全文获取类型
收费全文 | 2815篇 |
免费 | 119篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 84篇 |
综合类 | 13篇 |
化学工业 | 397篇 |
金属工艺 | 51篇 |
机械仪表 | 67篇 |
建筑科学 | 125篇 |
能源动力 | 104篇 |
轻工业 | 216篇 |
水利工程 | 27篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 588篇 |
一般工业技术 | 471篇 |
冶金工业 | 401篇 |
原子能技术 | 25篇 |
自动化技术 | 364篇 |
出版年
2023年 | 14篇 |
2022年 | 55篇 |
2021年 | 43篇 |
2020年 | 25篇 |
2019年 | 34篇 |
2018年 | 49篇 |
2017年 | 54篇 |
2016年 | 53篇 |
2015年 | 61篇 |
2014年 | 109篇 |
2013年 | 177篇 |
2012年 | 148篇 |
2011年 | 172篇 |
2010年 | 120篇 |
2009年 | 119篇 |
2008年 | 143篇 |
2007年 | 114篇 |
2006年 | 126篇 |
2005年 | 87篇 |
2004年 | 83篇 |
2003年 | 68篇 |
2002年 | 79篇 |
2001年 | 62篇 |
2000年 | 63篇 |
1999年 | 70篇 |
1998年 | 169篇 |
1997年 | 118篇 |
1996年 | 70篇 |
1995年 | 60篇 |
1994年 | 56篇 |
1993年 | 64篇 |
1992年 | 36篇 |
1991年 | 22篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1977年 | 6篇 |
1975年 | 13篇 |
1974年 | 7篇 |
1972年 | 6篇 |
1967年 | 5篇 |
1965年 | 6篇 |
排序方式: 共有2942条查询结果,搜索用时 15 毫秒
101.
Benedetto Nastasi Gianluigi Lo Basso 《International Journal of Hydrogen Energy》2017,42(38):23933-23951
Temperature levels play a key role in the thermal energy demand of urban contexts affecting their associated primary energy consumption and Renewable Energy Fraction. A Smart Heating strategy accounts for those supply features requiring new solutions to be effectively renewable and to solve the RES capacity firming. Power-to-Gas (P2G) is the way to decarbonize the energy supply chain as fraction of Hybrid fuels, combination of fossil ones and Renewable Hydrogen, as immediate responsive storage solution. While, Power-To-Heat is conceived as the strategy to modernize the high and medium temperature heating systems by electricity-driven machines to switch from Fuel-to-Heat to Electricity-to-Heat solutions. The authors investigated on different urban energy scenarios at RES share increase from 25% up to 50% in the energy mix to highlight strengths and weaknesses of the P2G applications. Primary Energy Consumption was chosen as the objective function. Three Reference Cities were chosen as reference scenarios. Moreover, the analytical models of P2G was designed and implemented in the reference energy system. The results of the twelve scenarios, four for each Reference City were evaluated in terms of amount of Renewable Heat delivered. Finally, the interaction between P2G and renewable heat production was evaluated. 相似文献
102.
This paper describes the development and performance of a new rapid amperometric biosensor for fructose monitoring in food analysis. The biosensor is based on the activity of fructose dehydrogenase (FDH) immobilised into a carbon nanotube paste electrode according to two different procedures. The direct wiring of the FDH in a highly original osmium-polymer hydrogel was found to offer a better enzyme entrapment compared to the immobilisation of the enzyme in an albumin hydrogel. The optimised biosensor required only 5 U of FDH and kept the 80% of its initial sensitivity after 4 months. During this time, the biosensor showed a detection limit for fructose of 1 μM, a large linear range between 0.1 and 5 mM, a high sensitivity (1.95 μA cm−2 mM), good reproducibility (RSD = 2.1%) and a fast response time (4 s). 相似文献
103.
104.
Consultants, in competing for work through two-envelope fee tendering, have been urged to consider variability differences between fees and technical scores, since the criterion with the greatest variability will influence which consultant is awarded the contract. Fee and technical score variability arising from different client fee tendering competitions is analysed in this paper, and a method proposed for determining whether a particular client's two-envelope fee tendering competition is likely to be dominated in terms of technical score or fee. Such information should be useful to consultants, as part of their bidding strategy, in deciding whether to aim for a higher technical score or submit a lower fee. Standard deviation is used to measure fee and technical score variability. Fee and technical score standard deviations are determined for each tendering competition, expressed as a ratio and aggregated over a series of competitions. A technical score-fee standard deviation ratio approximately equal to unity indicates that for future competitions consultants should adopt a balanced bidding strategy in putting equal emphasis on fee and technical score. A smaller ratio indicates that consultants should adopt a ‘low fee’ strategy whereas a larger ratio shows that consultants should adopt a ‘high technical score’ strategy. Fee tendering data from two large Hong Kong public sector clients were analysed. Fees were found to dominate the vast majority of tendering competitions, thereby indicating that consultants would be wise to adopt a low fee strategy in future competitions. 相似文献
105.
