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221.
This study quantified Escherichia coli (EC) and enterococci (ENT) in beach waters and dominant source materials, correlated these with ambient conditions, and determined selected EC genotypes and ENT phenotypes. Bathing-water ENT criteria were exceeded more frequently than EC criteria, providing conflicting interpretations of water quality. Dominant sources of EC and ENT were bird feces (10(8)/d/bird), storm drains (10(7)/d), and river water (10(11)/d); beach sands, shallow groundwater and detritus were additional sources. Beach-water EC genotypes and ENT phenotypes formed clusters with those from all source types, reflecting diffuse inputs. Some ENT isolates had phenotypes similar to those of human pathogens and/or exhibited high-level resistance to human-use antibiotics. EC and ENT concentrations were influenced by collection time and wind direction. There was a 48-72-h lag between rainfall and elevated EC concentrations at three southern shoreline beaches, but no such lag at western and eastern shoreline beaches, reflecting the influence of beach orientation with respect to cyclic (3-5 d) summer weather patterns. In addition to local contamination sources and processes, conceptual or predictive models of Great Lakes beach water quality should consider regional weather patterns, lake hydrodynamics, and the influence of monitoring method variables (time of day, frequency). 相似文献
222.
Warriner K Ibrahim F Dickinson M Wright C Waites WM 《Journal of food protection》2003,66(10):1790-1797
In this study, the interaction of a bioluminescence-labeled Escherichia coli strain with growing spinach plants was assessed. Through bioluminescence profiles, the direct visualization of E. coli growing around the roots of developing seedlings was accomplished. Subsequent in situ glucuronidase (GUS) staining of seedlings confirmed that E. coli had become internalized within root tissue and, to a limited extent, within hypocotyls. When inoculated seeds were sown in soil microcosms and cultivated for 42 days, E. coli was recovered from the external surfaces of spinach roots and leaves as well as from surface-sterilized roots. When 20-day-old spinach seedlings (from uninoculated seeds) were transferred to soil inoculated with E. coli, the bacterium became established on the plant surface, but internalization into the inner root tissue was restricted. However, for seedlings transferred to a hydroponic system containing 10(2) or 10(3) CFU of E. coli per ml of the circulating nutrient solution, the bacterium was recovered from surface-sterilized roots, indicating that it had been internalized. Differences between E. coli interactions in the soil and those in the hydroponic system may be attributed to greater accessibility of the roots in the latter model. Alternatively, the presence of a competitive microflora in soil may have restricted root colonization by E. coli. The implications of this study's findings with regard to the microbiological safety of minimally processed vegetables are discussed. 相似文献
223.
Factors affecting the correlation coefficient template matching algorithm with application to real-time 2-D coronary artery MR imaging 总被引:2,自引:0,他引:2
This paper characterizes factors affecting the accuracy of the correlation coefficient (CC) template matching algorithm, as applied to motion tracking from two-dimensional real-time coronary artery magnetic resonance images. The performance of this algorithm is analyzed in the presence of both random and systematic error. In the presence of random error, it is shown that a necessary and sufficient condition for accurate motion tracking is a large CC difference-to-noise ratio (CCDNR). The CCDNR itself is in turn affected by five factors: image and template size, image and template structure, and the magnitude of the noise. Techniques are introduced for manipulating some of these factors in order to increase the CCDNR for greater motion tracking accuracy. In the presence of superimposed systematic error it is shown that, while large CCDNR is necessary, it alone is not sufficient to ensure accurate motion tracking. Techniques are developed for improving motion tracking accuracy that minimize the effects of systematic error, while maintaining an adequate CCDNR level. The ability of these techniques to improve motion tracking accuracy is demonstrated both in phantoms and in coronary artery images. 相似文献
224.
Next-Generation NASA Airborne Oceanographic Lidar System 总被引:2,自引:0,他引:2
The complete design and flight test of the next-generation Airborne Oceanographic Lidar (AOL-3) is detailed. The application of new technology has allowed major reductions in weight, volume, and power requirements compared with the earlier AOL sensor. Subsystem designs for the new AOL sensor include new technology in fiber optics, spectrometer detector optical train, miniature photomultiplier modules, dual-laser wavelength excitation from a single small laser source, and new receiver optical configuration. The new design reduced telescope size and maintained the same principal fluorescence and water Raman bands but essentially retained a comparable measurement accuracy. A major advancement is the implementation of single-laser simultaneous excitation of two physically separate oceanic target areas: one stimulated by 532 nm and the other by 355 nm. Backscattered fluorescence and Raman signals from both targets are acquired simultaneously by use of the same telescope and spectrometer-detector system. Two digital oscilloscopes provide temporal- and depth-resolved data from each of seven spectral emission bands. 相似文献
225.
