全文获取类型
收费全文 | 4169篇 |
免费 | 59篇 |
国内免费 | 289篇 |
学科分类
工业技术 | 4517篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 15篇 |
2021年 | 13篇 |
2020年 | 27篇 |
2019年 | 6篇 |
2018年 | 15篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 43篇 |
2014年 | 128篇 |
2013年 | 83篇 |
2012年 | 170篇 |
2011年 | 293篇 |
2010年 | 173篇 |
2009年 | 147篇 |
2008年 | 245篇 |
2007年 | 332篇 |
2006年 | 324篇 |
2005年 | 358篇 |
2004年 | 318篇 |
2003年 | 336篇 |
2002年 | 312篇 |
2001年 | 240篇 |
2000年 | 186篇 |
1999年 | 166篇 |
1998年 | 112篇 |
1997年 | 76篇 |
1996年 | 69篇 |
1995年 | 49篇 |
1994年 | 41篇 |
1993年 | 32篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1981年 | 12篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有4517条查询结果,搜索用时 0 毫秒
1.
Biologically inspired design (BID) is one of the common methods for product design. To solve the problem of inaccurate acquisition of inspirational creatures due to the lack of user perception preference analysis, a data-driven intelligent service model for BID considering user perception needs is proposed based on Kansei engineering. Firstly, by extracting the perceptual features of creatures from the semantic source elements of products through mapping and encodes them, we proposed a data acquisition method based on intuitionistic fuzzy sets considering different customer preference distributions, bridging the gap caused by the asymmetry between designers and users. Secondly, the functional relationship between biometric features and user-perceived attributes is identified and predicted, and a predictive model of biodata considering user preferences is obtained by multiple linear regression analysis. Finally, based on the data clustering and reorganization theory to understand the organization and dynamics of the database, the construction of a BID library was completed, and the design resources in the library were used as analyzed knowledge for designers to plan design activities. Taking the bionic design of a UAV product as an example, a prototype of a computer-aided design service system was developed based on the theory proposed in the article, and the analyzed knowledge was used to improve the efficiency and science of the design, effectively verifying the usefulness of this study for design. To a certain extent, this study addresses the problem of cognitive limitations of designers and cognitive differences between designers and users, promotes the application of bioinspiration in product design, and improves the marketability of design solutions. 相似文献
2.
3.
《Journal of Great Lakes research》2022,48(1):37-51
Here, we describe the expansion and enhancement of a large (surface area ≥100 km2) lake and reservoir database (1.GREALD). These efforts have also resulted in the spin-off of two additional databases, one containing lakes and reservoirs (2.GREALD, area 10–99 km2), and the other containing ephemeral lakes (3.GELD, area ≥100 km2). These databases are unique sources for projects that utilize satellite radar altimeter data to monitor surface water levels. While 1.GREALD aims to be a complete catalog, 2.GREALD focuses on reservoirs in response to applied sciences programs that monitor water and energy resources. The creation of 3.GELD has climate change objectives as well as water resources and ecosystem conservation applications. The recording of information pertaining to the potential overpasses (waterbody crossings) of the current and archive satellite altimeters is a primary objective as is the need to highlight any form of controlled water level variation. The permanent water databases now contain 6282 entries, half experience some form of anthropogenic influence and ~430 have been identified as potential climatically sensitive terminal lakes. The revised integral surface area distribution is a power law with exponent ?1.016. Statistics reveal that with altimetric repeat visit times of 10-day to monthly, at least 80% of the permanent water bodies (≥10 km2) have been overflown at some period since the 1990s. Current information on water use and reservoir formation date show that the primary use of the reservoir class is hydroelectric power, and that China, Brazil, India, Turkey, and Vietnam dominate the dam building in recent decades. 相似文献
4.
随着数字化技术和数字孪生技术的不断应用和工程全命周期管理理念的不断完善,海洋钻机的各类数据信息系统也在不断地开发。为了解除三维设计数据库和模型规对数字化成果和应用范围的限制,本文对海洋钻机三维设计数据库与模型规划开展了深入的研究,并得出相关规划研究成果。 相似文献
6.
