全文获取类型
收费全文 | 105357篇 |
免费 | 11899篇 |
国内免费 | 6678篇 |
专业分类
电工技术 | 8582篇 |
技术理论 | 8篇 |
综合类 | 8521篇 |
化学工业 | 15787篇 |
金属工艺 | 5777篇 |
机械仪表 | 7034篇 |
建筑科学 | 8746篇 |
矿业工程 | 3477篇 |
能源动力 | 3329篇 |
轻工业 | 8227篇 |
水利工程 | 2549篇 |
石油天然气 | 5051篇 |
武器工业 | 1305篇 |
无线电 | 13075篇 |
一般工业技术 | 11081篇 |
冶金工业 | 4163篇 |
原子能技术 | 1428篇 |
自动化技术 | 15794篇 |
出版年
2024年 | 595篇 |
2023年 | 1964篇 |
2022年 | 3864篇 |
2021年 | 5298篇 |
2020年 | 3821篇 |
2019年 | 3085篇 |
2018年 | 3380篇 |
2017年 | 3787篇 |
2016年 | 3440篇 |
2015年 | 4937篇 |
2014年 | 6051篇 |
2013年 | 7097篇 |
2012年 | 8233篇 |
2011年 | 8318篇 |
2010年 | 7761篇 |
2009年 | 7352篇 |
2008年 | 7007篇 |
2007年 | 6449篇 |
2006年 | 6075篇 |
2005年 | 4774篇 |
2004年 | 3405篇 |
2003年 | 2621篇 |
2002年 | 2691篇 |
2001年 | 2244篇 |
2000年 | 1841篇 |
1999年 | 1638篇 |
1998年 | 1157篇 |
1997年 | 959篇 |
1996年 | 895篇 |
1995年 | 709篇 |
1994年 | 592篇 |
1993年 | 393篇 |
1992年 | 356篇 |
1991年 | 251篇 |
1990年 | 194篇 |
1989年 | 166篇 |
1988年 | 103篇 |
1987年 | 70篇 |
1986年 | 61篇 |
1985年 | 42篇 |
1984年 | 38篇 |
1983年 | 23篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 33篇 |
1979年 | 19篇 |
1977年 | 10篇 |
1976年 | 20篇 |
1959年 | 11篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Wang Hay Kan Chenxi Wei Dongchang Chen Tao Bo Bao‐Tian Wang Yan Zhang Yangchao Tian Jun‐Sik Lee Yijin Liu Guoying Chen 《Advanced functional materials》2019,29(17)
Lithium‐rich disordered rock‐salt oxides have attracted great interest owing to their promising performance as Li‐ion battery cathodes. While experimental and theoretical efforts are critical in advancing this class of materials, a fundamental understanding of key property changes upon Li extraction is largely missing. In the present study, single‐crystal synthesis of a new disordered rock‐salt cathode material, Li1.3Ta0.3Mn0.4O2 (LTMO), and its use as a model compound to investigate Li concentration–driven evolution of local cationic ordering, charge compensation, and chemical distribution are reported. Through the combined use of 2D and 3D X‐ray nanotomography, it is shown that Li removal accompanied by oxygen oxidation is correlated with the development of morphological defects such as particle cracking. Chemical heterogeneity, quantified by subparticle level distribution of Mn valence state, is minimal during Mn redox, which drastically increases upon the formation of cracks during oxygen redox. Density functional theory and bond valence sum mismatch calculations reveal the presence of local short‐range ordering in the pristine oxide, which gradually disappears along with the extraction of Li. The study suggests that with cycling the transformation into true cation–disordered state can be expected, which likely impacts the voltage profile and obtainable energy density of the oxide cathodes. 相似文献
42.
43.
This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach. 相似文献
44.
煤电平均供电煤耗作为评价能源系统效率的指标已在行业内广泛应用。但该项指标无法很好地反映一个国家、地区的用电结构与用电能耗水平。为此,参照行业内普遍采用的火电厂发电煤耗和供电煤耗指标,定义“综合用电煤耗”,即用户每用1 kW?h电“消耗”的标准煤量(单位:g/(kW?h))。在此基础上,提出“综合发电煤耗”与“综合供电煤耗”的概念,形成完整的指标评价体系。对近年典型省份指标值的研究表明,该指标体系能够很好地反映供给侧国家、省区或企业的发电结构与电能生产能耗水平。这一指标体系能够为正确理解和计算用电、输电与电能替代项目的化石能源消耗量及其排放量提供依据。 相似文献
45.
Debin Wang Jingsong Liu Mengshi Zeng Chunmei Zhang Huiqin Li Hongtao Yu Ying Yuan Shuren Zhang 《Journal of the American Ceramic Society》2019,102(7):4029-4037
(1-x)Sr0.7Pb0.15Bi0.1TiO3-xBi4Ti3O12 ((1-x)SPBT-xBIT, x = 0-0.125) bulk ceramics were developed and calcined via the solid-state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT-0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT-0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT-0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range. 相似文献
46.
主要阐述在距离台技术大楼2 km远的海盐一家门频道采、编、播系统的构建。整个系统的搭建,充分考虑了时间、空间、距离等各方面的要求,突出异地构建的特点,融合了电视台的节目录制、安全播出、计算机网络、远程控制等多方面技术。 相似文献
47.
48.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
49.
50.
Multimedia Tools and Applications - In Wyner-Ziv (WZ) video coding, decoder side information (SI) takes a key role in a WZ video codec among other building blocks. In this paper, we review the... 相似文献