全文获取类型
收费全文 | 2355篇 |
免费 | 184篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 40篇 |
综合类 | 7篇 |
化学工业 | 658篇 |
金属工艺 | 40篇 |
机械仪表 | 57篇 |
建筑科学 | 89篇 |
矿业工程 | 4篇 |
能源动力 | 179篇 |
轻工业 | 325篇 |
水利工程 | 41篇 |
石油天然气 | 11篇 |
无线电 | 292篇 |
一般工业技术 | 416篇 |
冶金工业 | 54篇 |
原子能技术 | 15篇 |
自动化技术 | 323篇 |
出版年
2024年 | 8篇 |
2023年 | 70篇 |
2022年 | 123篇 |
2021年 | 236篇 |
2020年 | 151篇 |
2019年 | 117篇 |
2018年 | 167篇 |
2017年 | 159篇 |
2016年 | 154篇 |
2015年 | 125篇 |
2014年 | 150篇 |
2013年 | 190篇 |
2012年 | 160篇 |
2011年 | 190篇 |
2010年 | 104篇 |
2009年 | 103篇 |
2008年 | 52篇 |
2007年 | 53篇 |
2006年 | 44篇 |
2005年 | 33篇 |
2004年 | 27篇 |
2003年 | 31篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2551条查询结果,搜索用时 31 毫秒
971.
Md. Tariqul Islam Shajib Mahbuba Kawser Md. Nuruddin Miah Parveen Begum Lalita Bhattacharjee A. Hossain Inge S. Fomsgaard Sheikh Nazrul Islam 《Food chemistry》2013
In line of the development of a food composition database for Bangladesh, 10 minor indigenous fruits were analysed for their nutrient composition comprising ascorbic acid, carotenoids and mineral values. Nutrient data obtained have been compared with published data reported in different literatures, book and United States Department of Agriculture-National Nutrient Database for Standard Reference. Ascorbic acid was highest in Wood apple and lowest in Roselle. Monkey jack contained the highest amount of carotenoids, zinc and copper. Content of calcium, magnesium and phosphorous were found highest in Antidesma velutinum. Potassium was the highest in Wood apple followed by in Moneky jack. It was noted that most of the minor fruits have much higher amount of ascorbic acid than the national fruit – Jack fruit ripe, the king fruit – Mango ripe of Bangladesh and exotic fruits – Apple and Grapes. The nutrient values of these minor fruits would make awareness among the people for their mass consumption for healthy life and to grow more minor fruit trees from extinction in order to maintain biodiversity. 相似文献
972.
Mahnaz Kazemipoor Geoffrey A. Cordell Md. Moklesur Rahman Sarker Che wan Jasimah Bt Wan Mohamed Radzi Majid Hajifaraji Phua En Kiat 《International Journal of Food Properties》2013,16(9):1942-1963
Obesity is emerging globally as a leading, underlying contributor to a variety of different diseases, some of which are fatal. This study aims to provide a brief review of the botanical sources which are available to serve as an alternative to modern, synthetic anti-obesity drugs, and to provide a brief discussion of their mechanism of action, and their safe and effective usage. Information was gathered from books, journals, and a variety of electronic sources published in the period of 1991 to 2014. Medicinal plants can reduce weight through five basic mechanisms: controlling appetite, stimulating thermogenesis and lipid metabolism, inhibiting pancreatic lipase activity, preventing adipogenesis, and promoting lipolysis. Based on a review of the available literature, the consumption of recommended medicinal plants in a single form, and at an optimum dosage, could be a safe and effective complementary treatment for obesity. 相似文献
973.
Selamat Jinap Asep Edi Kusnadi Md. Jahurul Haque Akanda Russly Abd Rahman Sahena Ferdosh Md. Zaidul Islam Sarker 《Food and Bioprocess Technology》2013,6(9):2455-2465
The effects of moisture content and alkali treatment on cocoa butter extraction using supercritical fluid were studied. Ground cocoa nibs were examined at moisture contents of 1.95 %, 3.91 %, 5.87 %, 9.79 % and 17.64 % and the pH of the cocoa liquor was maintained at 5.0–5.9, 6.8–7.2 and 7.5–7.9. Cocoa butter was successfully extracted, using supercritical carbon dioxide (SC-CO2) for the moisture content study and SC-CO2 with 25 % ethanol as a cosolvent for the pH-level alkali treatment study, at 35 MPa, 60 °C and 2 ml/min. The results showed that increases in moisture content and pH level significantly (p?<?0.05) increase the yield efficiency. A moisture content of 9.79 % and pH-alkali treatment at 7.5–7.9 produced the highest yield (60.36 % and 73.70 % at 20 and 18 h extraction time, respectively). Triglycerides (TG) and fatty acids (FAs) were similar to those found in cocoa butter obtained using the Soxhlet method. Saturated and short-chain TG and FA constituents were more soluble than unsaturated and long-chain constituents. 相似文献
974.
975.
