全文获取类型
收费全文 | 6467篇 |
免费 | 357篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 86篇 |
综合类 | 10篇 |
化学工业 | 1290篇 |
金属工艺 | 185篇 |
机械仪表 | 317篇 |
建筑科学 | 125篇 |
矿业工程 | 2篇 |
能源动力 | 309篇 |
轻工业 | 578篇 |
水利工程 | 20篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 1068篇 |
一般工业技术 | 1273篇 |
冶金工业 | 700篇 |
原子能技术 | 57篇 |
自动化技术 | 808篇 |
出版年
2024年 | 10篇 |
2023年 | 83篇 |
2022年 | 117篇 |
2021年 | 207篇 |
2020年 | 157篇 |
2019年 | 150篇 |
2018年 | 181篇 |
2017年 | 180篇 |
2016年 | 211篇 |
2015年 | 189篇 |
2014年 | 295篇 |
2013年 | 410篇 |
2012年 | 429篇 |
2011年 | 465篇 |
2010年 | 347篇 |
2009年 | 335篇 |
2008年 | 368篇 |
2007年 | 278篇 |
2006年 | 221篇 |
2005年 | 217篇 |
2004年 | 184篇 |
2003年 | 159篇 |
2002年 | 147篇 |
2001年 | 116篇 |
2000年 | 111篇 |
1999年 | 116篇 |
1998年 | 278篇 |
1997年 | 179篇 |
1996年 | 152篇 |
1995年 | 97篇 |
1994年 | 72篇 |
1993年 | 72篇 |
1992年 | 34篇 |
1991年 | 26篇 |
1990年 | 26篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 24篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 14篇 |
1974年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有6837条查询结果,搜索用时 46 毫秒
91.
The overall non-isothermal crystallization kinetics for nucleated and non-nucleated isotactic polypropylene (iPP) in dotriacontane systems was investigated. Adipic acid was used as the nucleating agent. Crystallization peak temperature was determined via differential scanning calorimetry as a function of the experimentally controlled variables iPP concentration, cooling rate, and nucleating agent concentration. The influence of these variables on crystallization mechanism and spherulitic structure as implied by the Ozawa and Ziabicki analyses was determined. The non-isothermal crystallization kinetics presented here are the first for iPP-diluent systems with and without nucleating agent. 相似文献
92.
Summary The transient flow behavior of the binary blend of monodisperse polystyrene fractions is measured by a flow birefringence method. Both of the shear stress and first normal stress difference are obtained simultaneously in time by using a PMFB technique. The entanglements of the polymer chains significantly affect the rheological property of the binary blend in flow region. Especially, the entanglements of the high molecular weight fractions with themselves is proven to be the main source to the growth of first normal stress differences. 相似文献
93.
Hyun Ju Lim Sung Jun Lee Han Gon Choi Jung Ae Kim Chul Soon Yong Sung Soo Han Seok Kyun Noh Jinho Jang Won Seok Lyoo 《应用聚合物科学杂志》2007,106(5):3268-3272
High‐molecular‐weight atactic poly(vinyl alcohol) (a‐PVA) gels loaded with (R,S)‐2‐(3‐benzoylphenyl)propionic acid (ketoprofen) were prepared from 5, 6, 7, and 8 g/dL solutions of a‐PVA with a number‐average degree of polymerization of 4000 in an ethylene glycol/water mixture with an aging method to identify the effect of the initial polymer concentration on the swelling behavior, morphology, and thermal properties of a‐PVA gels. Then, the release behavior of ketoprofen from a‐PVA gels was investigated. As the polymer concentration decreased, the ability for network formation decreased, and the degree of swelling of the a‐PVA gels increased. In addition, the enthalpy increased with an increase in the a‐PVA concentration, but the melting temperatures of the gels prepared at different initial polymer concentrations were the same; this indicated that tighter gel networks would be formed by a higher polymer chain density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
94.
The simple criterion proposed by Chandnani and Epstein (1984, 1986) for stable spouting, dor/dp ≤ 25.4, is shown to give a good separation between gas-solid systems which form permanent jets and those that bubble, for a wide range of experimental data reported in the literature. The criterion is suggested as a necessary but not sufficient condition for permanent jet formation in fluidized, spout-fluid and spouted beds. 相似文献
95.
