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   3502篇
  免费   99篇
  国内免费   22篇
电工技术   42篇
综合类   6篇
化学工业   886篇
金属工艺   127篇
机械仪表   80篇
建筑科学   49篇
矿业工程   3篇
能源动力   301篇
轻工业   185篇
水利工程   22篇
石油天然气   7篇
无线电   341篇
一般工业技术   814篇
冶金工业   470篇
原子能技术   25篇
自动化技术   265篇
  2023年   38篇
  2022年   82篇
  2021年   110篇
  2020年   86篇
  2019年   86篇
  2018年   146篇
  2017年   77篇
  2016年   84篇
  2015年   79篇
  2014年   114篇
  2013年   219篇
  2012年   160篇
  2011年   198篇
  2010年   157篇
  2009年   144篇
  2008年   121篇
  2007年   117篇
  2006年   93篇
  2005年   78篇
  2004年   67篇
  2003年   81篇
  2002年   51篇
  2001年   47篇
  2000年   38篇
  1999年   68篇
  1998年   154篇
  1997年   99篇
  1996年   93篇
  1995年   50篇
  1994年   53篇
  1993年   53篇
  1992年   37篇
  1991年   40篇
  1990年   34篇
  1989年   34篇
  1988年   28篇
  1987年   41篇
  1986年   41篇
  1985年   28篇
  1984年   36篇
  1983年   41篇
  1982年   24篇
  1981年   20篇
  1980年   25篇
  1979年   32篇
  1978年   22篇
  1977年   16篇
  1976年   23篇
  1975年   9篇
  1973年   11篇
排序方式: 共有3623条查询结果,搜索用时 0 毫秒
81.
82.
83.
Structured lipids containing behenic and medium chain (MC) fatty acids were prepared from palm stearin using 1,3-specific lipase-catalyzed acidolysis. Incorporation of MC and behenic acids was affected by proportion of substrate, type of fatty acids, reaction time, addition of water and quantity of lipase. It was found that incorporation of caproic acid was less compared to other longer chain fatty acids. Caprylic, capric and behenic acids shared similar incorporation (up to 32 %), which increased with the amount of fatty acids added and the time of reaction. The incorporation of these acids increased with addition of 1 % moisture and the increasing amount of enzyme from 5 to 10 % at the beginning of the reaction. Incorporating behenic and MC fatty acids, reduced palmitic and oleic acids considerably from palm stearin, the extent being the same as those incorporated. However, the reduction of linoleic acid was marginal. The solid fats content of the modified palm stearin containing MC and behenic acids were reduced at all temperatures due to a reduction in higher molecular weight triglycerides and an increasing proportion of lower chain triglycerides. The modified products of palm stearin with added capric and behenic acids were similar to commercial bakery shortenings and those with added capric acid were like salad or cooking oils or butter in melting characteristics.  相似文献   
84.
Soy meal-based biodegradable blends were prepared by melt extrusion process. The effects of denaturants, i.e., urea and sodium sulfite and plasticizer (glycerol) and polyester type (polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate) on tensile strength and elongation at break were investigated using a Taguchi experimental design approach. The results showed that the sodium sulfite had little or no effect on final properties of the blends. Also, biodegradable polyester type had significant effect on the tensile strength and elongation at break of the blends prepared. The predicted values and experimental were found to be in tune with each other. The chemical structure and morphology of the optimum sample was probed by FT-IR spectroscopy and scanning electron microscopy (SEM). Also, the results provided an insight into how important the plasticization and destructurization of soy protein to obtain the blends with desired mechanical properties.  相似文献   
85.
Despite of substantial advancement, the effect of grain boundary (GB) complexions on high temperature creep deformation process has not been fully understood. In this paper, we have studied the high temperature bending creep deformation of copper bicrystal with various GB complexions under different loads using molecular dynamics simulation. It has been found that specimen with normal kite GB complexion have better creep resistance properties when subjected to comparatively lower applied load. In case of monolayer Zr segregation, a drastic decrease in creep strength as well as creep plasticity is observed due to inhibition of GB migration. On the other hand, deviation between creep properties for specimen with split-kite GB complexion and split-kite bilayer Zr segregation GB complexion is minimal. Enhanced creep plasticity is observed in case of split-kite bilayer Zr segregation GB complexion, which is due to formation of interpenetrating icosahedral clusters in the necking region. Fracture in specimen with monolayer Zr segregation GB complexion has occurred by means of slip phenomenon at lower deformation load whereas amorphization and necking is observed at higher deformation load. In case of specimen with bilayer Zr segregation GB complexion, it is found that fracture has occurred through amorphization and necking at all deformation loads due to higher GB thickness.  相似文献   
86.
