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   604478篇
  免费   11152篇
  国内免费   2066篇
电工技术   10748篇
综合类   537篇
化学工业   91182篇
金属工艺   19894篇
机械仪表   17040篇
建筑科学   16888篇
矿业工程   1327篇
能源动力   16585篇
轻工业   65585篇
水利工程   4834篇
石油天然气   3450篇
武器工业   21篇
无线电   77401篇
一般工业技术   109519篇
冶金工业   115659篇
原子能技术   7752篇
自动化技术   59274篇
  2021年   4477篇
  2020年   3368篇
  2019年   4170篇
  2018年   6579篇
  2017年   6578篇
  2016年   7192篇
  2015年   5690篇
  2014年   9073篇
  2013年   29367篇
  2012年   15958篇
  2011年   22312篇
  2010年   17279篇
  2009年   19408篇
  2008年   20612篇
  2007年   20884篇
  2006年   18793篇
  2005年   17275篇
  2004年   16687篇
  2003年   16320篇
  2002年   15591篇
  2001年   15789篇
  2000年   14505篇
  1999年   15528篇
  1998年   37291篇
  1997年   26658篇
  1996年   20519篇
  1995年   15804篇
  1994年   13922篇
  1993年   13593篇
  1992年   9824篇
  1991年   9372篇
  1990年   8829篇
  1989年   8476篇
  1988年   8178篇
  1987年   6793篇
  1986年   6633篇
  1985年   8166篇
  1984年   7550篇
  1983年   6682篇
  1982年   6171篇
  1981年   6244篇
  1980年   5822篇
  1979年   5498篇
  1978年   5105篇
  1977年   6307篇
  1976年   8469篇
  1975年   4297篇
  1974年   4078篇
  1973年   4010篇
  1972年   3138篇
排序方式: 共有10000条查询结果,搜索用时 491 毫秒
991.
Eliminating the adoption barrier   总被引:1,自引:0,他引:1  
Krueger  C. 《Software, IEEE》2002,19(4):29-31
  相似文献   
992.
Beef and pork frankfurters were produced with 0, 5, 10, and 15% of the meat block being mechanically separated spleen (MSS). No fatting or peelability problems were experienced. Frankfurters were held at 2°C and evaluated at 2-wk intervals for 6 wk. Consumer panelists rated all products acceptable. A bi-monthly laboratory taste panel evaluated all frank furters (except the 15% product) acceptable during storage. Allo-Kramer shear values decreased with increased MSS, Frankfurters with 5, 10, and 15% MSS had 2.2, 3.9, and 4.9 times more iron than the control, respectively. Level of MSS did not influence bacterial numbers.  相似文献   
993.
A new technique for mixing optical waves to generate microwave-frequency signals using an injection laser diode and a fibre-optic interferometer is reported. A beat signal is produced by interfering light from the laser with light from the same laser emitted earlier at a different frequency. The interferometer consists of an evanescent-field fibre coupler joined to a length of single-mode optical fibre. The laser is tuned by pulsed or bipolar current waveforms superimposed on a DC bias current. Feedback from an external cavity stabilises the laser frequency and reduces its linewidth. Efficient mixing at difference frequencies from 250 MHz to 2 GHz is obtained, with spectral widths of less than 1% of the centre frequency.  相似文献   
994.
995.
The "Wisconsin process'(a combination of lactic acid starter culture and sucrose) has previously been shown to be effective in preventing botulinum toxigenesis in reduced nitrite bacon. This technology has been applied to other low-acid refrigerated foods which receive less than a 12D thermal process. A combination of Pediococcus acidilactici and dextrose was effective in preventing botulinum toxigenesis in chicken salad. When the chicken salad was temperature abused, the P. acidilactici catabolized available dextrose to lactic acid. Extracellular accumulation of the lactic acid caused a decrease in the pH of the product. Pathogen challenge tests verified that the rate and extent of lactic acid accumulation in the chicken salad during temperature abuse was sufficient to preclude botulinum toxigenesis. This technology has the potential to be of use in a variety of low-acid refrigerated foods.  相似文献   
996.
Cotton fabric was crosslinked with five agents, three of which were prepared form formaldehyde and two of which were formaldehyde-free. The formaldehyde-free agents produced less bonding between layers in the laminated microstructure of the cotton fiber. One agent, 4,5-dihydroxy-1,3-dimethyl-2-imidazolidinone, gave no evidence of any interlayer bonding. All five agents gave the same relationship between wrinkle recovery angle and molar substitution on the cotton up to moderate recovery angles, but only agents based on formaldehyde gave higher wrinkle recovery angles with additional reaction. Intralayer crosslinking did not reduce absorptivity, as shown by moisture regain and dye receptivity, but did restrict swelling in cupriethylenediamine hydroxide to the same extent as combined interlayer and intralayer crosslinking. The decrease in extensibility of treated fabric with increasing wrinkle recovery angle was the same with all agents. These results indicate the regions of the fiber that are important for each of these properties.  相似文献   
997.
The phospholipids of the spongePolymastia gleneni contain saturated long chain (C22–30)-acetoxy fatty acids. Their structures were assigned based on chromatographic and spectrometric data as well as comparison with a synthetic sample. The use of capillary gas chromatography combined with chemical ionization and electron impact mass spectrometry was instrumental in the eludication of structures, since only a very small amount of crude lipids was available. Part 10 of “Phospholipids in Marine Organisms.” For Part 9 in this series, see reference 12.  相似文献   
998.
The separate contributions of impellers and stators to suction are studied by means of interaction models. From these, suction can be predicted when interchangeable components are used in any combination, and in either direction of impeller rotation. Methods are devised by which numerical values of the impeller and stator terms can be simply assigned. The resulting model provides good agreement with experiment. The influence of variability in component geometry is reflected in the model parameters. Possible applications of the model are suggested.  相似文献   
999.
Broadline nuclear magnetic resonance measurements have been carried out for the proton resonance in oriented poly(vinylidene fluoride). The spectra in general show two component lines with distinctly different line widths. The broad component shows a high degree of molecular orientation and can be satisfactorily assigned to the crystalline regions of the polymer. The narrow component corresponds to an oriented non crystalline phase which is sufficiently constrained to allow motion about the chain axis only. An appreciable decrease in the value of the rigid mass fraction was observed in both of the samples over the temperature range examined. Our calculations indicate that this could play an important role in the temperature dependence of the pyroelectric response of this material.  相似文献   
1000.
P.J. Campion 《Measurement》1985,3(3):121-124
Two complementary national laboratory accreditation schemes are run by the National Physical Laboratory (NPL) to provide official recognition of competent British laboratories and an assurance of quality to their customers. The first of these, the British Calibration Service (BCS), was set up in 1966 to accredit laboratories to calibrate instruments, gauges and reference materials. In 1981 the National Testing Laboratory Accreditation Scheme (NATLAS) was formed to extend the service to all kinds of testing. Both BCS and NATLAS form an integral part of the UK national measurement system and were combined to form the National Measurement Accreditation Service on 1 October 1985.  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