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81.
82.
S Ribeiro A Ramos A Brand?o JR Rebelo A Guerra C Resina A Vila-Lobos F Carvalho F Remédio F Ribeiro 《Canadian Metallurgical Quarterly》1998,13(8):2037-2040
BACKGROUND: Cardiac valve calcification (VC) has been detected with increased frequency in haemodialysis (HD) patients, making it necessary to determine the potential pathogenic factors in uraemic patients. METHODS: A total of 92 chronic HD patients (39 female, 53 male) and 92 age and gender-matched nondialysis control subjects were evaluated by echocardiography and a severity score for VC was determined. Calcium phosphate metabolism was evaluated at the beginning of haemodialysis. RESULTS: We found a greater prevalence of VC in dialysis patients than in normal patients (mitral annulus 44.5% vs 10%, P = 0.02; aortic annulus 52% vs 4.3%, P = 0.01). HD patients with mitral calcification were found to be older than patients without calcification, were on long-term renal replacement therapy, had longer duration of predialysis arterial hypertension, had greater values of the highest value of mean calcium phosphate product in 6 successive months (CaxP) and the highest absolute value of calcium-phosphate product (CaxPmax). We also found a positive correlation between calcification score, age, and CaxP. No correlation was found between actual VC and arterial hypertension or parathyroid hormone. Multiple stepwise regression analysis selected age and CaxP as the most predictive parameters for mitral calcification (r = 0.47). Mitral calcification was associated more frequently with rhythm and cardiac conduction defects, valvular insufficiency and with peripheral vascular calcification. Aortic calcification was correlated with age (r = 0.42) and longer duration of predialysis arterial hypertension. CONCLUSION: Our study confirmed an increased prevalence of VC in HD patients and selected age and calcium phosphate product as the most predictive parameters. These findings support careful monitoring of calcium metabolism beginning at the early stages of end-stage renal failure to reduce the risk of heart disease. 相似文献
83.
Naves LZ Santana FR Castro CG Valdivia AD Da Mota AS Estrela C Correr-Sobrinho L Soares CJ 《Microscopy research and technique》2011,74(12):1088-1092
Morphology, etching patterns, surface modification, and characterization of 2 different fiber posts: Gfp, Glass fiber post; and Cfp, carbon fiber were investigated by SEM analysis, after different surface treatments. Thirty fiber posts, being 15 Gfp and 15 Cfp were divided into a 5 surface treatments (n = 3): C-alcohol 70% (control); HF 4%-immersion in 4% hydrofluoric acid for 1min; H(3) PO(4) 37%-immersion in 37% phosphoric acid for 30s; H(2) O(2) 10%-immersion in 10% hydrogen peroxide for 20 min; H(2) O(2) 24%-immersion in 24% hydrogen peroxide for 10 min. Morphology, etching patterns, surface modification and surface characterization were acessed by SEM analysis. SEM evaluation revealed that the post surface morphology was modified following all treatment when compared with a control group, for both type of reinforced posts. HF seems to penetrate around the fibers of Gfp and promoted surface alterations. The Cfp surface seems to be inert to treatment with HF 4%. Dissolution of epoxy resin and exposure of the superficial fiber was observed in both post groups, regardless the type of reinforcing fiber, H(2) O(2) in both concentrations. Relative smooth surface area was produced by H(3) PO(4) 37% treatment, but with similar features to untreated group. Surface treatment of fiber post is a determinant factor on micromechanical entanglement to resin composite core. Post treatment with hydrogen peroxide resulted strength of carbon and glass/epoxy resin fiber posts to resin composite core. 相似文献
84.
