全文获取类型
收费全文 | 530篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 152篇 |
金属工艺 | 2篇 |
机械仪表 | 10篇 |
建筑科学 | 19篇 |
能源动力 | 11篇 |
轻工业 | 78篇 |
石油天然气 | 1篇 |
无线电 | 29篇 |
一般工业技术 | 111篇 |
冶金工业 | 19篇 |
原子能技术 | 5篇 |
自动化技术 | 114篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 21篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 25篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 33篇 |
2012年 | 40篇 |
2011年 | 39篇 |
2010年 | 34篇 |
2009年 | 29篇 |
2008年 | 28篇 |
2007年 | 39篇 |
2006年 | 16篇 |
2005年 | 14篇 |
2004年 | 17篇 |
2003年 | 15篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 11篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有561条查询结果,搜索用时 24 毫秒
61.
Influence of light on food relevant fungi with emphasis on ochratoxin producing species 总被引:1,自引:0,他引:1
Schmidt-Heydt M Rüfer C Raupp F Bruchmann A Perrone G Geisen R 《International journal of food microbiology》2011,145(1):229-237
The influence of light of varying wavelength on growth and ochratoxin A biosynthesis of Aspergillus carbonarius, A. niger, A. steynii and on Penicillium nordicum and P. verrucosum was analysed. For comparison the influence of light on various other food relevant fungi, including citrinin producers, was also tested. Generally the Aspergilli seem to be more resistant to light treatment than the Penicillia. Interestingly wavelengths from both sides of the spectrum, e. g. red (long wavelength, 627 nm) and blue (short wavelength 470-455 nm) had the strongest inhibitory effects on growth and ochratoxin A biosynthesis. Blue light generally had a stronger effect. Light of moderate wavelength, 590 to 530 nm, (yellow to green) had more a positive than a negative influence on growth or ochratoxin A biosynthesis compared to the control (dark incubation). The light effect on growth and ochratoxin A biosynthesis was dependent on the growth medium. In contrast to malt extract medium (MEA), YES medium, as an especially nutrient rich medium, had an attenuating effect on the reactivity against light. However the tendency of the response in both media was the same. Moreover, the light intensity strongly influences how the fungus reacts. Depending on the intensity and the resistance of the species a complete cessation of growth and/or inhibition of ochratoxin A biosynthesis could be achieved. Light irradiation has the opposite effect on ochratoxin A than citrinin, two mycotoxins which can be produced simultaneously in P. verrucosum. Citrinin was produced essentially under light conditions which inhibited ochratoxin A biosynthesis. The same was true for a derivative of ochratoxin, in particular a derivative of ochratoxin β in A. carbonarius. A. carbonarius produced high amounts of the ochratoxin β derivative under blue light when the production of ochratoxin A was ceased at the most inhibiting conditions used (MEA, royal blue light, 455 nm, 1700 lx). Light has a growth stalling but not inactivating effect on aerial mycelia. If a non-growing colony under light is shifted to the dark it immediately grows normally. However on spores blue light has a deactivating effect. After incubation of spores of P. verrucosum for 24 h under blue light up to 97% of the spores were no longer able to germinate. Again the spores of the Aspergilli were much more resistant. 相似文献
62.
Palmira Mazzaracchio Piergiorgio Pifferi Maddalena Kindt Athanase Munyaneza & Giancarlo Barbiroli 《International Journal of Food Science & Technology》2004,39(1):53-59
The interactions between different glucosidic anthocyanins (pelargonin, cyanin, delphinin, malvin and petunin) and some organic compounds (lactic, galacturonic, tannic, phenolic and sinapic acids; pyrogallol, furfural, pectin, cellulose, hydrolitic lignin) which are present in food‐stuffs were investigated at pH 3.0–4.3 and 25 °C. The interactions were monitored by means of u.v.‐VIS spectra and their different behaviours were highlighted by following changes in absorbance over a range of wavelengths (Δλ and ΔA). Significant effects on absorbance were detected and are discussed in terms of the phenomenon of co‐pigmentation. 相似文献
63.
