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排序方式: 共有576条查询结果,搜索用时 15 毫秒
101.
Jason Stafford Ed Walsh Vanessa Egan 《International Journal of Heat and Mass Transfer》2012,55(7-8):1970-1985
Centrifugal fans are often integrated into thermal management solutions for a range of applications. Consequently, centrifugal fan designs can be subjected to varying environmental conditions, many of which can alter fan performance characteristics and ultimately influence the heat transfer performance of the cooling solution. Global cross flows are a commonly encountered practical operating condition, particularly in the cooling of electronics. Air-cooled electronic enclosures often incorporate miniature centrifugal fans to maintain reliable component operating temperatures at a local level, while larger system level fans are used to simultaneously control the ambient temperature within the enclosure. This type of operating condition has been investigated by introducing a uniform crossing air flow above a centrifugal fan inlet. Two scaled miniature centrifugal fan designs were selected to fundamentally assess the influence on local velocity field and heat transfer performance. This was achieved experimentally using Particle Image Velocimetry, and a combined infrared and heated-thin-foil technique developed for the accurate measurement of local heat transfer coefficients. the introduction of a crossing air flow above the fan inlet indirectly reduced both the local and global thermal performance of the centrifugal fan, and the resultant distorted inflow shifted the surface heat transfer distribution at the fan outlet from an axisymmetric to asymmetric profile. However, strategic positioning of components relative to a centrifugal fan can maintain the average component heat transfer coefficient at a similar level to a case without any cross flow. Results also indicate issues associated with the implementation of miniature centrifugal fan designs into crossing air flow environments, with reductions in thermal performance of over 30% observed. 相似文献
102.
William Eisenstein Gwen Fuertes Soazig Kaam Kimberly Seigel Ed Arens Louise Mozingo 《Building Research & Information》2017,45(8):828-844
This paper quantifies the greenhouse gas (GHG) emissions co-benefits associated with water, waste and transportation usage in certified green commercial office buildings in California. The study compares the measured values of water, waste and transportation usage self-reported by office buildings certified under the Leadership in Energy and Environmental Design rating system for Existing Building Operations and Maintenance (LEED EBOM) to baseline values of conventional California office buildings. The green buildings in the LEED EBOM dataset produced 50% less GHGs due to water consumption than baseline buildings, 48% less due to solid waste management, and 5% less due to transportation. If applied to the entire California office building stock, performance typical of the certified green buildings would save 730,038?MgCO2e/yr (metric tonnes) from transportation, 87,601?MgCO2e/yr from water, and 45,280?MgCO2e/yr from waste, for a total potential savings of about 862,920?MgCO2e/yr relative to conventional construction. In addition, buildings earning additional credits for specified performance thresholds for water and waste in the LEED EBOM code attained performance levels even higher than required by the code provisions, suggesting that such code provisions in other contexts may help incentivize larger GHG emissions reductions than anticipated. Specific recommendations are made for building standards and certification schemes. 相似文献
103.
Liang Han Yubo Guo Haojun Ma Xi He Yuyang Kuang Ning Zhang Ed Lim Wenjiang Zhou Chen Jiang 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(21):3647-3658
Targeting therapy of tumors in their early stages is crucial to increase the survival rate of cancer patients. Currently most drug‐delivery systems target the neoplasia through the tumor‐associated receptors overexpressed on the cancer cell membrane. However, the expression of these receptors on normal cells and tissues is inevitable, which leads to unwanted accumulation and side effects. Characteristics of the tumor microenvironment, such as acidosis, are pervasive in almost all solid tumors and can be easily accessed. It is shown that the different extracellular pH value can be used to activate/inactivate the receptor‐mediated endocytosis on tumor/normal cells. This idea is implemented by conjugating a shielding molecule at the terminus of a receptor‐specific ligand via a pH‐sensitive hydrazone bond. The acid‐activated detachment of the shielding molecule and enhanced tumor/background accumulation ratio are demonstrated. These results suggest that acid active receptor‐specific peptide ligand‐modified tumor‐targeting delivery systems have potential use in the treatment of tumors. 相似文献
104.
Nanofluids comprised of silicon dioxide (SiO2) nanoparticles suspended in a 60:40 (% by weight) ethylene glycol and water (EG/water) mixture were investigated for their heat transfer and fluid dynamic performance. First, the rheological properties of different volume percents of SiO2 nanofluids were investigated at varying temperatures. The effect of particle diameter (20 nm, 50 nm, 100 nm) on the viscosity of the fluid was investigated. Subsequent experiments were performed to investigate the convective heat transfer enhancement of nanofluids in the turbulent regime by using the viscosity values measured. The experimental system was first tested with EG/water mixture to establish agreement with the Dittus-Boelter equation for Nusselt number and with Blasius equation for friction factor. The increase in heat transfer coefficient due to nanofluids for various volume concentrations has been presented. Pressure loss was observed to increase with nanoparticle volume concentration. It was observed that an increase in particle diameter increased the heat transfer coefficient. Typical percentage increases of heat transfer coefficient and pressure loss at fixed Reynolds number are presented. 相似文献
105.