Multimedia Tools and Applications - In the era of the smart classroom environment, students’ affective content analysis plays a vital role as it helps to foster the affective states that are...  相似文献   
87.
Aluminum was electrodeposited from two different ionic liquid electrolytes namely; 1-ethyl-3-methylimidazolicum chloride and AlCl3 (EMIC–AlCl3) and 1-butyl-3-methylimidazolium chloride (BMIC–AlCl3) at 90 ± 2 °C. Nodular morphology of aluminum was obtained at the copper substrate. To evaluate the reaction mechanism, chronoamperometric study was adopted. From the chronoamperometric analysis, it was observed that the reaction was controlled by instantaneous three-dimensional diffusion process. The diffusion coefficient (D) of Al2C7 was found to be 5.2–6.6 × 10−11 m2 s−1 and 2.2 × 10−11 m2 s−1 for EMIC–AlCl3 and BMIC–AlCl3 ionic liquid electrolytes, respectively. The nuclei density of electrodeposited aluminum on the copper was also confirmed by scanning electron microscope wherein uniformly distributed aluminum nodules were observed.  相似文献   
88.
Microsegregation of alloying elements is prone to hot cracking in the weldment of alloy C-276. The formation of topologically close packed phases P and µ is largely responsible for the hot cracking. The present study articulates the effect of laser shock peening (LSP) to improve the metallurgical and mechanical properties of the weld joint. The weld joint was fabricated by pulsed current gas tungsten arc welding (PCGTAW) using an ERNiCrMo-3 filler wire. LSP without coating was carried out on the cap surface of the weldment. Microstructural studies were carried out to compare the as-welded and laser-peened microstructure on the fusion zone. The results show that a fine equiaxed dendritic structure was observed in both conditions. EDS analysis was carried out to evaluate the microsegregation of alloying elements. EDS analysis indicates that there are no secondary intermetallic phases. X-ray diffraction analysis was carried out to evaluate the phase change and crystallite size in the as-welded and laser shock peened fusion zone. The result shows 48.99% reduction in crystallite size after LSP. Hardness and tensile strength results indicate there is a consequential increase in laser shock peened specimen compared with as-welded specimen.  相似文献   
89.
5-Aminosalicylic acid (5-ASA) is an aminosalicylate anti-inflammatory drug, which is also known as mesalazine or mesalamine. Currently employed in treating inflammatory bowel disease, ulcerative colitis, inflamed anus or rectum, and maintain remission in Crohn's disease. Evidence from the researchers highlighted its significant re-epithelization in allergic asthma, aphthous, and gastric ulcerative conditions. The objective of the study was to formulate the pluronic lecithin organogel (PLO) containing 5-ASA and evaluate its wound-healing ability in a full thickness excision wound rat model. The data obtained from in silico docking studies revealed 5-ASA is having an affinity towards the transforming growth factor-beta (TGF-β) specifically towards beta1. Among various formulations prepared (F1 to F8), F1, and F6 have shown a maximum in vitro drug release with optimum pH and viscosity. From MTT assay it was found that selected PLO formulations showed no toxicity and enhanced cell proliferation in HaCaT cell lines. In vivo wound-healing studies in albino Wistar rats has revealed that PLO accelerates wound closure and reepithelization to the statistically significant level on day 3 (p?相似文献   
90.
Fine bamboo strips (BSs) have been laid on polypropylene (PP) web, stacked, and compression molded to prepare unconsolidated light-weight (0.312 g/cm3) composites. Composite properties are superior compared with jute-based composites and bamboo strips show potential to replace fiberglass or polyurethane in composites. Flexural strength, modulus, offset yield load, and Noise Reduction Coefficient (NR) of the BS–PP composites are 5.8×, 2.9×, 6.5×, and 1.4× higher, respectively, compared to jute–PP composites. Bamboo-based non-consolidated composites with excellent mechanical and sound absorption properties utilizing the methods described in this research provide an opportunity to manufacture functional composites with bio-based materials leading to reduction of environmental pollution and sustainable manufacturing.  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