全文获取类型
收费全文 | 25605篇 |
免费 | 3257篇 |
国内免费 | 1962篇 |
专业分类
电工技术 | 3066篇 |
综合类 | 3023篇 |
化学工业 | 2378篇 |
金属工艺 | 1879篇 |
机械仪表 | 2005篇 |
建筑科学 | 1965篇 |
矿业工程 | 607篇 |
能源动力 | 700篇 |
轻工业 | 1139篇 |
水利工程 | 586篇 |
石油天然气 | 1594篇 |
武器工业 | 338篇 |
无线电 | 2723篇 |
一般工业技术 | 2567篇 |
冶金工业 | 1064篇 |
原子能技术 | 221篇 |
自动化技术 | 4969篇 |
出版年
2024年 | 74篇 |
2023年 | 458篇 |
2022年 | 815篇 |
2021年 | 995篇 |
2020年 | 1005篇 |
2019年 | 762篇 |
2018年 | 679篇 |
2017年 | 896篇 |
2016年 | 1001篇 |
2015年 | 1054篇 |
2014年 | 1688篇 |
2013年 | 1661篇 |
2012年 | 1996篇 |
2011年 | 2002篇 |
2010年 | 1541篇 |
2009年 | 1572篇 |
2008年 | 1424篇 |
2007年 | 1721篇 |
2006年 | 1488篇 |
2005年 | 1254篇 |
2004年 | 1059篇 |
2003年 | 934篇 |
2002年 | 832篇 |
2001年 | 660篇 |
2000年 | 593篇 |
1999年 | 445篇 |
1998年 | 362篇 |
1997年 | 331篇 |
1996年 | 260篇 |
1995年 | 239篇 |
1994年 | 208篇 |
1993年 | 171篇 |
1992年 | 160篇 |
1991年 | 101篇 |
1990年 | 75篇 |
1989年 | 84篇 |
1988年 | 50篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 20篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1962年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 116 毫秒
91.
在井下综采工作面一侧巷道内激发槽波,另一侧巷道中接收通过采面透射的槽波。利用煤层与岩层的物理力学差异,分析在煤层中激发和接收到的槽波,以此来探查综采工作面中地质构造、煤体破碎区、应力集中区的位置,从而为后期探测地质构造参数、煤体破碎区注浆、应力集中区消突等工作的顺利进行提供基础数据,提高后期工程实施的针对性。 相似文献
92.
为探讨陶瓷颗粒对树脂基摩擦材料力学性能的影响,以SiO_2颗粒增强酚醛树脂基摩擦材料为例,利用三点弯曲实验研究颗粒特征对弯曲强度的影响,建立材料内部弹性应力场分布模型,并从细观力学角度进行分析。实验结果表明:添加二氧化硅陶瓷颗粒后,复合材料的弯曲强度降低、弹性模量升高;复合材料弯曲断裂截面显示脆性断裂特征,断裂过程中裂纹遇到颗粒贯穿通过;复合材料弯曲强度随颗粒含量增加而降低,随颗粒弹性模量增加先减小后增大。理论分析表明:陶瓷复合树脂基摩擦材料内部最大应力值位于颗粒边缘处;最大应力值随颗粒与基体弹性模量比值增大而增大;复合材料的平均应力与颗粒的含量成正相关。实验和理论研究表明,陶瓷颗粒添加引起材料内部应力集中,且与颗粒弹性模量和颗粒含量成正相关。 相似文献
93.
Ventilation system analysis for underground mines has remained mostly unchanged since the Atkinson method was made popular by Mc Elroy in 1935. Data available to ventilation technicians and engineers is typically limited to the quantity of air moving through any given heading. Because computer-aided modelling, simulation, and ventilation system design tools have improved, it is now important to ensure that developed models have the most accurate information possible. This paper presents a new technique for estimating underground drift friction factors that works by processing 3 D point cloud data obtained by using a mobile Li DAR. Presented are field results that compare the proposed approach with previously published algorithms, as well as with manually acquired measurements. 相似文献
94.
95.
利用有限元软件对空冷后具有一定温度梯度的板坯的轧制过程进行数值模拟计算,研究分析两种不同高温力学特性的钢种在轧制时边角部金属的位移、应变及应力情况,分析边部线状缺陷起源的褶皱的形成过程并通过轧制试验予以验证。分析结果表明,边线形成与变形温度范围内变形抗力的不连续变化具有明显相关性,变形抗力随温度连续变化的钢种轧制过程角部金属不会形成褶皱;变形抗力随变形温度不连续变化的钢种,当板坯角部金属进入两相区时,由于轧制过程两相区变形抗力出现谷值,易出现褶皱并最终演变为边部线状缺陷。 相似文献
96.
