全文获取类型
收费全文 | 1602篇 |
免费 | 50篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 482篇 |
金属工艺 | 32篇 |
机械仪表 | 9篇 |
建筑科学 | 63篇 |
矿业工程 | 2篇 |
能源动力 | 32篇 |
轻工业 | 172篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 171篇 |
一般工业技术 | 298篇 |
冶金工业 | 144篇 |
原子能技术 | 13篇 |
自动化技术 | 212篇 |
出版年
2023年 | 8篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 19篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 26篇 |
2014年 | 41篇 |
2013年 | 87篇 |
2012年 | 58篇 |
2011年 | 97篇 |
2010年 | 68篇 |
2009年 | 70篇 |
2008年 | 90篇 |
2007年 | 67篇 |
2006年 | 71篇 |
2005年 | 50篇 |
2004年 | 63篇 |
2003年 | 51篇 |
2002年 | 70篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 36篇 |
1998年 | 32篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 24篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 30篇 |
1984年 | 13篇 |
1983年 | 23篇 |
1982年 | 14篇 |
1981年 | 13篇 |
1980年 | 19篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1976年 | 16篇 |
1975年 | 20篇 |
1974年 | 10篇 |
1966年 | 7篇 |
排序方式: 共有1662条查询结果,搜索用时 12 毫秒
41.
Oregano: chemical analysis and evaluation of its antimalarial, antioxidant, and cytotoxic activities
El Babili F Bouajila J Souchard JP Bertrand C Bellvert F Fouraste I Moulis C Valentin A 《Journal of food science》2011,76(3):C512-C518
Abstract: GC‐FID and GC‐MS analysis of essential oil from oregano leaves (Origanum compactum) resulted in the identification of 46 compounds, representing more than 98% of the total composition. Carvacrol was the predominant compound (36.46%), followed by thymol (29.74%) and p‐cymene (24.31%). Serial extractions with petroleum ether, ethyl acetate, ethanol, and water were performed on aerials parts of Origanum compactum. In these extracts, different chemical families were characterized: polyphenols (gallic acid equivalent 21.2 to 858.3 g/kg), tannins (catechin equivalent 12.4 to 510.3 g/kg), anthocyanins (cyanidin equivalent 0.38 to 5.63 mg/kg), and flavonoids (quercetin equivalent 14.5 to 54.7 g/kg). The samples (essential oil and extracts) were subjected to a screening for antioxidant (DPPH and ABTS assays) and antimalarial activities and against human breast cancer cells. The essential oil showed a higher antioxidant activity with an IC50= 2 ± 0.1 mg/L. Among the extracts, the aqueous extract had the highest antioxidant activity with an IC50= 4.8 ± 0.2 mg/L (DPPH assay). Concerning antimalarial activity, Origanum compactum essential oil and ethyl acetate extract showed the best results with an IC50 of 34 and 33 mg/mL, respectively. In addition, ethyl acetate extract (30 mg/L) and ethanol extract (56 mg/L) showed activity against human breast cancer cells (MCF7). The oregano essential oil was considered to be nontoxic. 相似文献
42.
43.
Jean Claude Assaf Andr El Khoury Ali Chokr Nicolas Louka Ali Atoui 《International Journal of Dairy Technology》2019,72(2):248-256
This study aimed to develop a new method for detoxification of milk from aflatoxin M1 (AFM1) by using Lactobacillus rhamnosus GG biofilm. After inoculation of milk contaminated with AFM1 into L. rhamnosus GG biofilm, the unbound AFM1 was extracted and quantified by HPLC. The stability of the formed AFM1/biofilm complex using different AFM1 contamination levels of milk was also studied. We found that the percentages of bound AFM1 by L. rhamnosus GG biofilm reached up to 60.74%. While no significant difference in milk proteins content was observed after AFM1 binding, some changes in total dry matter and fat content were noticed. 相似文献
44.
