全文获取类型
收费全文 | 1087篇 |
免费 | 67篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 283篇 |
金属工艺 | 27篇 |
机械仪表 | 29篇 |
建筑科学 | 36篇 |
矿业工程 | 4篇 |
能源动力 | 29篇 |
轻工业 | 235篇 |
水利工程 | 8篇 |
石油天然气 | 14篇 |
无线电 | 34篇 |
一般工业技术 | 204篇 |
冶金工业 | 123篇 |
原子能技术 | 12篇 |
自动化技术 | 109篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 27篇 |
2021年 | 53篇 |
2020年 | 29篇 |
2019年 | 38篇 |
2018年 | 42篇 |
2017年 | 30篇 |
2016年 | 47篇 |
2015年 | 30篇 |
2014年 | 38篇 |
2013年 | 84篇 |
2012年 | 72篇 |
2011年 | 76篇 |
2010年 | 54篇 |
2009年 | 55篇 |
2008年 | 50篇 |
2007年 | 50篇 |
2006年 | 47篇 |
2005年 | 20篇 |
2004年 | 16篇 |
2003年 | 29篇 |
2002年 | 24篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 43篇 |
1997年 | 33篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 2篇 |
1991年 | 9篇 |
1989年 | 1篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有1155条查询结果,搜索用时 31 毫秒
11.
In the present work, coal co-processing with sugar cane bagasse oil was studied for the first time. Sugar cane bagasse was chosen due to its great offer, since it is a residue in the process of a large project named PROALCOOL aiming the producing ethanolfrom sugarcane. In addition, the liquefaction of sugar cane bagasse with monoethanolamine was already developed in our laboratory showing good results. Four coal samples were studied. The yields of the total conversion and the oil productions were obtained in order to evaluate the efficiency of the liquefaction process studied. 相似文献
12.
13.
Iskander M.F. Smith R.L. Andrade A.O.M. Kimrey H. Jr. Wal L.M. 《Microwave Theory and Techniques》1994,42(5):793-800
Microwave sintering of ceramics in multimode cavities, particularly the use of picket-fence arrangements, has recently received considerable attention. Various types of ceramics have been successfully sintered and, in some cases, a desirable and unique “microwave effect” has been observed. At present, various aspects of the sintering profess such as preparation of sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide an improved understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process. In this paper, we utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a ceramic loading plate placed at the base of the cavity 相似文献
14.
A Poblet S Andrade M Scagliola C Vodopivez A Curtosi A Pucci J Marcovecchio 《Canadian Metallurgical Quarterly》1997,207(2-3):187-194
Trace-metal contents were recorded for the epilithic antarctic lichens Usnea aurantiacoatra and U. antartica, sampled close to the Argentine scientific station 'Jubany' on '25 de Mayo' (King George) Island, in the Southern Shetland Archipelago (Antarctica). The corresponding heavy-metal levels have been measured through atomic absorption spectrophotometry, following internationally accepted analytical methods. The results obtained support the hypothesis that an atmospheric circulation of trace metals exists on the assessed area, and the activities developed at the different scientific stations located on this island would be a potential source of heavy metals to the evaluated environment. The geographical distribution of trace metals atmospherically transported in the area close to 'Jubany Station' was studied through the corresponding metal contents of the assessed lichens. Finally, the suitability of both analyzed lichen species, Usnea aurantiacoatra and U. antartica, as biological indicators for quantitative monitoring of airborne metals for this antarctic environment was recognized. 相似文献
15.
Morphological analysis of poly(o-methoxyaniline) thin-films deposited by spin coating technique 总被引:1,自引:0,他引:1
John Paul H. Lima Adnei M. de Andrade 《Journal of Materials Science: Materials in Electronics》2006,17(8):593-596
Morphological study of conducting polymer thin films obtained by spin coating is reported. Poly(o-methoxyaniline) films were deposited onto glass substrates and analyzed by profilometry and atomic force microscopy (AFM).
It is shown that final thickness is correlated by a power law with spin speed with a solution concentration varying coefficient
and that surface roughness decreases with increasing spin speed. 相似文献
16.
Hishinuma Earl S.; Else 'Iwalani R. N.; Chang Janice Y.; Goebert Deborah A.; Nishimura Stephanie T.; Choi-Misailidis Soojean; Andrade Naleen N. 《Canadian Metallurgical Quarterly》2006,21(3):286
School psychologists are generally not provided with the knowledge and skills to address both educational and psychosocial issues of Asian American and Pacific Islander students. The present study is the first of its kind in examining 36 independent (i.e., demographic, social, cultural, psychological) variables in association with four school outcomes (i.e., grade point average, absences, suspensions, and school infractions) with a large sample of Caucasian, Filipino, Native Hawaiian, Japanese, mixed/non-Hawaiian, and "other" Hawai'i high school students (N = 2,833). Given the relatively unique sample in question and the sheer number of variables, an exploratory approach was utilized with the goal of determining the most robust independent variables, with the unique inclusion of Hawaiian cultural identification. A cross-validation technique was used, whereby stepwise regressions were performed for each of two cross-validation samples; only common variables were retained in a final stepwise model for each of the four school outcomes. The results indicated that, remarkably, substance use accounted for the most variance (i.e., 8.4% -16.1 %) in the four school measures. Further analyses detailed the relationship, including the finding that smoking cigarettes regularly, accounted for the most variance compared to the other five substance use items. Further research and implications of the findings are discussed, including the need for prevention and intervention programs that incorporate substance use as a component, both within and outside of school environments. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
17.
