全文获取类型
收费全文 | 27322篇 |
免费 | 706篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 333篇 |
综合类 | 14篇 |
化学工业 | 6042篇 |
金属工艺 | 530篇 |
机械仪表 | 468篇 |
建筑科学 | 1181篇 |
矿业工程 | 333篇 |
能源动力 | 654篇 |
轻工业 | 1740篇 |
水利工程 | 227篇 |
石油天然气 | 245篇 |
无线电 | 1749篇 |
一般工业技术 | 4170篇 |
冶金工业 | 6355篇 |
原子能技术 | 270篇 |
自动化技术 | 3750篇 |
出版年
2022年 | 251篇 |
2021年 | 419篇 |
2020年 | 269篇 |
2019年 | 357篇 |
2018年 | 426篇 |
2017年 | 374篇 |
2016年 | 496篇 |
2015年 | 397篇 |
2014年 | 625篇 |
2013年 | 1673篇 |
2012年 | 950篇 |
2011年 | 1216篇 |
2010年 | 933篇 |
2009年 | 986篇 |
2008年 | 1165篇 |
2007年 | 1073篇 |
2006年 | 985篇 |
2005年 | 893篇 |
2004年 | 755篇 |
2003年 | 720篇 |
2002年 | 716篇 |
2001年 | 491篇 |
2000年 | 400篇 |
1999年 | 470篇 |
1998年 | 495篇 |
1997年 | 464篇 |
1996年 | 507篇 |
1995年 | 462篇 |
1994年 | 467篇 |
1993年 | 446篇 |
1992年 | 440篇 |
1991年 | 281篇 |
1990年 | 417篇 |
1989年 | 399篇 |
1988年 | 342篇 |
1987年 | 411篇 |
1986年 | 356篇 |
1985年 | 445篇 |
1984年 | 467篇 |
1983年 | 402篇 |
1982年 | 379篇 |
1981年 | 303篇 |
1980年 | 305篇 |
1979年 | 363篇 |
1978年 | 305篇 |
1977年 | 243篇 |
1976年 | 230篇 |
1975年 | 247篇 |
1974年 | 218篇 |
1973年 | 225篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Carels Robert A.; Cacciapaglia Holly; Pérez-Benítez Carlos I.; Douglass Olivia; Christie Samantha; O'Brien William H. 《Canadian Metallurgical Quarterly》2003,71(4):753
Reports an error in the original article by R. A. Carels et al (Journal of Consulting & Clinical Psychology, 2003[Jun], Vol 71[3], 613-618). On page 615, Lines 18, 20, 22, of Table 1, the data in the rows that read "Tachycardia in min per hr," "Repetitive PVCs per hr," and "PVCs per hr" are incorrectly reported in the n and % columns. They should have been reported in the M and SD columns. The corrected table is provided. (The following abstract of this article originally appeared in record 2003-00756-023.) Ventricular arrhythmia exhibits considerable within-subject variability that cannot be attributed to clinical status alone. This investigation examined the extent to which cardiac arrhythmia was associated with psychological and physical factors assessed during the hour preceding arrhythmic or nonarrhythmic activity. Approximately twice hourly, 46 patients randomly completed a diary assessing mood and physical symptoms during 24-hr electrocardiographic monitoring. Greater negative emotion was associated with increased arrhythmia. Additionally, greater negative emotion was significantly associated with increased arrhythmia among participants in a low left ventricular ejection fraction group (LVEF). However, this relationship between negative emotion and arrhythmia was not... (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
152.
Tony C. Scott Robert Mann Roberto E. Martinez II 《Applicable Algebra in Engineering, Communication and Computing》2006,17(1):41-47
We present a canonical form for a natural and necessary generalization of the Lambert W function, natural in that it requires minimal mathematical definitions for this generalization, and necessary in that it provides a means of expressing solutions to a number of physical problems of fundamental nature. This generalization expresses the exact solutions for general-relativistic self-gravitating N-body systems in one spatial and one time dimension, and a previously unknown mathematical link between the (1+1) gravity problem and the Schrödinger wave equation. 相似文献
153.
