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   936篇
  免费   29篇
  国内免费   10篇
电工技术   70篇
综合类   4篇
化学工业   262篇
金属工艺   20篇
机械仪表   10篇
建筑科学   36篇
能源动力   21篇
轻工业   54篇
水利工程   1篇
石油天然气   2篇
无线电   61篇
一般工业技术   191篇
冶金工业   140篇
原子能技术   26篇
自动化技术   77篇
  2022年   9篇
  2021年   16篇
  2020年   4篇
  2019年   12篇
  2018年   15篇
  2017年   12篇
  2016年   14篇
  2015年   13篇
  2014年   20篇
  2013年   33篇
  2012年   30篇
  2011年   46篇
  2010年   31篇
  2009年   34篇
  2008年   45篇
  2007年   26篇
  2006年   42篇
  2005年   41篇
  2004年   30篇
  2003年   28篇
  2002年   24篇
  2001年   16篇
  2000年   15篇
  1999年   25篇
  1998年   58篇
  1997年   38篇
  1996年   35篇
  1995年   19篇
  1994年   23篇
  1993年   18篇
  1992年   10篇
  1991年   13篇
  1990年   15篇
  1989年   8篇
  1988年   13篇
  1987年   10篇
  1986年   20篇
  1985年   10篇
  1984年   9篇
  1983年   11篇
  1982年   12篇
  1981年   5篇
  1980年   12篇
  1979年   15篇
  1978年   7篇
  1977年   8篇
  1976年   5篇
  1975年   4篇
  1974年   4篇
  1972年   3篇
排序方式: 共有975条查询结果,搜索用时 15 毫秒
71.
1IntroductionHydrogelisapolymericmaterial(syntheticornaturaJ)whichswellswhenplacedincontactwithwaterbutisnotsolubleandhastheabililtytoretainwaterwithinitsstructare.InIecentyears,muchattentionhasbeenfocusedontheresearchanddevelopmentofthepolymerhydIogelsforbiomaterials,suchascontactlenses,wounddressing,enzymeimmunoassay,cathetersanddIugdeliverysystems[1~3].Adressingisoftencoveredonthewotmdtoaccelerateitshealing.TheIearetwokindsofdiessings:drytypeandwettype.Ithasbeenreportedthatheallngwithawe…  相似文献   
72.
73.
In expanding expressway networks in Japan, various types of structures have been constructed, e.g., long span bridges and bridges with high piers. The expressway structures are well designed for the external dynamic forces, e.g., earthquakes and strong winds. However, for further safety promotion of the expressway networks, it is important to evaluate the drivers’ responses under strong dynamic disturbances. The present authors have investigated the moving stability of a vehicle under seismic motion based on both numerical simulation and virtual experiments using a driving simulator. Strong crosswind is considered as another factor that makes it difficult for drivers to control their vehicles. This study investigates the moving stability of a vehicle under strong crosswind based on numerical analyses and driving simulator experiments. To predict the future position of a moving vehicle including the reaction of a driver, the second-order predictable correction model is used in the numerical analyses. The results obtained from the numerical and experimental studies are compared and the validity of the driver model is discussed. It is expected that this research is helpful for the decision-making of expressway closure under strong wind and the design of wind barriers.  相似文献   
74.
We evaluated the effects of nipradilol, a beta-adrenoreceptor antagonist which contains a nitroxy residue, for vascular response in atherosclerosis of rabbits. Four groups of rabbits received different diets (standard diet; standard diet plus 10 mg/kg/day nipradilol; atherogenic diet [standard diet plus 1% cholesterol]; atherogenic diet plus 10 mg/kg/day nipradilol) for 9 weeks. Plasma lipids, blood pressure, vascular function, nitric oxide (NO), activity of NO synthase, cGMP, and histological atherosclerotic changes were evaluated. Neither the atherogenic diet nor nipradilol treatment affected significantly the animals' body weight, blood pressure, or heart rate. The atherogenic diet increased total cholesterol and triglycerides, which were not altered by nipradilol. The atherogenic diet diminished the acetylcholine-induced NO mediated relaxation. Nipradilol treatment restored this relaxation. Analyses using a NO-sensitive selective electrode showed that nipradilol released NO in the presence of cells and that NO release was greater in atherosclerotic aorta with than without nipradilol treatment. Nipradilol treatment increased the basal NO release as evaluated by the aortic tissue cyclic GMP (cGMP) levels in atherosclerotic vessel, and reduced the esterified cholesterol levels in atherosclerotic vessel. Conclusively, NO released by nipradilol may protect endothelium derived relaxation in atherosclerotic vessels, and may partially inhibit the accumulation of cholesterol in the atherosclerotic lesions.  相似文献   
75.
