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   478篇
  免费   5篇
  国内免费   2篇
电工技术   35篇
化学工业   175篇
金属工艺   12篇
机械仪表   21篇
建筑科学   8篇
能源动力   20篇
轻工业   41篇
水利工程   1篇
无线电   18篇
一般工业技术   104篇
冶金工业   4篇
原子能技术   15篇
自动化技术   31篇
  2023年   2篇
  2022年   8篇
  2021年   15篇
  2020年   6篇
  2019年   6篇
  2018年   1篇
  2017年   3篇
  2016年   5篇
  2015年   10篇
  2014年   23篇
  2013年   30篇
  2012年   22篇
  2011年   34篇
  2010年   17篇
  2009年   16篇
  2008年   26篇
  2007年   19篇
  2006年   22篇
  2005年   24篇
  2004年   20篇
  2003年   20篇
  2002年   17篇
  2001年   8篇
  2000年   9篇
  1999年   12篇
  1998年   12篇
  1997年   3篇
  1996年   4篇
  1995年   5篇
  1994年   9篇
  1993年   8篇
  1992年   5篇
  1991年   5篇
  1990年   3篇
  1989年   7篇
  1988年   5篇
  1987年   5篇
  1986年   7篇
  1985年   7篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   4篇
  1978年   1篇
  1977年   5篇
  1976年   3篇
  1974年   1篇
  1967年   1篇
排序方式: 共有485条查询结果,搜索用时 15 毫秒
91.
To reveal the effect of drying conditions on shrinkage stress existing between a film and a substrate, a polystyrene/toluene solution was coated on a glass substrate, and the volume fraction of toluene at the time when the stress starts to grow (?S) was measured at various drying temperatures and evaporation rates. ?S decreased with increase of drying temperature at a constant evaporation rate, while ?S increased with increase of evaporation rate at a constant drying temperature. From these results, it was suggested that the dominant factors affecting the starting point of stress were both the chain mobility and the measurement time‐scale. Considering the two factors, the tendency of ?S with the drying conditions is quite similar to that of the solvent content at glass transition point, and this fact indicates a strong correlation between the starting point of stress and the glass transition of coated solution. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   
92.
Evaluation of the mental workload during training for ship handling has usually depended on professionals (captain, pilot) who have lots of experience on board. We are attempting to evaluate a ship navigator's mental workload based on a physiological index. The physiological indices, namely heart rate variability (R–R interval), nasal temperature, and salivary amylase, are good indices for reading the mental workload during ship handling. Moreover, we find the possibility of using salivary NO$_{3}^{-}$ as a good index for evaluating the ship navigator's mental workload. Salivary NO$_{3}^{-}$ is expected to have a specific characteristic to represent quick response on the spot and the trend. We confirmed the response of students during simulator training, and then carried out the experiment on professionals on a real ship. We propose that salivary NO$_{3}^{-}$ can show a ship navigator's stress for ship handling in the simulator and on a real ship. This work to evaluate the ship navigator's mental workload using salivary NO$_{3}^{-}$ is the first attempt worldwide. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.  相似文献   
93.
Displacement fields have been calculated around 1/2[111] screw dislocations with various types of core structures in bcc metals. Three types of cores are studied: two types of polarized cores with large and small extensions of the displacement fields and an isotropic core. The difference in the displacement along the [111] direction Δuz from that for the elastic solution has been evaluated for each type of dislocation. In the outside of the core region, the Δuz values are close to zero along the six directions and the regions with Δuz>0 and Δuz<0 are alternately arranged, lying between those directions. Appreciable difference in Δuz has been detected between the polarized cores and the isotropic core up to large distance from the core region. The defocus convergent-beam electron diffraction patterns have been calculated for the dislocations with the incident beam parallel to the dislocation line. Winding and spiral features have been shown in the higher-order Laue zone (HOLZ) lines for the dislocated structures, which have been confirmed by a preliminary experiment. In addition, small shifts of the HOLZ lines have been shown by the calculation between the polarized cores and the isotropic one.  相似文献   
94.
