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   1734篇
  免费   29篇
  国内免费   3篇
电工技术   80篇
综合类   3篇
化学工业   338篇
金属工艺   36篇
机械仪表   29篇
建筑科学   22篇
能源动力   73篇
轻工业   145篇
水利工程   2篇
无线电   155篇
一般工业技术   295篇
冶金工业   381篇
原子能技术   64篇
自动化技术   143篇
  2022年   14篇
  2021年   14篇
  2020年   8篇
  2019年   8篇
  2018年   16篇
  2017年   13篇
  2016年   14篇
  2015年   12篇
  2014年   27篇
  2013年   73篇
  2012年   56篇
  2011年   79篇
  2010年   55篇
  2009年   56篇
  2008年   52篇
  2007年   65篇
  2006年   58篇
  2005年   58篇
  2004年   51篇
  2003年   58篇
  2002年   54篇
  2001年   48篇
  2000年   35篇
  1999年   29篇
  1998年   148篇
  1997年   86篇
  1996年   80篇
  1995年   48篇
  1994年   42篇
  1993年   55篇
  1992年   28篇
  1991年   24篇
  1990年   22篇
  1989年   21篇
  1988年   22篇
  1987年   14篇
  1986年   20篇
  1985年   24篇
  1984年   17篇
  1983年   19篇
  1982年   22篇
  1981年   22篇
  1980年   11篇
  1979年   11篇
  1978年   15篇
  1977年   19篇
  1976年   16篇
  1974年   5篇
  1973年   4篇
  1967年   3篇
排序方式: 共有1766条查询结果,搜索用时 15 毫秒
991.
In this paper an efficient technique using magnetic field is proposed for wearable handwriting input. This device requires mounting a permanent magnet onto fingertip and detecting the magnetic field generated by the magnet through magnetic sensors at the wrist of the other hand. The position of magnet is calculated by the vector of the magnetic field. And a method is proposed to avoid geomagnetic influence, using two magnetic sensors. Numerical methods are used to calculate the position of magnet with geomagnetism cancellation. Two numerical methods have been adopted and compared. A prototype device is made and we succeeded to get the trajectory of handwriting input character.  相似文献   
992.
The objectives of this study were to determine the factors that cause differences in the improvements of gel strength and ε(γ-glutamyl)lysine (G-L) content in chicken and beef (Japanese black cattle) myofibrillar proteins after adding microbial transglutaminase (MTG). As the amount of MTG added increased, the breaking strength increased progressively (p < 0.01) in chicken and beef samples, with the exception of chicken samples treated at 40 °C. The values of elasticity in the chicken samples were lower than those of the beef samples (p < 0.01). Surprisingly, the elasticity level, ε(γ-glutamyl)lysine contents and myosin heavy chain (MHC) band sizes of chicken and beef at all levels of MTG were significantly different (p < 0.01). The results of this study suggest that MTG activity was affected by MTG inhibitors; that MTG develops the texture of myofibrils differently in different species. However, the activity is limited and inconstant among meat proteins, as suggested by the data collected from the chicken samples. As a result, when the transferable amino acid residues are depleted (cross-linked) by MTG activity, the function of MTG will be insignificant. The correlation between MTG and different sources of meat protein is quite unstable but it is strong, which was observed when chicken and beef responded differently to MTG because their chemical and physiological properties were different. The remarkable rate of formation of cross-linked proteins and the discrepancy between the expected and observed amount of dipeptide raises the possibility that there are enzymes capable of reversing the reaction induced by transglutaminase in chicken and beef myofibrils. In summary, our results suggest that access of MTG to chicken and beef myofibrils is different because it depends on physiological (muscles and their fibre types), biological (substrates) and biochemical (inhibitors and amino acids) variables.  相似文献   
993.
The antioxidative properties of a hot water extract of the leaves of Mallotus japonicus were evaluated. The extract had a high phenolic content and strong antioxidative activity, compared with green tea, rooibos tea, and red wine. Six phenolic compounds were isolated as antioxidative components by HPLC. They were identified as mallotinic acid, mallotusinic acid, corilagin, geraniin, rutin, and ellagic acid. These antioxidative compounds were subjected to DPPH radical-scavenging, superoxide radical-scavenging, and hydroxyl radical-scavenging assays, and compared with other antioxidative compounds. Four of the compounds, mallotinic acid, mallotusinic acid, corilagin and geraniin, exhibited much stronger antioxidative activity than gallic acid, rutin, ellagic acid, quercetin, and chlorogenic acid, and were as active as epigallocatechin gallate (EGCG), a strong antioxidant in green tea. Mallotus japonicus leaves are an excellent source of strong natural antioxidative materials.  相似文献   
994.
