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排序方式: 共有272条查询结果,搜索用时 15 毫秒
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S Nava L Bocconi G Zuliani A Kustermann U Nicolini 《Canadian Metallurgical Quarterly》1996,87(6):975-980
OBJECTIVE: To construct reference ranges for fetal pH, oxygen pressure (PO2), and hematologic and biochemical blood constituents, which can be used to analyze changes with gestation and differences with maternal values, thus elucidating some aspects of fetal biology and the effects of the maternal and placental environments. METHODS: We assayed venous pH, PO2, hematocrit, glucose, uric acid, urea, creatinine, total protein, total and direct bilirubin, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, alkaline phosphatase, lactic dehydrogenase, amylase, pseudocholinesterase, creatine kinase, triglycerides, and cholesterol concentrations in 157 fetuses and 134 mothers who underwent fetal blood sampling from 18 to 37 weeks' gestation. None of the fetuses was infected or had chromosomal, hematologic, or hormonal abnormalities. RESULTS: All the variables analyzed were similar in fetuses sampled at the placental cord insertion (n = 125) or at the intrahepatic vein (n = 32). Maternal and fetal concentrations of glucose (r = 0.79, P < .001), urea (r = 0.96, P < .001), creatinine (r = 0.83, P < .001), and uric acid (r = 0.94, P < .001) correlated significantly, and their differences exhibited significant changes: the maternal-fetal differences of glucose and urea increased, whereas those of uric acid and creatinine decreased with advancing gestation. Fetal pH and PO2 decreased with gestational age, whereas hematocrit increased, similar to what has been described previously. All of the other variables, with the exception of amylase and cholesterol, changed significantly during the investigated period of pregnancy. Gestational age explained at least 40% of the variance in values of fetal total protein, pseudocholinesterase, alanine aminotransferase, creatine kinase, and triglycerides, but only 3-25% of the variation in the remainder. Most enzymes were higher in the fetus than in the maternal circulation, and all except alkaline phosphatase increased with gestational age. The maternal-fetal glucose difference correlated significantly with hematocrit, pH, and PO2, independent of gestational age and independent of each other. CONCLUSION: With the exception of aspartate aminotransferase, all of the analyzed fetal variables were different from the maternal values, and most changed with gestational age. The mechanisms leading to these fetal specificities remain mostly uncertain, but the provision of reference ranges for several blood constituents may be useful in the differential diagnosis of fetal disease. 相似文献
3.
F. Nava G. Wagner C. Lanzieri P. Vanni E. Vittone 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2003,510(3):273-280
The development of SiC minimum ionising particle (MIP) detectors imposes severe constrains in the electronic quality and the thickness of the material due to the relatively high value of the energy required to produce an electron–hole pair in this material by MIP against the value for Si. In this work, particle detectors were made using semiconductor epitaxial undoped n-type 4H-SiC as the detection medium. The thickness of the epilayer is on the order of 40 μm and the detectors are realised by the formation of a nickel silicide on the silicon surface of the epitaxial layer (Schottky contact) and of the ohmic contact on the back side of 4H-SiC substrate. The low doping concentration (6×1013 cm−3) of the epilayer allows the detector to be totally depleted at relatively low reverse voltages (100 V). We present experimental data on the charge collection properties by using 5.486 MeV -particles impinging on the Schottky contact. A 100% charge collection efficiency (CCE) is demonstrated for reverse voltages higher than the one needed to have a depletion region equal to the -particle extrapolated range in SiC. The diffusion contribution of the minority change carriers to CCE is pointed out. By comparing measured CCE values to the outcomes of drift–diffusion simulation, values are inferred for the hole lifetime within the neutral region of the charge carrier generation layer. 相似文献
4.
H. Nava C. Ornelas A. Aguilar G. Berhault S. Fuentes G. Alonso 《Catalysis Letters》2003,86(4):257-265
Unsupported cobalt-molybdenum sulfide catalysts were prepared from bimetallic CoMo alkyl precursors by in situ activation during the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The bimetallic CoMo precursors were prepared by reaction of tetraalkylammonium thiomolybdate salts, (R4N)2MoS4 (where R = H, methyl, butyl, pentyl or hexyl), with CoCl2 in water at a Co/Mo molar ratio of 0.3. These catalysts exhibit a Swiss-cheese-like morphology, high surface areas (from 52 up to 320 m2/g), high content of carbon (C/Mo = 2.2-3.3) and type IV adsorption-desorption isotherms of nitrogen. The in situ activation of these tetraalkylammonium thiobimetalate precursors leads to a mesoporous structure with pore size ranging from 2 to 4.5 nm. X-ray diffraction showed that the structure of unsupported cobalt-molybdenum sulfide catalysts corresponds to a poorly crystalline structure characteristic of 2H-MoS2 with low-stacked layers. The nature of the alkyl group strongly affects both the surface area and the HDS activity. The catalytic activity is strongly enhanced when using carbon-containing precursors; the CoMo catalysts prepared by in situ activation of Co/[N(C4H9)4]2MoS4 presents the highest HDS activity. The highest surface area of the catalysts was observed for the CoMo catalyst formed from Co/[N(C6H13)4N]2MoS4. 相似文献
5.
