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   2351篇
  免费   180篇
  国内免费   4篇
电工技术   36篇
综合类   2篇
化学工业   515篇
金属工艺   50篇
机械仪表   87篇
建筑科学   117篇
矿业工程   3篇
能源动力   176篇
轻工业   413篇
水利工程   18篇
石油天然气   11篇
无线电   147篇
一般工业技术   462篇
冶金工业   104篇
原子能技术   13篇
自动化技术   381篇
  2024年   8篇
  2023年   25篇
  2022年   59篇
  2021年   104篇
  2020年   93篇
  2019年   104篇
  2018年   114篇
  2017年   98篇
  2016年   128篇
  2015年   81篇
  2014年   114篇
  2013年   225篇
  2012年   144篇
  2011年   193篇
  2010年   137篇
  2009年   161篇
  2008年   137篇
  2007年   119篇
  2006年   86篇
  2005年   66篇
  2004年   67篇
  2003年   44篇
  2002年   41篇
  2001年   13篇
  2000年   16篇
  1999年   24篇
  1998年   25篇
  1997年   15篇
  1996年   19篇
  1995年   9篇
  1994年   3篇
  1993年   3篇
  1992年   6篇
  1991年   10篇
  1990年   5篇
  1989年   5篇
  1988年   4篇
  1987年   7篇
  1986年   7篇
  1985年   6篇
  1984年   4篇
  1982年   1篇
  1981年   1篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有2535条查询结果,搜索用时 203 毫秒
71.
72.
The aim of this study was to integrate multi omics data to characterize underlying functional pathways and candidate genes for drip loss in pigs. The consideration of different omics levels allows elucidating the black box of phenotype expression. Metabolite and protein profiling was applied in Musculus longissimus dorsi samples of 97 Duroc × Pietrain pigs. In total, 126 and 35 annotated metabolites and proteins were quantified, respectively. In addition, all animals were genotyped with the porcine 60 k Illumina beadchip. An enrichment analysis resulted in 10 pathways, amongst others, sphingolipid metabolism and glycolysis/gluconeogenesis, with significant influence on drip loss. Drip loss and 22 metabolic components were analyzed as intermediate phenotypes within a genome-wide association study (GWAS). We detected significantly associated genetic markers and candidate genes for drip loss and for most of the metabolic components. On chromosome 18, a region with promising candidate genes was identified based on SNPs associated with drip loss, the protein “phosphoglycerate mutase 2” and the metabolite glycine. We hypothesize that association studies based on intermediate phenotypes are able to provide comprehensive insights in the genetic variation of genes directly involved in the metabolism of performance traits. In this way, the analyses contribute to identify reliable candidate genes.  相似文献   
73.
A new Schiff base, 4-((6-ethoxybenzothiazole-2-ylimino)methyl)benzene-1,2-diol (3,4-HBAEBT) was synthesized by the condensation reaction of 3,4-dihydroxybenzaldehyde (3,4-HBA) and 2-amino-6-ethoxybenzothiazole. The Schiff base, then, was converted to its polymer derivatives by oxidative polycondensation reaction in both organic (P-1) and aqueous alkaline medium (P-2). Spectral observations indicated different structural properties for each polymerization condition. Organic and aqueous alkaline medium produced poly(ether) and poly(phenol) structures, respectively. The obtained polymers were separately studied with respect to optical, electrochemical, electrical and thermal properties. With exception of thermal degradation behaviors, the other investigated properties as well as morphological characteristics of both polymers were considerably different. In the fluorescence measurements a solvatochromic effect was recorded and the emission colors of the polymers could be changed as turquoise-green by solvent change.  相似文献   
74.
New cationic surfactants were synthesized by the quaternization of a number of straight-chain amide derivatives with triethylamine or pyridine. The corrosion inhibition tests of the surface-active compounds were performed at room temperature for 24 h on carbon steel coupons in acidic media using the gravimetric method. The acidic media used were 1.5 M HCl and 1.5 M H2SO4. Almost all of the synthesized cationic surfactants showed efficient inhibition of corrosion in the test. To establish the inhibition efficiencies of the inhibitors, surface characterization studies (contact angle measurements, SEM analysis and optical profilometer images) of the metal coupons used were performed.  相似文献   
75.
