全文获取类型
收费全文 | 27644篇 |
免费 | 1896篇 |
国内免费 | 1594篇 |
专业分类
电工技术 | 661篇 |
技术理论 | 1篇 |
综合类 | 2693篇 |
化学工业 | 1116篇 |
金属工艺 | 479篇 |
机械仪表 | 1446篇 |
建筑科学 | 2366篇 |
矿业工程 | 3356篇 |
能源动力 | 537篇 |
轻工业 | 454篇 |
水利工程 | 552篇 |
石油天然气 | 6369篇 |
武器工业 | 77篇 |
无线电 | 1035篇 |
一般工业技术 | 2055篇 |
冶金工业 | 871篇 |
原子能技术 | 87篇 |
自动化技术 | 6979篇 |
出版年
2024年 | 43篇 |
2023年 | 275篇 |
2022年 | 398篇 |
2021年 | 539篇 |
2020年 | 636篇 |
2019年 | 558篇 |
2018年 | 526篇 |
2017年 | 718篇 |
2016年 | 910篇 |
2015年 | 937篇 |
2014年 | 1802篇 |
2013年 | 1765篇 |
2012年 | 2206篇 |
2011年 | 2165篇 |
2010年 | 1597篇 |
2009年 | 1716篇 |
2008年 | 1661篇 |
2007年 | 1789篇 |
2006年 | 1658篇 |
2005年 | 1507篇 |
2004年 | 1197篇 |
2003年 | 1073篇 |
2002年 | 878篇 |
2001年 | 829篇 |
2000年 | 710篇 |
1999年 | 570篇 |
1998年 | 435篇 |
1997年 | 307篇 |
1996年 | 337篇 |
1995年 | 311篇 |
1994年 | 228篇 |
1993年 | 136篇 |
1992年 | 122篇 |
1991年 | 104篇 |
1990年 | 95篇 |
1989年 | 91篇 |
1988年 | 66篇 |
1987年 | 32篇 |
1986年 | 22篇 |
1985年 | 16篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 18篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1964年 | 8篇 |
1963年 | 9篇 |
1961年 | 8篇 |
1955年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
双玻光伏组件以其抗PID性强、防隐裂、防水汽透过、抗蜗牛纹、可靠性优异、轻量化等诸多优点,在晶硅太阳能组件市占比逐步提高。双玻光伏组件用背板玻璃一般需要预留出线孔,光伏背板玻璃的出线孔主要有两种打孔方式:金钢钻上下同步钻孔的模式和激光打孔。激光打孔以其易维护、可异形孔加工、效率高、生产成本低等优势得到各大玻璃厂的认可。通过分析在实际生产中激光打孔出现的打孔缺陷问题,提出了改善措施,有助于工厂的降本增效。 相似文献
2.
3.
4.
5.
《Ceramics International》2022,48(7):9658-9666
Polycrystalline Nd:YAG materials have wide applications in solid-state lasers. In this study, micro hole drilling experiments were performed on polycrystalline Nd:YAG using a polycrystalline diamond micro drill. The hole diameter, edge chipping, and hole wall surface quality were examined in detail. The results showed that the hole diameter was slightly larger than tool diameter. A diameter error of less than 5.5% was achieved. The edge chipping at the entry hole was formed by the encircled petal shape exfoliations, which were produced by the indentation and rotation movement in the drilling entry stage. Edge chipping at the exit hole was generated by an entire piece of exfoliation, which was produced by a circle of microcracks around the tool tip propagating to the bottom surface in the drilling exit stage. The edge chipping width at the entry hole was smaller than that at the exit hole. Based on different material removal modes, the hole surface morphology was classified into three types: ductile removal, coexisting ductile and brittle removal, and brittle removal. The hole surface quality mainly depended on the proportion of the brittle fracture to ductile removal surface. 相似文献
6.
7.
8.
针对货运车辆在配送调度过程中产生大量碳排放的问题,建立模型将多种影响碳排放量的因素协同优化。模型中考虑了不同载重量的异质车队,两个节点之间有多条道路的柔性路径,以及车辆重量随卸货而减少的动态负载等因素,以碳排放量、行驶时间和行驶路程为优化目标,并加入了节点需求时间窗、根据速度变化划分路段、交接和卸货时间的约束。提出了一种混合蚁群算法,利用蚁群算法信息素强度更新方式保持群体记忆性,利用粒子群算法的快速收敛特性增加计算效率。通过随机数值算例的仿真优化与对比分析,验证了算法和模型的有效性。 相似文献
9.
This paper presents a control design for the one‐phase Stefan problem under actuator delay via a backstepping method. The Stefan problem represents a liquid‐solid phase change phenomenon which describes the time evolution of a material's temperature profile and the interface position. The actuator delay is modeled by a first‐order hyperbolic partial differential equation (PDE), resulting in a cascaded transport‐diffusion PDE system defined on a time‐varying spatial domain described by an ordinary differential equation (ODE). Two nonlinear backstepping transformations are utilized for the control design. The setpoint restriction is given to guarantee a physical constraint on the proposed controller for the melting process. This constraint ensures the exponential convergence of the moving interface to a setpoint and the exponential stability of the temperature equilibrium profile and the delayed controller in the norm. Furthermore, robustness analysis with respect to the delay mismatch between the plant and the controller is studied, which provides analogous results to the exact compensation by restricting the control gain. 相似文献
10.
The airline industry is a representative industry with high cost and low profitability. Therefore, airlines should carefully plan their schedules to ensure that overall profit is maximized. We review the literature on airline planning and scheduling and focus on mathematical formulations and solution methodologies. Our research framework is anchored on three major problems in the airline scheduling, namely, fleet assignment, aircraft routing, and crew scheduling. General formulation, widely used solution approaches, and important extensions are presented for each problem and integrated problems. We conclude the review by identifying promising areas for further research. 相似文献