全文获取类型
收费全文 | 2500篇 |
免费 | 62篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 18篇 |
综合类 | 1篇 |
化学工业 | 323篇 |
金属工艺 | 32篇 |
机械仪表 | 50篇 |
建筑科学 | 119篇 |
矿业工程 | 7篇 |
能源动力 | 62篇 |
轻工业 | 262篇 |
水利工程 | 23篇 |
石油天然气 | 6篇 |
无线电 | 226篇 |
一般工业技术 | 325篇 |
冶金工业 | 855篇 |
原子能技术 | 28篇 |
自动化技术 | 232篇 |
出版年
2023年 | 17篇 |
2022年 | 25篇 |
2021年 | 32篇 |
2020年 | 28篇 |
2019年 | 36篇 |
2018年 | 24篇 |
2017年 | 30篇 |
2016年 | 44篇 |
2015年 | 27篇 |
2014年 | 47篇 |
2013年 | 111篇 |
2012年 | 83篇 |
2011年 | 109篇 |
2010年 | 73篇 |
2009年 | 57篇 |
2008年 | 82篇 |
2007年 | 92篇 |
2006年 | 82篇 |
2005年 | 78篇 |
2004年 | 61篇 |
2003年 | 63篇 |
2002年 | 64篇 |
2001年 | 57篇 |
2000年 | 46篇 |
1999年 | 56篇 |
1998年 | 165篇 |
1997年 | 135篇 |
1996年 | 87篇 |
1995年 | 54篇 |
1994年 | 56篇 |
1993年 | 44篇 |
1992年 | 30篇 |
1991年 | 25篇 |
1990年 | 28篇 |
1989年 | 25篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 21篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 30篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 36篇 |
1976年 | 46篇 |
1975年 | 15篇 |
1974年 | 22篇 |
排序方式: 共有2569条查询结果,搜索用时 0 毫秒
191.
Bayesian decision threshold, detection limit and confidence limits in ionising-radiation measurement
Weise K Hübel K Rose E Schläger M Schrammel D Täschner M Michel R 《Radiation protection dosimetry》2006,121(1):52-63
Based on Bayesian statistics and the Bayesian theory of measurement uncertainty, characteristic limits such as the decision threshold, detection limit and limits of a confidence interval can be calculated taking into account all sources of uncertainty. This approach consists of the complete evaluation of a measurement according to the ISO Guide to the Expression of Uncertainty in Measurement (GUM) and the successive determination of the characteristic limits by using the standard uncertainty obtained from the evaluation. This procedure is elaborated here for several particular models of evaluation. It is, however, so general that it allows for a large variety of applications to similar measurements. It is proposed for the revision of those parts of DIN 25482 and ISO 11929 that are still based on conventional statistics and, therefore, do not allow to take completely into account all the components of measurement uncertainty in the calculation of the characteristic limits. 相似文献
192.
A.R. Fernandes C. Tlustos F. Smith M. Carr R. Petch M. Rose 《Food Additives and Contaminants: Part B: Surveillance Communications》2013,6(1):86-94
Brominated dioxins (PBDD/Fs) and 17 polybrominated diphenylether (PBDE) congeners including BDE-209 were analysed in 100 composite samples of commonly consumed foods of animal origin, prepared from ten to 40 individual subsamples of each type. These included 30 samples of milk from farms; eggs from chickens; fat from cows, pigs, sheep, and poultry; and liver from cows, pigs, sheep, horses, and poultry. The ISO 17025-accredited analytical methodology used, follows similar guidelines as given for chlorinated dioxins and polychlorinated biphenyls (PCBs) in European Commission Directive 2002/69/EC. Apart from some samples of milk, PBDD/Fs and PBDEs were detected in all food types. Concentrations ranged from 0.31 µg kg?1 Σ17 PBDEs for a sample of milk to 37.5 µg kg?1 Σ17 PBDEs for a sample of liver. The corresponding range for the PBDD/F toxicity (computed using analogous PCDD/F toxic equivalency factors (TEFs)) was 0.09 ng TEQ kg?1 to approximately 3.5 ng TEQ kg?1. The detection of these compounds, in particular PBDD/Fs, is consistent with the increased use and disposal of brominated organic compounds. 相似文献
193.
