全文获取类型
收费全文 | 101808篇 |
免费 | 10227篇 |
国内免费 | 6293篇 |
专业分类
电工技术 | 6294篇 |
技术理论 | 6篇 |
综合类 | 10709篇 |
化学工业 | 14175篇 |
金属工艺 | 6926篇 |
机械仪表 | 6288篇 |
建筑科学 | 19197篇 |
矿业工程 | 3537篇 |
能源动力 | 3098篇 |
轻工业 | 5249篇 |
水利工程 | 2489篇 |
石油天然气 | 4476篇 |
武器工业 | 1006篇 |
无线电 | 7199篇 |
一般工业技术 | 12092篇 |
冶金工业 | 3691篇 |
原子能技术 | 664篇 |
自动化技术 | 11232篇 |
出版年
2024年 | 476篇 |
2023年 | 1708篇 |
2022年 | 2959篇 |
2021年 | 3351篇 |
2020年 | 3436篇 |
2019年 | 2844篇 |
2018年 | 2653篇 |
2017年 | 3314篇 |
2016年 | 3391篇 |
2015年 | 3627篇 |
2014年 | 6296篇 |
2013年 | 5525篇 |
2012年 | 6987篇 |
2011年 | 7782篇 |
2010年 | 5995篇 |
2009年 | 6396篇 |
2008年 | 5924篇 |
2007年 | 6942篇 |
2006年 | 6272篇 |
2005年 | 5419篇 |
2004年 | 4433篇 |
2003年 | 3943篇 |
2002年 | 3341篇 |
2001年 | 2767篇 |
2000年 | 2370篇 |
1999年 | 1969篇 |
1998年 | 1529篇 |
1997年 | 1319篇 |
1996年 | 991篇 |
1995年 | 845篇 |
1994年 | 798篇 |
1993年 | 531篇 |
1992年 | 477篇 |
1991年 | 387篇 |
1990年 | 304篇 |
1989年 | 223篇 |
1988年 | 163篇 |
1987年 | 86篇 |
1986年 | 66篇 |
1985年 | 74篇 |
1984年 | 54篇 |
1983年 | 55篇 |
1982年 | 69篇 |
1981年 | 23篇 |
1980年 | 68篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1975年 | 11篇 |
1959年 | 11篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
探讨了显控台的内涵,提出了显控台的分类方法,阐述了显控台型谱.采用广义和狭义的概念明晰了显控台的基本内涵;采用特征分类法从多个角度对显控台进行了分类和类型识别;通过分析和介绍几种显控台型谱,表明在不同行业和领域中显控台的型谱不一定相同 相似文献
992.
993.
对柱状晶纯镍样品先拉伸后冷轧,用透射电镜和扫描电镜表征其位错结构。在拉伸变形时形成的结构在后续的轧制变形后保持或改变取决于当应变路径改变时开动的滑移系是否发生了改变。当开动的滑移系发生变化时,最终的结构由第二应变路径中开动的滑移系所决定。这些结果为支持已发表的滑移系活动与位错结构的关系提供了进一步的证明。 相似文献
994.
本文提出了一种基于混合晶向硅材料的高性能PMOSFET 器件。采用硅玻键合、化学机械抛光、硅刻蚀和非选择性外延等方法,成功制作了集成有(100)和(110)晶向的混合晶向硅片。基于这种混合晶向材料,成功研制了沟道宽长比为50:8 的PMOSFET器件,器件测试结果表明:制作在(110)晶向上的PMOSFET 器件在低场条件下,电流驱动能力提高了50.7%,最大迁移率增加了150%,是当前见于报道的PMOSFET迁移率提升指标较高的一颗器件。 相似文献
995.
Attribute-based signature (ABS),which could realize fine-grained access control,was considered to be an important method for anonymous authentication in cloud computing.However,normal ABS only provided simple access control through threshold structure and thus could not cope with the large-scale attribute sets of users in the cloud.Moreover,the attribute sets were supervised by only one attribute authority,which increased the cost of computation and storage.The whole system was in danger of collapsing once the attribute authority was breached.Aiming at tackling the problems above,a novel scheme,was proposed called multi-authority ABS supporting dendritic access structure which supported any AND,OR and threshold gates and affords more flexible access control.Meanwhile,the attribute sets of users were classified by diverse attribute authorities which reduced the overhead and the risk of systems.Besides,the scheme is proved to be selective predicate chosen message attack secure in the random oracle model. 相似文献
996.
