全文获取类型
收费全文 | 8377篇 |
免费 | 241篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 88篇 |
综合类 | 13篇 |
化学工业 | 1760篇 |
金属工艺 | 136篇 |
机械仪表 | 112篇 |
建筑科学 | 484篇 |
矿业工程 | 47篇 |
能源动力 | 207篇 |
轻工业 | 807篇 |
水利工程 | 107篇 |
石油天然气 | 38篇 |
无线电 | 528篇 |
一般工业技术 | 1169篇 |
冶金工业 | 2118篇 |
原子能技术 | 95篇 |
自动化技术 | 919篇 |
出版年
2022年 | 82篇 |
2021年 | 121篇 |
2020年 | 98篇 |
2019年 | 100篇 |
2018年 | 107篇 |
2017年 | 109篇 |
2016年 | 126篇 |
2015年 | 112篇 |
2014年 | 164篇 |
2013年 | 435篇 |
2012年 | 285篇 |
2011年 | 355篇 |
2010年 | 280篇 |
2009年 | 306篇 |
2008年 | 366篇 |
2007年 | 350篇 |
2006年 | 307篇 |
2005年 | 261篇 |
2004年 | 233篇 |
2003年 | 238篇 |
2002年 | 212篇 |
2001年 | 147篇 |
2000年 | 143篇 |
1999年 | 144篇 |
1998年 | 122篇 |
1997年 | 119篇 |
1996年 | 115篇 |
1995年 | 140篇 |
1994年 | 132篇 |
1993年 | 123篇 |
1992年 | 134篇 |
1991年 | 91篇 |
1990年 | 109篇 |
1989年 | 122篇 |
1988年 | 116篇 |
1987年 | 113篇 |
1986年 | 117篇 |
1985年 | 146篇 |
1984年 | 135篇 |
1983年 | 118篇 |
1982年 | 130篇 |
1981年 | 126篇 |
1980年 | 89篇 |
1979年 | 123篇 |
1978年 | 120篇 |
1977年 | 103篇 |
1976年 | 87篇 |
1975年 | 84篇 |
1974年 | 90篇 |
1973年 | 99篇 |
排序方式: 共有8628条查询结果,搜索用时 15 毫秒
21.
Orthopedists being more engaged in surgery are often asked about problems concerning exercise science. This article will summarize the existing basic knowledge, very close to practice, and put down the leading steps of how to build up a (therapeutical) training programme. A lab block is recommended acting on a preventive as well as on a sportive medical base. 相似文献
22.
Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies. 相似文献
23.
What has become known as Community Operational Research has been around in the UK for many years. The election of Jonathan Rosenhead as President of the UK OR Society in 1986–87 was the catalyst for bringing together and expanding activities which had been carried out largely by individuals working in isolation on a voluntary basis. The following five years have seen the establishment of the Community OR Unit at Northern College, the Centre for Community OR at Hull University and the Community OR Network, which supports the activities of volunteer OR workers across the UK. This paper reviews the range and types of work which have been undertaken by various practitioners. An assessment of the success of community OR is made and a number of issues which have arisen are discussed. Finally, given the diverse nature of community OR, its practice and practitioners, there is some discussion about the future of the area. 相似文献
24.
Karen S. Servilla Antonios H. Tzamaloukas Charles Carter Glen H. Murata 《Hemodialysis international. International Symposium on Home Hemodialysis》2002,6(1):35-39
We developed a composite compliance index as the sum of the compliance scores for interdialytic weight gain (IDWG), pre‐dialysis serum potassium and phosphorus concentrations (each scored from zero to 3, with 3 indicating the poorest compliance), and skipping hemodialysis sessions (scored from zero to 9, with 9 indicating the poorest compliance). We used this composite score to prospectively evaluate compliance in 25 prevalent hemodialysis patients over a period of 1 year. We then followed these patients for another 3.5 years. The patients studied were divided into two groups: group A (poor compliance) consisted of 9 subjects with composite score ≥ 9 (13.2 ± 3.2); group B (better compliance) consisted of 16 subjects with composite score < 9 (4.7 ± 1.8). Age, duration of hemodialysis, and frequency of diabetes mellitus did not differ between the groups. Group A contained higher fractions of subjects with history of alcoholism (66.7% vs 12.5%, p = 0.010), other substance addiction (44.4% vs 0%, p = 0.010), and severe psychosocial problems (88.9% vs 18.8%, p = 0.002). Mean survival from the beginning of observation, estimated by actuarial life‐table survival analysis, was 1.19 years in group A and 2.60 years in group B (p = 0.0265). A composite compliance index incorporating domains indicating adherence to diet, medications, and dialysis schedule identified other behavioral problems in poorly compliant patients. Hemodialysis patients characterized by this composite index as poorly compliant had shortened survival. 相似文献
25.
