全文获取类型
收费全文 | 64593篇 |
免费 | 2378篇 |
国内免费 | 523篇 |
专业分类
电工技术 | 452篇 |
综合类 | 193篇 |
化学工业 | 18572篇 |
金属工艺 | 7417篇 |
机械仪表 | 1285篇 |
建筑科学 | 712篇 |
矿业工程 | 555篇 |
能源动力 | 6614篇 |
轻工业 | 917篇 |
水利工程 | 117篇 |
石油天然气 | 238篇 |
武器工业 | 19篇 |
无线电 | 4988篇 |
一般工业技术 | 17784篇 |
冶金工业 | 4387篇 |
原子能技术 | 840篇 |
自动化技术 | 2404篇 |
出版年
2024年 | 86篇 |
2023年 | 2568篇 |
2022年 | 1309篇 |
2021年 | 1473篇 |
2020年 | 2985篇 |
2019年 | 2451篇 |
2018年 | 1564篇 |
2017年 | 3197篇 |
2016年 | 3173篇 |
2015年 | 3286篇 |
2014年 | 4313篇 |
2013年 | 3696篇 |
2012年 | 2941篇 |
2011年 | 2781篇 |
2010年 | 2637篇 |
2009年 | 2895篇 |
2008年 | 1545篇 |
2007年 | 2549篇 |
2006年 | 2430篇 |
2005年 | 1475篇 |
2004年 | 1138篇 |
2003年 | 1420篇 |
2002年 | 1560篇 |
2001年 | 1479篇 |
2000年 | 1089篇 |
1999年 | 1310篇 |
1998年 | 633篇 |
1997年 | 395篇 |
1996年 | 535篇 |
1995年 | 592篇 |
1994年 | 507篇 |
1993年 | 440篇 |
1992年 | 448篇 |
1991年 | 437篇 |
1990年 | 427篇 |
1989年 | 375篇 |
1988年 | 562篇 |
1987年 | 1034篇 |
1986年 | 1035篇 |
1985年 | 420篇 |
1984年 | 312篇 |
1983年 | 202篇 |
1982年 | 225篇 |
1981年 | 247篇 |
1980年 | 174篇 |
1979年 | 221篇 |
1978年 | 194篇 |
1977年 | 124篇 |
1976年 | 188篇 |
1975年 | 77篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
21.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
22.
23.
《International Journal of Machine Tools and Manufacture》2007,47(3-4):462-470
In literature, five different sets of work material constants used in the Johnson–Cook's (J–C) constitutive equation are implemented in a numerical model to describe the behaviour of AISI 316L steel. The aim of this research is to study the effects of five different sets of material constants of the J–C constitutive equation in finite-element modelling of orthogonal cutting of AISI 316L on the experimental and predicted cutting forces, chip morphology, temperature distributions and residual stresses. Several experimental equipments were used to estimate the experimental results, such as piezoelectric dynamometer for cutting forces measurements, thermal imaging system for temperature measurements and X-ray diffraction technique for residual stresses determination on the machined surfaces; while an elastic–viscoplastic FEM formulation was implemented to predict the local and global variables involved in this research. It has been observed that all the considered process output and, in particular the residual stresses are very sensitive to the J–C's material constants. 相似文献
24.
Cyclic oxidation response of multiphase niobium-based alloys 总被引:4,自引:0,他引:4
Kwai S. Chan 《Metallurgical and Materials Transactions A》2004,35(2):589-597
Cyclic oxidation tests were performed on multiphase Nb-based alloys containing silicide, Laves, and Nb solid solution phases.
In particular, the oxidation resistance of six alloys with various compositions (Nb, Ti, Hf, Cr, Ge, and Si) and microstructures
was characterized by thermal cycling from ambient temperature to a peak temperature that ranges from 900 °C to 1400 °C. Weight
change data were obtained and the corresponding spalled oxides were collected and identified by X-ray diffraction. The results
indicated that Nb-based alloys formed a mixture of CrNbO4, Nb2O5, and Nb2O5 · TiO2, with possibly small amounts of SiO2 or GeO2. The oxidation resistance was improved when CrNbO4 formed instead of Nb2O5 and Nb2O5 · TiO2. These results were used to assess the influence of microstructure and composition on the oxidation resistance of multiphase
Nb-based alloys. 相似文献
25.