In the present work, the chemical characterization of the oils obtained from liquefaction of different coals with sugar cane bagasse oil and also from the liquefaction of coal with monoethanolamine are presented. Characterization of the oil samples was done with the add of spectroscopic and chromatographic techniques, including UV-vis, FTIR, NMR, preparative liquid chromatography (PLC) and high resolution gas chromatography (HRGC). 相似文献
18.
Simultaneous HPLC quantification of total cholesterol,tocopherols and β-carotene in Barrosã-PDO veal 总被引:1,自引:0,他引:1
José A. Mestre Prates Mário A. Gonçalves Quaresma Rui J. Branquinho Bessa Carlos M.G. Andrade Fontes Cristina M.P. Mateus Alfaia 《Food chemistry》2006
A simple, rapid and sensitive procedure for the simultaneous determination of total cholesterol, tocopherols and β-carotene in meat is described. The method involves a direct saponification of the meat, a single n-hexane extraction and the analysis of the extracted compounds by normal-phase HPLC, using fluorescence (tocopherols) and UV–Vis photodiode array (cholesterol and β-carotene) detections in tandem. Rates of recovery of spiked meat samples were 93% for cholesterol, 83–86% for (α-, β- and -γ) tocopherols and 89% for β-carotene. Repeatabilities were high (CV < 6%) for all determined compounds, except for δ-tocopherol. This tocopherol, which is not usually present in meat, showed a much lower recovery percentage (73%) and repeatability (12.8%). This methodology was applied for the quantification of total cholesterol, tocopherols and β-carotene in three muscles (longissimus thoracis, longissimus lumborum and semitendinosus) of the Portuguese traditional Barrosã-PDO veal, obtained from autochthonous calves fed extensively during summer (with the least abundant green pastures) and slaughtered in early autumn (October). Barrosã-PDO veal showed median contents of total cholesterol (0.50–0.56 mg/g) and, depending on the analysed muscle, moderate to high contents of α-tocopherol (3.3–3.9 μg/g) and β-carotene (0.07–0.09 μg/g), suggesting an high sensorial and hygienic quality. 相似文献
19.
Raquel Alves dos Santos Teresinha Rosa Cabral Isabel Rosa Cabral Lusania Maria Greggi Antunes Cristiane Pontes Andrade Plínio Cerqueira dos Santos Cardoso Marcelo de Oliveira Bahia Claudia Pessoa José Luis Martins do Nascimento Rommel Rodríguez Burbano Catarina Satie Takahashi 《Biocell》2008,32(2):195-200
Physalis angulata L (Solanaceae) is a medicinal plant from North of Brazil, whose different extracts and infusions are commonly used in the popular medicine for the treatment of malaria, asthma, hepatitis, dermatitis and rheumatism. However, the genotoxic effects of P. angulata on human cells is not well known. The main purpose of the present study was to evaluate the in vitro genotoxic effects of aqueous extract of P. angulata using the comet assay and the micronucleus assay in human lymphocytes provided from 6 healthy donors. Treatments with P. angulata extracts were performed in vitro in order to access the extent of DNA damage. The comet assay has shown that treatments with P. angulata at 0.5, 1.0, 2.0, 3.0 and 6.0 microg/mL in culture medium were genotoxic. Lymphocytes treated with P. angulata at the concentrations of 3.0 and 6.0 microg/mL in culture medium showed a statistically significant increase in the frequency of micronucleus (p<0.05), however, the cytokinesis blocked proliferation index (CBPI) was not decreased after P. angulata treatment. In conclusion, the present work demonstrated the genotoxic effects of P. angulata extract on human lymphocytes in vitro. 相似文献
20.
Schistosoma mansoni and S. japonicum infections in nude mice (nu/nu) were compared with infections in nu/+ heterozygotes or intact mice. Seven to 12 weeks after exposure to S. mansoni, the responses of Swiss NCR, C3H, BALB/c and C57B1/6 nude mice did not differ substantially. Nude mice of all these strains showed minute granulomas around eggs in the liver and minimal hepatic fibrosis. Microvesicular and necrotizing changes in hepatocytes were similar in all mouse strains, and S. mansoni infections were frequently lethal to nude, but not to intact mice between the seventh and ninth weeks of infection. Nude mice that survived the ninth week of infection generally lived until the 12th week. The number of eggs per mature worm pair in the tissues of S. mansoni-infected nude mice was similar to the number in intact mice, but nude mice passed fewer eggs in the feces. Nude mice that received serum from infected intact mice excreted eggs in the stool in numbers equivalent to intact mice, but continued to form minute granulomas around S. mansoni eggs. Reconstitution with fetal thymus or with splenocytes from normal or S. mansoni-infected mice partially or completely restored hepatic granuloma size, granuloma eosinophils, hepatic fibrosis, and excretion of eggs in the feces. In contrast to S. mansoni infection, S. japonicum infections in nude mice did not cause necrosis of hepatocytes or excessive mortality, and S. japonicum eggs were passed in the feces in numbers equivalent to those passed by infected intact mice. 相似文献