全文获取类型
收费全文 | 5031篇 |
免费 | 163篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 51篇 |
综合类 | 1篇 |
化学工业 | 926篇 |
金属工艺 | 87篇 |
机械仪表 | 86篇 |
建筑科学 | 296篇 |
矿业工程 | 18篇 |
能源动力 | 132篇 |
轻工业 | 458篇 |
水利工程 | 43篇 |
石油天然气 | 38篇 |
武器工业 | 1篇 |
无线电 | 274篇 |
一般工业技术 | 853篇 |
冶金工业 | 992篇 |
原子能技术 | 20篇 |
自动化技术 | 929篇 |
出版年
2023年 | 32篇 |
2022年 | 40篇 |
2021年 | 83篇 |
2020年 | 74篇 |
2019年 | 63篇 |
2018年 | 91篇 |
2017年 | 72篇 |
2016年 | 122篇 |
2015年 | 88篇 |
2014年 | 160篇 |
2013年 | 347篇 |
2012年 | 241篇 |
2011年 | 320篇 |
2010年 | 222篇 |
2009年 | 192篇 |
2008年 | 255篇 |
2007年 | 232篇 |
2006年 | 189篇 |
2005年 | 191篇 |
2004年 | 138篇 |
2003年 | 129篇 |
2002年 | 130篇 |
2001年 | 80篇 |
2000年 | 72篇 |
1999年 | 79篇 |
1998年 | 100篇 |
1997年 | 107篇 |
1996年 | 73篇 |
1995年 | 73篇 |
1994年 | 53篇 |
1993年 | 68篇 |
1992年 | 77篇 |
1991年 | 44篇 |
1990年 | 50篇 |
1989年 | 55篇 |
1988年 | 49篇 |
1987年 | 48篇 |
1986年 | 56篇 |
1985年 | 70篇 |
1984年 | 57篇 |
1983年 | 68篇 |
1982年 | 48篇 |
1981年 | 35篇 |
1980年 | 45篇 |
1979年 | 61篇 |
1978年 | 45篇 |
1977年 | 45篇 |
1976年 | 37篇 |
1975年 | 37篇 |
1973年 | 25篇 |
排序方式: 共有5205条查询结果,搜索用时 15 毫秒
21.
22.
Philip Tipping 《International Journal of Pressure Vessels and Piping》1996,66(1-3):17-25
The susceptibility and tendency for nuclear power plant (NPP) components to undergo changes in their mechanical and physical properties in the course of the NPP lifetime is generally termed as “ageing”. The light water reactor (LWR) nuclear environment is not a begnign one; it is characterized not only by fast neutrons, which can degrade metallic structures, but also relatively high temperatures of coolant water (around 300°C) which may contain impurities (e.g. sulphate, chloride, peroxides) which can cause corrosion. The hydrodynamical conditions of the coolant in steam generators, for example, can cause thermal fatigue, erosion and corrosion; suspended particulate matter can accelerate erosion processes which can lead to wall thinning and lowering of safety margins. Ageing is, therefore, a very complex mixture of factors concerned with materials, temperatures, times of exposure to environments which vary with time and with respect to chemical composition and flow charactertistics.
The paper describes a few ageing phenomena which can be considered important due to their impact on nuclear safety issues; their influence on economic aspects (availability) of NPP is outlined. Mitigation measures for NPP component ageing problems are given together with recommendations for addressing such issues in NPP now and in the future. 相似文献
23.
