全文获取类型
收费全文 | 2833篇 |
免费 | 136篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 36篇 |
化学工业 | 825篇 |
金属工艺 | 56篇 |
机械仪表 | 83篇 |
建筑科学 | 91篇 |
矿业工程 | 23篇 |
能源动力 | 87篇 |
轻工业 | 219篇 |
水利工程 | 18篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 288篇 |
一般工业技术 | 536篇 |
冶金工业 | 175篇 |
原子能技术 | 33篇 |
自动化技术 | 502篇 |
出版年
2023年 | 31篇 |
2022年 | 123篇 |
2021年 | 121篇 |
2020年 | 92篇 |
2019年 | 66篇 |
2018年 | 103篇 |
2017年 | 104篇 |
2016年 | 100篇 |
2015年 | 94篇 |
2014年 | 131篇 |
2013年 | 212篇 |
2012年 | 157篇 |
2011年 | 182篇 |
2010年 | 137篇 |
2009年 | 129篇 |
2008年 | 143篇 |
2007年 | 112篇 |
2006年 | 99篇 |
2005年 | 92篇 |
2004年 | 69篇 |
2003年 | 64篇 |
2002年 | 49篇 |
2001年 | 34篇 |
2000年 | 28篇 |
1999年 | 33篇 |
1998年 | 49篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 16篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 25篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 13篇 |
1972年 | 8篇 |
排序方式: 共有2981条查询结果,搜索用时 15 毫秒
61.
Jeremy Rott Eva Teresa Toepfer Maria Bartosova Ana Kolevica Alexander Heuser Michael Rabe Geert Behets Patrick C. DHaese Viktoria Eichwald Manfred Jugold Ivan Damgov Sotirios G. Zarogiannis Rukshana Shroff Anton Eisenhauer Claus Peter Schmitt 《International journal of molecular sciences》2022,23(14)
Serum calcium isotopes (δ44/42Ca) have been suggested as a non-invasive and sensitive Ca balance marker. Quantitative δ44/42Ca changes associated with Ca flux across body compartment barriers relative to the dietary Ca and the correlation of δ44/42CaSerum with bone histology are unknown. We analyzed Ca and δ44/42Ca by mass-spectrometry in rats after two weeks of standard-Ca-diet (0.5%) and after four subsequent weeks of standard- and of low-Ca-diet (0.25%). In animals on a low-Ca-diet net Ca gain was 61 ± 3% and femur Ca content 68 ± 41% of standard-Ca-diet, bone mineralized area per section area was 68 ± 15% compared to standard-Ca-diet. δ44/42Ca was similar in the diets, and decreased in feces and urine and increased in serum in animals on low-Ca-diet. δ44/42CaBone was higher in animals on low-Ca-diet, lower in the diaphysis than the metaphysis and epiphysis, and unaffected by gender. Independent of diet, δ44/42CaBone was similar in the femora and ribs. At the time of sacrifice, δ44/42CaSerum inversely correlated with intestinal Ca uptake and histological bone mineralization markers, but not with Ca content and bone mineral density by µCT. In conclusion, δ44/42CaBone was bone site specific, but mechanical stress and gender independent. Low-Ca-diet induced marked changes in feces, serum and urine δ44/42Ca in growing rats. δ44/42CaSerum inversely correlated with markers of bone mineralization. 相似文献
62.
Oil/Water Separation: Table Salt as a Template to Prepare Reusable Porous PVDF–MWCNT Foam for Separation of Immiscible Oils/Organic Solvents and Corrosive Aqueous Solutions (Adv. Funct. Mater. 41/2017) 下载免费PDF全文
63.
Optimization of the material flow in a manufacturing plant by use of artificial bee colony algorithm
Alejandro Alvarado-Iniesta Jorge L. Garcia-Alcaraz Manuel Ivan Rodriguez-Borbon Aide Maldonado 《Expert systems with applications》2013,40(12):4785-4790
To survive in today’s competitive global market, companies must perform strategic changes in order to increase productivity, eliminating wasted materials, time, and effort. This study will examine how to optimize the time and effort required to supply raw material to different production lines in a manufacturing plant in Juarez, Mexico by minimizing the distance an operator must travel to distribute material from a warehouse to a set of different production lines with corresponding demand. The core focus of this study is similar to that of the Vehicle Routing Problem in that it is treated as a combinatorial optimization problem. The artificial bee colony algorithm is applied in order to find the optimal distribution of material with the aim of establishing a standard time for this duty by examining how this is applied in a local manufacturing plant. Results show that using this approach may be convenient to set standard times in the selected company. 相似文献
64.
Hypermedia systems have been implemented for such a wide range of applications that one must wonder whether their principles should not be included among the building blocks of computer environments themselves. In this paper, we argue that this would indeed be desirable and present a model on which such extension could be based.After a brief review of hypermedia principles and the terminology used in this paper, we give examples of several computer applications in which hypermedia already are or could advantageously be used. We then suggest that most computer applications would greatly benefit if hypermedia were extended from isolated applications to a system-wide facility and that this could substantially simplify implementation of new hypermedia applications. This claim is then generalized and it is shown that extending hypermedia concepts to the organization of the computer environment itself --- the file system --- and to the user interface would make computer environments more flexible and easier to use.We then list the main characteristics of such a ‘hyperenvironment’ and conclude the paper with an outline of its implementation model and an example. 相似文献
65.
