首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1830篇
  免费   122篇
  国内免费   3篇
电工技术   31篇
综合类   2篇
化学工业   441篇
金属工艺   20篇
机械仪表   51篇
建筑科学   74篇
矿业工程   1篇
能源动力   69篇
轻工业   224篇
水利工程   19篇
石油天然气   4篇
无线电   185篇
一般工业技术   301篇
冶金工业   204篇
原子能技术   4篇
自动化技术   325篇
  2024年   3篇
  2023年   15篇
  2022年   22篇
  2021年   109篇
  2020年   54篇
  2019年   61篇
  2018年   74篇
  2017年   56篇
  2016年   84篇
  2015年   63篇
  2014年   85篇
  2013年   128篇
  2012年   109篇
  2011年   124篇
  2010年   119篇
  2009年   119篇
  2008年   109篇
  2007年   77篇
  2006年   65篇
  2005年   66篇
  2004年   39篇
  2003年   57篇
  2002年   51篇
  2001年   31篇
  2000年   16篇
  1999年   28篇
  1998年   28篇
  1997年   19篇
  1996年   14篇
  1995年   18篇
  1994年   18篇
  1993年   8篇
  1992年   8篇
  1991年   7篇
  1990年   4篇
  1989年   8篇
  1988年   4篇
  1987年   3篇
  1986年   2篇
  1985年   6篇
  1984年   6篇
  1983年   4篇
  1982年   5篇
  1981年   8篇
  1980年   4篇
  1978年   3篇
  1976年   2篇
  1975年   3篇
  1964年   2篇
  1946年   1篇
排序方式: 共有1955条查询结果,搜索用时 15 毫秒
91.
Silicon oxycarbide (SiOC) fibers with different chemical compositions were successfully fabricated by electrospinning a mixture of polyvinylpyrrolidone (PVP) and commercially available polymethylsilsesquioxane (MK) or polymethylphenylsilsesquioxane (H44) preceramic polymers, followed by cross‐linking and pyrolysis at 1000°C in Argon. The influence of the processing procedure (solvent selection, cross‐linking catalyst and additives) on the morphology of the produced fibers was investigated. For the MK/isopropanol system, the introduction of 20 vol% N,N‐dimethylformamide (DMF) enabled to decrease the diameter of the as‐spun fibers from 2.72 ± 0.12 μm to 1.65 ± 0.09 μm. For the H44/DMF systems, beads‐free fibers were obtained by adding 50 vol% choloroform. After pyrolysis, the resultant SiOC fibers derived from MK and H44 resins possessed uniform morphology, with an average diameter of 0.97 ± 0.07 μm and 1.07 ± 0.08 μm, respectively. Due to their different chemical compositions, the MK‐derived and H44‐derived SiOC ceramic fibers could find different potential applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39836.  相似文献   
92.
Mechanical properties of poly(d,l )lactic acid films enriched with Vitamin E and Vitamin E Acetate (5–40% w/w) were investigated. The addition of both formulations resulted in increased polymer Young's modulus and tensile strength. Human foreskin fibroblasts and murine pre‐osteoblasts were used to assess the biocompatibility of polymers. Pre‐osteoblasts adhesion and proliferation were strongly decreased by Vitamin E, whereas Vitamin E Acetate did not alter cell proliferation. Collagen deposition was lower onto Vitamin E blended polymers than onto native and Vitamin E Acetate blended ones. Fibroblasts adhesion and proliferation were increased by both Vitamin E and Vitamin E Acetate addition. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39970.  相似文献   
93.
