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排序方式: 共有2262条查询结果,搜索用时 31 毫秒
961.
Mehmet A. Oturan Elodie Guivarch Nihal Oturan Ignasi Sirs 《Applied catalysis. B, Environmental》2008,82(3-4):244-254
A very detailed scheme for the Fe3+-catalyzed electro-Fenton mineralization of malachite green as a model triarylmethane dye is presented. Bulk electrolyses of 250-mL aqueous solutions of 0.5 mM malachite green with 0.2 mM Fe3+ as catalyst have been carried out at room temperature and pH 3.0 under constant current in an undivided cell equipped with a graphite-felt cathode and a Pt anode to assess the performance of the electro-Fenton system. In situ electrogeneration of Fe2+ and H2O2 from quick cathodic reduction of Fe3+ and dissolved O2 (from bubbled compressed air), respectively, allows the formation of the very oxidizing species hydroxyl radical (OH) in the medium from Fenton's reaction. A pseudo-first-order decay kinetics with an apparent rate constant of k1,MG = 0.244 min−1 was obtained for total destruction of malachite green by action of OH at 200 mA, requiring 22 min for total decoloration of the solution. In the same experimental conditions, overall mineralization was reached at 540 min. Up to 15 aromatic and short-chain carboxylic acid intermediates were identified along the treatment. The evolution of current efficiency was calculated from the chemical oxygen demand (COD) removal. Based on the time course of most of the by-products and the identification of inorganic ions released, some plausible mineralization pathways are proposed and thoroughly discussed. It has been found that the electro-Fenton degradation of malachite green proceeds via parallel pathways, all of them involving primary splitting of the triaryl structure initiated by attack of OH on the central carbon, thus yielding two different N-dimethylated benzophenones. Successive cleavage of the aromatic intermediates generates oxalic acid as the ultimate short-chain carboxylic acid, whereas N-demethylation of some of them produces formic acid as well. Oxalic acid and its Fe2+ complexes, as well as formic acid, can be slowly but totally mineralized by OH. 相似文献
962.
Kürkcü M Benlidayi ME Ozsoy S Ozyeğin LS Oktar FN Kurtoğlu C 《Journal of materials science. Materials in medicine》2008,19(1):59-65
Objectives The aim of this study was to compare osseous healing characteristics of titanium implants coated with enamel-derived fluoride-substituted
apatite (EFSA) or dentin-derived fluoride-substituted apatite (DFSA).
Methods Fluoride-substituted apatite was derived from extracted human teeth with calcination method at 850 °C. DFSA and EFSA were
separated and carefully ground with a blade grinder. Twenty-four titanium implants were prepared from a 99.99% pure titanium
bar. EFSA and DFSA powders were sprayed separately on implants. As control group, unsprayed and sandblasted pure titanium
implants were used. Eight adult rams were used in the study. One EFSA coated, 1 DFSA coated and 1 control implants were placed
into right tibia of each rams. The rams were sacrificed after 6 months of healing. Undecalcified sections were prepared according
to Donath’s method and histomorphometric evaluation of implants was made.
Results The mean bone contact percentage of DFSA-coated, EFSA-coated and control implants was 89.88% ± 2.34, 70.19% ± 13.11 and 53.12% ± 5.76
respectively. This study suggests that DFSA-coated implants achieved better bone contact than EFSA-coated implants (P < 0.05). Also study groups presented better bone contact than control group (P < 0.05).
Conclusions The results of this study show that although DFSA-coated implants achieved better bone contact, both DFSA and EFSA can be
considered as appropriate coating materials. 相似文献
963.
Acir N Oztura I Kuntalp M Baklan B Güzeliş C 《IEEE transactions on bio-medical engineering》2005,52(1):30-40
This paper introduces a three-stage procedure based on artificial neural networks for the automatic detection of epileptiform events (EVs) in a multichannel electroencephalogram (EEG) signal. In the first stage, two discrete perceptrons fed by six features are used to classify EEG peaks into three subgroups: 1) definite epileptiform transients (ETs); 2) definite non-ETs; and 3) possible ETs and possible non-ETs. The pre-classification done in the first stage not only reduces the computation time but also increases the overall detection performance of the procedure. In the second stage, the peaks falling into the third group are aimed to be separated from each other by a nonlinear artificial neural network that would function as a postclassifier whose input is a vector of 41 consecutive sample values obtained from each peak. Different networks, i.e., a backpropagation multilayer perceptron and two radial basis function networks trained by a hybrid method and a support vector method, respectively, are constructed as the postclassifier and then compared in terms of their classification performances. In the third stage, multichannel information is integrated into the system for contributing to the process of identifying an EV by the electroencephalographers (EEGers). After the integration of multichannel information, the overall performance of the system is determined with respect to EVs. Visual evaluation, by two EEGers, of 19 channel EEG records of 10 epileptic patients showed that the best performance is obtained with a radial basis support vector machine providing an average sensitivity of 89.1%, an average selectivity of 85.9%, and a false detection rate (per hour) of 7.5. 相似文献
964.
