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   1320篇
  免费   48篇
  国内免费   27篇
电工技术   40篇
综合类   193篇
化学工业   203篇
金属工艺   244篇
机械仪表   32篇
建筑科学   39篇
矿业工程   12篇
能源动力   31篇
轻工业   76篇
水利工程   12篇
石油天然气   39篇
武器工业   7篇
无线电   137篇
一般工业技术   139篇
冶金工业   111篇
自动化技术   80篇
  2020年   9篇
  2019年   8篇
  2017年   14篇
  2016年   24篇
  2015年   8篇
  2014年   11篇
  2013年   35篇
  2012年   26篇
  2011年   33篇
  2010年   26篇
  2009年   12篇
  2008年   29篇
  2007年   24篇
  2006年   36篇
  2005年   24篇
  2004年   50篇
  2003年   17篇
  2002年   19篇
  2001年   20篇
  2000年   43篇
  1999年   32篇
  1998年   60篇
  1997年   29篇
  1996年   33篇
  1995年   25篇
  1994年   46篇
  1993年   76篇
  1992年   54篇
  1991年   21篇
  1990年   12篇
  1989年   14篇
  1988年   19篇
  1987年   14篇
  1986年   31篇
  1985年   15篇
  1984年   11篇
  1982年   10篇
  1981年   7篇
  1979年   9篇
  1977年   8篇
  1976年   9篇
  1966年   13篇
  1965年   37篇
  1964年   38篇
  1963年   39篇
  1962年   55篇
  1961年   58篇
  1960年   58篇
  1959年   29篇
  1958年   6篇
排序方式: 共有1395条查询结果,搜索用时 62 毫秒
81.
82.
Fe-Ni-Mn合金中等温马氏体的生长过程   总被引:1,自引:0,他引:1  
杨大智  朱敏 《金属学报》1988,24(4):236-241
本文采用透射电子显微镜研究了Fe-21Ni-4Mn合金中等温马氏体的生长过程,着重探讨了生长过程中亚结构的发展和变化.结果表明,在马氏体生长的初期阶段,小的薄片状马氏体的亚结构完全是以(112)_b为孪晶面的孪晶,并且贯穿整个片内,相界面平直向前生长.稍后阶段,片的生长主要集中在一侧,此例相界面弯曲向前生长,出现非孪晶区域,内含大量位错,同时,片的孪晶弯曲.生长到后期,弯曲的相界面变为平直,邻近相同位向的小片相互联接在一起,形成一宏观惯习面为(252)_f的大马氏体片,而构成大片的小马氏体片的惯习面为(121)_f.  相似文献   
83.
The technology of microalloyed steels is expanding beyond its original emphasis on low-carbon, severely control-rolled strip and plate products. A variety of economical, high-strength, tough, as-rolled or as-forged microalloyed products are replacing more expensive heat-treated steels. Recrystallization-controlled rolling is being utilized to produce very fine ferrite grain sizes and good toughness in strip, plate and bar products processed with relatively high rolling temperatures. High-strength microalloyed long products such as railroad joint bars, truck frame rails and flat bars for truck trailer construction are replacing heat-treated parts. Microalloyed, medium-carbon forging steels are used extensively for automobile engine and suspension components. Fully pearlitic high-carbon rods are being microalloyed to enhance the properties of wire and springs.  相似文献   
84.
The presentation of the main results attained today in the field of metrological reliability must be preceded by isolating some principal problems. The first concerns the reliability of measurements and the reliability of measuring instruments, while the second concerns the definition of the metrological failure. The third problem is to do with the classification of characteristics of the metrological reliability.The paper will discuss that part of the metrological reliability which deals with the hardware, that is, with instrumental reliability. Basic models used in metrological reliability will be evaluated. A relevant aim of the paper is to describe the present state and to express some new ideas about the future development of metrological reliability.  相似文献   
85.
The cover image, a 3D stationary salami structure of a green/red/black ternary polymer blend and the separated red and green continuous structure, is by QUI TRAN‐CONG‐MIYATA, based on the Editorial In Focus section: Polymer Research at KIT, Japan, DOI: 10.1002/pi.5248 .

  相似文献   

86.