Chaudhury Dipesh; Manella Laura; Arellanos Adolfo; Escanilla Olga; Cleland Thomas A.; Linster Christiane 《Canadian Metallurgical Quarterly》2010,124(4):490
Habituation is a simple form of memory, yet its neurobiological mechanisms are only beginning to be understood in mammals. In the olfactory system, the neural correlates of habituation at a fast experimental timescale involving very short intertrial intervals (tens of seconds) have been shown to depend on synaptic adaptation in olfactory cortex. In contrast, behavioral habituation to odorants on a longer timescale with intertrial intervals of several minutes depends on processes in the olfactory bulb, as demonstrated by pharmacological studies. We here show that behavioral habituation to odorants on this longer timescale has a neuronal activity correlate in the olfactory bulb. Spiking responses of mitral cells in the rat olfactory bulb adapt to, and recover from, repeated odorant stimulation with 5-min intertrial intervals with a time course similar to that of behavioral habituation. Moreover, both the behavioral and neuronal effects of odor habituation require functioning N-methyl-d-aspartic acid receptors in the olfactory bulb. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Ana Beatriz Aguiar Sanford Leidivan Sousa da Cunha Caio Bezerra Machado Flvia Melo Cunha de Pinho Pessoa Abigail Nayara dos Santos Silva Rodrigo Monteiro Ribeiro Fabiano Cordeiro Moreira Manoel Odorico de Moraes Filho Maria Elisabete Amaral de Moraes Lucas Eduardo Botelho de Souza Andr Salim Khayat Caroline Aquino Moreira-Nunes 《International journal of molecular sciences》2022,23(15)
The circadian clock (CC) is a daily system that regulates the oscillations of physiological processes and can respond to the external environment in order to maintain internal homeostasis. For the functioning of the CC, the clock genes (CG) act in different metabolic pathways through the clock-controlled genes (CCG), providing cellular regulation. The CC’s interruption can result in the development of different diseases, such as neurodegenerative and metabolic disorders, as well as cancer. Leukemias correspond to a group of malignancies of the blood and bone marrow that occur when alterations in normal cellular regulatory processes cause the uncontrolled proliferation of hematopoietic stem cells. This review aimed to associate a deregulated CC with the manifestation of leukemia, looking for possible pathways involving CG and their possible role as leukemic biomarkers. 相似文献
86.
Raúl Quijada Juan Luis Guevara Mehrdad Yazdani-Pedram Griselda B. Galland Daniel Ribeiro 《Polymer Bulletin》2002,49(4):273-280
Summary
1-Octadecene (C18) was polymerized by using different metallocene catalysts. The rac-Et(Ind)2ZrC12/MAO (I) and rac-Me2Si(Ind)2ZrC12/MAO (III) presented the highest activity as compared with ra-Et(2-Me-Ind)2ZrCl2/MAO (II) and Ph2C(Flu)(Cp)ZrC12/MAO (IV) catalysts. Catalyst IV produced polymers with highest molecular weights. The microstructure of the polymers was
determined by 13C-NMR spectroscopy. Catalyst systems I, II and III produced isotactic polymers while catalyst IV produced polymers with mainly
syndiotactic structures but with large amount of stereoregular error.
Received: 21 June 2002/Revised version: 4 November 2002/ Accepted: 4 November 2002 相似文献
87.
88.
Michel Keddam Christiane Rakotomavo Hisasi Takenouti 《Journal of Applied Electrochemistry》1984,14(4):437-448
When the impedance is measured on a battery, an inductive impedance is often observed in a high frequency range. This inductance is frequently related to the cell geometry and electrical leads. However, certain authors claimed that this inductance is due to the concentration distribution of reacting species through the pores of battery electrodes. Their argument is based on a paper in which a fundamental error was committed. Hence, the impedance is re-calculated on the basis of the same principle. The model shows that though the diffusion process plays an outstanding role, the overall reaction rate is never completely limited by this process. The faradaic impedance due to the concentration distribution is capacitive. Therefore, the inductive impedance observed on battery systems cannot be, by any means, attributed to the concentration distribution inside the pores. Little frequency distribution is found and the impedance is close to a semi-circle. Therefore depressed impedance diagrams in porous electrodes without forced convection cannot be ascribed to either a Warburg nor a Warburg-de Levie behaviour.Nomenclature
A
D¦C¦ (mole cm s–1)
-
B
j+K¦C¦ (mole cm s–1)
-
b
Tafel coefficient (V–1)
-
C(x)
Concentration ofS in a pore at depthx (mole cm–3)
