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   20910篇
  免费   550篇
  国内免费   24篇
电工技术   218篇
综合类   18篇
化学工业   4422篇
金属工艺   492篇
机械仪表   365篇
建筑科学   924篇
矿业工程   88篇
能源动力   535篇
轻工业   1399篇
水利工程   261篇
石油天然气   205篇
武器工业   1篇
无线电   1435篇
一般工业技术   3384篇
冶金工业   4521篇
原子能技术   167篇
自动化技术   3049篇
  2022年   147篇
  2021年   241篇
  2020年   198篇
  2019年   263篇
  2018年   296篇
  2017年   303篇
  2016年   366篇
  2015年   292篇
  2014年   459篇
  2013年   1236篇
  2012年   750篇
  2011年   945篇
  2010年   755篇
  2009年   762篇
  2008年   883篇
  2007年   955篇
  2006年   780篇
  2005年   739篇
  2004年   650篇
  2003年   606篇
  2002年   583篇
  2001年   365篇
  2000年   365篇
  1999年   363篇
  1998年   440篇
  1997年   388篇
  1996年   375篇
  1995年   361篇
  1994年   308篇
  1993年   359篇
  1992年   315篇
  1991年   228篇
  1990年   277篇
  1989年   281篇
  1988年   266篇
  1987年   253篇
  1986年   283篇
  1985年   298篇
  1984年   299篇
  1983年   291篇
  1982年   232篇
  1981年   259篇
  1980年   253篇
  1979年   251篇
  1978年   227篇
  1977年   229篇
  1976年   205篇
  1975年   195篇
  1974年   175篇
  1973年   180篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Several types of ink are used in web offset printing. However, heatset inks predominate in general commercial work. In these inks, the vehicle consists of resin dissolved in a solvent, and drying takes place mainly by evaporation. In heatset web offset printing, the printed web is passed through dryers, which raise the temperature of the web enough to cause evaporation of the solvent. leaving only the resin to bind the pigment into a film and to the paper.

Since the solvents used in the heatset inks vary in boiling range from approximately 232° C to 316° C, and the solvent selected depends on the printing conditions, it is necessary to determine the vapor pressure values of heatset inks versus web temperatures for drying calculations. The isoteniscope method is limited to only the vapor pressure measurement of liquids. It cannot be used for materials such as heatset inks. To overcome this difficulty, an apparatus was designed and con- structed by TEC Systems for directly measuring the vapor pressure versus temperature of heatset inks from approximately 21°C to 316°C. In this paper, TEC's apparatus, test procedure developed, and typical test results for pure solvents and heatset inks will be described.  相似文献   
22.
Everyday memory performance was examined longitudinally in 2 groups of Ss meeting the diagnostic criteria for age-associated memory impairment (AAMI). One group of 157 participants in a drug trial for reversing memory loss in AAMI was tested over multiple sessions. The other group of 75 persons did not participate in a drug trial and thus was tested only twice. Both groups were retested for longitudinal follow-up about 4 yrs after initial session. Follow-up test performance remained fairly stable relative to initial performance in both groups. The drug study group showed large practice effects during the course of the drug studies, but these effects subsided after the drug studies' end. Implications regarding memory decline in the normal elderly and neuropsychological measurement issues are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
23.
24.
Summary Styrene polymerization was initiated by methylaluminoxane in the presence of haloalkane. The propagating species are shown by trapping experiments and electron paramagnetic resonance to be both radicals and cations.  相似文献   
25.
Performance on computer-simulated, everyday memory tasks was found to deteriorate with age in 434 Belgian (aged 14–88 yrs) and 434 American Ss matched on gender and age. This age-related memory decline was reasonably consistent across samples. Difficulties in cross-cultural research and the advantages of ecologically valid measurement instruments are discussed. Instruments included a grocery list selective reminding test, the Wechsler Memory Scale, the Benton Visual Retention Test, and the Wechsler Adult Intelligence Scale (WAIS). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
26.
The spectral bandwidth formulae of Stearns and Stearns   are generalized for an arbitrary slit function. Correction coefficients are derived in terms of moments of the slit function. Application to model LED spectra measured with a compact, fiber‐coupled spectrometer having bandwidth of order 12 nm, and a nonlinear wavelength scale shows that accurate LED color measurements may be obtained with such an instrument. Fitting of the relatively broad slit function to line spectra for accurate wavelength calibration is also described. Such fitting, coupled consistently with the bandpass correction, improves the accuracy color measurements with a broad‐response spectrometer. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 374–380, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20242  相似文献   
27.
Bovine spongiform encephalopathy (BSE), or ‘mad cow disease’, is one of several transmissable spongiform encephalopathies (TSEs) known to affect certain mammals and is spread through the ingestion of infected animal tissue. It is believed that the inadvertent contamination of meat and bone meal (MBM) with infected animal tissue and the subsequent use of this material as a feed supplement contributed to the spread of the disease in cattle. As a result, the use of processed animal proteins (PAPs) in animal feeds is regulated in many parts of the world. Although feed testing is the only definitive means to certify compliance, regulatory compliance often relies solely on paper certification. Recently, rapid methods have become available that can be used by regulators to determine compliance during routine inspections. We describe a rapid, immunochromatographic strip test that can detect 0.1% MBM in animal feed. The test takes 15 min to perform and large numbers of samples can be screened for PAPs simultaneously.  相似文献   
28.
29.
One-dimensional linear stability analysis was performed for single-phase lead–bismuth eutectic (LBE) natural circulation. The Nyquist criterion and a root search method were employed to find the linear stability boundary of both forward and backward circulations. It was found that the natural circulations could be linearly unstable in a high Reynolds number region. Increasing loop friction makes a forward circulation more stable, but destabilizes the corresponding backward circulation under the same heating/cooling conditions. The characteristic wavelength of an unstable disturbance is roughly equal to the entire loop length.  相似文献   
30.
ND10 are recently characterized nuclear domains that are composed of 0.5 microm sized, precisely circumscribed dots in cultured human cell lines. To investigate the distribution and number of ND10 on various types of normal and neoplastic human tissues, we carried out immunostaining and immunoprecipitation analyses with monoclonal antibodies 138 and 1150. The number of ND10 varied from 1 to 10 or more in various tissues as did their size. ND10 were diffusely located in early embryonic and normal tissues, except for the exocrine and endocrine cells of the pancreas and for hepatocytes. In normal squamous mucosa, basal cells had more ND10 than did differentiated superficial squamous cells. The number and size of ND10 were markedly increased in malignant neoplasms but were similar in benign tumors and corresponding normal tissues. Sex hormone-related normal tissues, such as the endometrium or myometrium, and neoplasms strongly stained for ND10. The distribution pattern of ND10 in human tissues indicates that they are conserved nuclear substructures that are closely associated with cellular differentiation, hormonal stimulation, and oncogenesis.  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