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   3616篇
  免费   340篇
  国内免费   222篇
电工技术   544篇
综合类   660篇
化学工业   345篇
金属工艺   70篇
机械仪表   160篇
建筑科学   139篇
矿业工程   86篇
能源动力   58篇
轻工业   162篇
水利工程   32篇
石油天然气   111篇
武器工业   16篇
无线电   282篇
一般工业技术   281篇
冶金工业   550篇
原子能技术   26篇
自动化技术   656篇
  2024年   14篇
  2023年   37篇
  2022年   72篇
  2021年   78篇
  2020年   80篇
  2019年   78篇
  2018年   69篇
  2017年   92篇
  2016年   93篇
  2015年   131篇
  2014年   187篇
  2013年   203篇
  2012年   206篇
  2011年   278篇
  2010年   232篇
  2009年   229篇
  2008年   253篇
  2007年   226篇
  2006年   228篇
  2005年   211篇
  2004年   203篇
  2003年   190篇
  2002年   141篇
  2001年   118篇
  2000年   88篇
  1999年   59篇
  1998年   52篇
  1997年   47篇
  1996年   49篇
  1995年   44篇
  1994年   40篇
  1993年   22篇
  1992年   25篇
  1991年   13篇
  1990年   14篇
  1989年   4篇
  1988年   8篇
  1987年   6篇
  1986年   5篇
  1984年   4篇
  1983年   6篇
  1982年   4篇
  1977年   3篇
  1965年   3篇
  1964年   4篇
  1963年   3篇
  1957年   2篇
  1956年   3篇
  1955年   2篇
  1954年   2篇
排序方式: 共有4178条查询结果,搜索用时 15 毫秒
1.
The n-type thermoelectric Bi1.9Lu0.1Te3 was prepared by microwave-solvothermal method and spark plasma sintering. The magnetic field and temperature dependences of transverse magnetoresistance measured within temperature 2–200 K interval allow finding the peculiarities characteristic for strongly disordered and inhomogeneous semiconductors. The first peculiarity is due to appearance of linear-in-magnetic field contribution to the total magnetoresistance reflected in a crossover from quadratic magnetoresistance at low magnetic fields to linear magnetoresistance at high magnetic fields. The linear magnetoresistance can result from the Hall resistance picked up from macroscopically distorted current paths due to local variations in stoichiometry of the compound studied. The second peculiarity is that both linear magnetoresistance magnitude and crossover field are functions of carrier mobility which is in agreement with the Parish and Littlewood model developed for disordered and inhomogeneous semiconductors. An increase in the mobility due to a decrease in temperature is accompanied by an increase in the magnetoresistance magnitude and a decrease in the crossover field. Finally, the third peculiarity is related to the remarkable deviation of the total magnetoresistance measured at various temperatures from the Kohler's rule. Presence of strong inhomogeneity and disorder in the Bi1.9Lu0.1Te3 structure concluded from the magnetoresistance peculiarities can be responsible for the remarkable reduction in the total thermal conductivity of this compound.  相似文献   
2.
3.
Psychologists within a positive psychology framework have proposed the existence of a set of psychological strengths that buffer against the development of psychopathology. To date, most research efforts in positive psychology have focused on adults. This longitudinal study tested the prediction that adolescents' judgments of life satisfaction moderate the influence of stressful life events on the subsequent development of psychopathological behavior. Using a sample of 816 middle and high school students, the study demonstrated support for the moderational model for externalizing behavior outcomes, but not internalizing behavior problems. Specifically, adolescents with positive life satisfaction (vs. those who were dissatisfied with their lives) were less likely to develop later externalizing behaviors in the face of stressful life events. The study also revealed that adolescent life satisfaction reports show moderate stability across a one-year time frame and independently predict subsequent externalizing behavior even while controlling for prior levels of externalizing behavior... (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
4.
5.
The deletion of nine residues from the C-terminus of the bacterialchloramphenicol acetyltransferase (CAT) results in depositionof the mutant protein in cytoplasmic inclusion bodies and lossof chloramphenicol resistance in Escherichia coli. This foldingdefect is relieved by C-terminal fusion of the polypeptide withas few as two residues. Based on these observations, efficientpositive selection for the cloning of DNA fragments has beendemonstrated. The cloning vector encodes a C-terminally truncatedCAT protein. Restriction sites in front of the stop codon allowthe insertion of target DNA, resulting in the production ofproperly folded CAT fusion proteins and regained chloramphenicolresistance. The positive selection of recombinants is accomplishedby growth of transformants on chloramphenicol-containing agarplates. The method appears particularly convenient for the cloningof DNA fragments amplified by the PCR because minimal informationto restore CAT folding can be included in the primers. The cloningof random sequences shows that the folding defect can be relievedby fusion to a wide variety of peptides, providing great flexibilityto the positive selection system. This vector may also contributeto the determination of the role of the C-terminus in CAT folding.  相似文献   
6.
This paper presents a method to compensate voltage sags with minimum energy injection for a series‐connected voltage restorer using a micro‐SMES. A circuit for extracting the fundamental symmetrical components from sag voltages and a minimum energy injection algorithm is described. Simulations of voltage sag compensation have been carried out using PSCAD/EMTDC for various faults. The simulation results confirm the validity of the proposed method and show the possibility of reducing the size of energy storage devices. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(3): 70–80, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10047  相似文献   
7.
对儒家伦理的基本价值与基本特点以及局限性进行了疏理和分析,对于国内外学者对儒家伦理的肯定性评价和提出的有关儒学研究的理论方法作出了评介,在此基础上提出了研究儒家伦理的几点认识和启示.  相似文献   
8.
This study evaluated relations among optimism, perceived stress management skills (PSMS), and positive mood in 46 men who had surgical treatment for localized prostate cancer. The authors found that optimism, PSMS, and positive mood scores were positively correlated. Positive mood was unrelated to demographic and disease-related control variables. In a hierarchical regression model controlling for PSMS, the relationship between optimism and positive mood became nonsignificant, whereas PSMS remained a correlate of positive mood. Results suggest that the relationship between optimism and positive mood may be mediated by belief in being able to use stress management techniques effectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
9.
Some therapists hold that the Bobo and other aggressive toys should be excluded from the playroom as they elicit acting-out behavior that is transferred to the world outside the playroom. However, many therapists view the inclusion of these items as imperative elements that facilitate positive growth and maturation in the child. Interviews with authorities in the field of play therapy support the position that the inclusion of the Bobo is not only useful, but a therapeutic necessity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
10.
Although continuing care is strongly related to positive treatment outcomes for substance use disorder (SUD), participation rates are low and few effective interventions are available. In a randomized clinical trial with 150 participants (97% men), 75 graduates of a residential Veterans Affairs Medical Center SUD program who received an aftercare contract, attendance prompts, and reinforcers (CPR) were compared to 75 graduates who received standard treatment (STX). Among CPR participants, 55% completed at least 3 months of aftercare, compared to 36% in STX. Similarly, CPR participants remained in treatment longer than those in STX (5.5 vs. 4.4 months). Additionally, CPR participants were more likely to be abstinent compared to STX (57% vs. 37%) after 1 year. The CPR intervention offers a practical means to improve adherence among individuals in SUD treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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