全文获取类型
收费全文 | 5982篇 |
免费 | 378篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 125篇 |
综合类 | 4篇 |
化学工业 | 1364篇 |
金属工艺 | 239篇 |
机械仪表 | 387篇 |
建筑科学 | 113篇 |
矿业工程 | 2篇 |
能源动力 | 335篇 |
轻工业 | 511篇 |
水利工程 | 23篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 945篇 |
一般工业技术 | 1435篇 |
冶金工业 | 302篇 |
原子能技术 | 65篇 |
自动化技术 | 523篇 |
出版年
2024年 | 2篇 |
2023年 | 69篇 |
2022年 | 82篇 |
2021年 | 165篇 |
2020年 | 151篇 |
2019年 | 141篇 |
2018年 | 190篇 |
2017年 | 185篇 |
2016年 | 211篇 |
2015年 | 157篇 |
2014年 | 266篇 |
2013年 | 357篇 |
2012年 | 443篇 |
2011年 | 508篇 |
2010年 | 356篇 |
2009年 | 407篇 |
2008年 | 366篇 |
2007年 | 302篇 |
2006年 | 228篇 |
2005年 | 218篇 |
2004年 | 182篇 |
2003年 | 161篇 |
2002年 | 165篇 |
2001年 | 132篇 |
2000年 | 133篇 |
1999年 | 108篇 |
1998年 | 143篇 |
1997年 | 120篇 |
1996年 | 87篇 |
1995年 | 73篇 |
1994年 | 46篇 |
1993年 | 45篇 |
1992年 | 28篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1979年 | 3篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有6381条查询结果,搜索用时 156 毫秒
991.
The objective of this study was to model the effect of drying temperatures (52, 57, and 63 degrees C) and predrying treatments on the inactivation of Listeria monocytogenes on beef jerky. Before drying, beef slices were inoculated with a 10-strain composite of L. monocytogenes and then treated with the following: (i) nothing (C), (ii) traditional marinade (M), or (iii) dipping in 5% acetic acid solution for 10 min, followed by M (AM). In addition, sequential stresses (exposure to 10% NaCl, followed by an adjustment of the pH to 5.0 and, subsequently, a water bath at 45 degrees C) were applied to the inocula before beef contamination and drying at 63 degrees C. Surviving L. monocytogenes were determined on tryptic soy agar plus 0.6% yeast extract (TSAYE) and on PALCAM agar at 0, 2, 4, 6, 8, and 10 h during drying. Data were modeled by a linear regression (treatment AM) and a logistic-based equation capable of fitting biphasic inactivation curves without initial shoulder (treatments C and M). The total log reductions expressed as the CFU per square centimeter of L. monocytogenes (3.9 to 5.1) for the samples treated with M (3.5 to 5.4) when compared with C were similar, whereas AM-treated samples had higher (6.1 to 6.8) reductions. All survival curves were characterized by an initial rapid decrease in populations within the first 2 h, which was followed by a secondary death phase at a lower rate. No significant (P > or = 0.05) differences in inactivation were observed due to drying temperatures in the range (52 to 63 degrees C) tested. Inactivation differences between recovered counts of stressed and unstressed cells were significant (P < 0.05) in PALCAM but not in TSAYE. The acidified predrying treatment (AM) had higher pathogen inactivation during drying than other treatments, regardless of drying temperature. The models developed may be useful in designing effective drying processes for beef jerky. 相似文献
992.
We present a method for glucose prediction from mid-IR spectra by independent component analysis (ICA). This method is able to identify pure, or individual, absorption spectra of constituent components from the mixture spectra without a priori knowledge of the mixture. This method was tested with a two-component system consisting of an aqueous solution of both glucose and sucrose, which exhibit distinct but closely overlapped spectra. ICA combined with principal component analysis was able to identify a spectrum for each component, the correct number of components, and the concentrations of the components in the mixture. This method does not need a calibration process and is advantageous in noninvasive glucose monitoring since expensive and time-consuming clinical tests for data calibration are not required. 相似文献
993.
994.
