全文获取类型
收费全文 | 3360篇 |
免费 | 178篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 64篇 |
综合类 | 7篇 |
化学工业 | 752篇 |
金属工艺 | 79篇 |
机械仪表 | 80篇 |
建筑科学 | 115篇 |
矿业工程 | 3篇 |
能源动力 | 210篇 |
轻工业 | 300篇 |
水利工程 | 38篇 |
石油天然气 | 80篇 |
无线电 | 426篇 |
一般工业技术 | 637篇 |
冶金工业 | 115篇 |
原子能技术 | 13篇 |
自动化技术 | 635篇 |
出版年
2024年 | 14篇 |
2023年 | 120篇 |
2022年 | 234篇 |
2021年 | 274篇 |
2020年 | 183篇 |
2019年 | 179篇 |
2018年 | 223篇 |
2017年 | 168篇 |
2016年 | 175篇 |
2015年 | 110篇 |
2014年 | 138篇 |
2013年 | 269篇 |
2012年 | 177篇 |
2011年 | 194篇 |
2010年 | 136篇 |
2009年 | 137篇 |
2008年 | 102篇 |
2007年 | 69篇 |
2006年 | 77篇 |
2005年 | 70篇 |
2004年 | 51篇 |
2003年 | 37篇 |
2002年 | 37篇 |
2001年 | 31篇 |
2000年 | 25篇 |
1999年 | 30篇 |
1998年 | 35篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 14篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 5篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1974年 | 4篇 |
排序方式: 共有3554条查询结果,搜索用时 0 毫秒
81.
Mohammed Djebbouri Mohamed Terras 《The International journal of environmental studies》2013,70(6):990-1003
An evaluation and inventory study on the natural vegetation cover and its diversity was carried out on the forest vegetation of the district of Saïda. The floristic diversity of our study area revealed the existence of 397 taxa belonging to 64 families and 271 genera. The most important families are Asteraceae (42 genera), Fabaceae (25 genera), Brassicaceae (22 genera) and Poaceae (22 genera). The category of rare taxa represents 13% of the studied flora (52 taxa). In our study area, we have counted 35 endemic regional species of which 19 species are endemic Algerian-Moroccan, and 3 species are strictly endemic to Algeria. Among the taxa analysed, 02 are included in the IUCN Red List, and 12 are on the Algerian list of protected non-cultivated plant species. 相似文献
82.
Mohammed Wanous Halim A. Boussabaine John Lewis 《Construction Management & Economics》2013,31(7):737-744
Despite the crucial importance of the ‘bid/no bid’ decision in the construction industry, it has been given little attention by researchers. This paper describes the development and testing of a novel bid/no bid model using the artificial neural network (ANN) technique. A back‐propagation network consisting of an input buffer with 18 input nodes, two hidden layers and one output node was developed. This model is based on the findings of a formal questionnaire through which key factors that affect the ‘bid/no bid’ decision were identified and ranked according to their importance to contractors operating in Syria. Data on 157 real‐life bidding situations in Syria were used in training. The model was tested on another 20 new projects. The model wrongly predicted the actual bid/no bid decision only in two projects (10%) of the test sample. This demonstrates a high accuracy of the proposed model and the viability of neural network as a powerful tool for modelling the bid/no bid decision‐making process. The model offers a simple and easy‐to‐use tool to help contractors consider the most influential bidding variables and to improve the consistency of the bid/no bid decision‐making process. Although the model is based on data from the Syrian construction industry, the methodology would suggest a much broader geographical applicability of the ANN technique on bid/no bid decisions. 相似文献
83.
Mohammed A. Rajeh John E. Tookey James Olabode Bamidele Rotimi 《Construction Management & Economics》2013,31(11-12):921-941
The choice of an appropriate procurement system is crucial to construction project success. Procurement selection is largely based on path determination charts, with at least eight key criteria needing to be weighted by decision-makers. Including certain criteria whilst ignoring client-borne transaction costs (TCs) resulting from environmental uncertainties simplifies this process. TCs are ‘unseen’ costs associated with pre- and post-contract work. The effects of uncertainties in the transaction environment and procurement systems on TCs are investigated, comparing the traditional and design-build procurement systems. A cross-sectional sample approach was deployed, involving survey questionnaire and results verification through ‘real-world’ cases. Data was sought from construction professionals in management, design and operation of construction projects. The research participants evaluate their time spent on procurement activities using a five-point Likert scale. Hypotheses of the relations between environmental uncertainties, procurement systems, and pre- and post-contract TCs are tested using a structural equation modelling (SEM) approach. The study found that TCs account for about 46.75% and 42.88% of the daily time spent by project managers in traditional and design-build procurement systems in New Zealand respectively. The study concludes that the TC concept is a useful framework for determining objective instead of subjective opinions for procurement decisions. 相似文献
84.
