首页 | 官方网站   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   280篇
  免费   14篇
工业技术   294篇
  2023年   7篇
  2022年   3篇
  2021年   15篇
  2020年   17篇
  2019年   9篇
  2018年   11篇
  2017年   13篇
  2016年   13篇
  2015年   5篇
  2014年   6篇
  2013年   22篇
  2012年   24篇
  2011年   20篇
  2010年   32篇
  2009年   27篇
  2008年   20篇
  2007年   21篇
  2006年   17篇
  2005年   5篇
  2001年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1994年   1篇
排序方式: 共有294条查询结果,搜索用时 31 毫秒
31.
In this paper, five novel and minimum number count floating inductor simulators (FIs) are proposed. Three of the presented FIs depending on the passive component choice can provide parallel R–L, (–R)–(–L) and series R–L, (–R)–(–L) from the same configuration while other two provide one of parallel R–L or series R–L. Some of the introduced positive lossy inductor simulators employ a grounded capacitor; accordingly, they are convenient for integrated circuit (IC) implementation. So as to exhibit the performance of the proposed structures, computer simulations based on SPICE program are given.  相似文献   
32.
In this paper, a number of simulated floating inductors (FIs) employing second-generation current conveyor (CCII), current-feedback operational amplifier (CFOA), differential voltage current conveyor (DVCC) and differential difference current conveyor (DDCC) are proposed. They employ only a grounded capacitor; accordingly, they are suitable for integrated circuit (IC) implementation. Some of the developed FI simulators demonstrate the feature of improved low-frequency performance while the other ones suffer from the Z/Y terminal parasitic resistors bringing extra series resistors to the inductances of the simulated FIs. Two novel methods for reducing/eliminating the unwanted series resistance in equivalent inductances of the FIs are developed, one of which is called the direct design technique accomplished by adjusting the resistive component/components of the FIs. The series resistors of the FIs affecting their low-frequency performance can be canceled by adding floating negative resistors in series, which is another method. Three of the presented FIs as examples are chosen in order to verify the developed method, perform their simulations and show their performance.  相似文献   
33.
Sea food is a major source of animal protein. Marine foods are very rich sources of mineral components. The total content of minerals in the raw flesh of marine fish and invertebrates is in the range of 0.6–1.5% wet weight. The contents of Na, K, Ca, Mg and P are up to 1 mg/100 g, whereas those of Fe, Zn, I are less than 1 mg/100 g. Mussels (Mytilus galloprovincialis) were investigated for macro and trace element composition throughout the year. Ranges of moisture, ash, protein and fat contents were 79.76–87.46 g/100 g, 1.06–2.06 g/100 g, 7.28–12.65 g/100 g and 0.33–3.49 g/100 g, respectively. While the highest protein and fat values were found in the summer (July–August), the highest moisture and ash contents were found in the winter (December–January). The contents of highest Na, K, Ca were found in the summer. Cadmium, lead and copper were found to be below the legislative limits throughout year. High levels of mercury were found in January and October. It should be discussed whether mussel may provide an alternative source of mineral for healthy nutrition.  相似文献   
34.
In this paper, two new circuit configurations for realizing voltage‐mode (VM) all‐pass sections (APSs) are presented. The proposed circuits employ only two differential voltage current conveyors (DVCCs) and are cascadable with other VM circuits due to their high‐input and low‐output impedances. The first configuration uses a grounded resistor and a grounded capacitor without requiring matching constraints, whereas the second employs two grounded resistors and a grounded capacitor with a single matching condition. While the first configuration can realize only one all‐pass response, the second can provide inverting and non‐inverting all‐pass responses with selection of appropriate input port. Adding two grounded resistors to the proposed filters, variable gain APSs can also be obtained. As applications, two quadrature oscillators, each of which using one of the proposed all‐pass circuits, one grounded resistor and one grounded capacitor are presented. SPICE simulation results are included to verify the theory. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
35.
