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   253939篇
  免费   3200篇
  国内免费   866篇
电工技术   4835篇
综合类   196篇
化学工业   35605篇
金属工艺   9529篇
机械仪表   7588篇
建筑科学   6115篇
矿业工程   889篇
能源动力   7299篇
轻工业   21022篇
水利工程   2221篇
石油天然气   3239篇
武器工业   15篇
无线电   34668篇
一般工业技术   50298篇
冶金工业   49431篇
原子能技术   5105篇
自动化技术   19950篇
  2021年   2167篇
  2020年   1573篇
  2019年   1934篇
  2018年   3292篇
  2017年   3330篇
  2016年   3420篇
  2015年   2237篇
  2014年   3986篇
  2013年   11603篇
  2012年   6304篇
  2011年   8665篇
  2010年   6974篇
  2009年   7952篇
  2008年   8481篇
  2007年   8372篇
  2006年   7444篇
  2005年   6561篇
  2004年   6352篇
  2003年   6612篇
  2002年   6096篇
  2001年   6575篇
  2000年   6016篇
  1999年   6460篇
  1998年   16736篇
  1997年   11558篇
  1996年   8920篇
  1995年   6680篇
  1994年   5964篇
  1993年   5908篇
  1992年   4171篇
  1991年   4055篇
  1990年   3890篇
  1989年   3679篇
  1988年   3582篇
  1987年   3007篇
  1986年   2944篇
  1985年   3197篇
  1984年   2930篇
  1983年   2805篇
  1982年   2627篇
  1981年   2516篇
  1980年   2444篇
  1979年   2277篇
  1978年   2102篇
  1977年   2598篇
  1976年   3575篇
  1975年   1740篇
  1974年   1710篇
  1973年   1652篇
  1972年   1454篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
51.
Russian Journal of Non-Ferrous Metals - This article is devoted to the influence of sodium lignosulfonate (SL), anionic surfactants (sodium dodecylsulfate (SDS), sodium dodecylbenzene sulfonate...  相似文献   
52.
Metallurgical and Materials Transactions A - Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result...  相似文献   
53.
This study deals with the utility of mini spray dryer process to improve the dispersibility, of graphene oxide(GO) and its application for high-performance supercapacitor. Initially, the neutral solution of GO was obtained using the modified Hummer's method. After this, the prepared GO solution was processed by mini spray dryer to obtain a more purified, lighter, and dispersed form of GO which is named as spray dryer processed GO (SPGO). The SPGO thus obtained showed excellent dispersibility behavior with various solvents, which is not found in case of conventional oven drying. Furthermore, utility of SPGO and its reduced form (r-SPGO) for supercapacitor applications have been investigated. Results obtained from the cyclic voltammetry(CV) analysis, impedance, and charge-discharge behavior of supercapacitor fabricated using r-SPGO shows enhanced features. Therefore, the simple spray dried GO and its reduced form, that is, r-SPGO can be utilized as a potential candidate for the supercapacitor application. Herein, as synthesized SPGO exhibited the specific capacitance of 12.07 and 37.6 F/g with PVA-H3PO4 and 1 mol/L H3PO4, respectively, at a scan rate of 5 mV/s. On the other hand, reduced form of SPGO, that is, r-SPGO showed the specific capacitance of 27.16 and 230 F/g with PVA-H3PO4 and 1 mol/L H3PO4, respectively.  相似文献   
54.
Experimental and theoretical studies are performed in order to illuminate, for first time, the intercalation mechanism of polycyclic aromatic molecules into graphite oxide. Two representative molecules of this family, aniline and naphthalene amine are investigated. After intercalation, aniline molecules prefer to covalently connect to the graphene oxide matrix via chemical grafting, while napthalene amine molecules bind with the graphene oxide surface through π–π interactions. The presence of intercalated aromatic molecules between the graphene oxide layers is demonstrated by X‐ray diffraction, while the type of interaction between graphene oxide and polycyclic organic molecules is elucidated by X‐ray photoelectron spectroscopy. Combined quantum mechanical and molecular mechanical calculations describe the intercalation mechanism and the aniline grafting, rationalizing the experimental data. The present work opens new perspectives for the interaction of various aromatic molecules with graphite oxide and the so‐called “intercalation chemistry”.  相似文献   
55.
56.
In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota.  相似文献   
57.
58.
59.
60.
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