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81.
82.
Roberto Hirata Junior Marcel Brun Junior Barrera Edward R. Dougherty 《Journal of Mathematical Imaging and Vision》2002,16(3):199-222
The design of an aperture operator is based on adequately constraining the spatial domain and the graylevel range in order to diminish the space of operators and, consequently, the estimation error. The design of a resolution constrained operator is based on adequately combining information from two or more different resolutions and has the same motivation, that is, diminish the space of operators to facilitate design. This paper joins these approaches and studies multiresolution design of aperture operators for grayscale images. Spatial resolution constraint, range resolution constraint and the combination of both constraints are characterized, and the error increase by using the constrained filter in place of the optimal unconstrained one is analyzed. Pyramidal multiresolution design involves applying the resolution constraint approach hierarchically, from the higher to the lower resolution space. These approaches are also characterized and their error increase analyzed. The system that has been implemented to design pyramidal multiresolution operators is described and has its complexity (memory and runtime) analyzed. Several simulations and two applications for deblurring are shown and compared to optimal linear filters. The results confirm the usefulness of the approach. 相似文献
83.
Although particle detachment is a common phenomenon associated with most tribological processes, it seldom occurs that each piece of elemental debris can be considered as the result of a single event. Such an association has been revealed by the systematic study of a specific system, where a pin of graphite is made to rub against thoroughly polished steel. While the discontinuous nature of the transfer film allows a quantitative assessment of the volume of transfer h
e to be made by 3D optical-profilometry, the linear dependence of the rate of particle detachment dh
e/dn (n=number of rubbing cycles) with the logarithm of sliding speed v strongly suggests the existence of a particular type of stick–slip, where each stick may lead to the detachment of a debris particle. The variations in size of these debris with environment as revealed by AFM, further suggest that the global rate of particle detachment is of the form: dh
e/dn=Nx
i
, where N is the number of stick–slip events per rubbing cycle, x the proportion of stick events leading to a cohesive rupture, and
i
the mean volume of an elemental particle. While this relation is apparently supported by most experimental results, its actual validation can only be made by experiments at the level of single (nanoscale) asperities, carried out under well-controlled experimental conditions. 相似文献
84.
Summary The evolution of scientific fields analyzed by co-word analysis and presented in strategic diagrams is simulated based on
the law of cumulative advantages - the probability of a new tie between two keywords depends positively on the frequencies
in which both keywords have taken part already. The results we get from simulations are compared with the results of real
scientific field evolution. We consider the high correspondence of both to be a proof of the working of the law of cumulative
advantages in the development of scientific fields and we believe that our research opens new possibilities for predictions
of the development of scientific fields. 相似文献
85.
Roland Guérin El Houssine El Ghadraoui Jean-Yves Pivan Jean Padiou Marcel Sergent 《Materials Research Bulletin》1984,19(10):1257-1270
Two new compounds Ni12Zr2P7 and Ni20Zr6P13 were synthesized in the NiZrP system by reacting the constituent elements. Ni12Zr2P7 is of the Fe12Zr2P7-type while Ni20Zr6P13 appears as a new structural type in the chemistry of transition metal phosphides. Its unit cell is hexagonal with space group P6̄ and contains one formula unit. The X-ray structure was studied from three-dimensional single-crystal counter data and was refined down to R = 0.040 for 221 independent reflections. The structure of Ni20Zr6P13 can be described as built up by two groups of three phosphorus trigonal prisms occupied by the zirconium atoms. In each group, the |ZrP6| prisms are linked together by common edges in order to generate triangular phosphorus sites occupied by nickel atoms. In addition, nickel atoms are also in tetrahedral and square-planar pyramidal phosphorus sites. A comparative study with the Fe2P- and Co4Hf2P3-type structures having the same metal/non metal ratio as in Ni12Zr2P7 and Ni20Zr6P13 is also discussed. A nearly temperature independent paramagetism and a metallic conduction deducted from magnetic and electrical measurements exhibit the metallic behavior for these new compounds. 相似文献
86.