Based on its histochemical properties, the secretory portion of the hamster submandibular gland has been classified as seromucous cells. The presence of endogenous peroxidase (PO) reaction was shown in the nuclear envelope, cisternae of endoplasmic reticulum and Golgi apparatus. The 3,3′‐diaminobenzidene, tetrahydrochloride (DAB) method revealed bipartite secretory granules containing a PO‐positive dense core surrounded by a less dense halo in these cells. In the present investigation, serous and mucous‐like cells were found in resin‐embedded semi‐thin sections of the DAB‐reacted hamster submandibular gland. These sections were already on glass slides for routine light microscopic observations, therefore electron microscopic analysis could be unrealizable. We then used reflectance‐mode confocal laser scanning microscopy to visualize additional sites of PO activity as detected in these sections. Using this approach, we found mucous cells with PO activity‐negative secretory granules and seromucous cells with PO activity‐positive spot‐like secretory granules of the regular sublingual gland most frequently adjacent to the serous cells with typical electron‐dense secretory granules. These cells clearly differ from the seromucous cells with bipartite secretory granules and the granular duct cells with typical electron‐dense secretory granules of the hamster submandibular gland. Additionally, secretory endpieces of the ectopic sublingual gland‐like tissue empty into the duct of the hamster submandibular gland lobule. Thus, our findings suggest that a mass of sublingual gland tissue extends into the hamster submandibular gland during its development, and PO may be synthesized and secreted into the same duct. Microsc. Res. Tech. 76:1284–1291, 2013. © 2013 Wiley Periodicals, Inc.  相似文献   
95.
We investigated impedance perception characteristics of humans in the man-machine interface. Sensibility or operational feel about physical properties of machine dynamics is obtained through perception process. We evaluated the impedance perception characteristics of humans who are operating a mechanical system, based on extended Scheffe’s subjective evaluation method in full consideration of the influence of impedance level, impedance difference, experiment order, individual difference and so on. Constant method based quantitative evaluation was adopted to investigate the influence of motion frequency and change of the impedance on human impedance perception characteristics. Experimental results indicate that humans perceive impedance of mechanical systems based on comparison process of the dynamical characteristics of the systems. The proposed method can be applied to quantify the design requirement of man-machine interface. The effectiveness of the proposed method is verified through experimental results.  相似文献   
96.
97.
CeO2–ZrO2 solid solution catalysts are very effective for the selective synthesis of dimethyl carbonate from methanol and CO2. The activity was much dependent on the calcination temperature. The higher the calcination temperature, the higher the activity of the catalyst for DMC formation, though the BET surface area is lower on the catalyst calcined at higher temperature.  相似文献   
98.
99.
We newly generated an RNA-sequencing-based microRNA (miRNA) expression signature of head and neck squamous cell carcinoma (HNSCC). Analysis of the signature revealed that both strands of some miRNAs, including miR-139-5p (the guide strand) and miR-139-3p (the passenger strand) of miR-139, were downregulated in HNSCC tissues. Analysis of The Cancer Genome Atlas confirmed the low expression levels of miR-139 in HNSCC. Ectopic expression of these miRNAs attenuated the characteristics of cancer cell aggressiveness (e.g., cell proliferation, migration, and invasion). Our in silico analyses revealed a total of 28 putative targets regulated by pre-miR-139 (miR-139-5p and miR-139-3p) in HNSCC cells. Of these, the GNA12 (guanine nucleotide-binding protein subunit alpha-12) and OLR1 (oxidized low-density lipoprotein receptor 1) expression levels were identified as independent factors that predicted patient survival according to multivariate Cox regression analyses (p = 0.0018 and p = 0.0104, respectively). Direct regulation of GNA12 and OLR1 by miR-139-3p in HNSCC cells was confirmed through luciferase reporter assays. Moreover, overexpression of GNA12 and OLR1 was detected in clinical specimens of HNSCC through immunostaining. The involvement of miR-139-3p (the passenger strand) in the oncogenesis of HNSCC is a new concept in cancer biology. Our miRNA-based strategy will increase knowledge on the molecular pathogenesis of HNSCC.  相似文献   
100.
A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1 K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.  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