全文获取类型
收费全文 | 660篇 |
免费 | 23篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 184篇 |
金属工艺 | 16篇 |
机械仪表 | 14篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 48篇 |
轻工业 | 57篇 |
水利工程 | 5篇 |
无线电 | 64篇 |
一般工业技术 | 149篇 |
冶金工业 | 19篇 |
原子能技术 | 2篇 |
自动化技术 | 102篇 |
出版年
2024年 | 2篇 |
2023年 | 18篇 |
2022年 | 38篇 |
2021年 | 44篇 |
2020年 | 45篇 |
2019年 | 25篇 |
2018年 | 34篇 |
2017年 | 39篇 |
2016年 | 28篇 |
2015年 | 17篇 |
2014年 | 29篇 |
2013年 | 52篇 |
2012年 | 28篇 |
2011年 | 31篇 |
2010年 | 28篇 |
2009年 | 41篇 |
2008年 | 27篇 |
2007年 | 24篇 |
2006年 | 16篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 10篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有687条查询结果,搜索用时 15 毫秒
81.
In the present study, Chlamydomonas sp. MACC-216 was used to investigate total nitrate removal in TAP medium with sodium nitrate as the sole nitrogen source under several light conditions made up of permuted combinations of three light colors (referred to as blue, red, and white light) and three light intensities (50 µmol m−2 s−1, 100 µmol m−2 s−1, and 250 µmol m−2 s−1). It was observed that nitrate removal efficiency is influenced by light color as well as light intensity. Additionally, Chlamydomonas sp. MACC-216 was cultivated in synthetic wastewater under four light conditions, namely, Blue 250, Blue 125 + Red 125, Red 250, and White 250, where it showed the highest nitrate removal efficiency and nitrate reductase activity under the Blue 125 + Red 125 light condition. To observe the impact of light color on the nitrate removal capacity of Chlamydomonas sp. MACC-216, the expression of five genes participating in nitrate transport and reduction (NRT1, NRT2.1, NRT2.2, NIA, and MCP) was also analyzed; these genes showed the highest expression under the Blue 125 + Red 125 light condition. Based on the above-mentioned findings, the blue + red light combination emerged as a promising light combination for nitrate removal. Hence, our study suggests the importance of the blue + red light combination together with high light intensity, as the optimal light condition for nitrate removal from synthetic wastewater in comparison to other monochromatic lights with high light intensity. 相似文献
82.
Blends of 50/50 natural rubber (NR) and styrene-butadiene rubber (SBR) are vulcanized using several conventional and semi-EV systems. The cure characteristics and vulcanizate properties are compared. The quantity and quality of crosslinks in each case are deciphered by chemical probes to correlated them with the vulcanizate properties. 相似文献
83.
It has been recognized that as the function responsible for converting design specifications into manufacturing instructions, Process Planning has a key role to play in the integration of the Design and Manufacturing functions. In this paper, we describe the development of a robust interface between a Process Planning system and a CAD system using the new and emerging PDES standard for product data definition. The work is based on the concept of Design by Features whereby a part design is represented in terms of the constituent features. The relevant features data is then extracted from the design database and used as input to the process planning system. On the basis of this input, a detailed process plan as well as NC part program are generated by the system and these can be used in physically manufacturing the part. 相似文献
84.
Para-phenylenediamine (PD) was chemically attached to depolymerized natural rubber by a photochemical reaction. The rubber bound PD was characterized by TLC, 1H-NMR, IR, and TGA. The efficiency and permanence of the bound PD were compared with conventional antioxidants in NBR vulcanizates. The rubber bound PD was found to be less volatile and more resistant to water and oil extraction. The vulcanizates showed improved aging resistance in comparison to vulcanizates containing conventional antioxidants. The liquid rubber bound antioxidant reduces the amount of plasticizer required for compounding. © 1995 John Wiley & Sons, Inc. 相似文献
85.
The electron donor properties of Nd2O3 activated at 300, 500 and 800°C were investigated through studies on the adsorption of electron acceptors of various electron affinities — 7, 7, 8, 8-tetracyanoquinodimethane (2.84 eV), 2, 3, 5, 6-tetrachloro-1, 4-benzoquinone (2.40 eV), p-dinitrobenzene (1.77 eV), and m-dinitrobenzene (1.26 eV) in solvents acetonitrile and 1, 4-dioxan. The extent of electron transfer during adsorption has been found from magnetic measurements and electronic spectral data. The corresponding data on mixed oxides of neodymium and aluminium are reported for various compositions. The acid-base properties of catalysts were also determined using a set of Hammett indicators. 相似文献
86.
