全文获取类型
收费全文 | 1924篇 |
免费 | 43篇 |
学科分类
工业技术 | 1967篇 |
出版年
2022年 | 8篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 23篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 28篇 |
2014年 | 35篇 |
2013年 | 110篇 |
2012年 | 65篇 |
2011年 | 85篇 |
2010年 | 54篇 |
2009年 | 79篇 |
2008年 | 75篇 |
2007年 | 70篇 |
2006年 | 81篇 |
2005年 | 83篇 |
2004年 | 67篇 |
2003年 | 59篇 |
2002年 | 58篇 |
2001年 | 47篇 |
2000年 | 41篇 |
1999年 | 39篇 |
1998年 | 93篇 |
1997年 | 77篇 |
1996年 | 55篇 |
1995年 | 38篇 |
1994年 | 42篇 |
1993年 | 43篇 |
1992年 | 34篇 |
1991年 | 13篇 |
1990年 | 34篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 19篇 |
1986年 | 18篇 |
1985年 | 28篇 |
1984年 | 27篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 13篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1976年 | 28篇 |
1975年 | 11篇 |
1974年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有1967条查询结果,搜索用时 31 毫秒
41.
M Jaffar SA Everett MA Naylor SG Moore S Ulhaq KB Patel MR Stratford J Nolan P Wardman IJ Stratford 《Canadian Metallurgical Quarterly》1999,9(1):113-118
We report the cases of three patients with anorexia nervosa (AN) who each recovered rapidly after experiencing a life-threatening episode with severe thrombocytopenia. All three cases were the typical restricting-type of AN, occurring in adolescence. They refused to be admitted to a hospital until their general condition had been severely deteriorated. Their lowest platelet counts were 2.9, 4.6, and 2.3 x 10(4)/mm3, respectively. Apparent hemorrhagic tendencies, such as purpura, gingival and nasal bleeding, and gastrointestinal bleeding were observed. The bone marrow examination showed apparent hypoplasia in two patients. No evidence of disseminated intravascular coagulation or autoantibody to platelets was detected. The platelet counts recovered rapidly by water and nutritional supplementation. The recovery from the AN itself was excellent in all three patients without specific psychotherapy. 相似文献
42.
Action as a Fast and Frugal Heuristic 总被引:2,自引:2,他引:0
Decision making is usually viewed as involving a period of thought, while the decision maker assesses options, their likely consequences, and his or her preferences, and selects the preferred option. The process ends in a terminating action. In this view errors of thought will inevitably show up as errors of action; costs of thinking are to be balanced against costs of decision errors. Fast and frugal heuristics research has shown that, in some environments, modest thought can lead to excellent action. In this paper we extend this work to situations in which action is taken after little or no thought. We show that these `highly active' or `decision cycles' processes can lead to excellent results at the cost of almost no thought. The paper examines the settings in which this effectiveness is possible, and lists a number of environmental features that are required for decision cycles to work well. Several research directions for analytical, laboratory, and field-based research are identified. 相似文献
43.
Introduces the new Student Editorial Board for School Psychology Quarterly. Along with the Research Design and Methodology Section and the Book Review Section, which made their inaugural appearance in the Winter 1998 issue, the Student Editorial Board is intended to strengthen both our journal and our field as we move into the next century. It is expected that the Student Editorial Board will result in symbiotic benefits for both our field and the board members themselves. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
Stout Julie C.; Bondi Mark W.; Jernigan Terry L.; Archibald Sarah L.; Delis Dean C.; Salmon David P. 《Canadian Metallurgical Quarterly》1999,13(2):188
Twenty-seven research participants with dementia of the Alzheimer type were studied with the California Verbal Learning Test (D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 1987) and standardized volume measures of the mesial temporal cortical gray matter, neocortical gray matter, thalamus, and caudate nuclei, from magnetic resonance imaging. A pattern of atrophic brain changes in the mesial temporal lobes (MTL) and the thalamus, with relatively less severe atrophy in the neocortical gray matter, was associated with poorer learning of the word list. Similar patterns of brain atrophy were observed for measures of delayed recall and recognition hits. However, for delayed recall, neither contribution was statistically significant, and for recognition hits, MTL was only at the trend level for significance. These results provide evidence that the verbal memory deficit of Alzheimer's disease (AD) is associated not only with the mesial temporal limbic cortex, thought to be the site of earliest and most severe pathology in AD, but also with damage in the thalamus. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Many accounting and finance problems require ordinal multi-state classification decisions, (e.g., control risk, bond rating, financial distress, etc.), yet few decision support systems are available to aid decision makers in such tasks. In this study, we develop a Neural Network based decision support system (NN-DSS) to classify firms in four ordinal states of financial condition namely healthy, dividend reduction, debt default and bankrupt. The classification results of the NN-DSS model are compared with those of a Naïve model, a Multiple Discriminant Analysis (MDA) model, and an Ordinal Logistic Regression (OLGR) model. Four different evaluation criteria are used to compare the models, namely, simple classification accuracy, distance-weighted classification accuracy, expected cost of misclassification (ECM) and ranked probability score. Our study shows that NN-DSS models perform significantly better than the Naïve, MDA, and OLGR models on the ECM criteria, and provide better results than MDA and OLGR on other criteria, although not always significantly better. The effect of the proportion of firms of each state in the training set is also studied. A balanced training set leads to more uniform (less skewed) classification across all four states, whereas an unbalanced training set biases the classification results in favor of the state with the largest number of observations. 相似文献
46.
