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1.
大中型煤炭企业具有与市场关联度高、风险损失大等特点,一旦出现信用风险,对企业以及社会的影响都是巨大的。为了能够准确识别煤炭企业的信用风险,本文以上市煤炭企业为研究对象,提出基于Filter-Wrapper两阶段特征选择的大中型煤炭企业信用风险评估模型。首先针对大中型煤炭企业的特点,在通用指标选择上结合煤炭企业风险因素提出两个新指标:抗风险能力、煤炭及加工产品业务销售毛利率;然后使用Filter-Wrapper两阶段特征选择算法用来筛选冗余特征,从而构建信用风险预测模型。实验表明所提出模型与筛选前相比具有更高的预测准确性,同时对信用风险违约样本识别率也更高,验证了模型与所提指标的有效性,对大中型煤炭企业的信用风险识别具有重要意义。 相似文献
2.
从时空角度研究长江经济带的水环境污染状况,探究异质性环境规制对水环境污染的影响,为促进水资源合理利用与绿色发展提供参考。基于2009—2019年长江经济带11个省市的面板数据,研究长江经济带水环境污染的时空特征,用Moran's I指数研究水环境污染的空间自相关性,再通过空间杜宾模型探究异质性环境规制对水环境污染的空间溢出效应。研究表明:1)总体来看,长江经济带水环境污染呈上升趋势,其中上游地区水环境污染增速较快,下游和中游地区有所放缓,水环境污染得到一定控制;2)长江经济带水环境污染严重程度具有明显的空间特征,呈现出下游>中游>上游的趋势;3)从异质性角度来看,命令控制型环境规制能显著抑制水环境污染,在经济矩阵下效果最为显著,市场激励型环境规制具有显著负向作用,而公众自愿型环境规制的作用并不明显;4)从溢出效应来看,命令控制型环境规制对周围省市的水环境污染具有负向的空间溢出效应,市场激励型环境规制也会减轻周围省市的水环境污染严重程度,但没有命令控制型环境规制效果明显,公众自愿型环境规制效果不显著。目前长江经济带水环境污染状况仍不容乐观,需要进一步加强管控。虽然命令控制型环境规制对水环境污染治理效果最好,但公众参与也应该提上日程。各地要因地制宜,选择合适的方式来治理,此外还需要建立空间意识,加强联合治理。 相似文献
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4.
钨作为不可再生的稀缺资源,普遍用于工业、机械制造、科技、国防电力电子、石油化工、国防军事等诸多领域.由于独特的性能和稀有的储藏量,钨矿也是极为重要的战略资源.开展钨矿开发利用水平评价,对提高我国矿产资源利用效率,减少对环境扰动,增强我国资源保障能力具有重要意义.本文从设计开采回采率、设计选矿回收率、实际开采回采率和实际选矿回收率建立数学模型,计算了湖南省钨矿开发利用水平,梳理了湖南省钨矿开发现状.计算结果表明,湖南省9座钨矿山的开发利用水平指数均超过了 100,且加权平均高达104.88,说明该省钨矿资源开发利用整体水平较高. 相似文献
5.
归一化水体指数(NDWI)是水体遥感反演的一种重要指标,其阈值及修正直接影响反演结果的精度。基于Landsat-8与GF-1光学多光谱影像,使用归一化水体指数法阈值0(TH0)、最大类间方差法(OTSU)自适应阈值(THotsu)与均值漂移聚类算法(Mean-Shift)自适应阈值(THMS)分别对典型正常水体、云雾覆盖水体、富营养化水体、高含泥沙水体进行水体遥感提取与效果分析,结果表明:正常水体以TH0为阈值提取精度最高,THMS提取精度次之,THotsu提取精度最差;而云雾覆盖水体、富营养化水体以及含泥沙水体使用THMS提取精度最高,尤其少量云雾覆盖下的水体,THMS具有更明显的优势,TH0提取精度次之,THotsu提取精度最差;对于不同的阈值,Land?sat-8比GF-1总体表现出更高的水体提取精度。Mean-Shift算法应用于NDWI阈值修正与水体遥感反演具有快速、水质适应性强、效果稳定的优势,对尤其是复杂条件下的水体信息遥感反演具有较好的提取效果。 相似文献
6.
为探讨太白金矿回收原采场边部残余低品位矿体的方案,通过层次分析法(AHP)与模糊数学(FUZZY)理论,选取对残采工程影响较大的9个因素,建立优选模型。运用层次分析法确定了各评价指标的权重;采用模糊数学法分析计算各采矿方法的定性、定量指标,分别得到各评价指标的隶属度。最终计算出3种工程布置方案的综合优选度分别为68.1%、69.3%、58.1%,从而沿矿体走向双进路布置确定为最优开采方案。实践表明,采用该模型优选的工程布置方案具有一定的科学性、合理性,值得借鉴与推广。 相似文献
7.
