全文获取类型
收费全文 | 991篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
综合类 | 1篇 |
化学工业 | 187篇 |
金属工艺 | 19篇 |
机械仪表 | 12篇 |
建筑科学 | 41篇 |
矿业工程 | 3篇 |
能源动力 | 43篇 |
轻工业 | 122篇 |
水利工程 | 5篇 |
石油天然气 | 4篇 |
无线电 | 100篇 |
一般工业技术 | 130篇 |
冶金工业 | 164篇 |
原子能技术 | 4篇 |
自动化技术 | 193篇 |
出版年
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 19篇 |
2019年 | 24篇 |
2018年 | 25篇 |
2017年 | 29篇 |
2016年 | 31篇 |
2015年 | 25篇 |
2014年 | 39篇 |
2013年 | 60篇 |
2012年 | 44篇 |
2011年 | 74篇 |
2010年 | 46篇 |
2009年 | 51篇 |
2008年 | 45篇 |
2007年 | 46篇 |
2006年 | 39篇 |
2005年 | 35篇 |
2004年 | 26篇 |
2003年 | 38篇 |
2002年 | 14篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 68篇 |
1997年 | 37篇 |
1996年 | 26篇 |
1995年 | 16篇 |
1994年 | 17篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1976年 | 7篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有1048条查询结果,搜索用时 15 毫秒
101.
Online error correcting output codes 总被引:1,自引:0,他引:1
Sergio Escalera David Masip Eloi Puertas Oriol Pujol 《Pattern recognition letters》2011,32(3):458-467
This article proposes a general extension of the error correcting output codes framework to the online learning scenario. As a result, the final classifier handles the addition of new classes independently of the base classifier used. In particular, this extension supports the use of both online example incremental and batch classifiers as base learners. The extension of the traditional problem independent codings one-versus-all and one-versus-one is introduced. Furthermore, two new codings are proposed, unbalanced online ECOC and a problem dependent online ECOC. This last online coding technique takes advantage of the problem data for minimizing the number of dichotomizers used in the ECOC framework while preserving a high accuracy. These techniques are validated on an online setting of 11 data sets from UCI database and applied to two real machine vision applications: traffic sign recognition and face recognition. As a result, the online ECOC techniques proposed provide a feasible and robust way for handling new classes using any base classifier. 相似文献
102.
Sixto Malato Julin Blanco Alfonso Vidal Diego Alarcn Manuel I. Maldonado Julia Cceres Wolfgang Gernjak 《Solar Energy》2003,75(4):329-336
The technical feasibility and performance of photocatalytic degradation of four water-soluble pesticides (diuron, imidacloprid, formetanate and methomyl) have been studied at pilot scale in two well-defined systems which are of special interest because natural-solar UV light can be used for them: heterogeneous photocatalysis with titanium dioxide and homogeneous photocatalysis by photo-Fenton. The pilot plant is made up of compound parabolic collectors specially designed for solar photocatalytic applications. The initial concentration tested with imidacloprid, formetanate and methomyl was 50 and 30 mg/l with diuron, and the catalyst concentrations were 200 mg/l and 0.05 mM with TiO2 and iron, respectively. Total disappearance of the parent compounds, 90% mineralisation and toxicity reduction below the threshold (EC50) have been attained with all pesticides tested. All these results have contributed to an evaluation of photocatalytic treatment capacity and comments on the main parameters of TiO2 and Fe separation from the treated water. 相似文献
103.
