全文获取类型
收费全文 | 4114篇 |
免费 | 99篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 3篇 |
化学工业 | 617篇 |
金属工艺 | 18篇 |
机械仪表 | 32篇 |
建筑科学 | 202篇 |
矿业工程 | 85篇 |
能源动力 | 55篇 |
轻工业 | 433篇 |
水利工程 | 26篇 |
石油天然气 | 6篇 |
无线电 | 117篇 |
一般工业技术 | 428篇 |
冶金工业 | 1707篇 |
原子能技术 | 9篇 |
自动化技术 | 451篇 |
出版年
2022年 | 34篇 |
2021年 | 64篇 |
2020年 | 34篇 |
2019年 | 48篇 |
2018年 | 50篇 |
2017年 | 60篇 |
2016年 | 74篇 |
2015年 | 53篇 |
2014年 | 58篇 |
2013年 | 216篇 |
2012年 | 144篇 |
2011年 | 186篇 |
2010年 | 169篇 |
2009年 | 153篇 |
2008年 | 199篇 |
2007年 | 198篇 |
2006年 | 143篇 |
2005年 | 168篇 |
2004年 | 136篇 |
2003年 | 155篇 |
2002年 | 126篇 |
2001年 | 97篇 |
2000年 | 84篇 |
1999年 | 99篇 |
1998年 | 82篇 |
1997年 | 86篇 |
1996年 | 99篇 |
1995年 | 75篇 |
1994年 | 85篇 |
1993年 | 99篇 |
1992年 | 96篇 |
1991年 | 37篇 |
1990年 | 84篇 |
1989年 | 68篇 |
1988年 | 70篇 |
1987年 | 71篇 |
1986年 | 72篇 |
1985年 | 61篇 |
1984年 | 53篇 |
1983年 | 48篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 21篇 |
1979年 | 33篇 |
1978年 | 29篇 |
1977年 | 14篇 |
1976年 | 19篇 |
1975年 | 17篇 |
1974年 | 13篇 |
1973年 | 16篇 |
排序方式: 共有4214条查询结果,搜索用时 15 毫秒
241.
Hooper Stephen R.; Roberts Joanne; Sideris John; Burchinal Margaret; Zeisel Susan 《Canadian Metallurgical Quarterly》2010,46(5):1018
This study's primary purpose was to examine the relative contribution of social-behavioral predictors to reading and math skills. The study expands on Duncan et al.'s (2007) work by using longitudinal methodology from the National Institute of Child Health and Human Development's Study of Child Care and Youth Development (SECCYD) and the Early Childhood Longitudinal Study, Kindergarten Class of 1998–1999 (ECLS-K) databases, and by focusing on potential differences in patterns of early predictors of later reading and math trajectories for African American versus Caucasian students. Predictor measures were selected at kindergarten, and the outcomes included standardized reading and math scores obtained from Grades 1, 3, 5, and 9 for the SECCYD sample, and Grades 3, 5, and 8 for the ECLS-K sample. Consistent with Duncan et al.'s findings, results reflect the relative contributions of early reading and math skills to later functioning in these respective academic domains for both samples, and there are indications for the importance of early expressive language skills to both reading and math in the SECCYD sample. Findings related to the power of social-behavioral predictors, however, are not consistent across samples. Although the SECCYD sample evidenced no such predictors, several interactions in the ECLS-K sample suggested the moderating effects of early ratings of aggressive behaviors and internalizing behaviors on later reading and math for African American students. The moderating effects of early teacher ratings of attention and internalizing behaviors for African American students as compared with Caucasian students in later math growth also were noted. The importance of early social-behavioral functions as related to later academic skills remains an important area of inquiry. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
242.
Objective: Interventions are increasingly described as theory-based; however, the basis for this is often not clear. Advancing behavioral science requires a good understanding of how interventions are informed by, and test, theory. This study aims to develop a reliable method for assessing the extent to which behavioral interventions are theory-based. Design: The reliability, usability, and comprehensiveness of an initial coding scheme were improved in 13 iterative stages on the basis of its application to 29 papers, from a systematic review of interventions to promote physical activity and healthy eating. Results: The final Theory Coding Scheme contained 19 items, each with satisfactory interrater reliabilities, coding whether a theory or model was mentioned, how theories were used in intervention design, how intervention evaluations tested theory, and the implications of the results for future theory development. Conclusion: The Theory Coding Scheme is an important methodological innovation, providing a research tool to reliably describe the theoretical base of interventions, inform evidence syntheses within literature reviews and meta-analyses, and stimulate the use of empirical data for theory development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
243.
