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91.
Takehiko Matsuzaki Taka -aki Hanaoka Kazuhiko Takeuchi Yoshihiro Sugi Matti Reinikainen 《Catalysis Letters》1991,10(3-4):193-199
In the hydrogenation of carbon monoxide, alkali cations were found to be effective as modifiers for highly dispersed cobalt catalyst to improve the selectivities of C2-oxygenated compounds, especially acetic acid and acetaldehyde, and to increase the olefin/paraffin ratio of hydrocarbons. These effects are ascribed to depression of the hydrogenating ability of the catalyst by modification with alkali cations. 相似文献
92.
Laitinen J Julkunen-Tiitto R Rousi M Heinonen J Tahvanainen J 《Journal of chemical ecology》2005,31(10):2243-2262
This study investigates variation in the secondary chemistry of the bark of three closely related, winter-dormant species
of white birch (Betula resinifera, B. pendula, and B. platyphylla) at different ontogenetic stages by using different plant parts (top and base). The experimental birches were grown for 4 years
in two growing conditions (pot and field) at different nutrient levels. There was considerable species-specific quantitative
and qualitative variation in the secondary chemicals in bark, but this was also affected by fertilization and the age of the
plant. In general, there was greater chemical diversity in saplings than in seedlings. The study revealed three new components,
secoisolariciresinol 9-O-β-glucopyranoside and two of its derivatives, that have not been reported previously for the bark of white birches. Principal
component analysis showed that the species studied had a similar chemical composition at the juvenile stage, but as the plants
grew, they became more clearly differentiated, which indicates that the species of older plants can be identified by chemotaxonomy.
Evidently, the secondary chemistry of birches is under genetic control, but it is affected by properties of growing conditions
and ontogeny.
Electronic Supplementary Material Supplementary material to this paper is available in electronic form at 相似文献
93.
Miina Rautiainen Matti Mõttus Anu Akujärvi Titta Majasalmi 《Remote sensing of environment》2011,115(12):3020-3028
The influence of the seasonal cycle of boreal forest understory has been noticed in global remote sensing of vegetation, especially in remote sensing of biophysical properties (e.g. leaf area index) of the tree-layer in a forest. A general problem in the validation of operationally produced global biophysical vegetation products is the lack of ground reference data on the seasonal variability of different land surface types. Currently, little is known about the spectral properties of the understory layers of boreal forests, and even less is known about the seasonal dynamics of the spectra. In this paper, we report seasonal trajectories of understory reflectance spectra measured in a European boreal forest. Four study sites representing different forest fertility site types were selected from central Finland. The understory composition was recorded and its spectra measured with an ASD FieldSpec Hand-Held UV/VNIR Spectroradiometer ten times during the growing period (from May to September) in 2010. Our results show that the spectral differences between and within understory types are the largest at the peak of the growing season in early July whereas in the beginning and end of the growing season (i.e. early May and late September, respectively) the differences between the understory types are marginal. In general, the fertile sites had the brightest NIR spectra throughout the growing season whereas infertile types appeared darker in NIR. Our results also indicated that a mismatch in the seasonal development of understory and tree layers does not occur in boreal forests: the understory and tree layer vegetation develop at a similar pace in the spring (i.e. there are no or only few spring ephemerals present), and the forests with the strongest seasonal dynamics in tree canopy structure (LAI) have also the strongest dynamics in understory spectra. 相似文献
94.
Airborne discrete-return LIDAR data in the estimation of vertical canopy cover, angular canopy closure and leaf area index 总被引:2,自引:0,他引:2
Remote sensing of forest canopy cover has been widely studied recently, but little attention has been paid to the quality of field validation data. Ecological literature has two different coverage metrics. Vertical canopy cover (VCC) is the vertical projection of tree crowns ignoring within-crown gaps. Angular canopy closure (ACC) is the proportion of covered sky at some angular range around the zenith, and can be measured with a field-of-view instrument, such as a camera. We compared field-measured VCC and ACC at 15° and 75° from the zenith to different LiDAR (Light Detection and Ranging) metrics, using several LiDAR data sets and comprehensive field data. The VCC was estimated to a high precision using a simple proportion of canopy points in first-return data. Confining to a maximum 15° scan zenith angle, the absolute root mean squared error (RMSE) was 3.7-7.0%, with an overestimation of 3.1-4.6%. We showed that grid-based methods are capable of reducing the inherent overestimation of VCC. The low scan angles and low power settings that are typically applied in topographic LiDARs are not suitable for ACC estimation as they measure in wrong geometry and cannot easily detect small within-crown gaps. However, ACC at 0-15° zenith angles could be estimated from LiDAR data with sufficient precision, using also the last returns (RMSE 8.1-11.3%, bias -6.1-+4.6%). The dependency of LiDAR metrics and ACC at 0-75° zenith angles was nonlinear and was modeled from laser pulse proportions with nonlinear regression with a best-case standard error of 4.1%. We also estimated leaf area index from the LiDAR metrics with linear regression with a standard error of 0.38. The results show that correlations between airborne laser metrics and different canopy field characteristics are very high if the field measurements are done with equivalent accuracy. 相似文献
95.
