全文获取类型
收费全文 | 2191篇 |
免费 | 120篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 18篇 |
综合类 | 1篇 |
化学工业 | 496篇 |
金属工艺 | 29篇 |
机械仪表 | 42篇 |
建筑科学 | 154篇 |
矿业工程 | 6篇 |
能源动力 | 101篇 |
轻工业 | 142篇 |
水利工程 | 16篇 |
石油天然气 | 8篇 |
无线电 | 182篇 |
一般工业技术 | 381篇 |
冶金工业 | 280篇 |
原子能技术 | 12篇 |
自动化技术 | 451篇 |
出版年
2023年 | 24篇 |
2022年 | 67篇 |
2021年 | 90篇 |
2020年 | 53篇 |
2019年 | 61篇 |
2018年 | 65篇 |
2017年 | 57篇 |
2016年 | 77篇 |
2015年 | 70篇 |
2014年 | 80篇 |
2013年 | 153篇 |
2012年 | 103篇 |
2011年 | 150篇 |
2010年 | 89篇 |
2009年 | 89篇 |
2008年 | 97篇 |
2007年 | 98篇 |
2006年 | 97篇 |
2005年 | 84篇 |
2004年 | 61篇 |
2003年 | 75篇 |
2002年 | 67篇 |
2001年 | 27篇 |
2000年 | 27篇 |
1999年 | 35篇 |
1998年 | 64篇 |
1997年 | 32篇 |
1996年 | 32篇 |
1995年 | 28篇 |
1994年 | 36篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 19篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 25篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1973年 | 3篇 |
1969年 | 5篇 |
排序方式: 共有2319条查询结果,搜索用时 15 毫秒
81.
Sylvester Inkoom John Sobanjo Adrian Barbu Xufeng Niu 《Structure and Infrastructure Engineering》2019,15(7):940-953
Departments of Transportation regularly evaluate the condition of pavements through visual inspections, nondestructive evaluations, image recognition models and learning algorithms. The above methodologies, though efficient, have drawn attention due to their subjective errors, uncertainties, noise effects and overfitting. To improve on the outcomes of the shallow learning models already used in pavement crack prediction, this paper reports on an investigation of the use of recursive partitioning and artificial neural networks (ANN; deep learning frameworks) in predicting the crack rating of pavements. Explanatory variables such as the average daily traffic and truck factor, roadway functional class, asphalt thickness, and pavement condition time series data are employed in the model formulation. Overall, it is observed that the recursive partitioning (regression tree – R2 > 0.8 and classification tree – R2 > 0.6) and ANN (continuous response – R2 > 0.8 and categorical response – R2 > 0.6) are compelling machine learning models for the prediction of the crack ratings based on their goodness-of-fit statistics, mean absolute deviation (MAD < 0.4) and the root mean square errors (RMSE between 0.30 and 0.65). 相似文献
82.
Chamil Abeykoon Peter J. Martin Adrian L. Kelly Kang Li Elaine C. Brown Phil D. Coates 《Polymer Engineering and Science》2014,54(10):2430-2440
Polymer extrusion is fundamental to the processing of polymeric materials and melt flow temperature homogeneity is a major factor which influences product quality. Undesirable thermal conditions can cause problems such as melt degradation, dimensional instability, weaknesses in mechanical/optical/geometrical properties, and so forth. It has been revealed that melt temperature varies with time and with radial position across the die. However, the majority of polymer processes use only single‐point techniques whose thermal measurements are limited to the single point at which they are fixed. Therefore, it is impossible for such techniques to determine thermal homogeneity across the melt flow. In this work, an extensive investigation was carried out into melt flow thermal behavior of the output of a single extruder with different polymers and screw geometries over a wide range of processing conditions. Melt temperature profiles of the process output were observed using a thermocouple mesh placed in the flow and results confirmed that the melt flow thermal behavior is different at different radial positions. The uniformity of temperature across the melt flow deteriorated considerably with increase in screw rotational speed while it was also shown to be dependent on process settings, screw geometry, and material properties. Moreover, it appears that the effects of the material, machine, and process settings on the quantity and quality of the process output are heavily coupled with each other and this may cause the process to be difficult to predict and variable in nature. POLYM. ENG. SCI., 54:2430–2440, 2014. © 2013 Society of Plastics Engineers 相似文献
83.
