全文获取类型
收费全文 | 2754篇 |
免费 | 181篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 36篇 |
化学工业 | 648篇 |
金属工艺 | 36篇 |
机械仪表 | 47篇 |
建筑科学 | 112篇 |
矿业工程 | 2篇 |
能源动力 | 109篇 |
轻工业 | 459篇 |
水利工程 | 21篇 |
石油天然气 | 16篇 |
无线电 | 206篇 |
一般工业技术 | 381篇 |
冶金工业 | 380篇 |
原子能技术 | 18篇 |
自动化技术 | 468篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 45篇 |
2021年 | 86篇 |
2020年 | 67篇 |
2019年 | 78篇 |
2018年 | 75篇 |
2017年 | 89篇 |
2016年 | 102篇 |
2015年 | 84篇 |
2014年 | 126篇 |
2013年 | 209篇 |
2012年 | 185篇 |
2011年 | 183篇 |
2010年 | 153篇 |
2009年 | 151篇 |
2008年 | 135篇 |
2007年 | 139篇 |
2006年 | 85篇 |
2005年 | 91篇 |
2004年 | 78篇 |
2003年 | 71篇 |
2002年 | 51篇 |
2001年 | 43篇 |
2000年 | 47篇 |
1999年 | 35篇 |
1998年 | 138篇 |
1997年 | 95篇 |
1996年 | 54篇 |
1995年 | 37篇 |
1994年 | 30篇 |
1993年 | 40篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 16篇 |
1958年 | 1篇 |
排序方式: 共有2939条查询结果,搜索用时 937 毫秒
21.
Calaza C. Meca E. Marco S. Moreno M. Samitier J. Fonseca L. Gracia I. Cane C. 《IEEE sensors journal》2003,3(5):587-594
A model of a miniaturized non-dispersive infrared (NDIR) gas analysis system, aiming to predict the final system specifications, is presented. It comprises the different elements of the NDIR detector, including a surface micromachined Fabry-Perot tunable filter. These models have been used to estimate the response of the NDIR system to different gas mixtures. Multivariate regression methods like partial least squares allow recovering the true sample composition from the IR absorption spectra measured with the NDIR system, despite the limited selectivity of the filter. Combining model and data processing permits to predict the effect on the final system specification of design parameters. Here, we compare the effect of the technology used for the filter on the system errors. 相似文献
22.
A Ruiz-Bravo M Jimenez-Valera A Sampedro E Moreno 《Canadian Metallurgical Quarterly》1994,9(4):317-324
The survival of Yersinia enterocolitica serotype O9 within mouse peritoneal macrophages was investigated. To evaluate the role of the virulence plasmid in the resistance to intracellular killing, an isogenic pair of virulent (plasmid-bearing) and avirulent (plasmid-less) O9 strains was used. The virulent strain was able to express plasmid-encoded outer membrane proteins and to colonize the Peyer's patches of orally infected mice. When mice were infected intraperitoneally, both strains were recovered at similar rates and over the same time from the peritoneal cavity. When in vitro assays were performed, both strains showed similar resistance to intracellular killing by monolayers of resident and inflammatory peritoneal macrophages. Previous opsonization of bacteria did not modify their survival within macrophage monolayers. We concluded that serotype O9 strains display a chromosome-mediated resistance to intracellular killing by mouse peritoneal macrophages. Moreover, macrophage resistance does not seem to be of importance for virulence of serotype O9 strains in mice. 相似文献
23.
An 18-year time series of monthly NOAA-AVHRR Pathfinder Land burned area was analyzed for the region of tropical Africa, from July 1981 to June 1999. The transition period between NOAA-11 and NOAA-14 platforms from July 1993 to June 1995 was not included due to missing and outlier data. Stability of the time series was addressed for the input variables in the burned area algorithm, reflectance and temperature channels.A Seasonal AutoRegressive Integrated Moving-Average (SARIMA) model was developed for forecasting potential burned area. The SARIMA model identified an autoregressive regular term with 1-month lag and an autoregressive 12-month seasonal term with one season (12 months) component. A cross-correlation between Southern Oscillation Index (SOI) and burned area was statistically significant predictor variable in a time series with 20-month lag. Results show that the SARIMA model with this predictor improved both, fitting and forecasting, residual variance, by 4.1% and 5.6%, respectively, thereby, demonstrating potential relationship between SOI and burned area for the study region. Forecasting was estimated by considering only the first 16 years of the monthly burned area in the time series, from July 1981 to June 1997. The prediction for the following 24 months (from July 1997 to June 1999) was within the 95% confidence level indicating that the forecast was a valid characterization of the modeled process. 相似文献
24.
