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结合淮安供电公司地下停车库工程的结构设计,比较了各种楼盖形式及不同的抗浮措施对单建式地下车库设计的影响,并指出其各自的优缺点。着重讨论了无梁楼盖体系的几种常用计算方法。最后分析了超长结构无缝设计中后浇带的受力特点,提出了后浇带设置时应注意的问题及超长结构裂缝控制的施工措施。 相似文献
994.
岩质边坡锚杆设计计算方法分析 总被引:1,自引:0,他引:1
结合岩质边坡工程实例,对岩质边坡支护设计中的锚杆轴向拉力设计方法进行了分析和评价。通过对比分析发现:采用极限平衡法、强度折减法、等效内摩擦角法、二维数值分析计算法等方法的设计计算结果偏大,三维数值分析计算法计算结果比较可靠,符合工程实际。侧向岩石压力计算方法与剩余下滑力法的计算结果与数值分析计算法基本一致。在侧向压力接近于零时,建筑边坡支护技术规范采用的侧向岩石压力计算方法计算结果存在安全隐患。在这种情况下,建议采用强度折减法进行锚杆拉力的设计计算。锚杆轴力并非均匀分布,对边坡顶部、底部锚杆应予以加强。在施工阶段稳定性较好的边坡,可按正作法施工,充分发挥边坡的自稳能力,以减小锚杆轴力,可优化设计。 相似文献
995.
Considerations of rock dilation on modeling failure and deformation of hard rocks-a case study of the mine-by test tunnel in Canada 总被引:1,自引:0,他引:1
For the compressive stress-induced failure of tunnels at depth, rock fracturing process is often closely associated with the generation of surface parallel fractures in the initial stage, and shear failure is likely to occur in the final process during the formation of shear bands, breakouts or V-shaped notches close to the excavation boundaries. However, the perfectly elastoplastic, strain-softening and elasto-brittle-plastic models cannot reasonably describe the brittle failure of hard rock tunnels under high in-situ stress conditions. These approaches often underestimate the depth of failure and overestimate the lateral extent of failure near the excavation. Based on a practical case of the mine-by test tunnel at an underground research laboratory (URL) in Canada, the influence of rock mass dilation on the depth and extent of failure and deformation is investigated using a calibrated cohesion weakening and frictional strengthening (CWFS) model. It can be found that, when modeling brittle failure of rock masses, the calibrated CWFS model with a constant dilation angle can capture the depth and extent of stress-induced brittle failure in hard rocks at a low confinement if the stress path is correctly represented, as demonstrated by the failure shape observed in the tunnel. However, using a constant dilation angle cannot simulate the nonlinear deformation behavior near the excavation boundary accurately because the dependence of rock mass dilation on confinement and plastic shear strain is not considered. It is illustrated from the numerical simulations that the proposed plastic shear strain and confinement-dependent dilation angle model in combination with the calibrated CWFS model implemented in FLAC can reasonably reveal both rock mass failure and displacement distribution in vicinity of the excavation simultaneously. The simulation results are in good agreement with the field observations and displacement measurement data. 相似文献
996.
赵忆勇 《建筑·建材·装饰》2010,11(7)
园林树木在苗圃经过大苗培育,已进行过修剪,有的树形已经形成,栽植到园林绿地后,对定植后的树木要进行修剪、整形,调节树势,以保持合理的树冠结构,促进树木生长,形成优美树姿,追求美的景观效果. 相似文献
997.
Health risk assessment of inorganic arsenic intake of Cambodia residents through groundwater drinking pathway 总被引:3,自引:0,他引:3
Kongkea Phan Suthipong Sthiannopkao Kyoung-Woong Kim Ming Hung Wong Jamal Hisham Hashim Syed Mohamed Aljunid 《Water research》2010,44(19):5777-5788
In order to compare the magnitudes and health impacts of arsenic and other toxic trace elements in well water, groundwater and hair samples were collected from three areas with different arsenic exposure scenarios in the Mekong River basin of Cambodia. Ampil commune in Kampong Cham province was selected as an uncontaminated area, Khsarch Andaet commune in Kratie province was selected as a moderately contaminated area, and Kampong Kong commune in Kandal Province was selected as an extremely contaminated area. Results of ICP-MS analyses of the groundwater samples revealed that As, Mn, Fe and Ba concentrations were significantly different among the three study areas (Kruskal-Wallis test, p < 0.0001). Out of 46 observed wells in the Kandal province study area, 100% detected As > 50 μg L−1 and Fe > 300 μg L−1; 52.17% had Mn > 400 μg L−1 and 73.91% found Ba > 700 μg L−1. In the Kratie province study area (n = 12), 25% of wells showed elevated arsenic levels above 10 μg L−1 and 25% had Mn > 400 μg L−1, whereas samples from Kampong Cham province study area (n = 18) were relatively clean, with As < 10 μg L−1. A health risk assessment model derived from the USEPA was applied to calculate individual risks resulting from drinking groundwater. Computational results indicated that residents from Kandal Province study area (n = 297) confronted significantly higher non-carcinogenic and carcinogenic risks than those in Kratie (n = 89) and Kampong Cham (n = 184) province study areas (Kruskal-Wallis test, p < 0.0001). 98.65% of respondents from the Kandal province study area were at risk for the potential non-cancer effect and an average cancer risk index was found to be 5 in 1000 exposure. The calculations also indicated that, in the Kratie province study area, 13.48% of respondents were affected by non-cancer health risks and 33.71% were threatened by cancer, whereas none of respondents in the Kampong Cham province study area appeared to have non-carcinogenic effect. Positively significant correlations of the arsenic content in scalp hair (Ash) with both arsenic levels in groundwater (Asw) (rs (304) = 0.757, p < 0.0001) and individual average daily doses (ADD) of arsenic (rs (304) = 0.763, p < 0.0001) undoubtedly indicated that arsenic accumulation in the bodies of Cambodia residents in the Mekong River basin was mainly through a groundwater drinking pathway. To the best of our knowledge, this is the first comprehensive report comparing individual health risk assessments of arsenic exposure through a groundwater drinking pathway to enriched arsenic levels from groundwater in the Mekong River basin, Cambodia. This study indicates that elevated arsenic concentrations in groundwater may lead to thousands of cases of arsenicosis in the near future if mitigating actions are not taken. 相似文献
998.
工程能力是工程师最重要、最基本的素质之一,也是高等院校工程教育的薄弱环节。高等工程教育必须着力培养学生的工程能力。阐述了现代工程能力的内涵,分析了CDIO工程教育理念以及当前工程能力培养存在的问题,在此基础上,从多方面探讨和提出了基于CDIO工程能力培养的有效途径。 相似文献
999.
1000.