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   3360篇
  免费   144篇
电工技术   26篇
综合类   1篇
化学工业   677篇
金属工艺   31篇
机械仪表   27篇
建筑科学   168篇
矿业工程   4篇
能源动力   48篇
轻工业   502篇
水利工程   42篇
石油天然气   12篇
无线电   126篇
一般工业技术   408篇
冶金工业   1120篇
原子能技术   7篇
自动化技术   305篇
  2023年   23篇
  2022年   66篇
  2021年   112篇
  2020年   57篇
  2019年   68篇
  2018年   87篇
  2017年   72篇
  2016年   97篇
  2015年   53篇
  2014年   95篇
  2013年   205篇
  2012年   158篇
  2011年   219篇
  2010年   166篇
  2009年   166篇
  2008年   173篇
  2007年   175篇
  2006年   147篇
  2005年   140篇
  2004年   92篇
  2003年   89篇
  2002年   98篇
  2001年   65篇
  2000年   59篇
  1999年   64篇
  1998年   48篇
  1997年   41篇
  1996年   58篇
  1995年   44篇
  1994年   49篇
  1993年   46篇
  1992年   40篇
  1991年   16篇
  1990年   35篇
  1989年   37篇
  1988年   36篇
  1987年   24篇
  1986年   28篇
  1985年   27篇
  1984年   25篇
  1983年   20篇
  1982年   19篇
  1981年   22篇
  1980年   12篇
  1979年   17篇
  1978年   16篇
  1976年   9篇
  1975年   14篇
  1974年   10篇
  1969年   8篇
排序方式: 共有3504条查询结果,搜索用时 15 毫秒
101.
This paper presents the continued development of a novel non-destructive testing method termed tube-jack testing. The goal of the tube-jack system is to provide an enhanced and less destructive method than traditional flat-jack testing for determination of mechanical characteristics and local stress states in irregular masonry walls. Single tube-jack tests were performed, using previously developed rubber tube-jacks, in regular masonry walls of granite and cement-lime mortar. A traditional flat-jack test was also performed in the same masonry wall. Conclusions suggest that tube-jacks are successful in applying pressure to the masonry at low stress states.  相似文献   
102.
103.
104.
Spices are parts of plants that due to their properties are used as colorants, preservatives, or medicine. The uses of spices have been known since long time, and the interest in the potential of spices is remarkable due to the chemical compounds contained in spices, such as phenylpropanoids, terpenes, flavonoids, and anthocyanins. Spices, such as cumin (cuminaldehyde), clove (eugenol), and cinnamon (cinnamaldehyde) among others, are known and studied for their antimicrobial and antioxidant properties due to their main chemical compounds. These spices have the potential to be used as preservatives in many foods namely in processed meat to replace chemical preservatives. Main chemical compounds in spices also confer other properties providing a variety of applications to spices, such as insecticidal, medicines, colorants, and natural flavoring. Spices provide beneficial effects, such as antioxidant activity levels that are comparable to regular chemical antioxidants used so they can be used as a natural alternative to synthetic preservatives. In this review, the main characteristics of spices will be described as well as their chemical properties, different applications of these spices, and the advantages and disadvantages of their use.  相似文献   
105.
Drug delivery via the buccal route has emerged as a promising alternative to oral drug delivery. Didanosine (DDI) undergoes rapid degradation in the gastrointestinal tract, has a short half-life and low oral bioavailability, making DDI a suitable candidate for buccal delivery. Recent developments in buccal drug delivery show an increased interest toward nano-enabled delivery systems. The advantages of buccal drug delivery can be combined with that of nanoparticulate delivery systems to provide a superior delivery system. The aim of this study was to design and evaluate the preparation of novel nano-enabled films for buccal delivery of DDI. Solid lipid nanoparticles (SLNs) were prepared via hot homogenization followed by ultrasonication and were characterized before being incorporated into nano-enabled monolayered multipolymeric films (MMFs). Glyceryl tripalmitate with Poloxamer 188 was identified as most suitable for the preparation of DDI-loaded SLNs. SLNs with desired particle size (PS) (201?nm), polydispersity index (PDI) (0.168) and zeta potential (?18.8?mV) were incorporated into MMFs and characterized. Conventional and nano-enabled MMFs were prepared via solvent casting/evaporation using Eudragit RS100 and hydroxypropyl methylcellulose. Drug release from the nano-enabled films was found to be faster (56% versus 20% in first hour). Conventional MMFs exhibited higher mucoadhesion and mechanical strength than nano-enabled MMFs. SLNs did not adversely affect the steady state flux (71.63?±?13.54?µg/cm2?h versus 74.39?±?15.95?µg/cm2?h) thereby confirming the potential transbuccal delivery of DDI using nano-enabled MMFs. Nano-enabled buccal films for delivery of DDI can be successfully prepared, and these physico-mechanical studies serve as a platform for future formulation optimization work in this emerging field.  相似文献   
106.
107.
Language requires both storage and composition. However, exactly what is retrieved from memory and what is assembled remains controversial, especially for inflected words. Here, “imageability effects” is introduced as a new diagnostic of storage and a complement to frequency effects. In 2 studies of past-tense morphology, more reliable imageability and frequency effects were found on irregulars than on regulars. An interaction with sex was also observed: Males but not females showed more reliable frequency and imageability effects for irregulars than for regulars; females but not males showed signs of storage for regulars, particularly among higher frequency forms. Overall, the findings validate imageability effects as another diagnostic of storage and suggest that the line between storage and computation is not a simple function; rather, it depends upon the interplay of both item- and subject-specific factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
108.
The production of a composite powder of eutectic B4C–TiB2 is demonstrated via an atmospheric plasma processing method. Feedstock material is prepared for plasma processing by mixing and spray drying monolithic B4C and TiB2 to produce a flowable precursor powder. These powders are fed through a plasma torch, where they are melted and actively quenched in flight with argon gas. Plasma processed powders are composed of crystalline B4C and TiB2, with some additional B2O3 oxide phase. The plasma processing method results in the production of monolithic B4C and TiB2 nanoparticles, but some larger particles (generally ≥10 μm in diameter) are shown to contain the traditional lamellar eutectic microstructure. The eutectic interphase spacing ranges from 100 to 650 nm, and the composite microstructure is present through the entire thickness of the eutectic particles. Future work on plasma processing of eutectic powders should focus on methods utilizing passive in‐flight quenching to increase the average particle size.  相似文献   
109.
110.
The composition of the borosilicate glass layer formed during oxidation of ZrB2‐30 vol% SiC was determined to elucidate the extent of B2O3 retention in the oxide during high‐temperature oxidation. Oxidation was conducted in stagnant air at 1300°C, 1400°C, and 1500°C for times between 100 and 221 min. Specimens were characterized using mass change and scanning electron microscopy. After oxidation, the borosilicate glass layer was dissolved from the specimens sequentially with deionized H2O and HF acid, to analyze the glass composition using inductively coupled plasma optical emission spectrometry. It was found that the average B2O3 content in the glass scale ranged from 23 to 47 mol%. Retained B2O3 content in the bulk of the glass decreased with increasing temperature, confirming increased volatility with temperature. Boron depth profiles were also obtained in the near surface region using X‐ray photoelectron spectroscopy and energy dispersive spectroscopy. The measured B concentrations were used to estimate the B2O3 concentration profile and B diffusion coefficients in the borosilicate glass. Implications for the ZrB2‐SiC oxidation process are discussed.  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