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991.
This paper describes a simple and accurate procedure for preconcentration of trace amounts of Fe(III), Pb(II) and Cr(III) ions. The preconcentration procedure is based on retention of p-xylenol blue chelates on Amberlite XAD-7. The analytes retained were eluted from Amberlite XAD-7 by using 1 mol L(-1) HCl. The influences of the analytical parameters including amounts of reagents, pH and type of eluent were also investigated. The detection limits of Fe, Pb and Cr were found to be 3.07, 18.6 and 3.27 microg L(-1), respectively. The accuracy of the procedure was checked by the analysis of an electrolytic copper wire sample. The relative error was less than 5%. The presented method was applied to the determination of Fe(III), Pb(II) and Cr(III) in water samples from Denizli, Turkey with good results such as recoveries more than 95%, relative standard deviations below 10%. 相似文献
992.
A pre-concentration method was developed for determination of trace amounts of cadmium, copper and lead in water samples by FAAS after coprecipitation by using potassium 4-methylpiperidinedithiocarbamate (K4-MPDC) as a chelating agent and Bi(III) as a carrier element. This procedure is based on filtration of the solution containing precipitate on a cellulose nitrate membrane filter following Cd(II), Cu(II) and Pb(II) coprecipitation with Bi(III)4-MPDC and then the precipitates together with membrane filter were dissolved in concentrated nitric acid. The metal contents of the final solution were determined by FAAS. Several parameters including pH of sample solution, amount of carrier element and reagent, standing time, sample volume for precipitation and the effects of diverse ions were examined. The accuracy of the method was tested with standard reference material (MBH, C31XB20 and CRM BCR-32) and Cd, Cu and Pb added samples. Determination of Cd, Cu and Pb was carried out in sea water, river water and tap water samples. The recoveries were >95%. The relative standard deviations of determination were less than 10%. 相似文献
993.
Selek H Sahin S Kas HS Hincal AA Ponchel G Ercan MT Sargon M 《Drug development and industrial pharmacy》2007,33(2):147-154
Preparation of starch microspheres using epichlorohydrin is a time consuming method and requires around 18 hr for cross-linking reaction. To reduce reaction time, terbutaline sulfate (TBS) loaded degradable starch microspheres (DSM) were prepared using formaldehyde as the cross-linking agent. All microspheres were spherical in shape and had a porous, rough surface with a mean particle size of 18-24 microm. Whatever the cross-linking time, it was seen that the release of the TBS was not complete during the release experiments. The influence of enzyme on the degradation of microspheres was moderate. Following intravenous administration, initial uptake of microspheres by the lung was higher than those of other organs. 相似文献
994.
O?uzhan Çiçeko?lu 《Microelectronics Journal》1998,29(12):973-975
A simple new circuit realising negative immittances using a single commercially available CFOA is presented. The simulated immittance values can orthogonally be adjusted and all passive sensitivities are no more than unity. For the circuit the phase angle of the realised immittances are independent of the three CFOA non-idealities and the circuit allows easy compensation for these active errors. 相似文献
995.
This paper proposes a compression scheme for face profile images based on three stages, modelling, transformation, and the partially predictive classified vector quantization (CVQ) stage. The modelling stage employs deformable templates in the localisation of salient features of face images and in the normalization of the image content. The second stage uses a dictionary of feature-bases trained for profile face images to diagonalize the image blocks. At this stage, all normalized training and test images are spatially clustered (objectively) into four subregions according to their energy content, and the residuals of the most important clusters are further clustered (subjectively) in the spectral domain, to exploit spectral redundancies. The feature-basis functions are established with the region-based Karhunen–Loeve transform (RKLT) of clustered image blocks. Each image block is matched with a representative of near-best basis functions. A predictive approach is employed for mid-energy clusters, in both stages of search for a basis and for a codeword from the range of its cluster. The proposed scheme employs one stage of a cascaded region-based KLT-SVD and CVQ complex, followed by residual VQ stages for subjectively important regions. The first dictionary of feature-bases is dedicated to the main content of the image and the second is dedicated to the residuals. The proposed scheme is experimented in a set of human face images. 相似文献
996.
Lead zirconate titanate (PZT) thin films were deposited by radio-frequency (r.f.) magnetron sputtering with stoichiometric single oxide target on silicon substrates. The influence of the growth conditions (with or without substrate heating) and the post-annealing treatments (conventional or rapid thermal annealing) on the film properties in terms of structure and microstructure was systematically evaluated. The electrical properties such as the dielectric constant, the loss factor, the leakage current and the ferroelectric properties have been characterized. 相似文献
997.
998.
目的 阐述变长线快速成型机的设计思想与优点. 方法 对变长线快速成型机的机械结构及光学系统的设计进行分析. 结果 变长线快速成型机具有结构合理、成型尺寸大、效率高的优点. 结论 变长线快速成型机具有较好的应用前景 相似文献
999.
1000.
The impacts of water and ethanolic extracts of propolis at a dose of 0.4 or 0.8% on vacuum packaged sardine fillets inoculated with Morganella psychrotolerans DSM 17886 during storage at 3 ± 1°C for 15 days were investigated. All fish groups were inoculated with M. psychrotolerans (108 cfu/ml) at a rate of 1%. Sensory, colorimetric, chemical analysis (total volatile basic nitrogen, thiobarbituric acid, peroxide values, and free fatty acids), pH value, and microbiological analysis (viable mesophilic and psychrophilic bacteria, coliform, and lactic acid bacteria count) were carried out. An enhance in L* values was found in the group treated with 0.8% ethanolic extracts of propolis on the seventh day of the storage. Application of propolis extract on fish fillets significantly inhibited bacterial growth during storage and extended shelf life of sardine for 4 and 6 days by the use of water extract and for 8 days by the use of ethanolic extract at doses of 0.4 and 0.8%, respectively. The result of the study revealed that application of propolis extracts, mainly ethanolic propolis extracts on sardine fillets resulted in lower lipid oxidation and bacterial growth, therefore, could be natural food additive for preservation of fish fillets. 相似文献