全文获取类型
收费全文 | 4066篇 |
免费 | 396篇 |
国内免费 | 279篇 |
专业分类
电工技术 | 173篇 |
综合类 | 365篇 |
化学工业 | 381篇 |
金属工艺 | 352篇 |
机械仪表 | 306篇 |
建筑科学 | 1051篇 |
矿业工程 | 945篇 |
能源动力 | 92篇 |
轻工业 | 72篇 |
水利工程 | 99篇 |
石油天然气 | 79篇 |
武器工业 | 169篇 |
无线电 | 48篇 |
一般工业技术 | 351篇 |
冶金工业 | 205篇 |
原子能技术 | 8篇 |
自动化技术 | 45篇 |
出版年
2024年 | 4篇 |
2023年 | 30篇 |
2022年 | 75篇 |
2021年 | 131篇 |
2020年 | 116篇 |
2019年 | 105篇 |
2018年 | 80篇 |
2017年 | 109篇 |
2016年 | 128篇 |
2015年 | 145篇 |
2014年 | 273篇 |
2013年 | 238篇 |
2012年 | 298篇 |
2011年 | 301篇 |
2010年 | 247篇 |
2009年 | 299篇 |
2008年 | 253篇 |
2007年 | 268篇 |
2006年 | 254篇 |
2005年 | 221篇 |
2004年 | 201篇 |
2003年 | 177篇 |
2002年 | 149篇 |
2001年 | 124篇 |
2000年 | 118篇 |
1999年 | 110篇 |
1998年 | 63篇 |
1997年 | 61篇 |
1996年 | 35篇 |
1995年 | 36篇 |
1994年 | 37篇 |
1993年 | 18篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
排序方式: 共有4741条查询结果,搜索用时 62 毫秒
11.
12.
针对跨境电商客户订单的多品类且数量不稳定的特点,对跨境电商保税仓库拣货流程进行分析与优化。采用订单动态时间窗分拣策略,并在仓库拣货路径优化的基础上,建立了跨境电商保税仓库拣货模型。最后应用于某公司跨境电商保税仓库管理系统中,取得了较好的预期效果。 相似文献
13.
14.
An anti-fatigue smart paste, which consists of fine alumina particles and silicone grease with low viscosity, was applied to a bolt hole (and its periphery in some cases) in a steel plate specimen, and the effects of the smart paste on automatic restraint and visual detection of fatigue crack growth were experimentally investigated through fatigue tests. Fractographic observations using a scanning electron microscope were also carried out. As a result, approximately 20~410% increase in failure life was produced by the wedge effect of the alumina particles in the smart paste. When the smart paste was applied, remarkable black colour developed in the white paste along the paths of crack growth, exceedingly facilitating the visual detection of the crack growth. 相似文献
15.
《岩石力学与岩土工程学报(英文版)》2022,14(6):1872-1884
In deep ground engineering, the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity. However, the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature. In this study, taking Muzhailing highway tunnel as the background, physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity (TWIP) steel used for rock bolt. The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling. The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface. The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate. There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning. The high pretension (>600 MPa or 224 kN) can help bolt rod steel resist deformation-softening behavior, especially at low loading rate (<10?1 MPa/s or 10?2 kN/s). The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario. The results provide the theoretical basis and technical support for practical applications. 相似文献
16.
《Journal of the European Ceramic Society》2022,42(8):3634-3643
Novel AlN-SiC-C refractories were fabricated by nitrogen gas-pressure sintering using single Al4SiC4 as raw-material. The high nitrogen pressure is essential and effective for the nitridation because it contributes to the diffusion of the nitrogen atoms into the interior matrix of Al4SiC4 specimen. Different from traditional carbon-containing refractories and ceramic bonded carbon materials (CBCs), the resulted products possess a honeycomb microstructure consisting of interlocked structure of worm-like SiC and C particles with a AlN ceramic boundary. AlN-SiC nanoparticles and aluminum carbonitride particles (Al-C-Ns) were formed at the interface between AlN-rich and C/SiC-rich area, which acted as transition phases that make these two areas combined tightly. The as-prepared AlN-SiC-C refractories at 1700 ℃ by a 20 atm pressure showed a relative density of 75.8%, combining a bulk density of 2.20 g/cm3 with a flexural strength of 120.9 MPa. Furthermore, the potential reaction mechanism responsible for fabrication of AlN-SiC-C refractories was revealed. 相似文献
17.
18.
Adhesively bonded joints have been extensively employed in the aeronautical and automotive industries to join thin-layer materials for developing lightweight components. To strengthen the structural integrity of joints, it is critical to estimate and improve joint failure loads effectually. To accomplish the aforementioned purpose, this paper presents a novel deep neural network (DNN) model-enabled approach, and a single lap joint (SLJ) design is used to support research development and validation. The approach is innovative in the following aspects: (i) the DNN model is reinforced with a transfer learning (TL) mechanism to realise an adaptive prediction on a new SLJ design, and the requirement to re-create new training samples and re-train the DNN model from scratch for the design can be alleviated; (ii) a fruit fly optimisation (FFO) algorithm featured with the parallel computing capability is incorporated into the approach to efficiently optimise joint parameters based on joint failure load predictions. Case studies were developed to validate the effectiveness of the approach. Experimental results demonstrate that, with this approach, the number of datasets and the computational time required to re-train the DNN model for a new SLJ design were significantly reduced by 92.00% and 99.57% respectively, and the joint failure load was substantially increased by 9.96%. 相似文献
19.
结构胶胶接接头耐久性的研究进展 总被引:1,自引:0,他引:1
结构胶是胶黏剂中具有高强度、耐高温、高耐久特性的一类胶黏剂的总称,主要用于部件中承受载荷的胶接连接。胶接接头的耐久性能是结构胶应用中的一个重要指标。主要从影响胶接接头耐久性的内在因素和外在因素以及实验室研究方法对结构胶胶接接头耐久性的研究进展进行综述。 相似文献
20.
基于垫片时效泄漏模型和应力强度干涉模型建立螺栓法兰连接的模糊可靠性模型。通过对极限状态方程进行模糊化处理,得到了螺栓法兰连接模糊可靠性计算模型,将Monte-Carlo法和有限元法相结合,提出基于有限元的螺栓法兰连接模糊可靠性计算方法,并对该方法进行验证。 相似文献