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   379766篇
  免费   6745篇
  国内免费   1621篇
电工技术   7649篇
技术理论   3篇
综合类   1536篇
化学工业   55325篇
金属工艺   17369篇
机械仪表   14890篇
建筑科学   10148篇
矿业工程   2106篇
能源动力   9113篇
轻工业   28491篇
水利工程   3872篇
石油天然气   5797篇
武器工业   172篇
无线电   44959篇
一般工业技术   77423篇
冶金工业   64580篇
原子能技术   6505篇
自动化技术   38194篇
  2022年   2188篇
  2021年   3575篇
  2020年   2749篇
  2019年   3011篇
  2018年   12980篇
  2017年   13736篇
  2016年   9794篇
  2015年   4455篇
  2014年   6198篇
  2013年   15193篇
  2012年   12062篇
  2011年   19680篇
  2010年   17036篇
  2009年   16770篇
  2008年   17259篇
  2007年   18925篇
  2006年   9642篇
  2005年   11999篇
  2004年   9696篇
  2003年   9465篇
  2002年   7907篇
  2001年   7512篇
  2000年   7178篇
  1999年   7676篇
  1998年   20154篇
  1997年   13787篇
  1996年   10475篇
  1995年   7750篇
  1994年   6867篇
  1993年   6709篇
  1992年   4543篇
  1991年   4416篇
  1990年   4189篇
  1989年   3954篇
  1988年   3828篇
  1987年   3220篇
  1986年   3154篇
  1985年   3445篇
  1984年   3114篇
  1983年   2956篇
  1982年   2799篇
  1981年   2713篇
  1980年   2608篇
  1979年   2426篇
  1978年   2215篇
  1977年   2788篇
  1976年   3946篇
  1975年   1846篇
  1974年   1791篇
  1973年   1730篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
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   
82.
Atom scattering is becoming recognized as a sensitive probe of the electron–phonon interaction parameter λ at metal and metal-overlayer surfaces. Here, the theory is developed, linking λ to the thermal attenuation of atom scattering spectra (in particular, the Debye–Waller factor), to conducting materials of different dimensions, from quasi-1D systems such as W(110):H(1 × 1) and Bi(114), to quasi-2D layered chalcogenides, and high-dimensional surfaces such as quasicrystalline 2ML-Ba(0001)/Cu(001) and d-AlNiCo(00001). Values of λ obtained using He atoms compare favorably with known values for the bulk materials. The corresponding analysis indicates in addition, the number of layers contributing to the electron–phonon interaction, which is measured in an atom surface collision.  相似文献   
83.
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   
84.
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   
85.
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   
86.
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   
87.
88.
89.
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   
90.
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