Yupeng
Jiang Minchen Li Chenfanfu Jiang Fernando Alonso-Marroquin 《International journal for numerical methods in engineering》2020,121(14):3021-3047
Capturing the interaction between objects that have an extreme difference in Young's modulus or geometrical scale is a highly challenging topic for numerical simulation. One of the fundamental questions is how to build an accurate multiscale method with optimal computational efficiency. In this work, we develop a material-point-spheropolygon discrete element method (MPM-SDEM). Our approach fully couples the material point method (MPM) and the spheropolygon discrete element method (SDEM) through the exchange of contact force information. It combines the advantage of MPM for accurately simulating elastoplastic continuum materials and the high efficiency of DEM for calculating the Newtonian dynamics of discrete near-rigid objects. The MPM-SDEM framework is demonstrated with an explicit time integration scheme. Its accuracy and efficiency are further analyzed against the analytical and experimental data. Results demonstrate this method could accurately capture the contact force and momentum exchange between materials while maintaining favorable computational stability and efficiency. Our framework exhibits great potential in the analysis of multi-scale, multi-physics phenomena. 相似文献
97.
98.
脱硫废水零排放(ZLD)已成为现阶段环境治理的趋势,传统的治理方法具有高成本、难维护等缺点,因此提出一种利用中高温烟气干燥电厂脱硫废水的新技术。通过将选择性催化还原(SCR)脱硝后的热烟气引入喷雾干燥器,雾化废水使其与烟气充分接触,经干燥进入空气预热器后的原烟道。结果表明:抽取锅炉烟气量的7%左右可干燥脱硫废水2.5 t,使锅炉热效率降低0.68%左右,影响较小。干燥后烟气酸露点温度从93.20℃提高到96.72℃,不会腐蚀空气预热器等后续工艺设备,同时该技术有利于静电除尘器(ESP)、湿法烟气脱硫(WFGD)系统的运行,利用中高温烟气干燥脱硫废水是可行且有效的技术方法。 相似文献
99.
Efficient 3D point clouds classification for face detection using linear programming and data mining
Most of the applications related to security and biometric rely on skin region detection such as face detection, adult 3D objects filtering, and gesture recognition. In this paper, we propose a robust method for skin detection on 3D coloured point clouds. Then, we extend this method to solve the problem of 3D face detection. To do so, we construct a weighted graph from initial coloured 3D point clouds. Then, we present a linear programming algorithm using a predictive model based on a data mining approach to classify and label graph vertices as skin and non-skin regions. Moreover, we apply some refinement rules on skin regions to confirm the presence of a face. Furthermore, we demonstrate the robustness of our method by showing and analysing some experimental results. Finally, we show that our method deals with many data that can be represented by a weighted graph such as 2D images and 3D models. 相似文献
100.
Guihua Liu Dan Luo Rui Gao Yongfeng Hu Aiping Yu Zhongwei Chen 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(37)
The practical application of lithium–sulfur (Li–S) batteries is hindered by the “shuttle” of lithium polysulfides (LiPS) and sluggish Li–S kinetics issues. Herein, a synergistic strategy combining mesoporous architecture design and defect engineering is proposed to synthesize multifunctional defective 3D ordered mesoporous cobalt sulfide (3DOM N‐Co9S8?x) to address the shuttling and sluggish reaction kinetics of polysulfide in Li–S batteries. The unique 3DOM design provides abundant voids for sulfur storage and enlarged active interfaces that reduce electron/ion diffusion pathways. Meanwhile, X‐ray absorption spectroscopy shows that the surface defect engineering tunes the CoS4 tetrahedra to CoS6 octahedra on Co9S8, endowing abundance of S vacancies on the Co9S8 octahedral sites. The ever‐increasing S vacancies over the course of electrochemical process further promotes the chemical trapping of LiPS and its conversion kinetics, rendering fast and durable Li–S chemistry. Benefiting from these features, the as‐developed 3DOM N‐Co9S8?x/S cathode delivers high areal capacity, superb rate capability, and excellent cyclic stability with ultralow capacity fading rate under raised sulfur loading and low electrolyte content. This design strategy promotes the development of practically viable Li–S batteries and sheds lights on the material engineering in related energy storage application. 相似文献