全文获取类型
收费全文 | 186228篇 |
免费 | 19152篇 |
国内免费 | 11604篇 |
专业分类
电工技术 | 15372篇 |
技术理论 | 7篇 |
综合类 | 15515篇 |
化学工业 | 26061篇 |
金属工艺 | 11319篇 |
机械仪表 | 12605篇 |
建筑科学 | 15797篇 |
矿业工程 | 6111篇 |
能源动力 | 5539篇 |
轻工业 | 14143篇 |
水利工程 | 4537篇 |
石油天然气 | 9176篇 |
武器工业 | 2161篇 |
无线电 | 22642篇 |
一般工业技术 | 18862篇 |
冶金工业 | 7562篇 |
原子能技术 | 2104篇 |
自动化技术 | 27471篇 |
出版年
2024年 | 992篇 |
2023年 | 3087篇 |
2022年 | 6179篇 |
2021年 | 8476篇 |
2020年 | 6363篇 |
2019年 | 4921篇 |
2018年 | 5433篇 |
2017年 | 6421篇 |
2016年 | 5596篇 |
2015年 | 8344篇 |
2014年 | 10467篇 |
2013年 | 12291篇 |
2012年 | 14288篇 |
2011年 | 14806篇 |
2010年 | 13764篇 |
2009年 | 12915篇 |
2008年 | 12832篇 |
2007年 | 12113篇 |
2006年 | 11018篇 |
2005年 | 8755篇 |
2004年 | 6204篇 |
2003年 | 5184篇 |
2002年 | 5017篇 |
2001年 | 4400篇 |
2000年 | 3600篇 |
1999年 | 2922篇 |
1998年 | 1942篇 |
1997年 | 1630篇 |
1996年 | 1501篇 |
1995年 | 1271篇 |
1994年 | 1048篇 |
1993年 | 697篇 |
1992年 | 538篇 |
1991年 | 395篇 |
1990年 | 332篇 |
1989年 | 289篇 |
1988年 | 193篇 |
1987年 | 130篇 |
1986年 | 116篇 |
1985年 | 53篇 |
1984年 | 54篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 49篇 |
1980年 | 61篇 |
1979年 | 30篇 |
1978年 | 14篇 |
1977年 | 22篇 |
1976年 | 13篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
1.
2.
通过密度测定和DSC热分析,观测了超高分子量聚乙烯的辐射效应。实验结果表明:在吸收剂量0—1.13MGy范围内,密度随吸收剂量的增加而增大,熔化热和熔点也有所增加,特别是在低剂量范围内增加十分明显。以上结果都说明,超高分子量聚乙烯在辐照过程中,结晶在完善或有新的结晶形成 相似文献
3.
LeeSiewWei 《水利水电快报》2002,23(19):1-5
在英国伦敦多克兰斯轻便铁路刘易舍姆延长线(DLR-LWE)双隧道掘进工程中,在敏感建筑物下进行了补偿灌浆,以防止隧道开挖引起的过度沉降。但是,过度灌浆也会对隧道下部施加超越。介绍了由隧道掘进承包商所编辑的关于地面和建筑物沉降以及由补偿灌浆引起的隧道衬砌变形的详细现场监测数据。 相似文献
4.
恢复城市水环境的自然生态 总被引:5,自引:0,他引:5
为了确保城市社会经济的可持续发展,城市的水资源管理是重要的一环,而且,这项管理会逐步从防洪、水资源利用的量的管理向水质管理、空间管理和生态体系的保护等综合管理发展,其中恢复河流清澈、优美的自然生态,科学有效地建设城市水环境是个需要研究的大课题. 相似文献
5.
In this paper, a localized MEI method (L-MEI) is developed and combined with the domain decomposition method (DDM) for the simulation of scattering by a concave cylinder. In the L-MEI, the whole domain is decomposed into many subdomains. Different from the conventional MEI method, the MEI coefficients of the L-MEI method in each subdomain are only dependent on the localized metrons that are defined in the subdomain. The localization of metrons has the following advantages: (1) speeding up the calculation of MEI coefficients and saving memory, (2) making the MEI method available for concave structures, and (3) obtaining a band sparse matrix directly without any modification 相似文献
6.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
7.
The ennoblement of corrosion potential (Ecorr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of Ecorr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density. 相似文献
8.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3. 相似文献
9.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
10.