全文获取类型
收费全文 | 301164篇 |
免费 | 22633篇 |
国内免费 | 11302篇 |
专业分类
电工技术 | 16429篇 |
技术理论 | 25篇 |
综合类 | 17211篇 |
化学工业 | 51775篇 |
金属工艺 | 15466篇 |
机械仪表 | 18006篇 |
建筑科学 | 24101篇 |
矿业工程 | 7654篇 |
能源动力 | 8486篇 |
轻工业 | 18226篇 |
水利工程 | 4743篇 |
石油天然气 | 16405篇 |
武器工业 | 1976篇 |
无线电 | 37184篇 |
一般工业技术 | 38095篇 |
冶金工业 | 15861篇 |
原子能技术 | 3177篇 |
自动化技术 | 40279篇 |
出版年
2024年 | 970篇 |
2023年 | 4355篇 |
2022年 | 7963篇 |
2021年 | 10889篇 |
2020年 | 8102篇 |
2019年 | 6867篇 |
2018年 | 7682篇 |
2017年 | 8770篇 |
2016年 | 7986篇 |
2015年 | 10512篇 |
2014年 | 13658篇 |
2013年 | 17595篇 |
2012年 | 17878篇 |
2011年 | 20152篇 |
2010年 | 17161篇 |
2009年 | 16884篇 |
2008年 | 16365篇 |
2007年 | 15617篇 |
2006年 | 16271篇 |
2005年 | 14550篇 |
2004年 | 9894篇 |
2003年 | 8699篇 |
2002年 | 7861篇 |
2001年 | 7241篇 |
2000年 | 7508篇 |
1999年 | 8657篇 |
1998年 | 7876篇 |
1997年 | 6613篇 |
1996年 | 6029篇 |
1995年 | 5071篇 |
1994年 | 4162篇 |
1993年 | 3279篇 |
1992年 | 2552篇 |
1991年 | 1933篇 |
1990年 | 1554篇 |
1989年 | 1317篇 |
1988年 | 1019篇 |
1987年 | 737篇 |
1986年 | 551篇 |
1985年 | 467篇 |
1984年 | 278篇 |
1983年 | 251篇 |
1982年 | 229篇 |
1981年 | 194篇 |
1980年 | 171篇 |
1979年 | 128篇 |
1978年 | 88篇 |
1977年 | 88篇 |
1976年 | 117篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
World Wide Web - The wide spread use of positioning and photographing devices gives rise to a deluge of traffic trajectory data (e.g., vehicle passage records and taxi trajectory data), with each... 相似文献
92.
93.
94.
Jie-Long He An-Te Chen Jyong-Huei Lee Shih-Kang Fan 《International journal of molecular sciences》2015,16(9):22319-22332
The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed. 相似文献
95.
96.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
97.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
98.
A first‐principles‐based effective Hamiltonian is developed and employed to investigate finite‐temperature structural properties of a prototype of perovskite halides, that is CsPbI3. Such simulations, when using first‐principles‐extracted coefficients, successfully reproduce the existence of an orthorhombic Pnma state and its iodine octahedral tilting angles around room temperature. However, they also yield a direct transformation from Pnma to cubic upon heating, unlike measurements that reported the occurrence of an intermediate long‐range‐tilted tetragonal P4/mbm phase in‐between the orthorhombic and cubic phases. Such disagreement, which may cast some doubts about the extent to which first‐principle methods can be trusted to mimic hybrid perovskites, can be resolved by “only” changing one short‐range tilting parameter in the whole set of effective Hamiltonian coefficients. In such a case, some reasonable values of this specific parameter result in the predictions that i) the intermediate P4/mbm state originates from fluctuations over many different tilted states; and ii) the cubic phase is highly locally distorted and develops strong transverse antiphase correlation between first‐nearest neighbor iodine octahedral tiltings, before undergoing a phase transition to P4/mbm under cooling. 相似文献
99.
Lin Haicheng Huang Wantong Zhao Kun Qiao Shuang Liu Zheng Wu Jian Chen Xi Ji Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam... 相似文献
100.
针对传统低压回路电阻测试仪只能在被测设备停电时使用的一大限制,本文提出并设计了一种新型低压回路电阻测试仪。该仪器可在低压设备运行状态下对其回路电阻进行测量,在保证测量精度的前提下减少了设备停电率,大大提高了工作效率。 相似文献