Zhiling Lan Jiexing Gu Ziming Zheng Rajeev Thakur Susan Coghlan 《Journal of Parallel and Distributed Computing》2010
Despite years of study on failure prediction, it remains an open problem, especially in large-scale systems composed of vast amount of components. In this paper, we present a dynamic meta-learning framework for failure prediction. It intends to not only provide reasonable prediction accuracy, but also be of practical use in realistic environments. Two key techniques are developed to address technical challenges of failure prediction. One is meta-learning to boost prediction accuracy by combining the benefits of multiple predictive techniques. The other is a dynamic approach to dynamically obtain failure patterns from a changing training set and to dynamically extract effective rules by actively monitoring prediction accuracy at runtime. We demonstrate the effectiveness and practical use of this framework by means of real system logs collected from the production Blue Gene/L systems at Argonne National Laboratory and San Diego Supercomputer Center. Our case studies indicate that the proposed mechanism can provide reasonable prediction accuracy by forecasting up to 82% of the failures, with a runtime overhead less than 1.0 min. 相似文献
244.
An introduction to DNA microarrays for gene expression analysis 总被引:1,自引:0,他引:1
Tobias K. Karakach Susan E. Douglas 《Chemometrics and Intelligent Laboratory Systems》2010,104(1):28-52
This tutorial presents a basic introduction to DNA microarrays as employed for gene expression analysis, approaching the subject from a chemometrics perspective. The emphasis is on describing the nature of the measurement process, from the platforms used to a few of the standard higher-level data analysis tools employed. Topics include experimental design, detection, image processing, measurement errors, ratio calculation, background correction, normalization, and higher-level data processing. The objective is to present the chemometrician with as clear a picture as possible of an evolving technology so that the strengths and limitations of DNA microarrays are appreciated. Although the focus is primarily on spotted, two-color microarrays, a significant discussion of single-channel, lithographic arrays is also included. 相似文献
245.
The growth and electrical properties of Pb(Yb 1/2 Nb 1/2 )O 3 -PbTiO 3 (PYbN-PT) epitaxial films were investigated. PYbN-PT epitaxial films with SrRuO 3 bottom electrodes were grown by pulsed laser deposition. Optimization of the growth conditions for the PYbN-PT epitaxial films was carried out on (100) SrRuO 3 /(100) LaAlO 3 substrates using the (50/50) composition target. It was found that formation of pyrochlore phase could be caused not only by low growth temperatures or lead deficiency, but also by poor surface condition of the SrRuO 3 bottom electrodes. (001) PYbN-PT epitaxial films with good crystalline quality were obtained for a range of deposition rates (60-100 nm/min) and temperatures (620-680 °C) after vacuum annealing the SrRuO 3 bottom electrodes. The ferroelectric and piezoelectric properties of 1 w m-thick PYbN-PT epitaxial films with (50/50) and (60/40) compositions and with (001) and (111) orientations were investigated using (100) LaAlO 3 , (100) SrTiO 3 , and (111) SrTiO 3 substrates with SrRuO 3 bottom electrodes. The highest remanent polarization (29 w C/cm 2 ) and effective piezoelectric coefficient e 31.f ( m 14 C/m 2 ) were observed in the (001) PYbN-PT (50/50) film. The transition temperature of the (001) PYbN-PT (50/50) film was about 380 °C. Because of the degradation of the target during the deposition, a 3 w m-thick film was prepared by three depositions (1 w m each layer). The 3 w m-thick film exhibited a higher e 31.f coefficient of m 19 C/m 2. 相似文献
246.
Robinson-Whelen Susan; Hughes Rosemary B.; Powers Laurie E.; Oschwald Mary; Renker Paula; Swank Paul R.; Curry Mary Ann 《Canadian Metallurgical Quarterly》2010,55(2):97
Objective: To evaluate the effects of a computerized disability-specific abuse assessment intervention on abuse awareness, safety self-efficacy, and safety promoting behaviors of women with diverse disabilities. Research Design: A randomized control group design was used, with the intervention group completing the assessment intervention both at Time 1 (T1) and 3 months later at Time 2 (T2) and control participants completing it for the first time at T2. Analyses compared intervention and control groups at T2 and evaluated change over time in intervention group participants. The relationship between outcome variables (abuse awareness, safety self-efficacy, safety behaviors) was also explored. Results: The intervention group had greater abuse awareness than the control group at T2, and abuse awareness increased from T1 to T2 among women in the intervention group, particularly among women who had experienced little or no abuse in the past year. Both abuse awareness and safety self-efficacy were significantly related to safety behaviors. Conclusions: The computerized program offers promise as a nonthreatening method of conducting abuse assessments among women with disabilities while also serving as an intervention to enhance abuse awareness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
247.