-
C
0
Concentration ofS in the solution bulk (mole cm–3)
- C C(x)
change under a voltage perturbation (mole cm–3)
- ¦C¦
Amplitude of C (mole cm–3)
-
D
Diffusion coefficient (cm2 s–1)
-
E
Electrode potential (V)
- E
Small perturbation inE namely a sine-wave signal (V)
- ¦E¦
Amplitude of E(V)
-
F
Faraday constant (96500 A s mol–1)
-
F(x)
Space separate variable forC
-
f
Frequency in Hz (s–1)
-
g(x)
KC(x)¦E¦(mole cm s–1)
-
I
Apparent current density (A cm–2)
-
I
st
Steady-state current per unit surface of pore aperture (A cm–2)
- j
Imaginary unit [(–1)1/2]
-
K
Pseudo-homogeneous rate constant (s–1)
-
K
Potential derivative ofK, dK/dE (s–1 V–1)
-
K
*
Heterogeneous reaction rate constant (cm s–1)
-
L
Pore depth (cm)
-
n
Reaction order
- P
Reaction product
-
p
Parameter forF(x), see Equation 13
-
q
Parameter forF(x), see Equation 13
-
R
e
Electrolyte resistance (ohm cm)
-
R
p
Polarization resistance per unit surface of pore aperture (ohm cm2)
-
R
t
Charge transfer resistance per unit surface of pore aperture (ohm cm2)
- S
Reacting species
-
S
a
Total surface of pore apertures (cm2)
-
S
0
Geometrical surface area
-
S
p
Developed surface area of porous electrode per unit volume (cm2 cm–3)
-
s
Concentration gradient (mole cm–3 cm–1)
-
t
Time
-
U
Ohmic drop
-
x
Distance from pore aperture (cm)
-
Z
Faradaic impedance per unit surface of pore aperture (ohm cm2)
-
Z
x
Local impedance per unit pore length (ohm cm3)
-
z
Charge transfer number
-
Porosity
-
Thickness of Nernst diffusion layer
-
Penetration depth of reacting species (cm)
-
Penetration depth of a.c. signal determined by the potential distribution (cm)
-
Electrolyte (solution) resistivity (ohm cm)
-
0
Flow of S at the pore aperture (mole cm2 s–1)
-
Angular freqeuncy of a.c. signal, 2f(s–1)
-
Integration constant 相似文献
89.
Julia Welzenbach Christiane Neuhoff Hanna Heidt Mehmet Ulas Cinar Christian Looft Karl Schellander Ernst Tholen Christine Gro?e-Brinkhaus 《International journal of molecular sciences》2016,17(9)
The aim of this study was to integrate multi omics data to characterize underlying functional pathways and candidate genes for drip loss in pigs. The consideration of different omics levels allows elucidating the black box of phenotype expression. Metabolite and protein profiling was applied in Musculus longissimus dorsi samples of 97 Duroc × Pietrain pigs. In total, 126 and 35 annotated metabolites and proteins were quantified, respectively. In addition, all animals were genotyped with the porcine 60 k Illumina beadchip. An enrichment analysis resulted in 10 pathways, amongst others, sphingolipid metabolism and glycolysis/gluconeogenesis, with significant influence on drip loss. Drip loss and 22 metabolic components were analyzed as intermediate phenotypes within a genome-wide association study (GWAS). We detected significantly associated genetic markers and candidate genes for drip loss and for most of the metabolic components. On chromosome 18, a region with promising candidate genes was identified based on SNPs associated with drip loss, the protein “phosphoglycerate mutase 2” and the metabolite glycine. We hypothesize that association studies based on intermediate phenotypes are able to provide comprehensive insights in the genetic variation of genes directly involved in the metabolism of performance traits. In this way, the analyses contribute to identify reliable candidate genes. 相似文献
90.
Cláudio P. Ribeiro Jr. 《Chemical engineering science》2004,59(12):2363-2377
The study of bubble size distributions in direct-contact evaporators was addressed both theoretically and experimentally. Recently developed models for calculating bubble coalescence and breakage frequencies in isothermal bubble columns were adapted to the population balance equation using the bubble mass as the internal coordinate which was discretized using an expansion of the number density function by impulse functions. A sparger model was developed based on experimental data for a non-coalescing system and using bubble formation models for isothermal and non-isothermal conditions. Bubble size distributions in a direct-contact evaporator operating in the quasi-steady-state regime for four different gas superficial velocities, including the homogeneous and heterogeneous regimes, together with the sparger model, were used for estimating the three empirical parameters from the population balance model, which were observed to be functions of the gas superficial velocity. In all cases considered, the population balance model fitted the experimental data rather well and the regressed parameters exhibit the physically expected behavior with changes in the gas superficial velocity. 相似文献