Amalia Mesaros Cristina D. Ghitulica Mihaela Popa Raluca Mereu Adriana Popa Traian Petrisor Jr. Mihai Gabor Adrian Ionut Cadis Bogdan S. Vasile 《Ceramics International》2014
Zn1−xCoxO (x==0.05, 0.10, 0.15) nanoparticles have been synthesized by an alternative wet-chemical synthesis route using the SimAdd technique. The as-obtained powders were investigated by FT-IR spectroscopy, X-ray diffraction and thermal analysis correlated with evolved gas analysis (TG–DTA–FT-IR) in order to determine their chemical nature, crystalline structure and to establish the decomposition sequences. The precipitates are generally amorphous, but low-intensity reflection peaks assigned both to the zinc oxalate dihydrate, and zinc hydroxide can be observed in the recorded patterns, indicating that hydroxy-oxalate precipitates were obtained. The structure, morphology and magnetic properties of the thermally treated samples have been investigated by X-ray diffraction, FT-IR, HRTEM, SAED, UV–vis and EPR. XRD studies reveal a hexagonal wurtzite-type structure for all Zn1−xCoxO samples. TEM investigations show particle size between 28 and 37 nm, with spherical and polyhedral shapes and with tendency to form aggregates. The presence of a Co3O4 secondary phase was evidenced by XRD, UV–vis and EPR for the Zn0.85Co0.15O sample. The ferromagnetic behavior of the samples was revealed. The paper highlights that by varying the cobalt concentration it is possible to modulate the structural, morphological, optical and magnetic properties. 相似文献
84.
Kirk A. J. Stephenson Julia Zhu Adrian Dockery Laura Whelan Toms Burke Jacqueline Turner James J. OByrne G. Jane Farrar David J. Keegan 《International journal of molecular sciences》2022,23(2)
Although rare, inherited retinal degenerations (IRDs) are the most common reason for blind registration in the working age population. They are highly genetically heterogeneous (>300 known genetic loci), and confirmation of a molecular diagnosis is a prerequisite for many therapeutic clinical trials and approved treatments. First-tier genetic testing of IRDs with panel-based next-generation sequencing (pNGS) has a diagnostic yield of ≈70–80%, leaving the remaining more challenging cases to be resolved by second-tier testing methods. This study describes the phenotypic reassessment of patients with a negative result from first-tier pNGS and the rationale, outcomes, and cost of second-tier genetic testing approaches. Removing non-IRD cases from consideration and utilizing case-appropriate second-tier genetic testing techniques, we genetically resolved 56% of previously unresolved pedigrees, bringing the overall resolve rate to 92% (388/423). At present, pNGS remains the most cost-effective first-tier approach for the molecular assessment of diverse IRD populations Second-tier genetic testing should be guided by clinical (i.e., reassessment, multimodal imaging, electrophysiology), and genetic (i.e., single alleles in autosomal recessive disease) indications to achieve a genetic diagnosis in the most cost-effective manner. 相似文献
85.
Flaviu Tma Rodica Blaa Doina Manu Gabriel Gyorki Rare Chinezu Corina Tma Adrian Blaa 《International journal of molecular sciences》2022,23(3)
Brain metastases represent more than 50% of all cerebral tumors encountered in clinical practice. Recently, there has been increased interest in the study of extracellular vesicles, and the knowledge about exosomes is constantly expanding. Exosomes are drivers for organotropic metastatic spread, playing important roles in the brain metastatic process by increasing the permeability of the blood–brain barrier and preparing the premetastatic niche. The promising results of the latest experimental studies raise the possibility of one day using exosomes for liquid biopsies or as drug carriers, contributing to early diagnosis and improving the efficacy of chemotherapy in patients with brain metastases. In this review, we attempted to summarize the latest knowledge about the role of exosomes in the brain metastatic process and future research directions for the use of exosomes in patients suffering from brain metastatic disease. 相似文献
86.
Leon Wehrhan Prof. Dr. Alexander Hillisch Dr. Stefan Mundt Dr. Adrian Tersteegen Dr. Katharina Meier 《ChemMedChem》2020,15(21):2010-2018
Target druggability assessment is an integral part of the early target characterization and selection process in pharmaceutical industry. Here, we investigate a set of five different serine proteases from the blood coagulation cascade. The aim of this study is twofold. Firstly, leveraging the wealth of available in-house high-throughput screening (HTS) data, we analyze HTS hit rates and discuss their predictive value for the development of small molecule (SMOL) candidates. Purely structure-activity relationship (SAR) based druggability ratings are compared with computational protein-structure based druggability assessments. Secondly, we evaluate the impact of using conformational ensembles from molecular dynamics (MD) simulations instead of single static crystal structures as basis for computational druggability assessments. Based on this study, we recommend incorporating molecular dynamics routinely into the early target characterization process, especially if only a single X-ray structure is available. 相似文献
87.
