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   272435篇
  免费   5135篇
  国内免费   1874篇
电工技术   5645篇
技术理论   5篇
综合类   1178篇
化学工业   44198篇
金属工艺   11367篇
机械仪表   8092篇
建筑科学   6795篇
矿业工程   1733篇
能源动力   6253篇
轻工业   26916篇
水利工程   3073篇
石油天然气   6074篇
武器工业   243篇
无线电   29305篇
一般工业技术   51829篇
冶金工业   48667篇
原子能技术   5793篇
自动化技术   22278篇
  2021年   2962篇
  2020年   2071篇
  2019年   2521篇
  2018年   3924篇
  2017年   3858篇
  2016年   4152篇
  2015年   3066篇
  2014年   5010篇
  2013年   12204篇
  2012年   8181篇
  2011年   10831篇
  2010年   8628篇
  2009年   9170篇
  2008年   9922篇
  2007年   9956篇
  2006年   8744篇
  2005年   7627篇
  2004年   6886篇
  2003年   6406篇
  2002年   6377篇
  2001年   6454篇
  2000年   6045篇
  1999年   6010篇
  1998年   13183篇
  1997年   9734篇
  1996年   7507篇
  1995年   5733篇
  1994年   5251篇
  1993年   5111篇
  1992年   4074篇
  1991年   3892篇
  1990年   3929篇
  1989年   3873篇
  1988年   3646篇
  1987年   3120篇
  1986年   3133篇
  1985年   3510篇
  1984年   3407篇
  1983年   3175篇
  1982年   2785篇
  1981年   2984篇
  1980年   2715篇
  1979年   2890篇
  1978年   2780篇
  1977年   2895篇
  1976年   3764篇
  1975年   2486篇
  1974年   2319篇
  1973年   2348篇
  1972年   2000篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Communications Technology and Electronics - A quantitative comparison of the spectral characteristics of the human visual system and matrix photodetectors is carried out. Criteria for a...  相似文献   
2.
3.
4.
The effect of microwave roasting parameters (300, 450 and 600 W; 5, 10 and 15 min) on acrylamide content in sorghum grain was determined using High Pressure Liquid Chromatography (HPLC)-photo diode array (PDA) detector coupled with C-18 column. Samples roasted at 300 and 450 W did not possess acrylamide, whereas 600 W (15 min) favoured formation of 2740.19 µg/kg of acrylamide, levels far exceeding the defined European Union (EU) limits. The chronic daily intake (CDI) for acrylamide through consumption of such grain flour was 3.25–9.5-fold higher to Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined high exposure limits. The margin of exposure (MOE) values ranged from 4.3 to 12.76 and from 11.07 to 32.27 for neoplastic and neurological effects, respectively, demonstrating high exposure and serious health concerns associated with dietary intake of this toxicant. This study assesses the risk for the Indian population and highlights the importance of optimising process parameters for food product to minimise such exposure risks.  相似文献   
5.
Multimedia Tools and Applications - Currently, Deep Learning is playing an influential role for Image analysis and object classification. Maize’s diseases reduce production that subsequently...  相似文献   
6.

A large amount of data and applications need to be shared with various parties and stakeholders in the cloud environment for storage, computation, and data utilization. Since a third party operates the cloud platform, owners cannot fully trust this environment. However, it has become a challenge to ensure privacy preservation when sharing data effectively among different parties. This paper proposes a novel model that partitions data into sensitive and non-sensitive parts, injects the noise into sensitive data, and performs classification tasks using k-anonymization, differential privacy, and machine learning approaches. It allows multiple owners to share their data in the cloud environment for various purposes. The model specifies communication protocol among involved multiple untrusted parties to process owners’ data. The proposed model preserves actual data by providing a robust mechanism. The experiments are performed over Heart Disease, Arrhythmia, Hepatitis, Indian-liver-patient, and Framingham datasets for Support Vector Machine, K-Nearest Neighbor, Random Forest, Naive Bayes, and Artificial Neural Network classifiers to compute the efficiency in terms of accuracy, precision, recall, and F1-score of the proposed model. The achieved results provide high accuracy, precision, recall, and F1-score up to 93.75%, 94.11%, 100%, and 87.99% and improvement up to 16%, 29%, 12%, and 11%, respectively, compared to previous works.

  相似文献   
7.
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations.  相似文献   
8.
9.
10.
Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi4P4 and IrSi3P3 are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and 29Si and 31P magic angle spinning NMR. In agreement with previous report RuSi4P4 crystallizes in NCS space group P1, while IrSi3P3 is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi4P4 and IrSi3P3 to be wide bandgap (Eg) semiconductors, Eg = 1.9 and 1.8 eV, respectively. RuSi4P4 and IrSi3P3 outperform the current state-of-the-art infrared SHG material, AgGaS2, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi4P4 and IrSi3P3 are promising candidates for longer wavelength NLO materials.  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