Electrochemical carbon-nanotube filter performance toward virus removal and inactivation in the presence of natural organic matter 总被引:1,自引:0,他引:1
The performance of an electrochemical multiwalled carbon nanotube (EC-MWNT) filter toward virus removal and inactivation in the presence of natural organic matter was systematically evaluated over a wide range of solution chemistries. Viral removal and inactivation were markedly enhanced by applying DC voltage in the presence of alginate and Suwannee River natural organic matter (SRNOM). Application of 2 or 3 V resulted in complete (5.8 to 7.4 log) removal and significant inactivation of MS2 viral particles in the presence of 5 mg L(-1) of SRNOM or 1 mg L(-1) of alginate. The EC-MWNT filter consistently maintained high performance over a wide range of solution pH and ionic strengths. The underlying mechanisms of enhanced viral removal and inactivation were further elucidated through EC-MWNT filtration experiments using carboxyl latex nanoparticles. We conclude that enhanced virus removal is attributed to the increased viral particle transport due to the applied external electric field and the attractive electrostatic interactions between the viral particles and the anodic MWNTs. The adsorbed viral particles on the MWNT surface are then inactivated through direct surface oxidation. Minimal fouling of the EC-MWNT filter was observed, even after 4-h filter runs with solutions containing 10 mg L(-1) of natural organic matter and 1 mM CaCl(2). Our results suggest that the EC-MWNT filter has a potential for use as a high performance point-of-use device for the removal of viruses from natural and contaminated waters with minimal power requirements. 相似文献
976.
Umama Khan Sabrina Chowdhury Md Morsaline Billah Kazi Mohammed Didarul Islam Henrik Thorlacius Milladur Rahman 《International journal of molecular sciences》2021,22(14)
Neutrophils form sticky web-like structures known as neutrophil extracellular traps (NETs) as part of innate immune response. NETs are decondensed extracellular chromatin filaments comprising nuclear and cytoplasmic proteins. NETs have been implicated in many gastrointestinal diseases including colorectal cancer (CRC). However, the regulatory mechanisms of NET formation and potential pharmacological inhibitors in the context of CRC have not been thoroughly discussed. In this review, we intend to highlight roles of NETs in CRC progression and metastasis as well as the potential of targeting NETs during colon cancer therapy. 相似文献
977.
Hamidreza Sadreazami Marzieh Amini 《AEUE-International Journal of Electronics and Communications》2012,66(5):364-371
A new robust method of spread spectrum based image watermarking is proposed in this article. Spread spectrum technique and scrambling are used for increasing robustness and invisibility of the algorithm. Our suggested method is carried out using ridgelet transform as an efficient transform for representing images with line singularities. In embedding part, the host image is partitioned into non-overlapping blocks and ridgelet transform is applied to each single block. In this way, a curved edge is divided into some straight edges so that ridgelet transform shows optimal performance even for complicated images with curve edges. To embed the watermark bits, the best directions of ridgelet coefficients are selected with respect to their variance intensity. In extraction part, a computationally efficient detection method is used for detecting watermark logo blindly from distorted watermarked image. To achieve more robust algorithm firstly, we find the best place to insert the watermark bits and secondly, we encode the scrambled watermark bits by pseudo random sequences with an authentication key. Robustness of our proposed method is tested against different kinds of attacks. According to the experimental results, proposed method shows much improved performance in comparison to other published works. 相似文献
978.
Robert Chebli Md. Hasanuzzaman Ali Haidar Mohamad Sawan 《Microelectronics Journal》2012,43(10):670-679
A low-power and small silicon area digitally controlled Switched Mode Power Supply (SMPS) is intended for the minimization of both power and size of an on-chip DC power supply building block which is mainly dedicated for implantable medical sensing and microstimulation devices. Such SMPS is based on a successive divider-line analog-to-digital Converter (SDLADC), which is the focus of this paper. Special attention is paid for reducing the power consumption and silicon area of this SDLADC, which consists of a resistor network based on diode connected transistor used to replace the delay-line of the windowed ADC. To compensate process and temperature variations, a digital calibration technique is used to meet the specified static and dynamic output voltage regulations and avoid variations of the regulated SMPS output voltage. The proposed ADC is implemented in AMS 0.35 μm CMOS process. Simulation results show a current consumption of 1.5 μA/MHz and conversion time of 10 ns much lower than recent conventional topology values. The proposed circuit exhibits a quantization steps smaller than 1.6% of Vref and it can be a solution for high switching frequency, which results on faster regulation of SMPS output voltage. 相似文献
979.
The Lorentz model and modified Debye model (MDM) parameters forSi0.6Ge0.4 are presented. A nonlinear optimiza- tion algorithm is developed. The obtained parameters are used to determine the complex relative permittivity of Si0.6Ge0.4, and compared with the experimental data for validation. Finally the obtained parameters are used to analyze the properties of symmetric surface plasmon polariton (SPP) mode propagation in a dielectric-metal-dielectric (DMD) material constructed with silver (Ag) and Si0.6Ge0.4 for further verifying the extracted parameters. 相似文献
980.
Concentration of V, Mn, Fe, Co, Cu, Zn, As, Se, Cd, and Pb in muscle, liver, and gill tissues of red tilapia (Oreochromis spp) sampled from three different aquaculture sites which include earthen pond, ex-tin mining pool, and concrete tank in
Jelebu, Negeri Sembilan, were determined using microwave-assisted digestion–inductively coupled plasma-mass spectrometry.
Accumulation patterns relating organs and elements, as well as origins and elements, were evaluated using multivariate statistics.
With the aid of principal component analysis, it is possible to visualize the distribution pattern of metals in different
organs as well as clustering tendencies of tilapia samples according to the production sites. In general, levels of V, Co,
Fe, Cu, Zn, Se, and Cd in liver were higher than those in muscles and gills, whereas Mn and Pb were higher in gills while
As in muscles. Results from principal component analysis revealed that there are similar pattern of metal distribution among
organs regardless of the production sites. It is also suggested that Cu, As, and Pb are the best describers in characterizing
the studied organs, where liver tissues are associated with high Cu, gills with high Pb, and muscles with high As. On the
other hand, V, Co, and Pb are observed to be key discriminants for sample origins. 相似文献