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   3299篇
  免费   266篇
  国内免费   3篇
电工技术   16篇
综合类   2篇
化学工业   1234篇
金属工艺   26篇
机械仪表   84篇
建筑科学   111篇
矿业工程   2篇
能源动力   88篇
轻工业   1013篇
水利工程   14篇
石油天然气   15篇
无线电   105篇
一般工业技术   398篇
冶金工业   107篇
原子能技术   4篇
自动化技术   349篇
  2024年   10篇
  2023年   50篇
  2022年   234篇
  2021年   255篇
  2020年   122篇
  2019年   125篇
  2018年   136篇
  2017年   147篇
  2016年   134篇
  2015年   109篇
  2014年   179篇
  2013年   271篇
  2012年   255篇
  2011年   251篇
  2010年   157篇
  2009年   172篇
  2008年   164篇
  2007年   165篇
  2006年   97篇
  2005年   96篇
  2004年   73篇
  2003年   59篇
  2002年   46篇
  2001年   32篇
  2000年   29篇
  1999年   20篇
  1998年   40篇
  1997年   31篇
  1996年   24篇
  1995年   17篇
  1994年   7篇
  1993年   7篇
  1992年   3篇
  1991年   10篇
  1990年   2篇
  1989年   5篇
  1988年   3篇
  1987年   3篇
  1985年   3篇
  1984年   5篇
  1983年   5篇
  1982年   3篇
  1981年   2篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1976年   4篇
  1975年   1篇
  1972年   1篇
  1969年   1篇
排序方式: 共有3568条查询结果,搜索用时 0 毫秒
161.
Cristina Megías 《LWT》2009,42(1):228-926
The purification of a peptidic fraction with angiotensin converting enzyme (ACE) inhibitory activity from sunflower protein hydrolysates by affinity chromatography was recently described. We now describe that reverse-phase HPLC fractionation of this product yields several fractions with IC50 one order of magnitude higher than those previously purified by reverse-phase HPLC following gel filtration chromatography, showing that affinity chromatography is much more effective than gel filtration chromatography as a first step for purification of ACE inhibitory peptides. The amino acid composition of these fractions is presented, but attempts to determine their amino acid sequence failed, showing that these fractions contained more than one peptide.  相似文献   
162.
正由AN.ONYMOUS团队设计的IN.DENT牙科诊所,不仅在149 m2的空间实现了丰富职能,更将建筑作为人身体的延伸,成为一处让人反思的空间设计实验场。作为空间规划的依据,三角形吊顶系统明确地划定出这个医疗空间所容纳的复杂职能:T形走廊串联了诊所的公共接待区、无菌治疗室、手术室和医护办公区,走廊两侧治疗室的空间围合成梯形,相较于传统的矩形平面,它可以为诊所分隔出更  相似文献   
163.
Previously optimised postharvest treatments were compared to conventional chlorinated water treatment in terms of their effects on the overall quality of tomato (‘Zinac’) during storage at 10 °C. The treatments in question were water heat treatment (WHT?=?40 °C, 30 min), ultrasounds (US?=?45 kHz, 80 %, 30 min), thermosonication (TS?=?40 °C, 30 min, 45 kHz, 80 %) and ultraviolet irradiation (UV-C: 0.97 kJ m?2). The quality factors evaluated were colour, texture, sensorial analysis, mass loss, antioxidant capacity, total phenolic content, peroxidase and pectin methylesterase enzymatic activities, and microbial load reduction. The results demonstrate that all treatments tested preserve tomato quality to some extent during storage at 10 °C. WHT, TS and UV-C proved to be more efficient on minimising colour and texture changes with the additional advantage of microbial load reduction, leading to a shelf life extension when compared to control trials. However, at the end of storage, with exception of WHT samples, the antioxidant activity and phenolic content of treated samples was lower than for control samples. Moreover, sensorial results were well correlated with instrumental colour experimental data. This study presents alternative postharvest technologies that improve tomato (Zinac) quality during shelf life period and minimise the negative impact of conventional chlorinated water on human safety, health and environment.  相似文献   
164.
165.
