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   497篇
  免费   14篇
  国内免费   218篇
电工技术   4篇
综合类   15篇
化学工业   34篇
金属工艺   12篇
机械仪表   11篇
建筑科学   17篇
矿业工程   2篇
能源动力   17篇
轻工业   13篇
石油天然气   6篇
无线电   64篇
一般工业技术   25篇
冶金工业   4篇
原子能技术   388篇
自动化技术   117篇
  2024年   1篇
  2022年   8篇
  2021年   13篇
  2020年   9篇
  2019年   9篇
  2018年   15篇
  2017年   13篇
  2016年   16篇
  2015年   10篇
  2014年   19篇
  2013年   25篇
  2012年   29篇
  2011年   52篇
  2010年   40篇
  2009年   35篇
  2008年   34篇
  2007年   43篇
  2006年   46篇
  2005年   33篇
  2004年   34篇
  2003年   33篇
  2002年   34篇
  2001年   22篇
  2000年   26篇
  1999年   34篇
  1998年   9篇
  1997年   9篇
  1996年   6篇
  1995年   8篇
  1994年   7篇
  1993年   8篇
  1992年   12篇
  1991年   9篇
  1990年   9篇
  1989年   1篇
  1988年   1篇
  1987年   5篇
  1986年   5篇
  1985年   2篇
  1984年   3篇
  1983年   1篇
  1980年   1篇
排序方式: 共有729条查询结果,搜索用时 15 毫秒
1.
Radionuclide imaging of HER2 expression in tumours may enable stratification of patients with breast, ovarian, and gastroesophageal cancers for HER2-targeting therapies. A first-generation HER2-binding affibody molecule [99mTc]Tc-ZHER2:V2 demonstrated favorable imaging properties in preclinical studies. Thereafter, the affibody scaffold has been extensively modified, which increased its melting point, improved storage stability, and increased hydrophilicity of the surface. In this study, a second-generation affibody molecule (designated ZHER2:41071) with a new improved scaffold has been prepared and characterized. HER2-binding, biodistribution, and tumour-targeting properties of [99mTc]Tc-labelled ZHER2:41071 were investigated. These properties were compared with properties of the first-generation affibody molecules, [99mTc]Tc-ZHER2:V2 and [99mTc]Tc-ZHER2:2395. [99mTc]Tc-ZHER2:41071 bound specifically to HER2 expressing cells with an affinity of 58 ± 2 pM. The renal uptake for [99mTc]Tc-ZHER2:41071 and [99mTc]Tc-ZHER2:V2 was 25–30 fold lower when compared with [99mTc]Tc-ZHER2:2395. The uptake in tumour and kidney for [99mTc]Tc-ZHER2:41071 and [99mTc]Tc-ZHER2:V2 in SKOV-3 xenografts was similar. In conclusion, an extensive re-engineering of the scaffold did not compromise imaging properties of the affibody molecule labelled with 99mTc using a GGGC chelator. The new probe, [99mTc]Tc-ZHER2:41071 provided the best tumour-to-blood ratio compared to HER2-imaging probes for single photon emission computed tomography (SPECT) described in the literature so far. [99mTc]Tc-ZHER2:41071 is a promising candidate for further clinical translation studies.  相似文献   
2.
The aim of this study is to describe the development and application of a web-based decision support tool (ViRTUE) for performing climate risk evaluations of water supply systems. The tool is designed for small-scale water utilities in the northeastern United States that may lack the resources for detailed climate change risk investigations. Development of this tool demonstrates a relatively new approach to web application development using the Shiny framework for the R programming language to create an interactive environment for stakeholders and water managers to explore climate vulnerabilities. Using a decision-scaling framework, the tool allows the user to perform a climate stress test to evaluate the performance and vulnerability to water supply shortfalls of local reservoir systems over a wide range of potential climate change scenarios using a generic systems model. Probabilities of future climate conditions derived from climate projections then help inform utility operators of impending risk.  相似文献   
3.
The direct Z-scheme photocatalysts for overall water decomposition have aroused much concern on account of their strong redox ability and efficient separation of photogenerated electron-hole pairs. In the present work, we have constructed the two dimensional (2D) van der Waals (vdW) MoSe2/SnS2 heterojunction and investigated its electronical and optical properties by applying hybrid functional calculations. The calculated band structures have implied that the MoSe2/SnS2 heterostructure as a direct Z-scheme photocatalyst can make the best of visible light. The induced built-in electric field can effectively improve the separation efficiency of the photoinduced carriers. Moreover, compared with the MoSe2 and SnS2 monolayers, the absorption intensity of MoSe2/SnS2 heterojunction is reinforced in the visible light range. Therefore, MoSe2/SnS2 nanocomposite shows a bright application prospect as a direct Z-scheme visible-light-driven photocatalyst for overall water splitting.  相似文献   
4.