针对传统露天矿生产管理模式下人工计数的弊端,以及当前部分专题数据库未能充分利用空间数据的现状,从GIS空间分析的角度出发,提出以SQL Server 2008作为后台数据库的露天矿卡车调度系统数据库构建方案。在分析卡车调度系统需求的基础上,完成了数据库的概念设计、逻辑设计、物理设计及实现。该方案利用SQL Server2008新增的Geography数据类型存储并处理空间数据,将矿区的基础空间数据及卡车运行轨迹作为分析依据,具备车辆位置显示、轨迹回溯、卡车工作量自动统计等功能,确保了工作量统计的准确性,节约了人工成本,为进一步推动露天矿生产管理的现代化提供了有力的技术支撑。 相似文献
7.
王龙军 《成都电子机械高等专科学校学报》2015,(4):25-27
针对目前高校图书馆新闻管理系统开发成本高、集成化程度低、互动性不够等问题,采用 PHP 和 Oracle 数据库技术,设计并实现了一套图书馆新闻管理系统。该系统前台实现了新闻信息显示、搜索功能,系统后台实现了用户登录、添加新闻信息、修改新闻信息以及删除信息等功能。 相似文献
8.
We propose INDIANA, a system conceived to support a novel paradigm of database exploration. INDIANA assists the users who are interested in gaining insights about a database though an interactive and incremental process, like a conversation that does not happen in natural language. During this process, the system iteratively provides the user with some features of the data that might be “interesting” from the statistical viewpoint, receiving some feedbacks that are later used by the system to refine the features provided to the user in the next step. A key ability of INDIANA is to assist “data enthusiastic” users (i.e., inexperienced or casual users) in the exploration of transactional databases in an interactive way. For this purpose, we develop a number of novel, statistically-grounded algorithms to support the interactive exploration of the database. We report an in-depth experimental evaluation to show that the proposed system guarantees a very good trade-off between accuracy and scalability, and a user study that supports the claim that the system is effective in real-world database-exploration tasks. 相似文献
9.
Cold chain management can optimize freshness and safety to the consumer end. Within FRISBEE European project (http://frisbee-project.eu) a web-based platform was developed for temperature conditions data collection throughout the chilled and frozen food supply chain. Data including all cold chain stages (industry, distributors, retailers and consumers), were collected. This extensive database comprising more than 14,000 time-Temperature (t–T) profiles can serve as a valuable Cold Chain Management tool. The user can define a sequence of cold chain stages for selected food products. The Cold Chain Predictor (CCP) software based on the Cold Chain Database (CCD) allows calculation of product shelf-life status at different cold chain stages based on existing or user defined kinetic data. Conducted field tests expanded the Cold Chain Database and validated the software. The developed tools offer the potential to run simulation scenarios based on real cold chain data and contribute to effective cold chain improvement and management. 相似文献
10.
目的 探讨了碰撞面积值可以用于目标化合物定性和确证。方法 本研究中的农药包括杀虫剂、除草剂和杀菌剂,对75种农药采用离子淌度多维鉴定分析,数据采集信息种包括精确质量数、二级碎片和碰撞截面积值数据,运用拟合优度作为统计方法,探究碰撞截面积值和质荷比之间的相关性。结果 用75种农药的碰撞截面积值和质荷比进行了统计分析,获得了在不同加合物情况下,碰撞截面值与质荷比之间的非线性关系。在不同的加合物情况下,获得了不同的拟合度结果,首先进行了全部加合物计算,拟合度值R2达到 为0.8440;加合物+H离子时,拟合度值R2 为0.7786;加合物+Na离子时,拟合度值R2 为0.9141;在加合物+H和+Na离子时,拟合度值R2 为0.8267。在27份液态奶和20份牛肉样本中,经过筛查,未发现本研究中的75种农药残留。结论 本方法适用于这75种农药在未知物种的筛查和确证,为农药相关未知物筛查中提供数据基础。
关键词:碰撞截面积值;农药;数据库;牛肉和液态奶 相似文献