全文获取类型
收费全文 | 4100篇 |
免费 | 217篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 61篇 |
综合类 | 1篇 |
化学工业 | 838篇 |
金属工艺 | 86篇 |
机械仪表 | 71篇 |
建筑科学 | 80篇 |
矿业工程 | 10篇 |
能源动力 | 109篇 |
轻工业 | 494篇 |
水利工程 | 33篇 |
石油天然气 | 14篇 |
无线电 | 235篇 |
一般工业技术 | 504篇 |
冶金工业 | 1394篇 |
原子能技术 | 22篇 |
自动化技术 | 369篇 |
出版年
2024年 | 7篇 |
2023年 | 36篇 |
2022年 | 87篇 |
2021年 | 144篇 |
2020年 | 105篇 |
2019年 | 108篇 |
2018年 | 129篇 |
2017年 | 132篇 |
2016年 | 141篇 |
2015年 | 88篇 |
2014年 | 100篇 |
2013年 | 237篇 |
2012年 | 175篇 |
2011年 | 199篇 |
2010年 | 162篇 |
2009年 | 161篇 |
2008年 | 150篇 |
2007年 | 118篇 |
2006年 | 94篇 |
2005年 | 61篇 |
2004年 | 64篇 |
2003年 | 73篇 |
2002年 | 53篇 |
2001年 | 44篇 |
2000年 | 41篇 |
1999年 | 62篇 |
1998年 | 383篇 |
1997年 | 287篇 |
1996年 | 175篇 |
1995年 | 101篇 |
1994年 | 84篇 |
1993年 | 106篇 |
1992年 | 21篇 |
1991年 | 26篇 |
1990年 | 19篇 |
1989年 | 32篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 17篇 |
1979年 | 5篇 |
1978年 | 12篇 |
1977年 | 55篇 |
1976年 | 92篇 |
1973年 | 3篇 |
排序方式: 共有4321条查询结果,搜索用时 15 毫秒
41.
Costa Albert; Kovacic Damir; Fedorenko Evelina; Caramazza Alfonso 《Canadian Metallurgical Quarterly》2003,29(6):1270
The authors report 3 picture-word interference experiments in which they explore some properties of the agreement process in speech production. In Experiment 1, Croatian speakers were asked to produce utterances in which the noun's gender value had an impact on the selection of gender-marked freestanding morphemes (pronouns) while ignoring the presentation of same- or different-gender distractor words. In Experiments 2 and 3, Croatian speakers were asked to name the same pictures using noun phrases in which the noun's gender value surfaced as an inflectional suffix. Different-gender distractors interfered more than same-gender distractors (the gender congruency effect) in Experiment 1, but not in Experiments 2 and 3. These contrasting results show that the cause of the gender congruency effect is not at the level where lexical-grammatical information is selected but at the level of selection of freestanding morphemes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
42.
43.
LG Falender 《Canadian Metallurgical Quarterly》1995,74(2):16-9; quiz 20
Dental implants are well-established in dentistry and allow the restorative dentist to offer patients the best that dentistry has to offer. Through examination, radiographs, and study models, the restorative dentist and implant surgeon can develop a treatment plan. Comprehensive diagnosis and treatment planning involve much more than a clinical exam--they require an investigation involving past, present and future dental therapy. 相似文献
44.
PURPOSE: The neurologic effect of induced hyperglycemia in the postischemic period was investigated with a rat aortic occlusion model. METHODS: Sprague-Dawley rats weighing 200 to 350 gm were anesthetized, intubated, and ventilated with 1% to 1.5% halothane. Temperature was continuously monitored and maintained at 37 degrees +/- 0.5 degrees C. The chest was opened, the thymus excised, and the aortic arch exposed. Snares were placed around the aorta distal to the left subclavian artery and the right and left subclavian arteries. The three vessels thus isolated were occluded for 8 minutes. With snare release and withdrawal, the rats received an intraperitoneal injection of 5% dextrose in water (2 gm/kg) or an equivalent volume of 0.9% saline solution. In a second group of rats the administration of glucose or saline solution was delayed until 30 minutes after snare release. Blood samples for blood glucose determination were obtained before operation, before occlusion, immediately after occlusion, and 15, 30, 45, 60, and 240 minutes after occlusion. A neurologic deficit score was assigned at 1, 4, 18, and 24 hours after occlusion to quantify hindlimb neurologic deficit based on 15-point scale (0 = normal, 15 = severe deficit). Sham-operated rats received the same operation and injection, but the snares were only manipulated and not made occlusive. RESULTS: The rats that were administered glucose immediately after snare release showed a statistically significant exacerbation of lower extremity neurologic deficit at 24 hours after occlusion (p < or = 0.05, Mann-Whitney U test). The sham-operated rats were normal (0 score) at 24 hours. Significant elevation of blood glucose (321 +/- 33 mg/dl) was seen in the glucose-injected rats at 15 minutes and continued for up to 4 hours after occlusion (p = 0.040 and 0.014, respectively; Student's t test). CONCLUSION: Postischemic hyperglycemia immediately after a standard spinal cord ischemic stress worsens neurologic outcome. 相似文献
45.
