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991.
Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are essential for neuronal survival and growth. The signaling cascades initiated by BDNF and its receptor are the key regulators of synaptic plasticity, which plays important role in learning and memory formation. Changes in BDNF levels and signaling pathways have been identified in several neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease, and have been linked with the symptoms and course of these diseases. This review summarizes the current understanding of the role of BDNF in several neurodegenerative diseases, as well as the underlying molecular mechanism. The therapeutic potential of BDNF treatment is also discussed, in the hope of discovering new avenues for the treatment of neurodegenerative diseases. 相似文献
992.
Nur Azalina Suzianti Feisal Noor Haziqah Kamaludin Muhammad Firdaus Abdullah Sani Dayang Khairulnisa Awang Ahmad Mohd Azwan Ahmad Nur Faiza Abdul Razak Tengku Nilam Baizura Tengku Ibrahim 《水科学与水工程》2023,16(3):234-242
Malaysia's rapid economic and demographic development have placed negative pressure on its water supplies and the quality of the Juru River, which is close to the nation's capital and its major source of water. Healthy aquatic ecosystems are supported by physicochemical properties and biological diversity. This study evaluated the anthropogenic impacts on aquatic biodiversity, especially plankton, fish, and macrobenthos, as well as the water quality of the Juru River in the Penang area. Aquatic biodiversity and river water parameters were collected from ten sampling stations along the Juru River. Seven variables were used to assess the physicochemical environment: pH, temperature, total suspended solids (TSS), salinity, dissolved oxygen (DO), biochemical oxygen demand (BOD), and chemical oxygen demand. At each sampling station, the total number of plankton, fish, and macrobenthic taxa were counted and analyzed. The relationships between the physicochemical parameters and aquatic biodiversity were investigated with biotypological analysis, principal component analysis, hierarchical cluster analysis, and linear regression analysis. These analyses showed that the richness and diversity indices were generally influenced by salinity, temperature, TSS, BOD, and pH. The data obtained in this study supported the bioindicator concept. The findings, as they related to scientifically informed conservation, could serve as a model for Juru River management, as well as for river management throughout Malaysia and other tropical Asian countries. 相似文献
993.
Kok Whye Cheong Chin Ping Tan Hamed Mirhosseini Sung Tong Chin Yaakob B. Che Man Nazimah Sheikh Abdul Hamid Azizah Osman Mahiran Basri 《Food chemistry》2011
Headspace solid-phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was applied for equilibrium headspace analysis of Malaysian soursop (Annona muricata) volatile flavor compounds. A two-level fractional factorial design (25-1) was used to determine the effect of SPME variables, namely, SPME fibers, adsorption temperature, extraction time, amount of salt, sample amount and sample concentration on the extraction efficiency of volatile flavor compounds. A total of 37 volatile compounds were identified, comprising 21 esters, 6 alcohols, 3 terpenes, 2 acids, 2 ketones, 2 aldehydes and an aromatic with different hydrophobicities (log P) ranging between −0.14 and 4.83. Extraction using 10 g of diluted (5% w/w) blended soursop pulp with CAR/PDMS fiber at 25 °C for 30 min and 30% (w/w) of NaCl under stirring mode resulted in the highest extraction efficiency of volatile flavor compounds. The principal component analysis score discriminated the influence of SPME variables on the equilibrium headspace concentration of target volatile compounds. 相似文献
994.
M. A. Motalib Hossain Syed Muhammad Kamal Uddin Zaira Zaman Chowdhury Sharmin Sultana Mohd Rafie Johan Abdul Rohman 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2019,36(4):493-506
Mislabelling in fish products is a highly significant emerging issue in world fish trade in terms of health and economic concerns. DNA barcoding is an efficient sequencing-based tool for detecting fish species substitution but due to DNA degradation, it is in many cases difficult to amplify PCR products of the full-length barcode marker (~650 bp), especially in severely processed products. In the present study, a pair of universal primers targeting a 198 bp sequence of the mitochondrial 16s rRNA gene was designed for identification of fish species in the processed fish products commonly consumed in Malaysia. The specificity of the universal primers was tested by both in-silico studies using bioinformatics software and through cross-reaction assessment by practical PCR experiments against the DNA from 38 fish species and 22 other non-target species (animals and plants) and found to be specific for all the tested fish species. To eliminate the possibility of any false-negative detection, eukaryotic endogenous control was used during specificity evaluation. The developed primer set was validated with various heat-treated (boiled, autoclaved and microwaved) fish samples and was found to show high stability under all processing conditions. The newly developed marker successfully identified 92% of the tested commercial fish products with 96–100% sequence similarities. This study reveals a considerable degree of species mislabelling (20.8%); 5 out of 24 fish products were found to be mislabelled. The new marker developed in this work is a reliable tool to identify fish species even in highly processed products and might be useful in detecting fish species substitution thus protecting consumers’ health and economic interests. 相似文献
995.
