全文获取类型
收费全文 | 25702篇 |
免费 | 1652篇 |
国内免费 | 50篇 |
专业分类
电工技术 | 317篇 |
综合类 | 60篇 |
化学工业 | 5615篇 |
金属工艺 | 550篇 |
机械仪表 | 590篇 |
建筑科学 | 1062篇 |
矿业工程 | 82篇 |
能源动力 | 799篇 |
轻工业 | 2008篇 |
水利工程 | 213篇 |
石油天然气 | 98篇 |
无线电 | 1953篇 |
一般工业技术 | 5518篇 |
冶金工业 | 3405篇 |
原子能技术 | 208篇 |
自动化技术 | 4926篇 |
出版年
2023年 | 287篇 |
2022年 | 270篇 |
2021年 | 1064篇 |
2020年 | 698篇 |
2019年 | 700篇 |
2018年 | 879篇 |
2017年 | 804篇 |
2016年 | 956篇 |
2015年 | 802篇 |
2014年 | 1115篇 |
2013年 | 1768篇 |
2012年 | 1643篇 |
2011年 | 1927篇 |
2010年 | 1340篇 |
2009年 | 1274篇 |
2008年 | 1333篇 |
2007年 | 1267篇 |
2006年 | 964篇 |
2005年 | 802篇 |
2004年 | 635篇 |
2003年 | 613篇 |
2002年 | 553篇 |
2001年 | 359篇 |
2000年 | 312篇 |
1999年 | 345篇 |
1998年 | 457篇 |
1997年 | 378篇 |
1996年 | 321篇 |
1995年 | 286篇 |
1994年 | 249篇 |
1993年 | 254篇 |
1992年 | 181篇 |
1991年 | 122篇 |
1990年 | 177篇 |
1989年 | 162篇 |
1988年 | 128篇 |
1987年 | 134篇 |
1986年 | 141篇 |
1985年 | 147篇 |
1984年 | 129篇 |
1983年 | 108篇 |
1982年 | 125篇 |
1981年 | 122篇 |
1980年 | 99篇 |
1979年 | 92篇 |
1978年 | 95篇 |
1977年 | 98篇 |
1976年 | 127篇 |
1975年 | 72篇 |
1974年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
2.
Engineering new glass compositions have experienced a sturdy tendency to move forward from (educated) trial-and-error to data- and simulation-driven strategies. In this work, we developed a computer program that combines data-driven predictive models (in this case, neural networks) with a genetic algorithm to design glass compositions with desired combinations of properties. First, we induced predictive models for the glass transition temperature (Tg) using a dataset of 45,302 compositions with 39 different chemical elements, and for the refractive index (nd) using a dataset of 41,225 compositions with 38 different chemical elements. Then, we searched for relevant glass compositions using a genetic algorithm informed by a design trend of glasses having high nd (1.7 or more) and low Tg (500 °C or less). Two candidate compositions suggested by the combined algorithms were selected and produced in the laboratory. These compositions are significantly different from those in the datasets used to induce the predictive models, showing that the used method is indeed capable of exploration. Both glasses met the constraints of the work, which supports the proposed framework. Therefore, this new tool can be immediately used for accelerating the design of new glasses. These results are a stepping stone in the pathway of machine learning-guided design of novel glasses. 相似文献
3.
4.
Alexander Detzner Martin Eigner 《Quality and Reliability Engineering International》2021,37(1):335-351
Manufacturing companies not only strive to deliver flawless products but also monitor product failures in the field to identify potential quality issues. When product failures occur, quality engineers must identify the root cause to improve any affected product and process. This root-cause analysis can be supported by feature selection methods that identify relevant product attributes, such as manufacturing dates with an increased number of product failures. In this paper, we present different methods for feature selection and evaluate their ability to identify relevant product attributes in a root-cause analysis. First, we compile a list of feature selection methods. Then, we summarize the properties of product attributes in warranty case data and discuss these properties regarding the challenges they pose for machine learning algorithms. Next, we simulate datasets of warranty cases, which emulate these product properties. Finally, we compare the feature selection methods based on these simulated datasets. In the end, the univariate filter information gain is determined to be a suitable method for a wide range of applications. The comparison based on simulated data provides a more general result than other publications, which only focus on a single use case. Due to the generic nature of the simulated datasets, the results can be applied to various root-cause analysis processes in different quality management applications and provide a guideline for readers who wish to explore machine learning methods for their analysis of quality data. 相似文献
5.
Elli Ntakou Ralph Masiello Farnaz Farzan Shay Bahramirad Aleksi Paaso M.A. Nayeem Maigha Maigha Daniel Kushner 《The Electricity Journal》2019,32(4):45-49
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal. 相似文献
6.