J García Vidal JM López del Vallado P García de Olalla Rizo I Barnés Vayés JA Caylá Buqueras 《Canadian Metallurgical Quarterly》1998,72(3):197-208
A number of thrombin mutants have been constructed to investigate the role of Trp96 and the beta-insertion loop for the specificity of thrombin. Thrombin(60D) consists of the replacement of the beta-insertion loop (14 amino acid residues from 59 to 63, including a 9-residue insertion at position 60) with the corresponding four residues in trypsin, Tyr-Lys-Ser-Gly; thrombin(GGG) is a smaller loop mutation in which the residues Tyr(60A)Pro(60B)Pro(60C)Trp(60D) Asp(60E)Lys(60F) of the beta-insertion loop were replaced by Gly-Gly-Gly; thrombin(96S) consists of a point mutation Trp96 --> Ser; and thrombin(GGG/96S) is the double mutant incorporating both changes. Thrombin(96S) clots fibrinogen approximately 3 times more slowly than thrombin, with the two beta-insertion loop mutants, thrombin(GGG) and thrombin(GGG/96S), reacting approximately 3000- and 1300-fold more slowly, respectively. The specificity constant kcat/Km for the cleavage of fibrinopeptide A and fibrinopeptide B by thrombin(96S) was 2.6 and 0.35 microM(-1) s(-1), respectively, compared to 10 and 2.5 microM(-1) s(-1) for wild-type recombinant thrombin, respectively. Kinetic constants were determined for the hydrolysis of H-D-phenylalanyl-L-pipecolyl-L-arginine-p-nitroaniline. The Michaelis constant Km increased approximately 6-fold for thrombin(96S) and >200-fold for thrombin(GGG) and thrombin(GGG/96S) when compared to wild-type recombinant thrombin, while the catalytic constant kcat remained approximately the same. All mutants were more susceptible to inhibition by BPTI than wild-type recombinant thrombin. Clearly, the beta-insertion loop is important for thrombin activity. But the mutation of Trp96 --> Ser can compensate somewhat for the loss of binding at the beta-insertion loop. The deletion of the hydrophobic interaction between Trp96 and Pro(60B)Pro(60C) appears to decrease the stability of the beta-insertion loop, thereby causing a decrease in binding efficiency. 相似文献
104.
MP Majowicz MA Costa AM Balaszczuk NA Vidal KA Bombicino CT Arranz 《Canadian Metallurgical Quarterly》1998,19(8):1373-1376
The aim of the present study was to elucidate the role of an IV dose of endothelin-3 (ET-3) (5 ng Kg-1 min-1) on mean arterial pressure (MAP), on diuresis and natriuresis in control and in volume expanded anesthetized rats. A systemic infusion of ET-3 in normal rats (Group I) increased MAP and produced a trend of increasing diuresis, without changes in natriuresis. A 10% body weight expansion (Group II) increased diuresis and natriuresis without changes in MAP. The simultaneous infusion of ET-3 and expansion with saline (Group III) resulted in an increase in MAP, an enhanced diuretic response, and a natriuresis of similar magnitude to that observed in Group II. These results suggest that the diuresis produced by a low dose of exogenous ET-3 in control rats, is independent of sodium excretion. Furthermore, the enhanced diuresis caused by ET-3 during expansion is greater than the addition of ET-3 and expansion effects, suggesting that new mechanisms are triggered in order to maintain volume and salt homeostasis in this state. 相似文献
105.
Diabetes mellitus is one of the diseases with the greatest risk of developing coronary disease (CD), with the estimation of this risk in relation to the general population being from 2 to 4-fold greater. The existence of diabetes worsens the prognosis of CD and thus, postinfarction mortality in these patients is double that observed in non-diabetic patients. Together with the risk factors found in the general population, those of special interest are those derived from diabetes itself, such as hyperglycemia, dyslipemia, coagulation disorders and hyperinsulinemia or insulin resistance. Among these, the most important is probably the hyperglycemia which may contribute to the appearance of CD by different mechanisms such as proteic glycosylation, accumulation of sorbitol, increase in the synthesis of protein kinase C or oxidative stress. It must not be forgotten that an old controversy has recently been brought up suggesting that sulphonylureas may have a certain cardiotoxic effect, probably acting on the potassium channels dependent on ATP. Acute myocardial infarction in diabetic patients carries a greater risk of congestive heart failure, recurrent infarction, arrhythmia and cardiogenic shock, with one of its characteristics being the possibility of being silent when autonomic neuropathy is present. The prognosis of CD may be markedly improved by obtaining optimum glycemic control during the hours following infarction using intensified treatment. Diabetic myocardiopathy as a differentiated nosology responsible for alterations in myocardial contractile function and greater prevalence of heart failure in these patients seems to be clearly demonstrated although its etiology remains unknown. 相似文献
106.
107.