F Davodeau MA Peyrat A Necker R Dominici F Blanchard C Leget J Gaschet P Costa Y Jacques A Godard H Vie A Poggi F Romagné M Bonneville 《Canadian Metallurgical Quarterly》1997,158(12):5603-5611
Several studies have demonstrated the existence of a murine NK1.1+ alphabeta T cell subset expressing V alpha14+ TCR alpha-chains with highly conserved invariant junctional sequences and able to secrete Th2 cytokines when exposed to CD1+ stimulator cells. In humans, alphabeta T cells carrying invariant V alpha24+ TCR alpha-chains highly homologous to those expressed by murine NK1.1 cells have been recently described. Here we show that these cells (referred to as V alpha24inv T cells) and murine NK1.1+ alphabeta T cells resemble each other in several ways. First, like their murine counterparts, T cells expressing high levels of V alpha24inv TCRs can be either CD4- CD8- double negative (DN) or CD4+, but they never express heterodimeric CD8 molecules. Second, most V alpha24inv T cells are brightly stained by NKRP1-specific mAb but not by mAb directed against other type II transmembrane proteins of the NK complex. Third, DN and particularly CD4+ V alpha24inv T cells are greatly enriched for IL-4 producers. The concomitant expression of highly conserved TCRs of a particular set of NK markers and of Th2 cytokines in human and murine alphabeta T cells suggests a coordinate acquisition of these phenotypic and functional properties. Furthermore, the relatively high frequency of human V alpha24inv T cells, which are presently shown to represent on average 1/500 PBL, and the high interindividual variations of the size of this cell subset under physiologic conditions go for a major role played by alphabeta T cells carrying invariant TCR in a large array of immune responses. 相似文献
46.
DM Clark PM Salkovskis LG Ost E Breitholtz KA Koehler BE Westling A Jeavons M Gelder 《Canadian Metallurgical Quarterly》1997,65(2):203-213
Cognitive accounts of panic predict that panic disorder patients will be particularly prone to misinterpret autonomic sensations. Several studies have produced results consistent with this prediction, but each is open to alternative interpretation. To clarify matters, 2 studies administered the Body Sensations Interpretation Questionnaire (BSIQ) to panic patients and controls. Panic patients were more likely to interpret ambiguous autonomic sensations as signs of immediately impending physical or mental disaster and were more likely than other anxiety disorder patients and nonpatients to believe these interpretations. In a 3rd study, a brief version of the BSIQ was shown to have satisfactory test-retest reliability, to change with treatment, and to discriminate treatments that varied in their effects on panic. 相似文献
47.
Six measures of divergent thinking were administered to 825 men ranging in age from 17 to 101 over the period from 1959 to 1972; repeat administrations were given to a subset of 278 men after a 6-year interval. Cross-sectional analyses showed curvilinear trends, with an increase in scores for men under 40 and a decline thereafter. Repeated measures analyses on subjects initially aged 33 to 74 generally replicated this finding, whereas cross-sequential analyses suggested a decline for all cohorts tested at a later time. Additional analyses suggested that not all of the decline could be attributed to reduced speed of response production. These longitudinal findings confirm earlier cross-sectional reports of decline in divergent thinking abilities with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
Pursuing optimal solutions for large scale transmission network planning problems is a formidable task due to their combinatorial nature and also due to the nonconvexities involved. Successful approaches using hierarchical Benders decomposition incur in a high computational cost mainly due to the need to solve a large integer program (the investment sub-problem) for every Benders iteration. In this work the authors propose to use heuristics within the decomposition framework, therefore avoiding to solve to optimality each integer sub-problem. The global computational effort is substantially reduced, and allows coping with large problems that would be intractable using classical combinatorial techniques. Case studies with the 6 bus Garver test system and a reduced Southeastern Brazilian power network are presented and discussed 相似文献
49.