Ida-Marie Andersson Björn Bergenståhl Marcela Alexander Marie Paulsson Maria Glantz 《International Journal of Food Science & Technology》2021,56(1):480-492
During whey powder production, the feed is subjected to several heat treatments which can cause lactosylation of proteins. In this study, lactosylation of whey proteins was evaluated in spray-dried powders before and after storage by varying the native protein fraction as well as the serum protein/lactose ratio in the powders. The lactosylation of native α-lactalbumin and β-lactoglobulin in the powders before storage was not affected to a large extent by the protein denaturation or if the feed had been heat treated in a high or low lactose environment. After storage (relative humidity of 23.5%, 30 °C, 25 days), the kinetic of lactosylation tended to increase with increasing native protein fraction and bulk protein content in the powders. An explanation could be that proteins dissolved in the lactose glassy structure might have a lower reactivity, while proteins present in the protein glassy structure with dissolved lactose may display higher lactosylation reactivity. 相似文献
7.
Raquel Cano Jos L. Prez Liss Angarita Dvila ngel Ortega Yosselin Gmez Nereida Josefina Valero-Cedeo Heliana Parra Alexander Manzano Teresa Isabel Vliz Castro María P. Díaz Albornoz Gabriel Cano Joselyn Rojas-Quintero Maricarmen Chacín Valmore Bermúdez 《International journal of molecular sciences》2021,22(9)
Non-alcoholic fatty liver disease (NAFLD) is considered the most common liver disorder, affecting around 25% of the population worldwide. It is a complex disease spectrum, closely linked with other conditions such as obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome, which may increase liver-related mortality. In light of this, numerous efforts have been carried out in recent years in order to clarify its pathogenesis and create new prevention strategies. Currently, the essential role of environmental pollutants in NAFLD development is recognized. Particularly, endocrine-disrupting chemicals (EDCs) have a notable influence. EDCs can be classified as natural (phytoestrogens, genistein, and coumestrol) or synthetic, and the latter ones can be further subdivided into industrial (dioxins, polychlorinated biphenyls, and alkylphenols), agricultural (pesticides, insecticides, herbicides, and fungicides), residential (phthalates, polybrominated biphenyls, and bisphenol A), and pharmaceutical (parabens). Several experimental models have proposed a mechanism involving this group of substances with the disruption of hepatic metabolism, which promotes NAFLD. These include an imbalance between lipid influx/efflux in the liver, mitochondrial dysfunction, liver inflammation, and epigenetic reprogramming. It can be concluded that exposure to EDCs might play a crucial role in NAFLD initiation and evolution. However, further investigations supporting these effects in humans are required. 相似文献
8.
Abhendra K. Singh Kaitlyn Kahle Hannah James Allison L. Horner Daniel Villaflor Zach Benedict 《Ceramics International》2021,47(12):17268-17275
In this study the effects of high temperature and moisture on the impact damage resistance and mechanical strength of Nextel 610/alumina silicate ceramic matrix composites were experimentally evaluated. Composite laminates were exposed to either a 1050°C isothermal furnace-based environment for 30 consecutive days at 6 h a day, or 95% relative humidity environment for 13 consecutive days at 67°C. Low velocity impact, tensile and short beam strength tests were performed on both ambient and environmentally conditioned laminates and damage was characterized using a combination of non-destructive and destructive techniques. High temperature and humidity environmental exposure adversely affected the impact resistance of the composite laminates. For all the environments, planar internal damage area was greater than the back side dent area, which in turn was greater than the impactor side dent area. Evidence of environmental embrittlement through a stiffer tensile response was noted for the high temperature exposed laminates while the short beam strength tests showed greater propensity for interlaminar shear failure in the moisture exposed laminates. Destructive evaluations exposed larger, more pronounced delaminations in the environmentally conditioned laminates in comparison to the ambient ones. External damage metrics of the impactor side dent depth and area directly influenced the post-impact tensile strength of the laminates while no such trend between internal damage area and residual strength could be ascertained. 相似文献
9.
Isabel Fernandes Cecília Melo-Alvim Raquel Lopes-Brs Miguel Esperana-Martins Luís Costa 《International journal of molecular sciences》2021,22(2)
Osteosarcoma (OS) is a rare condition with very poor prognosis in a metastatic setting. Basic research has enabled a better understanding of OS pathogenesis and the discovery of new potential therapeutic targets. Phase I and II clinical trials are already ongoing, with some promising results for these patients. This article reviews OS pathogenesis and new potential therapeutic targets. 相似文献
10.