全文获取类型
收费全文 | 1082篇 |
免费 | 64篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 328篇 |
金属工艺 | 12篇 |
机械仪表 | 10篇 |
建筑科学 | 18篇 |
能源动力 | 20篇 |
轻工业 | 498篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 29篇 |
一般工业技术 | 95篇 |
冶金工业 | 39篇 |
原子能技术 | 3篇 |
自动化技术 | 78篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 47篇 |
2021年 | 45篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 36篇 |
2017年 | 37篇 |
2016年 | 36篇 |
2015年 | 36篇 |
2014年 | 49篇 |
2013年 | 59篇 |
2012年 | 76篇 |
2011年 | 80篇 |
2010年 | 55篇 |
2009年 | 45篇 |
2008年 | 64篇 |
2007年 | 48篇 |
2006年 | 51篇 |
2005年 | 54篇 |
2004年 | 40篇 |
2003年 | 34篇 |
2002年 | 29篇 |
2001年 | 19篇 |
2000年 | 9篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 25篇 |
1995年 | 10篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1146条查询结果,搜索用时 15 毫秒
81.
Ananías Pascoal Marta Prado Pilar Calo Alberto Cepeda Jorge Barros-Velázquez 《European Food Research and Technology》2005,220(3-4):444-450
The identification of beef in animal foods is a major concern not only for the prevention of commercial fraud, but also to avoid safety risks deriving from the presence of prohibited bovine material that might be harmful to both human and animal health. Here we report a novel set of bovine-specific primers, CYTbos1 (forward) and CYTbos2 (reverse), which allow the specific amplification of a 115 base pair fragment of the bovine cytochrome b gene (cytb) between nt 844 (mitochondrial site 15,590) and nt 958 (mitochondrial site 15,704), no cross-reaction being observed with DNA from another 12 frequent commercial meat species. The polymerase chain reaction product obtained is cleaved specifically by endonucleases ScaI and TspE1 to achieve further confirmation evidence. The sensitivity of the proposed method was 0.025%. The CYTbos primers successfully detected bovine DNA in meat samples processed for 20 min at 133 °C/300 kPa or for 2 h at 121 °C. CYTbos primers also detected bovine DNA in heat-processed commercial meat products exhibiting a complex nature, as well as in bovine specific risk materials. The proposed polymerase chain reaction method, aimed at detecting a small and specific fragment of the bovine mitochondrial DNA, may be especially useful for the direct identification of bovine DNA in foodstuffs subjected to severe heating under overpressure conditions. 相似文献
82.
Gloria Urbano Sławomir Frejnagel Jesús M. Porres Pilar Aranda Elena Gomez-Villalva Juana Frías María López-Jurado 《European Food Research and Technology》2007,226(1-2):105-111
The effect of dephytinization of Pisum sativum, L. flour on the bioavailability of Mg and Zn was evaluated in growing rats. Processing of legume flours under optimal conditions
for phytase activity (pH 5.5, 37 °C, 60 min) and subsequent removal of the soaking solution led to a 42 and 61% reduction
in the content of Mg and Zn, respectively. Treatment with phytase led to an additional reduction in the concentration of the
above-mentioned seed flour components, compared to the raw pea flour (69% and 74% for Mg and Zn, respectively). The considerable
reduction in the content of inositol phosphates with high degree of phosphorylation attained under both processing conditions
did not affect the digestive utilization of Mg, whereas the metabolic utilization of this mineral increased significantly.
The digestive and metabolic utilization of Zn increased significantly in response to both processes assayed, reaching the
highest values in the experimental group that was fed the phytase-treated pea flour diet. The amount of Mg retained by the
experimental animals was reflected in the content of this mineral in the different tissues studied (femur, sternum, kidney,
and heart), whereas no correlation was found in the case of Zn. 相似文献
83.
Carmen García-Domingo Pilar Rupérez F. Saura-Calixto 《European Food Research and Technology》1997,204(1):43-47
Profiles of flavonoid compounds of Apis mellifera and Melipona spp. honeys from Venezuela were analysed to evaluate entomological-dependent differences. The presence of ellagic acid was
a characteristic of A. mellifera honeys from Venezuela, but its presence was variable in Melipona spp. samples. The number of flavonoid types present in individual samples did not exceed six and occasionally only one phenolic
type was present. The diversity of flavonoid compounds in tropical honeys from Venezuela was lower than that previously measured
in temperate honeys. Flavonoids such as myricetin, an unidentified chalcone and a flavonol glycoside were only found in Melipona honeys but not in all the samples; therefore, they cannot be foreseen as entomological markers to differentiate between the
Apis and Melipona honeys under study. A preliminary discussion is made regarding flavonoids present in Melipona honeys and their probable link with the putative anticataract action of stingless bee-honeys.
Received: 22 February 1996 相似文献
84.
Alejandro González Orive Alberto Hernández Creus Pilar Carro Roberto C. Salvarezza 《Organic Electronics》2012,13(10):1844-1852
We have studied the adsorption and electronic properties of thin melanin films on Au(1 1 1) by scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), and density functional (DF) calculations. We have found that the minimum melanin unit detected under different adsorption conditions is consistent with the structural model for eumelanin protomolecules based on tetramer macrocycles formed by four monomer units (hydroquinone, indolequinone and its tautomers) with an inner porphyrin ring. DF calculations reveal that the entire π structure of the tetramers is implied in the chemisorption process through its frontier orbitals (HOMO and LUMO), a fact that is reflected in the change of intramolecular bonds. Also van der Waals interactions give an important contribution to the adsorption energy (≈0.02 eV/Å2). Dried thin melanin films (1 monolayer in thickness) exhibit good electronic conductance due to the presence of localized states near the Fermi level while dried thicker films exhibit a semiconductor-like behavior. Illumination of the thicker films with white light results in significant photo-induced tunneling currents when the melanin-covered Au is made negative with respect to the tip. 相似文献
85.