Reddy Felice; Spaulding William D.; Jansen Mary A.; Menditto Anthony A.; Pickett Susan 《Canadian Metallurgical Quarterly》2010,4(4):254
The emergence of psychiatric rehabilitation and the recovery movement generate new and expanded roles for psychologists in services for people with serious mental illness (SMI). However, the proportion of psychologists working in SMI services today is substantially less than previous decades. This article reviews the roles of psychologists in various mental health systems and outlines the contributions that psychologists can make in implementing evidence based approaches for people with SMI. A survey of American Psychology Association (APA)-accredited Council of University Directors of Clinical Psychology (CUDCP) Clinical Psychology doctoral programs was conducted. The results of the survey indicate an increase, since the early 1990s, in clinical faculty with SMI interests, and suggest that many graduate programs provide opportunities for SMI-relevant research and practicum training. However, the survey also indicates a lack of coursework on topics relevant to SMI and a lack of coursework relevant to assuming administrative and leadership roles in the mental health system. Despite training opportunities in graduate school, production of new PhDs who choose the SMI field is unlikely to meet the demand. According to the present study, the limiting factor is not availability of training, but student career choice. The opportunities and challenges that psychologists face in SMI recovery-oriented service delivery are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
248.
Lori E. Lowes Scott V. Bratman Ryan Dittamore Susan Done Shana O. Kelley Sabine Mai Ryan D. Morin Alexander W. Wyatt Alison L. Allan 《International journal of molecular sciences》2016,17(9)
Despite the identification of circulating tumor cells (CTCs) and cell-free DNA (cfDNA) as potential blood-based biomarkers capable of providing prognostic and predictive information in cancer, they have not been incorporated into routine clinical practice. This resistance is due in part to technological limitations hampering CTC and cfDNA analysis, as well as a limited understanding of precisely how to interpret emergent biomarkers across various disease stages and tumor types. In recognition of these challenges, a group of researchers and clinicians focused on blood-based biomarker development met at the Canadian Cancer Trials Group (CCTG) Spring Meeting in Toronto, Canada on 29 April 2016 for a workshop discussing novel CTC/cfDNA technologies, interpretation of data obtained from CTCs versus cfDNA, challenges regarding disease evolution and heterogeneity, and logistical considerations for incorporation of CTCs/cfDNA into clinical trials, and ultimately into routine clinical use. The objectives of this workshop included discussion of the current barriers to clinical implementation and recent progress made in the field, as well as fueling meaningful collaborations and partnerships between researchers and clinicians. We anticipate that the considerations highlighted at this workshop will lead to advances in both basic and translational research and will ultimately impact patient management strategies and patient outcomes. 相似文献
249.
Susan J. Altman Richard P. Jensen Malynda A. Cappelle Andres L. Sanchez Randy L. Everett Howard L. Anderson Lucas K. McGrath 《Desalination》2012
A pilot study was conducted to determine whether membrane treatment on a side stream of recirculating cooling-tower water could reduce overall water usage and discharge. The treated permeate was returned to the cooling tower while the concentrate was discharged to the sanitary sewer. Flow rates, pressures and water chemistry were monitored. The pilot demonstrated potential substantial water savings. Maximum make-up water and discharge reduction were 16% and 49%, respectively. As high as possible permeate recovery is needed to maximize water conservation. Silica scaling on the membranes limited water savings in this pilot. Development of membranes with a solute-rejection capacity less than the 92% average of the membranes used in the pilot would assist in optimizing water savings. Decreased water outlays compensated for the additional energy used by membrane treatment. Scaling control is critical for economic operation. 相似文献
250.
Viju Susan Mathew P. Jyotishkumar Soney.C. George Preetha Gopalakrishnan Laurent Delbreilh Jean Marc Saiter Prakash J. Saikia Sabu Thomas 《应用聚合物科学杂志》2012,125(1):804-811
An attempt was made to toughen diglycidyl ether of bisphenol A (DGEBA) type epoxy resin with liquid natural rubber possessing hydroxyl functionality (HTLNR). Epon 250 epoxy monomer is cured using nadic methyl anhydride as hardener in presence of N, N dimethyl benzyl amine as accelerator. HTLNR of different concentrations up to 20 wt % is used as modifier for epoxy resin. The addition HTLNR to an anhydride hardener/epoxy monomer mixture has given rise to the formation of phase-separated structure, consisting of small spherical liquid natural rubber particles bonded to the surrounding epoxy matrix. The particle size increased with increase in rubber content. The viscoelastic properties of the blends were analyzed using dynamic mechanical thermal analysis. The Tg corresponding to epoxy rich phase was evident from the dynamic mechanical spectrum, while the Tg of the rubber phase was overlapped by the β relaxation of epoxy phase. Glass transition of the epoxy phase decreased linearly as a function of the amount of rubber. The mechanical properties such as impact and fracture toughness were also carefully examined. The impact and fracture toughness increase with HTLNR content. A threefold increase in impact strength was observed with 15 wt % HTLNR/epoxy blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献