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161.
To plan undeveloped optimal routes between Asia and Europe via the Arctic Northeast Passages using a 3D geographic information system (GIS), voyage paths are simulated in a 3D visual form. This ensures that the distances are calculated accurately, and that other voyage data such as water depths, sea ice distribution, and seashore topology are also easily deciphered, giving a more direct and clear demonstration compared to simplified presentations on an Electronic Chart Display & Information System (ECDIS). This article also implements a higher-geometry maze router in ice zone areas to obtain the optimal path in relation to safety and costs. This article compares the optimal Arctic Northeast Passages with traditional routes through the Suez Canal for dynamic analyses of the cost efficiency (including time costs, fuel costs, and other factors) of travel between major ports in Asia and Europe. The average benefit assessment is around 30–45% in a bulk carrier comparison. Thus, a 3D GIS can easily obtain and demonstrate safe navigation routes, providing a very convenient tool for initial planning.  相似文献   
162.
The Himalayan Foreland Basin in the Ganga Valley is key to assessing the pre‐collision relationship between cratonic India and the Himalaya – the world's largest mountain chain. The subsurface Ganga Supergroup, representing the sedimentary basement of the Ganga Valley, has been interpreted as a northern extension of the Proterozoic Vindhyan Supergroup in cratonic India. This interpretation is contentious because the depositional age of the Ganga Supergroup is not resolved: whereas the lower Ganga Supergroup is widely regarded as Proterozoic, the upper Ganga Supergroup has been variously inferred to include Neoproterozoic, lower Palaeozoic, or Cretaceous strata. Here, we integrate biostratigraphic and detrital zircon data from drill cores to show that the entire Ganga Supergroup is likely Proterozoic and can be correlated with Proterozoic successions on the northern Indian craton and in the Lesser Himalaya. This helps redefine the first‐order stratigraphic architecture and indicates broad depositional continuity along the northern Indian margin during the Proterozoic.  相似文献   
163.
The precision and accuracy of 40Ar/39Ar dates are ultimately linked to co-irradiated reference materials of known age. Here we provide new data from the SK01 sanidine, which was analysed in three different laboratories to evaluate it as a 40Ar/39Ar reference material. Aliquots of 5 mg, incrementally heated in two laboratories, yielded indistinguishable results with a weighted mean age of 27.58 ± 0.06 Ma (95% confidence level). Single-crystal step heating and single-crystal total fusion analyses of SK01 sanidine were undertaken in the third laboratory to further test the intracrystalline homogeneity. For the seven step-heating analyses, six crystals yielded nearly concordant age spectra with 40Ar/39Ar ages ranging from 26.853 ± 0.094 Ma to 26.963 ± 0.067 Ma, whereas one crystal gave an older age of 27.774 ± 0.071 Ma with a slightly discordant age spectrum. Twenty-three single-crystal total fusion analyses yielded 40Ar/39Ar ages ranging from 27.070 ± 0.108 Ma to 27.736 ± 0.062 Ma with a dispersion of ~ 3.8%. The older ages from single-crystal total fusion dates are interpreted to reflect an inherited or excess argon component in some crystals. This is an initial characterisation of the SK01 sanidine, and additional work needs to be conducted to further evaluate the age dispersion so that it can be utilised as a 40Ar/39Ar reference material.  相似文献   
164.
对广西东部大瑶山-大明山地区分别位于早古生代不整合面之下和之上的寒武纪和泥盆纪地层进行了系统的碎屑锆石U-Pb同位素年代学研究.除少数为早太古宙锆石外, 寒武纪地层碎屑锆石的年龄主要有2.7~2.6、~1.8、1.4~1.1和~1.0Ga四组峰值及分别为250Ma和105Ma的热液改造年龄记录; 泥盆纪地层碎屑锆石除少数具有古太古代年龄外, 其余主要形成于~1.7和~1.0Ga, 并记录了强烈的~100Ma的热改造事件.这些特征表明, 研究区具有华夏陆块的属性, 扬子与华夏陆块的边界应位于该区西北以远; 经加里东构造事件后, 研究区沉积盆地的物源区发生了改变, 因而加里东期岩浆作用在本区并没有显示.结合前人研究成果分析, 加里东事件可能指示了已裂开古陆块与华夏陆块间发生的斜向碰撞, 而大瑶山-大明山地区为沿垂直于该碰撞方向挤压形成的被动盆地.区域地层中部分碎屑锆石U-Pb同位素组成的重置和热液锆石的形成, 反映了研究区在印支期和燕山期存在大规模流体参与的热改造事件, 这些热液对流作用应是导致本地区乃至整个华南褶皱带陆缘Au-Cu多金属矿带形成的重要原因之一.   相似文献   
165.
166.