A sequential procedure is developed in order to construct a confidence interval of “fixed-width and preassigned coverage probability” for the inverse of the coefficient of variation of a normal population. The proposed sequential procedure is proved to be “asymptotically efficient and consistent” in the sense of Chow and Robbins ([1]: Ann. Math. Statist. 36, 457–462 (1965)). Asymptotic distribution of the stopping time is derived. 相似文献
87.
Kalanithi Nesaretnam Teoh Hoon Koon Kanga Rani Selvaduray Richard S. Bruno Emily Ho 《European Journal of Lipid Science and Technology》2008,110(1):23-31
Previous studies have shown that tocotrienols are powerful growth inhibitors and potent inducers of apoptosis in human breast cancer cells. The objective of the current study was to examine effects of tocotrienols on apoptotic signals in androgen‐independent PC‐3 human prostate cancer cells. We investigated the effects of the tocotrienol‐rich fraction (TRF) from palm oil, α‐tocopherol (αT), α‐tocotrienol (αT3), γ‐tocotrienol (γT3) and δ‐tocotrienol (δT3) on PC‐3 cell growth. TRF inhibited PC‐3 growth with a nonlinear response, with complete growth suppression at 10 µg/mL. δT3 and γT3 showed complete cell inhibition at 8 µg/mL whilst αT had no effect. δT3 and γT3 showed the most promise in the cell growth assays, and all subsequent experiments were performed with δT3, TRF and αT. TRF and δT3 at 8 µg/mL induced apoptosis in PC‐3 cells after 48 h of treatment. In addition, TRF and δT3 treatments were able to affect the cell cycle, with accumulation in the S phase, G2 phase block and increases in SubG1 by 72 h. We then proceeded to investigate the expression levels of Fas receptor and Fas ligand, caspase 8, caspase 3 and bax in PC‐3 cells following treatment with tocotrienols using real‐time PCR and Western blot methods. TRF and δT3 at 8 µg/mL increased Fas ligand expression levels by 368 and 456%, respectively, after 24 h and Fas receptor expression levels by 210% and 356%, respectively, after 48 h. TRF‐ and δT3‐treated PC‐3 cells overexpressed caspase 8 and bax protein after 24 h, and caspase 3 after 48 h. In conclusion, tocotrienols are able to induce apoptosis and cell cycle arrest in PC‐3 cells, with increased expression of Fas receptor, Fas ligand, caspase 8, caspase 3 and bax, suggesting a potential role in chemoprevention of prostate cancer. 相似文献
88.
The present work undertakes the preparation and physico-chemical characterisation of iron promoted sulphated zirconia (SZ) with different amounts of iron loading and their application to Friedel–Crafts benzoylation of benzene, toluene and xylene under different experimental conditions. XRD and laser Raman techniques reveal the stabilisation of the tetragonal phase of zirconia and the existence of iron in highly dispersed form as Fe2O3 on the catalyst surface. The surface acidic properties were determined by ammonia temperature programmed desorption (TPD) and perylene adsorption. The results were supported by the TGA studies after adsorption of pyridine and 2,6-dimethylpyridine (2,6-DMP). Strong Lewis acid sites on the surface, which are evident from TPD and perylene adsorption studies, explain the high catalytic activity of the systems towards benzoylation. The experimental results provide evidence for the truly heterogeneous nature of the reaction. The studies also establish the resistance to deactivation in the metal incorporated sulphated systems. 相似文献
89.
Yann Civale Guglielmo Vastola Lis K. Nanver Rani Mary-Joy Jae-Ryoung Kim 《Journal of Electronic Materials》2009,38(10):2052-2062
Mechanisms governing the aluminum-mediated solid-phase epitaxy of Si on patterned crystalline Si substrates have been identified
by studying the deposited material as a function of growth conditions when varying parameters such as temperature, growth
time, and layer-stack properties. Early growth stages can be discerned as first formation of “free” Si at the Al/α-Si interface,
then diffusion of Si along the Al grain boundaries, nucleation at the Si substrate surface, nuclei rearrangement, and finally
crystal growth. The acquired understanding is applied to control the selectivity and completeness of single-crystal growth
in various sizes of contact windows to the Si substrate. 相似文献
90.
The dielectric response in the microwave field of polyaniline prepared at different temperatures and using different inorganic and organic dopants was studied. Chemical oxidative polymerization of aniline was done at low temperature (0–5°C), at room temperature, and at high (60°C) temperature using different inorganic dopants like HCl, HNO3, H2SO4, HClO4, etc. Polyaniline was also prepared with different organic dopants like camphor sulfonic acid, Toluene sulfonic acid, and Naphthalene sulfonic acid. All polymers formed were characterized using IR, TGA, DSC, and SEM, etc. The dielectric responses of all polymers are studied using cavity perturbation technique in the microwave field. The studies indicates that the polyaniline prepared with perchloric acid at room temperature shows higher conductivity and absorption coefficient compared with all other samples. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献