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   2214篇
  免费   131篇
  国内免费   4篇
电工技术   28篇
综合类   11篇
化学工业   403篇
金属工艺   49篇
机械仪表   31篇
建筑科学   204篇
矿业工程   7篇
能源动力   72篇
轻工业   203篇
水利工程   25篇
石油天然气   13篇
无线电   179篇
一般工业技术   383篇
冶金工业   210篇
原子能技术   5篇
自动化技术   526篇
  2024年   7篇
  2023年   29篇
  2022年   29篇
  2021年   65篇
  2020年   51篇
  2019年   69篇
  2018年   75篇
  2017年   63篇
  2016年   92篇
  2015年   74篇
  2014年   107篇
  2013年   170篇
  2012年   127篇
  2011年   172篇
  2010年   144篇
  2009年   101篇
  2008年   131篇
  2007年   113篇
  2006年   119篇
  2005年   100篇
  2004年   74篇
  2003年   79篇
  2002年   55篇
  2001年   43篇
  2000年   33篇
  1999年   27篇
  1998年   25篇
  1997年   14篇
  1996年   27篇
  1995年   18篇
  1994年   14篇
  1993年   11篇
  1992年   12篇
  1991年   12篇
  1990年   8篇
  1989年   13篇
  1988年   10篇
  1987年   4篇
  1986年   4篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1980年   5篇
  1978年   3篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有2349条查询结果,搜索用时 15 毫秒
111.
112.
This paper describes the development and fabrication of a modular eddy current micro sensor on a flexible polymer foil. Due to handling purposes during the micro sensor fabrication process the modular eddy current micro sensors are fabricated on a temporary Si substrate. To enable a release of the micro sensors at the end of the fabrication process, initial investigations concentrated on the proof of principle applying a deep reactive-ion etching (DRIE) process to structure the Si wafer. The DRIE process was used to structure Si frames, which serve as carriers for the modular micro sensors. For the evaluation of the fabricated eddy current micro sensors, electrical resistance measurements were accomplished with the integrated anisotropic magneto-resistance (AMR) sensor. The aim of these investigations was to evaluate the influence of the substrate material on the characteristics of the AMR sensor. The electrical output signal of these micro sensors were subsequently compared to electrical resistance measurements of identical AMR sensors fabricated on a Si substrate and served as reference. To prove the capability of the completed eddy current micro sensors, a defect in form of a scratch was created on the surface of a Cu probe and investigated by eddy current testing. The electrical output signal of the eddy current micro sensor was subsequently compared to an optical measurement of the surface profile of this scratch. There is a high correlation between the optical measurements and the signal of the eddy current micro sensor.  相似文献   
113.
In order to describe the time-dependent inelastic behavior of steel structures up to failure, a material model is developed within the framework of thermodynamics considering viscoplastic material behavior, isotropic hardening, softening, and isotropic ductile damage. Since softening and damage lead to localization of deformations, the model is extended by a non-local implicit gradient formulation. An additional gradient equation is formulated for the local damage variable in order to achieve results independent of the finite-element discretization. The approach is verified by 3D-structural analysis of CT-specimens.  相似文献   
114.
Ursodeoxycholic acid (UDCA) is a bile acid with demonstrated anti‐apoptotic activity in both in vitro and in vivo models. However, its utility is hampered by limited aqueous solubility. As such, water‐soluble prodrugs of UDCA could have an advantage over the parent bile acid in indications where intravenous administration might be preferable, such as decreasing damage from stroke or acute kidney injury. Five phosphate prodrugs were synthesized, including one incorporating a novel phosphoryloxymethyl carboxylate (POMC) moiety. These prodrugs were highly water‐soluble, but showed significant differences in chemical stability, with oxymethylphosphate prodrugs being the most unstable. In a series of NMR experiments, the POMC prodrug was bioactivated to UDCA by alkaline phosphatase (AP) faster than a prodrug containing a phosphate directly attached to the alcohol at the 3‐position of UDCA. Both of these prodrugs showed significant anti‐apoptotic activity in a series of in vitro assays, although the POMC prodrug required the addition of AP for activity, while the other compound was active without exogenous AP.  相似文献   
115.
A possible explanation for the enhanced flow in carbon nanotubes is given using a mathematical model that includes a depletion layer with reduced viscosity near the wall. In the limit of large tubes the model predicts no noticeable enhancement. For smaller tubes the model predicts enhancement that increases as the radius decreases. An analogy between the reduced viscosity and slip-length models shows that the term slip-length is misleading and that on surfaces which are smooth at the nanoscale it may be thought of as a length-scale associated with the size of the depletion region and viscosity ratio. The model therefore provides a physical interpretation of the classical Navier slip condition and explains why ‘slip-lengths’ may be greater than the tube radius.  相似文献   
116.
117.
The development and use of a Bayesian Belief Network (BBN) model, within an adaptive management process for the management of water quality in the Mackay Whitsunday region of Queensland, Australia is described. The management goal is firstly to set achievable targets for water quality entering the Great Barrier Reef lagoon from the Mackay Whitsunday natural resource management region and then secondly to define and implement a strategy to achieve these targets. The BBN serves as an adaptive framework that managers and scientists may use to articulate what they know about the managed system. It then provides a tool to guide where, when and what interventions (including research) are most likely to achieve management outcomes. Importantly the BBN provides a platform for collective learning.BBN estimates of total suspended sediment (TSS) loads and event mean concentrations (EMCs) were compared to observed data and results from current best practice models. The BBN estimates were reasonable relative to empirical observations. Example results from the BBN are thereafter used to illustrate the use of the model in estimating the likelihood of exceeding water quality targets with and without proposed actions to improve water quality. Example results are also used to illustrate what spatial or land use elements might contribute most to exceeding water quality targets. Finally key limitations of the tool are discussed and important learnings from the process are highlighted.  相似文献   
118.
Within public health discourse there is growing recognition that the social structures and ecology of neighbourhoods impact on health and wellbeing. A clearer understanding of the pathways through which this influence occurs will inform locality-based interventions to tackle inequalities. In this paper we report on an interview based study with parents of young children living in Massey, a suburban neighbourhood of metropolitan Auckland. Locational access to community resources is comparatively poor in Massey as measured by a community resource accessibility index. The findings provide insights into the impact of such access to services and amenities on neighbourhood social cohesion. We conclude by suggesting planning strategies for strengthening neighbourhood identification and attachment for this population group.  相似文献   
119.
CenterParcs     
CenterParcs is Europe's largest short-break holiday operator. It runs twenty ‘villages’ across Britain and Northern Europe which cater, in all, for over 4 million visitors every year. It dominates its own market sector and has become something of a cultural institution, particularly in Holland where it originated and where around ten per cent of the population still takes a holiday there every year. Since its conception in Holland back in the late 1960s the phenomenon of CenterParcs has become synonymous with the values of the aspirant middle classes. This essay seeks to investigate the architectural and cultural origins of CenterParcs within the context of modern tourism, and to explore its relevance as a (sub)urban template and a mirror of society's relationship to nature.

[The author was the winner of the 2006 RIBA President's Dissertation Medal.]  相似文献   
120.
Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.  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