全文获取类型
收费全文 | 421257篇 |
免费 | 5881篇 |
国内免费 | 1372篇 |
专业分类
电工技术 | 7747篇 |
综合类 | 330篇 |
化学工业 | 63437篇 |
金属工艺 | 16861篇 |
机械仪表 | 13810篇 |
建筑科学 | 9182篇 |
矿业工程 | 2236篇 |
能源动力 | 12008篇 |
轻工业 | 29624篇 |
水利工程 | 4487篇 |
石油天然气 | 8106篇 |
武器工业 | 17篇 |
无线电 | 50456篇 |
一般工业技术 | 85934篇 |
冶金工业 | 78986篇 |
原子能技术 | 9330篇 |
自动化技术 | 35959篇 |
出版年
2022年 | 2400篇 |
2021年 | 4084篇 |
2020年 | 3112篇 |
2019年 | 4032篇 |
2018年 | 6739篇 |
2017年 | 6736篇 |
2016年 | 7257篇 |
2015年 | 4571篇 |
2014年 | 7540篇 |
2013年 | 21152篇 |
2012年 | 12057篇 |
2011年 | 16089篇 |
2010年 | 12810篇 |
2009年 | 14399篇 |
2008年 | 14823篇 |
2007年 | 14656篇 |
2006年 | 13115篇 |
2005年 | 11772篇 |
2004年 | 11057篇 |
2003年 | 10949篇 |
2002年 | 10330篇 |
2001年 | 10050篇 |
2000年 | 9450篇 |
1999年 | 9829篇 |
1998年 | 24704篇 |
1997年 | 17049篇 |
1996年 | 13135篇 |
1995年 | 9845篇 |
1994年 | 8628篇 |
1993年 | 8697篇 |
1992年 | 6327篇 |
1991年 | 5896篇 |
1990年 | 5921篇 |
1989年 | 5566篇 |
1988年 | 5279篇 |
1987年 | 4650篇 |
1986年 | 4556篇 |
1985年 | 5084篇 |
1984年 | 4690篇 |
1983年 | 4256篇 |
1982年 | 3861篇 |
1981年 | 3963篇 |
1980年 | 3660篇 |
1979年 | 3563篇 |
1978年 | 3541篇 |
1977年 | 3965篇 |
1976年 | 5042篇 |
1975年 | 3034篇 |
1974年 | 2826篇 |
1973年 | 2903篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
192.
O.N. Kondrateva G.E. Nikiforova A.V. Tyurin M.A. Ryumin V.M. Gurevich A.P. Kritskaya K.S. Gavrichev 《Ceramics International》2018,44(15):18103-18107
The heat capacity of ytterbium orthovanadate was first measured by adiabatic calorimetry in the temperature range T?=?12.28–344.06?K. No obvious anomalies were observed on the curve obtained. The values of standard thermodynamic functions in the temperature range T?=?0–400 K were calculated. Based on low-temperature calorimetry data obtained, previously published data on the high-temperature heat capacity of ytterbium orthovanadate were corrected. The anomalous contribution to heat capacity for YbVO4 was compared with the data known for YbPO4. 相似文献
193.
Similarities and differences between male and female novice designers on color‐concept associations for warnings,action required,and signs and equipment status messages 下载免费PDF全文
This research examined the male and female novice designers toward color associations for the concepts used for ‘warnings’, ‘action required’, and ‘signs and equipment status’ through a questionnaire‐based study. A total of 178 Hong Kong Chinese final year undergraduate design students (89 males and 89 females) participated in the study. The test used required the participants to indicate their choice of one of nine colors to associations with each of 38 concepts in a color‐concept table, so that any one color could be associated with any one of the concepts. For both male and female groups of novice designers, chi‐square tests revealed a strong color association for each concept tested in this study (P < .05). The results showed males and females agreed on some color‐concept association stereotypes which were therefore gender neutral. The male and female novice designers had the same color associations and similar levels of stereotype strengths for 21 concepts. The nine strongest and therefore most useful color‐concept association stereotypes for both male and female novice designers were: red‐danger, red‐fire, red‐hot, red‐stop, red‐emergency, red‐error, blue‐cold, blue‐male, and green‐exit. However, the male and female novice designers had different color association stereotypes for the standby (green vs. yellow), emergency exit (green vs. red), and toxic (purple vs. black) concepts, and the strengths of the 14 remaining associations for both groups were not at equivalent levels. Overall, it is anticipated that the findings of this study will act as a useful reference for novice designers and other design practitioners to optimize color coding in the design of ‘warnings’, ‘action required’, and ‘signs and equipment status’ messages. 相似文献
194.
