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   283篇
  免费   24篇
电工技术   5篇
化学工业   85篇
金属工艺   13篇
机械仪表   7篇
建筑科学   18篇
能源动力   3篇
轻工业   51篇
无线电   21篇
一般工业技术   54篇
冶金工业   14篇
原子能技术   3篇
自动化技术   33篇
  2023年   5篇
  2022年   7篇
  2021年   8篇
  2020年   4篇
  2019年   11篇
  2018年   11篇
  2017年   5篇
  2016年   18篇
  2015年   14篇
  2014年   19篇
  2013年   25篇
  2012年   18篇
  2011年   29篇
  2010年   24篇
  2009年   19篇
  2008年   20篇
  2007年   16篇
  2006年   12篇
  2005年   8篇
  2004年   5篇
  2003年   4篇
  2002年   9篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   2篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   4篇
排序方式: 共有307条查询结果,搜索用时 218 毫秒
291.
Photoreactive analogues of substance P (biotin sulfone-spacer (amino pentanoic or Gly(3))-Arg-Pro-Lys-Pro-(pBzl)Phe-Gln-Phe-Phe-Gly-Leu-Met(O(2))NH(2)) with or without isotope (deuterium) labeling have been synthesized. Deuteriums were present on (d)-biotin or epibiotin sulfone (D(3)), on the Gly(3) spacer linker (D(6)), or on the Gly in position 9 of SP (D(2)). Therefore, peptide analogues could be either unlabeled or tri-, penta-, or hexadeuterated. Results obtained with the use of these peptide analogues show that (d)-biotin sulfone and epibiotin sulfone are not recognized with the same affinity by streptavidin, with (d)-biotin sulfone displaying better affinity for the protein. Photolabeling of the human NK-1 receptor with a 1:1 molar ratio of nondeuterated and deuterated photoreactive substance P (SP) analogues in position 5, followed by combined digestions, purification, and MALDI-TOF mass spectrometry analysis, made the identification of the domain of the receptor covalently linked by the photoreactive SP analogue easier. Indeed, doublets in mass spectra were specific for the covalent complex whereas single peaks could be attributed to contaminating species. This method is particularly suitable when minute amounts of complex have to be analyzed, as in the case of highly hydrophobic G-protein coupled receptors.  相似文献   
292.
The aim of this paper is to study a 2 × 2 Multiple-Input Multiple-Output (MIMO) with antenna’s coupling phenomena at the transmitters and at the receivers. The single motivation of this study is to show how to choose a couple of couplings in order to reach a fixed Signal to Noise Ratio according to the application considered. It is shown, that a certain combination of couplings can make the system more powerful.  相似文献   
293.
INTRODUCTION: Non-fatal road casualties are under-reported, with official figures coming from the police. In the French Rh?ne county, a road trauma registry constitutes a second source of reporting but its completeness needs to be assessed. We also wish to estimate an incidence rate of non-fatal road casualties that is corrected for under-count. METHODS: Having two sources of reporting available, we can apply the capture-recapture method under certain conditions. To take into account different reporting probabilities among casualties, the capture-recapture analysis is stratified according to injury severity (New Injury Severity Score=NISS), road user type and human third party. To evaluate the sensitivity of the capture-recapture estimate on the number of matched casualties between the police file and the registry, three scenarios of record-linkage are considered. RESULTS: For serious (NISS 9+) non-fatal road casualties, the police ascertainment rate is at most 57%, the registry ascertainment rate is at most 87%, and the aggregate ascertainment rate is at most 95%. The ascertainment-corrected incidence rate for serious (NISS 9+) non-fatal road casualties is at least 65 per 100,000. CONCLUSION: The degree of completeness of the registry for serious casualties is rather high, though not satisfactory.  相似文献   
294.
Robust 3-D modeling of vasculature imagery using superellipsoids   总被引:1,自引:0,他引:1  
This paper presents methods to model complex vasculature in three-dimensional (3-D) images using cylindroidal superellipsoids, along with robust estimation and detection algorithms for automated image analysis. This model offers an explicit, low-order parameterization, enabling joint estimation of boundary, centerlines, and local pose. It provides a geometric framework for directed vessel traversal, and extraction of topological information like branch point locations and connectivity. M-estimators provide robust region-based statistics that are used to drive the superellipsoid toward a vessel boundary. A robust likelihood ratio test is used to differentiate between noise, artifacts, and other complex unmodeled structures, thereby verifying the model estimate. The proposed methodology behaves well across scale-space, shows a high degree of insensitivity to adjacent structures and implicitly handles branching. When evaluated on synthetic imagery mimicking specific structural complexities in tumor microvasculature, it consistently produces ubvoxel accuracy estimates of centerlines and widths in the presence of closely-adjacent vessels, branch points, and noise. An edit-based validation demonstrated a precision level of 96.6% at a recall level of 95.4%. Overall, it is robust enough for large-scale application.  相似文献   
295.
Olive mill by-products are effluents generated during olive oil production process. The two-phase centrifugation system produces a semi-solid olive pomace called “alperujo.” This by-product is a combination of liquid and solid wastes derived from the three-phase manufacturing process. A direct and fast analytical method by ultra-high-pressure liquid chromatography-DAD coupled with ESI/MS-MS has been developed for the profiling of phenolic compounds. Thirty-five metabolites belonging to phenyl alcohols, secoiridoids, flavonoids, and iridoids were identified as the main constituents of alperujo in 12 min, including p-coumaroyl aldarate and a verbascoside derivative found for the first time in alperujo and a new ligstroside derivative. Six quantitatively significant components were determined at concentrations ranging from 17.7 mg/L for p-coumaric acid to 370.7 mg/L for hydroxytyrosol. Our data confirm that alperujo is an interesting source of phenolic compounds that could be extracted for use as nutraceuticals.  相似文献   
296.
