全文获取类型
收费全文 | 2254篇 |
免费 | 19篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 22篇 |
综合类 | 2篇 |
化学工业 | 226篇 |
金属工艺 | 14篇 |
机械仪表 | 16篇 |
建筑科学 | 49篇 |
矿业工程 | 1篇 |
能源动力 | 21篇 |
轻工业 | 130篇 |
水利工程 | 6篇 |
石油天然气 | 41篇 |
武器工业 | 1篇 |
无线电 | 96篇 |
一般工业技术 | 241篇 |
冶金工业 | 1303篇 |
原子能技术 | 12篇 |
自动化技术 | 100篇 |
出版年
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2014年 | 12篇 |
2013年 | 38篇 |
2012年 | 29篇 |
2011年 | 66篇 |
2010年 | 38篇 |
2009年 | 33篇 |
2008年 | 45篇 |
2007年 | 36篇 |
2006年 | 35篇 |
2005年 | 39篇 |
2004年 | 34篇 |
2003年 | 51篇 |
2002年 | 47篇 |
2001年 | 32篇 |
2000年 | 22篇 |
1999年 | 59篇 |
1998年 | 369篇 |
1997年 | 213篇 |
1996年 | 169篇 |
1995年 | 113篇 |
1994年 | 79篇 |
1993年 | 88篇 |
1992年 | 35篇 |
1991年 | 42篇 |
1990年 | 36篇 |
1989年 | 38篇 |
1988年 | 25篇 |
1987年 | 23篇 |
1986年 | 26篇 |
1985年 | 34篇 |
1984年 | 17篇 |
1983年 | 21篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 42篇 |
1976年 | 79篇 |
1975年 | 11篇 |
1974年 | 10篇 |
1973年 | 13篇 |
1972年 | 6篇 |
1971年 | 7篇 |
排序方式: 共有2281条查询结果,搜索用时 15 毫秒
71.
C. Ibarra-Ramírez M. E. Villafuerte-Castrejón A. R. West 《Journal of Materials Science》1985,20(3):812-816
The transformation Li3PO4 shows characteristics of both continuous and martensitic transformations. Below 340° C, no detectable transformation occurs; between 340 and 410° C, the transformation goes only partially to completion; above 410° C the transformation rapidly goes to completion. At any temperature in the range 340 to 410° C, transformation proceeds rapidly in the initial stages to attain a certain degree of transformation. With prolonged isothermal heating or grinding of the samples, further transformation does not occur. The reverse transformation could not be effected under normal, dry conditions. 相似文献
72.
Over a wide range of frequencies, the a.c. conductivity of ionic materials shows two regions of frequency-dependent conductivity. These are each characterized by a term K
p
1–n
n where K, n are constants,
p is a fundamental frequency identified with the hopping rate and is the measuring frequency. This behaviour is an example of Jonscher's Law of Dielectric Response for ionic conductors. In many cases, the region of low-frequency dispersion approximates to a frequency-independent plateau which may be taken as the d.c. conductivity. In others, a significant low-frequency dispersion is present and cannot be ignored in determining the effective d.c. conductivity. A method for the extraction of d.c. conductivities, hopping rates and for estimating carrier concentration effects is described. Data for three different types of material, single-crystal LiGaO2, -alumina and Na/Ag -alumina are used to illustrate the method. 相似文献
73.
Residuals of facial paralysis consist of a great variety of cosmetic and functional anomalies which differ in quality and/or quantity. An internationally standardized evaluation of such defects is mandatory for the assessment of the results of different therapeutic procedures. In the present study, a system has been developed to record the results of facial paralysis following therapy. Such a system does not require specialized training, instrumentation or require significant time for completion. A clearly-defined "Yes-No" evaluation criteria is established which creates a high interscorer reliability. The usefulness of this scoring system was tested by three examiners on 42 patients following facial nerve surgery, with an obtained interscorer reliability of 93%. 相似文献
74.
As the nuclear power plants within the UK age, there is an increased requirement for condition monitoring to ensure that the plants are still be able to operate safely. This paper describes the novel application of Intelligent Systems (IS) techniques to provide decision support to the condition monitoring of Nuclear Power Plant (NPP) reactor cores within the UK. The resulting system, BETA (British Energy Trace Analysis) is deployed within the UK’s nuclear operator and provides automated decision support for the analysis of refuelling data, a lead indicator of the health of AGR (Advanced Gas-cooled Reactor) nuclear power plant cores. The key contribution of this work is the improvement of existing manual, labour-intensive analysis through the application of IS techniques to provide decision support to NPP reactor core condition monitoring. This enables an existing source of condition monitoring data to be analysed in a rapid and repeatable manner, providing additional information relating to core health on a more regular basis than routine inspection data allows. The application of IS techniques addresses two issues with the existing manual interpretation of the data, namely the limited availability of expertise and the variability of assessment between different experts. Decision support is provided by four applications of intelligent systems techniques. Two instances of a rule-based expert system are deployed, the first to automatically identify key features within the refuelling data and the second to classify specific types of anomaly. Clustering techniques are applied to support the definition of benchmark behaviour, which is used to detect the presence of anomalies within the refuelling data. Finally data mining techniques are used to track the evolution of the normal benchmark behaviour over time. This results in a system that not only provides support for analysing new refuelling events but also provides the platform to allow future events to be analysed. The BETA system has been deployed within the nuclear operator in the UK and is used at both the engineering offices and on station to support the analysis of refuelling events from two AGR stations, with a view to expanding it to the rest of the fleet in the near future. 相似文献
75.
