全文获取类型
收费全文 | 10658篇 |
免费 | 223篇 |
国内免费 | 174篇 |
专业分类
电工技术 | 249篇 |
技术理论 | 2篇 |
综合类 | 663篇 |
化学工业 | 1083篇 |
金属工艺 | 748篇 |
机械仪表 | 918篇 |
建筑科学 | 1623篇 |
矿业工程 | 556篇 |
能源动力 | 449篇 |
轻工业 | 571篇 |
水利工程 | 177篇 |
石油天然气 | 624篇 |
武器工业 | 80篇 |
无线电 | 380篇 |
一般工业技术 | 1557篇 |
冶金工业 | 424篇 |
原子能技术 | 75篇 |
自动化技术 | 876篇 |
出版年
2024年 | 3篇 |
2023年 | 54篇 |
2022年 | 101篇 |
2021年 | 126篇 |
2020年 | 162篇 |
2019年 | 101篇 |
2018年 | 110篇 |
2017年 | 125篇 |
2016年 | 214篇 |
2015年 | 248篇 |
2014年 | 425篇 |
2013年 | 482篇 |
2012年 | 518篇 |
2011年 | 689篇 |
2010年 | 609篇 |
2009年 | 557篇 |
2008年 | 500篇 |
2007年 | 661篇 |
2006年 | 593篇 |
2005年 | 557篇 |
2004年 | 554篇 |
2003年 | 577篇 |
2002年 | 497篇 |
2001年 | 472篇 |
2000年 | 395篇 |
1999年 | 398篇 |
1998年 | 362篇 |
1997年 | 269篇 |
1996年 | 206篇 |
1995年 | 155篇 |
1994年 | 98篇 |
1993年 | 57篇 |
1992年 | 46篇 |
1991年 | 27篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
针对现有的混凝土裂缝检测算法在各种复杂环境中检测精度不够、鲁棒性不强的问题,根据深度学习理论和U-net模型,提出一种全U型网络的裂缝检测算法。首先,依照原U-net模型路线构建网络;然后,在每个池化层后都进行一次上采样,恢复其在池化层之前的特征图规格,并将其与池化之前的卷积层进行融合,将融合之后的特征图作为新的融合层与原U-net网络上采样之后的网络层进行融合;最后,为了验证算法的有效性,在测试集中进行实验。结果表明,所提算法的平均精确率可达到83.48%,召回率为85.08%,F1为84.11%,相较于原U-net分别提升了1.48%,4.68%和3.29%,在复杂环境中也能提取完整裂缝,保证了裂缝检测的鲁棒性。 相似文献
2.
《Ceramics International》2022,48(18):25984-25995
Design of architectured composites with layered-ordered structure can solve the strength-toughness mismatch problem of structural materials. In the present study, heterostructure Ti6Al4V/TiAl laminated composite sheets with different thicknesses of interface layer and TiAl composite layer were successfully produced by hot-pressing technology. The effects of interface regulation and laminated structure on their mechanical properties, crack propagation, and fracture behavior were studied. The results indicated that compressive strength of the sheets increased with the decrease in interface thickness. Compressive strength of TiAl composite sheet with thicker composite layer reached 1481.55 MPa at the arrester orientation with sintering holding time of 40 min, which was 25.96% higher than that of the sheet obtained at 120 min. Analysis indicated that the interface area transferred stress through slip bands and through-interface cracks. Compressive strength at the divider orientation reached 1443.06 MPa, which was 45.78% higher than that of the sheet obtained at 120 min. In this case, the interface area transferred stress through slip bands and along-interface cracks. For TiAl composite sheets with thinner composite layer, compressive strength was further improved to 1631.01 MPa and 1594.66 MPa at the arrester and divider orientations with sintering holding time of 40 min, respectively. The ductile metal layer exerted a significant toughening effect. Both interface regulation and laminated structure transformation could enhance the hetero-deformation induced (HDI) strengthening and improve the comprehensive mechanical properties of the composite sheets. 相似文献
3.
In the first critical assessment of knowledge economy dynamic paths in Africa and the Middle East, but for a few exceptions, we find overwhelming support for diminishing cross-country disparities in knowledge-based economy dimensions. The paper employs all the four components of the World Bank's Knowledge Economy Index (KEI): economic incentives, innovation, education, and information infrastructure. The main finding suggests that sub-Saharan African (SSA) and the Middle East and North African (MENA) countries with low levels of KE dynamics and catching-up their counterparts of higher KE levels. We provide the speeds of integration and time necessary to achieve full (100%) integration. Policy implications are also discussed. 相似文献
4.
The development of a sustainable energy system throughout an enterprise is a complex task, which requires an agile holistic approach. Such an approach needs to include a variety of objectives including energy strategy formation and strategic decision-making, which are directly related to the analysis and management of the main areas of sustainable development:The economic, technological, environmental, and social. These multidimensional requirements of sustainability are often difficult to achieve within the enterprise, because these aspects are interrelated and influenced by various internal and external environment factors. This paper first reviews the main challenges for an energy system, and then demonstrates how a strategic agile enterprise architecture driven approach could effectively guide the sustainable energy system development. The study presented in this paper provides a holistic approach that contributes to the advancement and usage of literature dealing with issues of sustainable energy system development and agile enterprise architecture, which has not been discussed before to any great extent. 相似文献
5.
The paper concerns an analysis of an equilibrium problem for 2D elastic body with two semirigid inclusions. It is assumed that inclusions have a joint point, and we investigate a junction problem for these inclusions. The existence of solutions is proved, and different equivalent formulations of the problem are proposed. We investigate a convergence to infinity of a rigidity parameter of the semirigid inclusion. It is proved that in the limit, we obtain an equilibrium problem for the elastic body with a rigid inclusion and a semirigid one. A parameter identification problem is investigated. In particular, the existence of a solution to a suitable optimal control problem is proved. 相似文献
7.
8.
提出在县市级广电宽带数据网络的建设过程中,要着眼业务发展,突出高扩展性,构建基于标准、扩展灵活的主干网,实现网络建设的可持续性发展,并结合实际,从核心设备、端口、中继带宽、网络业务4个方面对扩展能力进行了阐述. 相似文献
9.
10.
新产品研发是建陶企业可持续发展的核心 总被引:2,自引:0,他引:2
新世纪我国建陶企业在整个国民经济的带动下将进一步发展,入世后经济全球化的市场竞争格局,建陶企业只有走新产口研发之路,严格企业管理,才会在日趋激烈的市场竞争中得以生存和可持续发展。 相似文献