Grounding spatial language in perception: An empirical and computational investigation. 总被引:1,自引:0,他引:1
The present paper grounds the linguistic categorization of space in aspects of visual perception; specifically, the structure of projective spatial terms such as above are grounded in the process of attention and in vector-sum coding of overall direction. This is formalized in the attentional vector-sum (AVS) model. This computational model accurately predicts linguistic acceptability judgments for spatial terms, under a variety of spatial configurations. In 7 experiments, the predictions of the AVS model are tested against those of 3 competing models. The results support the AVS model and disconfirm its competitors. The authors conclude that the structure of linguistic spatial categories can be partially explained in terms of independently motivated perceptual processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
47.
Shrilatha Balakrishna Jordy Saravia Paul Thevenot Terry Ahlert Slawo Lominiki Barry Dellinger Stephania A Cormier 《Particle and fibre toxicology》2011,8(1):11
Background
Increased asthma risk/exacerbation in children and infants is associated with exposure to elevated levels of ultrafine particulate matter (PM). The presence of a newly realized class of pollutants, environmentally persistent free radicals (EPFRs), in PM from combustion sources suggests a potentially unrecognized risk factor for the development and/or exacerbation of asthma. 相似文献48.
Terry A. Egerton 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(8):1024-1031
BACKGROUND: This paper examines TiO2 photoelectrocatalysis (PEC), a process that increases the efficiency of TiO2 photocatalysis (PC) by applying a potential to separate the UV‐generated charge carriers whose recombination typically limits photonic efficiencies of conventional photocatalysis. RESULTS: Four representative photoelectrocatalytic reactions, nitrophenol oxidation, oxalate degradation, E. coli inactivation and dye decolouration were considered. For all four, a small applied potential raised the rate of pollutant removal by TiO2 electrodes. Because the improvements were probably insufficient to make PEC technologically viable except in niche applications, rates of pollutant removal by PEC and by PC using TiO2 particle dispersions were directly compared. PEC rates were not significantly larger than rates of PC by dispersions. CONCLUSION: Discussions of the implications of these conclusions focus on whether PEC is currently limited by reactor design (irradiation geometry, or mass transfer) or by electrode materials. It is inferred that the performance of present electrodes is not limited significantly by mass transfer constraints. Since the choice of electrode materials (sol–gel or thermal electrodes) has been shown to influence PEC efficiency, recent results on titania nanotubes (TNT) are reviewed. It is concluded that the enhancement factors—the PEC:PC ratio—of TNT electrodes are no higher than those of conventional materials. Copyright © 2011 Society of Chemical Industry 相似文献
49.
Shanshan Liu Daniel Olive Jeff Terry Carlo U. Segre 《Journal of Nuclear Materials》2009,392(2):259-263
The corrosion of fuel cladding and structural materials by lead and lead-bismuth eutectic in the liquid state at elevated temperatures is an issue that must be considered when designing advanced nuclear systems and high-power spallation neutron targets. In this work, lead corrosion studies of molybdenum were performed to investigate the interaction layer as a function of temperature by X-ray absorption spectroscopy. In situ X-ray absorption measurements on a Mo substrate with a 3-6 μm layer of Pb deposited by thermal evaporation were performed at temperatures up to 900 °C and at a 15° angle to the incident X-rays. The changes in the local atomic structure of the corrosion layer are visible in the difference extended X-ray absorption fine structure and the linear combination fitting of the X-ray absorption near-edge structure to as-deposited molybdenum sample and molybdenum oxide (MoO2 and MoO3) standards. The data are consistent with the appearance of MoO3 in an intermediate temperature range (650-800 °C) and the more stable MoO2 phase dominating at high and low temperatures. 相似文献
50.
Hem Joshi Bryan R. Moser Shailesh N. Shah Anurag Mandalika Terry Walker 《European Journal of Lipid Science and Technology》2010,112(7):802-809
The low temperature operability and oxidative stability of cottonseed oil methyl esters (CSME) were improved with four anti‐gel additives as well as one antioxidant additive, gossypol. Low temperature operability and oxidative stability of CSME was determined by cloud point (CP), pour point (PP), cold filter plugging point (CFPP), and oxidative stability index (OSI). The most significant reductions in CP, PP, and CFPP in all cases were obtained with Technol®, with the average reduction in temperature found to be 3.9 °C. Gunk®, Heet®, and Howe's® were progressively less effective, as indicated by average reductions in temperature of 3.4, 3.0, and 2.8 °C, respectively. In all cases, the magnitude of CFPP reduction was greater than for PP and especially CP. Addition of gossypol, a polyphenolic aldehyde, resulted in linear improvement in OSI (R2 = 0.9804). The OSI of CSME increased from 5.0 to 8.3 h with gossypol at a concentration of 1000 ppm. 相似文献