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981.
Identification of optimal sites for the isolation of waste on the abyssal seafloor was performed with two approaches: by the traditional method of map overlays of relevant attributes, and by a specially developed, automated Site-Selection Model (SSM). Five initial, Surrogate Sites, identified with the map-overlay approach, were then compared with the more rigorously produced scores from the SSM. The SSM, a process for optimization of site locations, accepts subjective, expert-based judgments and transforms them into a quantitative, reproducible, and documented product. The SSM is adaptable to any siting scenario. Forty-one factors relevant to the isolation scenario, including 21 weightable factors having a total of 123 scorable categories, have been entered into the SSM. Factors are grouped under project definition, unique environments, anthropogenic, geologic, biologic, weather, oceanographic and distance criteria. The factor scores are linked to a georeferenced database array of all factors, corresponding to 1°×1° latitude–longitude squares. The SSM includes a total of 2241 one-degree squares within 1000 n.m. of the U.S. coasts, including the western North Atlantic, the Gulf of Mexico, and the eastern North Pacific. Under a carefully weighted and scored scenario of isolation, the most favorable sites identified with the SSM are on the Hatteras and Nares Abyssal Plains in the Atlantic. High-scoring sites are also located in the Pacific abyssal hills province between the Murray and Molokai Fracture Zones. Acceptable 1° squares in the Gulf of Mexico are few and of lower quality, with the optimum location on the northern Sigsbee Abyssal Plain. Two of the five Surrogate Site locations, on the Hatteras and Sigsbee Abyssal Plains, correspond to the best SSM sites in each ocean area. Two Pacific and a second Atlantic Surrogate Site are located in low-scoring regions or excluded by the SSM. Site-selection results from the SSM, although robust, are an initial attempt to quantify the site-selection process. The SSM database exposes a significant lack of high-quality information for many areally mappable attributes on the abyssal seafloor, particularly bottom-current speed and measures of biologic productivity and flux. Terminologies and classifications of some measures, such as sediment types, suffer from parochialism and vary by ocean. Considerable research is needed even for a broad understanding of the environmental measures required to make sound societal decisions about use of the abyssal seafloor for disposal or other purposes. 相似文献
982.
983.
984.
利用BP、RBF神经网络自适应学习法模型,对社会消费品总额进行了预测和研究,结果表明用RBF网络自适应学习法所建立的模型经过训练后,可得到较精确的预测结果,并具有较强的应用性。 相似文献
985.
986.
Transportation agencies experiences with decision support systems for airport ground access planning
This article reports on a field investigation into the ways that transportation agencies use quantitative and qualitative information for making strategic decisions regarding airport ground access. The study analyzes the value of this information for planning airport ground access improvements at seven major international airport sites.The major finding of the research is that quantitative modeling for strategic decision support is very difficult, costly and time consuming. Modelers are confident that the models are accurate and reliable but executives generally lack confidence in the results. Transportation officials believe that the information supplied is flawed by a number of defects that minimize its value for strategic decision makers. The information defects described in this article provide an analysis of the structural difficulty of using quantitative modeling for transportation problems of strategic importance. To date, qualitative information is not frequently used, but some transportation agencies are considering its application to designing transportation services. Although this study is limited to airport ground access, the authors feel that this evidence, in conjunction with the evidence from other studies in the transportation area, dictates a need for wariness in the development of decision support systems for transportation planners. Developers of decision support systems for transportation planners must be aware of modeling costs and defects and consider how to improve the timeliness, relevance and credibility of information quantitative models provide transportation executives. Fundamentally it is important to recognize that decision makers tend, either singularly or in concert with other individuals or groups, to be the champions of a long-term vision for the community. When modeling produces inconsistent or wide ranging results that contradict their position, decision makers may not only discard modeling activities, but lose confidence in the models altogether. As a consequence, transportation planners are faced with the challenge of how to improve quantitative modeling. The most reliable and effective means for improvement is incorporation of qualitative techniques which provide greater understanding of customer perceptions and human behavior. 相似文献
987.
988.
全长粘结岩锚抗拔受力特性 总被引:1,自引:0,他引:1
根据锚杆与锚固浆之间界面耦合机理,分析了岩锚抗拔状态下界面剪应力的分布特征。基于变形协调得出小荷载情况下界面剪应力随离锚固受力点距离的增大成指数衰减,并随荷载增加,界面出现4个变形段,分离段和残余变形段随着塑性区开展产生非耦应力向远端传递。耦合区界面剪应力分布与小荷载情况不同,其相关模量参数可采用综合折减系数表示。同时,提出了单孔多锚杆受力剪应力衰减模型,并通过试验证示了现场锚杆在荷载逐级加大时,剪应力峰值强度的变化规律。 相似文献
989.
混合交通流参数之间关系模型标定 总被引:1,自引:1,他引:0
提出了混合交通流参数之间关系模型的标定和超车换道率的计算方法,采用广深高速公路、广佛高速公路和沪宁高速公路的实测数据对模型进行了验证,并计算了各数据点的超车换道率.结果表明,流量、密度数据的相关系数都接近1,超车换道率介于-1和1之间. 相似文献
990.
盾构隧道管片结构纵向错台研究 总被引:1,自引:0,他引:1
盾构隧道通缝拼装管片结构的错台一直是困扰盾构隧道施工的技术问题,且由错台引起的管片开裂、拼装困难和防水隐患等问题对施工和运营的影响日益凸显,并直接影响到工程质量。以上海轨道交通二号线西延伸段盾构隧道工程为背景,采用现场监测和数值计算方法对盾构推进过程中管片错台进行分析,获得了管片结构错台发生及发展的变化规律。进一步探讨了盾构千斤顶的顶力对错台大小及发展规律的影响,为盾构施工中减小错台,提高施工精度和质量,以及盾构隧道设计施工提供依据。 相似文献