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121.
Bing-Shun HuangMing-Yen Wey 《International Journal of Hydrogen Energy》2011,36(16):9479-9486
The effect of calcination temperature on the properties and H2 production ability of nitrogen-doped (N-doped) titanium dioxide (TiO2) photodeposited with 0.2 wt% Pt (platinum) was studied. The increase in crystallinity of pre-calcinated N-doped TiO2 initiated at temperatures higher than 131 °C transformed the morphology from anomalous nanostructure to texture composed of nanoparticles and enhanced the specific surface areas. At 200-400 °C, the anatase peaks gradually became sharper and the visible light absorption region decreased due to the growth of crystallites and the decrease of N-doping content, respectively. Maximum H2 production was reached when N-doped TiO2 was calcined at 200 °C followed by Pt photodeposition. The maximum condition is brought about by the formation of textures consisting of nanoparticles and a broad absorption region, thus creating superior active sites for photocatalytic H2 production. 相似文献
122.
Canadian cities are active competitors in the process of recruiting immigrants to help them increase diversity, improve their economies, and stimulate population growth. This study of Halifax, a small city in eastern Canada, suggests that some features which make the city-region attractive for inter-provincial migrants — such as the easy pace of life, perceptions of homogeneity, and tight social networks — affect the ability of international migrants to integrate in the community. 相似文献
123.
Cleavable surfactants 总被引:6,自引:0,他引:6
Per-Erik Hellberg Karin Bergström Krister Holmberg 《Journal of surfactants and detergents》2000,3(1):81-91
Cleavable surfactants are of interest for several reasons. Above all, the development of surfactants with weak bonds deliberately
built into the structure is driven by the need for improved biodegradability of amphiphiles. The breakdown may be catalyzed
by enzymes, and biodegradation would be the normal mechanism in sewage plants. Alternatively, the surfactant may degrade by
chemical means, e.g., induced by acid, alkali, ultraviolet (UV) light, heat, or ozone. Acid- and alkali-labile surfactants
have attracted particular attention, and there is often a compromise between required stability at one stage and ease of breakdown
at a subsequent stage. The paper reviews the main routes used to prepare cleavable surfactants and points out advantages and
disadvantages of the different approaches. Emphasis is placed on the development during recent years. Cyclic and acyclic acetals,
ketals, and ortho esters are the most important types of bonds for the preparation of acid-labile surfactants, whereas alkali-labile
amphiphiles usually are based on ester bonds. The ester bond approach has been particularly important for cationic surfactants,
and so-called ester quats have rapidly taken a large share of the traditional market for quats. Betaine esters constitute
a special class of ester with very pronounced pH dependence. UV-labile surfactants based, for instance, on an azo bond, offer
promise for the future. 相似文献
124.
Dimer formation during the thermo-oxidation of stigmasterol 总被引:1,自引:1,他引:0
Karin Struijs Anna-Maija Lampi Velimatti Ollilainen Vieno Piironen 《European Food Research and Technology》2010,231(6):853-863
The monomeric oxidation products formed during the thermo-oxidation of phytosterols do not explain the loss of unoxidized
phytosterols, leaving a gap in the knowledge on the products that are being formed during thermo-oxidation. Previous research
showed that the gap can be explained by the formation of dimers and polymers. The aim of this research was to investigate
the dimers that are formed during the thermo-oxidation of phytosterols, using stigmasterol as a model compound. Following
the oxidation of stigmasterol at 180 °C, several dimeric fractions were obtained by solid phase extraction and high-performance
size-exclusion chromatography. Individual dimers were separated by reversed-phase high-performance liquid chromatography,
and their molecular masses were determined by combining atmospheric pressure chemical ionization-mass spectrometry and coordination-ion
spray-mass spectrometry. This study resulted, for the first time, in the assignment of several individual stigmasterol dimers.
The most dominant dimer was found to have a molecular mass of 822.7 Da and is suggested to represent a C–C linked dimer of
stigmasterol, in accordance with literature. Several other stigmasterol dimers were found to be formed during thermo-oxidation,
which are suggested to differ in monomeric subunit composition, linkage type, and stereochemistry. 相似文献
125.
Karin Hoppert Susann Zahn Luise Jänecke Robert Mai Stefan Hoffmann Harald Rohm 《International Dairy Journal》2013,28(1):1-7
Reduction of energy in foods by eliminating sugar, combined with an increase in fiber, frequently results in products with sensory characteristics that cannot be compared with standard counterparts. This study analyzed the response of young educated consumers (n = 704) on standard or reduced-sugar vanilla yogurt enriched with inulin or with inulin combined with a grain mixture, a milled mixture of flakes, or a combination of grains and milled flakes. On a nine-point hedonic scale, mean acceptance was 6.4 and 6.8 for yogurt with 112 g kg?1 and 160 g kg?1 sugar, respectively. It was concluded from acceptance data and from results obtained by just-about-right rating that adapting the flavoring concentration might be an appropriate tool to mask sugar reduction. In yogurt with visible fiber, it is mainly the size of incorporated fiber that should be considered in product optimization. In these products, sugar content significantly affects acceptance. 相似文献
126.
