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   213篇
  免费   19篇
电工技术   1篇
综合类   2篇
化学工业   72篇
机械仪表   7篇
建筑科学   10篇
能源动力   3篇
轻工业   56篇
水利工程   1篇
石油天然气   1篇
无线电   7篇
一般工业技术   37篇
冶金工业   6篇
自动化技术   29篇
  2024年   1篇
  2023年   3篇
  2022年   21篇
  2021年   20篇
  2020年   8篇
  2019年   6篇
  2018年   10篇
  2017年   7篇
  2016年   11篇
  2015年   11篇
  2014年   11篇
  2013年   28篇
  2012年   26篇
  2011年   14篇
  2010年   15篇
  2009年   15篇
  2008年   2篇
  2007年   3篇
  2006年   7篇
  2005年   4篇
  2003年   2篇
  2002年   2篇
  2000年   1篇
  1997年   1篇
  1995年   1篇
  1982年   1篇
  1978年   1篇
排序方式: 共有232条查询结果,搜索用时 46 毫秒
31.
The periodic assessment of claddings adhesion during the facade life cycle becomes an important preventive in-service issue. This paper discusses the pull-off test, an in-situ diagnosis technique, which characterizes the in-service performance of ceramic tile claddings, by measuring adherence resistance to tension. Adherence is one of the main required properties of external coating, not only for aesthetical reasons but also for safety purposes. Throughout this research, an experimental campaign is performed in laboratory and in-situ, analyzing the variability of the pull-off testing technique. In-situ tests have been undertaken in existing construction sites and test walls. The laboratory results were compared to the in-situ ones. Standards requirements were evaluated and different failure modes were verified. In this work the impact of several parameters is analyzed such as the use of metallic discs with different thickness levels, geometries, and dimensions; the location of the testing at different heights; and the use of different dynamometer equipment. The main conclusion of this work is in order to reduce the uncertainty of the in-service diagnosis used for decision process of facade interventions, the previous parameters should be taking into account despite pull-off being a standardized technique.  相似文献   
32.
An automatic method is established for layer‐by‐layer (LbL) assembly of biomimetic coatings in cell culture microplates using a commercial liquid‐handling robot. Highly homogeneous thin films are formed at the bottom of each microwell. The LbL film‐coated microplates are compatible with common cellular assays, using microplate readers and automated microscopes. Cellular adhesion is screened on crosslinked and peptide‐functionalized LbL films and stem cell differentiation in response to increasing doses of bone morphogenetic proteins (2, 4, 7, 9). This method paves the way for future applications of LbL films in cell‐based assays for regenerative medicine and high‐throughput drug screening.  相似文献   
33.
Water Resources Management - The behavior of a rainwater harvesting system depends on some variables that cannot be controlled, such as rainfall, building roof size and water consumption. The...  相似文献   
34.
In this paper, we present our efforts in modeling and simulation of polyethylene glycol crosslinked with an isocyanate tHDI. The polymer, by its nature, is hydrophilic and has strong hydrogen bond interactions with water. The simulations are performed at coarse-grained scale by using a dissipative particle dynamics (DPD) simulation method. The effect of hydrogen bond between water and polymer beads on the structure of the crosslinked hydrophilic polymer structure is studied. The polymer is observed to phase separate with water in the absence of hydrogen bonds in DPD simulations. In the reverse case, where hydrogen bonds are explicitly included in DPD simulations, polymer mixes with water. This behavior is investigated by plotting the density profiles. Moreover, the volumetric swelling behavior in mixtures with different water contents is estimated from simulations and extrapolated by a polynomial fit to compare with experiments. It is observed that the predicted swelling ratio is in good agreement with the experimental measurements.  相似文献   
35.
RASGRP2 encodes the calcium and diacylglycerol (DAG)-regulated guanine nucleotide exchange factor I (CalDAG-GEFI) identified as a Rap1-activating molecule. Pathogenic variants previously identified in RASGRP2 allowed the characterization of CalDAG-GEFI deficiency as a non-syndromic, autosomal recessive platelet function disease. We report on the clinical manifestations and laboratory features of a Portuguese family with a likely pathogenic variant in RASGRP2 (c.999G>C leading to a p.Lys333Asn change in the CDC25 catalytic domain of CalDAG-GEFI) and discuss the contribution of this variant to the disease manifestations. Based on the study of this family with one homozygous patient and five heterozygous carriers and on a critical analysis of the literature, we challenge previous knowledge that CalDAG-GEFI deficiency only manifests in homozygous patients. Our data suggest that at least for the RASGRP2 variant reported herein, there is a phenotypic expression, albeit milder, in heterozygous carriers.  相似文献   
36.
Chronic Myeloid Leukemia (CML) is a rare malignant proliferative disease of the hematopoietic system, whose molecular hallmark is the Philadelphia chromosome (Ph). The Ph chromosome originates an aberrant fusion gene with abnormal kinase activity, leading to the buildup of reactive oxygen species and genetic instability of relevance in disease progression. Several genetic abnormalities have been correlated with CML in the blast phase, including chromosomal aberrations and common altered genes. Some of these genes are involved in the regulation of cell apoptosis and proliferation, such as the epidermal growth factor receptor (EGFR), tumor protein p53 (TP53), or Schmidt-Ruppin A-2 proto-oncogene (SRC); cell adhesion, e.g., catenin beta 1 (CTNNB1); or genes associated to TGF-β, such as SKI like proto-oncogene (SKIL), transforming growth factor beta 1 (TGFB1) or transforming growth factor beta 2 (TGFB2); and TNF-α pathways, such as Tumor necrosis factor (TNFA) or Nuclear factor kappa B subunit 1 (NFKB1). The involvement of miRNAs in CML is also gaining momentum, where dysregulation of some critical miRNAs, such as miRNA-451 and miRNA-21, which have been associated to the molecular modulation of pathogenesis, progression of disease states, and response to therapeutics. In this review, the most relevant genomic alterations found in CML will be addressed.  相似文献   
