全文获取类型
收费全文 | 291篇 |
免费 | 19篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 90篇 |
金属工艺 | 6篇 |
机械仪表 | 11篇 |
建筑科学 | 7篇 |
能源动力 | 16篇 |
轻工业 | 33篇 |
水利工程 | 8篇 |
石油天然气 | 3篇 |
无线电 | 24篇 |
一般工业技术 | 54篇 |
冶金工业 | 6篇 |
自动化技术 | 45篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 11篇 |
2019年 | 24篇 |
2018年 | 26篇 |
2017年 | 29篇 |
2016年 | 24篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 35篇 |
2012年 | 16篇 |
2011年 | 21篇 |
2010年 | 20篇 |
2009年 | 11篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 3篇 |
1992年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有314条查询结果,搜索用时 15 毫秒
11.
The composition of essential oils from aerial parts of Heracleum persicum, a widely used medicinal plant, and three other Heracleum species growing wild in Iran were analysed by GC and GC–MS. Myristicin (53.6%), (E)-anethole (25.0%), hexyl butanoate (29.7%) and elemicin (41.1%) were the major compounds of Heracleum pastinacifolium, H. persicum, Heracleum rechingeri and Heracleum transcaucasicum, respectively. Cytotoxic activity assessed on three human cancer cell lines (HeLa, LS180 and Raji), showed that essential oils from H. transcaucasicum (IC50 values; 0.362–0.594 mg/ml) followed by H. pastinacifolium (0.497–1.398 mg/ml) had moderate antitumoral activities. In the DPPH radical scavenging assay, H. pastinacifolium and H. persicum oils showed the highest activities with IC50 values of 7.3 and 7.4 mg/ml, respectively. Antioxidant activity correlated well with the total phenolic content of the oils. None of the essential oils showed significant antimicrobial activities. 相似文献
12.
Motahhareh Estebsari Mohammad Gholami Mohammad Javad Ghahramanpour 《International Journal of Circuit Theory and Applications》2018,46(3):401-414
In this paper, a design of analog delay locked loop is introduced in which new techniques are applied to eventually increase operating frequency range and reduce jitter considerably. In this design, all blocks of a delay locked loop including a voltage controlled delay line, charge pump, and loop filter are accurately designed. A new delay cell is proposed with wide delay range, in which increase of delay range results in using fewer cells, and consequently the power consumption will decrease. Current mirror techniques and feedback in the proposed charge pump also cause higher current matching and better jitter performance. This delay locked loop, which is designed with TSMC 0.18‐μm CMOS technology, has a wide frequency range from 217 to 800 MHz. It consumes maximum 3.4‐mW and minimum 2.6‐mW power dissipation in source voltage of 1.8 V, which is suitable for low power applications. It also has an appropriate lock time that is at least equal to 3 clock cycles at 217 MHz and at most 25 clock cycles at 800 MHz. Jitter performance in this delay locked loop is improved significantly: RMS jitter is 0.65 ps at 800 MHz and 2.54 ps at 217 MHz. Moreover, its maximum peak‐to‐peak jitter is equal to 5.17 ps, and its minimum peak‐to‐peak jitter is equal to 1.39 ps at 217 and 800 MHz, respectively. 相似文献
13.
Mohsen Gholami Mohammad Reza Talaie Seyed Foad Aghamiri 《Korean Journal of Chemical Engineering》2014,31(2):322-326
A bi-modal porous structure MCM-41 (BPS-MCM-41) was synthesized and functionalized by 3-[2-(2-Aminoethylamino)ethylamino]propyltrimethoxysilane (TRI); also, its performance in amine grafting and CO2 capturing was compared with that of pore-expanded MCM-41 [1]. To create larger pores beside the mesoporous structure of MCM-41, carbon black nanoparticles were used as the solid template. Characterizing the BPS-MCM-41 using the BET and BJH techniques resulted in the surface reduction of 29.3 percent and volume increase of 68.46 percent. The pore size distribution showed two peaks: a narrow peak at 2.24 nm diameter, which belonged to micelles, and a wide one at about 50 nm due to the presence of used nanoparticles. The functionalization confirmed that BPS-MCM-41 is capable of accommodating a large quantity of amine groups. The CO2 adsorption measurement indicated that internal volume of the adsorbent was a critical factor affecting the adsorption capacity of the amine grafted adsorbents. 相似文献
14.
Ahmadi Ameneh Sedaghat Tahereh Azadi Roya 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(10):4126-4140
Journal of Inorganic and Organometallic Polymers and Materials - 3-Chloropropyltrimethoxysilane (CPTMS) was grafted on the surface of silica coated Fe3O4 core (Fe3O4@MCM-41) and then condensed with... 相似文献
15.