L Millet H Vidal F Andreelli D Larrouy JP Riou D Ricquier M Laville D Langin 《Canadian Metallurgical Quarterly》1997,100(11):2665-2670
Uncoupling protein-2 and -3 (UCP2 and UCP3) are mitochondrial proteins that show high sequence homology with the brown adipocyte-specific UCP1. UCP1 induces heat production by uncoupling respiration from ATP synthesis. UCP2 is widely expressed in human tissues, whereas UCP3 expression seems restricted to skeletal muscle, an important site of thermogenesis in humans. We have investigated the regulation of UCP2 and UCP3 gene expression in skeletal muscle and adipose tissue from lean and obese humans. UCP2 and -3 mRNA levels were not correlated with body mass index (BMI) in skeletal muscle, but a positive correlation (r = 0.55, P < 0.01, n = 22) was found between UCP2 mRNA level in adipose tissue and BMI. The effect of fasting was investigated in eight lean and six obese subjects maintained on a hypocaloric diet (1,045 kJ/d) for 5 d. Calorie restriction induced a similar 2-2.5-fold increase in UCP2 and -3 mRNA levels in lean and obese subjects. To study the effect of insulin on UCP gene expression, six lean and five obese subjects underwent a 3-h euglycemic hyperinsulinemic clamp. Insulin infusion did not modify UCP2 and -3 mRNA levels. In conclusion, the similar induction of gene expression observed during fasting in lean and obese subjects shows that there is no major alteration of UCP2 and -3 gene regulation in adipose tissue and skeletal muscle of obese subjects. The increase in UCP2 and -3 mRNA levels suggests a role for these proteins in the metabolic adaptation to fasting. 相似文献
108.
109.
A Elmgren R Mollicone M Costache C B?rjeson R Oriol J Harrington G Larson 《Canadian Metallurgical Quarterly》1997,272(35):21994-21998
The Lewis alpha(1,3/1,4)-fucosyltransferase, Fuc-TIII, encoded by the FUT3 gene is responsible for the final synthesis of Lea and Leb antigens. Various point mutations have been described explaining the Lewis negative phenotype, Le(a-b-), on erythrocytes and secretions. Two of these, T202C and C314T originally described in a Swedish population, have not been found as single isolated point mutations so far. To define the relative contribution of each of these two mutations to the Lewis negative phenotype, we cloned and made chimeric FUT3 constructs separating the T202C mutation responsible for the amino acid change Trp68 --> Arg, from the C314T mutation leading to the Thr105 --> Met shift. COS-7 cells were transfected and the expression of Fuc-TIII enzyme activity and the presence of Lewis antigens were determined. There was no decrease in enzyme activity nor of immunofluorescence staining on cells transfected with the construct containing the isolated C314T mutation compared with cells transfected with a wild type FUT3 allele control. No enzyme activity nor immunoreactivity for Lewis antigens was detected in FUT3 constructs containing both mutations in combination. The T202C mutation alone decreased the enzyme activity to less than 1% of the activity of the wild type FUT3 allele. These results demonstrate, that the Trp68 --> Arg substitution in human Fuc-TIII is the capital amino acid change responsible for the appearance of the Le(a-b-) phenotype on human erythrocytes in individuals homozygous for both the T202C and C314T mutations. 相似文献
110.
Marco Favaro Silvia Leonardi Carlos Valero‐Vidal Silvia Nappini Marianne Hanzlik Stefano Agnoli Julia Kunze‐Liebhuser Gaetano Granozzi 《Advanced Materials Interfaces》2015,2(5)
Anodic production of self‐organized titania nanotubes (TNTs) in an electrolyte enriched with graphene oxide quantum dots (GOQDs) is reported. The TNT‐GOQD composites grown under these conditions show in‐situ carbon doping, leading to the formation of anatase TiO2 domains and to the reduction to substoichiometric oxide (TiOx) and TiC. Surface science and electrochemical techniques are used in synergy to reveal that graphitic carbon is incorporated into TiO2 upon anodic nanotube growth promoting the formation of oxygen vacancies and thus TiO2 reduction. Upon annealing in ultrahigh vacuum, titanium oxycarbide (TiOxCy) is formed at temperatures ≥400 °C, where the material changes from a semiconductor to a semimetal. At the solid/liquid interface, the apparent electron donor density increases from as‐grown TNTs to as‐grown TNT‐GOQD composites due to the carbon doping, and the conductivity increases further with annealing temperature due to the increasing concentration of coordinatively unsaturated C atoms, crystallinity, and TiO2 reduction. The materials synthesized and characterized in this study find application in different areas ranging from visible light photocatalysis and photo‐electrochemistry to use as Li‐ion battery anodes and electrocatalyst supports, because it is possible to gradually tune the density of states below the Fermi level, which can be referred to as band‐gap engineering. 相似文献