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61.
Riboflavin Photosensitized Singlet Oxygen Oxidation of Vitamin D 总被引:2,自引:0,他引:2
Samples containing various levels of vitamin D and riboflavin, with and without ascorbic acid or a-tocopherol were prepared in a model system. Samples were stored in the light or in the dark at 45®C for up to 8 h. Headspace oxygen was determined by gas chromatography with thermal conductivity detection. Oxidation of vitamin D was not observed in samples without riboflavin stored in the light nor in samples with riboflavin stored in the dark. Vitamin D with riboflavin was oxidized under light. α-Tocopherol quenched singlet oxygen at a rate of 2.52 × 108 M-1 sec-1 , whereas ascorbic acid quenched singlet oxygen at a rate of 2.23 × 107 M-1 sec-1 . 相似文献
62.
TYTUS BERNAS † DAVID BARNES# ELIKPLIMI K. ASEM‡ J. PAUL ROBINSON† & BARTEK RAJWA† 《Journal of microscopy》2007,226(2):163-174
Standardization and calibration of optical microscopy systems have become an important issue owing to the increasing role of biological imaging in high‐content screening technology. The proper interpretation of data from high‐content screening imaging experiments requires detailed information about the capabilities of the systems, including their available dynamic range, sensitivity and noise. Currently available techniques for calibration and standardization of digital microscopes commonly used in cell biology laboratories provide an estimation of stability and measurement precision (noise) of an imaging system at a single level of signal intensity. In addition, only the total noise level, not its characteristics (spectrum), is measured. We propose a novel technique for estimation of temporal variability of signal and noise in microscopic imaging. The method requires registration of a time series of images of any stationary biological specimen. The subsequent analysis involves a multi‐step process, which separates monotonic, periodic and random components of every pixel intensity change in time. The technique allows simultaneous determination of dark, photonic and multiplicative components of noise present in biological measurements. Consequently, a respective confidence interval (noise level) is obtained for each level of signal. The technique is validated using test sets of biological images with known signal and noise characteristics. The method is also applied to assess uncertainty of measurement obtained with two CCD cameras in a wide‐field microscope. 相似文献
63.
THE EFFECTS OF TURGOR PRESSURE ON PUNCTURE AND VISCOELASTIC PROPERTIES OF TOMATO TISSUE 总被引:1,自引:0,他引:1
ROBERT L. JACKMAN ALEJANDRO G. MARANGONI DAVID W. STANLEY 《Journal of texture studies》1992,23(4):491-505
The effects of turgor pressure on puncture and viscoelastic properties of mature-green tomato pericarp were examined using tissue discs soaked in a range of osmotica (0.0–0.6 M mannitol) for at least 36 h at 4C. Turgor pressure was estimated from the osmotic potential of soaking solutions that induced incipient plasmolysis. Based on volume changes, the osmotic potential and turgor pressure of fresh tissue were estimated to be −0.56 ± 0.08 MPa and 0.20 MPa, respectively. However, puncture and viscoelastic properties corresponded to a turgor pressure of 0.15 MPa. The discrepancy between calculated and actual turgor pressures was attributed to the presence of apoplastic solutes. The data from this study revealed a general increase in cell wall stress, strain and elasticity with increasing turgor. With increases in turgor above that of untreated tissue both wall extensibility and elasticity became limiting and thus cell wall stiffness increased. Conversely, a decrease in turgor below that of untreated tissue led to an increase in viscoelasticity. Increases in bioyield and pseudoplastic bioyield strains with a variation in turgor from that of untreated tissue were consistent with cell debonding as a dominant mechanism of tomato tissue bioyielding. The reduced failure force, deformation and firmness with increasing turgor were consistent with cell rupture as a predominant mechanism of failure of mature-green tomato pericarp tissue. 相似文献
64.
DAVID SEPÜLVEDA GUADALUPE OLIVAS JOSE-JUAN RODRIGUEZ HEIDI WARNER STEPHANIE CLARK GUSTAVO BARBOSA-CÁNOVAS 《Journal of Food Processing and Preservation》2003,27(3):227-242
Changes in specific physico-chemical and sensory attributes as well as acceptability of beefsteak and beef stew Meal-Ready-to-Eat (MRE) components packed under different headspace levels (10, 20, 30 and 40 cm3 ) and stored at selected temperatures of 4, 27 and 38C (40, 80 and 100F) were evaluated over a six month period. No significant changes in microbial counts, pH, residual oxygen, color, hardness and oxidation occurred in retort-packed beefsteak or beef stew. Unlike beefsteak, beef stew received acceptable scores by consumers during all six months of analysis. Consumers' lack of familiarity with beefsteak may have negatively influenced product acceptability. Beefsteak and beef stew acceptability and specific attributes, particularly moistness and firmness, were detrimentally affected by high storage temperatures. Headspace may be increased to 40 cm3 without significant detrimental effects on product quality and acceptability of beefsteak or beef stew. 相似文献
65.