Sa’Ed M. Salhieh 《The International Journal of Advanced Manufacturing Technology》2008,39(5-6):599-611
Product developers usually rely on their experience and knowledge during the design process to generate manufacturable products that can fulfill the required functions. Product developers make various decisions during the course of developing a modular product that affect the functional, physical, and operational structures, which either enhance or reduce the manufacturability of the products. This paper proposes constructing manufacturing response models by modeling the behavior of the manufacturability as a response to the series of decisions made during the design process. The manufacturability response models are mathematical models used to relate the product manufacturability to the different metrics used to quantify the results of the design decisions made during the development life cycle. Decisions made during the design process includes specifying the product functionalities needed to meet customer needs, the physical components capable of delivering the required functionalities, and the manufacturing processes needed to produce the physical components. Manufacturing response models can be used by product developers to predict the effect of the decisions made during the course of developing a modular product on the final modular product manufacturability. Furthermore, this paper demonstrates the construction of the manufacturing response models and their usage in new product design by using an illustrative example. 相似文献
106.
Hepatic and Adipose Tissue Depot-Specific Changes in Lipid Metabolism in Late-Onset Obese (LOB) Rats
Transgenic Late-onset OBesity (LOB) rats slowly develop a male-specific, autosomal dominant, obesity phenotype with a specific
increase in peri-renal white adipose tissue (WAT) depot and preserved insulin sensitivity (Bains et al. in Endocrinology 145:2666–2679,
2004). To better understand the remarkable phenotype of these rats, the lipid metabolism was investigated in male LOB and non-transgenic
(NT) littermates. Total plasma cholesterol (C) levels were normal but total plasma triacylglycerol (TAG) (2.8-fold) and hepatic
TAG content (25%) was elevated in LOB males. Plasma VLDL-C and VLDL-TAG levels were higher while plasma apoB levels were 60%
lower in LOB males. Increased hepatic TAG secretion explained the increased VLDL levels in LOB males. The hepatic gene expression
of FAS, SCD-1, mitochondrial (mt)GPAT, and DGAT2 was up-regulated in both old obese and young non-obese LOB rats. Lipoprotein
lipase (LPL) activity in heart and epididymal white adipose tissue (WAT) was unchanged, while LPL activity was increased in
peri-renal WAT (30%) and decreased in soleus muscle (40%). Moreover, FAS, SCD-1 and DGAT2 gene expression was increased in
peri-renal, but not in epididymal WAT. Basal lipolysis was reduced or unchanged and β-adrenergic stimulated lipolysis was
reduced in WAT from both old obese and young non-obese LOB rats. To summarize, the obese phenotype of LOB male rats is associated
with increased hepatic TAG production and secretion, a shift in LPL activity from skeletal muscle to WAT, reduced lipolytic
response in WAT depots and a specific increase in expression of genes responsible for fatty acid and TAG synthesis in the
peri-renal depot.
F. Frick and R. Hume contributed equally to this work. 相似文献
107.
108.
Bezanson G Delaquis P Bach S McKellar R Topp E Gill A Blais B Gilmour M 《Journal of food protection》2012,75(3):480-487
Little is known about the influence of abiotic factors such as climate and soil chemistry on the survival of Escherichia coli O157:H7 in field lettuce. We applied a nalidixic acid-resistant derivative of strain ATCC 700728 to field-grown romaine lettuce in two regions in Canada characterized by large variances in soil type and climate. Surviving populations in soil and on lettuce leaves were estimated on sorbitol MacConkey agar supplemented with nalidixic acid. Data were fitted with the Weibull decline function to permit comparison of decay rates in the two experimental sites. E. coli O157:H7 populations fell from 10? to <102 CFU/g on leaves, and <103 CFU/g in soil within 7 days after inoculation. Analysis revealed there was no significant difference between decay rates at the two experimental sites in either environment. The results of this study suggest that the inherent ecological fitness of E. coli O157:H7 ATCC 700728 determines the extent of survival in the production environment. 相似文献
109.
Furuno S Foss S Wild E Jones KC Semple KT Harms H Wick LY 《Environmental science & technology》2012,46(10):5463-5470
To cope with heterogeneous subsurface environments mycelial microorganisms have developed a unique ramified growth form. By extending hyphae, they can obtain nutrients from remote places and transport them even through air gaps and in small pore spaces, repectively. To date, studies have been focusing on the role that networks play in the distribution of nutrients. Here, we investigated the role of mycelia for the translocation of nonessential substances, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. We show that the hyphae of the mycelial soil oomycete Pythium ultimum function as active translocation vectors for a wide range of PAHs. Visualization by two-photon excitation microscopy (TPEM) demonstrated the uptake and accumulation of phenanthrene (PHE) in lipid vesicles and its active transport by cytoplasmic streaming of the hyphae ('hyphal pipelines'). In mycelial networks, contaminants were translocated over larger distances than by diffusion. Given their transport capacity and ubiquity, hyphae may substantially distribute remote hydrophobic contaminants in soil, thereby improving their bioavailability to bacterial degradation. Hyphal contaminant dispersal may provide an untapped potential for future bioremediation approaches. 相似文献
110.
Le Huy; Oh In-Sue; Robbins Steven B.; Ilies Remus; Holland Ed; Westrick Paul 《Canadian Metallurgical Quarterly》2011,96(1):113
The relationships between personality traits and performance are often assumed to be linear. This assumption has been challenged conceptually and empirically, but results to date have been inconclusive. In the current study, we took a theory-driven approach in systematically addressing this issue. Results based on two different samples generally supported our expectations of the curvilinear relationships between personality traits, including Conscientiousness and Emotional Stability, and job performance dimensions, including task performance, organizational citizenship behavior, and counterproductive work behaviors. We also hypothesized and found that job complexity moderated the curvilinear personality–performance relationships such that the inflection points after which the relationships disappear were lower for low-complexity jobs than they were for high-complexity jobs. This finding suggests that high levels of the two personality traits examined are more beneficial for performance in high- than low-complexity jobs. We conclude by discussing the implications of these findings for the use of personality in personnel selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献