Yoon TH Benzerara K Ahn S Luthy RG Tyliszczak T Brown GE 《Environmental science & technology》2006,40(19):5923-5929
Synchrotron-based soft X-ray spectromicroscopy was used to probe nanometer-scale chemical heterogeneities of black carbon (BC) materials, including anthracite coal, coke, and activated carbon (AC), and to study their impact on the partitioning of one type of polychlorinated biphenyls (PCB-166: 2,3,4,4',5,6 hexachloro biphenyl) onto AC particles. Various carbon species (e.g., aromatic, ketonic/ phenolic, and carboxylic functional groups) were found in all of the BC materials examined, and impurities (e.g., carbonate and potassium ions in anthracite coal) were identified in nanometer-scale regions of these samples. We show that these chemical heterogeneities in AC particles influence their sorption of hydrophobic organic compounds (HOCs). PCB-166 was found to accumulate preferentially on AC particles with the highest content of aromatic functionalities. These new findings from X-ray spectromicroscopy have the following implications for the role of BC materials in the environment: (1) the functional groups of BC materials vary on a 25-nanometer scale, and so does the abundance of the HOCs; (2) molecular-level characterization of HOC sorption preferences on AC will lead to an improved understanding of AC sorption properties for the remediation of HOCs in soils and sediments. 相似文献
995.
Leem CH Kim WT Ha JM Lee YJ Seong HC Choe H Jang YJ Youm JB Earm YE 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2006,364(1842):1223-1243
In recent studies, we recorded transiently activated outward currents by the application of three-step voltage pulses to induce a reverse mode of Na+-Ca2+ exchange (NCX). We found that these currents were mediated by a Ca2+-activated Cl- current. Based on the recent reports describing the atrial Ca2+ transients, the Ca2+ transient at the subsarcolemmal space was initiated and then diffused into the cytosolic space. Because the myocardium in the pulmonary vein is an extension of the atrium, the Ca2+-activated Cl- current may reflect the subsarcolemmal Ca2+ dynamics. We tried to predict the subsarcolemmal Ca2+ dynamics by simulating these current traces. According to recent reports on the geometry of atrial myocytes, we assumed that there were three compartments of sarcoplasmic reticulum (SR): a network SR, a junctional SR and a central SR. Based on these structures, we also divided the cytosolic space into three compartments: the junctional, subsarcolemmal and cytosolic spaces. Geometry information and cellular capacitance suggested that there were essentially no T-tubules in these cells. The basic physical data, such as the compartmental volumes, the diffusion coefficients and the stability coefficients of the Ca2+ buffers, were obtained from the literature. In the simulation, we incorporated the NCX, the L-type Ca2+ channel, the rapid activating outward rectifier K+ channel, the Na+-K+ pump, the SR Ca2+-pump, the ryanodine receptor, the Ca2+-activated Cl- channel and the dynamics of Na+, K+, Ca2+ and Cl-. In these conditions, we could successfully reconstruct the Ca2+-activated Cl- currents. The simulation allowed estimation of the Ca2+ dynamics of each compartment and the distribution of the Ca2+-activated Cl- channel and the NCX in the sarcolemma on the junctional or subsarcolemmal space. 相似文献
996.
Liquid-ordered (L(O)) domains reconstituted in model membranes have provided a useful platform for in vitro studies of the lipid-raft model, in which signalling membrane molecules are thought to be compartmentalized in sphingolipid- and cholesterol-rich domains. These in vitro studies, however, have relied on an uncontrolled phase-separation process that gives a random distribution of L(O) domains. Obviously, a precise control of the size and spatial distribution of the L(O) domains would enable a more systematic large-scale in vitro study of the lipid-raft model. The prerequisite for such capability would be the generation of a well-defined energy landscape for reconstituting the L(O) domain without disrupting the two-dimensional (2D) fluidity of the model membrane. Here we report controlling the reconstitution of the L(O) domains in a spatially selective manner by predefining a landscape of energy barriers using topographic surface modifications. We show that the selective reconstitution spontaneously arises from the 2D brownian motion of nanoscale L(O) domains and signalling molecules captured in these nanodomains, which in turn produce a prescribed, concentrated downstream biochemical process. Our approach opens up the possibility of engineering model biological membranes by taking advantage of the intrinsic 2D fluidity. Moreover, our results indicate that the topographic configuration of cellular membranes could be an important machinery for controlling the lipid raft in vivo. 相似文献
997.