Martensitic transformations in Ti-Mo alloys 总被引:5,自引:0,他引:5
A detailed investigation has been made of the structure of alloys of the Ti-Mo system containing up to 10wt% Mo, water-quenched from the-phase region. With increase in molybdenum content, the martensite structure changes from hexagonal () to orthorhombic () at 4 wt% Mo, and at 10 wt% Mo, the structure is completely retained . For alloy compositions <4 wt% Mo, there is a diffusional component in the transformation of the -phase at the quench rates employed. There is a transition, with increase in molybdenum content, in morphology (from massive to acicular) and in substructure (from dislocations to twins). However, the transitions in crystallography, morphology and sub-structure are not directly related to one another except for an abrupt loss of dislocation substructure at the/ transition. The to crystallographic transition has the characteristics of a second order transformation, and evidence has been obtained of the existence of a spinodal within the metastable orthorhombic system. The orthorhombic martensites of Ti-6 and 8 wt% Mo decompose during quenching producing a fine modulated structure within the martensite plates, consistent with a proposed spinodal mode of decomposition. 相似文献
76.
There is an accumulation of the glycolytic enzyme enolase and of cholesteryl esters in macrophages that have been converted
into “foam” cells. In this study, we questioned whether enolase could be involved in this accumulation of cholesteryl esters
by inhibiting the activity of neutral cholesteryl ester hydrolases. Enolase from both yeast and rabbit muscle were incubated
with three different cholesteryl ester hydrolases and were shown to inhibit the hydrolysis of cholesteryl esters. Inhibition
was dependent on the concentration of enolase and appeared to occur through binding of the enolase to the cholesteryl ester.
Nevertheless, the yeast and rabbit muscle enolases differed in their efficiency of inhibition and in their mechanism of action.
Purification of commercial enolase preparations by gel-filtration yielded single proteins with the same inhibitory activities
as the originals, indicating that the inhibition was not due to the presence of an impurity. Partially purified αα-and γγ-isoforms
of the enzyme from rat brain also appear to have inhibitory effects on cholesteryl ester hydrolysis. Negative control of the
hydrolytic phase of the cholesterol/cholesteryl ester cycle may be a secondary function of enolases which correlates with
the accumulation of cholesteryl esters in a number of neuro-degenerative and demyelinating diseases. 相似文献
77.
A young female with ulcerative colitis associated with positive direct and indirect Coombs reaction and severe autoimmune hemolytic anemia is reported. Cortisone was beneficial and total colectomy was promptly followed by subsidence of the hematologic defects. Review of the literature suggests that this complication of ulcerative colitis is uncommon. It basis is unclear. It seems to be expressed through the presence of a "warm" auto-antibody. Colectomy should be strongly considered when severe hemolysis is present but not when the Coombs test is positive alone without significant hemolysis. 相似文献
78.
JH West 《Canadian Metallurgical Quarterly》1976,69(6):741-746
Forty-two (37 evaluable) unselected women with advanced breast carcinoma were treated with a modified "Cooper regimen" in a community setting. After 12 weeks of induction therapy, the patients were evaluated for response and toxicity. The 74% overall response rate (78% in the evaluable group) compares favorably with that of other series. The median duration of remission was 13.7 months. The median survival was 17 months for the evaluable patients and 14 months for the entire group. Twenty-two percent of the patients required hospitalization during the induction phase, and 35% were treated exclusively as outpatients during all phases of therapy. There was only one drug-related death. It is concluded that a complex chemotherapeutic regimen can be managed adequately by physicians experienced in chemotherapy in a community setting with results comparable to those from cancer centers. 相似文献
79.
Interval Set Clustering of Web Users with Rough K-Means 总被引:1,自引:0,他引:1
Data collection and analysis in web mining faces certain unique challenges. Due to a variety of reasons inherent in web browsing and web logging, the likelihood of bad or incomplete data is higher than conventional applications. The analytical techniques in web mining need to accommodate such data. Fuzzy and rough sets provide the ability to deal with incomplete and approximate information. Fuzzy set theory has been shown to be useful in three important aspects of web and data mining, namely clustering, association, and sequential analysis. There is increasing interest in research on clustering based on rough set theory. Clustering is an important part of web mining that involves finding natural groupings of web resources or web users. Researchers have pointed out some important differences between clustering in conventional applications and clustering in web mining. For example, the clusters and associations in web mining do not necessarily have crisp boundaries. As a result, researchers have studied the possibility of using fuzzy sets in web mining clustering applications. Recent attempts have used genetic algorithms based on rough set theory for clustering. However, the genetic algorithms based clustering may not be able to handle the large amount of data typical in a web mining application. This paper proposes a variation of the K-means clustering algorithm based on properties of rough sets. The proposed algorithm represents clusters as interval or rough sets. The paper also describes the design of an experiment including data collection and the clustering process. The experiment is used to create interval set representations of clusters of web visitors. 相似文献
80.
分析了地质因素和工程因素对矿井瓦斯涌出量的影响,提出了瓦斯涌出量非线性回归预测方法.根据矿井实际情况确定了需要分析的影响因素,通过STATISTICA统计软件中Nonlinear Estimation和FixedNonlinear regression模块建立和检验了瓦斯涌出量非线性回归数学模型,得出非线性回归数学模型瓦斯涌出量与主要影响因素具有较高的相关性.应用.NET提供的可视化界面及C#程序语言开发了瓦斯涌出量非线性预测软件,通过对成庄矿3390采面预测效果验证,表明非线性回归预测方法对矿井瓦斯涌出量预测是可行的. 相似文献