S Niermeyer P Yang Shanmina Drolkar J Zhuang LG Moore 《Canadian Metallurgical Quarterly》1995,333(19):1248-1252
BACKGROUND: Reduced oxygen availability at high altitude is associated with increased neonatal and infant mortality. We hypothesized that native Tibetan infants, whose ancestors have inhabited the Himalayan Plateau for approximately 25,000 years, are better able to maintain adequate oxygenation at high altitude than Han infants, whose ancestors moved to Tibet from lowland areas of China after the Chinese military entered Tibet in 1951. METHODS: We compared arterial oxygen saturation, signs of hypoxemia, and other indexes of neonatal wellbeing at birth and during the first four months of life in 15 Tibetan infants and 15 Han infants at 3658 m above sea level in Lhasa, Tibet. The Han mothers had migrated from lowland China about two years previously. A pulse oximeter was placed on each infant's foot to provide measurements of arterial oxygen saturation distal to the ductus arteriosus. RESULTS: The two groups had similar gestational ages (about 38.9 weeks) and Apgar scores. The Han infants had lower birth weights (2773 +/- 92 g) than the Tibetan infants (3067 +/- 107 g), higher concentrations of cord-blood hemoglobin (18.6 +/- 0.8 g per deciliter, vs. 16.7 +/- 0.4 in the Tibetans), and higher hematocrit values (58.5 +/- 2.4 percent, vs. 51.4 +/- 1.2 percent in the Tibetans). In both groups, arterial oxygen saturation was highest in the first two days after birth and was lower when the infants were asleep than when they were awake. Oxygen saturation values were lower in the Han than in the Tibetan infants at all times and under all conditions during all activities. The values declined in the Han infants from 92 +/- 3 percent while they were awake and 90 +/- 5 percent during quiet sleep at birth to 85 +/- 4 percent while awake and 76 +/- 5 percent during quiet sleep at four months of age. In the Tibetan infants, oxygen saturation values averaged 94 +/- 2 percent while they were awake and 94 +/- 3 percent during quiet sleep at birth and 88 +/- 2 percent while awake and 86 +/- 5 percent during quiet sleep at four months. Han infants had clinical signs of hypoxemia--such as cyanosis during sleep and while feeding--more frequently than Tibetans. CONCLUSIONS: In Lhasa, Tibet, we found that Tibetan newborns had higher arterial oxygen saturation at birth and during the first four months of life than Han newborns. Genetic adaptations may permit adequate oxygenation and confer resistance to the syndrome of pulmonary hypertension and right-heart failure (subacute infantile mountain sickness). 相似文献
50.
Dominguez M. Pons-Nin J. Ricart J. Bermejo A. Costa E.F. Morata M. 《IEEE transactions on circuits and systems. I, Regular papers》2005,52(11):2286-2297
The aim of this paper is the analysis, simulation, and experimental verification of the /spl Sigma/-/spl Delta/ pulsed digital oscillator (PDO) topology. As it has been shown in previous works, the oscillation frequency and output spectrum in the PDO depend on the sampling frequency, the natural frequency of the microelectromechanical systems (MEMS) resonator and its damping factor. Here, extensive discrete-time simulations have been carried out which show that the normalized oscillation frequency as a function of the normalized natural frequency of the resonator is very similar to a distorted Devil's Staircase fractal. This nonlinear behavior is a direct consequence of the damping losses of the MEMS resonator. Analytical conditions for a perfect oscillation at the natural frequency of the resonator are also calculated. For this set of what we call "perfect" frequencies, it is also shown that the energy transfer from the electrical to the mechanical domain is maximum. Then a more generalized structure of the oscillator is considered and the drawn conclusions are tested against experimental results obtained from an oscillator prototype which uses a MEMS resonator with thermoelectric actuation and piezoresistive position sensing. 相似文献