Anne Lanfer Karin Bammann Kolja Knof Kirsten Buchecker Paola Russo Toomas Veidebaum Yiannis Kourides Stefaan de Henauw Dénes Molnar Silvia Bel-Serrat Lauren Lissner Wolfgang Ahrens 《Food quality and preference》2013,27(2):128-136
The present study investigated taste preferences in a sample of 1705 children aged 6 to 9 years from survey centres in Italy, Estonia, Cyprus, Belgium, Sweden, Germany, Hungary, and Spain and aimed to identify factors correlated with taste preference. Children’s preferences for varying levels of sucrose (sweet) in apple juice and fat, sodium chloride (salt) and monosodium glutamate (umami) in crackers were assessed using paired-comparison tests. Socio-demographics (age, sex, parental education), early feeding practises (breastfeeding, introduction of fruits), parenting behaviour (TV viewing, using food as a reward) and taste threshold sensitivity for sucrose (sweet), sodium chloride (salt), caffeine (bitter) and monosodium glutamate (umami) were investigated as possible correlates of taste preferences. Parents reported on socio-demographics, early feeding and parenting behaviour. Taste thresholds were determined via a paired-comparison staircase method. Country of residence was the strongest factor related to preferences for all four tastes. Taste preferences also differed by age. Preference for sugar and salt increased between 6 and 9 years of age while preference for monosodium glutamate decreased. The age differences remained significant even after adjustment for sex, country of residence, parental education and early feeding habits. Sex, parental education, early feeding habits, TV viewing, using food as a reward and taste thresholds were not consistently related to taste preferences among the survey centres. In summary, the results highlight the importance of culture and age in taste preferences in children younger than 10 years of age. 相似文献
127.
Estimating probability distributions that describe bacterial concentrations in food products is a key element of quantitative microbial risk assessments. Standard bacteriological protocols for bacterial enumeration first apply a detection test to a set of samples. For samples that test positive, bacterial concentrations are quantified using a serial dilution assay such as the most probable number (MPN) method. Estimation of bacterial concentration distributions based on a set of such data, however, represents a considerable statistical challenge. A maximum likelihood approach has been published to estimate bacterial concentrations from this type of data while accounting for the censored nature of the data. In this study, we derived an alternative method, based on complete likelihood maximization from observed MPN pattern data. Both methods were first evaluated in simulation studies, which showed that the latter method generated unbiased estimates of the parameters of the bacterial concentration distribution, while the former method generated biased results. The bias was particularly pronounced when bacterial concentrations were low. Both methods fail to predict accurately low contamination levels at low prevalence (e.g. mean of ?7 log10 for contaminated products and prevalence of 0.2). The methods were then applied to bacteriological data from a food survey of Listeria monocytogenes in the United States. The former method led to approximately 1 log10 cfu higher estimated mean bacterial concentration compared to estimates generated using the alternative method. The alternative method is preferable, in particular if bacterial concentrations are low. 相似文献
128.
Karin Schiefenh?vel Dr. Hartmut Rehbein 《Journal für Verbraucherschutz und Lebensmittelsicherheit》2011,6(2):203-214
Fish and fillet of barramundi (Lates calcarifer) and tilapia (Oreochromis species) obtained from wholesale and retail trade were assigned to species by sequencing of PCR products. Two segments (358 and 464?bp) of the cytochrome b gene (cytb) were amplified using universal primers. The amplicons gave characteristic patterns in SSCP-analysis (single strand conformation polymorphism) suitable for differentiation of Lates calcarifer from Lates niloticus and Lateolabrax japonicus. Intra-specific variation of sequences and SSCP patterns were observed for barramundi. In case of tilapia species, it was found to be difficult to identify samples by BLAST due to the high similarity of cytb sequences of O. niloticus, O. mossambicus, O. aureus and Sarotherodon galileus. Four different patterns of single strand DNA (ssDNA) were obtained by SSCP analysis of the 464?bp amplicon of tilapia. Different patterns of ssDNA matched to variations in sequences. Protein profiles obtained by IEF (isoelectric focusing) of water-soluble proteins from raw fillet were found to be suitable for rapid differentiation of Lates calcarifer from Lateolabrax japonicus, but the three different Oreochromis species expressed only minor differences in protein patterns. The patterns of the tilapia and barramundi species showed a number of acidic, heat-stable proteins, presumably representing parvalbumin. 相似文献
129.
L. A. Glushchenko V. A. Golovkov M. G. Karin K. K. Morgunov V. I. Tupota 《Optical Memory & Neural Networks》2010,19(4):338-343
The analysis of probability of erroneous reception of one binary code are lead for transfer of the information to the open
optical data links, including IR-keyboards. Theoretical estimations for maximum permissible values of the attitude a signal/noise
are received. 相似文献
130.