Formal Aspects of Computing are dedicated to Professor Rod Burstall, and, as a collection of papers, memoirs and incidental pieces, form a Festschrift
for Rod. The contributions are made by some of the many who know Rod and have been in uenced by him. The research papers included
here represent some of the areas in which Rod has been active, and the editors thank their colleagues for agreeing to contribute
to this Festschrift. 相似文献
66.
Markets and Hierarchies and (Mathematical) Economic Theory 总被引:4,自引:0,他引:4
Over the past decade transaction-cost economics has been partiallytranslated in the more mathematical language of game theory,and understanding of the costs of transactions has been deepened,refined and extended. But the translation is incomplete: a greatdeal of human behaviour is missed, and doing game theory withmore life-like models of individuals will bring theory closerto phenomena. Transaction-cost economics, particulary the economicsof relational contracts, provides a major arena for these developments,since the important issues of bounded rationality and individualbehavior are central to the topic. 相似文献
67.
PROCESSING AND QUALITY EVALUATION OF WHOLE CANNED 'DWARF' GOLDEN APPLES (SPONDIAS CYTHEREA) 总被引:1,自引:0,他引:1
DAVID RAMSUNDAR EDWARD COMISSIONG NEELA BADRIE GAIL S.H. BACCUS-TAYLOR JOHN SPENCE 《Journal of food quality》2002,25(1):13-25
‘Dwarf’ golden apples (Spondias cytherea) were canned in sucrose syrup of either 30 d?Brix (L) or 40 d?Brix (H). Processing was either by hot filling (HF) of syrup at 92C in filled cans or by steam‐exhausting (SE) of the filled cans at 85C for 12–14 min, followed by processing at 100C for 20 min (W20) or 30 min (W30). Sensory evaluation of commercial sterile products, SE‐LW30 and SE‐LW30 indicated there were no differences (P < 0.05) in appearance, color, taste, aroma and texture. Overall scores indicated that fruits in syrup were liked definitely to like slightly. Panelists indicated that they might or definitely will purchase the products. Fruits in 40 d?Brix syrup were firmer than in 30 d?Brix syrup. By week 8 of storage at 28–30C, pH was stable between 3.6–3.7, and ‘cut‐out’d?Brix of syrup for LW30 and HW30 products was 24.0 – 24.5 and 28.5, respectively. 相似文献
68.
Fine-particle beta sodium ferrite (β-NaFeO2 ), rather than α-Fe2 O3 , may be responsible for superparamagnetic behavior in a glass of composition (in mole fractions) 0.37Na2 O-0.26Fe2 O3 -0.37SiO2 . The 700°C isothermal section of the phase diagram of the Na2 O-Fe2 O3 -SiO2 system is given, showing a three-phase field bounded by Na2 SiO3 -NaFeO2 -Fe2 O3 ; there is no evidence for the existence (at 700°C) of compounds of molar composition 6Na2 O-4Fe2 O3 -5SiO2 or 2Na2 O-Fe2 O3 -SiO2 . The Moessbauer spectrum of β-NaFeO2 has an internal magnetic field of 487 kOe at room temperature. 相似文献
69.
Comparison of three‐dimensional analysis and stereological techniques for quantifying lithium‐ion battery electrode microstructures 下载免费PDF全文
OLUWADAMILOLA O. TAIWO DONAL P. FINEGAN DAVID S. EASTWOOD JULIE L. FIFE LEON D. BROWN JAWWAD A. DARR PETER D. LEE DANIEL J.L. BRETT PAUL R. SHEARING 《Journal of microscopy》2016,263(3):280-292
Lithium‐ion battery performance is intrinsically linked to electrode microstructure. Quantitative measurement of key structural parameters of lithium‐ion battery electrode microstructures will enable optimization as well as motivate systematic numerical studies for the improvement of battery performance. With the rapid development of 3‐D imaging techniques, quantitative assessment of 3‐D microstructures from 2‐D image sections by stereological methods appears outmoded; however, in spite of the proliferation of tomographic imaging techniques, it remains significantly easier to obtain two‐dimensional (2‐D) data sets. In this study, stereological prediction and three‐dimensional (3‐D) analysis techniques for quantitative assessment of key geometric parameters for characterizing battery electrode microstructures are examined and compared. Lithium‐ion battery electrodes were imaged using synchrotron‐based X‐ray tomographic microscopy. For each electrode sample investigated, stereological analysis was performed on reconstructed 2‐D image sections generated from tomographic imaging, whereas direct 3‐D analysis was performed on reconstructed image volumes. The analysis showed that geometric parameter estimation using 2‐D image sections is bound to be associated with ambiguity and that volume‐based 3‐D characterization of nonconvex, irregular and interconnected particles can be used to more accurately quantify spatially‐dependent parameters, such as tortuosity and pore‐phase connectivity. 相似文献
70.
CCD型束流截面探测器的主要特点是使用电荷耦合器件做传感器,用束流同步光中的可见光成份做为信号源。该探测器同时具有模拟量和数字量两种输出,工作周期短,速度高,不影响束团粒子寿命,在电子储存环物理运行中,是一种有效的探测设备。 相似文献