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   2376篇
  免费   185篇
电工技术   13篇
综合类   1篇
化学工业   763篇
金属工艺   13篇
机械仪表   28篇
建筑科学   107篇
矿业工程   7篇
能源动力   38篇
轻工业   757篇
水利工程   19篇
石油天然气   20篇
无线电   87篇
一般工业技术   325篇
冶金工业   187篇
原子能技术   9篇
自动化技术   187篇
  2024年   3篇
  2023年   14篇
  2022年   91篇
  2021年   135篇
  2020年   66篇
  2019年   54篇
  2018年   69篇
  2017年   76篇
  2016年   92篇
  2015年   73篇
  2014年   100篇
  2013年   175篇
  2012年   154篇
  2011年   211篇
  2010年   129篇
  2009年   146篇
  2008年   136篇
  2007年   128篇
  2006年   92篇
  2005年   85篇
  2004年   70篇
  2003年   69篇
  2002年   58篇
  2001年   29篇
  2000年   19篇
  1999年   27篇
  1998年   29篇
  1997年   26篇
  1996年   28篇
  1995年   22篇
  1994年   25篇
  1993年   21篇
  1992年   14篇
  1991年   5篇
  1990年   7篇
  1989年   9篇
  1988年   10篇
  1987年   3篇
  1986年   7篇
  1985年   7篇
  1984年   4篇
  1983年   9篇
  1982年   6篇
  1981年   4篇
  1979年   4篇
  1978年   3篇
  1977年   8篇
  1975年   2篇
  1974年   2篇
  1965年   1篇
排序方式: 共有2561条查询结果,搜索用时 31 毫秒
81.
A fast and reliable method for anthocyanin extraction and identification by HPLC‐DAD‐ESI/MS‐QTOF was used to analyse the anthocyanin composition of commercial red fruit juices (blackberry, redcurrant and pomegranate), purees (strawberry, cherry and raspberry) and concentrates (elderberry, blueberry and red grape). The anthocyanin profile of black carrot juice is also reported. The extraction and analysis method allowed us to detect and quantify a wide range of individual anthocyanins in a simple and rapid way. Pelargonidin‐3‐glucoside was detected in redcurrant for the first time and petunidin‐3‐galactoside quantified for the first time in blueberries. Considering the health benefits that have been associated with anthocyanin consumption, all these fruit and vegetables processed products could appear as a good source of this group of phytochemical compounds for their direct consumption or their use as ingredients for the design of new food product or food supplements.  相似文献   
82.
The main objective of this study was to configure the acquisition and analysis of low-field magnetic resonance imaging (MRI) to predict physico-chemical characteristics of Iberian loin, evaluating the use of different MRI sequences (spin echo, SE; gradient echo, GE; turbo 3D, T3D), computational texture feature methods (GLCM, NGLDM, GLRLM, GLCM + NGLDM + GLRLM), and data mining techniques (multiple linear regression, MLR; isotonic regression, IR). Moderate to very good correlation coefficients and low mean absolute error were found when applying MLR or IR on any method of computational texture features from MRI acquired with SE or GE. For T3D sequence, accurate results are only obtained by applying IR on GLCM or GLCM + NGLDM + GLRLM methods. Considering not only the accuracy of the methodology but also consumed time and required resources, the use of SE sequences for MRI acquisition, GLCM method for MRI texture analysis, and MLR could be indicated for prediction physico-chemical characteristics of loin.  相似文献   
83.
Several quality parameters of smoked, oven‐dried and sun‐dried paprikas were studied. Smoked paprikas showed the highest American Spice Trade Association (ASTA) units and pigment concentrations, whereas oven‐dried paprikas showed the best browning index and red/yellow pigment ratio, and sun‐dried paprikas had the highest redness for reflected colour. The colour stability results showed drastic overall colour change (ΔE) and decreased redness and ASTA units of the sun‐dried and oven‐dried paprikas after two and 5 days of UV exposure. Degradation of the smoked paprika colour parameters was progressive, and they showed less degradation even after 30 days. The evaluation of the antioxidant activity showed higher DPPH radical‐scavenging capacity in the smoked samples. The profiles of volatile phenolic compounds of the smoked samples are responsible for the differences in the antioxidant capacity. The great differences in colour stability and antioxidant activity make smoked paprika the best choice for use in the food industry.  相似文献   
84.
