首页 | 官方网站   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   579篇
  免费   28篇
  国内免费   1篇
工业技术   608篇
  2023年   4篇
  2022年   13篇
  2021年   16篇
  2020年   8篇
  2019年   18篇
  2018年   16篇
  2017年   15篇
  2016年   18篇
  2015年   8篇
  2014年   27篇
  2013年   40篇
  2012年   45篇
  2011年   49篇
  2010年   33篇
  2009年   38篇
  2008年   39篇
  2007年   41篇
  2006年   24篇
  2005年   26篇
  2004年   16篇
  2003年   14篇
  2002年   16篇
  2001年   7篇
  2000年   3篇
  1999年   6篇
  1998年   12篇
  1997年   7篇
  1996年   7篇
  1995年   3篇
  1994年   5篇
  1993年   5篇
  1991年   2篇
  1990年   2篇
  1989年   2篇
  1987年   3篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   3篇
  1973年   3篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
排序方式: 共有608条查询结果,搜索用时 359 毫秒
81.
A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.  相似文献   
82.
La(3+) and not Ca(2+) increases methanol dehydrogenase (MDH) activity in Methylobacterium radiotolerans NBRC15690. La(3+)- and Ca(2+)-MDH-like proteins were found to be homodimeric (α(2)) and heterotetrameric (α(2)β(2)), respectively. N-terminal amino acid sequences of these proteins revealed that La(3+)- and Ca(2+)-MDH-like proteins were encoded by xoxF and mxaFI, respectively.  相似文献   
83.
折叠之舞     
这所住宅位于日本古老的首都--京都中心传统住宅街区内,由建筑师Kentaro Takeguchi+Asako Yamamoto/ALPHAVILLE共同设计建造。由于地区性建筑规范和邻里关系的制约,住宅外部延续了日本传统木制别墅的特征,尽量低调谦和地融入外部传统街区环境之中。当夜暮降临,透过住宅临街的木质格栅散透出柔和的暖光,晕染着这个  相似文献   
84.
Polysaccharides extracted from human tubercle bacilli (specific substance of Maruyama [SSM]) have been clinically applied with satisfactory results. Thymidylate synthetase (TS) and thymidine kinase (TK) are key enzymes in de novo and salvage pathways for pyrimidine nucleotide synthesis. Well- and moderately well differentiated adenocarcinomas induced with 1,2-dimethylhydrazine (DMH) are widely distributed throughout the colorectal tract with high TK activity, and the poorly differentiated type is mainly restricted in the proximal colon and the cecum with high TS activity in rats. Subcutaneously injecting the rats with SSM reduced TS activity in colonic nontumorous regions, but in the tumorous regions it reduced TK activity compared with that of the DMH-treated rats without SSM treatment. SSM is suggested to reduce the colorectal carcinogenesis induced with DMH by inhibiting DNA synthesis in a de novo pathway, and to suppress the development of the tumors by decreasing DNA synthesis in the salvage pathway in rats.  相似文献   
85.
We report on the direct deposition of high-quality ZrO2 thin films on various kinds of substrates by the liquid phase deposition method. After reaction for 24 h, thin films formed on various kinds of substrates, and the obtained thin film was comprised of densely packed nano-sized particles. The film annealed at 500°C showed a tetragonal phase at room temperature and this phenomenon has been discussed from the viewpoint of crystallite size effect. The result of optical transmittance measurement revealed that high transparency, more than 70% transmittance, has been achieved for the film after annealing at 900°C.  相似文献   
86.
The time variations in the electrode potential and mass of an electrodeposited CdTe layer when immersed in a deposition bath under an open-circuit condition were examined using an electrochemical QCM in order to observe the oxidation behavior due to dissolved oxygen. The morphology, composition, and crystallinity of the CdTe layer were also examined by SEM, EPMA, and XRD measurements. In the early stage of immersion, mostly only Cd atoms in the CdTe were found to dissolve from the zinc blende-type CdTe lattice, keeping the flat and smooth surface morphology intact. Then, the remaining Te formed a lattice of elemental Te and covered the CdTe layer. The electrolyte could penetrate the Te layer and access the CdTe layer's surface because the Te layer was porous due to the elution of Cd atoms. Therefore, the preferential dissolution of Cd species continued to occur, and finally, only the porous Te layer remained on the substrate. This dissolution of CdTe supports the validity of the potential-pH diagram of the Cd-Te-NH3-H2O system.  相似文献   
87.
Bioassays were performed on malePeriplaneta americana L. using synthetic (–)-periplanone-B (P-B) and Hauptmann's (–)-periplanone-A (P-A), and their mixtures at various ratios to estimate the roles of both periplanones for the sexual communication of the species. Both P-A and P-B elicited qualitatively the same responses, such as antennal movement, rapid locomotion, wing raising, and homosexual behavior of male cockroaches, but the threshold of the pheromone activities for P-B was two orders of magnitude lower than that of P-A. Neither synergistic nor inhibitory but only a simple integrated effect on the responses was observed when mixtures of P-A and P-B were applied.  相似文献   
88.
89.
The nodular type of muscular sarcoidosis has been known to show characteristic MR findings: however, MR imaging features after steroid therapy have not been reported. A 48-year-old man with nodular type of muscular sarcoidosis is reported. Prior to steroid therapy, axial MR images showed peripheral increased signal intensity and central star-shaped decreased signal intensity. Coronal images showed an inner stripe of decreased signal intensity and outer stripes of increased signal intensity. After steroid therapy, axial images showed only the central star-shaped area of decreased signal intensity. Coronal images showed only the inner stripe of decreased signal intensity. It is important to know that the central area will continue to exist after steroid therapy.  相似文献   
90.
The deformation of plasma-sprayed alumina droplets of 35-55 μm diameter d with an impact velocity of around 90 m/s has been investigated over various micro-patterned substrates with an arithmetic mean roughness of 0.5 μm. On a line-and-space pattern, droplets exhibited elliptical splats extending in the direction perpendicular to the line, when the normalized pattern spacing λ (= x/d) was 0.1-0.3, where x is the pattern spacing. The fingering of the splats was also caused by a concave pattern as well as by a convex pattern and the number of fingers significantly increased at λ = 0.2. In addition, holes suggesting air entrapment were observed off center in the bottom side of each splat by approximately 1.5 times the radius of the droplets, regardless of the pattern. These results suggest the importance of the surface design of substrate on the micrometer scale in plasma spraying.  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-23

京公网安备 11010802026262号