Jennifer K. Edwards Adrian Thomas Benjamin E. Solsona Philip Landon Albert F. Carley Graham J. Hutchings 《Catalysis Today》2007,122(3-4):397-402
The direct synthesis of hydrogen peroxide from H2 and O2 using a range of supported Au–Pd alloy catalysts is compared for different supports using conditions previously identified as being optimal for hydrogen peroxide synthesis, i.e. low temperature (2 °C) using a water–methanol solvent mixture and short reaction time. Five supports are compared and contrasted, namely Al2O3, -Fe2O3, TiO2, SiO2 and carbon. For all catalysts the addition of Pd to the Au only catalyst increases the rate of hydrogen peroxide synthesis as well as the concentration of hydrogen peroxide formed. Of the materials evaluated, the carbon-supported Au–Pd alloy catalysts give the highest reactivity. The results show that the support can have an important influence on the synthesis of hydrogen peroxide from the direct reaction. The effect of the methanol–water solvent is studied in detail for the 2.5 wt% Au–2.5 wt% Pd/TiO2 catalyst and the ratio of methanol to water is found to have a major effect on the rate of hydrogen peroxide synthesis. The optimum mixture for this solvent system is 80 vol.% methanol with 20 vol.% water. However, the use of water alone is still effective albeit at a decreased rate. The effect of catalyst mass was therefore also investigated for the water and water–methanol solvents and the observed effect on the hydrogen peroxide productivity using water as a solvent is not considered to be due to mass transfer limitations. These results are of importance with respect to the industrial application of these Au–Pd catalysts. 相似文献
24.
25.
Philip John McKerrow 《Robotics and Autonomous Systems》1993,11(3-4):205-211
A ring of ultrasonic sensors mounted on a mobile robot is used to map a room. The sensors are modelled with an arc model: the object causing the reflection lies on an arc with radius equal to the range and arc angle equal to twice the beam angle. By fusing sensing with motion, a surface is displayed as a sequence of arcs. In this paper, the algorithm for obtaining outline segments from the arcs is presented. 相似文献
26.
27.
Philip G. Holland 《Flow Measurement and Instrumentation》2002,13(5-6):299-301
Standards cannot be set, specifications cannot be written uniformly and unambiguously, and methods cannot be described succinctly, without an agreed terminology. Producing a glossary is a painstaking process and the fundamental principles involved are described. Some difficulties and misunderstandings are identified. 相似文献
28.
Philip G. Spain 《国际强度与非线性控制杂志
》1991,1(1):43-45
》1991,1(1):43-45
Formulae, explicitly symmetric in the roots of the denominator, are derived for the best approximation to a rational function of degree 2 by an analytic function and by a function with at most one pole. 相似文献
29.
Murphy Philip N.; Bentall Richard P.; Ryley Lisa D.; Ralley Richard 《Canadian Metallurgical Quarterly》2003,17(2):167
Admission scores from a model comprising 3 motivation factors concerning the cessation of heroin use and a confidence scale concerning postdischarge abstinence were tested for their ability to predict postdischarge outcomes in patients beginning inpatient opiate detoxification. Statistically significant prediction of abstinence from heroin 30 days after discharge and the number of heroin-free days in the 3 months following admission was based on the confidence scale and a factor concerned with externally imposed constraints on continued heroin use. The single-scale confidence measure made the largest contribution to each prediction, indicating that such scales may be potentially useful outcome predictors for postdischarge abstinence. External constraints on heroin use may not provide a basis for success in this treatment modality. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
Longabaugh Richard; Wirtz Philip W.; Beattie Martha C.; Noel Nora; Stout Robert 《Canadian Metallurgical Quarterly》1995,63(2):296
Patients were randomly assigned to 1 of 3 treatments: brief broad-spectrum (BBS), extended relationship enhancement (ERE), or extended cognitive–behavioral (ECB). A hierarchical latent growth model was used to analyze the data of 188 patients (82%) followed for 18 months. ERE treatment was significantly more effective in increasing abstinence of patients entering treatment with a network unsupportive of abstinence or with a low level of investment in their network, whereas BBS treatment was more effective for patients with either (a) both a social network unsupportive of abstinence and a low level of network investment or (b) high investment in a network supportive of abstinence. ECB outcomes were neither as good as those matched nor as bad as those mismatched to the different exposures of relationship enhancement. This suggests that dose of relationship enhancement should be determined after assessing patient relationships. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献