Hexavalent chromium removal by ferrochromium slag 总被引:1,自引:0,他引:1
The aim of this study is to demonstrate the potential of Cr(VI) generation during jigging operation applied for ferrochrome recovery from slag. The Cr(VI) concentrations of water contacted with ferrochromium slag (W/FS=10) in a closed cycle after 50 batches were found as 0.61 mg/l. Also, reduction of Cr(VI) to Cr(III) and a subsequent precipitation of Cr(III) by using ferrochrome slag (FS) in a model solution has been aimed. The effects of amount of acid, contact time, FS dosage, initial Cr(VI) concentration and temperature on the Cr(VI) reduction have been studied through the batch runs. The amount of acid has been found to be the most effective parameter affecting the Cr(VI) reduction. A 10 g/l FS dosage and 3.5 ml/l H2SO4 (5M) are sufficient to reduce all Cr(VI) in the model solution containing 10mg/l Cr(VI) and for contact time of 60 min at 25 degrees C. In reduced solutions, precipitation of metal ions has been studied by using extra FS. A 60 g/l dosage of fresh FS can precipitate all Cr(III) and Fe ions in the reduced solution. Thus, it has been demonstrated that the treatment of jigging water stream to be generated in a ferrochrome plant containing Cr(VI) can be accomplished by using ferrochromium slag and sulphuric acid. Also, it has been determined that solid residues of the process are environmentally stable by applying TCLP test. 相似文献
965.
We have developed a simple and robust method to fabricate nanoarrays of metals and metal oxides over macroscopic substrates using the crystalline surface layer (S-layer) protein of Deinococcus radiodurans as an electrodeposition mask. Substrates are coated by adsorption of the S-layer from a detergent-stabilized aqueous protein extract, producing insulating masks with 2-3 nm diameter solvent-accessible openings to the deposition substrate. The coating process can be controlled to achieve complete or fractional surface coverage. We demonstrate the general applicability of the technique by forming arrays of cuprous oxide (Cu(2)O), Ni, Pt, Pd, and Co exhibiting long-range order with the 18 nm hexagonal periodicity of the protein openings. This protein-based approach to electrochemical nanofabrication should permit the creation of a wide variety of two-dimensional inorganic structures. 相似文献
966.
Kemal?Sagduyu Mehmet?E?DokucuEmail author Bruce?A?Eddy Gerald?Craigen Claudia?F?Baldassano Ay?egül?Y?ld?z 《Nutrition journal》2005,4(1):6
This is a report on a 37-patient continuation study of the open ended, Omega-3 Fatty Acid (O-3FA) add-on study. Subjects consisted
of the original 19 patients, along with 18 new patients recruited and followed in the same fashion as the first nineteen.
Subjects carried a DSM-IV-TR diagnosis of Bipolar Disorder and were visiting a Mood Disorder Clinic regularly through the
length of the study. At each visit, patients' clinical status was monitored using the Clinical Monitoring Form. Subjects reported
on the frequency and severity of irritability experienced during the preceding ten days; frequency was measured by way of
percentage of days in which subjects experienced irritability, while severity of that irritability was rated on a Likert scale
of 1 – 4 (if present). The irritability component of Young Mania Rating Scale (YMRS) was also recorded quarterly on 13 of
the 39 patients consistently. Patients had persistent irritability despite their ongoing pharmacologic and psychotherapy. 相似文献
967.
