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排序方式: 共有763条查询结果,搜索用时 78 毫秒
91.
A new conductimetric microprobe and conductimeter have been designed to study mixing phenomena in fluids of non-uniform composition in turbulent flow. For the case of a parallelepipedic cell with two parallel jets at different salt tracer concentrations, the spatial distribution and the mean and variance of the fluctuation of the tracer are obtained experimentally and used to characterise the state of local mixing.A theoretical expression for the mean concentration is obtained by solving the convective diffusion equation. Comparison of experimental and theoretical results is satisfactory and proves to be a sufficiently good test of the reliability of the apparatus used. 相似文献
92.
Reaktionen während des Anlaufs. Brennfleckentkohlung während des linearen Abfalls. Schematische Temperaturprofile durch den Reaktionsraum. Modellvorstellungen zu den Vorgängen im Blasstrahl. Badentkohlung während des Auslaufs. 相似文献
93.
B Carcy E Precigout A Valentin A Gorenflot J Schrevel 《Canadian Metallurgical Quarterly》1995,63(3):811-817
The supernatants of in vitro cultures of Babesia divergens Rouen 1987 in human erythrocytes, obtained by using a semidefined medium based on human high-density lipoproteins, were fractionated by gel filtration chromatography into four fractions, F1 to F4. The crude supernatant as well as each fraction adjuvanted with Quil-A protected gerbils from mortality due to a homologous infectious challenge. Analysis of the humoral response of the 10 protected gerbils with fraction F4, containing major proteins with molecular masses lower than 50 kDa, showed that a few antigens (from 50 to 17 kDa) could be important candidates for an improved vaccine against B. divergens babesiosis. As an immunodominant response was directed against the 37-kDa antigen (Bd37) in two different B. divergens strains tested, a polyclonal antibody directed against Bd37 was produced in a rabbit. In an immunofluorescence assay, the anti-Bd37 antiserum strongly labelled small internal vesicles of the merozoites and the cell surface was diffusely labelled after fixation, whereas on live merozoites, this labelling was not observed. [3H]glucosamine-radiolabelling experiments demonstrate that Bd37 is a glycoprotein. The Bd37 protein can also be labelled with [14C]palmitate but not with [3H]myristic acid. In Triton X-114 temperature phase partitioning of B. divergens-infected erythrocyte extracts, Bd37 was exclusively found into the detergent phase, indicating that the palmitoylated Bd37 protein was in the membrane fraction. In the in vitro supernatant, the glycoprotein Bd37 was found in a nonpalmitoylated form, indicating excretion and/or release of the glycoprotein from the merozoite. 相似文献
94.
Hans Berns Sergej Nikolaijevitsch Bugajchuk Vladimir Andrejevitsch Duz Rüdiger Ehrhardt Valentin Gennadijevitsch Gavriljuk Yuri Nikolaljevitsch Petrov Igor Arkabijevitsch Yakubzov 《国际钢铁研究》1994,65(10):444-450
Hardness measurements, dilatometry, internal friction measurements, Mössbauer spectroscopy and transmission electron microscopy are utilized in order to study the effect of tempering on the microstructure of a stainless martensitic steel containing 15% Cr, 1% Mo and 0.6% N. A similar carbon steel containing 15% Cr, 1% Mo and 0.6% C is used for comparison. Tempering of alloy Fe-15Cr-1Mo-0.6N in the low temperature range of 353-473 K leads to formation of hexagonal ?-nitride (Fe,Cr)2N, which is followed by precipitation of the orthorombic ?-nitride (Fe,Cr)2N at temperatures of 573-773 K. The hexagonal nitride Cr2N is precipitated at 923 K and preferably formed at grain boundaries. The alloy Fe-15Cr-1Mo-0.6C shows the expected tempering behaviour. ?-carbide (Fe,Cr)2C and cementite (Fe,Cr)3C are precipitated during low temperature ageing, followed by the formation of Cr7C3 carbides after the temperature has risen to 873 K. With a similar interstitial content the amount of retained austenite in the nitrogen martensite is nearly twice as high as in the carbon one. Furthermore, the thermal stability of the retained austenite of the nitrogen alloy is substantially higher than that of the carbon steel. 相似文献
95.
