全文获取类型
收费全文 | 1542篇 |
免费 | 34篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 256篇 |
金属工艺 | 8篇 |
机械仪表 | 30篇 |
建筑科学 | 96篇 |
矿业工程 | 4篇 |
能源动力 | 54篇 |
轻工业 | 152篇 |
水利工程 | 14篇 |
石油天然气 | 4篇 |
无线电 | 96篇 |
一般工业技术 | 156篇 |
冶金工业 | 464篇 |
原子能技术 | 5篇 |
自动化技术 | 230篇 |
出版年
2023年 | 11篇 |
2022年 | 36篇 |
2021年 | 37篇 |
2020年 | 25篇 |
2019年 | 26篇 |
2018年 | 20篇 |
2017年 | 19篇 |
2016年 | 35篇 |
2015年 | 36篇 |
2014年 | 39篇 |
2013年 | 82篇 |
2012年 | 62篇 |
2011年 | 94篇 |
2010年 | 75篇 |
2009年 | 74篇 |
2008年 | 71篇 |
2007年 | 66篇 |
2006年 | 63篇 |
2005年 | 36篇 |
2004年 | 43篇 |
2003年 | 33篇 |
2002年 | 46篇 |
2001年 | 30篇 |
2000年 | 16篇 |
1999年 | 31篇 |
1998年 | 24篇 |
1997年 | 18篇 |
1996年 | 19篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 24篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 19篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 24篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1969年 | 6篇 |
排序方式: 共有1576条查询结果,搜索用时 31 毫秒
71.
Davies W. Hobart; Satter Ellyn; Berlin Kristoffer S.; Sato Amy F.; Silverman Alan H.; Fischer Elizabeth A.; Arvedson Joan C.; Rudolph Colin D. 《Canadian Metallurgical Quarterly》2006,20(3):409
The feeding of young children is fundamentally a relational and multisystemic process. Successful treatment of clinically significant feeding problems involves careful assessment of the full range of influences on the feeding relationship and integrated treatment approaches. However, current diagnostic approaches to feeding disorders tend to be reductionistic, exclusively focused on the child as an individual, and overly concerned with exclusionary criteria. Criteria are proposed for "Feeding Disorder Between Parent and Child" that address these limitations and embrace the complexity of feeding problems. A multiaxial diagnosis that describes the child (including medical, developmental, and behavioral characteristics); the parent; the parent-child relationship; and the social and nutritional context of feeding will more accurately speak to treatment planning in this population. The proposed diagnostic criteria were developed and refined on the basis of the available literature and many years of treatment experience across the authors of this article. The proposed diagnosis will support the development and evaluation of treatment packages with components specifically targeted to issues of the child, parent, parent-child interaction, and the broader environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
72.
Heil Sarah H.; Higgins Stephen T.; Mongeon Joan A.; Badger Gary J.; Bernstein Ira M. 《Canadian Metallurgical Quarterly》2006,14(2):165
Maternal smoking is a leading preventable cause of poor pregnancy outcomes and infant morbidity and mortality. Whereas pregnancy has been thought of as a "window of opportunity" when women are more motivated to change health behaviors such as smoking, only 20% of pregnant women quit smoking upon learning they are pregnant and remain abstinent at the end of the pregnancy. Greater understanding of possible obstacles to smoking during pregnancy, such as nicotine withdrawal, is needed. The symptoms of nicotine withdrawal have been well characterized in nonpregnant smokers, but there has been only 1 report conducted during pregnancy, and that was a retrospective study. The aim of the present study was to characterize nicotine withdrawal and craving in pregnant cigarette smokers. These data were collected as part of prospective clinical trials assessing the efficacy of voucher-based incentives to promote abstinence from cigarette smoking during pregnancy and postpartum. The authors examined results from the Minnesota Nicotine Withdrawal Scale (J. R. Hughes & D. K. Hatsukami, 1998) in 27 abstainers (reported no or very low levels of smoking, which was confirmed biochemically) and 21 smokers (smoked at >80% of their baseline smoking level) during the first 5 days of a cessation attempt. Abstainers reported more impatience, anger, and difficulty concentrating than did smokers. The results also suggest that pregnant smokers generally may have elevated baseline levels of withdrawal, which need to be considered in the design and analysis of future studies. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Ground measurements for the validation of land surface temperatures derived from AATSR and MODIS data 总被引:1,自引:0,他引:1