Zhaoling Li Miaomiao Zhu Jiali Shen Qian Qiu Jianyong Yu Bin Ding 《Advanced functional materials》2020,30(6)
With the rapid advancement in artificial intelligence, wearable electronic skins have attracted substantial attention. However, the fabrication of such devices with high elasticity and breathability is still a challenge and highly desired. Here, a route to develop an all‐fiber structured electronic skin with a scalable electrospinning fabrication technique is reported. The fabricated electronic skin is demonstrated to exhibit high pressure sensing with a sensitivity of 0.18 V kPa?1 in the detection range of 0–175 kPa. This wearable device could maintain prominent sensing performance and mechanical stability in the presence of large deformation, even when the elastic deformation is up to 50%. The electronic skin is easily conformable on different desired objects for real‐time spatial mapping and long‐term tactile sensing. Besides, it possesses high gas permeability with a water vapor transmittance rate of 10.26 kg m?2 d?1. More importantly, the electronic skin is capable of working in a self‐powered manner and even serves as a reliable power source to effectively drive small electronics. Possessing several compelling features, such as high sensitivity, high elasticity, high breathability as well as being self‐powered and scalable in fabrication, the presented device paves a pathway for smart electronic skins. 相似文献
997.
Katrin Ortstein Sebastian Hutsch Alexander Hinderhofer Jrn Vahland Martin Schwarze Sebastian Schellhammer Martin Hodas Thomas Geiger Hans Kleemann Holger F. Bettinger Frank Schreiber Frank Ortmann Karl Leo 《Advanced functional materials》2020,30(32)
In modern electronics, it is essential to adapt band structures by adjusting energy levels and band gaps. At first sight, this “band structure engineering” seems impossible in organic semiconductors, which usually exhibit localized electronic states instead of Bloch bands. However, the strong Coulomb interaction in organic semiconductors allows for a continuous shift of the ionization energy (IE) over a wide range by mixing molecules with halogenated derivatives that exhibit different quadrupole moments. Here, this effect of energy level engineering on blends of pentacene and two fluorinated derivatives, in which the position but not the number of fluorine atoms differ, is studied. Structural investigations confirm that pentacene forms intermixed phases in blends with the fluorinated species. The investigation of electronic properties and simulations reveals a much larger shift of the ionization energy (1.5 eV) than in previous studies, allowing to test this model in a range not investigated so far, and emphasizing the role of the position of the halogen atoms. The tuning effect is preserved in electronic devices such as field‐effect transistors and significantly influences device characteristics. 相似文献
998.
采用溶胶-凝胶(sol-gel)旋涂法在常规玻璃衬底 上生长了In掺杂浓度分别为1at%、2at%、3at%、4at%、5at%的ZnO薄膜。借助X射线衍射仪(X RD)、扫描电子显微镜(SEM)、紫外- 可见分光光度计(UV-Vis)对样品的晶粒生长、结构以及光学性能进行表征。结果如下:所 制 备的薄膜均沿(002)方向择优生长,且随着In3+掺杂浓度增加 ,衍射峰的峰型及半高宽均呈 先降低后升高的趋势;In3+掺入后,ZnO薄膜晶粒由原来的六边形状发展成类似蠕虫 状,同 时粒径变小且大小不一;与本征样品相比,掺杂后的ZnO光透过率提高了10%,且吸收边向短 波长方向偏移,同时随着In3+的掺入,薄膜的光学带隙值从3.49 eV增加到3.80 eV。当In3+掺 杂浓度为4at%时,薄膜(002)峰的峰形最为尖锐、峰值最大,晶粒较为均匀、 晶格间距更小,光透过率最高,光学带隙值相对较大为3.77 eV。 相似文献
999.
Causal consistency is one of the important projects to ensure data consistency in distributed storage.The current research focuses on causal consistency including optimization of clock method,design of the protocol and the optimization of operation transaction sequence.In the actual cloud environment,in addition to clock skew and query amplification,there are also insecure factors such as Trojans and untrusted third parties,which will destroy the causal consistency metadata stored by users,and the consistency of user’s operating results,even affect the availability of the storage environment.From the perspective of performance improvement and security in distributed storage,the clock synchronization,data replications,analysis and design of server protocol,related research progress of the serialization of operational affairs were introduced combined with consensus mechanisms such as blockchain.At the same time,their principlest,advantages,limitations,and different utilities in terms of security constraints were discussed,and then the future development trends and follow-up research directions were point out at last,which would provide a reference and help for the research in this field. 相似文献
1000.