Jodi E Williams Susan E. Duncan Robert C. Williams Kumar Mallikarjunan William N. Eigel III Sean F. O'Keefe 《Journal of food science》2006,71(3):S265-S269
ABSTRACT: Flavor characteristics of roasted peanuts over short-term storage were explored through sensory and chemical analyses. The volatiles from freshly roasted peanuts were evaluated over short-time (21 d) storage using gas chromatography, chemosensory techniques, and a sensory panel to quantify and identify pyrazines and hexanal over a 21-d storage period. A significant decrease ( P < 0.05) was noted in 2,3-diethylpyrazine, 2-methoxypyrazine, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine, and 2,3,5-trimethylpyrazine concentrations over a 21-d period. No significant difference ( P > 0.05) was noted in the 2-methylpyrazine and 2-ethylpyrazine concentrations. The hexanal concentration significantly increased ( P < 0.05) over the 21-d period. The peroxide values and sensory analysis agreed with these results. A significant increase ( P < 0.05) in peroxide value was seen at days 14 and 21, and a significant decrease ( P < 0.05) in fresh roasted peanuty flavor from day 0 to 21 and significant increases ( P < 0.05) in painty, cardboardy, and bitter flavors from day 7 to 21 with the sensory analysis. The electronic nose successfully separated day 0 and 21 samples from day 7 and 14 samples, which were also separated but with some overlap. 相似文献
154.
Reports an error in "Current issues relating to psychosocial job strain and cardiovascular disease research" by T?res Theorell and Robert A. Karasek (Journal of Occupational Health Psychology, 1996[Jan], Vol 1[1], 9-26). On p. 12, in the caption to Figure 2, the copyright statement is missing. The caption should have read "The environment, the worker, and illness: Dynamic associations linking environmental strain and learning to evolution of personality. From Healthy Work: Stress, Productivity, and the Reconstruction of Working Life (p. 99), by R. A. Karasek and T. Theorell, 1990, New York: Basic Books. Copyright 1990 by Basic Books. Used with permission." (The following abstract of the original article appeared in record 1996-04477-002.) Examines recent reviews of cardiovascular (CV) job strain (JS) research by P. L. Schnall and P. A. Landsbergis (1994) and T. S. Kristensen (see record 1995-39109-001), which conclude that JS as defined by the demand-control model (the combination of contributions of low job decision latitudes and high psychological job demands) is confirmed as a risk factor for CV mortality in a large majority of studies. Lack of social support at work appears to increase this risk. Several still-unresolved issues are discussed in light of recent research. Methodological issues related to the use of occupational & career aggregate estimates, use of standard scales for job analysis, and recall bias in issues of self-reporting are examined. Confounding factors and differential strengths of associations by subgroups in JS-CV disease analyses with respect to social class, gender, and working hours are addressed. A review of results of monitoring JS-blood pressure associations and associated methodological issues is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
155.
156.
157.
Estimation is influenced by a variety of processes: application of heuristics, domain-specific reasoning, and intuitive statistical induction among them. In this article, the authors propose the metrics and mapping framework to account for how these processes are integrated to generate estimates. This framework identifies 2 types of information as critical: knowledge of distributional properties (metric knowledge) and knowledge of relative status of individual entities within the distribution (mapping knowledge). Heuristics and domain-specific knowledge are both viewed as cues that contribute to mapping knowledge; intuitive statistical induction is viewed as providing cues to metric properties. Results of 4 experiments illustrate the framework's usefulness for integrating these types of information and for predicting when people emphasize heuristics and when they emphasize domain-specific knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
158.
This paper highlights the role of the faculty member in recruiting students currently enrolled in B.S. programs in engineering and the sciences into full-time pursuit of a graduate-level engineering degree. The faculty member is demonstrated to be in a unique position to influence such students, providing strong counterforces to a confluence of attitudes and pressures experienced during the B.S. experience which effectively create a barrier to full-time engineering graduate study. We analyze this barrier via the method of force field analysis, and demonstrate that effective recruitment into full-time graduate study must be based on a four-fold strategy of education, expectations, improved B.S. experience and better control of the B.S. environment. Approaches to implement these strategies are discussed. 相似文献
159.
Biomaterials and biomedical engineering 总被引:1,自引:0,他引:1
Robert Langer 《Chemical engineering science》1995,50(24):4109-4121
The current status and future prospects of biomaterials, in the context of chemical engineering science and biomedical engineering, is examined. Research on artificial organs, controlled drug delivery systems, tissue engineering, materials for minimally invasive surgery, medical contrast imaging agents, gene therapy, immobilized enzyme bioreactors, and biosensors is evaluated. Techniques for assessing the performance of biomaterials are considered. The role of new types of materials, not yet used in medicine, such as electrically conducting polymers, is discussed. Finally, an analysis of future educational and training issues in biomaterials in the context of chemical engineering is provided. 相似文献
160.
Giving patients instructions to focus on sensory (vs emotional) stimuli during a root canal procedure significantly reduced self-reported pain, but only among patients who were classified as having strong desire for control and low felt control in dental situations. Among patients with low felt control and low desire for control, sensory-focus instructions produced greater pain reports than did emotion-focus instructions. Finally, high desire–low felt patients reported higher levels of expected pain before treatment than did other patient subgroups. These data suggested limiting conditions for H. Leventhal's (1982) theory of emotion and supported the idea that desire for control might moderate the effects of perceived control. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献