全文获取类型
收费全文 | 66630篇 |
免费 | 3451篇 |
国内免费 | 548篇 |
专业分类
电工技术 | 1370篇 |
综合类 | 534篇 |
化学工业 | 12627篇 |
金属工艺 | 2572篇 |
机械仪表 | 3524篇 |
建筑科学 | 1916篇 |
矿业工程 | 272篇 |
能源动力 | 2499篇 |
轻工业 | 4677篇 |
水利工程 | 375篇 |
石油天然气 | 531篇 |
武器工业 | 46篇 |
无线电 | 11555篇 |
一般工业技术 | 12690篇 |
冶金工业 | 6545篇 |
原子能技术 | 721篇 |
自动化技术 | 8175篇 |
出版年
2023年 | 695篇 |
2022年 | 1111篇 |
2021年 | 1778篇 |
2020年 | 1263篇 |
2019年 | 1246篇 |
2018年 | 1627篇 |
2017年 | 1632篇 |
2016年 | 1950篇 |
2015年 | 1627篇 |
2014年 | 2478篇 |
2013年 | 4117篇 |
2012年 | 3775篇 |
2011年 | 4581篇 |
2010年 | 3572篇 |
2009年 | 3738篇 |
2008年 | 3513篇 |
2007年 | 2959篇 |
2006年 | 2745篇 |
2005年 | 2289篇 |
2004年 | 2155篇 |
2003年 | 2020篇 |
2002年 | 1940篇 |
2001年 | 1529篇 |
2000年 | 1428篇 |
1999年 | 1415篇 |
1998年 | 2476篇 |
1997年 | 1653篇 |
1996年 | 1407篇 |
1995年 | 1117篇 |
1994年 | 856篇 |
1993年 | 786篇 |
1992年 | 559篇 |
1991年 | 549篇 |
1990年 | 458篇 |
1989年 | 449篇 |
1988年 | 354篇 |
1987年 | 302篇 |
1986年 | 279篇 |
1985年 | 252篇 |
1984年 | 209篇 |
1983年 | 163篇 |
1982年 | 161篇 |
1981年 | 140篇 |
1980年 | 144篇 |
1979年 | 115篇 |
1978年 | 101篇 |
1977年 | 128篇 |
1976年 | 171篇 |
1975年 | 91篇 |
1974年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
Michael J. McNallan Ph.D. Pei Pei Hsu Ph.D. Soo Young Lee Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1993,45(12):22-25
Nonoxide silicon-based ceramics owe their oxidation resistance to the formation of a thin silica film that separates the ceramic from oxidizing environments. This silica film can be fluxed by alkali oxides to form low-melting alkali silicate corrosion products that do not provide protection. Alkali chlorides and other halides have sufficiently high vapor pressures that silica fluxing can occur without the formation of a condensed halide salt. The rates of oxidation of Si, SiC, and Si3N4 are influenced by the composition of gas mixtures containing these species. 相似文献
992.
COUPLED SIMULATION OF 3D ELECTRO-MAGNETO-FLOW FIELD IN HALL-HEROULT CELLS USING FINITE ELEMENT METHOD 总被引:6,自引:0,他引:6
J. Li W. Liu Y.Q. Lai Q.Y. Li Y.X. Liu 《金属学报(英文版)》2006,19(2):105-116
Two full 3D steady mathematical models are developed by finite element method (FEM) to calcalate coupled physics fields. the electro-magnetic model is built and solved first and so is the fluid motion model with the acquired electromagnetic force as source body forces in Navier-Stokes equations. Effects caused by the ferromagnetic shell, busbar system around, and open boundary problem as well as inside induced current were considered in terms of the magnetic field. Furthermore, a new modeling method is found to set up solid models and then mesh them entirely with so-called structuralized grids, namely hex-mesh. Examples of 75kA prebaked cell with two kinds of busbar arrangements are presented. Results agree with those disclosed in the literature and confirm that the coupled simulation is valid. It is also concluded that the usage of these models facilitates the consistent analysis of the electric field to magnetic field and then flow motion to the greater extent, local distributions of current density and magnetic flux density are very much dependent on the cell structure, the steel shell is a shield to reduce the magnetic field and flow pattern is two dimensional in the main body of the metal pad. 相似文献
993.
The Cd−Zn system has been thermodynamically reassessed with the CALPHAD method by combining more recent experimental data,
in particular the activities of zinc in the liquid phase. A good agreement is obtained between the calculated and experimental
thermodynamic parameters as well asphase boundaries. 相似文献
994.
研究了等离子喷涂法制备ZrO2Ti系功能梯度涂层。结果表明,采用等离子喷涂工艺制备功能梯度涂层是可行的,涂层与基体除以机械咬合方式结合外,还存在着少量冶金化学反应结合,添加Ni/Al和SiO2有助于提高涂层的结合强度 相似文献
995.