Response time variability is a new optimization problem with a broad range of applications and a distinctive number of theoretic
flavour. The problem occurs whenever events, jobs, clients or products need to be sequenced so as to minimize the variability
of time for which they wait for the next turn in obtaining the resources necessary for their advance. The problem has numerous
real-life applications. We study its computational complexity, present efficiency, polynomial time algorithms for some cases,
and the NP-hardness proof for a general problem. We propose a position exchange heuristic and apply it to improve the total
response time variability of an initial sequence. The latter is the optimum bottleneck sequence, Webster or Jefferson sequence
of the apportionment, or a random sequence. We report on computational experiments with the heuristic. 相似文献
25.
26.
Vincenzo Augugliaro Vittorio Loddo Ignacio Maldonado Raffaele Molinari 《Solar Energy》2005,79(4):402-408
The photocatalytic oxidation of a common antibiotic, the lincomycin was carried out in aqueous suspensions of polycrystalline TiO2 Degussa P25 irradiated by sunlight. In order to improve the performance of the lincomycin degradation a hybrid system consisting of a solar photoreactor with the photocatalyst in suspension coupled with a membrane module, used to confine both photocatalyst and pollutants in the reaction environment, was tested.A preliminary study was carried out in order to determine some kinetics parameters of the drug photodegradation. The influence of initial substrate concentration on the lincomycin photooxidation rate was investigated. The photooxidation rate follows a pseudo-first order kinetics with respect to the lincomycin concentration under the used experimental conditions. The presence of the membrane reactor allows the catalyst separation and to operate in continuous mode as the membranes rejection for lincomycin and its oxidation products was quite high. 相似文献
27.
P Melgarejo Moreno D Hellín Meseguer C Melgarejo Moreno 《Canadian Metallurgical Quarterly》1998,25(5):471-480
BACKGROUND: Twenty-nine patients with large bulbous and giant aneurysms of the paraclinoid segment of the internal carotid artery (ICA) were operated on, using Dolenc's combined epi- and subdural approach, between 1985 and 1994. Ages ranged from 25 to 79 (83% female; 17% male). METHODS: Proximal control was established in all patients through either an extracranial or petrous carotid exposure. The aneurysm was approached through a wide exposure by removing the anterior clinoid extradural. All but one aneurysm was clipped directly. A saphenous vein graft from the petrous-to-supraclinoid bypass was performed in this remaining case. RESULTS: Surgical morbidity was assessed at 20%. One patient developed a postoperative subdural hematoma and remained severely disabled. Two patients developed permanent third nerve palsy. One patient experienced severe disabling cognitive deficit. One patient died from complications related to a stroke. One patient developed transient diabetes insipidus. Visual outcome, which was assessed separately, was unimproved in 50% of the cases during a follow-up period that averaged 7 years. CONCLUSIONS: With the development of cranial base procedures such as Dolenc's combined epi- and subdural approach, large and giant aneurysms of the paraclinoid segment can be directly clipped with acceptable morbidity, allowing the ICA to remain patent. 相似文献
28.
Ignacio Hernandez Laura Tesoro Rafael Ramirez-Carracedo Javier Diez-Mata Sandra Sanchez Marta Saura Jose Luis Zamorano Carlos Zaragoza Laura Botana 《International journal of molecular sciences》2021,22(6)
In response to cardiac ischemia/reperfusion, proteolysis mediated by extracellular matrix metalloproteinase inducer (EMMPRIN) and its secreted ligand cyclophilin-A (CyPA) significantly contributes to cardiac injury and necrosis. Here, we aimed to investigate if, in addition to the effect on the funny current (I(f)), Ivabradine may also play a role against cardiac necrosis by reducing EMMPRIN/CyPA-mediated cardiac inflammation. In a porcine model of cardiac ischemia/reperfusion (IR), we found that administration of 0.3 mg/kg Ivabradine significantly improved cardiac function and reduced cardiac necrosis by day 7 after IR, detecting a significant increase in cardiac CyPA in the necrotic compared to the risk areas, which was inversely correlated with the levels of circulating CyPA detected in plasma samples from the same subjects. In testing whether Ivabradine may regulate the levels of CyPA, no changes in tissue CyPA were found in healthy pigs treated with 0.3 mg/kg Ivabradine, but interestingly, when analyzing the complex EMMPRIN/CyPA, rather high glycosylated EMMPRIN, which is required for EMMPRIN-mediated matrix metalloproteinase (MMP) activation and increased CyPA bonding to low-glycosylated forms of EMMPRIN were detected by day 7 after IR in pigs treated with Ivabradine. To study the mechanism by which Ivabradine may prevent secretion of CyPA, we first found that Ivabradine was time-dependent in inhibiting co-localization of CyPA with the granule exocytosis marker vesicle-associated membrane protein 1 (VAMP1). However, Ivabradine had no effect on mRNA expression nor in the proteasome and lysosome degradation of CyPA. In conclusion, our results point toward CyPA, its ligand EMMPRIN, and the complex CyPA/EMMPRIN as important targets of Ivabradine in cardiac protection against IR. 相似文献
29.