H. Wright J.-M. Le Cléac'h M. Deveughèle 《Bulletin of Engineering Geology and the Environment》2001,60(1):59-67
The objective of this work was to undertake creep tests on shale and describe the microtextural phenomena which initiate internal damage/rupture under thermomechanical loading and relative humidity conditions. The CGI test cell is a system developed at the Centre de Geologie de l'Ingénieur specifically to allow observation of the fabric of a thick slide (50×40×5?mm) at different magnifications during the test. The CGI test cell imposes both an axial and a planar strain on the sample. The first step is to prepare a thick slide from a core and to describe its "initial" state. The second stage is to undertake a creep test to rupture, while the third step is to study the fragments of the ruptured material using XRD (X-ray diffractometry), SEM (scanning electron microscopy) and EDS (energy dispersive spectrometry). The samples studied are from the shales of the Callovo-Oxfordian of the Paris Basin, to the south of Bar-le-Duc in the east of France. These rocks consist of clay minerals (illite and kaolinite), quartz, calcite (22.8%), dolomite, feldspar and pyrite (1%). The pyrite is essentially found in the bioclasts. The creep test is carried out under thermomechanical loading with an axial stress of up to 12?MPa and a temperature rising to 80??°C. The relative humidity is maintained at more than 90%. After 33?days the axial strain reached 0.76%, with rupture of the thick slide occurring 10?days later. The deformation was related to the texture/heterogeneity of the rock and occurred mainly along fissuring. Rupture also occurred along bedding planes, particularly where oxidized pyritic bioclasts were present. The chemical phenomena noted were in part related to the formation of iron hydroxides and sulphuric acid. This reacts with the calcite to form gypsum, which has a lower density than the original pyrite and calcite. The XRD indicated that the iron hydroxides observed on the discontinuities are dominantly limmonite. Examination of the SEM and EDS suggested an increase in porosity, even at some distance from the macroscopic fissures. 相似文献
226.
Frequencies of births that were reported for specific days of the month were documented for US dairy cattle born since 1987 by birth year, herd size, and registry status and compared with calving frequencies for those dates. Because birth dates are expected to be random and uniformly distributed throughout each month, percentages of births on individual dates were expected to be equal (3.3% for d 1 to d 28, 3.2% for d 29, 3.0% for d 30, and 1.9% for d 31). However, percentages of reported birth dates for d 1, 2, 10, 15, and 20 were higher than expected. The percentage of reported births for d 1 was highest (5.3%) of all days of the month regardless of herd size or registry status. The nonuniform distribution of birth dates within month indicated that a substantial number of birth dates were unknown and that estimated birth dates had been reported. About one-third of the birth dates recorded on d 1 appeared to have been estimated, or altered to gain an advantage in cattle shows. The highest frequencies for birth dates on d 1 (5.9 to 7.4%) were found for registered cows during months that initiated age groupings for dairy shows (March, June, September, and December). Birth dates for some registered cows were intentionally misreported as confirmed by comparison of birth dates of individual cows with calving dates of their dams. Reported calving dates appeared to be more accurate than reported births; the inflated frequency of recorded calvings on d 1 was only about 30% as large as the inflated frequency of recorded births. Because cow age is determined by birth date, proper reporting of birth dates is important to ensure the accuracy of standardized yield and fitness records and the genetic evaluations that are based on those records. When animals' recorded birth dates and their dams' calving dates differ, more credence should be given to the latter to improve accuracy. 相似文献
227.
Cesena C Morelli L Alander M Siljander T Tuomola E Salminen S Mattila-Sandholm T Vilpponen-Salmela T von Wright A 《Journal of dairy science》2001,84(5):1001-1010
A wild-type Lactobacillus crispatus, showing a cell aggregation phenotype and its spontaneous nonaggregating mutant were compared for their in vitro adhesion properties to human ileal mucus and to a cultured human colonic cell line (Caco2) and for their in vivo colonization and adhesion potential with colonoscopy patients as volunteers in feeding trials. The wild-type strain adhered better to mucus or to Caco2 cells than did the mutant. Altogether, three human trials with the wild type and two with the mutant strain were performed. In two of the trials, the wild type could be recovered from either fecal samples or biopsies taken from the colon, while the mutant strain could not be demonstrated in either of the trials where it was used. The L. crispatus colonies recovered from the trials were often mixed, and several enterococci and lactobacillus strains coaggregating with L. crispatus wild type could be isolated. The results indicate that the surface-mediated properties, such as aggregation, of lactobacilli can have a role in adhesion and colonization. 相似文献
228.
Hills BP Buff C Wright KM Sutcliffe LH Ridge Y 《International journal of food microbiology》2001,68(3):187-197
Evolving microstructure in a model dextran solution is shown to exert a major influence on the survival of Escherichia coli K-12 frag 1 and Salmonella typhimurium LT2. The microstructure results from microscopic phase separation, which develops over several hours resulting in hardening of the solution into a glassy state. The microstructure is characterized by an array of physical methods including image analysis, electron spin resonance and bulk rheology, and it is shown that bacterial survival depends on the formation of microscopic. water-rich domains and not primarily on bulk water activity or hardness. 相似文献
229.
230.