Jong-Young?Park Young-Soo?No Byung-Jun?Park Hyun-Woo?Lee Ji-Won?Choi Jin-Sang?Kim Y.?Ermakov Seok-Jin?Yoon Young-Jei?Oh Won-Kook?ChoiEmail author 《Metals and Materials International》2004,10(4):351-355
A low energy N2 ? ion beam impinged on a α-Al2O3(0001) single crystal surface in the range of fluence 5×1015/cm2?1×1018/cm2 at room temperature. After ion bombardment, chemical bonding on the modified sapphire surface was investigated by x-ray photoelectron spectroscopy. Below a fluence of 1×1015/cm2, only a non-bonded N1s peak at the binding energy 398.7 eV was found, but further irradiation up to 2×1017/cm2 induced Al?O?N bonding at around 403 eV. The occurrence of Al?N bonding was identified at ion fluence higher than 5×1017/cm2 at 396.6 eV. II–VI ZnO thin films were grown on an untreated/ion-beam-induced sapphire surface by pulsed laser deposition (PLD) for the investigation of the modified-substrate effect on photoluminescence. The ZnO films grown on modified sapphire containing Al?O?N bonding only, and both Al?O?N and Al?N bonding showed a significant reduction of the peak related to deep-level defects in photoluminescence. These results are explained in terms of the formation of Al?N?O and Al?O?N layers and relaxation of the interfacial strain between Al2O3 and ZnO. 相似文献
996.
In-Gyu Park Chang-Soon Lee Seong-Sik Hwang Hong-Pyo Kim Joung-Soo Kim 《Metals and Materials International》2005,11(5):401-409
In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made
alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C,
for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according
to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations,
but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking
was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In
30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount
of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has
the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic
SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature.
Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance. 相似文献
997.
Jung Lee 《Behaviour & Information Technology》2015,34(1):57-68
This study challenges the conventional assumption that online customers with high purchase intention routinely move to the purchase stage. To this end, the process of how online customers form purchase intention and behaviour is examined. On the basis of product value distribution (PVD), we propose that the hypothetically expected product value (i.e. PVD average) determines purchase intention, whereas the actual probability of attaining the expected product value (i.e. PVD variance) moderates purchase behaviour. This proposal indicates that the expected product value has significance only when repeated purchase is assumed given that most consumers do not repeatedly purchase the same product in reality. Thus, the actual probability of attaining the expected product value more critically affects customer behaviour than does its expected value. The effectiveness of the research model is verified by conducting a survey on 300 online mall shoppers in Korea. The results confirm model effectiveness. 相似文献
998.
Anshu Dubey Klaus Weide Dongwook Lee John Bachan Christopher Daley Samuel Olofin Noel Taylor Paul M. Rich Lynn B. Reid 《Software》2015,45(2):233-244
When developing a complex, multi‐authored code, daily testing on multiple platforms and under a variety of conditions is essential. It is therefore necessary to have a regression test suite that is easily administered and configured, as well as a way to easily view and interpret the test suite results. We describe the methodology for verification of FLASH, a highly capable multiphysics scientific application code with a wide user base. The methodology uses a combination of unit and regression tests and an in‐house testing software that is optimized for operation under limited resources. Although our practical implementations do not always comply with theoretical regression‐testing research, our methodology provides a comprehensive verification of a large scientific code under resource constraints.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
1000.
Programmers build large‐scale systems with multiple languages to leverage legacy code and languages best suited to their problems. For instance, the same program may use Java for ease of programming and C to interface with the operating system. These programs pose significant debugging challenges, because programmers need to understand and control code across languages, which often execute in different environments. Unfortunately, traditional multilingual debuggers require a single execution environment. This paper presents a novel composition approach to building portable mixed‐environment debuggers, in which an intermediate agent interposes on language transitions, controlling and reusing single‐environment debuggers. We implement debugger composition in Blink, a debugger for Java, C, and the Jeannie programming language. We show that Blink is (i) simple: it requires modest amounts of new code; (ii) portable: it supports multiple Java virtual machines, C compilers, operating systems, and component debuggers; and (iii) powerful: composition eases debugging, while supporting new mixed‐language expression evaluation and Java native interface bug diagnostics. To demonstrate the generality of interposition, we build prototypes and demonstrate debugger language transitions with C for five of six other languages (Caml, Common Lisp, C#, Perl 5, Python, and Ruby) without modifications to their debuggers. Using real‐world case studies, we show that diagnosing language interface errors require prior single‐environment debuggers to restart execution multiple times, whereas Blink directly diagnoses them with one execution. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献