全文获取类型
收费全文 | 99561篇 |
免费 | 11724篇 |
国内免费 | 7987篇 |
专业分类
电工技术 | 8655篇 |
综合类 | 9828篇 |
化学工业 | 12983篇 |
金属工艺 | 6663篇 |
机械仪表 | 6739篇 |
建筑科学 | 7310篇 |
矿业工程 | 3408篇 |
能源动力 | 2468篇 |
轻工业 | 11607篇 |
水利工程 | 3556篇 |
石油天然气 | 3624篇 |
武器工业 | 1285篇 |
无线电 | 10377篇 |
一般工业技术 | 8940篇 |
冶金工业 | 4625篇 |
原子能技术 | 1815篇 |
自动化技术 | 15389篇 |
出版年
2024年 | 510篇 |
2023年 | 1505篇 |
2022年 | 3938篇 |
2021年 | 5065篇 |
2020年 | 3611篇 |
2019年 | 2623篇 |
2018年 | 2796篇 |
2017年 | 3156篇 |
2016年 | 2761篇 |
2015年 | 4434篇 |
2014年 | 5671篇 |
2013年 | 6819篇 |
2012年 | 8492篇 |
2011年 | 8964篇 |
2010年 | 8550篇 |
2009年 | 7883篇 |
2008年 | 8104篇 |
2007年 | 7721篇 |
2006年 | 6545篇 |
2005年 | 5208篇 |
2004年 | 3620篇 |
2003年 | 2470篇 |
2002年 | 2309篇 |
2001年 | 2009篇 |
2000年 | 1560篇 |
1999年 | 660篇 |
1998年 | 492篇 |
1997年 | 306篇 |
1996年 | 233篇 |
1995年 | 174篇 |
1994年 | 132篇 |
1993年 | 137篇 |
1992年 | 88篇 |
1991年 | 70篇 |
1990年 | 76篇 |
1989年 | 87篇 |
1988年 | 43篇 |
1987年 | 45篇 |
1986年 | 40篇 |
1985年 | 35篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 21篇 |
1977年 | 46篇 |
1976年 | 92篇 |
1959年 | 15篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
11.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
12.
Juan Ding Yong He Shenhe Fu Xiangsheng Xie Haowen Liang Jianying Zhou 《Journal of the Society for Information Display》2022,30(2):159-167
Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution. 相似文献
13.
不同给液方式对铜电解过程中有重要的影响,不同的循环方式会影响槽内温度分布、电解液成分及阳极泥沉降等,因此,根据铜电解生产不同情况的需要,分析对比了多种给液方式在贵冶电解车间的应用,总结了这几种给液方式的优缺点和适用条件。 相似文献
14.
15.
16.
Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved. 相似文献
17.
18.
进入新发展阶段,中国水资源安全保障需要以“节水优先、空间均衡、系统治理、两手发力”治水思路为指导,厘清问题、研判趋势、优化对策,支撑新阶段水利高质量发展。本文在全面分析我国水资源安全保障存在的突出问题与面临形势基础上,阐述了新发展阶段中国水资源安全保障的基本思路与战略路径,从保证资源安全、构建国家水网、强化供水保障、建设美丽河湖、改善水环境质量等方面提出了战略对策和需要进一步回答的重大问题,以期为完善新发展阶段中国水资源安全保障战略,全面提高国家水资源安全保障能力提供有力支撑。 相似文献
19.
Dr. Alejandra A. Carriles Alberto Mills Dr. María-José Muñoz-Alonso Dr. Dolores Gutiérrez Dr. Juan M. Domínguez Prof. Dr. Juan A. Hermoso Prof. Dr. Federico Gago 《Chembiochem : a European journal of chemical biology》2021,22(2):374-391
Spontaneous mutations in the EEF1A2 gene cause epilepsy and severe neurological disabilities in children. The crystal structure of eEF1A2 protein purified from rabbit skeletal muscle reveals a post-translationally modified dimer that provides information about the sites of interaction with numerous binding partners, including itself, and maps these mutations onto the dimer and tetramer interfaces. The spatial locations of the side chain carboxylates of Glu301 and Glu374, to which phosphatidylethanolamine is uniquely attached via an amide bond, define the anchoring points of eEF1A2 to cellular membranes and interorganellar membrane contact sites. Additional bioinformatic and molecular modeling results provide novel structural insight into the demonstrated binding of eEF1A2 to SH3 domains, the common MAPK docking groove, filamentous actin, and phosphatidylinositol-4 kinase IIIβ. In this new light, the role of eEF1A2 as an ancient, multifaceted, and articulated G protein at the crossroads of autophagy, oncogenesis and viral replication appears very distant from the “canonical” one of delivering aminoacyl-tRNAs to the ribosome that has dominated the scene and much of the thinking for many decades. 相似文献
20.
连续多跨的二层无粘结预应力混凝土框架结构按照改造需要拆成单跨框架结构,且增加一层。某一方向的预应力钢筋将全部切断。通过对多种改造加固方案的比选,最终确定了无粘结预应力钢绞线应力释放和重张拉法。通过与专业施工单位的共同配合,顺利完成了该工程预应力拆除改造关键技术,施工监测表明,通过施工监测表明整个拆改过程变形合理可控。本项目取得了较好的经济效应,且是改造项目中的绿色工程。 相似文献