全文获取类型
收费全文 | 950篇 |
免费 | 98篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 5篇 |
化学工业 | 367篇 |
金属工艺 | 21篇 |
机械仪表 | 21篇 |
建筑科学 | 17篇 |
矿业工程 | 1篇 |
能源动力 | 54篇 |
轻工业 | 124篇 |
水利工程 | 18篇 |
石油天然气 | 9篇 |
无线电 | 71篇 |
一般工业技术 | 180篇 |
冶金工业 | 12篇 |
原子能技术 | 32篇 |
自动化技术 | 112篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 58篇 |
2021年 | 81篇 |
2020年 | 68篇 |
2019年 | 77篇 |
2018年 | 107篇 |
2017年 | 83篇 |
2016年 | 80篇 |
2015年 | 46篇 |
2014年 | 69篇 |
2013年 | 97篇 |
2012年 | 59篇 |
2011年 | 64篇 |
2010年 | 48篇 |
2009年 | 25篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1979年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1052条查询结果,搜索用时 890 毫秒
51.
Behnam Noorani Fatemeh Yazdian Zahra-Soheila Soheili Mehdi Shakibaie Shiva Rahmani 《国际聚合物材料杂志》2018,67(12):754-763
Damage of the retinal pigmented epithelial cells causes various diseases such as age-related macular degeneration in retinal tissue. Nowadays, scientists are attempting to replace lost retinal cells with healthy and efficient cells that provide better conditions for recovering and preventing blindness. In this study, gelatin/chitosan nanofibrous scaffolds with mean diameters of 180?nm were fabricated for subretinal space through electrospinning. Thickness and morphology of the gelatin–chitosan scaffolds were analyzed by scanning electron microscopy (SEM). The results showed that the high rate of degradation, i.e., 90% damage was obtained after 1 month. The cell viability of gelatin/chitosan nanofibers were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The SEM results of cultured RPE on gelatin/chitosan scaffolds showed the appropriate adhesion of cells on the substrate. The results of the identity of RPE cells cultured on the scaffolds indicated that a large number of cells strongly expressed RPE65 and cytokeratin 8/18. 相似文献
52.
53.
A novel bilayer nanofibrous wound dressing, with enhanced mechanical properties is successfully fabricated. This membrane, consisted of polyvinylidenefluoride (PVDF) nanofibers for providing tensile strength and polyhydroxybutyrate/chitosan (PHB/CTS) nanofibers loaded with gentamicin with ability of controlled drug delivery, is a great choice for post-surgical ulcers. Mechanical properties showed dramatically improvement of tensile strength by addition of PVDF layer. Gentamycin release represented both an immediate and a sustained release of about 24?h and 1 week, respectively and release increment with increase of CTS ratio. Results also revealed that drug release in structures follow first order kinetic and Fickian release mechanism. 相似文献
54.
Alireza Hassanzadeh Fatemeh Kanaani Shában Elahi 《Expert systems with applications》2012,39(12):10959-10966
In the era of internet, universities and higher education institutions are increasingly tend to provide e-learning. For suitable planning and more enjoying the benefits of this educational approach, a model for measuring success of e-learning systems is essential. So in this paper, we try to survey and present a model for measuring success of e-learning systems in universities. For this purpose, at first, according to literature review, a conceptual model was designed. Then, based on opinions of 33 experts, and assessing their suggestions, research indicators were finalized. After that, to examine the relationships between components and finalize the proposed model, a case study was done in 5 universities: Amir Kabir University, Tehran University, Shahid Beheshti University, Iran University of Science & Technology and Khaje Nasir Toosi University of Technology. Finally, by analyzing questionnaires completed by 369 instructors, students and alumni, which were e-learning systems user, the final model (MELSS Model1). 相似文献
55.
Masumeh Sadat Shahidi Rizi Abbas Akhavan Sepahi Keivan Beheshti Maal Farzaneh Hosseini 《Petroleum Science and Technology》2017,35(9):831-838
Oil sludge is obtained from the contaminated site of Bahregan area in the Persian Gulf in Iran. Chemotaxis was used for the isolation of alkane-degrading bacteria from oil sludge and the alk genes were determined with specific primers. bac1 identified in Thalassospira was selected as a powerful strain for biodegradation of oil sludge. Biodegradation of oil sludge by bac1 in the presence of nanoparticles was investigated by GC-MS analysis. Synergistic effect of Fe2O3 and Fe3O4 nanoparticles on bacteria increases the biodegradation of oil sludge and produces cyclosiloxane compound which is used in the field of medicine; however, the Thalassospira reduced its toxicity in the environment. 相似文献
56.