T. Ohta  F. Okada  M. Hayashi  M. Mihoichi 《Polymer》1989,30(12):2170-2173
A new method using gel-like spherulites will be presented for obtaining high-performance materials of ultra-high-molecular-weight polyethylene (UHMW-PE), which is available for the production of high-strength and high-modulus materials having a large cross-sectional area, for example, rods and thicker tapes. Such high-performance organic materials were not known until the development of this method in 1983. Ultra-drawability and characteristics of UHMW-PE produced by this method are discussed, based on the fine structure of gel press sheet.  相似文献   
995.
A new transverse mode controlled buried-multiquantum-well (BMQW) laser has been fabricated using the simple and reliable Zn-diffusion-induced disordering process. BMQW lasers are characterized by low threshold current (20 mA) and single transverse and longitudinal mode oscillation. It is observed that the threshold current is proportional to the stripe width and the transverse mode is controlled by controlling the stripe width. From these results, it is confirmed that the BMQW structure provides good optical confinement as well as current confinement.  相似文献   
996.
This paper proposes an economic model for the selection of time‐varying control chart parameters for monitoring on‐line the mean and variance of a normally distributed quality characteristic. The process is subject to two independent assignable causes. One cause changes the process mean and the other changes the process variance. The occurrence times of these assignable causes are described by Weibull distributions having increasing failure rates. The paper combines two existing models: (I) the model of Ohta and Rahim (IIE Transactions 1997; 29 :481–486) for a dynamic economic design of $\overline{X}$\nopagenumbers\end control charts, where a single assignable cause occurs according to a Weibull distribution and all design parameters are time varying; (II) the model of Costa and Rahim (QRE International 2000; 16 :143–156) for the joint economic design of $\overline{X}$\nopagenumbers\end and R control charts where two assignable causes occur independently according to Weibull distribution, with variable sampling intervals. The advantages of the proposed model over traditional $\overline{X}$\nopagenumbers\end and R control charts with fixed parameters are presented. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
997.
The bacteriostatic and bactericidal actions of vinegar on food-borne pathogenic bacteria including enterohemorrhagic E. coli (EHEC) O157:H7 were examined. The growth of all strains evaluated was inhibited with a 0.1% concentration of acetic acid in the vinegar. This inhibition was generally increased in the presence of sodium chloride or glucose. There was almost no difference in sensitivity to the bacteriostatic action of vinegar among the strains of pathogenic E. coli. Vinegar had a bactericidal effect on food-borne pathogenic bacteria including EHEC O157:H7. This action against EHEC O157:H7 was synergically enhanced by sodium chloride but was attenuated with glucose. For EHEC strains (O157:H7, O26:H11, O111:HNM) the difference in the inactivation rate due to vinegar among strains used was small, although an enteropathogenic E. coli (EPEC) O111:K58:H- strain was more sensitive, being more quickly killed compared with EHEC strains. The inactivation rate due to vinegar was constant irrespective of inoculum size. However, it differed greatly depending on growth phase of the cells, where logarithmic growth phase cells were more sensitive and easily killed than stationary phase cells. The bactericidal activity of vinegar increased with the temperature. Various conditions for bactericidal effects on EHEC O157:H7 were examined by the multiparametric analysis of five factors: acetic acid concentration in the vinegar, sodium chloride concentration, temperature, incubation time, and viable cell number. The combined use of vinegar and sodium chloride, with use of an appropriate treatment temperature, was found to be markedly effective for the prevention of bacterial food poisoning.  相似文献   
998.
999.
This work extends a recent observation that Otsuka Long-Evans Tokushima Fatty (OLETF) rats, which have been established as an animal model of non-insulin-dependent diabetes mellitus, show no expression of the cholecystokinin (CCK)-A receptor gene in the pancreas. The CCK-A receptor is known to be involved in regulating pancreatic exocrine function and growth. We examined the growth of the pancreas in terms of wet weight, enzyme compositions, and protein and DNA contents at 5-6 and 24-25 weeks of age in OLETF rats and control (Long-Evans Tokushima; LETO) rats. The pancreatic wet weight increased significantly with age in both OLETF and LETO rats but was significantly lower in OLETF rats than in LETO rats. The total DNA contents in the whole pancreas (cell numbers) were comparable for both strains and increased significantly with age. However, the ratio of protein content to DNA content (the cell size) significantly increased with age in LETO rats, with no increase in OLETF rats. The changes in chymotrypsin, amylase, and insulin with respect to age were in the same direction in both strains: a decrease or no change in total and/or cellular contents of chymotrypsin and insulin and increases in amylase. These results suggest that the CCK-A receptor plays some role in the increase in cell size associated with normal growth of the pancreas from 5 to 25 weeks of age (after weaning).  相似文献   
1000.
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