85.
Cerebellar ataxias (CA) comprise a heterogeneous group of neurodegenerative diseases characterized by a lack of motor coordination. They are caused by disturbances in the cerebellum and its associated circuitries, so the major therapeutic goal is to correct cerebellar dysfunction. Neurotrophic factors enhance the survival and differentiation of selected types of neurons. Liver growth factor (LGF) is a hepatic mitogen that shows biological activity in neuroregenerative therapies. We investigate the potential therapeutic activity of LGF in the 3-acetylpiridine (3-AP) rat model of CA. This model of CA consists in the lesion of the inferior olive-induced by 3-AP (40 mg/kg). Ataxic rats were treated with 5 µg/rat LGF or vehicle during 3 weeks, analyzing: (a) motor coordination by using the rota-rod test; and (b) the immunohistochemical and biochemical evolution of several parameters related with the olivo-cerebellar function. Motor coordination improved in 3-AP-lesioned rats that received LGF treatment. LGF up-regulated NeuN and Bcl-2 protein levels in the brainstem, and increased calbindin expression and the number of neurons receiving calbindin-positive projections in the cerebellum. LGF also reduced extracellular glutamate and GABA concentrations and microglia activation in the cerebellum. In view of these results, we propose LGF as a potential therapeutic agent in cerebellar ataxias.  相似文献   
86.
The simultaneous consumption of different classes of phytochemical antioxidants in the diet can result in more beneficial effects than when consumed alone. In the present study, the in vitro and in vivo antioxidative effects of espresso coffee brew (EC) (rich in chlorogenic acids) with added crude hazelnut skin phenolic extract (HSPE) from hazelnut skin waste (rich in flavonoids) were studied. Both post-brewing and pre-brewing phenolic-enriched espresso coffees (PE-ECs) were analysed for total phenols and screened for their in vitro antiradical ability. Moreover, the in vivo biological effect on the antioxidant potential of plasma in rats was evaluated. The PE-ECs showed increased both in vitro and in vivo antiradical activity proportional to the added HSPE. The in vivo experiments suggested that HSPE was much more antioxidant active than the phenolic fraction naturally contained in EC. Moreover, evidence of possible synergic effects of EC and HSPE phenolics was observed in vivo.  相似文献   
87.
88.
This paper models the relationship between vehicle miles traveled (VMT) on local and collector roads with an objective to predict local road VMT by using collector road VMT. Through a continuous approximation method typically used for vehicle routing, it first analytically reveals this relationship mainly as a function of roadway density ratios between multiple roadway classifications. This structural relationship suggests regression equations using density ratios or logarithmic values of them as the explanatory variables. The use of regression equations enables to account for varying spatial distributions of roadways and demand through parameter calibration. The proposed regression equations are proved good fits through computer simulation using distinct community road network topologies. In addition, practical data from Hennepin County of Minnesota, U.S.A. that encompasses Minneapolis indicates that our developed regression equations can work well.  相似文献   
89.
Due to the imaging devices, real-world images such as biological images may have poor contrast and be corrupted by noise, so that regions in the images present soft edges and their segmentation turns out to be quite difficult. Fuzzy mathematical morphology can be successfully applied to segment biological images having such characteristics of vagueness and imprecision. In this work we introduce an approach based on fuzzy mathematical morphology to segment images of human oocytes in order to extract the oocyte region from the entire image. The approach applies fuzzy morphological operators to detect soft edges in the oocyte images, followed by morphological reconstruction operators to isolate the oocyte region. The main concepts from fuzzy mathematical morphology are briefly introduced and the results of applying fuzzy morphological operators are reported in low-contrast images of human oocytes.  相似文献   
90.
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