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   324962篇
  免费   3518篇
  国内免费   917篇
电工技术   6446篇
综合类   278篇
化学工业   45623篇
金属工艺   15848篇
机械仪表   13038篇
建筑科学   7455篇
矿业工程   1613篇
能源动力   7994篇
轻工业   22509篇
水利工程   3247篇
石油天然气   4611篇
武器工业   16篇
无线电   40963篇
一般工业技术   68579篇
冶金工业   53967篇
原子能技术   6104篇
自动化技术   31106篇
  2022年   1541篇
  2021年   2340篇
  2020年   1690篇
  2019年   2069篇
  2018年   11418篇
  2017年   12037篇
  2016年   8064篇
  2015年   2824篇
  2014年   4199篇
  2013年   11759篇
  2012年   8897篇
  2011年   16763篇
  2010年   14629篇
  2009年   14532篇
  2008年   14658篇
  2007年   16600篇
  2006年   7476篇
  2005年   10040篇
  2004年   8204篇
  2003年   8103篇
  2002年   6662篇
  2001年   6590篇
  2000年   6121篇
  1999年   6417篇
  1998年   16498篇
  1997年   11422篇
  1996年   8817篇
  1995年   6622篇
  1994年   5939篇
  1993年   5876篇
  1992年   4148篇
  1991年   4050篇
  1990年   3861篇
  1989年   3652篇
  1988年   3571篇
  1987年   3019篇
  1986年   2948篇
  1985年   3212篇
  1984年   2930篇
  1983年   2830篇
  1982年   2643篇
  1981年   2546篇
  1980年   2462篇
  1979年   2307篇
  1978年   2111篇
  1977年   2608篇
  1976年   3563篇
  1975年   1764篇
  1974年   1733篇
  1973年   1668篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
51.
52.
Litvyak  V. M.  Cherbunin  R. V.  Kalevich  V. K.  Kavokin  K. V. 《Semiconductors》2020,54(12):1728-1729
Semiconductors - We found bulk n-GaAs layers grown by liquid phase epitaxy to be irregularly stressed. Deformation created by this stress causes a small but detectable quadrupole splitting of...  相似文献   
53.
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   
54.
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   
55.
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   
56.
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   
57.
58.
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   
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