Nooshin Araghipour Jennifer Colineau Alex Koot Wies Akkermans Jose Manuel Moreno Rojas Jonathan Beauchamp Armin Wisthaler Tilmann D. Märk Gerard Downey Claude Guillou Luisa Mannina Saskia van Ruth 《Food chemistry》2008
The volatile compositions of 192 olive oil samples from five different European countries were investigated by PTR-MS sample headspace analysis. The mass spectra of all samples showed many masses with high abundances, indicating the complex VOC composition of olive oil. Three different PLS-DA models were fitted to the data to classify samples into ‘country’, ‘region’ and ‘district’ of origin, respectively. Correct classification rates were assessed by cross-validation. The first fitted model produced an 86% success rate in classifying the samples into their country of origin. The second model, which was fitted to the Italian oils only, also demonstrated satisfactory results, with 74% of samples successfully classified into region of origin. The third model, classifying the Italian samples into district of origin, yielded a success rate of only 52%. This lower success rate might be due to either the small class set, or to genuine similarities between olive oil VOC compositions on this tight scale. 相似文献
45.
Croizé L Mondelain D Camy-Peyret C Delmotte M Schmidt M 《The Review of scientific instruments》2008,79(4):043101
We have developed a tunable diode laser spectrometer, called SIMCO (spectrometer for isotopic measurements of CO(2)), for determining the concentrations of (12)CO(2) and (13)CO(2) in atmospheric air, from which the total concentration of CO(2) and the isotopic composition (expressed in delta units) delta(13)CO(2) are calculated. The two concentrations are measured using a pair of lines around 2290.1 cm(-1), by fitting a line profile model, taking into account the confinement narrowing effect to achieve a better accuracy. Using the Allan variance, we have demonstrated (for an integration time of 25 s) a precision of 0.1 ppmv for the total CO(2) concentration and of 0.3[per thousand] for delta(13)CO(2). The performances on atmospheric air have been tested during a 3 days campaign by comparing the SIMCO instrument with a gas chromatograph (GC) for the measurement of the total CO(2) concentration and with an isotopic ratio mass spectrometer (MS) for the isotopic composition. The CO(2) concentration measurements of SIMCO are in very good agreement with the GC data with a mean difference of Delta(CO(2))=0.16+/-1.20 ppmv for a comparison period of 45 h and the linearity of the concentration between the two instruments is also very good (slope of correlation: 0.9996+/-0.0003) over the range between 380 and 415 ppmv. For delta(13)CO(2), the comparison with the MS data shows a larger mean difference of Delta(delta(13)CO(2))=(-1.9+/-1.2)[per thousand], which could be partly related to small residual fluctuations of the overall SIMCO instrument response. 相似文献
46.
Claude Leger Lucie Fremont Didier Marion Ibrahim Nassour Marie-Françoise Desfarges 《Lipids》1981,16(8):593-600
This paper describes evidence of (n−3) and particularly of 22∶6 (n−3) fatty acid enrichment in trout lipoproteins as well
as in vitellogenin, egg lipovitellin and oil globule. Among the lipoproteins, HDL and LDL were the main forms of blood lipid
transport, whereas phospholipids and cholesteryl esters are the preferential chemical carriers for (n−3) fatty acid transport.
However, cholesteryl esters were less important as esterified fatty acid carriers than in man. Taken together with the data
obtained in mammals, our results suggest that there may be a relationship between EFA activity and the distribution of the
EFA among the lipoprotein lipid fractions in vertebrates, irrespective of the EFA series. Administration of an (n−3) fatty
acid deficient diet for three months prior to trout spawning produced a significant increase in egg lipid content, primarily
as a result of the increase of the oil globule composed almost exclusively of triacylglycerols. This diet decreased the 22∶6
(n−3), as well as the (n−3) fatty acid contents of lipoproteins, lipovitellin, vitellogenin and the oil globule. In contrast,
the (n−3) fatty acid level was always higher in lipoproteins and lipovitellin than in the vitellogenin and the oil globule.
Moreover, the relative levels of 22∶6 (n−3) and total (n−3) fatty acids were quite similar in lipoproteins and lipovitellin
on the one hand, and in vitellogenin and the oil globule on the other. These findings suggest a direct relationship between
the two forms of plasma lipid transport and the two egg compartments. During ovogenesis, dietary lipids seemed to be diverted
from the adipose tissue and essentially deposited in the egg. 相似文献
47.