The optimisation of the quantity of sourdough (A) prepared with two different fermentation methods, [spontaneous fermentation (F1) vs. starter of lactic acid bacteria‐added fermentation (F2)], instant active dry yeast (B) and wheat bran (C) for a nutritionally improved bread formulation has been studied by evaluating the bioavailability and bioactive properties. The bread produced according to the optimised formula and fermentation types of F1 (OBF1) and F2 (OBF2) was compared with control bread (CB). The optimised levels for F1 were 11.45% for sourdough, 1.10% for dry yeast and 1.58% for wheat bran and for F2 6.99% for sourdough, 1.02% for dry yeast and 38.84% for wheat bran. The addition of sourdough significantly (< 0.05) affected antioxidant activity, total phenolic content, in vitro ash and protein digestibility, and enzyme resistance starch contents of bread. The F1 fermentation method was found to be more effective in terms of bread properties examined.  相似文献   
76.
This paper presents a comparative study for the weakly compressible (WCSPH) and incompressible (ISPH) smoothed particle hydrodynamics methods by providing numerical solutions for fluid flows over an airfoil and a square obstacle. Improved WCSPH and ISPH techniques are used to solve these two bluff body flow problems. It is shown that both approaches can handle complex geometries using the multiple boundary tangents (MBT) method, and eliminate particle clustering‐induced instabilities with the implementation of a particle fracture repair procedure as well as the corrected SPH discretization scheme. WCSPH and ISPH simulation results are compared and validated with those of a finite element method (FEM). The quantitative comparisons of WCSPH, ISPH and FEM results in terms of Strouhal number for the square obstacle test case, and the pressure envelope, surface traction forces, and velocity gradients on the airfoil boundaries as well as the lift and drag values for the airfoil geometry indicate that the WCSPH method with the suggested implementation produces numerical results as accurate and reliable as those of the ISPH and FEM methods. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
77.
Trend Assessment by the Innovative-Şen Method   总被引:1,自引:0,他引:1  
Hydro-meteorological time series may include trend components mostly due to climate change since about three to four decades. Trend detection and identification in a better and refined manner are among the major current research topics in water resources domain. Even though different methodologies can be found for trend detection in literature, two well-known procedures are the Mann-Kendall (MK) trend test and recently innovative-?en trend method, which provides different aspects of the trend. The theoretical basis and application of these two methods are completely different. The MK test gives a holistic monotonic trend without any categorization of the time series into a set of clusters, but the innovative-?en method is based on cluster and provides categorical trend behavior in a given time series. The main purpose of this paper is to provide important differences between these two approaches and their possible similarities. The applications of the two approaches are given for hydro-meteorological records including relative humidity, temperature, precipitation and runoff from Ergene drainage basin in the north-western part of Turkey. It is observed that although MK trend test does not show significant trend almost in all the cases, the innovative-?en approach yields trend categorizations as “very low”, “low”, “medium” “high” and “very high”, which should be taken into consideration in future flood (“very high”) and drought (“very low”) studies.  相似文献   
78.
79.
Nowadays, so as to adapt to the global market, where competition is getting tougher, firms producing through the modern production approach need to bring not the only performance of the system designed both during the research and development phase and the production phase but also the performance of the product to be developed as well as the process to be improved to the highest level. The Taguchi method is an experimental design technique seeking to minimize the effect of uncontrollable factors, using orthogonal arrays. It can also be designed as a set of plans showing the way data are collected through experiments. Experiments are carried out using factors defined at different levels and a solution model generated in ARENA 3.0 program using SIMAN, which is a simulation language. Many experimental investigations reveal that the speed and capacity of automated-guided vehicle, the capacities of local depots, and the mean time between shipping from the main depot are the major influential parameters that affect the performance criteria of the storage system. For the evaluation of experiment results and effects of related factors, variance analysis and signal/noise ratio are used and the experiments are carried out in MINITAB15 according to Taguchi L16 scheme. The purpose of this study is to prove that experimental design is an utilizable method not only for product development and process improvement but it can also be used effectively in the design of material handling–transfer systems and performance optimization of automation technologies, which are to be integrated to the firms.  相似文献   
80.
To increase the mechanical properties of recycled carbon fiber-reinforced polypropylene (PP) composites, recycled carbon fibers (RCF) were subjected to atmospheric plasma treatment at different plasma powers (100, 200, and 300 W). The changes on surface topography and roughness of RCF were examined by atomic force microscopy. Plasma treatment of RCF increased the roughness value of RCF. The variation of surface elemental compositions and tensile strength of RCF were determined by using X-ray photoelectron spectroscopy and tensile test, respectively. Plasma-treated RCF-reinforced PP composites were fabricated using high speed thermo-kinetic mixer. Plasma treatment of RCF at 100 W increased the tensile and flexural strength values of RCF-reinforced PP composites considerably by 17 and 11%, respectively. However, plasma treatment of RCF at higher plasma powers (200 W and 300 W) decreased tensile and flexural strength values of composites because of the etching of RCF. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47131.  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