In the current economic climate, budgets for the maintenance of public buildings are unlikely to meet the ever-increasing maintenance needs. Although it is unlikely that this problem can be overcome completely without an injection of further resources, it is possible for government maintenance authorities to improve the situation by ensuring that the best solution in terms of ‘value for money’ is achieved in the planned maintenance programme. A maintenance plan which is based on a rational assessment of priorities and up-to-date knowledge of the condition of the property stock will help to ensure the best use of available resources. Based on the multi-attribute maintenance prioritization model developed by Alan Spedding, Roy Holmes and Qiping Shen at the University of West of England, which is simple in practice and flexible from a management point of view, this paper presents the results of some further research into this area by modifying the original model using an analytical hierarchy process in deciding the weightings of the criteria set out in the prioritization model. This modified model is more quantitative and objective than the original model. The validation of the framework is also discussed. 相似文献
106.
G. D’Amato Avanzi Y. Galanti R. Giannecchini D. Lo Presti A. Puccinelli 《Bulletin of Engineering Geology and the Environment》2013,72(3-4):609-624
In Northern Tuscany (Italy) rapid, shallow landslides often cause casualties and severe damage. Aimed at contributing to the characterisation of the source areas of rapid, shallow landslides, this paper deals with the geotechnical parameterisation of the mainly involved soil by means of dynamic penetration tests. The source areas are usually located in difficult access sites, where boring and undisturbed sampling are very hard and onerous. Therefore, the results of 177 dynamic penetration tests were analysed, including dynamic probing (DP) tests and standard penetration tests (SPT). The results of these tests were related to relative density D r and friction angle Φ′ of the soil by means of empirical equations. The distribution and variability of these parameters were analysed and related to soil type, test type and probing depth. The D r and Φ′ values coming from the DP and SPT tests were found to be comparable. The Φ′ values coming from DP tests and direct shear tests showed an acceptable correlation, confirming the utility of the DP tests. The DP test can thus be an effective tool in the estimation of the properties of potentially unstable soil slope covers. 相似文献
107.
108.
Lui Ng Sunny Kit-Man Wong Zheng Huang Colin Siu-Chi Lam Ariel Ka-Man Chow Dominic Chi-Chung Foo Oswens Siu-Hung Lo Roberta Wen-Chi Pang Wai-Lun Law 《International journal of molecular sciences》2022,23(3)
CD26 has been reported as a marker for colorectal cancer stem cells endowed with tumor-initiating properties and capable of colorectal cancer (CRC) metastasis. In this study, we investigated the functional effect of CD26 on CRC angiogenesis and metastasis, and the potential underlying mechanism. The functional effects of CD26 overexpression or repression were determined by a wound healing experiment, and cell migration and invasion assays in vitro and in mouse models. Differentially expressed genes regulated by CD26 were identified by genome-wide mRNA expression array and validated by quantitative PCR. CD26 functionally regulated CRC cell migration and invasion in vitro and angiogenesis and metastasis in vivo. Genome-wide mRNA expression array and qPCR showed that MMP1 was up-regulated in CD26+ subpopulation, and a subsequent experiment demonstrated the regulatory effect of CD26 on MMP1 in CRC cell lines with CD26 repression or overexpression. Furthermore, overexpression of CAV1 abrogated the CD26-regulated MMP1 induction in CRC cell lines. This study demonstrated the functional roles of CD26 in inducing CRC migration, invasion, angiogenesis and metastasis and identified the potential involvement of MMP1 and CAV1 in such process. CD26 is an attractive therapeutic target for combating tumor progression to improve the prognosis of CRC patients. 相似文献
109.
Yew Joon Tam Morvarid Akhavan Rezaei Mohd Lila Mohd Azmi Abdul Rani Bahaman Sewn Cen Lo 《分离科学与技术》2016,51(5):816-829
Univariate screening on factors affecting the purification performance of recombinant hepatitis B surface antigen (HBsAg) on ion exchange chromatography (IEC) and size exclusion chromatography (SEC) and the establishment of a two-step purification strategy were performed. Amongst four IEC adsorbents examined, the use of Q Sepharose XL IEC adsorbent under optimized conditions together with optimized SEC purification was able to efficiently purify HBsAg. An established purification strategy comprising the two techniques further demonstrated adaptability for scale-up operations with a final total purification factor (PF) of 94.82 ± 16.20, HBsAg purity of 95.48% and recovery yield of 78.07%. 相似文献
110.
Mohammad Maududul Huq Md. Robiur Rahman Masnun Naher Mohammad Mizanur Rahman Khan Mostafa Kamal Masud Golam Mohammad Golzar Hossain Nianyong Zhu Yih Hsing Lo Muhammad Younus Wai-Yeung Wong 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(6):1243-1252
Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (1H, 13C and 31P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh3, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S1 → S0) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts. 相似文献