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   418690篇
  免费   6874篇
  国内免费   2199篇
电工技术   8384篇
技术理论   1篇
综合类   1198篇
化学工业   62283篇
金属工艺   17413篇
机械仪表   14341篇
建筑科学   9386篇
矿业工程   2449篇
能源动力   11994篇
轻工业   30038篇
水利工程   4597篇
石油天然气   8468篇
武器工业   123篇
无线电   50852篇
一般工业技术   85011篇
冶金工业   76489篇
原子能技术   9337篇
自动化技术   35399篇
  2022年   3280篇
  2021年   4809篇
  2020年   3580篇
  2019年   4274篇
  2018年   6997篇
  2017年   7096篇
  2016年   7454篇
  2015年   5016篇
  2014年   8026篇
  2013年   21031篇
  2012年   12510篇
  2011年   16445篇
  2010年   13123篇
  2009年   14641篇
  2008年   14906篇
  2007年   14582篇
  2006年   13128篇
  2005年   11677篇
  2004年   10896篇
  2003年   10734篇
  2002年   10135篇
  2001年   10025篇
  2000年   9361篇
  1999年   9746篇
  1998年   24693篇
  1997年   16992篇
  1996年   13010篇
  1995年   9652篇
  1994年   8472篇
  1993年   8479篇
  1992年   6107篇
  1991年   5728篇
  1990年   5731篇
  1989年   5354篇
  1988年   5073篇
  1987年   4446篇
  1986年   4321篇
  1985年   4837篇
  1984年   4442篇
  1983年   4011篇
  1982年   3671篇
  1981年   3767篇
  1980年   3444篇
  1979年   3340篇
  1978年   3346篇
  1977年   3773篇
  1976年   4876篇
  1975年   2860篇
  1974年   2663篇
  1973年   2733篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
41.
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...  相似文献   
42.
The influence of the microstructure on the corrosion rate of three monolithic SiC samples in FLiNaK salt at 900 °C for 250 h was studied. The SiC samples, labeled as SiC-1, SiC-2, and SiC-3, had corrosion rates of 0.137, 0.020, and 0.043 mg/cm2h, respectively. Compared with grain size and the presence of special grain boundaries (i.e., Σ3), the content of high-angle grain boundaries (HAGBs) appeared to have the strongest influence on the corrosion rate of SiC in FLiNaK salt, since the corrosion rate increased six times as the concentration of high-angle grain boundaries increased from 19 to 32% for SiC-2 and SiC-1, respectively. These results stress the importance of controlling the content of HAGBs during the production process of SiC.  相似文献   
43.
Theoretical Foundations of Chemical Engineering - The corona onset voltage is an important operating parameter in the electrostatic precipitation of nanoparticulate, however, its experimental...  相似文献   
44.
Herein, we report the photosensing property of CdS thin films. CdS thin films were coated onto glass substrates via a spray pyrolysis method using different spray pressures. Prepared films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical and photoluminescence spectroscopy. XRD analysis demonstrated the growth of crystalline CdS films with crystallite sizes varying from 26 to 29 nm depending on the pressure. The SEM and EDAX analyses revealed nearly-stoichiometric CdS films with smooth surfaces and slight variation in grain morphology due to pressure changes. Optical measurements showed a direct bandgap varying from 2.37 eV to 2.42 eV due to pressure changes. A photodetector was also fabricated using the grown CdS films; the fabricated photodetector exhibited good performance depending on the spray pressure. A spray pressure of 1.5 GPa resulted in high photoresponsivity and external quantum efficiency.  相似文献   
45.
Golubev  N. V.  Ignat’eva  E. S.  Maurus  A. A.  Ziyatdinova  M. Z.  Lopatina  E. V.  Lorenzi  R.  Paleari  A.  Sigaev  V. N. 《Glass and Ceramics》2021,77(11-12):415-418
Glass and Ceramics - The influence of Al2O3 as an additive and the heat-treatment regime on the luminescence spectra of gallate glass-ceramics was investigated. It is shown that its luminescence...  相似文献   
46.
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   
47.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
48.
49.
50.
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