全文获取类型
收费全文 | 1196篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 64篇 |
金属工艺 | 19篇 |
机械仪表 | 10篇 |
建筑科学 | 9篇 |
能源动力 | 14篇 |
轻工业 | 44篇 |
无线电 | 34篇 |
一般工业技术 | 162篇 |
冶金工业 | 728篇 |
原子能技术 | 4篇 |
自动化技术 | 106篇 |
出版年
2022年 | 5篇 |
2021年 | 4篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 14篇 |
2013年 | 22篇 |
2012年 | 19篇 |
2011年 | 7篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 15篇 |
2007年 | 24篇 |
2006年 | 13篇 |
2005年 | 21篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 8篇 |
2001年 | 11篇 |
2000年 | 11篇 |
1999年 | 32篇 |
1998年 | 234篇 |
1997年 | 133篇 |
1996年 | 102篇 |
1995年 | 63篇 |
1994年 | 54篇 |
1993年 | 51篇 |
1992年 | 10篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 13篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 24篇 |
1976年 | 37篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1971年 | 6篇 |
排序方式: 共有1203条查询结果,搜索用时 0 毫秒
71.
Ch.S. Sastry Arun K. Pujari B.L. Deekshatulu C. Bhagvati 《Pattern recognition letters》2004,25(16):454-1855
The present work aims at proposing a new wavelet representation formula for rotation invariant feature extraction. The algorithm is a multilevel representation formula involving no wavelet decomposition in standard sense. Using the radial symmetry property, that comes inherently in the new representation formula, we generate the feature vectors that are shown to be rotation invariant. We show that, using a hybrid data mining technique, the algorithm can be used for rotation invariant content based image retrieval (CBIR). The proposed rotation invariant retrieval algorithm, suitable for both texture and nontexture images, avoids missing any relevant images but may retrieve some other images which are not very relevant. We show that the higher precision can however be achieved by pruning out irrelevant images. 相似文献
72.
Asymptotic tracking is studied for systems which are not regular, that is, the relative degree is not well defined. For these systems, the input–output linearizing control law has singularities. We propose a tracking control law which switches between an approximate tracking law (Hauser et al., IEEE Trans. Automat. Control 37 (3) (1992) 392–398) close to the singularities, and an exact tracking law away from the singularities, and we study the applicability of this law based on the behavior of the system’s zero dynamics at the switching boundary. As in Hauser et al. (IEEE Trans. Automat. Control 37 (3) (1992) 392–398), the ball and beam example is used to motivate the study. 相似文献
73.
74.
Sajid Husain G. S. R. Sastry N. Prasada Raju 《Journal of the American Oil Chemists' Society》1991,68(11):822-826
A simple method for quality assessment of heated oils and fats is described. The proposed method involves precise determination
of molecular weight averages (MWA)viz., the weight average molecular weight (
), the number average molecular weight (
) and the Z-average molecular weight (
) by high performance size exclusion chromatography (HPSEC) and their quantitative correlation to percent polar material obtained
by column chromatography (CC). Change in MWA on heat treatment of fourteen different edible oils and fats at 180° ± 2°C for
eight 8-hr days is studied. Relative standard deviations and regression coefficients of correlation between MWA and their
ratios (
, {
}, {
}, {
}, {
} and {
)vs percent polar material have been reported. Probable discard time was predicted for all the oils based on the above-mentioned
correlations and also from the percent of high molecular weight (H. Mwt) species formed. It was observed that the oils which
are generally recommended for coronary patients deteriorated faster. A possibility of extending this methodology to the frying
oils is suggested.
Part of the work was presented at “40th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy” at Georgia
World Congress Centre, USA, 1989.
IICT Communication No. 2630. 相似文献
75.
76.
Studies on Micellar Behavior of PEO‐PBO or PEO‐PBO‐PEO Copolymers,or Surface Active Amphiphilic Ionic Liquids in Aqueous Media and Exploration of the Micellar Solutions for Solubilization of Dexamethasone and its Delayed Release 下载免费PDF全文
Nandhibatla V. Sastry Dipak K. Singh Pooja A. Trivedi 《Journal of surfactants and detergents》2018,21(1):65-79
The aggregation behavior of a di‐ and tri‐block copolymers of type PEO‐PBO, PEO‐PBO‐PEO, surface‐active ionic liquid (SAIL) of type 4‐dodecyl‐4‐methylmorpholinium chloride [C12mmor][Cl], and 1‐dodecyl‐1‐methylpyrrolidinium chloride [C12mpyrr][Cl]) in water as well as in 10 mM of a poorly water soluble dexamethasone (dex) aqueous solution was studied by determining the critical micelle concentrations using drug solubilization, surface tension, and isothermal titration calorimetry (ITC) methods. ITC measurements were also made on solutions prepared by mixing the micellar aqueous solutions of copolymers and simple aqueous solutions of SAIL across the mole fractions at three different temperatures (298.15, 308.15, and 318.15 K). The thermodynamic parameters, namely Gibbs free energy (ΔGm), enthalpy (ΔHm), and entropy (ΔSm), of micellization were calculated, and it was observed that the negative ΔGm and positive ΔSm for the mixture solutions increase with the increase in mole fraction of SAIL. Otherwise, the micellization is reported to be a spontaneous and highly entropy‐driven process. The dex‐solubilized micellar solutions were mixed with agar to obtain standing gels. The gel samples were dry‐cast into thin films, and the release of dex from films by simple dilution was monitored by UV measurements. The drug release data was fitted to several mechanistic models, and it was inferred that the release mechanism for dex from thin films is non‐Fickian for mixtures and Fickian in copolymer or SAIL micellar aqueous solutions. The transport of dex is diffusion‐controlled with diffusivities of 5.8–12 × 10?11 m2 s?1 for copolymer micelles, 5–11 × 10?11 m2 s?1 for micelles of SAIL, and 3–14 × 10?11 m2 s?1 for the mixed micelles of copolymer and SAIL in aqueous media. 相似文献
77.
