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71.
Stuart W. Styles Charles M. Burt Franklin Gaudi Sierra Orvis 《Canadian Metallurgical Quarterly》2008,134(3):292-297
Emitter pressures and flow rates were systematically and extensively sampled in one drip and one microspray field. The data distributions are presented. The accuracy of rapid (limited samples) evaluation pressure sampling procedures was found to be quite good if the pressure distribution was systematic, but erroneous if the pressure distribution throughout a field was random. A simple mathematical combination of two nonuniformity components (due to pressure differences, and other causes of flow variation) provided a better estimate of overall system distribution uniformity than more complex mathematics. 相似文献
72.
Kinetics of free and glycosylated B6 vitamers,thiamin and riboflavin during germination of pea seeds
The effect of germination on the free and glycosylated B6 vitamers (pyridoxine, pyridoxal, pyridoxamine and glycosylated pyridoxine), thiamin and riboflavin content in pea seed (Pisum sativum L, var Esla) was investigated. In raw peas, the total vitamin B6 content (sum of all vitamers expressed as pyridoxine) was 2.183 mg kg−1 DM. Pyridoxine was found to be the predominant B6 vitamer, while only a little amount of glycosylated pyridoxine, the vitamer with the lowest boiavailability, was observed. Thiamin and riboflavin content in raw peas was found to be 7.614 and 2.110 mg kg −1 DM, respectively. After 6 days of germination, carried out at 20°C, in the dark and with daily rinsing, a significant increase of the total vitamin B6 content, mainly due to the increase of glycosylated pyridoxine, was observed. The content of pyridoxal and riboflavin increased in peas 7.5 and 2 times, respectively, whereas pyridoxine, pyridoxamine and thiamin decreased by 83, 24 and 25%, respectively, at the end of the experiment. Results obtained for these vitamins during pea germination were fitted to modelling curves in order to predict vitamin content for different germination periods. © 1999 Society of Chemical Industry 相似文献
73.
74.
Development of engineered cementitious composites with limestone powder and blast furnace slag 总被引:1,自引:1,他引:0
Jian Zhou Shunzhi Qian M. Guadalupe Sierra Beltran Guang Ye Klaas van Breugel Victor C. Li 《Materials and Structures》2010,43(6):803-814
Nowadays limestone powder and blast furnace slag (BFS) are widely used in concrete as blended materials in cement. The replacement
of Portland cement by limestone powder and BFS can lower the cost and enhance the greenness of concrete, since the production
of these two materials needs less energy and causes less CO2 emission than Portland cement. Moreover, the use of limestone powder and BFS improves the properties of fresh and hardened
concrete, such as workability and durability. Engineered cementitious composites (ECC) is a class of ultra ductile fiber reinforced
cementitious composites, characterized by high ductility, tight crack width control and relatively low fiber content. The
limestone powder and BFS are used to produce ECC in this research. The mix proportion is designed experimentally by adjusting
the amount of limestone powder and BFS, accompanied by four-point bending test and uniaxial tensile test. This study results
in an ECC mix proportion with the Portland cement content as low as 15% of powder by weight. This mixture, at 28 days, exhibits
a high tensile strain capacity of 3.3%, a tight crack width of 57 μm and a moderate compressive strength of 38 MPa. In order
to promote a wide use of ECC, it was tried to simplify the mixing of ECC with only two matrix materials, i.e. BFS cement and
limestone powder, instead of three matrix materials. By replacing Portland cement and BFS in the aforementioned ECC mixture
with BFS cement, the ECC with BFS cement and limestone powder exhibits a tensile strain capacity of 3.1%, a crack width of
76 μm and a compressive strength of 40 MPa after 28 days of curing. 相似文献
75.
Cultivation of Solanum tuberosum in a former mining district for a safe human consumption integrating simulated digestion
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76.
Sánchez-Muñoz S Gómez-Ruiz S Pérez-Quintanilla D Morante-Zarcero S Sierra I Prashar S Paschke R Kaluđerović GN 《ChemMedChem》2012,7(4):670-679
Dehydrated MCM-41 (S1) was functionalized under nitrogen with 3-chloropropyltriethoxysilane (CPTS) and 3-aminopropyltriethoxysilane (APTS) by grafting in toluene at 80 °C over 48 h to give the corresponding materials S2 and S3, respectively. Subsequently, S2 and S3 were suspended in methanol and reacted in a nitrogen atmosphere with betulinic acid (BA) for 48 h at 65 °C (in the presence of the triethylamine of S2) to give the BA-functionalized materials S4 and S5. All materials studied were characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear MAS NMR spectroscopy, thermogravimetry, UV spectroscopy, IR, SEM, and TEM. To study the release of BA, S4 and S5 were suspended in solutions simulating various body pH conditions (pH 7.4, 5.5, and 3.0). Results of the quantification of BA release by HPLC for S4 show a pH-dependent and very slow BA release following a logarithmic tendency, while S5 behaves differently, also pH-dependent but, in this case, fast release of BA which requires only days for total release of the therapeutic compound. In addition, the cytotoxic activity of all synthesized materials against various cancer cell lines was studied. The results show the absence of an antiproliferative effect on the surfaces without BA S1-S3, while an antiproliferative effect was observed with S4 and S5 and was attributed to the release of BA in the medium. 相似文献
77.