We developed an alternative approach for measuring information and communication technology (ICT), applying Data Envelopment Analysis (DEA) using data from the International Telecommunications Union as a sample of 183 economies. We compared the ICT-Opportunity Index (ICT-OI) with our DEA-Opportunity Index (DEA-OI) and found a high correlation between the two. Our findings suggest that both indices are consistent in their measurement of digital opportunity, though differences still exist in different regions. Our new DEA-OI offers much more than the ICT-OI. Using our model, the target and peer groups for each country can be identified. 相似文献
16.
Afshin Maleki Amir Hossein Mahvi Roya Ebrahimi Yahya Zandsalimi 《Korean Journal of Chemical Engineering》2010,27(6):1805-1810
The degradation of two commercially available dyestuffs (C.I. Reactive Black 5 and C.I. Disperse Orange 25) by ultraviolet
radiation (UV), ultrasonic irradiation (US), UV/H2O2 and US/H2O2 processes was investigated in a laboratory-scale batch photoreactor equipped with a 55 W immersed-type low-pressure mercury
vapor lamp and a sonoreactor with low frequency (42 kHz) plate type transducer at 170 W of acoustic power. The toxicity was
also evaluated in acute toxicity studies using Daphnia magna. Results showed that color removal efficiencies by US and US/H2O2 processes were negligible for both dyes. Almost complete disappearance of Reactive Black 5 (97.9%) in UV/H2O2 process was possible after 5 min of irradiation. The maximum color removal efficiency of Disperse Orange 25 after 10 min
of irradiation, however, was only 9.2% and reached a maximum value of 41% after 120 min of irradiation. Pseudo-first order
kinetics with respect to dyestuffs concentrations was found to fit all the experimental data. The results clearly showed that
both dyes examined were toxic to D. magna and resulted in quite low LC50 values. 相似文献
17.
Mohammad Hadi Gholami Mahmood Reza Azizi 《The International Journal of Advanced Manufacturing Technology》2014,73(5-8):981-988
Selection of parameters in machining process significantly affects quality, productivity, and cost of a component. This paper presents an optimization procedure to determine the optimal values of wheel speed, workpiece speed, and depth of cut in a grinding process considering certain grinding conditions. Experimental studies have been carried out to obtain optimum conditions. Mathematical models have also been developed for estimating the surface roughness based on experimental investigations. A non-dominated sorting genetic algorithm (NSGA II) is then used to solve this multi-objective optimization problem. The objectives under investigation in this study are surface finish, total grinding time, and production cost subjected to the constraints of production rate and wheel wear parameters. The Pareto-optimal fronts provide a wide range of trade-off operating conditions which an appropriate operating point can be selected by a decision maker. The results show the proposed algorithm demonstrates applicability of machining optimization considering conflicting objectives. 相似文献
18.
Shabnam Asghari Niari Reza Rahbarghazi Roya Salehi Leila Kazemi Sonia Fathi Karkan Mohammad Karimipour 《Microscopy research and technique》2022,85(4):1433-1443
In recent years with regard to the development of nanotechnology and neural stem cell discovery, the combinatorial therapeutic strategies of neural progenitor cells and appropriate biomaterials have raised the hope for brain regeneration following neurological disorders. This study aimed to explore the proliferation and neurogenic effect of PLGA and PLGA–PEG nanofibers on human SH-SY5Y cells in in vitro condition. Nanofibers of PLGA and PLGA–PEG biomaterials were synthesized and fabricated using electrospinning method. Physicochemical features were examined using HNMR, FT-IR, and water contact angle assays. Ultrastructural morphology, the orientation of nanofibers, cell distribution and attachment were visualized by SEM imaging. Cell survival and proliferation rate were measured. Differentiation capacity was monitored by immunofluorescence staining of Map-2. HNMR, FT-IR assays confirmed the integration of PEG to PLGA backbone. Water contact angel assay showed increasing surface hydrophilicity in PLGA–PEG biomaterial compared to the PLGA substrate. SEM analysis revealed the reduction of PLGA–PEG nanofibers' diameter compared to the PLGA group. Cell attachment was observed in both groups while PLGA–PEG had a superior effect in the promotion of survival rate compared to other groups (p < .05). Compared to the PLGA group, PLGA–PEG increased the number of Ki67+ cells (p < .01). PLGA–PEG biomaterial induced neural maturation by increasing protein Map-2 compared to the PLGA scaffold in a three-dimensional culture system. According to our data, structural modification of PLGA with PEG could enhance orientated differentiation and the dynamic growth of neural cells. 相似文献
19.
This paper develops an economic order quantity model for non-instantaneous deteriorating items with and without shortages to investigate the performance of the vendor-managed inventory (VMI) system. This model is developed for a two-level supply chain consisting of a single supplier and single retailer with a single non-instantaneous deteriorating item. A numerical example and sensitivity analysis are provided to illustrate how increasing or reducing the related parameters change the optimal values of the decision variables of the two proposed models. The results show that VMI works better and charges lower cost in all conditions. 相似文献
20.