We have attempted to synthesize the meixnerite (Mg–Al–OH) type layered double hydroxide (LDH) by a two step milling operation of a mixture of Mg(OH)2 and Al(OH)3 with water. In the first-step, a mixture of the starting materials was milled for 1 h without water, and the product prepared in the first-step was milled for 2 h with water in the second-step milling operation. The milled products were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermo gravimetric-differential thermal analyses with mass spectroscopy (TG-DTA/MS). The surface morphology was characterized by scanning electron microscopy (SEM). Meixnerite with a small amount of carbonate was successfully synthesized mechanochemically at ambient conditions by milling for only 3 h in a planetary ball mill.  相似文献   
76.
77.
Sending voltage profile of distribution feeder is controlled by changing a tap of distribution transformer. In a distribution network with distributed generators, for reasons of effect of reversed flows from them and existence of a great number of sending voltage profile candidates, it is not easy to control sending voltage profile within the acceptable voltage limit. In this paper, in order to determine the optical sending voltage profile of distribution transformer in a distribution network with distributed generators, the authors propose a new method to determine the optimal sending voltage profile so as to minimize the total number of tap position's change per day under constraints of acceptable voltage limit. In the proposed method, after calculating acceptable range of three‐phase voltage of distribution feeder, the optimal profile of tap position within the calculated acceptable voltage range is determined among these candidates by using reduced ordered binary decision diagram (ROBDD) which is an efficient enumeration algorithm. In order to check the validity of the proposed method, numerical simulations are carried out for a distribution network model with a distributed generator. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(2): 16–24, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20393  相似文献   
78.
Processability of thermoplastic elastomer (TPE) prepared by radiation-induced grafting of methyl methacrylate (MMA) onto radiation vulcanized natural rubber latex (RVNRL) has been evaluated using a kneader and a hot roll mill at 150°C. It was found that mixing time and revolution rate (rpm) of the kneader have significantly affected the processability. The longer mixing time and the higher revolution rate result in better processability. In such processing conditions, however, the mechanical properties were found to be inferior because the molecular chain scissions occurred during the mixing. A considerable improvement of mechanical properties was obtained when the mixing was carried out without added process oils. Blends of the grafted vulcanized natural rubber latex (RVNRL-g-PMMA) and MMA grafted on unvulcanized natural rubber latex (NRL-g-PMMA) improved processability where the better processability could be achieved at a shorter mixing time and a lower revolution rate. In addition, a comparable value of mechanical properties was obtained.  相似文献   
79.
The evaporation processes of water molecules adsorbed in the edge region of graphene have been investigated by means of direct MO–MD method. A large system composed of 29 water molecules and a graphene sheet (C96H24) was used as a model system. The edge carbon atom of graphene was terminated by hydrogen atom. The geometry optimization showed that the water molecules interact with the hydrogen atoms in the edge region of graphene. At low temperature (300 K), the water molecules were dissociated as water clusters from the graphene. On the other hand, in addition to the dissociation of water clusters, the isolated water molecule was also found as dissociation product at high temperature (500 K). The mechanism of water evaporation was discussed on the basis of theoretical results.  相似文献   
80.
A method for confirming identification of prohibited species tissue in animal feed has been developed on the basis of PCR-RFLP analysis. In Japan, to prevent the spread of BSE through animal feed, the use of animal protein in feed has been regulated. Species-specific PCR detection of prohibited species materials in feed has been used as one of a series of laboratory tests to ensure the proper implementation of the feed regulations. However, since the result of this PCR method is determined only by amplicon length, it is sometimes necessary to confirm whether or not the positive result is due to the effect of a non-specific reaction. For this purpose, DNA sequencing is the best way to confirm the test result but it is not suitable for routine analysis because of the required time and cost. In this study, we developed an easy and rapid method to confirm the species identification (mammals, ruminants and cattle) by using 4 restriction enzymes: SmlI, MboI, BlnI and Hpy188III. This PCR-RFLP method, which ensures identification of prohibited animal species in feed, is useful for enhancing the reliability of feed inspection for BSE prevention. This method will be added to the Official Methods of Feed Analysis.  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