Haley William E.; Larson Dale G.; Kasl-Godley Julia; Neimeyer Robert A.; Kwilosz Donna M. 《Canadian Metallurgical Quarterly》2003,34(6):626
Professional psychologists are increasingly likely to encounter opportunities to work with patients and families facing end-of-life issues. Psychologists can provide psychological assessment, intervention for patients and families, consultation with and support of health care team members, grief therapy, and program development and evaluation. Psychological services are useful for healthy individuals who wish to make thoughtful plans about their own future care, patients with life-limiting illnesses, families stressed by providing end-of-life care, bereaved individuals, and health care providers who face issues of burnout and strain. Several challenges for psychologists working in end-of-life care are noted, including training, development of clear roles, and reimbursement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
194.
Housing is widely regarded as playing an important role in the mediation and management of health inequalities. British policy-makers are increasingly looking to the research community to specify what it is about housing environments that impact on health, and to identify what housing interventions constitute healthy public policies. To feed into this debate, this paper begins by reviewing the state of the art of research on housing and health. It shows that the majority of work continues to focus on how housing affects health, while the limited attention to how health status affects housing outcomes has concentrated on medical priority for rehousing in the public sector. It is argued, however, that the market sector now merits closer scrutiny among those concerned with the health selectivity of the housing system. Drawing on a series of qualitative interviews, questions are raised about: how readily people with health problems and mobility difficulties gain access to owner occupation; how easily they sustain a position in that tenure sector; and how effective they are in maintaining their homes as healthy enabling living environments. 相似文献
195.
M. Aarthy P. Saravanan M.K. Gowthaman C. Rose N.R. Kamini 《Chemical Engineering Research and Design》2014
Biodiesel has provided an eco-friendly solution to fuel crisis, as it is renewable, biodegradable and a non-toxic fuel that can be easily produced through enzymatic transesterification of vegetable oils and animal fats. Enzymatic production of biodiesel has many advantages over the conventional methods as high yields can be obtained at low reaction temperatures with easy recovery of glycerol. Microbial lipases are powerful biocatalysts for industrial applications including biodiesel production at lower costs due to its potential in hydrolyzing waste industrial materials. Among them, lipases from yeasts, Candida antarctica, Candida rugosa, Cryptococcus sp., Trichosporon asahii and Yarrowia lipolytica are known to catalyze such reactions. Moreover, stepwise addition of methanol in a three step, two step and single step reactions have been developed using yeast lipases to minimize the inhibitory effects of methanol. The latest trend in biodiesel production is the use of whole-cell as biocatalysts, since the process requires no downstream processing of the enzyme. Synthesis of value added products from the byproduct glycerol further reduces the production cost of biodiesel. This review aims at compiling the information on various yeast lipase catalyzed transesterification reactions for greener production of biodiesel. 相似文献
196.
Wey Yang Teoh Frans Denny Rose Amal Donia Friedmann Lutz Mädler Sotiris E. Pratsinis 《Topics in Catalysis》2007,44(4):489-497
A comparative photocatalytic analysis was carried out on TiO2 made in a Flame Spray Pyrolysis (FSP) process and flame-made Degussa P25. Both have similar crystallinity, phase composition,
phase segregation and a non-porous surface. Hence comparison was made based on their difference in specific surface area,
organic adsorption and the amount of OH• generated upon illumination. The photocatalytic activity tests were carried out using
the following series of organic compounds: sucrose, glucose, fructose, maleic acid, glyoxylic acid, oxalic acid, isobutyric
acid, phenol and methanol. FSP-made TiO2 outperformed P25 for saccharides mineralisation, while for phenol and methanol mineralisation P25 was better than FSP-made
TiO2. Similar mineralisation rates were observed for both FSP-made and P25 TiO2 for the mineralisation of carboxylic acids. This shows that the relative performance of the photocatalysts depends on the
type of organic compounds to be degraded. The high surface area and possibly a more efficient interfacial charge transfer
of FSP-made TiO2 provided an efficient pathway for saccharides mineralisation. As for phenol and methanol, the mineralisation rates were higher
when using P25 due to the greater amount of OH• radicals generated by this photocatalyst. The fast mineralisation rates of
carboxylic acids made degradation of these organic compounds to be less affected by the TiO2 photocatalyst properties and conditions tested in this work. 相似文献
197.
Beckham Jean C.; Feldman Michelle E.; Vrana Scott R.; Mozley Susannah L.; Erkanli Alaattin; Clancy Carolina P.; Rose Jed E. 《Canadian Metallurgical Quarterly》2005,13(3):219
Using ambulatory methods for 1 day of monitoring, the authors of this study investigated the association between smoking and situational cues in 63 smokers with posttraumatic stress disorder (PTSD) and 32 smokers without PTSD. Generalized estimating equations contrasted 682 smoking and 444 nonsmoking situations by group status. Smoking was strongly related to craving, positive and negative affect, PTSD symptoms, restlessness, and several situational variables among PTSD smokers. For non-PTSD smokers, the only significant antecedent variables for smoking were craving, drinking coffee, being alone, not being with family, not working, and being around others who were smoking. These results are consistent with previous ambulatory findings regarding mood in smokers but also underscore that, in certain populations, mood and symptom variables may be significantly associated with ad lib smoking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
198.