Hybrid organosiloxane coatings containing epoxide precursors for protecting mild steel against corrosion in a saline medium 下载免费PDF全文
Hybrid organic–inorganic materials made from sol–gel precursors can be used as anticorrosion barriers on metal substrates. The modification of epoxy resins with silicones is an interesting approach toward the synthesis of hybrid materials that combine the advantages offered by epoxy resins with those of silicones. In this study, novel hybrid epoxy‐silicon materials were synthesized using sol–gel chemistry and subsequently functionalized with 4,4′‐methylenebis(phenyl isocyanate), incorporating urethane functionality into the final polymer. The study screened five different epoxide precursors for use in the synthesis of the new hybrid materials and optimizing their anticorrosion properties. Spectral characterization confirms the proposed chemical structures of the newly synthesized polymers. The newly developed polymers were painted on mild steel panels, thermally cured, and their thermal, surface morphological, adhesion, and anticorrosion properties were fully characterized. The new coatings were found to have excellent thermal stability and adherence properties to steel surface. The results of corrosion testing on coated steel panels following long‐term immersion in a 3.5 wt % aqueous NaCl medium revealed that the polymer prepared using the epoxide precursor bisphenol A diglycidyl ether provided the best anticorrosion protection property among the synthesized polymers. This could be attributed to the excellent integrity and crosslink density properties in addition to the lack of microdefects in the surface of this coated sample as confirmed by scanning electron microscopy analyses. The newly prepared hybrid coatings reported in this study are very promising as an alternative to toxic chromate‐based coatings. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43947. 相似文献
85.
Barkai Hassan El Abed Soumya Sadiki Moulay Iraqui Houssaini Mohammed 《The Journal of Adhesion》2016,92(5):341-348
The sessile drop technique was used to investigate the evolution of the physicochemical properties of cedar wood as a function of contact time with the Penicillium expansum spores. The most important finding showed that the impact of different contact periods (2, 4, 6, 8, 10, and 24 hr) on the wood surface were very indicative. In fact, after 2 hr of contact, the results have shown a significant impact of the bioadhesion of spores to the substrate on both the hydrophobic character (θW = 108.5°; ΔGiwi = ?28.25 mJ/m2), the electron donor (γ? = 13.63 mJ/m2), and the electron acceptor (γ+ = 4.35 mJ/m2) parameters that were significantly reduced compared to the initial wood (θW = 118.5°; ΔGiwi = ?6.29 mJ/m2; γ? = 32.1 mJ/m2; and γ+ = 9.1 mJ/m2). In addition, this decrease of parameters continued over time to stabilize after 10 hr of contact. Indeed, after 24 hr, the acid/base properties were almost zero and the contact angle with water decreased to 30°. Moreover, it was found that the coefficient of correlation (r2) was strong between the contact angle with water, the surface energy, and the electron acceptor character with the contact time parameter with values (r2 = 0.65), (r2 = 0.79), and (r2 = 0.68), respectively. 相似文献
86.
87.
88.
Mohammed Shahien Motohiro Yamada Masahiro Fukumoto 《Journal of Thermal Spray Technology》2016,25(5):851-873
Reactive plasma spraying (RPS) is a promising technology for the in situ formation of several ceramic coatings. The focus of this paper is to summarize the state of our current knowledge about the RPS process and using the nitriding of Al particles and the fabrication of aluminum nitride coatings, as a case study. The aspects and challenges in this process such as the influence of the plasma power, in-flight time, particle size, nitriding mechanism, splat morphology, in-flight particle diagnostics, N2 plasma gas, and the feeding rate on the RPS process are analyzed and discussed. 相似文献
89.
Mustafa S. Nasser Mohammed J. Al-Marri Abdelbaki Benamor Sagheer A. Onaizi Majeda Khraisheh Mohammed A. Saad 《Korean Journal of Chemical Engineering》2016,33(2):448-455
The effects of the surface charge type and density C496, C492 and A130LMW polyacrylamides (PAMs) on the rheological behavior of real industrial papermaking suspensions were quantitatively related to the degree of flocculation for the same industrial papermaking suspensions. The floc sizes were larger but less dense when anionic PAM was used, and this due to the repulsive forces between the anionic PAM and colloidal particles, leading to the development of open structure flocs of less density. On the other hand, rheological measurements showed that the papermaking suspension is thixotropic with a measurable yield stress. The results showed that the magnitude of the critical stress, τ c , complex viscosity, η*, elastic modulus, G′, and viscous modulus, G″, depend on the number of interactions between the PAM chains and particle surface and the strength of those interactions. Cationic PAM showed higher values of η*, G′, G″ and τ c compared to anionic PAM. This behavior is in good agreement with Bingham yield stress, τ B , adsorption and effective floc density results. Similar to oscillatory measurements, creep measurements also showed that the deformation was much lower for the cationic PAM based suspensions than for the anionic PAM based suspensions. Furthermore, the results revealed that increasing the cationic PAM surface charge decreases the floc size but increases the adsorption rate, elasticity and effective floc density proposing differences in the floc structures, which are not revealed clearly in the Bingham yield stress measurements. 相似文献
90.
El Guerraf Abdelqader Ben Jadi Sana Aouzal Zaynab Bouabdallaoui Mimouna Bakirhan Nurgul K. Ozkan Sibel A. Bazzaoui Mohammed Bazzaoui El Arbi 《Journal of Applied Electrochemistry》2022,52(9):1383-1407
Journal of Applied Electrochemistry - Modern technologies continuously need special materials with specific properties to adopt the desired application. Recently, numerous researches have been... 相似文献