Grape seed extracts (GSEs) were investigated in yeast cells harbouring defects in their antioxidant system (regarding the cellular growth and growth recovery from H2O2 insult). GSEs antioxidant activity was detected in wild-type and mutant strains Δcta1, Δgsh1 and Δoye2glr1, while pro-oxidant activity in Δsod1 cells was seen. Assessment of proliferation of prostate cancer PC3 and HBV-replicating HepG2 2.2.15 cells treated with GSEs has shown higher cytotoxicity of red grape seed extract (RW) than white grape seed extract (WW) subjective to dose and period of administration. No antiviral effect was detected by measuring the secreted virion particles in HepG2 2.2.15 cells treated with GSEs. The GSEs play a dual antioxidant/pro-oxidant role in vivo according with the cellular antioxidant system deficiencies and exhibit cytotoxic properties in PC3 and HepG2 2.2.15 cell lines, but no antiviral action against HBV.  相似文献   
166.
167.
It is well known that the content of water does affect materials behaviour and may cause important damages to buildings, including structural deterioration. Thermography is a non-intrusive imaging technique that allows the inspection of different materials based on their surface temperatures. Within an appropriate thermal analysis, moisture and other structural damages can be detected. The present research work deals with multitemporal thermal analysis to detect moisture on buildings, as well as other alterations. Two different approaches are tested to determine the effectiveness on the moisture surveys, one simple based on image differences, and another more sophisticated based on principal components analysis (PCA). The results are tested at the front door of the Arenberg Castle (Leuven, Belgium). Some moisture maps are derived and used to determine the reliability of either the computation of image differences or the PCA to carry out semi-automatically moisture surveys on architectural façades. The latter method is proven to be superior when using thermal imagery acquired at different times.  相似文献   
168.
Four experiments investigated the influence of a sudden social request on the kinematics of a preplanned action. In Experiment 1, participants were requested to grasp an object and then locate it within a container (unperturbed trials). On 20% of trials, a human agent seated nearby the participant unexpectedly stretched out her arm and unfolded her hand as if to ask for the object (perturbed trials). In the remaining 3 experiments, similar procedures were adopted except that (a) the human was replaced by a robotic agent, (b) the gesture performed by the human agent did not imply a social request, and (c) the gaze of the human agent was not available. Only when the perturbation was characterized by a social request involving a human agent were there kinematic changes to the action directed toward the target. Conversely, no effects on kinematics were evident when the perturbation was caused by the robotic agent or by a human agent performing a nonsocial gesture. These findings are discussed in the light of current theories proposed to explain the effects of social context on the control of action. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
169.
The purpose of this study was to investigate the impact of low fat diets in children aged 2 to 5. Eighty two children (40 females and 42 males) attending a school cafeteria (Province of Buenos Aires, Argentina), in a cross sectional study, were evaluated. Body weight (W), height (H) and body composition (BC) by bioimpedance were recorded. The anthropometric raw data were processed as Z-score of the weight-for-age (WEZ) and of the height-for-age (HAZ). Serum insulin-like growth factor 1 (IGF-1) and Zinc/haemoglobin ratio (Zn/Hb) were also measured. Results showed that 73.2% of the children were adequate (A) according WEZ, 13.4% were lean (L) and 13.4% overweight (O). 8.5% presented simultaneously impairment in WEZ and HAZ. Body fat percentage and energy metabolism were higher in O than in L and A (p < 0.05). Serum IGF-1's children--aged 4 to 5 years--with HAZ deficit were low than adequate HAZ ones. No statistical differences in Zn/Hb ratio between A, L and O were found. This cross sectional study suggests metabolic disorders in young children attending school cafeterias. These conclusions will allow to design balanced diets in order to optimize the resources, promote optimal growth and development and prevent adult diseases through dietary practices in childhood.  相似文献   
170.
The nutritional quality of protein hydrolysates has been related in several reports to their di- and tripeptide contents. In the present work different hydrolytic conditions were tested using papain in order to prepare casein hydrolysates with a suitable peptide profile for being used in special diets. The hydrolysates were fractionated by size-exclusion HPLC and the rapid Correct Fraction Area method was used for quantifying the peptides. Among the five hydrolytic conditions studied, three of them gave rise to preparations having nutritionally similar peptide profiles. However, the use of the temperature of 37 degrees C and enzyme:substrate ratio (E:S) of 2% may probably be the most economical condition for industrial production.  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