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991.
简述了在南海纳土纳岛(Natuna Islands)建设地震台站的意义和设备.用获得的首批观测资料,分别采用接收函数方法和ScS波分裂技术反演了纳土纳地震台下面地壳的S波速度结构和各向异性参数.结果表明纳土纳地震台下方地壳厚度约28 km,为典型的陆壳性质,上地幔40~50 km为低速层.纳土纳的地壳快波方向为S62°E,与GPS测量的亚洲南部巽他块体的地壳运动方向一致.  相似文献   
992.
化学方法改良吹填土固结沉降性质研究   总被引:1,自引:1,他引:0  
大连市大窑湾港区的吹填土为高分散性低液限粉质黏土,其特点是亲水性高,含水量大,排水率低,这造成了吹填土承载力低,在荷载作用下变形量大,在很长一段时间内无法作为正常建筑地基使用.通过在盐水环境下添加不同剂量的浓度为0.1%的絮凝剂Praestol-2515或Praestol-650溶液,可以观察到土颗粒迅速聚合,土粒粒径明显增大,粒间胶结更加均匀和紧密,形成絮状物,从而促进了土颗粒与自由水分的分离,导致过饱和吹填土(悬浊液)沉降速度大大提高,极大地缩短了吹填土的排水固结时间,在短期内达到建筑地基所需要的变形量和承载能力.研究结果对于沿海地区过饱和吹填土的造陆工程,以及类似的高含水率黏性土的地基处理具有重要的启示意义.  相似文献   
993.
由郭荣星教授撰写的《跨边界资源管理(第二版)》(英文名:Cross-Border Resource Management-Second Edition",由荷兰Elsevier出版社于2012年出版;网络版:http://www.sciencedirect.com/science/bookseries/14748177/10)是一本系统阐述在跨边界地区或是边界过渡地区对自然与环境资源如何有效管理的学术专著。在跨边界地区,政府行为和管理手段是复杂的,司法权通常受制于两个或以上的独立政权或行政/军事势力影响。本书的作者对跨边界地区的地理、政治、法理、社会、经济学以及文化多个问  相似文献   
994.
旱雀麦(Bromus tectorum)原产于欧亚大陆,18世纪传入北美,并成为该地区的入侵植物。然而,同为雀麦属的扁穗雀麦(Bromus catharticus)和无芒雀麦(Bromus inermis)并不具有旱雀麦的入侵性。本研究设置高温、低温和黑暗等处理,探讨温度和光照对3种植物种子萌发的影响,旨在从种子萌发的角度揭示旱雀麦的入侵性。结果表明:温度和光照对旱雀麦和扁穗雀麦种子的发芽率均无明显影响(p>0.05);高温和黑暗处理显著提高了无芒雀麦种子的发芽率(p<0.05),对旱雀麦、扁穗雀麦和无芒雀麦种子的发芽势、发芽指数、日均发芽率、发芽系数、发芽峰值和发芽值有一定的促进作用,而低温处理则表现出相反的效应;高温和黑暗处理对3种植物种子的平均发芽天数和萌发持续时间有一定降低的作用,而低温处理则表现出相反的效应。同一处理下旱雀麦种子萌发各项指标均优于另两种植物,这可能是旱雀麦具有较强入侵性的重要原因。  相似文献   
995.
This study investigated the seasonal changes in carbon (C) and nitrogen (N) stable isotope values of several typical food sources of Apostichopus japonicus in a farm pond, including particulate organic matter (POM), macroalgae, benthic microalgae and animals such as nematode and copepod. The stable isotope technique was used to quantify relative contributions of various sources to the food uptake by A. japonicus. The results showed that significant changes occurred in the C and N stable isotope values of sea cucumber food sources due to the seasonality of micro-or macroalgae prosperity and the fluctuation of environmental conditions. The sea cucumber A. japonicus exhibited corresponding alterations in feeding strategy in response to the changes in food conditions. Calculation with a stable isotope mixing model showed that macroalgae was the principal food source for A. japonicus throughout the 1-yr investigation, with the relative contribution averaging 28.1% - 63.2%. The relative contributions of other food sources such as copepod and nematode, POM, benthic microalgae to the total food uptake by sea cucumber averaged 22.6% - 39.1%, 6.3% - 22.2%, 2.8% - 6.5%, and 2.8% - 4.2%, respectively. Together these results indicated that the seasonal changes in food sources led to the obvious temporal differences in the relative contribution of various food sources utilized by A. japonicus. Such findings provide the basic scientific information for improving the aquaculture techniques of A. japonicus, particularly for optimizing the food environment of A. japonicus culture in farm ponds.  相似文献   
996.