I am presenting a new design for the head sub-system of the humanoid robot iCub. ICub is a humanoid robot platform that has been conceived as a result of the development of the European Project RobotCub. Mechanical problems of the current head sub-system of iCub robot have been studied in order to figure out improvements for a new design. The feasibility of the new design has been checked through dynamic simulations of the head operations. The successful results have shown plots with curve evolutions of smooth shapes and suitable values of important kinematic and dynamic parameters of the head structure. 相似文献
6.
Matteo Giovarelli Francesca Arnaboldi Silvia Zecchini Laura Brigida Cornaghi Ambra Nava Michele Sommariva Emilio Giuseppe Ignazio Clementi Nicoletta Gagliano 《International journal of molecular sciences》2022,23(15)
Duchenne muscular dystrophy (DMD) is a rare genetic disease leading to progressive muscle wasting, respiratory failure, and cardiomyopathy. Although muscle fibrosis represents a DMD hallmark, the organisation of the extracellular matrix and the molecular changes in its turnover are still not fully understood. To define the architectural changes over time in muscle fibrosis, we used an mdx mouse model of DMD and analysed collagen and glycosaminoglycans/proteoglycans content in skeletal muscle sections at different time points during disease progression and in comparison with age-matched controls. Collagen significantly increased particularly in the diaphragm, quadriceps, and gastrocnemius in adult mdx, with fibrosis significantly correlating with muscle degeneration. We also analysed collagen turnover pathways underlying fibrosis development in cultured primary quadriceps-derived fibroblasts. Collagen secretion and matrix metalloproteinases (MMPs) remained unaffected in both young and adult mdx compared to wt fibroblasts, whereas collagen cross-linking and tissue inhibitors of MMP (TIMP) expression significantly increased. We conclude that, in the DMD model we used, fibrosis mostly affects diaphragm and quadriceps with a higher collagen cross-linking and inhibition of MMPs that contribute differently to progressive collagen accumulation during fibrotic remodelling. This study offers a comprehensive histological and molecular characterisation of DMD-associated muscle fibrosis; it may thus provide new targets for tailored therapeutic interventions. 相似文献
7.
To speed up data‐intensive programs, two complementary techniques, namely nested loops parallelization and data locality optimization, should be considered. Effective parallelization techniques distribute the computation and necessary data across different processors, whereas data locality places data on the same processor. Therefore, locality and parallelization may demand different loop transformations. As such, an integrated approach that combines these two can generate much better results than each individual approach. This paper proposes a unified approach that integrates these two techniques to obtain an appropriate loop transformation. Applying this transformation results in coarse grain parallelism through exploiting the largest possible groups of outer permutable loops in addition to data locality through dependence satisfaction at inner loops. These groups can be further tiled to improve data locality through exploiting data reuse in multiple dimensions. 相似文献
8.
Nava Pliskin 《Information Systems Management》2013,30(2):51-58
Microcomputer technology has matured to a point at which its successful assimilation depends more on the proper management of personnel and less on the features of the technology. This article presents a case study that demonstrates how lead users can be identified and recruited to provide a support infrastructure to peers throughout the initiation stage within the organization. The article recommends that managers of microcomputer technology develop an understanding of different user types and apply adaptive human resource management practices 相似文献
9.
Jin Pan Julian Tang Miguela Caniza Jean-Michel Heraud Evelyn Koay Hong Kai Lee Chun Kiat Lee Yuguo Li Alejandra Nava Ruiz Carlos Francisco Santillan-Salas Linsey C. Marr 《Indoor air》2021,31(6):2281-2295
The incidence of several respiratory viral infections has been shown to be related to climate. Because humans spend most of their time indoors, measures of indoor climate, rather than outdoor climate, may be better predictors of disease incidence and transmission. Therefore, understanding the relationship between indoor and outdoor climate will help illuminate their influence on the seasonality of diseases caused by respiratory viruses. Indoor-outdoor relationships between temperature and humidity have been documented in temperate regions, but little information is available for tropical regions, where seasonal patterns of respiratory viral diseases differ. We have examined indoor-outdoor correlations of temperature, relative humidity (RH), and absolute humidity (AH) over a 1-year period in each of seven tropical cities. Across all cities, the average monthly indoor temperature was 25 ± 3°C (mean ± standard deviation) with a range of 20–30°C. The average monthly indoor RH was 66 ± 9% with a range of 50–78%, and the average monthly indoor AH was 15 ± 3 g/m3 with a range of 10–23 g/m3. Indoor AH and RH were linearly correlated with outdoor AH when the air conditioning (AC) was off, suggesting that outdoor AH may be a good proxy of indoor humidity in the absence of AC. All indoor measurements were more strongly correlated with outdoor measurements as distance from the equator increased. Such correlations were weaker during the wet season, especially when AC was in operation. These correlations will provide insight for assessing the seasonality of respiratory viral infections using outdoor climate data, which is more widely available than indoor data, even though transmission of these diseases mainly occurs indoors. 相似文献
10.