Wind energy systems have been considered for Canada's remote communities in order to reduce their costs and dependence on diesel fuel to generate electricity. Given the high capital costs, low-penetration wind–diesel systems have been typically found not to be economic. High-penetration wind–diesel systems have the benefit of increased economies of scale, and displacing significant amounts of diesel fuel, but have the disadvantage of not being able to capture all of the electricity that is generated when the wind turbines operate at rated capacity.Two representative models of typical remote Canadian communities were created using HOMER, an NREL micro-power simulator to model how a generic energy storage system could help improve the economics of a high-penetration wind–diesel system. Key variables that affect the optimum system are average annual wind speed, cost of diesel fuel, installed cost of storage and a storage systems overall efficiency. At an avoided cost of diesel fuel of 0.30 $Cdn/kWh and current installed costs, wind generators are suitable in remote Canadian communities only when an average annual wind speed of at least 6.0 m/s is present. Wind energy storage systems become viable to consider when average annual wind speeds approach 7.0 m/s, if the installed cost of the storage system is less than 1000 $Cdn/kW and it is capable of achieving at least a 75% overall energy conversion efficiency. In such cases, energy storage system can enable an additional 50% of electricity from wind turbines to be delivered. 相似文献
88.
Illicit drug consumption estimations derived from wastewater analysis: A critical review 总被引:1,自引:0,他引:1
Alexander L.N. van NuijsSara Castiglioni Isabela TarcomnicuCristina Postigo Miren Lopez de AldaHugo Neels Ettore ZuccatoDamia Barcelo Adrian Covaci 《The Science of the total environment》2011,409(19):3564-3577
The consumption of illicit drugs causes indisputable societal and economic damage. Therefore it is necessary to know their usage levels and trends for undertaking targeted actions to reduce their use. Recently, a new approach (namely sewage epidemiology) was developed for the estimation of illicit drug use based on measurements of urinary excreted illicit drugs and their metabolites in untreated wastewater. This review aims at critically evaluating the published literature and identifying research gaps of sewage epidemiology. Firstly, the existing analytical procedures for the determination of the four most used classes of illicit drugs worldwide (cannabis, cocaine, opiates and amphetamine-like stimulants) and their metabolites in wastewater are summarized and discussed. The focus lies on the sample preparation and on the analysis with chromatographic techniques coupled to mass spectrometry. Secondly, back-calculations used to transform measured concentrations in wastewater (in ng/L) into an amount of used illicit drug (in g/day per 1000 inhabitants or doses/day per 1000 inhabitants) are discussed in detail for the four groups of illicit drugs. Sewage epidemiology data from Spain, Belgium, UK, Italy, Switzerland and USA are summarized and compared with data from international organisations, such as the European Monitoring Centre for Drug and Drug Addiction (EMCDDA) and the United Nations Office on Drugs and Crime (UNODC). The results derived from wastewater analysis show in general good agreement with existing prevalence data (percentage of a population that uses illicit drugs at a given time) and demonstrate the potential of sewage epidemiology. However, this review confirms that future work should focus on further optimisation and standardisation of various important parameters (e.g. sample collection and back-calculations). In the future, sewage epidemiology could be used in routine drug monitoring campaigns as a valuable tool in addition to the classical socio-epidemiological studies for the determination of local, national and international illicit drug use. 相似文献
89.
一种城市主义的批判性实践不应执着于不相干的美学自主性,而应着眼于作为当代城市化主要征象的四种空间类型:位于城市与农村之间界定模糊区域的工厂区;纵横全国的基础设施管线和网络;新型文化聚落、邻里和建筑物;来自农村而在城市工作的新城市主体所形成的心理与社会网络。 相似文献
90.
Piotr Długosz Angelika Rączka Adrian Kopeć Rudolf Krzyżak Paweł Darłak Marek Hebda 《Journal of Materials Engineering and Performance》2016,25(6):2261-2266
This paper presents novel opportunities for management of fly ash by synthesizing the material into cordierite ceramics and using it as a reinforcing phase for light metal alloys. Metal matrix composites (based on magnesium alloy and aluminum alloy) were produced by squeeze casting. The magnesium matrix composites with a suitably selected reinforcing phase content (2 wt.%) exhibited much better strength properties than the unmodified alloy (AM60). It was also demonstrated that the wettability (or the lack thereof) in the metal-ceramic system is critical to successful production of the composites based on the AK7 alloy with cordierite. Light alloy matrix composites reinforced with cordierite ceramics particles are innovative materials that combine high strength with low weight, which may be a key factor of merit for numerous applications of the composite in various branches of industries. 相似文献