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   121篇
  免费   1篇
电工技术   1篇
化学工业   19篇
金属工艺   3篇
能源动力   1篇
轻工业   2篇
无线电   17篇
一般工业技术   6篇
冶金工业   53篇
自动化技术   20篇
  2023年   1篇
  2020年   2篇
  2019年   1篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2014年   3篇
  2013年   4篇
  2012年   1篇
  2011年   5篇
  2010年   8篇
  2009年   1篇
  2008年   3篇
  2007年   5篇
  2006年   3篇
  2005年   3篇
  2004年   1篇
  2003年   1篇
  2002年   4篇
  2000年   2篇
  1999年   3篇
  1998年   24篇
  1997年   11篇
  1996年   10篇
  1995年   3篇
  1994年   1篇
  1993年   5篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1978年   1篇
  1976年   2篇
  1973年   1篇
  1965年   1篇
排序方式: 共有122条查询结果,搜索用时 31 毫秒
11.
An adult, intact female Australian shepherd presented for frank vaginal bleeding of unknown duration. The only coagulation profile abnormality upon presentation was mild prolongation of the partial thromboplastin time (PTT). The uterus was removed at surgery and contained a large amount of coagulated blood. Clotting profiles were markedly abnormal 48 hours postoperatively. Serum analysis was positive for brodifacoum, an anticoagulant rodenticide. Preoperative coagulation was most likely normalized by vitamin K1 therapy administered prior to presentation. The only manifestation of anticoagulant rodenticide was hematometra. Rodenticide intoxication should be considered in the differential diagnosis list of hematometra or metrorrhagia.  相似文献   
12.
Very high activity and selectivity could be achieved for the direct oxidation of H2S into elemental sulfur at low reaction temperature (40–60°C), on nickel sulfide supported SiC catalyst. The heterogeneous nature of the support surface (hydrophilic and hydrophobic areas) could explain the important role played by water to maintain a high and stable H2S conversion level. The formation of a very active superficial nickel oxysulfide phase was proposed in order to explain the activation period necessary at reaction temperatures <60°C. Total selectivity for sulfur was attributed to the very low reaction temperature and the absence of any microporosity in the support.  相似文献   
13.
Wireless local area networks (WLAN??s) based on the 802.11 standards are ubiquitous. However, the popularity of WLAN??s has made interference between WLAN users an issue. Spatial division multiple access (SDMA) is one way to orthogonalize these users and reduce interference. The contribution of this paper is to use real antenna array prototypes to determine the best array design for implementing indoor SDMA. Two SDMA antenna array prototypes are constructed and used to collect propagation measurements in an indoor environment. The propagation data is then incorporated into an SDMA orthogonal frequency division multiplexing (OFDM) analysis. This approach is able to very accurately predict how the two array designs will influence SDMA-OFDM performance in the indoor environment where the measurements are collected. The results indicate that the compact sectorized antenna array prototype performs better than the linear array prototype for in-room communication and that the reverse is true for inter-room communication.  相似文献   
14.
Doxycycline medicated feed was administered to healthy fattening pigs for an 8-day period either for 1 h every 12 h or ad libitum. The average dosage regimen ranged between 11.8 and 13.3 mg/kg/day. Doxycycline concentrations were determined in plasma, lung and nasal mucosa using a high performance liquid chromatography assay (HPLC). The agreement between the doxycycline HPLC assay and a bioassay was also assessed in plasma. Following the multiple medicated feed administration every 12 h, the plasma concentrations were best described by a one-compartmental model with first-order absorption. Steady-state plasma concentrations ranged between 0.7 and 1 microgram/mL. The mean accumulation factor and elimination half-life were, respectively, 1.8 +/- 0.4 and 5.9 +/- 1.0 h. Following ad libitum administration of medicated feed, steady-state plasma concentrations ranged between 0.9 and 1.5 micrograms/mL. At the end of the treatment, the doxycycline lung and nasal mucosa concentrations were 1.7 +/- 0.4 micrograms/g and 2.9 +/- 0.6 micrograms/g, respectively. These data validate the dosage regimen tested in order to control pig respiratory infections, provided that controlled clinical studies are confirmatory.  相似文献   
15.