Willow species(Salix fragilis L.and S.alba L.) are important elements of cold desert agroforestry systems in the Lahaul valley,northwestern Himalaya.Their ability to grow through shoot-cuttings plantations under extreme and xeric climatic conditions of cold deserts,makes them ecologically suited and socially accepted for forestry programmes.Willow species in cold deserts may combat desertification and can thrive well in these areas as compared to any other species.Salix fragilis L.and S.alba L.are under cultivation in the Lahaul valley.However,S.fragilis is widely cultivated under the agroforestry and plantation forestry systems.In the Lahaul valley,willow species are used as subsistence resources and for socio-religious purposes.The present study was carried out to examine the vegetation analysis,density,diversity and distribution of willow species,present status and potential willow plantation sites and uses.The results of present study revealed that a higher species density was recorded at middle altitude villages(Jahlma-3,000 m asl and Hinsa-2,700 m asl),except,a higher density of S.fragilis was at Khoksar(3,200 m asl) in plantation forestry on south-facing slopes.In forests,S.fragilis was planted mainly along the water channels,resulted a low density.The shrubby willow species occurred naturally in the entire Lahaul valley up to an altitude of 3,850 m asl.81% of households felt the scarcity of willow trees,whereas,19% of households were satisfied with the willow trees they owned.The majority of willow species were planted in middle altitudes on privately owned irrigated lands.It was rated most potential prospective willow planting site by the farmers.Small size of land-holdings was one of the main constraints for establishing a large number of willow plantations.Commercial aspects of willow species need to be investigated to encourage the farmers to plant more willows further.  相似文献   
997.
Organotin compounds (OTs) are ubiquitous in the marine environment and high concentrations (μg g(-1) range) in sediments from different coastal areas around the world have been reported. However, few reports have described the OTs contamination status in the offshore and deep sea environment. This work investigated organotin levels in Nazaré canyon for the first time. Levels of monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPT), triphenyltin (TPT), dioctyltin (DOT) and trioctyltin (TOT) were quantified in sediment samples from the upper flanks of the canyon and from the adjacent coastal area. TBT levels detected in the canyon flanks are about two to three orders of magnitude lower than those found in the coastal area. Nevertheless, when quantifiable, TBT levels in the canyon samples were higher than the Environmental Assessment Criteria set for TBT in sediments by the OSPAR Commission indicating that at those locations negative ecological impacts are likely to occur.  相似文献   
998.
The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.  相似文献   
999.
We propose a framework for spatially estimating a proxy for coral reef resilience using remote sensing. Data spanning large areas of coral reef habitat were obtained using the commercial QuickBird satellite, and freely available imagery (NASA, Google Earth). Principles of coral reef ecology, field observation, and remote observations, were combined to devise mapped indices. These capture important and accessible components of coral reef resilience. Indices are divided between factors known to stress corals, and factors incorporating properties of the reef landscape that resist stress or promote coral growth. The first-basis for a remote sensed resilience index (RSRI), an estimate of expected reef resilience, is proposed. Developed for the Red Sea, the framework of our analysis is flexible and with minimal adaptation, could be extended to other reef regions. We aim to stimulate discussion as to use of remote sensing to do more than simply deliver habitat maps of coral reefs.  相似文献   
1000.
Patterns of bivalve larvae dispersal in the deep Ahe atoll lagoon was studied by using a numerical 3D transport model (MARS3D) coupled with a vertical swimming sub-model, forced mainly by tide and wind-induced currents. The simulations were validated against observations of larval dispersal monitored several days throughout the lagoon. Connectivity matrices describing larval exchanges inside the lagoon were inferred. Larvae displayed a significant dispersal capacity at the lagoon scale, especially with dominant eastern winds. With southeastern winds, larvae mostly remained in their origin sector. The total export rate of the larvae, toward the ocean through the pass and shallow lagoon borders, was independent of the wind conditions, with 1% of the total concentration exported per day. However, the tide-driven currents efficiently flushed larvae in sectors close to the pass. Connectivity matrices suggest that the south and west sectors were more suitable for spat collecting and that central sectors would be efficient sanctuaries if genitors were accumulated.  相似文献   
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