César Coll Vicente Caselles Joan M. Galve Enric Valor Raquel Niclòs Juan M. Sánchez Raúl Rivas 《Remote sensing of environment》2005,97(3):288-300
An experimental site was set up in a large, flat and homogeneous area of rice crops for the validation of satellite derived land surface temperature (LST). Experimental campaigns were held in the summers of 2002-2004, when rice crops show full vegetation cover. LSTs were measured radiometrically along transects covering an area of 1 km2. A total number of four thermal radiometers were used, which were calibrated and inter-compared through the campaigns. Radiometric temperatures were corrected for emissivity effects using field emissivity and downwelling sky radiance measurements. A database of ground-based LSTs corresponding to morning, cloud-free overpasses of Envisat/Advanced Along-Track Scanning Radiometer (AATSR) and Terra/Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. Ground LSTs ranged from 25 to 32 °C, with uncertainties between ± 0.5 and ± 0.9 °C. The largest part of these uncertainties was due to the spatial variability of surface temperature. The database was used for the validation of LSTs derived from the operational AATSR and MODIS split-window algorithms, which are currently used to generate the LST product in the L2 level data. A quadratic, emissivity dependent split-window equation applicable to both AATSR and MODIS data was checked as well. Although the number of cases analyzed is limited (five concurrences for AATSR and eleven for MODIS), it can be concluded that the split-window algorithms work well, provided that the characteristics of the area are adequately prescribed, either through the classification of the land cover type and the vegetation cover, or with the surface emissivity. In this case, the AATSR LSTs yielded an average error or bias of − 0.9 °C (ground minus algorithm), with a standard deviation of 0.9 °C. The MODIS LST product agreed well with the ground LSTs, with differences comparable or smaller than the uncertainties of the ground measurements for most of the days (bias of + 0.1 °C and standard deviation of 0.6 °C, for cloud-free cases and viewing angles smaller than 60°). The quadratic split-window algorithm resulted in small average errors (+ 0.3 °C for AATSR and 0.0 °C for MODIS), with differences not exceeding ± 1.0 °C for most of the days (standard deviation of 0.9 °C for AATSR and 0.5 °C for MODIS). 相似文献
74.
Cole David A.; Nolen-Hoeksema Susan; Girgus Joan; Paul Gilda 《Canadian Metallurgical Quarterly》2006,115(1):40
In 2 longitudinal studies of negative life events and depressive symptoms in adolescents (N = 708) and in children (N = 508), latent trait-state-error structural equation models tested both the stress generation hypothesis and the stress exposure hypothesis. Results strongly suggested that self-reports of depressive symptoms reflect the influence of a perfectly stable trait factor as well as a less stable state factor. Support emerged for both the stress generation model and the stress exposure model. When the state depression factor was modeled as predicting stress, support for the stress generation model appeared to increase with age. When the trait depression factor was modeled as the predictor of stress, support for the stress generation model did not vary with the child's age. In both models, support for the stress exposure remained relatively constant across age. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Tucker Joan S.; Ellickson Phyllis L.; Collins Rebecca L.; Klein David J. 《Canadian Metallurgical Quarterly》2006,20(4):363
This longitudinal study compared Grade 8 solitary cigarette smokers (n = 541), drinkers (n = 577), and marijuana users (n = 148) with adolescents who restricted their use of these substances to social settings (ns = 562, 1,426, and 388, respectively) on adolescent functioning and young adult outcomes. In Grade 8, solitary users held more positive beliefs about the consequences of substance use, earned poorer grades, engaged in more deviant behavior, and devoted less time to school and more time to social activities. By age 23, these solitary users had lower educational attainment, poorer self-rated health, and greater substance use problems. Results indicate the importance of better understanding and addressing the needs of this understudied group of high-risk youth. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
76.