Aggregation operations play an essential role in time series database management. As the number of data increases, it is difficult for current solutions, such as summary table and MapReduce-based methods to respond to such queries with low latency. Other approaches, such as segment tree-based methods, have a poor insertion performance when the data size exceeds the available memory. This paper proposes a Persistent Index for Segmented Aggregations (PISA), which has fast insertion performance and low latency for aggregation queries. PISA uses a forest to overcome the performance disadvantage of insertion in traditional segment trees. By defining two kinds of tags, namely code number and serial number, we propose an algorithm to accelerate queries by avoiding unnecessary reading data on disk. Additionally, we extend it to Dual-PISA to tolerate a range of unordered data, which is very important in the real world. Dual-PISA is stored on disk and is hugely memory-efficient — only takes a few hundred bytes of memory for billions of data points. Dual-PISA can be easily implemented on both traditional databases and NoSQL systems. It handles aggregation queries within milliseconds on a commodity server, for a time range that contains tens of billions of data points. 相似文献
8.
采用COMSOL软件建立了油气润滑环状流管道与ECT系统的三维物理及有限元模型,结合电磁场理论获取了传感器的电容值;建立了电容值与成像灰度值一一对应的的RBF映射模型;提出了RBF算法并应用于油气润滑两相流动的图像重建过程;以图像相对误差(IME)和图像相关系数(CORR)为评价指标对该算法的进行实验验证。研究结果表明,RBF算法在ECT系统图像成像的准确性及相关性方面可以很好的适用于油气润滑;相较于其他图像重建算法,图像精度提高了40.52%,图像分辨率提高了22.13%。 相似文献
9.
Yulong Zhu Tatsuya Ishikawa Srikrishnan Siva Subramanian Bin Luo 《Soils and Foundations》2021,61(1):198-217
In 2005, the Japanese government launched a new nationwide early warning system for predicting debris flow and slope failure disasters based on rainfall intensity and the Soil Water Index (SWI). However, the Japanese government has not set early warning criteria in many mountain areas. In addition, the existing early warning criteria in some areas are much higher than realistic ones, and snowmelt water is not considered in the calculation of the SWI. These two factors have been the cause of many slope failures in seasonally cold regions, induced by rainfall and/or snowmelt, which were not predicted. Therefore, this study attempts to propose a new determination method for setting early warning criteria for rainfall- and/or snowmelt-induced slope failures in seasonally cold regions. For this purpose, the study firstly proposes a combination model for estimating snow density that incorporates the hourly snowmelt water into the Japanese early warning system more accurately by using meteorological monitoring data and modeled snow density. Next, based on case studies and parametric analyses for slope stability assessment, new early warning criteria are proposed for predicting three different patterns of slope failures under two typical types of precipitation (rainfall and snowmelt) conditions. Finally, a new determination method for setting early warning criteria in seasonally cold regions is proposed by referring to the existing early warning criteria near the target area, in accordance with the precipitation types and the local ground conditions of the slopes. Since the existing early warning criteria near the target area already take the effects of the variations in local geology and geography into account, the new determination method for early warning criteria can be applied to arbitrary areas in seasonally cold regions, without directly considering the local soil properties, in the actual design and maintenance works. 相似文献
10.
Assessing all pertinent environmental variables to categorize a skill level to safely navigate the water environment can be difficult for inexperienced kayakers, especially at a remote site where internet access is limited. A real-time kayaker safety assessment of water environmental conditions at the Mainland Sea Caves of the Apostle Islands National Lakeshore, Lake Superior is achieved. We present a new cyberinfrastructure that provides kayakers with real-time data access and a Safety Index (SI) with consideration of multiple environmental factors to characterize the degree of navigational difficulty for classifying kayaker skill levels. Specifically, radar reflectivity is added to improve forecasts of dangerous conditions caused by convective storms using state-of-the-art weather and wave modeling. Spectral characteristics of surface waves are employed to correlate the occurrences of extreme and freak waves. In addition, unexpectedly dangerous conditions like coastal upwelling and freak wave occurrence due to changing wind directions are considered. A contingency plan is implemented to handle the issue of possibly missing required environmental data. Display of the SI and visualization of other real-time environmental data are communicated by a power-efficient kiosk. Web analytics demonstrates a public interest in real-time water conditions and the need for the on-site kiosk to provide the latest information before kayakers enter the water. The new real-time water environment cyberinfrastructure for kayaker safety in the Apostle Islands, Lake Superior has been successfully operated since 2014. 相似文献