Suman Pokhrel Cristian E. Simion Valentin S. Teodorescu Nicolae Barsan Udo Weimar 《Advanced functional materials》2009,19(11):1767-1774
Widely applicable nonaqueous solution routes have been employed for the syntheses of crystalline nanostructured tungsten oxide particles from a tungsten hexachloride precursor. Here, a systematic study on the crystallization and assembly behavior of tungsten oxide products made by using the bioligand deferoxamine mesylate (DFOM) (product I ), the two chelating ligands hexadecyltrimethylammoniumbromide (CTAB) ( II ) and poly(alkylene oxide) block copolymer (Pluronic P123) ( III ) is presented. The mechanistic pathways for the material synthesis are also discussed in detail. The tungsten oxide nanomaterials and reaction solutions are characterized by Fourier transform IR, 1H, and 13C NMR spectroscopies, powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high‐resolution TEM, and selected‐area electron diffraction. The indexing of the line pattern suggests WO3 is in its monoclinic structure with a = 0.7297 nm, b = 0.7539 nm, c = 0.7688 nm, and β‐i; = 90.91 °. The nanoparticles formed have various architectures, such as chromosomal shapes (product I ) and slates ( II ), which are quite different from the mesoporous one ( III ) that has internal pores or mesopores ranging from 5 to 15 nm. The nanoparticles obtained from all the synthetic procedures are in the range of 40–60 nm. The investigation of the gas‐sensing properties of these materials indicate that all the sensors have good baseline stability and the sensors fabricated from material III present very different response kinetics and different CO detection properties. The possibility of adjusting the morphology and by that tuning the gas‐sensing properties makes the preparation strategies used interesting candidates for fabricating gas‐sensing materials. 相似文献
96.
Valentina Matveeva Alexey Bykov Valentin Doluda Mikhail Sulman Narendra Kumar Stanislaw Dzwigaj Eric Marceau Leonid Kustov Olga Tkachenko Esther Sulman 《Topics in Catalysis》2009,52(4):387-393
In the present work, nanocatalysts prepared on inorganic supports (zeolites) were investigated in d-glucose oxidation and compared to systems supported on polymer (hypercrosslinked polystyrene (HPS)) previously described.
Catalytic activities and selectivities were measured under various reaction conditions. The selectivity of d-glucose oxidation and activity of both Pd-containing zeolites and HPS-Ru were similar (99.7% and TOF 0.013–0.014 mol/(mol Me s)).
Physicochemical analysis X-ray photoelectron spectroscopy, liquid nitrogen physisorption, diffuse reflectance infrared Fourier
transform spectroscopy of adsorbed CO for metal sites evaluation, CD3CN for acid sites evaluation showed that Pd species were in oxidic form, while Ru species were in oxidic and reduced form.
The catalytic activity decreased when acidic sites were present in Pd-containing zeolites. 相似文献
97.
Sergey Y. Nechaev Alexei V. Lutay Valentin V. Vlassov Marina A. Zenkova 《International journal of molecular sciences》2009,10(4):1788-1807
RNA non-enzymatic recombination reactions are of great interest within the hypothesis of the “RNA world”, which argues that at some stage of prebiotic life development proteins were not yet engaged in biochemical reactions and RNA carried out both the information storage task and the full range of catalytic roles necessary in primitive self-replicating systems. Here we report on the study of recombination reaction occuring between two 96 nucleotides (nts) fragments of RNAs under physiological conditions and governed by a short oligodeoxyribonucleotide template, partially complementary to sequences within each of the RNAs. Analysis of recombination products shows that ligation is predominantly template-directed, and occurs within the complementary complex with the template in “butt-to-butt” manner, in 1- or 3- nts bulges or in 2–3 nts internal loops. Minor recombination products formed in the template-independent manner are detected as well. 相似文献
98.
Lázaro Valentin Zuquette Janaina Barrios Palma Osni José Pejon 《Bulletin of Engineering Geology and the Environment》2009,68(1):117-136
The goal of the study was to establish a methodology for territorial zoning based on predicted groundwater pollution. The
31 attributes identified were divided into six different environmental components associated with the transport of contaminants
to the geological medium. Two indices were obtained: the pre-disposition index (PI), and the potential pollution intensity
index (PPII). The paper reports an assessment of the potential pollution of the groundwater in the sandstones of the Botucatu
and Pirambóia Formations, Sao Paulo, Brazil. The region was divided into 447 units according to the type of land use, size
of watershed and degree of lithological homogeneity. The units were assessed for potential pollution in the pre-disposition
condition (based on geological/geotechnical data) and the complete condition (geological/geotechnical and situation specific
data) using the analytical hierarchical process method. A high degree of pollution potential was established for 35 of the
units in the complete condition and 157 units in the pre-disposition condition. The study has highlighted areas where attention
to pollution control should be focused.
相似文献
99.
100.