Berkun M 《Water research》2005,39(20):41-5016
Copper mine tailings are discharged to the anoxic zone of the Black Sea at 350 m depth, and there is currently consideration of reducing this discharge depth. Oceanographic sampling has provided data allowing calculating whether dilute buoyant plumes will separate from the tailings density current as predicted. Calculations for various discharge rates and slurry dilutions indicate that such plumes will rise 89 m above the discharge depth, hence will remain in the deep anoxic zone below the permanent pycnocline at 150 m depth at both the present and currently proposed sites. There is some indication from relative seawater density measures that these plumes will drift rather than spreading diffusely. Plume separation from controlled discharges of the tailings slurry was confirmed by visual observations in an experimental tank. The oceanographic sampling also showed that trace element levels in the seawater by the discharge point remained below Turkish marine receiving water quality criteria. 相似文献
968.
Ariksoysal DO Karadeniz H Erdem A Sengonul A Sayiner AA Ozsoz M 《Analytical chemistry》2005,77(15):4908-4917
The resistance analysis related to the hepatitis B virus (HBV) genotyping and treatment procured key information for the study of infected patients. The aim of this study was to develop a novel assay for the voltammetric detection of DNA sequences related to the HBV genotype on the development of lamuvidine resistance by monitoring the oxidation signal of guanine. This new technique not only provides a rapid, cost-effective, simple analysis but also gives information concerning both genotyping and lamivudine resistance. Synthetic single-stranded oligonucleotides ("probe") including YMDD (HBV wild type) YVDD, or YIDD (mutations in the YMDD) variants have been immobilized onto pencil graphite electrodes with the adsorption at a controlled potential. The probes were hybridized with different concentrations of their complementary ("target") sequences such as synthetic complementary sequences, clonned PCR products, or real PCR samples. The formed synthetic hybrids on the electrode surface were evaluated by a differential pulse voltammetry technique using a label-free detection method. The oxidation signal of guanine was observed as a result of the specific hybridization between the probes and their synthetic targets and specific PCR products. The response of the hybridization of the probes with their single-base mismatch oligonucleotides at PGE was also detected. Control experiments using the noncomplementary oligonucleotides were performed to determine whether the DNA genosensor responds selectively. Numerous factors, affecting the probe immobilization, target hybridization, and nonspecific binding events, were optimized to maximize the sensitivity and reduce the assay time. Under the optimum conditions, 457 fmol/mL was found as the detection limit for target DNA. With the help of the appearance of the guanine signal, the new protocol is based on the electrochemical detection of HBV genotype for the development of lamuvidine resistance for the first time. Features of this protocol are discussed and optimized. 相似文献
969.
Artur?AndrzejakEmail author Mehmet?Ceyran 《Journal of Network and Systems Management》2005,13(2):175-196
We present algorithms for characterizing the demand behavior of applications and predicting demand by mining periodicities in historical data. Our algorithms are change-adaptive, automatically adjusting to new regularities in demand patterns while maintaining low algorithm running time. They are intended for applications in scientific computing clusters, enterprise data centers, and Grid and Utility environments that exhibit periodical behavior and may benefit significantly from automation. A case study incorporating data from an enterprise data center is used to evaluate the effectiveness of our technique.Artur Andrzejak received the PhD degree in computer science from the Swiss Federal Institute of Technology (ETH Zurich) in 2000. He is currently a researcher at Zuse-Institute Berlin, Germany. He was a postdoctoral researcher at the Hewlett-Packard Labs in Palo Alto, California, from 2001 to 2002. His research interests include systems management and modeling, and Grids.Mehmet Ceyran is working toward his Masters Degree in Computer Science at the Freie Universität Berlin, Germany. He has been employed as a student programmer at Zuse-Institute Berlin since 2003. His research interests include software engineering, systems management, and artificial intelligence. 相似文献
970.
Kuntalp M 《Network (Bristol, England)》2005,16(1):55-84
The aim of this study is to investigate via computation whether the olivocerebellar system is capable of functioning as an adaptive rhythm generator. For this purpose, a detailed and physiologically realistic computational model of the olivocerebellar system is developed, based on the known intrinsic cell and network topological properties of this brain system. The present network, where individual cells are modelled by leaky integrate-and-fire units, converts the irregular spikes produced by the olivary cells into a precise rhythmic signal at the output. The simulation results reveal that the computational model, which normally does not exhibit any rhythmic activity, could be switched into a new mode in which it functions as a rhythm generator producing pulses within three different frequency ranges corresponding to alpha, beta, or gamma bands, respectively. In either mode of operation, the firing rates of all simulated cell types are observed to match real data. The results of this study therefore support the experimental findings of researchers who argue that a biological clock producing rhythmic pulses within different temporal ranges is located within the cerebellum. 相似文献