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   468217篇
  免费   4846篇
  国内免费   1068篇
电工技术   8355篇
综合类   273篇
化学工业   70511篇
金属工艺   22907篇
机械仪表   16192篇
建筑科学   9760篇
矿业工程   4284篇
能源动力   10365篇
轻工业   29236篇
水利工程   5865篇
石油天然气   14753篇
武器工业   40篇
无线电   51071篇
一般工业技术   104403篇
冶金工业   77055篇
原子能技术   14597篇
自动化技术   34464篇
  2021年   4500篇
  2019年   4272篇
  2018年   7908篇
  2017年   8204篇
  2016年   8616篇
  2015年   4885篇
  2014年   8560篇
  2013年   20066篇
  2012年   12542篇
  2011年   16292篇
  2010年   13205篇
  2009年   14894篇
  2008年   15440篇
  2007年   15058篇
  2006年   12836篇
  2005年   11296篇
  2004年   11024篇
  2003年   11089篇
  2002年   10487篇
  2001年   10784篇
  2000年   10233篇
  1999年   10081篇
  1998年   22899篇
  1997年   16576篇
  1996年   12714篇
  1995年   9799篇
  1994年   8897篇
  1993年   8990篇
  1992年   6933篇
  1991年   6879篇
  1990年   6854篇
  1989年   6534篇
  1988年   6354篇
  1987年   5843篇
  1986年   5698篇
  1985年   6106篇
  1984年   5761篇
  1983年   5536篇
  1982年   5216篇
  1981年   5196篇
  1980年   5144篇
  1979年   5120篇
  1978年   5139篇
  1977年   5638篇
  1976年   7033篇
  1975年   4594篇
  1974年   4639篇
  1973年   4640篇
  1972年   4080篇
  1971年   3625篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
61.
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers.  相似文献   
62.
Jori  Popat K.  Jadhav  Vrushali H. 《Catalysis Letters》2022,152(6):1703-1710
Catalysis Letters - A new zirconium based carbonaceous solid acid catalyst Zr@CC-PA with both Lewis and Bronsted acidic sites was prepared by simultaneous carbonization and phosphonation of glucose...  相似文献   
63.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
64.
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing...  相似文献   
65.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
66.
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food...  相似文献   
67.
68.
69.
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally.  相似文献   
70.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  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