全文获取类型
收费全文 | 1276篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 18篇 |
化学工业 | 157篇 |
金属工艺 | 7篇 |
机械仪表 | 10篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 60篇 |
轻工业 | 20篇 |
水利工程 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 180篇 |
冶金工业 | 675篇 |
原子能技术 | 1篇 |
自动化技术 | 49篇 |
出版年
2023年 | 5篇 |
2021年 | 10篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 9篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 43篇 |
2012年 | 17篇 |
2011年 | 18篇 |
2010年 | 14篇 |
2009年 | 16篇 |
2008年 | 23篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 26篇 |
1998年 | 175篇 |
1997年 | 124篇 |
1996年 | 77篇 |
1995年 | 61篇 |
1994年 | 43篇 |
1993年 | 56篇 |
1992年 | 20篇 |
1991年 | 24篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 10篇 |
1987年 | 25篇 |
1986年 | 27篇 |
1985年 | 23篇 |
1984年 | 16篇 |
1983年 | 16篇 |
1982年 | 18篇 |
1981年 | 24篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 26篇 |
1976年 | 69篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1972年 | 5篇 |
排序方式: 共有1286条查询结果,搜索用时 46 毫秒
31.
A cigarette which heats rather than burns tobacco (Premier) was introduced in 1988, but was unacceptable due to unpleasant taste and low nicotine intake. We examined availability of nicotine from a new version (Eclipse), in the same four subjects as our earlier Premier study. Average blood nicotine boosts of 23.7 and 17.8 ng/ml were obtained from smoking a first and second Eclipse. This substantially exceeds intake from Premier (boost 13 ng/ml) and that obtained by heavy smokers from conventional brands (boost 12-15 ng/ml). Eclipse (or similar product) may be the best option for averting Peto's dire warnings of rising millions of annual smoking deaths in the 2020s, and its potential for large-scale, long-term switching warrants further study. 相似文献
32.
1. Calcium disodium ethylenediaminetetraacetate (CaNa2 EDTA) and meso-2,3-dimercaptosuccinic acid (DMSA) individually and in permutation-combination in various doses (0.1, 0.2 and 0.4 mmol/kg bodyweight) were investigated for their efficacy to mobilize lead from vital tissues into urine and faeces and to restore the lead-sensitive biochemical parameters in lead pre-exposed rats with a view to develop the most acceptable treatment regimen for lead poisoning with a minimal loss of endogenous essential elements. 2. The combined therapy was more effective than a single chelator treatment. 3. The combination of 0.2 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA caused a lower depletion of zinc, calcium and iron but possessed almost equal capability to that of 0.4 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA to produce urinary as well as faecal excretion of lead, to reduce the tissue burden of lead, including that of the brain, and to reverse lead-induced biochemical alterations. 4. The combination of 0.2 mmol/kg CaNa2EDTA + 0.4 mmol/kg DMSA has shown a definite improvement over previously reported combinations in terms of removal of lead from tissues, particularly the brain, restoration of urinary delta-aminolevulinic acid levels and a decrease in the loss of body zinc and is, therefore, recommended for the treatment of lead intoxication. 相似文献
33.
VK Boppana 《Canadian Metallurgical Quarterly》1995,692(1-2):195-202
A highly sensitive and selective high-performance liquid chromatographic method was developed for the determination of granisetron and its active metabolite, 7-hydroxygranisetron (7OH-G) in human plasma. Granisetron is a selective 5-hydroxytryptamine receptor antagonist used in the treatment of cytotoxic drug-induced emesis. The method involves isolation of granisetron, 7OH-G and the internal standards from plasma by solid-phase extraction prior to reversed-phase ion-pair chromatographic separation on an octyl silica column with subsequent quantification of analytes simultaneously either with electrochemical (7OH-G) or fluorescence (granisetron) detectors which are placed in series. The recovery of granisetron and 7OH-G from human plasma was quantitative. Using 1 ml of plasma, the limits of quantification for granisetron and 7OH-G were 0.1 and 0.25 ng/ml, respectively. Linear responses in analyte/internal standard peak-area ratios were observed for analyte concentrations ranging from 0.1 to 50 ng/ml plasma. Precision and accuracy were within 13% across the calibration range for both granisetron and 7OH-G. The method was sufficiently sensitive, accurate and precise to support pharmacokinetic studies for granisetron and 7OH-G, in both normal and patient populations. 相似文献
34.
