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   6084篇
  免费   157篇
  国内免费   14篇
电工技术   131篇
综合类   6篇
化学工业   1086篇
金属工艺   138篇
机械仪表   98篇
建筑科学   139篇
矿业工程   27篇
能源动力   239篇
轻工业   290篇
水利工程   20篇
石油天然气   18篇
无线电   727篇
一般工业技术   1071篇
冶金工业   1443篇
原子能技术   39篇
自动化技术   783篇
  2023年   46篇
  2022年   72篇
  2021年   123篇
  2020年   106篇
  2019年   104篇
  2018年   138篇
  2017年   134篇
  2016年   113篇
  2015年   91篇
  2014年   129篇
  2013年   354篇
  2012年   195篇
  2011年   260篇
  2010年   212篇
  2009年   212篇
  2008年   229篇
  2007年   191篇
  2006年   188篇
  2005年   186篇
  2004年   147篇
  2003年   130篇
  2002年   112篇
  2001年   112篇
  2000年   87篇
  1999年   112篇
  1998年   402篇
  1997年   262篇
  1996年   174篇
  1995年   111篇
  1994年   152篇
  1993年   145篇
  1992年   90篇
  1991年   69篇
  1990年   61篇
  1989年   51篇
  1988年   66篇
  1987年   59篇
  1986年   54篇
  1985年   74篇
  1984年   58篇
  1983年   50篇
  1982年   43篇
  1981年   53篇
  1980年   47篇
  1979年   39篇
  1978年   36篇
  1977年   66篇
  1976年   95篇
  1974年   34篇
  1973年   35篇
排序方式: 共有6255条查询结果,搜索用时 953 毫秒
151.
Wireless Personal Communications - This paper proposes and analyses the power allocation coefficient normalization for successive interference cancellation in power-domain non-orthogonal multiple...  相似文献   
152.
Wireless Personal Communications - The climate has changed absolutely in every area in just a few years as digitized, making high-speed internet service a significant need in the future. Future...  相似文献   
153.
Engineering with Computers - The vibration and damping characteristics of carbon nanotubes reinforced (CNTR) skewed shell structure under a hygrothermal environment have been investigated using the...  相似文献   
154.
Real-Time Systems - Heterogeneous MPSoCs are being used more and more, from cellphones to critical embedded systems. Most of those systems offer heterogeneous sets of identical cores. In this...  相似文献   
155.
Microsystem Technologies - In this paper synthesis of two wideband Metamaterial Cross Polarizer (MCPs) is proposed. The synthesis of proposed MCPs is done by using Binary Wind Driven Optimization...  相似文献   
156.
This study was undertaken to observe the effect of nano-composite coating on steel surface for enhancing its tribological properties. In the investigation, EN31 steel surfaces were coated with nano-composite (Ni-WS2) by pulse current co-deposition process in order to improve the tribological properties of the surface. The coatings were prepared according to different parameter settings. The effect of variations on coating thickness, microstructure, surface morphology, microhardness and tribological properties was observed. The maximum coating thickness of 117?µm with 8% by weight of WS2 particle concentration could be attained with the following parameter settings: applied voltage: 5?V; pulse frequency: 20?Hz; WS2 concentration: 20?g/l; duty factor: 0.6 and bath temperature: 50°C. The average friction coefficient of the deposited surface was 0.11, which is significantly less than that of the EN31 steel surface (average coefficient of friction >?0.5).  相似文献   
157.
In this paper, the authors study the problem of testing the hypothesis of a block compound symmetry covariance matrix with two-level multivariate observations, taken for m variables over u sites or time points. Through the use of a suitable block-diagonalization of the hypothesis matrix, it is possible to obtain a decomposition of the main hypothesis into two sub-hypotheses. Using this decomposition, it is then possible to obtain the likelihood ratio test statistic as well as its exact moments in a much simpler way. The exact distribution of the likelihood ratio test statistic is then analyzed. Because this distribution is quite elaborate, yielding a non-manageable distribution function, a manageable but very precise near-exact distribution is developed. Numerical studies conducted to evaluate the closeness between this near-exact distribution and the exact distribution show the very good performance of this approximation even for very small sample sizes and the approach followed allows us to extend its validity to situations where the population distributions are elliptically contoured. A real-data example is presented and a simulation study is also conducted.  相似文献   
158.
