全文获取类型
收费全文 | 326442篇 |
免费 | 26427篇 |
国内免费 | 16508篇 |
专业分类
电工技术 | 19067篇 |
技术理论 | 51篇 |
综合类 | 39891篇 |
化学工业 | 46866篇 |
金属工艺 | 16084篇 |
机械仪表 | 16553篇 |
建筑科学 | 40012篇 |
矿业工程 | 15922篇 |
能源动力 | 16051篇 |
轻工业 | 22234篇 |
水利工程 | 14253篇 |
石油天然气 | 13524篇 |
武器工业 | 3032篇 |
无线电 | 21095篇 |
一般工业技术 | 26938篇 |
冶金工业 | 18720篇 |
原子能技术 | 3121篇 |
自动化技术 | 35963篇 |
出版年
2024年 | 984篇 |
2023年 | 3490篇 |
2022年 | 7453篇 |
2021年 | 8901篇 |
2020年 | 8437篇 |
2019年 | 7251篇 |
2018年 | 6829篇 |
2017年 | 8361篇 |
2016年 | 9442篇 |
2015年 | 10351篇 |
2014年 | 18017篇 |
2013年 | 16897篇 |
2012年 | 21519篇 |
2011年 | 23614篇 |
2010年 | 18541篇 |
2009年 | 19044篇 |
2008年 | 17612篇 |
2007年 | 22807篇 |
2006年 | 21376篇 |
2005年 | 18625篇 |
2004年 | 15767篇 |
2003年 | 14081篇 |
2002年 | 11760篇 |
2001年 | 9861篇 |
2000年 | 8328篇 |
1999年 | 6874篇 |
1998年 | 5309篇 |
1997年 | 4540篇 |
1996年 | 4168篇 |
1995年 | 3497篇 |
1994年 | 3127篇 |
1993年 | 2300篇 |
1992年 | 2036篇 |
1991年 | 1485篇 |
1990年 | 1256篇 |
1989年 | 1099篇 |
1988年 | 873篇 |
1987年 | 592篇 |
1986年 | 442篇 |
1985年 | 384篇 |
1984年 | 354篇 |
1983年 | 256篇 |
1982年 | 230篇 |
1981年 | 180篇 |
1980年 | 150篇 |
1979年 | 120篇 |
1978年 | 65篇 |
1977年 | 73篇 |
1976年 | 58篇 |
1975年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
《Measurement》2015
The evaluation of functional features of manufactured workpieces is based on GO- and NO-GO-test results, which are obtained by comparing measured geometric characteristics with nominal dimensions and tolerances specified by the designer. These geometrical specifications are based on a tolerancing system, which was originally defined for the function mating capability. Against the background of upcoming lots of other new functions (like reduction of flow resistance, light absorption, reduction of friction, diffraction of light, self-cleaning or mass transmission) are to be realized with our products – particularly by micro- and nano scaled features. If the verification process will deliver the prediction of the achievable degree of functionality, the usability of a part can be assessed more accurately and in consequence quality and economics can be improved. So, a new principle for tolerancing and verifying turns out to be necessary. In this paper the fundamental deficit of the actual tolerancing and specification systems GPS and ASME Y14.5 is derived and the path for enlarging the system by preposing a functional model is shown. To verify the functional capability of the workpieces an approach based on simulations done with the parameterized mathematical–physical model of the function is suggested. Advantages of this approach will be discussed and demonstrated by examples with microstructured inking rolls, crankshafts and injection valves. 相似文献
82.
SPEEK/cSMM membrane for simultaneous electricity generation and wastewater treatment in microbial fuel cell
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
83.
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
84.
This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines. 相似文献
85.
86.
有机化学是化学化工、材料、制药、食品等多个专业的基础课程,在其教学过程中,教师可以根据课程的内容及特点,分别以有机化学发展中的重大历史事件、有机化物的性质及有机反应为引导,开展学生的思想品德教育,加强课程思政建设。 相似文献
87.
88.
冯鹏一 《信息通信技术与政策》2020,(1):12-15
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。 相似文献
89.
90.
We report a simple processing method to simultaneously improve the efficiency and stability of organic solar cells (OSCs). Poly(4-styrene sulfonate)-doped poly(3,4-ethylenedioxy-thiophene (PEDOT:PSS), widely used as hole transport layer (HTL) in OSCs, tends to accelerate the degradation of devices because of its hygroscopic and acidic properties. In this regard, we have modified PEDOT:PSS to reduce its hygroscopic and acidic properties through a condensation reaction between PEDOT:PSS and poly(ethylene glycol) methyl ether (PEGME) in order to improve the efficiency and stability of OSCs. As a result, the power conversion efficiency (PCE) increased by 21%, from 2.57% up to 3.11%. A better energy level alignment by the reduced work function of the modified PEDOT:PSS with a highest occupied molecular orbital (HOMO) level of poly(3-hexylthiophene-2,5-diyl) (P3HT) is considered the origin of the improved the efficiency. The half-life of OSCs with PEDOT:PSS modified with PEGME buffer layer also increased up to 3.5 times compared to that of devices with pristine PEDOT:PSS buffer layer. 相似文献