全文获取类型
收费全文 | 8506篇 |
免费 | 395篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 171篇 |
综合类 | 23篇 |
化学工业 | 1643篇 |
金属工艺 | 235篇 |
机械仪表 | 445篇 |
建筑科学 | 193篇 |
矿业工程 | 5篇 |
能源动力 | 330篇 |
轻工业 | 633篇 |
水利工程 | 46篇 |
石油天然气 | 21篇 |
武器工业 | 1篇 |
无线电 | 1588篇 |
一般工业技术 | 1488篇 |
冶金工业 | 796篇 |
原子能技术 | 94篇 |
自动化技术 | 1204篇 |
出版年
2023年 | 64篇 |
2022年 | 90篇 |
2021年 | 133篇 |
2020年 | 115篇 |
2019年 | 137篇 |
2018年 | 177篇 |
2017年 | 163篇 |
2016年 | 232篇 |
2015年 | 200篇 |
2014年 | 323篇 |
2013年 | 606篇 |
2012年 | 471篇 |
2011年 | 515篇 |
2010年 | 395篇 |
2009年 | 472篇 |
2008年 | 405篇 |
2007年 | 365篇 |
2006年 | 361篇 |
2005年 | 307篇 |
2004年 | 291篇 |
2003年 | 277篇 |
2002年 | 294篇 |
2001年 | 221篇 |
2000年 | 201篇 |
1999年 | 197篇 |
1998年 | 415篇 |
1997年 | 249篇 |
1996年 | 182篇 |
1995年 | 149篇 |
1994年 | 124篇 |
1993年 | 130篇 |
1992年 | 70篇 |
1991年 | 80篇 |
1990年 | 66篇 |
1989年 | 60篇 |
1988年 | 42篇 |
1987年 | 46篇 |
1986年 | 40篇 |
1985年 | 33篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 15篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 16篇 |
1977年 | 17篇 |
1976年 | 23篇 |
1973年 | 8篇 |
1971年 | 6篇 |
排序方式: 共有8916条查询结果,搜索用时 0 毫秒
91.
The dynamical behavior of polymers with molecular weight distribution is analyzed from the standpoint of reptation and tube
renewal. In a binary blend where the entanglements between longer chains are prominent, the shorter chain relaxes only by
reptation, whereas the longer chain shows more complex behavior, i.e., reptation in the original tube, short-range tube renewal
causing the tube enlargement, and thereafter reptation again in the expanded tube. Dynamic moduli data from literature are
used for determining the compositional dependence of the relaxation times. Also on the basis of the relaxation mechanism considered
here, the critical composition due to the onset of entanglements between different longer chains is proposed as a function
of their component molecular weighl ratio. 相似文献
92.
Summary A confined stiff chain model is suggested for the prediction of the rotational diffusion coefficient of a rigid rodlike polymer with a slight flexibility above the region of dilute solution (c1/L3). It shows a fairly good agreement with the experimental data of various polymers. Among them, PBLG and PBT with more rigidity are more consistent with the model when the log-jamming effect is considered. The predicted rotational diffusivity shows approximately the inverse seventh-power of length, which is less than 9 of Doi-Edwards tube model, but larger than the experimental value 5.7 of M-virus, while it shows the inverse power of concentration is a little larger than the value 2 of tube model except for the rodlike virus M-13. 相似文献
93.
Polypropylene (PP)/layered silicate nanocomposites were prepared via simple melt mixing of three components, PP, layered silicates modified with octadecylamine (C18-MMT) and antioxidant, to investigate the role of antioxidant. TEM and X-ray scattering results confirmed the intercalated state of silicates in PP/layered silicate nanocomposites with antioxidant. In rheological and mechanical study, the nanocomposites with antioxidant showed higher properties than those of the unfilled PP. The nanocomposite with 5 wt% C18-MMT and 0.5 phr antioxidant exhibited about 1.4 times higher tensile modulus and 1.3 times higher storage modulus than the unfilled PP. However, PP/C18-MMT without antioxidant showed lower rheological values owing to the thermal decomposition of PP and the poor compatibility between PP and C18-MMT. It could be concluded that antioxidants played an important role in enhancing the compatibility between PP and C18-MMT. According to the real time X-ray diffraction, the nanocomposite showed the weak ordering of PP crystals than the unfilled PP in the load-extension plateau region of elongation. 相似文献
94.
Kim-Choy Chung 《Behaviour & Information Technology》2014,33(7):743-756
This study investigates perceived risk and trust in relationship to the Diffusion of Innovation Theory [Rogers, E.M., 1962. Diffusion of innovations. Glencoe, IL: The Free Press; 1983. Diffusion of innovations. 3rd ed. New York: The Free Press] from a cultural perspective to understand the determinants of behavioural intent to adopt mobile commerce among the Y Generation in Kazakhstan. Surveys from 345 university-level students and subsequent structural equation modelling revealed perceived risk, trustworthiness and Rogers’ five innovation characteristics are important determinants. Perceived risk and trustworthiness are important determinants because of the high uncertainty avoidance characteristics of the Kazakh society. This study advances theory regarding culture- and generation-based characteristics to transition economies by verifying theoretical proposition regarding the behavioural intent towards mobile commerce adoption, resulting in a greater understanding of mobile commerce adoption among the Y Generation in transition economies. Marketing implications are discussed. 相似文献
95.