《Cement and Concrete Composites》2007,29(7):527-532
In internal curing, pre-wetted lightweight aggregates (LWA) serve as internal reservoirs to supply the extra water needed by the cementitious and pozzolanic components of the concrete during their hydration processes. Due to their porous nature and reasonably high absorption capacity, the LWA can also be filled with other materials, such as phase change materials (PCMs). In this paper, three potential applications of PCM-filled LWA in concrete technology are presented. In addition to the previously explored application of increasing the energy storage capacity of concrete in residential and commercial construction by using a PCM with a transition temperature near room temperature, applications for higher and lower temperature PCMs also exist. In the former case, a PCM can be used to reduce the temperature rise (and subsequent rate of temperature decrease) of a large concrete section during (semi)adiabatic curing, to minimize thermal cracking, etc. In the latter case, a PCM can perhaps reduce the number or intensity of freeze/thaw cycles experienced by a bridge deck or other concrete exposed to a winter environment. In this paper, these latter two applications are preliminarily explored from both experimental and modeling viewpoints. 相似文献
26.
27.
《Computers & Geosciences》2006,32(7):912-926
This paper describes the development of highly accurate adaptive discontinuous Galerkin schemes for the solution of the equations arising from a thin layer type model of debris flows. Such flows have wide applicability in the analysis of avalanches induced by many natural calamities, e.g. volcanoes, earthquakes, etc. These schemes are coupled with special parallel solution methodologies to produce a simulation tool capable of very high-order numerical accuracy. The methodology successfully replicates cold rock avalanches at Mount Rainier, Washington and hot volcanic particulate flows at Colima Volcano, Mexico. 相似文献
28.
《Sensors and actuators. B, Chemical》2006,113(1):106-111
A stable film made from hydroxyethylcellulose (HEC) on pyrolytic graphite (PG) electrode was employed for incorporating hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP), and the electrochemical characteristics of the proteins were studied correspondingly. Experimental results revealed that HEC film could greatly accelerate electron transfer between the proteins and electrode, and the proteins showed a thin layer electrochemical behavior in the film. Moreover, all the proteins in the film exhibited good catalytic activity towards the reduction of hydrogen peroxide (H2O2) in the low H2O2 concentration range. In the high concentration range, H2O2 would exhibit toxicity effect on the proteins. The electrochemical properties and electrocatalytic abilities of the three heme proteins in HEC film have been compared, and the optimal conditions for H2O2 biosensor fabrication have been obtained. 相似文献
29.
P. C. Campbell E. B. Hawbolt J. K. Brimacombe 《Metallurgical and Materials Transactions A》1991,22(11):2769-2778
The goal of this study was to develop a mathematical model which incorporates heat flow, phase transformation kinetics, and
property-structure-composition relationships to predict the mechanical properties of steel rod being control cooled under
industrial conditions. Thus, the principles of microstructural engineering have been brought to bear on this interdisciplinary
problem by combining computer modeling with laboratory measurements of heat flow, austenite decomposition kinetics, microstructure
and mechanical properties, and industrial trials to determine heat transfer and obtain rod samples under known conditions.
Owing to the length and diversity of the study, it is reported in three parts,[8191]the first of which is concerned with the heat flow measurements. A relatively simple and reliable technique, involving a preheated
steel rod instrumented with a thermocouple secured at its centerline, has been devised to determine the cooling rate in different
regions of the moving bed of rod loops on an operating Stelmor line. The measured thermal response of the rod has been analyzed
by two transient conduction models (lumped and distributed parameter, respectively) to yield overall heat-transfer coefficients
for radiation and convection. The adequacy of the technique has been checked by cooling instrumented rods under well-defined,
air crossflow conditions in the laboratory and comparing measured heat-transfer coefficients to values predicted from well-established
equations. The industrial thermal measurements have permitted the characterization of a coefficient to account for radiative
interaction among adjacent rod loops near the edge and at the center of the bed.
Formerly Graduate Student, The University of British Columbia. 相似文献
30.
Journal of Materials Science Letters - 相似文献