Mohammad Mahdavi Fatemeh Khodadadi Azadboni Reza Khodadadi Azadboni 《Journal of Fusion Energy》2012,31(4):368-373
In this paper, the effective Parameters in the confinement and trapping of fast electrons in plasma source Such as; plasma pressure, wall material of plasma chamber and magnetic mirror rate have been investigated with using Comsol & Geant4 code. The calculations are shown that the Multicusp magnetic field was effective the pressure less than 5?mTor, and the confinement effect becomes stronger with decreasing pressure. It is equivalent to a higher yield of output ions of plasma source. The number of fast electrons trapped in the magnetic field increases with increasing magnetic field intensity and using aluminum for wall material. Optimum conditions of confinement plasma, leading to increased the hot electron density, and ionization efficiency is increased. The results of investigations have demonstrated good correspondence with theoretical calculations, therefore there is the adequacy of the developed approach and the possibility to build more effective source ion on this basis. 相似文献
57.
Mohammad Rafat Sadat Jie Huang Sazzad Bin-Shafique Sepehr Rezaeimalek 《Geotextiles and Geomembranes》2018,46(1):77-90
The limit equilibrium (LE) analysis has been used to design MSE walls. Presumably, the deflection of MSE walls can be limited to an acceptable range by ensuring sufficient factors of safety (FOSs) for both external and internal stabilities. However, unexpected ground movements, such as movements induced by excavations, volume changes of expansive soils, collapse of sinkholes, and consolidations of underlying soils, can induce excessive differential settlements that may influence both the stability and the serviceability of MSE walls. In this study, a numerical model, which was calibrated by triaxial tests and further by a specially-designed MSE wall tests, investigated the behavior of an MSE wall as well as the influence of various factors on the performance of the MSE wall when the wall facing settled relatively to the reinforced zone. The numerical results showed that the differential settlement would cause substantial vertical and horizontal movements for the MSE wall, as well as an increase in lateral earth pressure and geosynthetic reinforcement strain. The maximum horizontal movement and increase of the lateral earth pressure occurred at about 1.0 m above the toe. The differential settlement resulted in a critical plane that coincided with the plane of 45°+?/2. The maximum increase of the strain for each geogrid layer occurred in that plane, and the bottom layer had the greatest strain increase among all layers of reinforcement. The study further indicated that the surcharge, backfill friction angle, tensile stiffness of geogrid, reinforcement length and MSE wall height had noticeable influences on horizontal and vertical movements, and strain in geosynthetics. According to the results, the MSE wall that had a higher factor of safety would have less movements and geosynthetic strain increase. In contrast, only the friction angle, tensile stiffness and MSE wall height showed some degree of influence on the lateral earth pressure due to differential settlements. 相似文献
58.
Dan A. Buzatu Willie M. Cooper Christine Summage-West John B. Sutherland Anna J. Williams Deborah A. Bass Lisa L. Smith Robert S. Woodruff Jessica M. Christman Steven Reid Randal K. Tucker Christopher J. Haney Ashfaqe Ahmed Fatemeh Rafii Jon G. Wilkes 《Food microbiology》2013
A flow cytometric method (RAPID-B™) with detection sensitivity of one viable cell of Escherichia coli serotype O157:H7 in fresh spinach (Spinacia oleracea) was developed and evaluated. The major impediment to achieving this performance was mistaking autofluorescing spinach particles for tagged target cells. Following a 5 h non-selective enrichment, artificially inoculated samples were photobleached, using phloxine B as a photosensitizer. Samples were centrifuged at high speed to concentrate target cells, then gradient centrifuged to separate them from matrix debris. In external laboratory experiments, RAPID-B and the reference method both correctly detected E. coli O157:H7 at inoculations of ca. 15 cells. In a follow-up study, after 4 cell inoculations of positives and 6 h enrichment, RAPID-B correctly identified 92% of 25 samples. The RAPID-B method limit of detection (LOD) was one cell in 25 g. It proved superior to the reference method (which incorporated real time-PCR, selective enrichment, and culture plating elements) in accuracy and speed. 相似文献
59.
Various organosilane-treated SiO2 nanoparticles were dispersed in a 2-pack polyurethane coating. The influence of surface modification and silica content on the electrochemical behaviour of the resultant nanocoatings was investigated. Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) variations were examined. The surface chemistry of nanoparticles and its effect on the resultant nanocoating morphology were also studied utilising FTIR, and TEM analyses. The results reveal that the presence of more hydrophobic groups and longer-lengthed hydrophobic chains on the surface of nanoparticles, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance. 相似文献
60.
The paper studied by Subbaraj et al. (2009) considers the feasibility of using self adaptive real-coded genetic algorithm for enhancement of combined heat and power economic dispatch. The paper includes some problems about the considered feasible operating region. In this discussion, the controversial point of the paper are given. 相似文献