将具有肿瘤靶向性的精氨酸-精氨酸-亮氨酸(RRL)多肽与双功能螯合剂MAG3相连,摸索其螯合99Tcm的适宜标记条件并评价探针的体外稳定性。标记利用SnCl2还原法进行99Tcm标记,对影响标记的主要变量因素分别进行探究以获得适宜标记条件,采用纸层析法测定标记率和放射化学纯度。实验所得MAG3-RRL纯度为98.94%,适宜标记条件下,标记率为93.67%±1.10%,纯化后放射化学纯度为94.32%±0.19%(n=3)。99Tcm-MAG3-RRL在生理盐水和50%牛血清白蛋白(BSA)中放置,6 h内放射化学纯度均大于90%(n=3),在半胱氨酸溶液中的最高置换率为0.57%±0.21%,生理盐水对照为0.41%±0.04%(n=3,P>0.05)。99Tcm-MAG3-RRL的脂水分配系数为lg P=-0.15±0.01(n=3)。结果表明:MAG3可成功连接RRL多肽,并能进一步提高标记率;探针制备方法简单快速,体外稳定性好,为进一步的生物学实验提供了良好的基础。  相似文献   
5.
Image super-resolution using self-optimizing mask via fractional-order gradient interpolation and reconstruction aims to recover detailed information from low-resolution images and reconstruct them into high-resolution images. Due to the limited amount of data and information retrieved from low-resolution images, it is difficult to restore clear, artifact-free images, while still preserving enough structure of the image such as the texture. This paper presents a new single image super-resolution method which is based on adaptive fractional-order gradient interpolation and reconstruction. The interpolated image gradient via optimal fractional-order gradient is first constructed according to the image similarity and afterwards the minimum energy function is employed to reconstruct the final high-resolution image. Fractional-order gradient based interpolation methods provide an additional degree of freedom which helps optimize the implementation quality due to the fact that an extra free parameter α-order is being used. The proposed method is able to produce a rich texture detail while still being able to maintain structural similarity even under large zoom conditions. Experimental results show that the proposed method performs better than current single image super-resolution techniques.  相似文献   
6.
7.
The pressure-time method is classified as a primary method for measuring discharge in hydraulic machinery. The uncertainty in the discharge determined using the pressure-time method is typically around ±1.5 %; however, despite dating back almost one hundred years in time, there still exists potential to reduce this uncertainty. In this paper, an improvement of the pressure-time method is suggested by implementing a novel formulation to model the frictional losses arising in the evaluation procedure. By analyzing previously obtained data from CFD, laboratory and full-scale pressure-time measurements it is shown that the new friction model improves the accuracy of the flow rate calculation by approximately 0.1–0.2% points, compared to currently utilized friction models. Despite being a small absolute improvement, the new friction model presents an important development of the pressure-time method because the relative improvement is significant.  相似文献   
8.
周赛  李龙  刘宜树 《同位素》2019,32(3):171-177
与裂变型99Mo-99mTc发生器相比,凝胶型99Mo-99mTc发生器制备99mTc具有工艺简单、产生的放射性废物容易处理、对环境影响小等优点。本文主要论述了凝胶型99Mo-99mTc发生器与裂变型99Mo-99mTc发生器的区别,堆照生产99Mo原料和凝胶材料的研究进展,凝胶结构以及凝胶组分等多种条件因素对凝胶型99Mo-99mTc发生器性能的影响等,并对低比活度99Mo生产99mTc的研究进展进行综述。  相似文献   
9.
Urban development has an important influence on the energy consumption of transportation. To develop public transportation is one of the important ways to decrease the energy consumption of urban transportation. It is very urgent to upgrade technology to reduce the energy consumption and emissions of the vehicles constantly. The popularization of hydrogen fuel cell vehicles is the trend of the future automobile industry, which can effectively reduce traffic energy consumption and alleviate urban pollution. This article analyzes the impact of urban development on public transport and private transportation energy consumption from 2013 to 2015; and uses hydrogen fuel cell vehicles alternatives in urban public transport as a scenario. It shows that urban economic development can effectively reduce public transport. Population growth will increase greatly energy consumption of public transport, while larger cities with reasonable spatial density can reduce traffic energy consumption. Moreover, hydrogen fuel cell vehicles can effectively reduce the energy consumption and pollution emissions of urban transportation during operating. Based on the above conclusions, this article will eventually provide targeted recommendations for the development of Chinese cities, public transport, and hydrogen fuel cell vehicles.  相似文献   
10.
A robust two-stage shape retrieval (TSR) method is proposed to address the 2D shape retrieval problem. Most state-of-the-art shape retrieval methods are based on local features matching and ranking. Their retrieval performance is not robust since they may retrieve globally dissimilar shapes in high ranks. To overcome this challenge, we decompose the decision process into two stages. In the first irrelevant cluster filtering (ICF) stage, we consider both global and local features and use them to predict the relevance of gallery shapes with respect to the query. Irrelevant shapes are removed from the candidate shape set. After that, a local-features-based matching and ranking (LMR) method follows in the second stage. We apply the proposed TSR system to MPEG-7, Kimia99 and Tari1000 three datasets and show that it outperforms all other existing methods. The robust retrieval performance of the TSR system is demonstrated.  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