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   2160篇
  免费   135篇
电工技术   13篇
综合类   1篇
化学工业   679篇
金属工艺   17篇
机械仪表   51篇
建筑科学   80篇
矿业工程   5篇
能源动力   54篇
轻工业   621篇
水利工程   16篇
石油天然气   15篇
无线电   84篇
一般工业技术   272篇
冶金工业   243篇
原子能技术   1篇
自动化技术   143篇
  2024年   5篇
  2023年   28篇
  2022年   137篇
  2021年   139篇
  2020年   73篇
  2019年   89篇
  2018年   83篇
  2017年   96篇
  2016年   80篇
  2015年   57篇
  2014年   123篇
  2013年   169篇
  2012年   151篇
  2011年   162篇
  2010年   106篇
  2009年   101篇
  2008年   97篇
  2007年   103篇
  2006年   72篇
  2005年   44篇
  2004年   50篇
  2003年   32篇
  2002年   29篇
  2001年   14篇
  2000年   27篇
  1999年   16篇
  1998年   25篇
  1997年   17篇
  1996年   23篇
  1995年   14篇
  1994年   18篇
  1993年   12篇
  1992年   12篇
  1991年   4篇
  1990年   8篇
  1989年   6篇
  1988年   8篇
  1987年   8篇
  1986年   13篇
  1985年   8篇
  1984年   3篇
  1983年   7篇
  1982年   7篇
  1981年   4篇
  1980年   3篇
  1979年   2篇
  1977年   3篇
  1970年   1篇
  1940年   1篇
  1928年   1篇
排序方式: 共有2295条查询结果,搜索用时 15 毫秒
41.
The aim of this study is to evaluate the ability of physical training in the maintenance of muscle strength in rats with HFD (high-fat diet) after OVX (ovariectomy). Eighty Wistar rats are at eight weeks of age and weight 200 g which divided into 8 groups (n = 10) and treated for 12 weeks: GA: OVX + ND (normal diet), GB: OVX + ND + training, GC: sham + ND, GD: sham + ND + training, GE: OVX + HFD, GF: OVX + HFD + training, GG: sham + HFD and GH: sham + HFD + training. HFD consists of standard ration for rats with addition of 30% lipids. In training groups, physical training five training/week was conducted on a treadmill with adaptation period of three weeks up to 18 m/s for one hour, training were performed for 12 weeks. The sedentary animals remained in individual box. To analyze the effects of training and diet, tensile strength tests of the gastrocnemius muscles were conducted: the speed of 0.1 mm/min. Analysis of variance was performed to compare groups. The mean (SD) obtained for the maximum load (N) were: GA 57.77 (6.89), GB 62.74 (5.07), GC 49.45 (6.06), GD 59.42 (5.26) and GE 55.58 (4.72), GF 62.50 (4.56), GG 58.35 (4.54) and GH 56.67 (5.87), respectively. There were no differences for maximum load between surgeries (p = 0.004) and between treatments (p = 0.000). Differences were found also for the relationship surgery diet treatment (p = 0.007). For the variable stiffness (N/mm), there were not statistically significant differences: GA 5.03 (0.72), GB 5.08 (1.09), GC 5.17 (0.53), GD 5.35 (0.80), GE 5.52 (1.20), GF 5.36 (1.07), GG 4.83 (1.03) and GH 5.40 (0.73). For the toughness (N/mm), there were differences between treatments (p = 0.010) and the ratio diet treatment (p = 0.024): GA 455.00 (107.21), GB 541.96 (126.80), GC 394.97 (84.67), GD 566.90 (157.07); GE 424.63 (113.03), GF 478.07 (106.03); GG 517.44 (98.65?  相似文献   
42.
Plant-derived products and their extracted compounds have been used in folk medicine since early times. Zimbro or common juniper (Juniperus communis) is traditionally used to treat renal suppression, acute and chronic cystitis, bladder catarrh, albuminuria, leucorrhea, and amenorrhea. These uses are mainly attributed to its bioactive composition, which is very rich in phenolics, terpenoids, organic acids, alkaloids, and volatile compounds. In the last few years, several studies have analyzed the huge potential of this evergreen shrub, describing a wide range of activities with relevance in different biomedical discipline areas, namely antimicrobial potential against human pathogens and foodborne microorganisms, notorious antioxidant and anti-inflammatory activities, antidiabetic, antihypercholesterolemic and antihyperlipidemic effects, and neuroprotective action, as well as antiproliferative ability against cancer cells and the ability to activate inductive hepato-, renal- and gastroprotective mechanisms. Owing to these promising activities, extracts and bioactive compounds of juniper could be useful for the development of new pharmacological applications in the treatment of several acute and chronic human diseases.  相似文献   
43.

Rational use of cars in smart cities can represent an economical and cheaper way to decrease the quantity of cars on the roads to better the life quality of the populations. This paper presents a low-cost deployment proposal called “URCa project” to reach these goals and proposes a paradigm change by sharing the cars considering some logistic aspects including car ride mechanism. Technical feasibility to deploy this solution was checked by means of a proof of concept. The concept was proven by passenger counting and license plate that are essential information in this solution were obtained taking photographs, applying two types of recognition algorithms and sending the results to be stored and evaluated by analytic data processes of a transit regulatory agency showing that this project is technically viable. The low-cost solution was justified by a financial analysis based on both costs (URCa solution and a bridge) that has shown a ratio of 1:10,000.