New halide glasses based on cadmium halides as glass progenitors have been discovered. This paper describes fluoride glasses in the CdF2-BaF2-ZnF2 ternary system. Binary glasses CdxBa1?xF2 (0.45 < x < 0.52) have been obtained. The limits of the glassy area are: 5–55 % CdF2, 15–55 % BaF2, 0–60 % ZnF2. Numerous fluorides such as the alkali fluorides, AlF3, YbF3 and ThF4 may be included in the glass composition. Only thin glass samples may be prepared because of the high crystallization rate. The characteristic temperatures of the Cd0.3Ba0.4Zn0.3F2 glass are 290° C for TG, 330° C for TC and 620° C for TF. The optical transmission spectrum of a thin sample shows an extrinsic absorption band at around 9000 nm and the multiphonon IR absorption edge beyond 10500 nm. The optimization of these glasses will make them attractive materials for IR transmittance and IR optical fibres. The crystallization of the Cd0.5Ba0.5F2 glass results in two solid solutions Ba1?xCdxF2 and Cd1?xBaxF2 deriving from the fluorite structural type. Thus, cadmium fluoride glasses appear as the result of the disordering of the fluorite type structure in the same way as ZrF4-based glasses derive from the disordering of the ReO3-type structure. Both glasses may be described as the random insertion of cations into an aperiodic array of F? anions. 相似文献
87.
Hiscock Merrill; Kinsbourne Marcel; Caplan Bruce; Swanson James M. 《Canadian Metallurgical Quarterly》1979,88(1):27
Administered dichotic digit tasks requiring free report and selective listening, respectively, to 20 6–16 yr old hyperactive children. Ss received methylphenidate before 2 experimental sessions and a placebo before 2 control sessions. The stimulant did not improve free-report performance significantly; rather it facilitated or impaired performance, depending on how it affected the order in which stimuli were reported. Similarly, medication had no effect on overall selective-listening performance, but it increased the difficulty of switching attention from one ear to the other. Results demonstrate that stimulants may act to maintain selective attention and to inhibit channel switching. Listening asymmetry, that is, right-ear superiority, was influenced by task variables but not by stimulant medication. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
Regelous M Turner SP Elliott TR Rostami K Hawkesworth CJ 《Analytical chemistry》2004,76(13):3584-3589
We describe a new method for the chemical separation and analysis of Pa in silicate rock samples by isotope dilution. Our new technique has the following advantages over previous methods: (a) The initial separation of Pa from the rock matrix is carried out using anionic exchange resin and HCl-HF mixtures, avoiding the need to remove F(-) quantitatively from the sample solution prior to this step, (b) Efficient ionization of Pa is achieved using a multicollector inductively coupled plasma mass spectrometer, so that smaller sample sizes and shorter measurement times are required, compared to previous methods using thermal ionization mass spectrometry or alpha spectrometry. (c) Plasma ionization requires less efficient separation of the high field strength elements from Pa, thus reducing reagent volumes, blanks, and sample preparation times. Instrumental mass fractionation can be corrected for using admixed U of known isotopic composition. Using this method, Pa concentrations can be measured to a precision of approximately 0.5% and an accuracy of approximately 1% using only a few tens of femtograms of Pa. 相似文献
89.
The molecular architecture of the GPCRs, including the dynamic set of interactions between the receptor and the ligand, is one of the key structural questions of biophysical approaches. In the present study, molecular dynamics (MD) simulations were performed on the well-validated molecular model of the vasopressin V1a receptor applying different parameters (i.e., force fields, time variation, use of constraints) in order to sample the conformational space of the endogenous ligand arginine vasopressin (AVP), to explore different putative binding modes, and to analyze the simulation results with respect to experimental data. Noteworthy, it is to mention that for the first time a model of the vasopressin receptor remained stable in a 500 ps MD simulation run under vacuo boundary conditions using the Kollman all-atom FF even though no constraints were imposed. Conclusively, we determined an optimized experimental procedure for studying the dynamics and structure-functionship of this highly important family of GPCRs: the use of MD simulations with the Kollman all-atom force-field parameters on a constrained receptor. Our simplified model may be used as a basis for structure based design of new GPCR ligands and for in silico screening of virtual combinatorial chemistry libraries. 相似文献
90.
Rohrlack T Christoffersen K Hansen PE Zhang W Czarnecki O Henning M Fastner J Erhard M Neilan BA Kaebernick M 《Journal of chemical ecology》2003,29(8):1757-1770
This paper describes the purification and characterization of microviridin J, a newly discovered metabolite of Microcystis that causes a lethal molting disruption in Daphnia spp., upon ingestion of living cyanobacterial cells. Microviridin J consists of an acetylated chain of 13 amino acids arranged in three rings and two side chains. Unlike other known isoforms of microviridin, microviridin J contains arginine that imparts a unique solution conformation characterized by proximal hydrophobic interactions between Arg and other regions of the molecule. This eventually results in the formation and stabilization of an additional ring system. Microviridin J potently inhibits porcine trypsin, bovine chymotrypsin, and daphnid trypsin-like proteases. The activity against trypsin is most likely due to Arg and its distinctive conformational interactions. Overall, the data presented for microviridin J emphasize once again the ability of cyanobacteria to produce numerous and potent environmental toxins. 相似文献