A water quality model applicable to rice paddies was developed using field data from 1999-2002. Use of the Dirac delta function efficiently explained the nutrient-concentration characteristics of ponded water. The model results agreed reasonably well with the observed data. The ponded-water quality was influenced primarily by fertilization; nutrient concentration was especially high during early cultivation periods. Reducing surface drainage during the fertilization period may substantially reduce nonpoint source loading from paddies. Increased weir heights and shallow irrigation methods were evaluated by the model as practical methods for reducing nutrient loading from paddies. These methods were effective in reducing surface drainage and are suggested as "best management practices" (BMPs) if applied based on site-specific paddy conditions. 相似文献
998.
Dong-Gyu Ahn Dae-Won Kim Yeol-Ui Yoon 《Journal of Mechanical Science and Technology》2010,24(1):145-148
The objective of this paper is to examine the influence of injection molding parameters on the core shift to obtain the optimal
injection molding conditions of a plastic battery case with thin and deep walls using numerical analyses and experiments.
Unlike conventional injection molding analysis, the flexible parts of the mold were represented by 3-D tetrahedron meshes
to consider the core shift in the numerical analysis. The design of experiments (DOE) was used to estimate the proper molding
conditions that minimize the core shift and a dominant parameter. The results of the DOE showed that the dominant parameter
is the injection pressure, and the core shift decreases when the injection pressure decreases. In addition, it was shown that
the initial mold temperature and the injection time hardly affect the core shift. The results of the experiments showed that
products without warpage are manufactured when the injection pressure is nearly 32 MPa. Comparing the results of the analyses
with those of the experiments, optimal injection molding conditions were determined. In addition, it was shown that the core
shift should be considered to simulate the injection molding process of a plastic battery case with thin and deep walls. 相似文献
999.
Jae Ho Cho Atul Kulkarni Hojoong Kim Jin Uk Yoon Jae Hyuck Sung Il Je Yu Taesung Kim 《Journal of Mechanical Science and Technology》2010,24(11):2215-2220
Silver nanoparticles are among the fastest growing product categories in the nanotechnology industry. Several experimental studies reported earlier for its toxicity and its associated risks. Uniform distribution of nanoparticle concentration in inhalation toxicity exposure chambers is important in the conduct of inhalation experimental evaluation. However, relatively little is known. Several factors, including nanoparticle size, degree of mixing, and chamber design, may influence the nanoparticles distribution in whole-body exposure chamber. In the present work we investigated numerically the silver nanoparticles concentration distribution and particle trajectory in the whole body inhalation toxicity test chamber. A three dimensional numerical simulation was performed using the commercially available computational fluid dynamics code Fluent with two models, discrete phase model (DPM) and fine particle model (FPM) to calculate spatial particle trajectories and concentration. The simulated results show that the silver nanoparticle trajectories and concentration distribution are dependent on inhalation toxicity chamber geometry. 相似文献
1000.
Kyung-Beom Yoon Hee-Chul Chang Tae-Kuk Kim 《Journal of Mechanical Science and Technology》2010,24(7):1531-1536
In this study the modified weighted sum of gray gases model (WSGGM) using the gray gas regrouping technique and the discrete
ordinates interpolation method (DOIM) are applied to analyze the radiative transfer within an irregular 3-D enclosure filled
with non-gray gas mixture of CO2, H2O and N2. The computer code developed in this study is successfully applied for solving the non-gray gas radiation within a 3-D rectangular
enclosure and the gray gas radiation within an irregular 3-D enclosure by showing fairly good agreements with the existing
results. In this paper the radiative transfer within an irregular 3-D enclosure filled with non-isothermal non-gray gases
with uniform mixtures of CO2, H2O and N2 is studied to demonstrate the applicability of the modified sum of gray gases model for irregular systems and to examine
the effect of the concentrations of CO2 and H2O on the radiative transfer within modern combustors. Results show that the wall heat fluxes and the radiative heat source
terms are increased as the concentrations of CO2 and H2O are increased. Results also show that the radiative fluxes caused by the mixture gases with high concentrations CO2 and H2O which can be observed in oxy-fuel combustion systems can reach up to nearly twice of those found in ordinary air-fuel combustion
systems. 相似文献