Recently, there have been considerable interests to immobilize photocatalyst in alginate beads for removing pollutants from water sources. However, the feasibility of using alginate beads in industry largely depends on its long‐term stability during operation. This study investigated the physicochemical stability of alginate/titanium dioxide beads (Alg/TiO2) when exposed to UV irradiation in aqueous environment. The degradation of Alg/TiO2 beads was evident because the diameter and mass of the beads was reduced by 12% and 40%, respectively, after 120 h of irradiation. A substantial amount of TiO2 was leached into the external medium. Consequently, the removal efficiency of model cationic dye was found to reduce after every process cycle. Morphological analysis showed the formation of cavities on the surface of the Alg/TiO2 beads. Interestingly, the blank alginate beads degraded more rapidly than the Alg/TiO2 beads, confirming the UV‐shielding effect of TiO2. Nevertheless, this study reveals the need to improve the UV stability of alginate‐based beads before they can be considered for practical application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45002.  相似文献   
87.
This study aimed to model the kinetic of hydro-distillation of Aquilaria malaccensis leaves oil in order to understand and optimize the extraction process. In addition, this study, for the first time, aimed to identify the chemical compositions of the A. malaccensis leave-oil. By assessing both first-order kinetic model and the model of simultaneous washing and diffusion, the result indicated that the model of simultaneous washing and diffusion better describes the hydro-distillation mechanism of the essential oil from A. malaccensis leaves.The optimum time, solid to liquid ratio, and the heating power for extracting the highest amount of essential oil were found to be around 3 h, 1:10(g·ml-1), and 300 W respectively. Yellow essential oil with a strong smell and a yield of 0.05 v/w was extracted by hydro-distillation Clevenger apparatus. Chemical compounds of the essential oil were analyzed using gas chromatography–mass spectroscopy(GC/MS), which resulted in identification of 42 compounds that constitute 93% of essential oil. Among the identified components,Pentadecanal(32.082%), 9-Octadecenal,(Z)(15.894%), and Tetradecanal(6.927%) were the major compounds.Considering the fact that all the identified major components possess pesticidal properties, A. malaccensis leaves can be regarded as a promising natural source for producing pesticides.  相似文献   
88.
Local and temporal variations of the particle cloud formed in a cylindrical mixing vessel were investigated experimentally. Different particle sizes (0.5, 1, and 2 mm) and volumetric concentration up to 20 vol % were evaluated at different impeller speeds. The time‐averaged cloud height was linear with impeller frequency and with volume concentration. Suspensions with larger particles had a lower average cloud height, while the standard deviation for the temporal cloud height variation was larger. Two strong periodic phenomena were identified to be dominating the particle cloud height variations. The frequencies were linear with impeller speed, resulting in dimensionless frequencies of S1=0.02–0.03 and S2=0.05–0.06. The frequencies were affected by neither the particle size nor the volumetric concentration. The amplitude showed no dependency on the particle size, but the S2 amplitude significantly decreases and S1 increases with increasing solid concentration. The results were compared to LES/discrete element method simulations and showed a fair agreement. © 2015 American Institute of Chemical Engineers AIChE J, 62: 338–348, 2016  相似文献   
89.
FKBP5 encodes FK506-binding protein 5, a glucocorticoid receptor (GR)-binding protein implicated in various psychiatric disorders and alcohol withdrawal severity. The purpose of this study is to characterize alcohol preference and related phenotypes in Fkbp5 knockout (KO) mice and to examine the role of FKBP5 in human alcohol consumption. The following experiments were performed to characterize Fkpb5 KO mice. (1) Fkbp5 KO and wild-type (WT) EtOH consumption was tested using a two-bottle choice paradigm; (2) The EtOH elimination rate was measured after intraperitoneal (IP) injection of 2.0 g/kg EtOH; (3) Blood alcohol concentration (BAC) was measured after 3 h limited access of alcohol; (4) Brain region expression of Fkbp5 was identified using LacZ staining; (5) Baseline corticosterone (CORT) was assessed. Additionally, two SNPs, rs1360780 (C/T) and rs3800373 (T/G), were selected to study the association of FKBP5 with alcohol consumption in humans. Participants were college students (n = 1162) from 21–26 years of age with Chinese, Korean or Caucasian ethnicity. The results, compared to WT mice, for KO mice exhibited an increase in alcohol consumption that was not due to differences in taste sensitivity or alcohol metabolism. Higher BAC was found in KO mice after 3 h of EtOH access. Fkbp5 was highly expressed in brain regions involved in the regulation of the stress response, such as the hippocampus, amygdala, dorsal raphe and locus coeruleus. Both genotypes exhibited similar basal levels of plasma corticosterone (CORT). Finally, single nucleotide polymorphisms (SNPs) in FKBP5 were found to be associated with alcohol drinking in humans. These results suggest that the association between FKBP5 and alcohol consumption is conserved in both mice and humans.  相似文献   
90.
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