To test the hypothesis that a greater proportion of women than men react to methacholine challenge and investigate the possible reasons for any differences observed, we recruited 495 subjects 20 to 44 yr of age (50.9% male) in Paris and 304 subjects (51.3% male) in Montpellier (France), as part of the European Community Respiratory Health Survey. The proportion of responders (PD20 < or = 4 mg methacholine) was 33.7% in women and 11.9% in men (odds ratio = 3.8; 95% confidence interval = 2.4-6.0) in Paris and 43.2% in women and 29.5% in men (odds ratio = 1.8; 95% confidence interval = 1.1-2.9) in Montpellier. These differences could not be explained by asthma, respiratory symptoms, atopy, or lung function parameters. In stepwise logistic regressions including sex, asthma, and asthma-like symptoms, nasal allergies, atopy, baseline FEV1, FEV1%pred, FVC, and FEV1%FVC, the odds-ratios for the effect of female sex on PD20 < or = 4 mg methacholine were 5.2 (3.0-9.0) in Paris and 2.2 (1.2-3.8) in Montpellier. Reacting to low doses of methacholine (PD20 < or = 0.5 mg) was associated with asthma and atopy in both men and women. In contrast, reacting to doses between 0.5 and 4 mg was associated with asthma and atopy only in men and with heavy tobacco consumption only in women. We conclude that the excess of hyperresponsiveness in women is not due to their having smaller lung size or airway caliber than men and may be related to a greater susceptibility to smoking.  相似文献   
16.
Laser-induced breakdown spectroscopy is used to measure chromium concentration in soil samples. A comparison is carried out between the calibration curve method and two chemometrics techniques: partial least-squares regression and neural networks. The three quantitative techniques are evaluated in terms of prediction accuracy, prediction precision, and limit of detection. The influence of several parameters specific to each method is studied in detail, as well as the effect of different pretreatments of the spectra. Neural networks are shown to correctly model nonlinear effects due to self-absorption in the plasma and to provide the best results. Subsequently, principal components analysis is used for classifying spectra from two different soils. Then simultaneous prediction of chromium concentration in the two matrixes is successfully performed through partial least-squares regression and neural networks.  相似文献   
17.
In this work, the polishing‐induced contamination layer at the fused silica optics surface was studied with various interface analysis techniques: Secondary Ion Mass Spectroscopy (SIMS), Electron Probe Microanalysis (EPMA), X‐Ray Photoelectron Spectroscopy (XPS), and Inductively Coupled Plasma—Optical Emission Spectroscopy (ICP‐OES). Samples were prepared using an MRF polishing machine and cerium‐based slurry. The cerium and iron penetration and concentration were measured in the surface out of defects. Cerium is embedded at the surface in a 60 nm layer and concentrated at 1200 ppmw in this layer while iron concentration falls down at 30 nm. Spatial distribution and homogeneity of the pollution were also studied in the scratches and bevel using SIMS and EPMA techniques. We saw evidence that surface defects, such as scratches, are specific places that hold the pollutants. This overconcentration is also observed in the chamfer. These new insights into the polishing‐induced contamination of fused silica optics and it repartition have been obtained using various characterization methods. Advantages and disadvantages of each one are discussed.  相似文献   
18.
We have studied the heteroepitaxial growth of Zn(Mg)BeSe alloys on both GaAs and Si substrates. X-ray measurements show that ZnMgBeSe quaternary alloys can be grown with a high structural quality on GaAs(001). Linewidths as low as to 20 arcsec have been obtained from double x-ray diffraction and the etch pit density is in the range of 10−3 cm−2. The growth of ZnBeSe ternary alloys on vicinal Si(001) substrates has been investigated. Optical properties of Zn0.55Be0.45Se which is lattice-matched to silicon have been studied by photoluminescence and reflectivity and a fundamental bandgap E0 of 3.85 eV has been measured. Therefore, this material is a potential candidate for ultraviolet B detection. However, it is important to note that these measurements are not conclusive about the direct nature of alloys bandgaps.  相似文献   
19.
20.
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