High altitude platform station (HAPS) is an innovative technology which delivers some unique features, contrary to conventional communications networks, such as fixed satellite service (FSS). The absence of confirmed spectrum emission mask (SEM) of HAPS and its diversity to work within FSS networks are significant issues in evaluating the coexistence of HAPS and FSS. At this juncture, a practical SEM for HAPS gateway links is proposed which will endeavor to assess its functionality and its ability to coexist with FSS. HAPS SEM’s impact on coexistence issues are exposed upon consideration of criteria such as MD, NFD and ACIR. These facets are well-described and their measured amounts for specific applicable SEMs are proposed. Therefore, reckoning process regarding these factors is ascertained. It must be said that the remarked criteria and their amounts for HAPS gateway links are unprecedented. The simulation parameters are well organized based upon International Telecommunication Union and World Radiocommunications Conferences periodicals. The aim of this article is to shed more light on the associated facets of the HAPS network spectrum and their impressions on HAPS and FSS networks coexistence. The assessments have been performed for HAPS gateway links in the 5,850–7,075 MHz frequency band where FSS uplink frequency band in C-band (5,925–6,725 MHz) partially intrude with HAPS gateway links. Therefore, HAPS gateway links channelization regarding FSS uplink channel is appraised and light is shed on the impact of HAPS and FSS coexisting in the same frequency band. 相似文献
996.
Nazim Abdul Nariman 《Frontiers of Structural and Civil Engineering》2017,11(1):66-89
This paper studies optimization of three design parameters (mass ratio, frequency ratio and damping ratio) of multiple tuned mass dampers MTMDs that are applied in a cable stayed bridge excited by a strong wind using minimax optimization technique. ABAQUS finite element program is utilized to run numerical simulations with the support of MATLAB codes and Fast Fourier Transform FFT technique. The optimum values of these three parameters are validated with two benchmarks from the literature, first with Wang and coauthors and then with Lin and coauthors. The validation procedure detected a good agreement between the results. Box-Behnken experimental method is dedicated to formulate the surrogate models to represent the control efficiency of the vertical and torsional vibrations. Sobol’s sensitivity indices are calculated for the design parameters in addition to their interaction orders. The optimization results revealed better performance of the MTMDs in controlling the vertical and the torsional vibrations for higher mode shapes. Furthermore, the calculated rational effects of each design parameter facilitate to increase the control efficiency of the MTMDs in conjunction with the support of the surrogate models. 相似文献
997.
Estimation of Clark’s Instantaneous Unit Hydrograph Parameters and Development of Direct Surface Runoff Hydrograph 总被引:1,自引:1,他引:1
Muhammad Masood Ahmad Abdul Razzaq Ghumman Sajjad Ahmad 《Water Resources Management》2009,23(12):2417-2435
We present a method to estimate Time of Concentration (T
c) and Storage Coefficient (R) to develop Clark’s Instantaneous Unit Hydrograph (CIUH). T
c is estimated from Time Area Diagram of the catchment and R is determined using optimization approach based on Downhill Simplex technique (code written in FORTRAN). Four different objective
functions are used in optimization to determine R. The sum of least squares objective function is used in a novel way by relating it to slope of a linear regression best fit
line drawn between observed and simulated peak discharge values to find R. Physical parameters (delineation, land slope, stream lengths and associated drainage areas) of the catchment are derived
from SPOT satellite imageries of the basin using ERDAS: Arc GIS is used for geographic data processing. Ten randomly selected
rainfall–runoff events are used for calibration and five for validation. Using CIUH, a Direct surface runoff hydrograph (DSRH)
is developed. Kaha catchment (5,598 km2), part of Indus river system, located in semi-arid region of Pakistan and dominated by hill torrent flows is used to demonstrate
the applicability of proposed approach. Model results during validation are very good with model efficiency of more than 95%
and root mean square error of less than 6%. Impact of variation in model parameters T
c and R on DSRH is investigated. It is identified that DSRH is more sensitive to R compared to T
c. Relatively equal values of R and T
c reveal that shape of DSRH for a large catchment depends on both runoff diffusion and translation flow effects. The runoff
diffusion effect is found to be dominant. 相似文献
998.