Mixtures of CaCO3SiO2 in 21 molar ratio were subjected separated to thermal analysis with varying concentration of Cr2O3 (0.1 to 5%) as dopant. The activation energy (E
a) and enthalpy (H) shows a decreasing trend with 0.1 to 1% Cr2O3 and attains a minimum value with 1% dopant. 0.1 to 0.5% Cr2O3 helps in the formation of and C2S, (Cement Chemistry notations, C = CaO, S = SiO2) phases at 1400° C and above but 1% Cr2O3 stabilizes -C2S phase along with a little free lime and CaCrO4. A small quantity of CaCrO4, Cr2SiO2 and -C2S are also formed along with the major phases with 5% Cr2O3 indicating that Cr3+ can substitute both Ca2+ and Si4+ ions in the C2S lattice. 相似文献
35.
Quantification of response time in poly(vinyl alcohol)–metal complex thermochromic polymeric systems
Thermochromic poly(vinyl alcohol) (PVA)‐based material was synthesized and an extensive study of its thermochromic behavior with respect to response time was carried out. It was observed that it is possible to manipulate the response time by keeping control over chemical and physical parameters. The response time, which is the most important property of a smart material, has in this case been found to be very much influenced by rate of heat transfer into the material. Different compositions of the thermochromic material and their corresponding response time with respect to rate of heat transfer were studied and correlated. First, a theoretical equation was derived and later on it was experimentally verified to quantify the response time in PVA–metal complex‐based thermochromic systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4832–4834, 2006 相似文献
36.
37.
38.
Nanocomposites of epoxy resin with montmorillonite clay were synthesized by swelling of different proportions of the clay in a diglycidyl ether of bisphenol‐A followed by in situ polymerization with aromatic diamine as a curing agent. The montmorillonite was modified with octadecylamine and made organophilic. The organoclay was found to be intercalated easily by incorporation of the epoxy precursor and the clay galleries were simultaneously expanded. However, Na‐montmorillonite clay could not be intercalated during the mixing or through the curing process. Curing temperature was found to provide a balance between the reaction rate of the epoxy precursor and the diffusion rate of the curing agent into the clay galleries. The cure kinetics were studied by differential scanning calorimetry. The exfoliation behavior of the organoclay system was investigated by X‐ray diffraction. Thermogravimetric analysis was used to determine the thermal stability, which was correlated with the ionic exchange between the organic species and the silicate layers. The morphology of the nanocomposites was evaluated by scanning electron microscopy. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2201–2210, 2004 相似文献
39.
A novel ether connected epoxy star like polymer was synthesized by selective reaction of water soluble polyhydroxy fullerene (fullerenol) with a commercial grade cycloaliphatic epoxy resin (CY-230, Ciba Geigy) in heterogeneous medium at ambient alkaline condition using tetrabutylammonium hydroxide as phase transfer catalyst. The reaction went well in such conditions and the hydroxy groups of fullerenol underwent selective nucleophilic addition reaction with polar carbonyl groups of the epoxy resin with the formation of a hemiketal. The progress of the reaction was monitored by FTIR analysis of the product formed. The disappearance of characteristic FTIR bands of fullerenol (at 1593.2, 1381.2, and 1068 cm−1) and the typical carbonyl peak (at 1725 cm−1) of parent epoxy resin and also changes of broad hydroxy peak (at 3431 cm−1) of fullerenol into a sharp peak (at 3396.6 cm−1, indicating reduced hydrophilicity) in the reaction product clearly demonstrated the chemical attachment of the epoxy units to the fullerene core. Multiple epoxy units (about 8-10) were attached to fullerene core. Non-reactivity of fullerenol towards DGEBA epoxy resin (LY 556 Ciba Geigy) in similar conditions further supports our result. The thermal properties of the product were influenced by the presence of fullerenol and exhibits higher thermal stability compared to parent epoxy. A probable reaction mechanism for the reaction has also been discussed. 相似文献
40.
Crystallization kinetics of the Se80–x
Sb
x
Te20 (0x9) alloys have been studied using differential scanning calorimetry. The activation energies for the glass transition and that for crystallization have been determined from the heating rate dependence of the glass transition temperature and the peak crystallization temperature. The results have been analysed using the modified Kissinger's and Matusita's equations for the non-isothermal crystallization of materials. The variation of glass transition temperature with composition suggests that a small amount of Sb ( 4 at %) leads to an increase in the chain length of Se-Te, whereas further increase in Sb atomic per cent increases the number of Se-Te chains in the alloys. 相似文献