High-pressure treatment is useful for increasing the microbiological safety of ready-to-eat foods. With dry-cured hams, this treatment can be applied to the finished product after slicing and vacuum packaging. The effect of high-pressure treatment on the survival of inoculated Listeria monocytogenes Scott A and on the sensory characteristics of two Spanish dry-cured hams, Iberian and Serrano, was investigated. Ham slices were inoculated with L. monocytogenes at 6 x 10(6) CFU/g and held at 4 degrees C for 20 h before high-pressure treatment. During this holding period, the population of the pathogen declined by 0.44 and 0.51 log CFU/g in Iberian and Serrano hams, respectively. Treatment at 450 MPa for 10 min at 12 degrees C reduced L. monocytogenes populations by 1.50 and 1.16 log CFU/g in Iberian and Serrano hams, respectively. During the first week of storage at 4 or 8 degrees C, L. monocytogenes populations declined by an average 0.89 log CFU/g in pressurized Iberian ham and 2.09 log CFU/g in pressurized Serrano ham. After 60 days at 4 or 8 degrees C, the respective populations in pressurized and control hams were 3.24 and 4.70 log CFU/g for Iberian ham and 2.73 and 5.07 log CFU/g for Serrano ham. The color parameters L* and a* were not influenced by high-pressure treatment, and parameter b* was increased only in Iberian ham. Sensory characteristics of hams were not affected by high-pressure treatment. Treatment of Iberian and Serrano hams at 450 MPa for 10 min significantly reduced the population of L. monocytogenes Scott A without a detrimental effect on the sensory characteristics of the hams. 相似文献
86.
J. S. Felton Pilar Pais Cynthia P. Salmon Mark G. Knize 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1998,207(6):434-440
Levels of known heterocyclic amines vary from undetectable in many meats sold in fast food restaurants, to over 10 ng/g for
meats prepared in restaurants that cook food to order, to hundreds of nanograms per gram for some meats cooked under certain
home or laboratory conditions. To simulate the dry reactions that seem to occur at the meat surface we developed a model system
to mimic these processes. Mixtures of free amino acids, creatinine and glucose, simulating the composition of beef or chicken,
heated at 200 °C, form eight heterocyclic amines. Besides the commonly found 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, 2-amino-3-methylimidazo[4,5-f]quinoline, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, 2-amino-1,6-dimethylimidazo[4,5-b]pyridine, 2-amino-1,5,6-trimethylimidazo[4,5-b]pyridine and 2-amino-1,6-dimethylfuro[3,2-e]imidazo[4,5-b]pyridine were also found. The calculated risk of consumption of heterocyclic amines is determined by the dietary dose, the
extrapolation of carcinogenic potencies from rodents to humans, and the extrapolation of high rodent doses to low human exposures.
Results suggest that DNA binding is linear with dose, but that the human DNA forms more adducts per unit dose than that of
the rat. Altogether, the risk appears to be equivalent to that for many carcinogens that are regulated.
Received: 23 April 1998 相似文献
87.
Karola B?hme Inmaculada C. Fern��ndez-No Jose M. Gallardo Benito Ca?as Pilar Calo-Mata 《Food and Bioprocess Technology》2011,4(6):907-918
Foodborne intoxications caused by the consumption of fish and other products of marine origin contaminated with bacterial
pathogens are an ever-present threat, either due to bacteria and/or its metabolites. In addition, the rapid spoilage of seafood
due to microbial activity, results in high economic losses. The development of the microbiota in seafood products depends
on the microbiological ambience of capture, processing and storage, and the applied preservation method. Thus, pathogenic
and spoilage bacterial species in seafood may come from the indigenous microbiota of the aquatic ambience or are introduced
by contamination during processing. Rapid and accurate bacterial species identification is essential for an effective control
program to ensure safety and quality of either processed or minimally processed seafood. In the present work, matrix-assisted
laser desorption ionization-time of flight mass spectrometry was successfully applied to identify 26 bacterial strains isolated
from fresh fish and processed seafood samples. The approach was based on the comparison of unknown spectra to a reference
spectral library and demonstrated to be a fast and accurate technique for bacterial species differentiation, which can be
used for the rapid identification of foodborne pathogens and spoilage bacteria potentially present in products of marine origin. 相似文献
88.
To determine the modulus of elasticity of concrete precisely is very important for structures that require strict control of the deformability. International codes propose a wide variety of formulae which establish a relationship between modulus of elasticity and compressive strength. Most of these codes are valid up to 50 MPa, the usual limit for normal concretes. A research programme has been carried out to establish the modulus of elasticity-compressive strength curve for low and high strength concretes. The effect of the aggregate also has been studied. This is an important factor to take into account, sometimes more important than the concrete strength itself or even age. A model code formula provides good correlation with experiment up to a compressive strength of 120 MPa. Other aggregates not considered for this code have been studied and results given. Also, the influence of age on the modulus of elasticity is discussed. 相似文献
89.
The extensive application of emerging technologies is revolutionizing warehouse management. These technologies facilitate working with complex and powerful warehouse management models in which products do not have assigned fixed locations (random storage). Random storage allows the utilization of the available space to be optimized. In this context, and motivated by a real problem, this article presents a model that looks for the optimal allocation of goods in order to maximize the storage space availability within the restrictions of the warehouse. For the proposed model a construction method, a local search algorithm and different metaheuristics have been developed. The introduced algorithms can also be used for other purposes such as to assess when and how it is convenient to perform relocation of stored items to improve the current level of storage space availability. Computational tests performed on a set of randomly generated and real warehouse instances show the effectiveness of the proposed methods. 相似文献