37.
The development of low-cost, accurate, and equipment-free diagnostic tests is crucial to many clinical, laboratory, and field applications, including forensics and medical diagnostics. Cellulose fiber-based paper is an inexpensive, biodegradable, and renewable resource, the use of which as a biomolecule detection matrix and support confers several advantages compared to traditional materials such as glass. In this context, a new, facile method for the preparation of surface functionalized papers bearing single-stranded probe DNA (ssDNA) for rapid target hybridization via capillary transport is presented. Optimized reaction conditions were developed that allowed the direct, one-step activation of standard laboratory filters by the inexpensive and readily available bifunctional linking reagent, 1,4-phenylenediisothiocyanate. Such papers were thus amenable to subsequent coupling of amine-labeled ssDNA under standard conditions widely used for glass-based supports. The intrinsic wicking ability of the paper matrix facilitated rapid sample elution through arrays of probe DNA, leading to significant, detectable hybridization in the time required for the sample liquid to transit the vertical length of the strip (less than 2 min). The broad applicability of these paper test strips as rapid and specific diagnostics in "real-life" situations was exemplified by the discrimination of amplicons generated from canine and human mitochondrial and genomic DNA in mock forensic samples.  相似文献   
38.
Cows' and donkey milks (raw and thermally processed) and respective whey were analysed for quantification of major proteins. Two different chromatographic approaches, size exclusion (SE-HPLC) and reversed-phase high performance liquid chromatography (RP-HPLC) both coupled to UV detection were used. Usefulness of these methods for routine control of the effect of thermal processing was evaluated. The external standard method was used to calibrate the SE-HPLC and RP-HPLC systems. Concerning quantification of β-lactoglobulin (β-lg), α-lactalbumin (α-la), lysozyme (lys), and total casein (cn), no significant differences between results obtained by SE-HPLC and by RP-HPLC (t-test, P>0·05) were observed for raw milks and whey. Heating of cows' milk promoted aggregation of denatured proteins as observed by SE-HPLC, whereas α-la and β-lg from donkey milk were stable to thermal processing at 100 °C (5 min). Lys was quantified in donkey raw milk and whey however, in thermally processed donkey milk lys was denatured and could not be quantified by HPLC.  相似文献   
39.
A headspace solid-phase microextraction gas chromatography (GC)-mass spectrometry (MS) method previously optimized for analyses of volatiles in coffee was used for simultaneous quantification of major furanic compounds (2-furfural, furfuryl alcohol, 5-methylfurfural and furfuryl acetate) and furan, in espresso coffee prepared from hermetically closed capsules. High sensitivity was achieved with low limits of detection and limits of quantification. Good linearity was observed with correlation coefficients higher than 0.999. Recovery percentages were 102 % for furan, 99.7 % for 2-furfural, 98.0 % for furfuryl alcohol, 99.8 % for 5-methylfurfural and 99.9 % for furfuryl acetate. The method was applied to the analyses of espresso coffee from hermetically closed capsules. A total of 69 volatiles for Blend Roast and Blend Dark Roast samples, 64 volatiles for Arabica Dark Roast samples, 91 volatiles for Arabica Light Roast samples, 96 volatiles for Caramel coffee, 90 volatiles for Vanilla coffee and 92 volatiles for Almond coffee. In general, furanic compounds were the major chemical family, ketones, aldehydes, acids, pyrazines, pyrroles, alcohols, pyridines, aromatic compounds, hydrocarbons, and ethers were also detected. Total content of these furanic compounds varied from 105 to 199 μg ml?1. The optimized method proved to be a reliable methodology for quantification of major furanic compounds and furan present in different types of espresso coffee. Although relative percentage of peak area is a good method for discriminate volatiles in different coffee brews with closer composition, the quantification of furanic compounds is more accurate for understand the real intake amount.  相似文献   
40.
Background: Dietary patterns are often considered as one of the main causes of non-communicable diseases worldwide. It is of utmost importance to study dietary habits in developing countries since this work is scarce.

Objective: To summarize the most recent research conducted in this field in African countries, namely the most used methodologies and tools.

Methods: A systematic review was conducted on MEDLINE®/PubMed, aiming to identify scientific publications focused on studies of dietary intake of different African populations, in a ten-year period. Papers not written in English/Portuguese/Spanish, studies developed among African people but not developed in African countries, studies aiming to assess a particular nutrient/specific food/food toxin and studies that assessed dietary intake among children were excluded.

Findings: Out of 99 included studies, the 24-hour recall and the food-frequency questionnaire were the most used dietary intake assessment tools, used to assess diet at an individual level. It was also observed that often country-unspecific food composition databases are used, and the methodologies employed are poorly validated and standardized.

Conclusions: There is an emergent need to improve the existing food databases by updating food data and to develop suitable country-specific databases for those that do not have their own food composition table.  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