首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   213篇
  免费   8篇
电工技术   2篇
化学工业   16篇
金属工艺   5篇
机械仪表   1篇
建筑科学   4篇
能源动力   19篇
轻工业   63篇
无线电   16篇
一般工业技术   39篇
冶金工业   18篇
原子能技术   1篇
自动化技术   37篇
  2023年   1篇
  2022年   5篇
  2021年   7篇
  2020年   10篇
  2019年   16篇
  2018年   6篇
  2017年   3篇
  2016年   6篇
  2015年   4篇
  2014年   11篇
  2013年   12篇
  2012年   9篇
  2011年   9篇
  2010年   7篇
  2009年   8篇
  2008年   9篇
  2007年   10篇
  2006年   6篇
  2005年   5篇
  2004年   8篇
  2003年   4篇
  2001年   5篇
  2000年   6篇
  1999年   1篇
  1998年   7篇
  1997年   8篇
  1996年   4篇
  1995年   2篇
  1994年   5篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   4篇
  1985年   7篇
  1984年   3篇
  1982年   1篇
  1981年   1篇
  1977年   1篇
排序方式: 共有221条查询结果,搜索用时 812 毫秒
101.
This experiment is the first exploration of use of charge traps in the bulk of deposited top oxide and at the interface between thermal oxide and deposited top oxide. We report the operational characteristics of SiO2/SiO2 device structures with 0.5 microm gate width and length. Low power operations are achieved through very thin gate stacks of 3 nm of thermally grown oxide and 7 nm of deposited oxide. However, narrow memory windows have been acquired comparing with conventional silicon-oxide-nitride-oxide-silicon (SONOS) memory cells due to a low trap density at the interface between a grown oxide and a deposited oxide. Additionally, the electric field between the channel and the charge is determined by solving 1D Poisson equation at a given write voltage, then total tunneling current density is calculated to make a program modeling for charge trapping devices. Tunneling/trapping simulation based on Fowler-Nordheim (F-N) tunneling performed and it fits the programming curves well. The memory window is almost constant after 100,000 cycles, and the retention characteristics are deteriorated rapidly.  相似文献   
102.
The effect of aqueous extracts of green alga-Haematococcus pluvialis and blue green alga-Spirulina platensis was studied for accumulation of betalaines (food colourant) and thiophenes (insecticide useful against food grain spoilage) in hairy root cultures of Beta vulgaris and Tagetes patula, respectively. It was found that upon treatment with extracts (100 μg dry cell extract/ml of the culture medium each) of H. pluvialis and S. platensis there was an increase in biomass of cultured Beta vulgaris hairy roots which was 165.3 g fresh wt/L (14.38 g dry wt/L) and 149.4 g fresh wt/L (13 g dry wt/L), respectively from the initial inoculum of 1.25 g fresh wt/L (0.115 g dry wt/L). The accumulation of betalaines showed an increase of 2.28 fold on 15th day in hairy root culture treated with H. pluvialis over the control (7.9 mg/g dry wt) on the same day from the initial level of 0.67 mg/g dry wt. Similarly S. platensis extract treated hairy roots showed elicitation of betalaines 1.16 fold on 25th day over the control (11.08 mg/g dry wt) from the initial level of 0.67 mg/g dry wt. It was also observed that the H. pluvialis extract also influenced the biomass production in T. patula hairy roots which was 1.4 fold higher than the control (40 g fresh wt/L or 3.21 g dry wt/L) on 20th day from the initial inoculum of 1.25 g fresh wt/L (0.105 g dry wt/L). Whereas the accumulation of thiophene increased by 1.2 fold in cultures treated with H. pluvialis extract on the 20th day over the untreated control (510 μg/g dry wt) from the initial level of 200 μg/g dry wt, while S. platensis extract did not influence the growth as well as thiophene accumulation. In conclusion S. platensis extract influenced elicitation of betalaines in B. vulgaris hairy roots where as H. pluvialis extract elicited betalaine and thiophene production in hairy root cultures of B. vulgaris and T. patula respectively.  相似文献   
103.