In vitro and in situ anti-listerial properties of 3 strains of Facultative Anaerobic Halophilic and Alkaliphilic (FAHA) species, i.e. Alkalibacterium kapii ALK 6, Marinilactibacillus psychrotolerans ALK 9 and Facklamia tabacinasalis ALK 1, were investigated. The 3 strains were isolated from a smear ecosystem originating from a commercial Raclette type cheese and exhibiting strong anti-listerial activity in situ on cheese surface.In a first step, strains were tested in vitro for production of antimicrobial compounds against Listeria innocua 81000-1 and Listeria ivanovii HPB 28. M. psychrotolerans ALK 9 inhibited both indicator strains in spot-on-the-lawn tests while A. kapii ALK 6 showed no inhibiting effect. F. tabacinasalis ALK 1 exerted an in vitro inhibition on L. ivanovii HPB 28, but induced the formation of dense ball-shaped microcolonies of L. innocua 81000-1 in the soft agar, a typical biofilm microstructure. The extent of the biofilm zone was enhanced when F. tabacinasalis ALK 1 and M. psychrotolerans ALK 9 were tested together.In a second step, different combinations of strains were applied on Raclette cheeses ripened at pilot scale and contaminated with 50 cfu/cm2L. innocua at day 7. A control flora of 6 strains, isolated from ecosystem F and corresponding to species commonly found on smear cheeses, was applied on control and test cheeses. In test cheeses, we investigated the impact on Listeria growth of the addition of the 3 FAHA strains, applied as single or mixed cultures. A 1-log inhibition was obtained at day 15 on cheeses treated with FAHA strains applied either as single or mixed cultures. This 1-log inhibition was correlated with the development of FAHA species that reached their maximal count at day 15.This study suggests that the development of FAHA species in early ripening likely contributes to the initial part of the in situ inhibition exerted by the complex cheese surface ecosystem investigated.  相似文献   
297.
The deuteration of a diverse group of silanes: alkyl‐, aryl‐, alkoxy‐ and chlorosilanes, siloxane and silazane, under an atmosphere of dideuterium (D2) was explored with ruthenium bis(dihydrogen) dihydride complexes and hydrated metal salts. Deuterium incorporation of greater than 97% for the silanes O(SiMe2H)2, Et3SiH, (EtO)3SiH and Me2ClSiH was possible with 0.1 mol% of the ruthenium complex [RuH22‐H2)2(PCyp3)2] [0.05 mol% for O(SiMe2H)2] when catalysis was conducted in the neat silane at 30 °C under 1 bar of D2 for 3.5 h. The air‐stable ruthenium trichloride salt RuCl3⋅x H2O was also an efficient catalyst for the deuteration of O(SiMe2H)2 and Et3SiH; deuterium incorporations for the two silanes of 93% and 90%, respectively, were possible under the same conditions as for [RuH22‐H2)2(PCyp3)2] with 0.1% catalyst loading. Hydrogen–deuterium exchange of O(SiMe2H)2 catalyzed by the rhodium trichloride (RhCl3⋅x H2O) and iridium trichloride (IrCl3⋅x H2O) was similarly efficient as with RuCl3⋅x H2O although catalytic alacrity dropped for Et3SiH.

  相似文献   

298.
Near infrared (NIR) spectroscopy was used to predict colour of European Emmental cheese samples. Colour values (L, a and b) were measured on 20 Emmental cheese samples using a Hunter-lab D25-D-2 optical head in the system according to Hunter to determine L (brightness), a (green-red component) and b (blue-yellow component). The diffuse reflectance of the investigated cheeses was also determined by a Büchi NIR Lab N-200 spectrometer using a rotating measuring cell in the range of 1000–2500 nm. The best results for L-value (squared correlation coefficient (R 2) = 0.56, root mean square error of cross-validation (RMSECV) = 0.76, ratio of prediction deviation (RPD) = 1.89 and range error ratio (RER) = 7.91), a-value (R 2 = 0.72, RMSECV = 0.15, RPD = 1.98 and RER = 7.6) and b-value (R 2 = 0.82, RMSECV = 0.52, RPD = 2.56 and RER = 9.42) were obtained when the first 12 principal components (PCs) of the principal component analysis (PCA) applied on normalised NIR spectra were used. It can be concluded that NIR spectroscopy could be used to predict b-value. The a- and L-values can also be predicted from NIR technique with approximate quantitative prediction.  相似文献   
299.
Water deficit causes substantial yield losses that climate change is going to make even more problematic. Sustainable agricultural practices are increasingly developed to improve plant tolerance to abiotic stresses. One innovative solution amongst others is the integration of plant biostimulants in agriculture. In this work, we investigate for the first time the effects of the biostimulant –Leafamine®–a protein hydrolysate on greenhouse lettuce (Lactuca sativa L.) grown under well-watered and water-deficit conditions. We examined the physiological and metabolomic water deficit responses of lettuce treated with Leafamine® (0.585 g/pot) or not. Root application of Leafamine® increased the shoot fresh biomass of both well-watered (+40%) and deficit-irrigated (+20%) lettuce plants because the projected leaf area increased. Our results also indicate that Leafamine® application could adjust the nitrogen metabolism by enhancing the total nitrogen content, amino acid (proline) contents and the total protein level in lettuce leaves, irrespective of the water condition. Osmolytes such as soluble sugars and polyols, also increased in Leafamine®-treated lettuce. Our findings suggest that the protective effect of Leafamine is a widespread change in plant metabolism and could involve ABA, putrescine and raffinose.  相似文献   
300.
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