Luigi Catuogno Roberto Gassirà Michele Masullo Ivan Visconti 《Information Security Technical Report》2013,17(3):93-104
A smart card is a tamper-resistant miniature computer that performs some basic computations on input a secret information. So far, smart cards have been widely used for securing many digital transactions (e.g., pay television, ATM machines).We focus on the implementation of operating system security services leveraging on smart cards. This very challenging feature allows one to personalize some functionalities of the operating system by simply changing a smart card. Current solutions for integrating smart card features in operating system services require at least a partial execution of some of the operating system functionalities at “user level”. Unfortunately, system functionalities built on top of components lying at both kernel and user levels may negatively affect the overall system security, due to the introduction of multiple points of failure.In this work, we present the design and implementation of SmartK: a framework that integrates features of smart cards uniquely in the Linux kernel. In order to validate our approach, we propose a host of enhancements to the Linux operating system built on top of SmartK: 1) in-kernel clients' authentication with Kerberos; 2) execution of trusted code; 3) key management in secure network filesystems.In particular, we present an experimental Linux OS distribution (SalSA), which addresses the security issues related to downloading packages and to updating an operating system through the Internet. 相似文献
66.
Ivan Rodero David Villegas Norman Bobroff Yanbin Liu Liana Fong S. Masoud Sadjadi 《Journal of Grid Computing》2013,11(2):311-336
The goal of Grid computing is to integrate the usage of computer resources from cooperating partners in the form of Virtual Organizations (VO). One of its key functions is to match jobs to execution resources efficiently. For interoperability between VOs, this matching operation occurs in resource brokering middleware, commonly referred to as the meta-scheduler or meta-broker. In this paper, we present an approach to a meta-scheduler architecture, combining hierarchical and peer-to-peer models for flexibility and extensibility. Interoperability is further promoted through the introduction of a set of protocols, allowing meta-schedulers to maintain sessions and exchange job and resource state using Web Services. Our architecture also incorporates a resource model that enables an efficient resource matching across multiple Virtual Organizations, especially where the compute resources and state are dynamic. Experiments demonstrate these new functional features across three distributed organizations (BSC, FIU, and IBM), that internally use different job scheduling technologies, computing infrastructure and security mechanisms. Performance evaluations through actual system measurements and simulations provide the insights on the architecture’s effectiveness and scalability. 相似文献
67.
Kristopher Page Michael Wilson Nicola J. Mordan Wojciech Chrzanowski Jonathan Knowles Ivan P. Parkin 《Journal of Materials Science》2011,46(19):6355-6363
The adhesion of Staphylococcus aureus was studied using a selection of laboratory-prepared and commercially available coated glass substrates using a simple methodology. Substrates were examined by scanning electron microscopy, atomic force microscopy and water droplet contact angles. It was found that microbial adhesion was independent of surface roughness, when this was of a lower magnitude than microbial size. It was also found that microbial adhesion was greater for hydrophilic surfaces than for hydrophobic ones, but that on a photoinduced superhydrophilic surface, microbes were more spread out—a potential benefit for more effective photocatalytic disinfection. It is suggested that hydrophobic and photoinduced superhydrophilic surface coatings both have potential as a means of reducing microbial fouling of surfaces. 相似文献
68.
Ahmad Ivan Karayan Adi Hersuni Dian Adisty Ardiyansyah Yatim 《Journal of Failure Analysis and Prevention》2011,11(5):481-486
A seawater inlet pipe failed in service. The visual examination showed that the backing bar was present inside the pipe and the failure was characterized by leaks at approximately 4–8 o’clock position near that backing bar. The finite element analysis of fluid in the seawater inlet pipe showed that the eddy zone was formed near the backing bar. The leaks and crater-like surfaces were noticed on the inner pipe surface at which the finite element analysis modeled the possibility of the formation of eddy zone. 相似文献
69.
Mary F. Wheeler Tim Wildey Ivan Yotov 《Computer Methods in Applied Mechanics and Engineering》2011,200(9-12):1251-1262
The aim of this paper is to introduce a new approach to efficiently solve sequences of problems that typically arise when modeling flow in stochastic porous media. The governing equations are based on Darcy’s law with a stochastic permeability field. Starting from a specified covariance relationship, the log permeability is decomposed using a truncated Karhunen–Loève expansion. Multiscale mortar mixed finite element approximations are used in the spatial domain and a nonintrusive sampling method is used in the stochastic dimensions. A multiscale mortar flux basis is computed for a single permeability, called a training permeability, that captures the main characteristics of the porous media, and is used as a preconditioner for each stochastic realization. We prove that the condition number of the preconditioned interface operator is independent of the subdomain mesh size and the mortar mesh size. Computational results confirm that our approach provides an efficient means to quantify the uncertainty for stochastic flow in porous media. 相似文献
70.