Epidemiologic studies indicate that millions of people suffer from recurrent cystitis, a pathology requiring antibiotic prophylaxis and entailing high social costs. Cranberry is a traditional folk remedy for cystitis and, which, in the form of a variety of products and formulations has over several decades undergone extensive evaluation for the management of urinary tract infections (UTI). The aim of this retrospective study is to summarize and review the most relevant and recent preclinical and clinical studies on cranberries for the treatment of UTIs. The scientific literature selected for this review was identified by searches of Medline via PubMed. A variety of recent experimental evidence has shed light on the mechanism underlying the anti-adhesive properties of proanthrocyanidins, their structure–activity relationships, and pharmacokinetics. Analysis of clinical studies and evaluation of the cranberry efficacy/safety ratio in the prevention of UTIs strongly support the use of cranberry in the prophylaxis of recurrent UTIs in young and middle-aged women. However, evidence of its clinical use among other patients remains controversial.  相似文献   
94.
In recent years, a peculiar homelessness policy that goes under the name of ‘Housing First’ has become increasingly popular all over the world. Epitomising a quintessential case of policy-mobility, Housing First can today be considered an heterogeneous assemblage of experiences and approaches that sometimes have little in common with each other. Introducing and commenting upon this heterogeneity, the paper critically analyses why and how Housing First has become a planetary success and what are the issues at stake with its widespread implementation. If recent scholarship published in this journal has granted us a fine understanding of Housing First’s functioning in the US, this paper offers something currently absent from the debate: a nuanced and critical understanding of the ambiguities related to the international success of this policy, with specific references to the challenges associated to its translation in the Italian case.  相似文献   
95.
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   
96.
In this report, we conducted a secondary analysis of the Treatment of SSRI-Resistant Depression in Adolescents (TORDIA) study to explore the impact of specific cognitive–behavioral therapy (CBT) treatment components on outcome. In TORDIA, 334 youths (ages 12 to 18 years) with major depressive disorder who had failed to respond to an adequate course of selective serotonin reuptake inhibitor (SSRI) medication were randomized to a medication switch (either to an alternative SSRI or venlafaxine) with or without 12 weeks of adjunctive CBT. Participants who had more than 9 CBT sessions were 2.5 times more likely to have adequate treatment response than those who had 9 or fewer sessions. CBT participants who received problem-solving and social skills treatment components, controlling for number of sessions and other confounding variables, were 2.3 and 2.6 times, respectively, more likely to have a positive response. These preliminary findings underscore the importance of receiving an adequate number of sessions to attain an adequate clinical response. Finally, social skills and problem solving may be active elements in CBT for adolescent depression and should be considered in treatment by those working with seriously depressed youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
97.
The Nuclear Hydrogen Initiative (NHI) of the U.S. Department of Energy′s Office of Nuclear Energy Science and Technology is supporting an effort to reevaluate thermochemical cycles reported in the literature as having both promising efficiencies and proof-of-concept results. Recognizing that the calculation of efficiencies was not always consistently done or well defined in the literature, we first developed a consistent methodology for reevaluating the candidate thermochemical cycles. This methodology was defined for three levels of maturity in process knowledge. Argonne National Laboratory and a group of universities recalculated the efficiency for each level and identified the most critical R&D necessary to further assess the cycles' potential. This methodology is illustrated with the Cu–Cl in Part I of this series of three papers. Current results of the analyses for all of the cycles are summarized in Part II. Part III contains a more detailed Level 3 analysis for the Cu–Cl cycle.  相似文献   
98.
99.
100.
Multi-objective optimisation problems have seen a large impulse in the last decades. Many new techniques for solving distinct variants of multi-objective problems have been proposed. Production scheduling, as with other operations management fields, is no different. The flowshop problem is among the most widely studied scheduling settings. Recently, the Iterated Greedy methodology for solving the single-objective version of the flowshop problem has produced state-of-the-art results. This paper proposes a new algorithm based on Iterated Greedy technique for solving the multi-objective permutation flowshop problem. This algorithm is characterised by an effective initialisation of the population, management of the Pareto front, and a specially tailored local search, among other things. The proposed multi-objective Iterated Greedy method is shown to outperform other recent approaches in comprehensive computational and statistical tests that comprise a large number of instances with objectives involving makespan, tardiness and flowtime. Lastly, we use a novel graphical tool to compare the performances of stochastic Pareto fronts based on Empirical Attainment Functions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号