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   1647篇
  免费   41篇
电工技术   13篇
化学工业   235篇
金属工艺   36篇
机械仪表   35篇
建筑科学   37篇
矿业工程   2篇
能源动力   26篇
轻工业   219篇
水利工程   20篇
石油天然气   2篇
无线电   211篇
一般工业技术   157篇
冶金工业   498篇
原子能技术   9篇
自动化技术   188篇
  2023年   7篇
  2022年   7篇
  2021年   13篇
  2020年   15篇
  2019年   17篇
  2018年   26篇
  2017年   20篇
  2016年   16篇
  2015年   19篇
  2014年   30篇
  2013年   49篇
  2012年   46篇
  2011年   63篇
  2010年   42篇
  2009年   50篇
  2008年   55篇
  2007年   66篇
  2006年   46篇
  2005年   51篇
  2004年   46篇
  2003年   47篇
  2002年   47篇
  2001年   44篇
  2000年   42篇
  1999年   39篇
  1998年   116篇
  1997年   79篇
  1996年   71篇
  1995年   48篇
  1994年   31篇
  1993年   41篇
  1992年   34篇
  1991年   23篇
  1990年   25篇
  1989年   31篇
  1988年   22篇
  1987年   30篇
  1986年   23篇
  1985年   21篇
  1984年   16篇
  1983年   19篇
  1982年   8篇
  1981年   22篇
  1980年   19篇
  1979年   14篇
  1978年   9篇
  1977年   12篇
  1976年   26篇
  1974年   8篇
  1970年   6篇
排序方式: 共有1688条查询结果,搜索用时 15 毫秒
71.
Abstract

The inhomogeneity of thin films of ZrO2 and TiO2 was reduced by ion beam bombardment with mixed argon and oxygen as a working gas during deposition. The inhomogeneities of the films were calculated from transmission monitoring curves. The optimum ion beam voltage and ion beam current density are 900 V and 12 μA cm?2 for TiO2 film.  相似文献   
72.
Efforts to further extend the range of applications of polymer based materials have resulted in the recent production of healable polymers that can regain their strength after damage. Within this field of healable materials, supramolecular polymers have been subject to extensive investigation. By virtue of their reversible non‐covalent interactions, cracks and fractures in such polymers can be readily and repeatedly healed in order to regain key physical properties. However, many supramolecular polymers are relatively weak and elastomeric in nature, which renders them unsuitable for high strength structural applications. To overcome these deficiencies, preliminary studies have shown that it is possible to reinforce supramolecular polymers with microscale and nanoscale fillers to afford composites that are not only stronger and stiffer compared with the polymers alone but also retain their healing abilities. In this minireview we discuss the evolution of these supramolecular composites and their advantages over more conventional, covalent polymeric materials. © 2014 Society of Chemical Industry  相似文献   
73.
A method is proposed for modeling the self-pressurization of optical fibers that are sealed before drawing. The model is solved numerically and the results compared with experimental results. An explanation of the mechanism is presented and a numerical investigation is undertaken to optimize the choice of experimental parameters to minimize the transient effects of sealed preform drawing.  相似文献   
74.
T15NT was added to a soil of low organic carbon content and composted for 20 days in an aerobic bench scale reactor. The finished whole compost and fulvic acid, humic acid, humin, and lignocellulose fractions extracted from the compost were analyzed by solid-state CP/MAS and DP/MAS 15N NMR. 15N NMR spectra provided direct spectroscopic evidence for reduction of TNT followed by covalent binding of the reduced metabolites to organic matter of the composted soil, with the majority of metabolite found in the lignocellulose fraction, by mass also the major fraction of the compost. In general, the types of bonds formed between soil organic matter and reduced TNT amines in controlled laboratory reactions were observed in the spectra of the whole compost and fractions, confirming that during composting TNT is reduced to amines that form covalent bonds with organic matter through aminohydroquinone, aminoquinone, heterocyclic, and imine linkages, among others. Concentrations of imine nitrogens in the compost spectra suggest that covalent binding by the diamines 2,4DANT and 2,6DANT is a significant process in the transformation of TNT into bound residues. Liquid-phase 15N NMR spectra of the fulvic acid and humin fractions provided possible evidence for involvement of phenoloxidase enzymes in covalent bond formation.  相似文献   
75.
Conducting user-centered design is a primary challenge in ubiquitous computing. Two kinds of prototyping techniques can be particularly effective for developing mobile and ubiquitous computing applications: compound prototypes and situated experience prototypes. Compound prototypes combine the final product's user interface (UI) with a computational implementation that runs on a separate system without the resource constraints of the target device. This model lets researchers and designers evaluate a new application's physicality and aesthetics as well as its functionality. Situated experience prototypes, or paratypes, include experimental protocols that attempt to reproduce user interaction with the system in real situations, and can optionally use common prototyping instruments such as paper mock-ups or physical props. Using our Personal Audio Loop (PAL) project as a case study, we discuss how you can fruitfully employ compound prototypes and paratypes when designing and developing mobile and ubiquitous computing applications.  相似文献   
76.
The software engineering industry undertakes many activities that require generating and using mappings. Companies develop knowledge bases to capture corporate expertise and possibly proprietary information. Software developers build traceability matrices to demonstrate that their designs satisfy the requirements. Proposal managers map customers' statements of work to individual sections of companies' proposals to prove compliance. Systems engineers authoring interface specifications record design rationales as they make relevant decisions. We developed an approach to tracing and mapping that aims to use fully automated information retrieval techniques, and we implemented our approach in a tool called RETRO (requirements tracing on target).  相似文献   
77.
This paper addresses the issues related to improving the overall quality of the dynamic candidate link generation for the requirements tracing process for verification and validation and independent verification and validation analysts. The contribution of the paper is four-fold: we define goals for a tracing tool based on analyst responsibilities in the tracing process, we introduce several new measures for validating that the goals have been satisfied, we implement analyst feedback in the tracing process, and we present a prototype tool that we built, RETRO (REquirements TRacing On-target), to address these goals. We also present the results of a study used to assess RETRO's support of goals and goal elements that can be measured objectively.  相似文献   
78.
Woods Mill Lake is the centrepiece of a nature reserve at Henfield in Sussex, UK. During the last forty years, the lake has undergone a succession of changes, and this has resulted in loss of depth and encroachment of the reed-bed. In the summer months the large carp population was suffering stress due to shallow water. The problem of silt excavation required extensive discussion with statutory agencies: in addition, the work had to be scheduled around nesting birds, breeding newts and school visits. This paper (a) discusses the complexity of the work which was undertaken, and (b) provides an analysis of the fish population which was removed from the lake.  相似文献   
79.
80.
A consensual qualitative research strategy was used to examine data from 127 interviews conducted with 8 psychologists immediately following their sessions of brief therapy with 8 clients. Analyses revealed 3 domains relevant to countertransference: origins (including categories of family issues, needs and values, therapy specific issues, and cultural issues), triggers (including categories of content of client material, therapist comparing client with others, change in therapy structure or procedures, therapist assessing progress of therapy, therapist perception of client, and emotions), and manifestations (including categories of approach, avoidance, negative feelings, and treatment planning). The frequency of categories within and across cases was classified, and relationships among categories from the 3 domains were detected, generating hypotheses for future empirical research. Implications for practice, training, and continued research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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