S. A. Pul’nev A. I. Pryadko A. V. Chikiryaka V. I. Nikolaev 《Technical Physics Letters》2018,44(11):992-994
The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal. 相似文献
195.
The cracks in the workpiece specimens can reduce the fatigue life of any machine components. Since the residual stress has a considerable amount of influence on determining crack formation over the machined surface, it is very essential to analyze the residual stress developed in any machining process. However, it is a very tedious process to compute the residual stress over the machined surface. In the present study, an endeavor has been made to measure and analyze the residual stress of machined silicon steel as a workpiece using the EDM process with different energy distribution. The nano-indentation method was used to compute the residual stress produced over the machined surface. From the experimental results, it was found that the uniform energy distribution has produced higher compressive residual stress owing to the tiny and uniform spark energy distribution. It has also been observed that the tool electrode has a considerable amount of influence on determining development of residual stress in the EDM process. 相似文献
196.
S.K. Vimala Bharathi M. Maria Leena J.A. Moses C. Anandharamakrishnan 《International Journal of Food Science & Technology》2020,55(3):1238-1245
The usage of cling wraps is emerging as an easy and cost-effective approach to protect fresh-cut fruits and vegetables from dust, whilst improving visual appeal on retail counters. This study focused on developing an alternate, protein-based packaging material as a food grade cling wrap for food packaging applications. Zein-based cling wraps were produced, and their physical and mechanical characteristics were evaluated and compared with conventionally used chitosan biopolymer films and commercial synthetic polymer films. Antioxidant potential of the prepared films was studied, and the effectiveness of the developed films as anti-browning cling wraps was evaluated using studies conducted on fresh-cut apple slices at ambient conditions. Anti-browning effects were in par with polymeric counterparts; however, zein cling wraps could better prevent weight loss in apple slices. Zein-based films can be adopted as biodegradable food grade cling wraps as an alternative to chitosan and synthetic polymeric materials. 相似文献
197.
198.
199.
Amer Ibrahim Al-Omari Ibrahim M. Almanjahie Amal S. Hassan Heba F. Nagy 《计算机、材料和连续体(英文)》2020,64(2):835-857
In reliability analysis, the stress-strength model is often used to describe the life of
a component which has a random strength (X) and is subjected to a random stress (Y). In this
paper, we considered the problem of estimating the reliability R=P [Y<X] when the
distributions of both stress and strength are independent and follow exponentiated Pareto
distribution. The maximum likelihood estimator of the stress strength reliability is calculated
under simple random sample, ranked set sampling and median ranked set sampling methods.
Four different reliability estimators under median ranked set sampling are derived. Two
estimators are obtained when both strength and stress have an odd or an even set size. The
two other estimators are obtained when the strength has an odd size and the stress has an
even set size and vice versa. The performances of the suggested estimators are compared
with their competitors under simple random sample via a simulation study. The simulation
study revealed that the stress strength reliability estimates based on ranked set sampling and
median ranked set sampling are more efficient than their competitors via simple random
sample. In general, the stress strength reliability estimates based on median ranked set
sampling are smaller than the corresponding estimates under ranked set sampling and simple
random sample methods. 相似文献
200.
Low-Temperature Growth of the CdS Cubic Phase by Atomic-Layer Deposition on SiC/Si Hybrid Substrates
Kukushkin S. A. Osipov A. V. Romanychev A. I. Kasatkin I. A. Loshachenko A. S. 《Technical Physics Letters》2020,46(11):1049-1052
Technical Physics Letters - A new method for epitaxial growth of cadmium sulfide (CdS) films in the metastable cubic phase by atomic-layer deposition on silicon substrates with a buffer layer of... 相似文献