Greg Andraso James Cowles Rose Colt Jay Patel Michael Campbell 《Journal of Great Lakes research》2011,37(4):738-743
The potential of predators to regulate populations of dreissenid mussels (Dreissena polymorpha and Dreissena rostriformis bugensis) has been addressed since early in the dreissenid invasion of North America. Round gobies (Neogobius melanostomus) larger than approximately 60 mm have been shown to prey extensively on dreissenids, whereas smaller round gobies feed mainly on aquatic insects and crustaceans. We propose that ontogenetic changes in pharyngeal morphology may contribute to this diet shift in round gobies. Pharyngeals of 69 round gobies ranging from 31 to 164 mm total length were investigated using light microscopy and scanning electron microscopy. Areas of lower pharyngeals and pharyngobranchial 2 increased allometrically with fish length. Pharyngeals of round gobies smaller than 50 mm contained narrow (< 0.1 mm diameter) papilliform teeth that are consistent with eating soft-bodied prey. By the time round gobies reached approximately 80 mm in length, pharyngeals contained larger diameter (0.3-0.5 mm) molariform teeth typical of those found in molluscivorous fish. Pharyngeal teeth of the largest round gobies also showed considerable wear. Although changes in pharyngeal morphology may contribute to the previously described diet shift in round gobies as they age, genetic and environmental factors both likely influence pharyngeal remodeling and therefore merit further investigation. 相似文献
199.
Eclesielter Batista Moreira Jair Arrieta Baldovino Juliana Lundgren Rose Ronaldo Luis dos Santos Izzo 《岩石力学与岩土工程学报(英文版)》2019,11(2)
One of the conventional ways to improve the mechanical behavior of soils is to mix them with cementing agents such as cement, lime and fly ash. Recently, introduction to alternative materials or sub-products that can be adopted to improve the soil strength is of paramount importance. Therefore, the present study aims to investigate the effects of porosity (η), dry unit weight (γd) of molding, cement content (C) and porosity/volumetric cement content ratio (η/Civ) or void/cement ratio on the unconfined compressive strength (qu or UCS) of silty soil–roof tile waste (RT) mixtures. Soil samples are molded into four different dry unit weights (i.e. 13 kN/m3, 13.67 kN/m3, 14.33 kN/m3 and 15 kN/m3) using 3%, 6% and 9% cement and 5%, 15% and 30% RT. The results show that with the addition of cement, the strength of the RT–soil mixtures increases in a linear manner. On the other hand, the addition of RT decreases qu of the samples at a constant percentage of cement, and the decrease in porosity can increase qu. A dosage equation is derived from the experimental data using the porosity/volumetric cement content ratio (η/Civ) where the control variables are the moisture content, crushed tile content, cement content and porosity. 相似文献
200.
Fecal indicators such as Escherichia coli and enterococci are used as regulatory tools to monitor water with 24 h cultivation techniques for possible input of sewage or feces and presence of potential enteric pathogens yet their source (human or animal) cannot be determined with routine methods. This critical uncertainty has furthered water pollution science toward new molecular approaches. Members of Bacteroides genus, such as Bacteroides thetaiotaomicron are found to have features that allow their use as alternative fecal indicators and for Microbial Source Tracking (MST). The overall aim of this study was to evaluate the concentration and fate of B. thetaiotaomicron, throughout a wastewater treatment facility and septage treatment facility. A large number of samples were collected and tested for E. coli and enterococci by both cultivation and qPCR assays. B. thetaiotaomicron qPCR equivalent cells (mean: 1.8 × 107/100 mL) were present in significantly higher concentrations than E. coli or enterococci in raw sewage and at the same levels in raw septage. The removal of B. thetaiotaomicron target qPCR signals was similar to E. coli and enterococci DNA during the treatment of these wastes and ranged from 3 to 5 log10 for wastewater and was 7 log10 for the septage. A significant correlation was found between B. thetaiotaomicron marker and each of the conventional indicators throughout the waste treatment process for both raw sewage and septage. A greater variability was found with enterococci when compared to E. coli, and CFU and equivalent cells could be contrasted by various treatment processes to examine removal and inactivation via septage and wastewater treatment. These results are compared and contrasted with other qPCR studies and other targets in wastewater samples providing a view of DNA targets in such environments. 相似文献