Joan Moss Ruth Beatty 《International Journal of Computer-Supported Collaborative Learning》2006,1(4):441-465
While it has been suggested that patterning activities support early algebra learning, it is widely acknowledged that the
shift from perceiving patterns to understanding algebraic functions—and correspondingly, from reporting empirical patterns
to providing explanations—is difficult. This paper reports on the collaborations of grade 4 students (n = 68) from three classrooms in diverse urban settings, connected through a knowledge-building environment (Knowledge Forum),
when solving mathematical generalizing problems as part of an early algebra research project. The purpose of this study was
to investigate the underlying principles of idea improvement and epistemic agency and the potential of knowledge building—as
supported by Knowledge Forum—to support student work. Our analyses of student-generated collaborative workspaces revealed
that students were able to find multiple rules for challenging problems and revise their own conjectures regarding those rules.
Furthermore, the discourse was sustained over 8 weeks and students were able to find similarities across problem types without
the support of teachers or researchers, suggesting that these grade-4 students had developed a disposition for evidence use
and justification that eludes much older students. 相似文献
77.
Miguel A. Rodriguez Joan E. Ricart Pablo Sanchez 《Creativity & Innovation Management》2002,11(3):135-146
Does the need for sustainable development hinder businesses’ ability to create value? Is a firm’s competitiveness negatively affected by considering that need? After quickly reviewing the main literature contributions on the relationship between business and society, and drawing from resource‐based view of the firm and sustainable development literature, this paper presents a proposal for a dynamic and sustainable view of the firm. It shows how considering the changes introduced into the competitive landscape by sustainable development influences the way in which companies develop their resources, capabilities and activities, fostering the persistence of competitive advantages based on knowledge and innovation. 相似文献
78.
Joan Peuteman Joan Peuteman Dirk Aeyels 《Mathematics of Control, Signals, and Systems (MCSS)》2002,15(3):202-228
Let be a time-varying vector field depending on t containing a regular and a slow time scale (α large). Assume there exist a k (τ)≥1 and a γ(τ) such that ∥x
τ(t, t
0, x
0)∥≤k(τ) e
−γ(τ)(t−t0)∥x
0∥, with x
τ(t, t
0, x
0) the solution of the parametrized system with initial state x
0 at t
0. We show that for α sufficiently large is exponentially stable when “on average”γ(τ) is positive. The use of this result is illustrated by means of two examples.
First, we extend the circle criterion. Second, exponential stability for a pendulum with a nonlinear slowly time-varying friction
attaining positive and negative values is discussed.
Date received: January 22, 2000. Date revised: April 14, 2001. 相似文献
79.
Katz Jonathan F.; Adler Joan C.; Mazzarella Nicholas J.; Ince Laurence P. 《Canadian Metallurgical Quarterly》1985,30(1):53
Examined the effects of a 12-wk exercise training program on the mood states (assessed via the Profile of Mood States [POMS]) of a 27-yr-old spinal-cord-injured male in a rehabilitation hospital. S was administered the POMS immediately before and after the program and once each week during the program. S demonstrated major mood changes following exercise training, indicating a significant decrease in tension, depression, anger, fatigue, and confusion and a significant increase in vigor. Findings support the hypothesis that vigorous physical exercise can be a useful therapeutic strategy with the disabled. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
73 teachers of kindergarten to 8th grade viewed disruptive- or nondisruptive-context videotaped vignettes and rated each portrayal in terms of severity, manageability, tolerance, and contagion to investigate the effects of context on Ss' perceptions of 5 problem behaviors (blaming, poor peer cooperation, negative aggression, inattention, and failure anxiety). ANCOVA showed that contagion yielded significant differences (stronger within the disruptive context), suggesting that the target child was held responsible for the classroom disorder. Correlational data explained the relationship between the 4 areas, suggesting a dichotomy between quality (type of behavior) and quantity (degree or severity of behavior) for interpreting perceptions. Low tolerance was associated with higher levels of severity and more outer-directed behaviors. Contagion had more active, observable components and was related more to the qualitative dimension. Manageability (also active, observable, and teacher centered) was strongly influenced by quantitative factors (greater extremes of atypical behavior). (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献