Replicated W. K. Kirchner and M. D. Dunnette's (see record 1955-03161-001) study on attitudes toward older workers with 71 male and 5 female hourly employees (aged 18–61 yrs) and 22 male supervisors (aged 27–63 yrs) of a nonunion manufacturing plant. Ss completed a questionnaire that was nearly identical to the one administered in the Kirchner and Dunnette study. Results are similar to those obtained in the earlier study: Hourly workers held more positive attitudes toward older employees than did supervisors, and attitude score correlated strongly with the age of hourly workers but not with the age of supervisors. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
26.
Pezeshki A. Scharf L.L. Azimi-Sadjadi M.R. Yingbo Hua 《Signal Processing, IEEE Transactions on》2005,53(1):121-135
The problem of two-channel constrained least squares (CLS) filtering under various sets of constraints is considered, and a general set of solutions is derived. For each set of constraints, the solution is determined by a coupled (asymmetric) generalized eigenvalue problem. This eigenvalue problem establishes a connection between two-channel CLS filtering and transform methods for resolving channel measurements into canonical or half-canonical coordinates. Based on this connection, a unified framework for reduced-rank Wiener filtering is presented. Then, various representations of reduced-rank Wiener filters in canonical and half-canonical coordinates are introduced. An alternating power method is proposed to recursively compute the canonical coordinate and half-canonical coordinate mappings. A deflation process is introduced to extract the mappings associated with the dominant coordinates. The correctness of the alternating power method is demonstrated on a synthesized data set, and conclusions are drawn. 相似文献
27.
28.
Prediction of Undrained Sinkhole Collapse 总被引:2,自引:0,他引:2
Charles E. Augarde Andrei V. Lyamin Scott W. Sloan 《Canadian Metallurgical Quarterly》2003,129(3):197-205
Sinkholes are surface depressions or shafts resulting from the collapse of a submerged cavity in soil. The cavities that lead to sinkholes form as a result of underlying geology in limestone areas, or as a result of human activity such as mining or leakage from a sewer. The formation of sinkholes is often sudden and can lead to extensive damage and loss of life, especially in urban areas. Much of the literature on the subject of sinkhole formation is empirical in nature, often being associated with specific locations. This paper presents the results of a study, using numerical modeling, of the undrained stability of the submerged cavities that lead to sinkhole formation. Finite-element limit analysis techniques (using programs developed at the University of Newcastle) are used to obtain upper and lower bound values of a suitable load parameter, which bracket the exact solution. The results are compared to analytical solutions, both from literature and derived independently. 相似文献
29.
Richard F. D.; Bond Charles F. Jr.; Stokes-Zoota Juli J. 《Canadian Metallurgical Quarterly》2003,7(4):331
This article compiles results from a century of social psychological research, more than 25,000 studies of 8 million people. A large number of social psychological conclusions are listed alongside meta-analytic information about the magnitude and variability of the corresponding effects. References to 322 meta-analyses of social psychological phenomena are presented, as well as statistical effect-size summaries. Analyses reveal that social psychological effects typically yield a value of r equal to .21 and that, in the typical research literature, effects vary from study to study in ways that produce a standard deviation in r of .15. Uses, limitations, and implications of this large-scale compilation are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
Fellers Gloria; McInnis Charles; Cappelli Mario; Cragg Susan; Vaillancourt Raymond 《Canadian Metallurgical Quarterly》1987,19(1):108
The WAIS-R Information subtest was combined with 21 potential substitute Canadian content items and group-administered to 119 high school students ranging in age from 16 to 19 years. Seven acceptable substitute items were identified. Mean scores on the American items for the 16-17 and 18-19 age groups suggested that Canadians of these ages are not penalized by American content with respect to either Verbal or Full Scale IQ. Nevertheless, the research identified eight Information items, four easier and four more difficult than the standard WAIS-R implies. Similar results were noted in two previous studies of the WAIS-R, and indicate the extreme caution required for the clinical interpretation of intra test scatter. There is also evidence that item difficulty within the Information subtest may vary with the age of the subject. These results were considered indicative of the necessity for Canadian content Information items and the development of Canadian norms for an adapted WAIS-R Information subtest. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献