Isabel Sierra Concepción Vidal-Valverde Halina Kozlowska 《European Food Research and Technology》1998,206(2):126-129
Seeds of yellow pea lupin (Lupinus luteus L., cv. Juno), pea (Pisum sativum L., cv. Ergo) and faba bean (Vicia faba sp. minor Harz., cv. Tibo) were harvested at different stages of seed maturity. Changes in thiamin and riboflavin levels
during growth and maturation were studied. The results obtained showed that thiamin and riboflavin were found in high abundance
early in the development of lupins and peas, but that their content decreased during maturation. The thiamin content of faba
bean seeds increased from 33 to 47 days after flowering (DAF), then a decrease was observed until 61 DAF; however, no significant
differences between these levels in faba bean seeds harvested from 61 to 89 DAF were found. The riboflavin content of faba
beans increased after 54 DAF, and no significant changes were observed between then and 89 DAF. The thiamin and riboflavin
contents in lupin, pea and faba bean seeds during development were fitted to modelling curves in order to predict the vitamin
content at different stages of maturity.
Received: 17 July 1997 相似文献
78.
An experiment was carried out using 7 month old male calves from four different breeds: 10 Spanish Holstein (dairy), 10 Old Brown Swiss (dual purpose), 10 Limousin (fast growth) and 10 Blonde d'Aquitaine (high muscularity). They were all fed concentrate and cereal straw ad libitum. Animals were slaughtered at usual commercial weights for the Spanish market depending on the growth and precocity of each breed (500 kg liveweight at slaughter for Holstein, 550 kg for Old Brown Swiss, 560 kg for Limousin and 620 kg for Blonde d'Aquitaine, with an age between 13 and 15 months). There were significant differences (P<0.001) among breeds in the quantity of total and insoluble collagen in the Longissimus thoracis and lumborum muscle, but collagen solubility was similar (41–44%), except for muscle from the Old Brown Swiss (33%; P<0.001). Overall, breeds specialized for beef production (Limousin and Blonde d'Aquitaine) had lower values for compression and WB in raw and heated meat, respectively, for ageing periods of less than a week. Ageing had a larger effect on myofibrillar tenderness than breed and tended to eliminate the breed effect on textural variables, as well as individual differences within each breed. 相似文献
79.
The effects of cooking viz. pressure-cooking and broiling and storage at 4 °C for six days and -10 °C for 90 days on lipid oxidation and development of cholesterol oxidation products in mutton were studied. Results revealed that cooking of meat significantly increased the total lipids, phospholipids, cholesterol, glycolipids, free fatty acids and glycerides, but they did not change during refrigerated and frozen storage. The TBA values increased on cooking and during storage. However, the values were below the threshold level for rancidity development. The following cholesterol oxidation products were separated by thin layer chromatography cholestanetriol, 7-α-hydroxy cholesterol, 19-hydroxycholesterol, 7-ketocholesterol, cholesterol-α-epoxide, cholesterol-β-epoxide and an unidentified fraction. All these fractions except the unidentified fraction increased on cooking. On refrigerated and even on frozen storage all these fractions increased except the unidentified fraction, which showed a concomitant reduction. The changes in broiled meat were more pronounced compared to pressure-cooked meat. Results clearly indicated that even frozen storage of cooked meat did not prevent the development of cholesterol oxidation products. 相似文献
80.
The seminal report by Hegedus in 1982, showing that alkoxychromium(0) carbenes reacted with imines under bright Colorado sunlight to yield β-lactams, marked the beginning of a key reaction in organometallic chemistry. Very little was known about the mechanism of this reaction. In fact, Hegedus proposed the reversible generation of a chromium-coordinated ketene, which would react with nucleophiles. This coordinated species would show all the advantages of ketenes without their shortcomings, namely, dimerization, formation of undesired adducts, and so forth. The quest for the detection of these species and the pursuit of the mechanism of the photocarbonylation (a reaction exclusive to Cr(0) and Mo(0) carbene complexes, not W(0) carbene complexes) remained unabated over the next 15 years. In fact, all attempts to experimentally determine the mechanism of this useful reaction have been fruitless. At the same time, the photocarbonylation of Cr(0) carbenes matured into a valuable synthetic reaction, allowing access to several families of organic compounds. Unfortunately, reactions other than photocarbonylation remained elusive. We used a combination of experimental and computational methodologies to study the photocarbonylation of Cr(0) carbene complexes and the subsequent reaction of the photogenerated ketenes with nucleophiles. In parallel, we discovered new photochemical processes and succeeded in making photoreactive the so-called "unreactive" W(0) carbene complexes. In this Account, we discuss the disentangling of the mechanisms of these transformations, thereby shedding some light onto the photochemistry of group 6 metal (Fischer) carbene complexes. The original designation of the electronic transitions of group 6 carbene complexes was reassigned, and the photocarbonylation step was analyzed again, resulting in the sequence S(0)-T(1)-S(0), which is far removed from conventional organic photochemistry. The T(1) species is a chromacyclopropanone; its unpaired electrons are primarily localized in the metal fragment and in the former carbene carbon atom. The T(1)-S(0) intersystem crossing occurs with the participation of the solvent through an unusual loose-bolt radiationless mechanism. The photogenerated S(0) species reacts with imines to form the final β-lactams in a mechanism that resembles the organic Staudinger reaction, but here the metal is present during the entire reaction coordinate. The selectivity of these reactions is defined by the nucleophilic attack on the O-bonded metallaketene instead of the subsequent conrotatory ring closure, a distinct departure from the organic reaction. Appropriate modification of the substituents of the carbene ligand or in the coordination sphere of the complex results in new photoprocesses; these include 1,2-metalladyotropic rearrangements as well as α-fragmentations in which W(0) carbene complexes become photoreactive. Moreover, the inclusion of additional metal centers usually results in new reactions, such as the formation of fulvenes by η(5)→ η(3) photoslippage, or in the complete inhibition of the photoreactivity. The photochemistry of group 6 metal-carbene complexes thus offers unexplored territory for pursuing new reactions and reaction mechanisms. 相似文献