Jafar Ali Abdul Hameed Safia Ahmed Muhammad Ishtiaq Ali Shama Zainab Naeem Ali 《IET nanobiotechnology / IET》2016,10(5):295
Biological routes of synthesising metal nanoparticles (NPs) using microbes have been gaining much attention due to their low toxicity and eco‐friendly nature. Pseudomonas aeruginosa JP2 isolated from metal contaminated soil was evaluated towards extracellular synthesis of silver NPs (AgNPs). Cell‐free extract (24 h) of the bacterial isolate was reacted with AgNO3 for 24 h in order to fabricate AgNPs. Preliminary observations were recorded in terms of colour change of the reaction mixture from yellow to greyish black. UV‐visible spectroscopy of the reaction mixture has shown a progressive increase in optical densities that correspond to peaks near 430 nm, depicting reduction of ionic silver (Ag+) to atomic silver (Ag0) thereby synthesising NPs. X‐ray diffraction spectra exhibited the 2θ values to be 38.4577° confirming the crystalline and spherical nature of NPs [9.6 − 26.7 (Ave. = 17.2 nm)]. Transmission electron microscopy finally confirmed the size of the particles varying from 5 to 60 nm. Moreover, rhamnolipids and proteins were identified as stabilising molecules for the AgNPs through Fourier transform‐infrared spectroscopy. Characterisation of bacterial crude and purified protein fractions confirmed the involvement of nitrate reductase (molecular weight 66 kDa and specific activity = 3.8 U/mg) in the Synthesis of AgNPs.Inspec keywords: microorganisms, silver, nanoparticles, enzymes, molecular biophysics, ultraviolet spectra, visible spectra, X‐ray diffraction, transmission electron microscopy, Fourier transform infrared spectra, catalysis, biochemistry, nanobiotechnologyOther keywords: catalytic protein, stabilising agents, Pseudomonas aeruginosa, metal nanoparticles, UV–visible spectroscopy, optical densities, ionic silver, atomic silver, X‐ray diffraction spectra, transmission electron microscopy, nitrate reductase, rhamnolipids, Fourier transform‐infrared spectroscopy, Ag 相似文献
999.
The exponentially weighted moving average (EWMA) control chart is a memory‐type process monitoring tool that is frequently used to monitor small and moderate disturbances in the process mean and/or process dispersion. In this study, we propose 2 new memory‐type control charts for monitoring changes in the process dispersion, namely, the generally weighted moving average and the hybrid EWMA charts. We use Monte Carlo simulations to compute the run length profiles of the proposed control charts. The run length comparisons of the proposed and existing charts reveal that the generally weighted moving average and hybrid EWMA charts provide better protection than the existing EWMA chart when detecting small to moderate shifts in the process dispersion. An illustrative dataset is also used to show the superiority of the proposed charts over the existing chart. 相似文献
1000.
Optical properties and crystallinity of hydrogenated nanocrystalline silicon (nc-Si:H) thin films deposited by rf-PECVD 总被引:1,自引:0,他引:1
Hydrogenated nanocrystalline silicon (nc-Si:H) thin films prepared in a home-built radio-frequency (rf) plasma enhanced chemical vapour deposition (PECVD) system have been studied. The rf powers were fixed in the range of 5 W-80 W. The optical properties and crystallinity of the films were studied by X-ray diffraction (XRD), Micro-Raman scattering spectroscopy, high resolution transmission electron microscope (HRTEM), and optical transmission and reflection spectroscopy. The XRD and Micro-Raman scattering spectra were used to investigate the evidence of crystallinity in order to determine the crystallite sizes and crystalline volume fraction in the films. The HRTEM image of the film was used to correlate with the crystallinity that was determined from XRD and Micro-Raman scattering spectra. Optical constants such as refractive index, optical energy gap, Tauc slope, Urbach energy and ionic constants were obtained from the optical transmission and reflectance spectra. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of rf power. Also, the ionic constants of the films showed an indication of the degree of crystallinity in the films. The variation of the optical energy gap with the rf power based on structure disorder and the quantum confinement effect is discussed. 相似文献