In spite of cancer screening programs, women continue to present with advanced breast cancer. How do women decide whether and when to seek an evaluation for self-discovered symptoms? This study examined 104 narratives told by 80 Anglo-, Latina-, and African-American women who participated in 1 of 16 community-based focus groups. The women's narratives contained powerful thematic messages about breast cancer and their expected behavior in the event of a self-discovered breast symptom. Narrative explanations that predicted an increased likelihood of advanced disease at diagnosis included these factors: incorrect symptom attributions and risk estimations; reluctance to consider the threat posed by the symptom; failure to tell another person about the symptom; and expectations of abandonment by male partners, deportation, prejudice, and refusal of treatment due to poverty. Stories of advanced breast cancer also told of reliance on alternative healing, concerns about overwhelming family resources, and extreme modesty that inhibited obtaining a physical examination. Interventions aimed at earlier detection of breast cancer must connect with the beliefs and assumptions embedded in these narratives, provide pragmatic solutions for perceived constraints on seeking evaluations of self-discovered symptoms, and explore the use of community narratives to confirm the value of early detection of breast cancer. 相似文献
64.
Efficient removal of lymphocytes undergoing programmed cell death (apoptosis) by macrophages plays an important role for the proper function of normal immune system. Furthermore, in malignant lymphoma, elimination of apoptotic tumor cells by phagocytes contributes to the anti-tumor immune response. It is unknown, however, whether macrophages in normal and malignant lymphoid tissues differ in their ability to recognize and remove apoptotic cells. Our present results demonstrate that normal and malignant lymphoid tissues differ according to the extent of the infiltration by macrophages. The highest densities of macrophages (p < 0.0001) were detected in diffuse large B-cell lymphoma, centroblastic (DLBCL-CB) and immunoblastic variants and Burkitt's lymphoma. The grade of the macrophage infiltration correlated with the proliferation rates of the tumors (p < 0.0001). Compared with normal lymphoid organs, malignant lymphoma contained lower percentages of apoptotic cells phagocytosed by tissue macrophages (p < 0.001). Of all lymphomas tested, mantle cell lymphoma and DLBCL-CB expressed the lowest percentages of phagocytosed apoptotic cells (p < 0.0001). 相似文献
65.
Giancarlo Scalabrin Giovanni Cristofoli Maurizio Grigiante 《Chemical Engineering Communications》2002,189(12):1705-1729
Predictive and semipredictive models for viscosity calculation are currently needed and highly appreciated. Models developed for halogenated refrigerants (HR) and based on Corresponding States (CS) are leading to a prediction accuracy comparable to that of specifically developed models. In the present work, using recently published, highly accurate viscosity dedicated equations, it has been verified that viscosity conforms to a two-parameter CS model is then developed, based on Teja and coworker's three-parameter CS structure. Two fluids of the same family are taken for reference, and the reduced viscosity of a third fluid is obtained in reduced P,T variables. At first the Pitzer acentric factor is proposed as a third parameter, then it is substituted with a temperature-dependent function fitted on saturated viscosity data. The prediction accuracy of the model is comparable to that of the reference fluid equations and, considering its predictive nature, it is a satisfactory tool for the needs of technical applications. 相似文献
66.
Because of the progress in electronic technology and the increasing importance of colour quality control in various branches of industry, over the last decades several colour-measuring instruments have been developed, each one with its own design features; the lack of standardization among them might be an obstacle to the spread of colour quality control as a means for product qualification. Colour-difference measurements taken with 11 different models of spectrophotometers [four with 45 (circumferential)/0 geometry and the others with diffuse geometry] were compared with the aim of analyzing their correlation and dispersion. In order to cover different colour-space regions, measurements were taken on test panels painted with four saturated basic hue (red, yellow, green, and blue) acrylic products gradually modified by adding white or black paint. Basic statistical analyses made on colour-difference values (ΔE*ab, ΔL*, Δa*, and Δb*) resulted in a high correlation among the examined instruments, but a certain variability, particularly as far as certain hues are concerned. 相似文献
67.