Shoots, plantlets and semi‐differentiated callus (SDC) cultures of Pandanus amaryllifolius capable of producing high levels of basmati rice flavour were established in vitro using Murashige and Skoog nutrient medium. A total of 10% of the initial explants responded to produce shoot cultures in the presence of benzylamino purine (BAP) (0.5 mg L?1) and glutamine (100 mg L?1). Leaf explants and basal portions of shoots produced SDC whereas elongated in vitro shoots could be continuously multiplied, using BAP (1.5 mg L?1) and kinetin (Kn) (1.0 mg L?1), and rooted in half‐strength medium for ex vitro cultivation leading to a process of micropropagation. Steam‐distillation extraction (SDE) followed by gas chromatography‐mass spectrometry (GC‐MS) analysis of various cultured organs and spent liquid medium used for SDC revealed the presence of 2‐acetyl‐1‐pyrroline (2‐AP) to various extents. This 2‐AP compound has been identified as the major flavouring compound of scented basmati and other scented rice varieties. 2‐AP was found to be highest, on a fresh weight basis, in SDC (19.7 mg kg?1) on the 40th day, whereas in vitro roots, shoots and field leaves (of one‐year‐old plant) had lower levels of 15, 6.8 and 14 mg kg?1, respectively. Further enhancement of 2‐AP in SDC using precursor was possible by feeding into medium 1 mmol L?1 of L ‐proline where a highest level of 21.67 ppm of 2‐AP accumulated on the seventh day whereas a higher level of 2 mmol L?1 of L ‐proline suppressed 2‐AP levels. The present report is the first on the tissue culture studies of P. amaryllifolius where continuous production of plantlets as well as synthesis of high levels of 2‐AP has been documented. Copyright © 2005 Society of Chemical Industry  相似文献   
104.
Studies were conducted to determine the possible production of coumarins in hairy root cultures of Cichorium intybus L.cv.Lucknow local under the influence of microbial agents. Pythium aphanidermatum and Phytopthora parasitica var. nicotiana were cultured and their mycelial and medium filtrate were used for the elicitation of coumarin production. The media filtrate of P. parasitica at 1.0% v/v added to the MS basal medium led to the maximum growth of hairy roots of C. intybus, which was 1.57-fold higher than the untreated control on the 28th day of culture, along with maximum esculin and esculetin yields which were 4.06- and 3.71-fold higher than the control on the 28th day. The yields of esculin and esculetin in hairy root cultures of chicory strongly correlated with growth. To check the effect of these fungal elicitors on endogenous polyamine metabolism, titers of total endogenous polyamines were analyzed. It was confirmed that the media filtrate of P. parasitica at 1.0% v/v concentration resulted in maximum accumulation of total endogenous polyamines, wherein endogenous spermine titers were found to be maximum as compared to endogenous spermidine and putrescine titers on the 28th day. Total endogenous spermine in the case of 1.0% MF v/v P. parasitica was 1.3-fold higher than that of the control on the 28th day of culture. Maximum growth index with greater length of primary root (17.61±0.18 cm) and greater number of secondary and tertiary roots was recorded for the medium filtrate of P. parasitica at 1.0% v/v concentration. This study also provided an insight into the morphological changes in terms of branching patterns, occurring in roots under the influence of these fungal elicitors.  相似文献   
105.
In this paper we present a novel technique to analyze stereo images generated from a SEM. The two main features of this technique are that it uses a binary linear programming approach to set up and solve the correspondence problem and that it uses constraints based on the physics of SEM image formation. Binary linear programming is a powerful tool with which to tackle constrained optimization problems, especially in cases that involve matching between one data set and another. We have also analyzed the process of SEM image formation, and present constraints that are useful in solving the stereo correspondence problem. This technique has been tested on many images. Results for a few wafers are included here.  相似文献   
106.