In the present investigation, we develop a method for estimating rheological parameters of viscoelastic fluids using velocity measurement in a square straight channel. It is believed that a somewhat complicated patterns of secondary flows due to the non-zero second normal stress difference are more useful than the simple viscometric flows traditionally adopted in the determination of rheological parameters. The inverse problem of determining the rheological parameters from a set of velocity measurements is solved using a conjugate gradient method. When applied to a general constitutive equation encompassing the UCM model, the Oldroyd-B model and the PTT model, the present method is found to yield a reasonably accurate estimation of five rheological parameters simultaneously even with noisy velocity measurements. 相似文献
96.
This study utilizes a two‐dimensional hydrodynamic model to calibrate and validate an inundation model for the Brisbane River estuary in Queensland, Australia. The bathymetry data used in the hydraulic model are derived from one arc second (1 s) shuttle radar topography mission digital elevation model, and the two‐dimensional hydraulic model is parameterized using the generated bathymetry with four open boundaries with water level observations and roughness coefficients. The calibration performance is evaluated by comparing the simulated results with the digitized records during the January 2013 flood event (a low magnitude event) at three gauging stations. The calibrated model is validated with water level data and available discharge data during the January 2011 flood (a large magnitude event) at four gauging stations located along the Brisbane River. Different performance indices are applied to demonstrate that the developed model performs well during calibration and validation. A sensitivity analysis is presented to assess the influence of riverbed elevation changes on the model because the main uncertainty of the model is the bathymetry data. The proposed model with the shuttle radar topography mission digital elevation model‐derived riverbed elevation for the Brisbane estuary is able to predict the flood inundation extent at an accuracy of 66.9% which is higher than or comparable with the accuracies of the existing studies. However, it is expected that the accuracy will increase if some improved bathymetry data become available in the future. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
97.
Rubber‐toughened polypropylene (PP)/org‐Montmorillonite (org‐MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twin‐screw extruder at 230°C and injection‐molded. The POE used had 25 wt % 1‐octene content and the weight fraction of POE in the blend was varied in the range of 0–20 wt %. X‐ray diffraction analysis (XRD) revealed that an intercalation org‐MMT silicate layer structure was formed in rubber‐toughened polypropylene nanocomposites (RTPPNC). Izod impact measurements indicated that the addition of POE led to a significant improvement in the impact strength of the RTPPNC, from 6.2 kJ/m2 in untoughened PP nanocomposites to 17.8 kJ/m2 in RTPPNC containing 20 wt % POE. This shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Young's modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two‐phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3441–3450, 2006 相似文献
98.
Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004 相似文献
99.
This paper proposes a tactile display providing both shear and normal feedback to the fingertip for generating three-axis tactile feedback during teleoperation of a surgical robot. The display is composed of five balloons actuated by controlling the pneumatic pressure. The implemented display is 18?mm?×?18?mm?×?15?mm. This size is suitable for mounting the display onto the master controls of a surgical robot. The maximum normal and shear displacements are 2 and 1.3?mm, respectively. The proposed tactile display may provide perceivable stimuli to a human finger pad in all five directions: normal, distal, proximal, radial, and ulnar. This paper also reports on the results of psychophysical measurement of the minimum perceivable movement of the developed tactile display for each of the five directions. 相似文献
100.
Ting Yee Lim 《Artificial Intelligence Review》2014,41(3):385-399
The Genetic Algorithm (GA) has been one of the most studied topics in evolutionary algorithm literature. Mimicking natural processes of inheritance, mutation, natural selection and genetic operators, GAs have been successful in solving various optimization problems. However, standard GA is often criticized as being too biased in candidate solutions due to genetic drift in search. As a result, GAs sometimes converge on premature solutions. In this paper, we survey the major advances in GA, particularly in relation to the class of structured population GAs, where better exploration and exploitation of the search space is accomplished by controlling interactions among individuals in the population pool. They can be classified as spatial segregation, spatial distance and heterogeneous population. Additionally, secondary factors such as aging, social behaviour, and so forth further guide and shape the reproduction process. Restricting randomness in reproduction has been seen to have positive effects on GAs. It is our hope that by reviewing the many existing algorithms, we shall see even better algorithms being developed. 相似文献