Camponeschi Biagio Casa De Giancarlo Giglio Giovanni Mattias Pier Paolo 《Bulletin of Engineering Geology and the Environment》1984,29(1):21-25
Close to the present Latium coast, at Rio Torto, in the area between Pomezia and Ardea, about 35 km to the South of Rome, there are vast sandy deposits of continental and marine origin that may be associated with ancient coast lines. The extent and thickness of these deposits vary widely and are used as sources for extracting aggregate materials that are successfully used in preparing cement mortars. Field surveys and laboratory tests have helped identify these products as belonging to a paleogeographic environment and to define both their volume and their geographic location. The results obtained have allowed characterization of the sands from a technical point of view and to define their fields of utilization keeping account of their location and their mining availability. 相似文献
68.
Optically active (?)menthylethylfumarate (2) and (?)dimenthylfumarate (3) have been synthesised and free radically copolymerized with N-vinylcarbazole (1). Copolymers of (1) and (2) exhibit a strong tendency to alternation in agreement with earlier conclusions from studies of copolymerization of (1) with diethylfumarate. Surprisingly the much more hindered, but symmetrical fumarate, (3) yields copolymers which always have carbazole monomer contents in excess of the 1:1 alternating ratio. Chiroptical measurements indicate significant induced optical activity in the carbazole chromophores of all the copolymers obtained but, in accord with the predominance of alternating structures, there is no real evidence for any sequence-determined maximum in induced circular dichroism. Fluorescence emission spectra of all copolymer samples exhibit significant asymmetric broadening on the long wavelength (low energy) side of the normal carbazole monomeric emission. This broadening is exhibited even by poly (1-co-2) samples for which the monomer compositions strongly indicate alternating sequences and must, therefore, represent interaction between carbazole segments. Accordingly, and in contrast to widely held assumptions, it is concluded that excimer-like emission may be exhibited by alternating copolymers of N-vinylcarbazole. Further evidence for electronic interactions between non-nearest neighbour carbazole units is provided by u.v. absorption and 1H-n.m.r. spectra of appropriate copolymers. 相似文献
69.
Stanley HE Buldyrev SV Franzese G Giovambattista N Starr FW 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2005,363(1827):509-523
The thermodynamic behaviour of water seems to be related to static heterogeneities. These static heterogeneities are related to the local structure of water molecules and, when properly characterized, may offer an economical explanation of thermodynamic data. 'What matters' most in determining some of the unusual properties of liquid water may be the fact that the local geometry of the liquid molecules is not spherical or oblong, but rather tetrahedral. In respect to static heterogeneities, this local geometry is critical. The dynamic behaviour of water seems to be related to dynamic heterogeneities, which seem to explain the dynamics of supercooled liquid water well. 相似文献
70.
Camila R. Correa Lei Li Giancarlo Aldini Marina Carini C.-Y. Oliver Chen Hye-Kyung Chun Soo-Muk Cho Ki-Moon Park Robert M. Russell Jeffrey B. Blumberg Kyung-Jin Yeum 《Food chemistry》2010
Phytochemical compositions of five varieties of black soybeans (Glycine max) and their stabilities at room temperature, 4 and −80 °C over 14 months were determined by HPLC systems with electrochemical (ECD) and UV detectors. Polyphenol profiling was carried out by a liquid chromatography–electrospray ionisation-mass spectrometry (LC–ESI-MS) with orbitrap as a mass analyser in both positive and negative ion modes, and polyphenols in aglycone forms were quantified by HPLC–ECD. Five different varieties of black soybeans (G. max) contained 249–405 μg/g dry wt of γ-tocopherol and 6.76–14.98 μg/g dry wt of lutein. Major polyphenols in black soybeans (G. max) were daidzein (193–288 μg/g dry wt) and genistein (145–223 μg/g dry wt), mainly present as glucosides and acetyl glucosides. No significant decrease was found in total phenols of black soybeans (G. max) stored at room temperature, 4 or −80 °C for 14 months. On the other hand, lutein and γ-tocopherol degraded significantly within a month of storage at room temperature (p < 0.01), whereas they remained stable up to 6 months at 4 °C and up to 14 months at −80 °C. The current study indicates that black soybeans (G. max) are rich source of γ-tocopherol and phenols (isoflavones, flavonols, flavan-3-ols, proanthocyanidins and anthocyanin) and that the levels vary depending upon varieties. In addition, storage at low temperature is recommended to reduce the loss of fat-soluble phytochemicals in black soybeans (G. max) over an extended period of time. 相似文献