The control of soil pollution in China has become an issue, and in this study, a compound contaminated site was selected and focus on the site and its nearby environment, organochlorine pesticides (OCPs) were investigated in both soil (top and deep soil) and air samples. The main pollutants in top soils at site are dichlorodiphenyltrichloroethane (DDTs, 0.05–104 mg/kg d.w., avg: 14.5 mg/kg d.w.) and hexachlorobenzene (HCB, 0.02–4.85 mg/kg d.w., avg: 0.72 mg/kg d.w.) which is in accordance with its production history. As for the deep soils, ΣOCPs at site were found concentrated at workshops especially the technical pesticide workshop (5.29–22.1 mg/kg d.w., avg: 9.15 mg/kg d.w.) and the history DDTs’ workshop (4.00–64.8 mg/kg d.w., avg: 20.4 mg/kg d.w). Around site, OCPs were mainly concentrated at layers of −20 cm and the −40 cm and decreased with distance being far away, at 5000 m, the ΣOCPs was comparable with normal agriculture soil (22.1−91.4 ng/g d.w., avg: 55.4 ng/g d.w.). ΣOCPs in the air samples ranged 64.6–823 ng/m3 (avg: 459 ng/m3) at site and 9.93–176 ng/m3 (avg: 50.8 ng/m3) around site which are all dominated with DDTs and HCHs. Soil–air exchange fugacity was calculated to judge the transportation of the OCPs and the results showed soils at the site and its nearby areas (within 5000 m) are releasing most of the OCPs into air, and accordingly through evaluation, inhalation was found to be the major source for human health risk, which is a great threat to the workers at site and the nearby residents.

  相似文献   
167.
有毒铜绿微囊藻对鱼和溞的毒性   总被引:12,自引:2,他引:12  
用有毒铜绿微囊藻细胞及其从毒细胞中提取的毒素喂养和腹腔注射鱼类,结果表明:(1)微囊藻毒素MCYST-LR对所有实验过的鱼有毒害作用(LD_(50)为110-500μg/kg).注射毒素24h后,鱼肝电镜超微结构观察均表现出肝损伤.(2)在受控条件下,当用有毒铜绿微囊藻作为食物喂养日鲢和罗非鱼时,鱼类能在以毒藻为唯一食物的环境中生活20d以上.白鲢和罗非鱼粪便的毒性比喂食藻类的毒性分别降低约2—4.5倍,其肝的超微结构现察仍有轻度损伤.(3)在培养液中加入15μg/mLMCYST-LR和用实验室纯培养的铜绿微囊藻作为食物培养枝角类时,均可使它们在48h死亡.以无毒微囊藻培养时则生长不良亦不怀卵,表明它不是枝角类合适的食物.  相似文献   
168.
江苏省锡山市西部地区地下水资源计算模型研究   总被引:4,自引:0,他引:4  
从地下水运动均衡原理的角度分析江苏省锡山市西部地区第Ⅱ承压含水层天然和现状开采条件下的地下水均衡要素.揭示了该区地下水开采与地面沉降的关系,其中现状开采条件下的75%~80%的开采量来自于粘性土层的压密水量.根据地面沉降的发生机理剖析地面沉降严重发育地区忽略地面沉降影响因子建立的地下水资源计算模型中存在的问题针对存在的问题,提出了地下水可开采资源合理的计算方法,并对融有地面沉降影响因子的地下水资源计算模型的可实现性进行了分析.  相似文献   
169.
以五莲分岭山火山机构为例,运用高精度的^40Ar-^39Ar定年技术,对胶莱盆地青山组火山岩的形成年龄进行了精确测定。结果表明。青山组第一旋回中偏碱性富钾火山岩的形成年龄为109.9±0.6Ma,第二旋回酸性流纹质火山岩形成年龄为108.2±0.6Ma,据此确定胶莱盆地青山组火山岩应为早白垩世岩浆活动的产物。根据该组火山岩在空间上具有自西向东年龄渐新的演变趋势,表明中生代伊泽奈崎板块向欧亚板块碰撞俯冲应是制约区内火山活动的主要动力因素。  相似文献   
170.
The extensive spread ofPhragmites australis throughout brackish marshes on the East Coast of the United States is a major factor governing management and restoration decisions because it is assumed that biogeochemical functions are altered by the invasion. Microbial activity is important in providing wetland biogeochemical functions such as carbon and nitrogen cycling, but there is little known about sediment microbial communities inPhragmites marshes. Microbial populations associated with invasivePhragmites vegetation and with native salt marsh cordgrass,Spartina alterniflora, may differ in the relative abundance of microbial taxa (community structure) and in the ability of this biota to decompose organic substrates (community biogeochemical function). This study compares sediment microbial communities associated withPhragmites andSpartina vegetation in an undisturbed brackish marsh near Tuckerton, New Jersey (MUL), and in a brackish marsh in the anthropogenically affected Hackensack meadowlands (SMC). We use phospholipid fatty acid (PLFA) analysis and enzymataic activity to profile sediment microbial communities associated with both plants in each site. Sediment analyses include bulk density, total organic matter, and root biomass. PLFA profiles indicate that the microbial communities differ between sites with the undisturbed site exhibiting greater fatty acid richness (62 PLFA recovered from MUL versus 38 from SMC). Activity of the 5 enzymes analyzed (β-glucosidase, acid phosphatase, chitobiase, and 2 oxidases) was higher in the undisturbed site. Differences between vegetation species as measured by Principal Components Analysis were significantly greater at the undisturbed MUL site than at SMC, and patterns of enzyme activity and PLFAs did not correspond to patterns of root biomass. We suggest that in natural wetland sediments, macrophyte rhizosphere effects influence the community composition of sediment microbial populations. Physical and chemical site disturbances may impose limits on these rhizosphere effects, decreasing sediment microbial diversity and potentially, microbial biogeochemical functions.  相似文献   
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