Luis O. Soto-Rojas B. Berenice Campa-Crdoba Charles R. Harrington Andrs Salas-Casas Mario Hernandes-Alejandro Ignacio Villanueva-Fierro Marely Bravo-Muoz Linda Garcs-Ramírez Fidel De La Cruz-Lpez Miguel ngel Ontiveros-Torres Goar Gevorkian Mar Pacheco-Herrero Jos Luna-Muoz 《International journal of molecular sciences》2021,22(7)
Alzheimer’s disease (AD) is a neurodegenerative disease, characterized histopathologically by intra-neuronal tau-related lesions and by the accumulation of amyloid β-peptide (Aβ) in the brain parenchyma and around cerebral blood vessels. According to the vascular hypothesis of AD, an alteration in the neurovascular unit (NVU) could lead to Aβ vascular accumulation and promote neuronal dysfunction, accelerating neurodegeneration and dementia. To date, the effects of insoluble vascular Aβ deposits on the NVU and the blood–brain barrier (BBB) are unknown. In this study, we analyze different Aβ species and their association with the cells that make up the NVU. We evaluated post-mortem AD brain tissue. Multiple immunofluorescence assays were performed against different species of Aβ and the main elements that constitute the NVU. Our results showed that there are insoluble vascular deposits of both full-length and truncated Aβ species. Besides, insoluble aggregates are associated with a decrease in the phenotype of the cellular components that constitute the NVU and with BBB disruption. This approach could help identify new therapeutic targets against key molecules and receptors in the NVU that can prevent the accumulation of vascular fibrillar Aβ in AD. 相似文献
30.
Ivn Benito Ignacio J. Encío Fermín I. Milagro María Alfaro Ana Martínez-Peuela Miguel Barajas Florencio Marzo 《International journal of molecular sciences》2021,22(9)
Recent studies have suggested that flavonoids such as quercetin and probiotics such as Bifidobacterium bifidum (Bf) and Lactobacillus gasseri (Lg) could play a relevant role in inhibiting colon cancer cell growth. Our study investigated the role of dietary supplementation with microencapsulated probiotics (Bf and Lg) along with quercetin in the development of mouse colorectal cancer (CRC). Methods: Adenomatous polyposis coli/multiple intestinal neoplasia (ApcMin/+) mice were fed a standard diet or the same diet supplemented with microencapsulated probiotics (Bf and Lg strains, 107 CFU/100 g food) or both probiotics strains plus microencapsulated quercetin (15 mg/100 g food) for 73 days. Changes in body and organ weights, energy metabolism, intestinal microbiota, and colon tissue were determined. The expression of genes related to the Wnt pathway was also analyzed in colon samples. Results: Dietary supplementation with microencapsulated probiotics or microencapsulated probiotics plus quercetin reduced body weight loss and intestinal bleeding in ApcMin/+ mice. An improvement in energy expenditure was observed after 8 weeks but not after 10 weeks of treatment. A supplemented diet with microencapsulated Bf and Lg reduced the number of aberrant crypt foci (ACF) and adenomas by 45% and 60%, respectively, whereas the supplementation with Bf, Lg and quercetin decreased the number of ACF and adenomas by 57% and 80%, respectively. Microencapsulated Bf and Lg in combination with quercetin could exert inhibition of the canonical Wnt/β-catenin signaling pathway in the colon of ApcMin/+ mice Conclusions: The administration of microencapsulated Bf and Lg, individually or in combination with quercetin, inhibits the CRC development in ApcMin/+ mice. 相似文献