On the direct estimation of creep and relaxation functions 总被引:1,自引:0,他引:1
Two alternative approaches for estimating linear viscoelastic material functions from a single experiment under random excitation
are derived and analyzed. First, Boltzmann’s superposition integral is discretized into a system of linear equations. Due
to the ill-posedness of the resulting matrix equation, Tikhonov’s regularization is introduced. Second, the integral is transformed
into a recursive formula, using a Prony series representation of viscoelastic material functions, in which gradient-based
optimization is applied. Numerical results are provided to compare and verify the applicability of the presented numerical
procedures. 相似文献
96.
97.
Tomi Roinila Tomi Helin Matti Vilkko Teuvo Suntio Hannu Koivisto 《Simulation Modelling Practice and Theory》2009,17(6):1043-1058
Switching power converters are extensively used in powering various electronics loads and processes. The proper functioning of those processes may be vital for the every day life of the society. Therefore, the reliable operation of the switched-mode converters is of prime importance and the functioning has to be verified reliably both during the design phase and in the production. It has been shown lately that the main deficiencies in the verification process are related to the dynamics of the converter which can be characterized with a certain set of transfer functions. This paper investigates the frequency response measurement methods by means of which the transfer functions can be identified fast and accurately being economically feasible to apply also in the production phase. Multi-period maximum length pseudo random binary sequence (m.l.b.s.) is used as the excitation signal and the transfer functions are identified from the measurement data with circular cross-correlation method. The measurement uncertainty is computed by means of fuzzy density approach yielding a certain confidence band around the measured nominal response. The proposed methods are verified both by simulations and experimental data from high-frequency switched-mode converters. 相似文献
98.
Atomic layer deposition (ALD) was used to produce hydroxyapatite from Ca(thd)2 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionato) and (CH3O)3PO onto Si(100) and Corning (0211). Film crystallinity, stoichiometry, possible impurities and surface morphology were determined. The as-deposited films contained significant amounts of carbonate impurities however, annealing at moist N2 flow reduced the carbonate content even at 400 °C. The as-deposited Ca-P-O films were amorphous but rapid thermal annealing promoted the formation of the hydroxyapatite phase. Mouse MC 3T3-E1 cells were used for the cell culture experiments. According to the bioactivity studies cell proliferation was enhanced on as-deposited ALD-grown Ca-P-O films and greatly enhanced on films annealed at 500 °C in comparison with reference cells on borosilicate glass or cell culture polystyrene. 相似文献
99.
Frederick K. Teye Mikko Hautala Matti Pastell Jaan Praks Imbi Veermäe Väino Poikalainen Aime Pajumägi Tapani Kivinen Jukka Ahokas 《Energy and Buildings》2008,40(7):1194-1201
A series of ventilation, thermal and indoor air quality measurements were performed in 14 different dairy buildings in Estonia and Finland. The number of animals in the buildings varied from 30 to 600. Measurements were made all year round with ambient temperatures ranging between −40 °C and +30 °C. The results showed that microclimatic conditions in the dairy buildings were affected by the design of the building, outside temperature, wind, ventilation and manure handling method. The average inside air concentration of carbon dioxide was 950 ppm, ammonia 5 ppm, methane 48 ppm, relative humidity 70% and inside air velocity was 0.2 m/s. Although occasionally exceeded, the ventilation and average indoor air quality in the dairy buildings were mainly within the recommended limits. 相似文献
100.
Facial expression recognition from near-infrared videos 总被引:1,自引:0,他引:1