  相似文献   
44.
45.
Examined the role of counterfactual thinking in 2 emotions: shame and guilt. In 1 series of studies, Ss read about situations evocative of shame and guilt or described personal experiences of guilt or shame. They then generated counterfactual alternatives to "undo" the distressing outcomes. Consistent with predictions derived from J. P. Tangney (see record 1992-05447-001), Ss tended to undo shame situations by altering qualities of the self and to undo guilt situations by altering actions. In a 2nd series of studies, Ss imagined themselves in a situation that could evoke either guilt or shame. Ss were then led to mutate the self or behavior to undo the situation. Mutation manipulations amplified shame and guilt such that the former Ss anticipated feeling greater shame, whereas the latter anticipated feeling greater guilt. The role of counterfactual thinking in specific emotions and in differentiating shame and guilt-prone personalities is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
46.
A nonlinear dynamics framework that has been applied successfully to several laboratory idealizations of rhythmic behaviors was applied to a more naturally occurring behavior, clapping. Inertial loading of limbs and frequency of oscillation were manipulated. Displacement of relative phase from perfectly in phase and the variability of relative phase, both of which are used as indexes of coordination dynamics, increased with greater inertial imbalance between limbs. Increasing frequency exaggerated these effects. These hallmark properties of coupled oscillator dynamics appeared whether or not the hands contacted, albeit with the latter condition revealing a significant asymmetry in the dynamics. Results highlight the generality of the coupled oscillator regime in interlimb coordination as well as its appropriateness for characterizing behaviors that involve contact of limb surfaces and suggest one way in which perceptual information may tune the dynamical regime. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
47.
Emerging deep learning-based applications in precision medicine include computational histopathological analysis. However, there is a lack of the required training image datasets to generate classification and detection models. This phenomenon occurs mainly due to human factors that make it difficult to obtain well-annotated data. The present study provides a curated public collection of histopathological images (DeepHP) and a convolutional neural network model for diagnosing gastritis. Images from gastric biopsy histopathological exams were used to investigate the performance of the proposed model in detecting gastric mucosa with Helicobacter pylori infection. The DeepHP database comprises 394,926 histopathological images, of which 111 K were labeled as Helicobacter pylori positive and 283 K were Helicobacter pylori negative. We investigated the classification performance of three Convolutional Neural Network architectures. The models were tested and validated with two distinct image sets of 15% (59K patches) chosen randomly. The VGG16 architecture showed the best results with an Area Under the Curve of 0.998%. The results showed that CNN could be used to classify histopathological images from gastric mucosa with marked precision. Our model evidenced high potential and application in the computational pathology field.  相似文献   
48.
Films based on polylactic acid (PLA) reinforced with multi‐walled carbon nanotubes (MWCNT) were developed after using an excellent methodology to ensure an optimum dispersion of the filler in the matrix. The functionalization of MWCNT was carried out through a Fenton reaction to generate hydroxyl (OH) and carboxyl (COOH) groups on their walls. After that, COOH groups were lengthened by reacting with thionyl chloride and then with triethylene glycol to achieve a terminal OH distanced from the wall of the MWCNT. Nanocomposites based on PLA containing different concentrations of functionalized filler (fMWCNT: 0.026, 0.10, and 0.18 wt%) were prepared by casting. The influence of filler concentration was investigated using some techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), water vapor permeability (WVP) and uniaxial tensile mechanical properties. Excellent dispersion of fMWCNT was observed suggesting that the technique of functionalization used was appropriate. All nanocomposites presented great stability, allowing them to be processed to temperatures reaching 300°C. Furthermore, an increasing trend of ultimate tensile strength (σu) up to 20% and a decrease of WVP around 40% with the addition of only 0.10 wt% of fMWCNT were obtained. Considering these results, the new biodegradable nanocomposites developed in this work could be very promising to replace synthetic plastics that currently are used in different areas such as nanotechnology, packaging and biomedicine. POLYM. COMPOS., 37:3066–3072, 2016. © 2015 Society of Plastics Engineers  相似文献   
49.
Zinc oxide (ZnO) is an inorganic compound widely used in everyday applications. ZnO is currently listed as a generally recognized as safe (GRAS) material by the Food and Drug Administration and is used as food additive. The advent of nanotechnology has led the development of materials with new properties for use as antimicrobial agents. Thus, ZnO in nanoscale has shown antimicrobial properties and potential applications in food preservation. ZnO nanoparticles have been incorporated in polymeric matrices in order to provide antimicrobial activity to the packaging material and improve packaging properties. This review presents the main synthesis methods of ZnO nanoparticles, principal characteristics and mechanisms of antimicrobial action as well as the effect of their incorporation in polymeric matrices. Safety issues such as exposure routes and migration studies are also discussed.  相似文献   
50.
The synthesis, structural characterization, photo and electroluminescence, thermal and electrochemical properties of a new fluorinated fluorene-containing copolymer are described. The copolymer is formed by alternating mers of [2,3,5,6 tetrafluoro-1,4 phenylene] and [9,9′-dihexyl-2,7 fluorene] and emits blue light with low turn on voltages. The EL performance of the fluorinated copolymer was superior to those of the non-fluorinated analog copolymer and of the corresponding poly(9,9′dihexyl-2,7 polyfluorene) homopolymer.  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