O. K. Chung Y. Pomeranz K. F. Finney M. P. Shogren 《Journal of the American Oil Chemists' Society》1978,55(9):635-641
Petroleum ether (PE) extracted 1.00% total free lipids (0.70% nonpolar and 0.30% polar) and 2-propanol (PrOH) extracted 1.36%
total free and bound lipids (0.73% nonpolar and 0.63% polar) from wheat flour; the lipid fractions were characterized by thin
layer chromatography. PE- or PrOH-defatted flours were baked after reconstitution with total, nonpolar, or polar wheat flour
lipids; or with equivalent amounts of nonionic sucrose monopalmitate (SMP), ethoxylated monoglycerides (EMG) — each with a
hydrophile-lipophile balance (HLB) of 14.0 or anionic sodium stearoyl-2-lactylate (SSL) — with an HLB value of 9.0. Defatted
flours supplemented with surfactants alone or in combination with wheat flour lipids were used in bread with no-shortening
and with 3%-shortening. The importance of the polar flour lipids in breadmaking was verified. The lipids in wheat flour were
essential for maximizing the beneficial effects of shortening on breadmaking quality. Nonionic SMP or EMG completely replaced
both PE-extractable wheat flour free total lipids ( or their non-polar or polar fractions) and 3% shortening; nonionic surfactants
with high HLB were better than the anionic SSL for replacing free flour lipids. No surfactant completely replaced unfractionated
PrOH-extracted lipids (free + bound) and shortening or total polar flour lipids (free + bound). All surfactants, especially
anionic SSL, added with PrOH-extracted polar lipids improved the overall bread-making properties of the PrOH-defatted flour
both in the absence and in the presence of shortening.
Presented at the AOCS Meeting, New York, May 1977 相似文献
96.
Microstructure and Phase Stability of Yttria-Doped Tetragonal Zirconia Polycrystals Heat Treated in Nitrogen Atmosphere 总被引:2,自引:0,他引:2
Tai-Joo Chung Huesup Song Gyeung-Ho Kim Doh-Yeon Kim 《Journal of the American Ceramic Society》1997,80(10):2607-2612
The low-temperature degradation of zirconia (ZrO2 ) that was doped with 3 mol% yttria (Y2 O3 ) (3Y-TZP) was prevented by the heat treatment of sintered specimens in nitrogen. The heat treatment of sintered specimens resulted in a surface layer that was stabilized by nitrogen ions, whereas the interior was only slightly affected by the heat treatment. X-ray diffractometry and transmission electron microscopy analyses revealed that the stabilized surface layer consisted of cubic grains with tetragonal precipitates. Although the presence of the surface layer decreased the strength of the sintered 3Y-TZP, the strength of nitrified specimens was maintained when low-temperature annealing was applied. 相似文献
97.
Hyun Jin Chung Suk Jin Chung Min Ku Jeon Seong Ihl Woo 《Korean Journal of Chemical Engineering》2006,23(2):329-332
The ((Bi3.5La0.5)Ti3O12(BLT) thin-films used in this study were fabricated on a Pt(111)/SiO2/Si(100) substrate by a Liquid Source Misted Chemical Deposition (LSMCD) technique. X-ray diffraction patterns showed that
the BLT films were crystallized and no other phases were observed when annealed above 650 ‡C. Grain size and remnant polarizations
increased with increase in the annealing temperature, while leakage current densities decreased. The remnant polarizations
(Pr) increased from 2.0 to 4.8 and 19.0 μC/cm2 with increase in the annealing temperature from 650 to 700 and 750 ‡C, respectively.
The BLT films annealed at 700 ‡C in O2 showed a good fatigue resistance of reduced polarization by 10% after 109 switching cycles when 9 V of bipolar voltage was applied at a frequency of 40 kHz. 相似文献
98.
A personalized service in the ubiquitous environment is to provide services or items, which reflect personal tastes, attitudes, and contexts. It is impossible to reflect the context information generated in u-healthcare environments due to the existing recommendation system performing the recommendation using the information directly input by users and application usage record only. This study develops a context-aware model using the context information provided by the context information model. The study applies it to the extraction of the missing value in a collaborative filtering process. The context-aware model reflects the information that selects items by users according to the appropriate context using the C-HMM and provides it to users. The solution of the missing value in the preference significantly affects the recommendation accuracy in a preference based item supply method. Thus, this study developed a new collaborative filtering for ubiquitous environments by reflecting the missing preference value and reflecting it to the collaborative filtering using the context-aware model. Also, the validity of this method will be evaluated by applying it to menu services in u-healthcare services. 相似文献
99.
Ashwin Kumar Vutha Benyamin Davaji Chung Hoon Lee Glenn M. Walker 《Microfluidics and nanofluidics》2014,17(5):871-878
We demonstrate the use of heat to count microscopic particles. A thermal particle detector (TPD) was fabricated by combining a 500-nm-thick silicon nitride membrane containing a thin-film resistive temperature detector with a silicone elastomer microchannel. Particles with diameters of 90 and 200 μm created relative temperature changes of 0.11 and ?0.44 K, respectively, as they flowed by the sensor. A first-order lumped thermal model was developed to predict the temperature changes. Multiple particles were counted in series to demonstrate the utility of the TPD as a particle counter. 相似文献
100.
Gil-Young Song Youngjoon Cheon Kihwang Lee Heuiseok Lim Kyung-Yong Chung Hae-Chang Rim 《Personal and Ubiquitous Computing》2014,18(6):1387-1403
As various forms of social media are spreading, we often witness that an idea of an individual user drives macroscopic changes. From the perspectives of product development and marketing, the opinions left by potential consumers in online social network can generate big ripple effects. This study analyzes the user opinions in online space to grasp preferences toward various products psychologically categorized by users. We also suggest an aspect of the market mentally configured by users using network modeling while following the framework of economic sociology. Existing analyses on online market place are mainly dealing with structural issues such as inter-actor relationships and status measurement. This study, however, analyzes complex preferences regarding diverse products and brands and derives a new model for inter-market connections. We expect that our study will provide important consequences on digital marketing and community design of corporations planning word of mouth effect in online space. 相似文献