全文获取类型
收费全文 | 5684篇 |
免费 | 157篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 81篇 |
综合类 | 5篇 |
化学工业 | 1109篇 |
金属工艺 | 115篇 |
机械仪表 | 75篇 |
建筑科学 | 316篇 |
矿业工程 | 7篇 |
能源动力 | 163篇 |
轻工业 | 381篇 |
水利工程 | 44篇 |
石油天然气 | 113篇 |
武器工业 | 1篇 |
无线电 | 384篇 |
一般工业技术 | 872篇 |
冶金工业 | 1392篇 |
原子能技术 | 50篇 |
自动化技术 | 744篇 |
出版年
2021年 | 63篇 |
2020年 | 58篇 |
2019年 | 59篇 |
2018年 | 70篇 |
2017年 | 61篇 |
2016年 | 79篇 |
2015年 | 82篇 |
2014年 | 85篇 |
2013年 | 346篇 |
2012年 | 203篇 |
2011年 | 231篇 |
2010年 | 166篇 |
2009年 | 180篇 |
2008年 | 223篇 |
2007年 | 227篇 |
2006年 | 193篇 |
2005年 | 188篇 |
2004年 | 169篇 |
2003年 | 153篇 |
2002年 | 161篇 |
2001年 | 90篇 |
2000年 | 95篇 |
1999年 | 106篇 |
1998年 | 78篇 |
1997年 | 84篇 |
1996年 | 109篇 |
1995年 | 78篇 |
1994年 | 76篇 |
1993年 | 87篇 |
1992年 | 85篇 |
1991年 | 62篇 |
1990年 | 76篇 |
1989年 | 89篇 |
1988年 | 77篇 |
1987年 | 90篇 |
1986年 | 80篇 |
1985年 | 102篇 |
1984年 | 111篇 |
1983年 | 81篇 |
1982年 | 74篇 |
1981年 | 85篇 |
1980年 | 62篇 |
1979年 | 96篇 |
1978年 | 68篇 |
1977年 | 75篇 |
1976年 | 55篇 |
1975年 | 65篇 |
1974年 | 58篇 |
1973年 | 74篇 |
1972年 | 53篇 |
排序方式: 共有5852条查询结果,搜索用时 15 毫秒
11.
12.
Joel P. Martin J. Edward Swan II Robert J. Moorhead II Zhanping Liu Shangshu Cai 《Computer Graphics Forum》2008,27(3):991-998
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields. 相似文献
13.
Somsak Vanit-Anunchai Jonathan Billington Guy Edward Gallasch 《International Journal on Software Tools for Technology Transfer (STTT)》2008,10(1):29-56
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration
method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces
the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise
but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially
relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard,
the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we
introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the
peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP
to be analysed for larger parameter values.
Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree
University of Technology.
Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927). 相似文献
14.
Edward C. Malthouse 《Data mining and knowledge discovery》2007,15(3):383-402
This paper discusses a new application of data mining, quantifying the importance of responding to trigger events with reactive
contacts. Trigger events happen during a customer’s lifecycle and indicate some change in the relationship with the company.
If detected early, the company can respond to the problem and retain the customer; otherwise the customer may switch to another
company. It is usually easy to identify many potential trigger events. What is needed is a way of prioritizing which events
demand interventions. We conceptualize the trigger event problem and show how survival analysis can be used to quantify the
importance of addressing various trigger events. The method is illustrated on four real data sets from different industries
and countries. 相似文献
15.
The accumulation of two independent, broadly applicable formulations for determining the boundary to manipulator workspaces, presented elsewhere, are compared in this paper. Insights gained from one method are used to explain behavior exhibited in the other. Results are also compared and validated. A numerical formulation based on continuation methods is used to map curves that are on the boundary of a manipulator workspace. Analytical criteria based on row rank deficiency criteria of the manipulator's analytical Jacobian are used to map a family of one-dimensional solution curves on the boundary. The other formulation, based on a similar rank-deficiency criteria, yields analytic boundaries parametrized in terms of surface patches on the boundary. Results concerning the applicability of the numerical method to open- and closed-loop systems are compared with those limited to the open-loop for the analytical method. Conclusions regarding the behavior of the manipulator on geometric entities characterized by singular curves, higher-order bifurcation points, and surfaces inside the workspace are drawn. Applicability of both methods and their limitations are also addressed. 相似文献
16.
Myers Jerome L.; O'Brien Edward J.; Albrecht Jason E.; Mason Robert A. 《Canadian Metallurgical Quarterly》1994,20(4):876
Previous research demonstrated a contradiction effect: Although text currently being processed was locally coherent, readers were aware of inconsistencies between a protagonist's actions and characteristics of the protagonists that were described earlier in the text and subsequently backgrounded. In the present experiments, not only the critical characteristics but also the protagonist were backgrounded. When the protagonist was reintroduced into the narrative in the context of carrying out an inconsistent action, the contradiction effect again occurred. In Exps 1–3, we examined the effects of several variables on the onset of the effect. In Exp 4, we presented probes at various points in the passage with results that supported the conclusion that the critical characteristics had been backgrounded before the sentence that contradicted them. Results are discussed in terms of several recent models in which currently active representational elements serve as retrieval cues for other inactive, but highly related, elements. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
18.
A national survey of school psychologists' acceptability of psychological assessment techniques in the area of externalizing problem behaviors was examined. School psychologists' ratings of 2 procedures, Behavioral Assessment (BA) and Traditional Assessment (TA), were compared using an analog case study methodology. Using a random sample of 500 National Association of School Psychologists members from the 1991–1992 membership directory, 339 Ss completed the Assessment Rating Profile after reading a hypothetical case summary describing a student with suspected externalizing problem behaviors. Results indicated statistically significant differences between assessment methods and ratings of acceptability. BA procedures were found to be more acceptable than TA procedures. Implications related to the acceptability of psychological assessment techniques, as well as implications for school psychology practitioners are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
Yuansheng Jiang Yihan Shao Edward C. Kirby 《Fullerenes, Nanotubes and Carbon Nanostructures》1994,2(4):481-497
An algorithm to generate the molecular graphs of the trivalent clusters is presented. All the polyhedral trivalent cages with 4-16 vertices are enumerated, with particular attention being given to their symmetry, spectra and stability. The relative stability of isomers is not decided solely by their symmetry. A new kind of spectral phenomenon is reported. This is the occurrence of graphs having the same HOMO-LUMO gap, the same E and the same even-order moments. We refer to it as 'pseudo-isospectrality'. 相似文献
20.
N. M. Agh-Atabay W. Edward Lindsell Peter N. Preston Peter J. Tomb 《Polymer International》1993,31(4):367-374
Symmetrically substituted 1,3-diynes containing hydroxyalkyl ( 1a-d ), bromoalkyl ( 1e-h ) (diphenylphosphinyl) ( 1i-k ) and carboxyalkyl ( 2a-d ) substituents have been prepared and characterised; the phosphine derivative ( 1k ) has been converted with alkyl iodides ( RI ; R = Me, Et) into bis(phosphonium) salts ( 1l and m ). During preparation of the diynedioic acid. ( 2a ), the non-centrosymmetrical diyne, HO2CCH2C?C—C?C(CH2)2OH ( 3 ), was also isolated. 60Co γ-Irradiation of diacetylene monomers ( 2a – d ) and 10,12-tricosadiyn-1-oic acid gave the corresponding polydiacetylene derivatives ( 4a – d and 5 ), respectively. Rubidium salts of ( 4c ) and ( 4d ), a barium salt of ( 4c ), and a potassium salt of ( 5 ) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers ( 4 ) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed. 相似文献