Helena A. Soini Donald Wiesler Sachiko Koyama Christophe Féron Claude Baudoin Milos V. Novotny 《Journal of chemical ecology》2009,35(5):580-589
Whereas the house mouse (Mus domesticus) has been studied extensively in terms of physiology/behavior and pheromonal attributes, the evolutionarily related mound-building
mouse (Mus spicilegus) has received attention only recently due to its divergent behavioral traits related to olfaction. To date, no chemical studies
on urinary volatile compounds have been performed on M. spicilegus. The rationale for our investigations was to determine if there are differences in urinary volatiles of intact and castrated
M. spicilegus males and to explore further whether this species could utilize the same or structurally similar pheromones as the male house
mouse, M. domesticus. The use of capillary gas chromatography/mass spectrometry (GC-MS) together with sorptive stir bar extraction sampling enabled
quantitative comparisons between the intact and castrated M. spicilegus urinary profiles. Additionally, through GC-MS and atomic emission (sulfur-selective) detection, we identified qualitative
molecular differences between intact M. spicilegus and M. domesticus. A series of volatile and odoriferous lactones and the presence of coumarin were the unique features of M. spicilegus, as was the notable absence of 2-sec-butyl-4,5-dihydrothiazole (a prominent M. domesticus male pheromone) and other sulfur-containing compounds. Castration of M. spicilegus males eliminated several substances, including δ-hexalactone and γ-octalactone, and substantially decreased additional compounds,
suggesting their possible role in chemical communication. Some other M. domesticus pheromone components were also found in M. spicilegus urine. These comparative chemical analyses support the notion of metabolic similarities as well as the uniqueness of some
volatiles for M. spicilegus, which may have a distinct physiological function in reproduction and behavior. 相似文献
48.
YBCO textured thick film was prepared by direct periteetic growth method. Microstructure of the film was characterized. Electron backscattered diffraction (EBSD) technique was applied to the film for quantitative texture analysis. The main difficulty in resolving the ori-entation of YBCO pseudo-cubic structure was investigated. Automated orientation mapping was performed on YBCO thick film. Local tex-ture was presented in the form of orientation maps. Misorientation distribution and crystal growth characterization in the YBCO thick film were revealed. Large domains with well-aligned YBCO grains were formed. Each domain presented clear in-plane and out-plane textures. 相似文献
49.
Lna Saint Macary Myrtil L. Kahn Claude Estourns Pierre Fau David Trmouilles Marise Bafleur Philippe Renaud Bruno Chaudret 《Advanced functional materials》2009,19(11):1775-1783
Conditions for the elaboration of nanostructured varistors by spark plasma sintering (SPS) are investigated, using 8‐nm zinc oxide nanoparticles synthesized following an organometallic approach. A binary system constituted of zinc oxide and bismuth oxide nanoparticles is used for this purpose. It is synthesized at room temperature in an organic solution through the hydrolysis of dicyclohexylzinc and bismuth acetate precursors. Sintering of this material is performed by SPS at various temperatures and dwell times. The determination of the microstructure and the chemical composition of the as‐prepared ceramics are based on scanning electron microscopy and X‐ray diffraction analysis. The nonlinear electrical characteristics are evidenced by current–voltage measurements. The breakdown voltage of these nanostructured varistors strongly depends on grain sizes. The results show that nanostructured varistors are obtained by SPS at sintering temperatures ranging from 550 to 600 °C. 相似文献
50.
Rachman Chaim Amit Shlayer Claude Estournes 《Journal of the European Ceramic Society》2009,29(1):91-98
Nanocrystalline Y2O3 powders with 18 nm crystallite size were sintered using spark plasma sintering (SPS) at different conditions between 1100 and 1600 °C. Dense specimens were fabricated at 100 MPa and 1400 °C for 5 min duration. A maximum in density was observed at 1400 °C. The grain size continuously increased with the SPS temperature into the micrometer size range. The maximum in density arises from competition between densification and grain growth. Retarded densification above 1400 °C is associated with enhanced grain growth that resulted in residual pores within the grains. Analysis of the grain growth kinetics resulted in activation energy of 150 kJ mol?1 and associated diffusion coefficients higher by 103 than expected for Y3+ grain boundary diffusion. The enhanced diffusion may be explained by combined surface diffusion and particle coarsening during the heating up with grain boundary diffusion at the SPS temperature. 相似文献