One of the important applications of high tensile steel grades is in wheel rims by the automotive industry. High tensile steel facilitates vehicle weight reduction under the ‘Go Green’ initiative. Along with weight reduction, in recent times, the surface quality requirement of steels for wheel rim applications has also gained a significant focus, and in many cases, it is becoming the cause of rejection at the customers’ processing line. It is known that owing to chemistry requirements such high strength steel grades generally show peritectic behavior during solidification and are prone to surface defects. Tata Steel India produces several wheel rim grades of varying strength levels. In one such high manganese and micro-alloyed peritectic steel grade, the rejection by the customer on account of surface defects was a major concern. The defects consisted of typical longitudinal cracks of varying dimensions along with the unique defects in transverse direction named tear marks on the surface of 100-mm-thick plates rolled from 215-mm-thick slab. In subsequent stages, these plates were processed into rim profiles through hot working by the wheel customer. The paper highlights how systematic study led to arrive at root causes and helped redesign steel chemistry to ensure zero rejection for surface quality without affecting mechanical property requirements.  相似文献   
159.
Development of highly active and stable Pt‐free oxygen reduction reaction catalysts from earth‐abundant elements remains a grand challenge for highly demanded metal–air batteries. Ag‐based alloys have many advantages over platinum group catalysts due to their low cost, high stability, and acceptable oxygen reduction reaction (ORR) performance in alkaline solutions. Nevertheless, compared to commercial Pt/C‐20%, their catalytic activity still cannot meet the demand of commercialization. In this study, a kind of catalysts screening strategy on Agx Cu100?x nanoalloys is reported, containing the surface modification method, studies of activity enhancement mechanism, and applied research on zinc–air batteries. The results exhibit that the role of selective dealloying (DE) or galvanic displacement (GD) is limited by the “parting limitation”, and this “parting limitation” determines the surface topography, position of d‐band center, and ORR performance of Agx Cu100?x alloys. The GD‐Ag55Cu45 and DE‐Ag25Cu75 catalysts alloys present excellent ORR performance that is comparable to Pt/C‐20%. The relationship between electronic perturbation and specific activity demonstrates that positive shift of the d‐band center (≈0.12 eV, relative to Ag) for GD‐Ag55Cu45 is beneficial for ORR, which is contrary to Pt‐based alloys (negative shift, ≈0.1 eV). Meanwhile, extensive electrochemical and electronic structure characterization indicates that the high work function of GD‐Ag55Cu45 (4.8 eV) is the reason behind their excellent durability for zinc–air batteries.  相似文献   
160.
This study for the first time reports on fresh water microalgae Chlorella minutissima aqueous extract (CmAe) which was utilized for the biogenic synthesis of silver nanoparticles and tested their antineoplastic potential against Liver Hepatocellular Carcinoma (HepG2) cell line. The characteristic colour change of the reaction mixture from greenish yellow to yellowish brown confirmed the synthesis of Chlorella minutissima silver nanoparticles (CmAgNPs). Microscopic analysis revealed CmAgNPs to be spherical‐shaped with particle size ranging from 10 to 30 nm. The carbohydrates and proteins distinctive peaks were observed in Fourier transform infrared spectroscopy (FTIR) spectra which suggested these biomolecules acted as reducing and capping agents. Further, the crystalline nature of CmAgNPs was confirmed by X‐ray diffraction (XRD) analysis. CmAgNPs showed maximum free radical scavenging proving it to be more potent antioxidant agent as compared to CmAe. The mortality rate of HepG2 cells treated with CmAgNPs was found to be 91.8 % at 120 μg/ml with IC50 value 12.42 ± 1.096 μg/ml after 48 h whereas no effect was observed on normal Human Embryonic Kidney (HEK 293) cells. Fluorescent images of the treated HepG2 cells revealed the formation of apoptotic bodies, condensed nuclei and cell shrinkage indicating their effectiveness against the cancer cells.Inspec keywords: silver, nanoparticles, nanomedicine, microorganisms, cellular biophysics, nanofabrication, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, proteins, Fourier transform infrared spectra, molecular biophysics, X‐ray chemical analysis, X‐ray diffraction, kidney, cancer, biomedical materialsOther keywords: antineoplastic potential, antioxidant potential, phycofabricated silver nanoparticle, Chlorella minutissima, freshwater microalgae, aqueous extract, liver hepatocellular carcinoma cell line, CmAgNP synthesis, field emission scanning electron microscopy, high‐resolution transmission electron microscopy, atomic force microscopy, dynamic light scattering, carbohydrate, protein, Fourier transform infrared spectroscopy, biomolecule, energy‐dispersive X‐ray spectroscopy, elemental silver signal, CmAgNP crystalline, X‐ray diffraction analysis, antioxidant agent, HepG2 cell mortality rate, human embryonic kidney, HEK 293 cell, fluorescent image, apoptotic body formation, condensed nuclei, cell shrinkage, cancer cell, antineoplastic agent, Ag  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