The effect of plant extract (bay leaf, rosemary, black cumin seed and lemon oil) treatment on the shelf life of vacuum-packaged fish was studied. Hot smoked rainbow trout was treated with 1 % plant extracts, and their shelf lives were compared with those of control (only vacuum packaged) samples. Samples were stored at 2 °C and sensory evaluation as well as chemical and microbiological analyses were conducted weekly. The control group was spoiled after four weeks of storage. In contrast the addition of plant extracts decreased microbiological activity. The results obtained from this study showed that the shelf life of hot smoked trout stored in cold storage (+2 °C), as determined by overall acceptability of all data, was 6 weeks for rosemary, black cumin seed, and lemon oil treatment plus vacuum packaged fish and 7 weeks for bay leaf oil treatment plus vacuum packaged smoked fish.  相似文献   
36.
The aim of this study was to examine the use of liposome in the dyeing of wool and mohair fibres with acid dyestuffs. Soybean lecithin and cholesterol were used to form the liposome membrane utilised in the dyebath. Liposome production was performed according to the thin lipid layer method (Bangham Method) using a rotary evaporator. Two different forms of liposome were used for dyeing wool and mohair fibres. In its first form, liposome was utilised as an auxiliary agent, where it was added to a conventional dyebath at the beginning of the process. In its second form, dyes were encapsulated with liposome and then used in dyeing. The effects of these two different forms of liposome were compared with conventional dyeing. Dyeing was carried out at depths of shade of 0.5%, 1.0% and 2.0% using three different concentrations of liposome (0.33%, 0.66% and 1.33%). An analysis of K/S values, fastness to washing, and the alkali solubility of fibres was conducted. The fibre samples dyed in the presence of liposome exhibited very good fastness to light (grade 8). The wash fastness test results of the liposomal‐dyed samples were significantly better (grade 4‐5) than for those samples which were conventionally dyed. In the presence of liposome, the tensile strength of fibres was 20 gf, whereas it was 11 gf without liposomes.  相似文献   
37.
38.
Different samples of xTeO2.(25-y)B2O3.zV2O5.yYb2O3 (or TBVY) new glass material were synthesized by the classical melt-quenching method. Structural, optical, physical, and thermal analyses of the synthesized glasses were performed in addition to Monte Carlo simulation to test radiation shielding properties. The results showed that increasing ratios of Yb2O3 (y = 0.0, 0.5, 1.0, and 1.5 mol%) produced monotonic density values of the synthesized glasses ranging from 4.70058 g cm?3 to 5.01038 g cm?3. XRD and FTIR analyses were used to confirm the glass structure of all samples. Optical transmittance and absorption parameters varied almost monotonically with increasing ratios of Yb2O3 indicating the ability to predict and control these properties using Yb2O3 additive. Furthermore, simulated radiation interaction parameters, such as attenuation coefficients and half-value layer, exhibited well-behaved dependence on the concentration ratio of the Yb2O3 additive. This approach to glass material synthesis demonstrate the useful synergetic effect of combining structural, optical, and radiation characteristics.  相似文献   
39.
Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response, compared to conventional tin‐doped indium oxide (ITO) electrodes, are shown. Optimized IZRO films feature a very high electron mobility (up to ≈77 cm2 V?1 s?1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω □?1 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO. Fundamentally, it is found that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr‐doping. Overall, on a four‐terminal perovskite/silicon tandem device level, an absolute 3.5 mA cm?2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO, resulting in improving the PCE from 23.3% to 26.2%.  相似文献   
40.
Defects at the surface and grain boundaries of metal–halide perovskite films lead to performance losses of perovskite solar cells (PSCs). Here, organic cyano‐based π‐conjugated molecules composed of indacenodithieno[3,2‐b]thiophene (IDTT) are reported and it is found that their cyano group can effectively passivate such defects. To achieve a homogeneous distribution, these molecules are dissolved in the antisolvent, used to initiate the perovskite crystallization. It is found that these molecules are self‐anchored at the grain boundaries due to their strong binding to undercoordinated Pb2+. On a device level, this passivation scheme enhances the charge separation and transport at the grain boundaries due to the well‐matched energetic levels between the passivant and the perovskite. Consequently, these benefits contribute directly to the achievement of power conversion efficiencies as high as 21.2%, as well as the improved environmental and thermal stability of the PSCs. The surface treatment provides a new strategy to simultaneously passivate defects and enhance charge extraction/transport at the device interface by manipulating the anchoring groups of the molecules.  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-23

京公网安备 11010802026262号