全文获取类型
收费全文 | 2101篇 |
免费 | 70篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 384篇 |
金属工艺 | 12篇 |
机械仪表 | 30篇 |
建筑科学 | 109篇 |
矿业工程 | 6篇 |
能源动力 | 78篇 |
轻工业 | 230篇 |
水利工程 | 22篇 |
石油天然气 | 11篇 |
无线电 | 193篇 |
一般工业技术 | 236篇 |
冶金工业 | 479篇 |
原子能技术 | 8篇 |
自动化技术 | 353篇 |
出版年
2023年 | 22篇 |
2022年 | 49篇 |
2021年 | 66篇 |
2020年 | 45篇 |
2019年 | 37篇 |
2018年 | 39篇 |
2017年 | 38篇 |
2016年 | 50篇 |
2015年 | 47篇 |
2014年 | 55篇 |
2013年 | 127篇 |
2012年 | 95篇 |
2011年 | 129篇 |
2010年 | 97篇 |
2009年 | 102篇 |
2008年 | 104篇 |
2007年 | 95篇 |
2006年 | 89篇 |
2005年 | 59篇 |
2004年 | 59篇 |
2003年 | 49篇 |
2002年 | 61篇 |
2001年 | 38篇 |
2000年 | 20篇 |
1999年 | 41篇 |
1998年 | 38篇 |
1997年 | 24篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 37篇 |
1992年 | 27篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 23篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 8篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 14篇 |
1974年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有2171条查询结果,搜索用时 15 毫秒
101.
We present a numerical formulation to compute optical parameters in a turbulent air flow. The basic numerical formulation is a large eddy simulation (LES) of the incompressible Navier-Stokes equations, which are approximated using a finite element method. From the time evolution of the flow parameters we describe how to compute statistics of the flow variables and, from them, the parameters that determine the quality of the visibility. The methodology is applied to estimate the optical quality around telescope enclosures. 相似文献
102.
103.
Four of Rodolfa et al.’s (2005) competencies in professional psychology—relationship, self-reflection, assessment-case conceptualization, and intervention—are key for the psychodynamic psychotherapist. Relationship lies at the heart of what is understood to be curative about psychodynamic psychotherapy. Self-reflection implies a complex and highly developed process that includes but goes beyond Rodolfa et al.’s and Kaslow, Dunn, and Smith’s (2008) definitions. Competent assessment, diagnosis, and case conceptualization entails making inferences about unconscious processes by observing the client and also one’s own experience, and integrating these inferences with theory. Effective psychodynamic intervention is derived from what the psychotherapist has experienced, processed, and conceptualized about the relationship with the client and about the client’s internal object world. An extended vignette shows these competencies emerging in a psychotherapist-in-training, facilitated by an intense interaction with a supervisor. Although the supervisory and clinical tasks are different, the supervisor provides a relationship experience that models these same competencies for the supervisee and catalyzes their development in the supervisee. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
104.
Joan R. Casas 《Construction and Building Materials》2009,23(8):2964-2972
The paper presents the development of a model for the fatigue resistance of brick masonry under compression. The model takes into account the random nature of the fatigue strength phenomena and, as a consequence, proposes different model parameters as a function of the desired probability level. The model, based on a Weibull distribution, has been calibrated with the still limited experimental data on brick masonry under high cycle compression loading. Very good correlation is obtained. The results show that there is a clear trend of the experimental data to follow the Weibull distribution. It is also shown how the fatigue resistance of brick masonry is not only dependent on the magnitude of the stress cycles, but also on the magnitude of the minimum stress level. The paper also shows how the proposed model can be used in the reliability-based assessment of the fatigue performance of existing masonry arch bridges. Either the nominal probability of failure (reliability index) to fatigue or the remaining service life with a predefined probability level for an existing bridge can be predicted with the proposed method. 相似文献
105.
Gross PA Patriaco D McGuire K Skurnick J Teichholz LE 《The Joint Commission journal on quality improvement》2002,28(10):566-573
BACKGROUND: Telemetry monitoring is widely used in hospitals; the importance of being able to monitor and examine dysrhythmias has been universally accepted. Yet it is often used for patients who do not actually require this technology. A model to improve the efficiency of telemetry use entailed the use of an advanced practice nurse (APN; identical to a nurse practitioner) to provide concurrent review and intervention of floating telemetry, which is available for patients independently of the floor location and who do not need an intensive care unit bed. ADDRESSING OVERUSE: The demand for floating telemetry at Hackensack University Medical Center had equaled or exceeded the telemetry availability virtually 100% of the time, even after local guidelines had been disseminated in 1998. The APN carried out concurrent monitoring and intervened with the attending physician when patients were on telemetry for longer than 48 hours and did not meet the local telemetry guidelines. RESULTS: The mean number (standard error [SE]) of hours per patient declined from 65.2 +/- 0.7 hours (95% confidence interval, 63.8 to 66.6 hours) for the 11 months before the intervention to a mean of 49.6 +/- 0.4 hours (95% confidence interval, 48.7 to 50.2 hours) for the 29 months after intervention--representing a decrease of 34% (p < 0.0001). This decrease led to an increase in the number of patients per month put on telemetry. DISCUSSION: The APN model, an aggressive approach that induced change almost immediately, was then applied to other quality improvement projects. 相似文献
106.
Merging Information Under Constraints: A Logical Framework 总被引:9,自引:0,他引:9
107.
Ricardo Toledo Ramon Baldrich Xavier Orriols Juan Sanchez Xavier Binefa 《Multimedia Tools and Applications》2006,31(2):119-144
Advertising activities are one of the main aspects of companies. Its global evaluation is an important index, not only within economic sectors, but also for public economic policies. The evaluation of the adverts is carried out by specialised companies, which deliver advertisement expenditure information. Their work consist in an exhaustive collection of adverts (e.g., all adverts from any media), and deliver information (integrated from every media) relevant for their clients. The delivered information can range from statistical data to bear witness of an advertisement campaign. Important quality indicators for the delivered information are the exhaustiveness, the delay of delivering and a correct identification of different versions of an advert. In this article, we present an advanced computer-aided system for collecting and delivering advertising information from magazines and daily press. The system provides computer-aided data validation and exploitation resources. Using computerised document image analysis and image database indexing and retrieval, the system is able to locate an advert in a page, extract relevant quality indicators and search the advert (or similar ones) in a database. This tool is configured as an intranet and offers resources for image data acquisition, storage/retrieval and advert quality indicators extraction, however, the key of the system is the underlying idea of incorporating computer-aided visual information management.The EU has funded the system construction within the program: European Take-up of essential Information Society Technologies, Integrated Machine Vision (EUTIST-IMV), task CV-AdControl. . 相似文献
108.
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
109.
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
110.
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