The performance of the DI segmented collector (SC)-LIGBT is compared to the collector shorted (CS)-LIGBT. The SC-LIGBT allows for adjusting the tradeoff between switching speed and on-state voltage drop by simply changing the P+ collector segment width during device layout. In contrast to previously reported junction isolated (JI) devices, the DI SC-LIGBT was observed to have a turnoff speed similar to the CS-LIGBT with a higher forward drop than the conventional LIGBT. The on-state performance of the integral diodes of the SC-LIGBTs was found to be superior to the integral diode of the CS-LIGBT. The integral diodes of both the CS and the SC-LIGBTs were found to have much superior switching characteristics compared to a lateral PiN diode at the expense of a higher on-state voltage drop. Thus, the superior switching characteristics of the integral diode in the SC-LIGBT complements its fast switching behavior making this device attractive for compact, high frequency, high efficient, power ICs.  相似文献   
107.
Human genome diversity studies analyse genetic variation among individuals and between populations in order to understand the origins and evolution of anatomically modern humans (Homo sapiens sapiens). The availability of thousands of DNA polymorphisms (genetic markers) brings analytic power to these studies. Human genome diversity studies have clearly shown that the large part of genetic variability is due to differences among individuals within populations rather than to differences between populations, effectively discrediting a genetic basis of the concept of 'race'. Evidence from paleontology, archaeology and genetic diversity studies is quite consistent with an African origin of modern humans more than 100,000 years ago. The evidence favors migrations out of African as the source of the original peopling of Asia, Australia, Europe and Oceania. An international program for the scientific analysis of human genome diversity and of human evolution has been developed. The Human Genome Diversity Project (HGDP) aims to collect and preserve biologic samples from hundreds of populations throughout the world, make DNA from these samples available to scientists and distribute to the scientific community the results of DNA typing with hundreds of genetic markers.  相似文献   
108.
Compressed sensing (CS) utilizes the sparsity of magnetic resonance (MR) images to enable accurate reconstruction from undersampled k-space data. Recent CS methods have employed analytical sparsifying transforms such as wavelets, curvelets, and finite differences. In this paper, we propose a novel framework for adaptively learning the sparsifying transform (dictionary), and reconstructing the image simultaneously from highly undersampled k-space data. The sparsity in this framework is enforced on overlapping image patches emphasizing local structure. Moreover, the dictionary is adapted to the particular image instance thereby favoring better sparsities and consequently much higher undersampling rates. The proposed alternating reconstruction algorithm learns the sparsifying dictionary, and uses it to remove aliasing and noise in one step, and subsequently restores and fills-in the k-space data in the other step. Numerical experiments are conducted on MR images and on real MR data of several anatomies with a variety of sampling schemes. The results demonstrate dramatic improvements on the order of 4-18 dB in reconstruction error and doubling of the acceptable undersampling factor using the proposed adaptive dictionary as compared to previous CS methods. These improvements persist over a wide range of practical data signal-to-noise ratios, without any parameter tuning.  相似文献   
109.
In this study, the effect of different vegetables baby corn, green pea, broccoli as filling ingredients along with yellowfin tuna (Thunnus albacares) on the heat penetration characteristics and quality changes were assessed. Heating and cooling lag factors (Jh and Jc) were least for tuna with broccoli and tuna without vegetables, respectively. Heating rate index was in the range of 13.5–19.3 min with least value for tuna with broccoli. Heat processing increased the hardness and chewiness of tuna significantly (< 0.05), whereas cohesiveness decreased. Thermal processing resulted in higher L*and hue (h) value for tuna. Substantial decrease in a* value was observed for tuna with broccoli and peas where as b* value showed an increase for tuna with baby corn. Tuna packed with green pea and baby corn was rated better sensorily, whereas tuna with broccoli was rated least.  相似文献   
110.
Liposomes play a significant role in encapsulation of various bioactive compounds (BACs), including functional food ingredients to improve the stability of core. This technology can be used for promoting an effective application in functional food and nutraceuticals. Incorporation of traditional and emerging methods for the developments of liposome for loading BACs resulted in viable and stable liposome formulations for industrial applications. Thus, the advance technologies such as supercritical fluidic methods, microfluidization, ultrasonication with traditional methods are revisited. Liposomes loaded with plant and animal BACs have been introduced for functional food and nutraceutical applications. In general, application of liposome systems improves stability, delivery, and bioavailability of BACs in functional food systems and nutraceuticals. This review covers the current techniques and methodologies developed and practiced in liposomal preparation and application in functional foods.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号