78.
S Makino DN Haylock T Dowse S Trimboli S Niutta LB To CA Juttner PJ Simmons 《Canadian Metallurgical Quarterly》1997,6(5):475-489
A major potential application for ex vivo culture of hematopoietic progenitor cells is the treatment of cytopenia following high-dose chemotherapy and hematopoietic transplantation. We have previously postulated that infusion of a sufficient number of neutrophil postprogenitor cells generated by ex vivo culture of CD34+ cells may be able to abrogate neutropenia. In this article, we describe further development of an efficient stromal-free, cytokine-dependent, static culture system for generation of these cells. Our previous studies indicated that maximal production of nucleated cells and myeloid progenitor cells from PB CD34+ cells occurred with multiple hematopoietic growth factor (HGF), notably the 6-HGF combination of interleukin (IL)-1, IL-3, IL-6, granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage-CSF (GM-CSF), and stem cell factor (SCF). In the present study, we determine the contribution of each of these 6 HGF in generation of neutrophilic precursors. SCF, G-CSF, and IL-3 were found to be the most important HGF for production of neutrophilic cells. The 4-HGF combination of IL-3, IL-6, G-CSF, and SCF was optimized by performing dose-response experiments and shown to be as potent as 6 HGF for production of nascent CFU-GM and neutrophilic precursors. 相似文献
79.
DN Dunham 《Canadian Metallurgical Quarterly》1997,27(3):171-182
Characterization of flow properties of an artificial ventricle may aid development of designs to minimize thrombosis. Techniques for determining two such flow properties, viz. ventricular clearance rate and ejection fraction, are compared and validated here for polyurethane and silicone rubber ventricles operated in a mock circulatory loop at various stroke volumes and pulse rates. Ventricular clearance rats were measured both by clinical radionuclide tracer techniques and by an optical tracer method. Ejection fractions were measured by radionuclide imaging and validated by direct measurements of flow rate and ventricular volume. Results from the two methods for ventricular clearance are in close agreement. The optical tracer method is superior in spatial resolution, convenience and economy, but the radionuclide tracer method for ejection fraction gives excellent agreement with the absolute measurements. 相似文献
80.
U Herrlinger CM Kramm KM Johnston DN Louis D Finkelstein G Reznikoff G Dranoff XO Breakefield JS Yu 《Canadian Metallurgical Quarterly》1997,4(6):345-352
Within the pituitary, folliculostellate (FS) cells are considered to regulate the intercellular communication between endocrine cells by paracrine mechanisms. One of the possible paracrine factors involved, could be interleukin-6 (IL-6) which is produced by these cells. Since IL-6 has been shown to be a growth factor of pituitary cells, we have determined whether IL-6 can also influence FS cell proliferation. To test this, a FS cell-like mouse pituitary cell line (TtT/GF cells) was used that exhibits most characteristics of normal FS cells. Under serum-free conditions the proliferation of TtT/GF cells is critically dependent on the initial seeding density: cells seeded at low density do not grow at all whereas cells seeded at high density proliferate with maximal doubling times of 34 hrs. Mouse IL-6 (mIL-6) stimulated only low density cell cultures in a dose and time dependent manner. For cells seeded at high density, exogenously added IL-6 may have failed to stimulate growth because of endogenously produced mIL-6. Conditioned medium from TtT/GF cells, in which mIL-6 concentrations up to 1017 pg/ml were measured, stimulated the proliferation of TtT/GF cells, indicating an autocrine growth stimulatory mechanism. A neutralizing mIL-6 antibody partially suppressed the growth of TtT/GF cells seeded at high density and partially reduced the growth stimulatory activity of TtT/GF conditioned medium. Thus, IL-6 is one but not the only factor that is involved in the autocrine growth stimulatory loop. The relevance of this mechanism for normal FS cells and its physiological consequence needs to be elucidated. 相似文献