plan (1986–1990).The number of; industries has increased from 2500 in 1959 to 4684 in 1974, to 8533 in 1984, and 18600 in 1992. The employment or labor force also increased from 10,000 in 1959 to 70,000 in 1988, and to 110,000 in 1992. It represents about 16.4% of the total labor force in Jordan, the index number of industrial production also increased from (100) in 1979 which was the same base year, to (151) in 1983 to (205) in 1987 and to (215) in 1993. The study was based on three hypotheses: (i) the magnitude varies from one industry to another at the national (Jordan) and local (governorate levels), (ii) temporal change in the magnitude of industries has taken place during the period 1979–1992, (iii) the temporal change in the magnitude of industries was positive in some industries and negative in others.  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