首页 | 官方网站   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   419篇
  免费   20篇
工业技术   439篇
  2023年   6篇
  2022年   5篇
  2021年   11篇
  2020年   10篇
  2019年   15篇
  2018年   8篇
  2017年   12篇
  2016年   11篇
  2015年   8篇
  2014年   15篇
  2013年   25篇
  2012年   33篇
  2011年   38篇
  2010年   30篇
  2009年   26篇
  2008年   18篇
  2007年   24篇
  2006年   23篇
  2005年   12篇
  2004年   13篇
  2003年   11篇
  2002年   14篇
  2001年   5篇
  2000年   2篇
  1999年   5篇
  1998年   5篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1994年   1篇
  1993年   4篇
  1991年   2篇
  1989年   3篇
  1988年   2篇
  1987年   3篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1982年   2篇
  1981年   1篇
  1980年   4篇
  1979年   2篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1972年   2篇
  1969年   1篇
排序方式: 共有439条查询结果,搜索用时 593 毫秒
101.
Understanding and managing groundwater resources require the integration of a large amount of high-quality data from a variety of sources. Due to the limitations in accessing information related to groundwater and subsurface conditions, the gathering of available existing information is of crucial importance when conducting a successful hydrogeological study. Here, we present an approach for the development of an exhaustive and comprehensive groundwater database through (1) the gathering of relevant sources of information relating to groundwater, and (2) the application of a quality control process in order to screen the data for accuracy and quality. This hydrogeological database is then implemented within a GIS (geographic information system) framework coupled to a Relational Database Management System (RDBMS) as a personal geodatabase (ESRI format) GIS technology. Once established, the spatial database allows a user to request the relevant data required for a specific hydrogeological study. In addition, stratigraphic data stored within the spatial database may be utilized for constructing 3D subsurface hydrostructural models. In order to achieve this objective, the software Arc Hydro Groundwater combined with the ArcGIS spatial database is shown to be appropriate for the 3D structural representation of aquifers (groundwater reservoirs). The innovative contribution of this approach in building 3D hydrostructural subsurface models from a spatial database resides in simplifying the required step-by-step processes by considering a unified compatible combination of “RDBMS-ArcGIS-Arc Hydro Groundwater” technologies. The proposed methodology is illustrated using data from an ongoing project aimed at developing an inventory of the groundwater resources of the Saguenay-Lac-Saint-Jean region, Quebec (Canada).  相似文献   
102.
In a two-sample location-scale model with censored data, the logrank test is asymptotically efficient when the error distribution is extreme minimum value. On the other hand, the Wilcoxon test is asymptotically efficient when the error distribution is logistic. We propose a pretest for choosing between logrank and Wilcoxon by determining if the error distribution is closer to extreme minimum value or logistic. This adaptive test is compared with the logrank and Wilcoxon tests through simulation.  相似文献   
103.
The influence of distillation parameters on the extraction of flavour compounds from the gin botanical Juniperus communis L. using vapour infusion was investigated. The optimum mix of conditions to extract the highest levels of certain compounds was established using a 33-factorial design. Quantification using solid-phase microextraction and gas chromatography coupled mass spectrometry, was performed measuring nine common flavour compounds. The greatest influence was the botanical ratio, whilst the least influential parameter was ethanol concentration for all compounds except terpinen-4-ol. Density functional theory calculations of quantitative structure–activity relationship properties for the flavour compounds were also undertaken to test for molecular influence on solvent extraction. The quantitative structure–activity relationship model showed the highest dipole moment for terpinen-4-ol and the lowest for γ-terpinene. © 2020 The Institute of Brewing & Distilling  相似文献   
104.
Photonic Network Communications - The present paper addresses future network architectures considered for Fixed Mobile Convergence, where users can access resources transparently either through...  相似文献   
105.
The possible coexistence of three mycotoxins in rice, including aflatoxin B1 (AFB1), citrinin (CIT) and ochratoxin A (OTA), was investigated. The samples of rice were collected in large markets in five provinces of the central region of Vietnam. These toxins were extracted, purified and finally quantified by HPLC with fluorimetry detection. Contamination of AFB1 was found to be the most, followed by OTA, while contamination of CIT was insignificant. The coexistence of CIT with AFB1/OTA in rice was found in high percentage. Some samples overpassed the authorized limit by Europe in OTA and/or AFB1.  相似文献   
106.
A key property for predicting the effectiveness of stochastic search techniques, including evolutionary algorithms, is the existence of a positive correlation between the form and the quality of candidate solutions. In this paper we show that when the ordering of genomic symbols in a genetic algorithm is completely independent of the fitness function and therefore free to evolve along with the candidate solutions it encodes, the resulting genomes self-organize into self-similar structures that favor this key stochastic search property.  相似文献   
107.
108.
Fiber units are conserved design motifs that bestow intrinsic stiffness to biological tissues. Collagen fibrils are the fundamental unit of fibrous tissues with controlled assembly and multiscale structure‐function properties. Characteristic non‐linear tissue response is afforded through energy dissipation at the stiff‐soft interfaces of fibril collagen and extrafibrillar matrix components. The goal of this research is to develop a 3D silk hydrogel microfiber platform with bioinspired toughening mechanisms. Batch fabrication and post‐processing renders fibers that can be handled and with tunable features, as well as loading of components to improve material responses. Matrix loading of a glycoprotein, bovine serum albumin (BSA), adds a primary defense mechanism to material failure in the form of sacrificial bonds. This enables nano‐ to micro‐scale rearrangement with strain and improved fiber toughness compared to silk‐only fibers. Further biomimicry is added via matrix loading of a biosilica precursor peptide, R5, enabling biomineralization in the form of silicification. Inorganic mineral deposition of Silk‐BSA‐R5 hydrogel microfibers provides a fibrous scaffold for applications that require fibril‐mineral interfaces for load transduction. This microfiber platform introduces a methodology for meticulous fibrous scaffold design with biomimetic fibril hierarchy, toughening mechanisms, and loading capabilities for systematic tissue engineering applications.  相似文献   
109.
110.
The behavior of alumina nano-particles taken from a commercial powder is investigated during in situ compression experiments in a transmission electron microscope (TEM). Small particles of 40 nm in diameter can undergo severe plastic deformation without failure, whereas brittle fracture is observed for 120 nm sized nano-particles. This is evidence of a critical size under which alumina, at least in the form of nano-particles, cannot be considered as brittle materials even at room temperature and a direct observation of the grinding limit generally observed during ball milling.  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-23

京公网安备 11010802026262号