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   739055篇
  免费   19014篇
  国内免费   7020篇
电工技术   19205篇
技术理论   9篇
综合类   9185篇
化学工业   115979篇
金属工艺   35261篇
机械仪表   29073篇
建筑科学   22740篇
矿业工程   8080篇
能源动力   18247篇
轻工业   55559篇
水利工程   10192篇
石油天然气   22513篇
武器工业   1083篇
无线电   78782篇
一般工业技术   145234篇
冶金工业   105458篇
原子能技术   17510篇
自动化技术   70979篇
  2022年   7233篇
  2021年   11084篇
  2020年   8188篇
  2019年   8684篇
  2018年   17517篇
  2017年   18164篇
  2016年   16372篇
  2015年   11283篇
  2014年   16632篇
  2013年   33739篇
  2012年   25590篇
  2011年   34425篇
  2010年   28857篇
  2009年   29706篇
  2008年   30141篇
  2007年   30525篇
  2006年   22903篇
  2005年   22156篇
  2004年   19328篇
  2003年   18913篇
  2002年   17925篇
  2001年   16698篇
  2000年   15620篇
  1999年   14950篇
  1998年   29893篇
  1997年   21863篇
  1996年   17273篇
  1995年   13497篇
  1994年   12068篇
  1993年   11563篇
  1992年   9193篇
  1991年   8818篇
  1990年   8601篇
  1989年   8324篇
  1988年   7965篇
  1987年   7172篇
  1986年   6880篇
  1985年   7701篇
  1984年   6992篇
  1983年   6694篇
  1982年   6067篇
  1981年   6187篇
  1980年   5902篇
  1979年   6045篇
  1978年   5994篇
  1977年   6480篇
  1976年   8018篇
  1975年   5426篇
  1974年   5204篇
  1973年   5291篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Kamar  M. S.  Shalan  A. S.  Youssef  W. M.  Hussein  A. E. M.  Khawassek  Y. M.  Taha  M. H. 《Radiochemistry》2022,64(2):244-256
Radiochemistry - Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones...  相似文献   
72.

Modern metrics for evaluating agreement coefficients between the experimental results and expert opinion are compared, and the possibility of using these metrics in experimental research in automatic text processing by machine learning methods is assessed. The choice of Cohen’s kappa coefficient as a measure of expert opinion agreement in the NLP and Text Mining problems is justified. An example of using Cohen’s kappa coefficient for evaluating the level of agreement between the opinion of an expert and the results of ML classification and the measure of agreement of expert opinions in the alignment of sentences of the Kazakh-Russian parallel corpus is given. Based on this analysis, it is proved that Cohen’s kappa coefficient is one of the best statistical methods for determining the level of agreement in experimental studies due to its ease of use, computing simplicity, and high accuracy of the results.

  相似文献   
73.
74.
Small interfering RNA (siRNA) can effectively silence target genes through Argonate 2 (Ago2)-induced RNA interference (RNAi). It is very important to control siRNA activity in both spatial and temporal modes. Among different masking strategies, photocaging can be used to regulate gene expression through light irradiation with spatiotemporal and dose-dependent resolution. Many different caging strategies and caging groups have been reported for light-activated siRNA gene silencing. Herein, we describe a novel caging strategy that increases the blocking effect of RISC complex formation/process through host/guest (including ligand/receptor) interactions, thereby enhancing the inhibition of caged siRNA activity until light activation. This strategy can be used as a general approach to design caged siRNAs for the photomodulation of gene silencing of exogenous and endogenous genes.  相似文献   
75.
Wireless Personal Communications - Multiple inputs multiple outputs (MIMO) is a reliable technique which can manage the increased wireless data traffic in the future generation of wireless...  相似文献   
76.
Russian Engineering Research - The modernization of manufacturing by the comprehensive application of digital technology—in both production and management—is considered. Principles are...  相似文献   
77.
78.
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded.  相似文献   
79.
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,...  相似文献   
80.
Russian Engineering Research - The stability of robot-mower motion in a specific direction is considered. The direction is regulated by means of an angular sensor and a programmable controller...  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