全文获取类型
收费全文 | 37644篇 |
免费 | 4238篇 |
国内免费 | 2699篇 |
专业分类
电工技术 | 3654篇 |
技术理论 | 8篇 |
综合类 | 3645篇 |
化学工业 | 1268篇 |
金属工艺 | 319篇 |
机械仪表 | 900篇 |
建筑科学 | 3497篇 |
矿业工程 | 1230篇 |
能源动力 | 1398篇 |
轻工业 | 1947篇 |
水利工程 | 1964篇 |
石油天然气 | 857篇 |
武器工业 | 436篇 |
无线电 | 5346篇 |
一般工业技术 | 1917篇 |
冶金工业 | 1363篇 |
原子能技术 | 373篇 |
自动化技术 | 14459篇 |
出版年
2024年 | 227篇 |
2023年 | 599篇 |
2022年 | 1064篇 |
2021年 | 1357篇 |
2020年 | 1387篇 |
2019年 | 1098篇 |
2018年 | 1063篇 |
2017年 | 1204篇 |
2016年 | 1535篇 |
2015年 | 1478篇 |
2014年 | 3135篇 |
2013年 | 2980篇 |
2012年 | 3163篇 |
2011年 | 3521篇 |
2010年 | 2613篇 |
2009年 | 2562篇 |
2008年 | 2480篇 |
2007年 | 2711篇 |
2006年 | 2361篇 |
2005年 | 1917篇 |
2004年 | 1483篇 |
2003年 | 1278篇 |
2002年 | 870篇 |
2001年 | 611篇 |
2000年 | 440篇 |
1999年 | 287篇 |
1998年 | 222篇 |
1997年 | 146篇 |
1996年 | 139篇 |
1995年 | 91篇 |
1994年 | 91篇 |
1993年 | 62篇 |
1992年 | 43篇 |
1991年 | 36篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 32篇 |
1987年 | 22篇 |
1986年 | 23篇 |
1985年 | 29篇 |
1984年 | 28篇 |
1983年 | 23篇 |
1982年 | 18篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1971年 | 4篇 |
1965年 | 14篇 |
1959年 | 5篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
David F. Barrero Julio César Hernández‐Castro Pedro Peris‐Lopez David Camacho María D. R‐Moreno 《Expert Systems》2014,31(1):9-19
Radio frequency identification (RFID) is a powerful technology that enables wireless information storage and control in an economical way. These properties have generated a wide range of applications in different areas. Due to economic and technological constrains, RFID devices are seriously limited, having small or even tiny computational capabilities. This issue is particularly challenging from the security point of view. Security protocols in RFID environments have to deal with strong computational limitations, and classical protocols cannot be used in this context. There have been several attempts to overcome these limitations in the form of new lightweight security protocols designed to be used in very constrained (sometimes called ultra‐lightweight) RFID environments. One of these proposals is the David–Prasad ultra‐lightweight authentication protocol. This protocol was successfully attacked using a cryptanalysis technique named Tango attack. The capacity of the attack depends on a set of boolean approximations. In this paper, we present an enhanced version of the Tango attack, named Genetic Tango attack, that uses Genetic Programming to design those approximations, easing the generation of automatic cryptanalysis and improving its power compared to a manually designed attack. Experimental results are given to illustrate the effectiveness of this new attack. 相似文献
92.
《Calphad》2014
Thermodynamic properties and phase diagrams of the MCl–YCl3 (M=Na, K, Rb, Cs) systems were reassessed by using the CALPHAD method with the latest phase diagram data. A two-sublattice ionic solution model (M+)P(Cl−, , YCl3)Q reflecting the ionic behavior of the components was adopted to describe the liquid phase in the systems. A new set of optimized model parameters was found, and the calculated phase diagrams and enthalpies of mixing have good agreement with experimental data. The calculated liquidus near to YCl3 side agrees much better with experimental data compared with previous work. In consideration of high and low temperature modifications as well as stability of intermediate compounds, Gibbs energies of formation of these compounds evaluated in the present work are more reasonable. 相似文献
93.
Career visual searchers such as radiologists and airport security screeners strive to conduct accurate visual searches, but despite extensive training, errors still occur. A key difference between searches in radiology and airport security is the structure of the search task: Radiologists typically scan a certain number of medical images (fixed objective), and airport security screeners typically search X-rays for a specified time period (fixed duration). Might these structural differences affect accuracy? We compared performance on a search task administered either under constraints that approximated radiology or airport security. Some displays contained more than one target because the presence of multiple targets is an established source of errors for career searchers, and accuracy for additional targets tends to be especially sensitive to contextual conditions. Results indicate that participants searching within the fixed objective framework produced more multiple-target search errors; thus, adopting a fixed duration framework could improve accuracy for career searchers. 相似文献
94.
Pieter Coenen Margriet Formanoy Marjolein Douwes Tim Bosch Heleen de Kraker 《Applied ergonomics》2014
Exposure to mechanical vibrations at work (e.g., due to handling powered tools) is a potential occupational risk as it may cause upper extremity complaints. However, reliable and valid assessment methods for vibration exposure at work are lacking. Measuring hand-arm vibration objectively is often difficult and expensive, while often used information provided by manufacturers lacks detail. Therefore, a subjective hand-arm vibration assessment method was tested on validity and inter-observer reliability. 相似文献
95.
The secure operation of autonomous vehicle networks in the presence of adversarial observation is examined, in the context of a canonical double-integrator-network (DIN) model. Specifically, we study the ability of a sentient adversary to estimate the full network’s state, from noisy local measurements of vehicle motions. Algebraic, spectral, and graphical characterizations are provided, which indicate the critical role of the inter-vehicle communication topology and control scheme in achieving security. 相似文献
96.
Giuseppe Placidi Danilo Avola Marco Ferrari Daniela Iacoviello Andrea Petracca Valentina Quaresima Matteo Spezialetti 《Computer methods and programs in biomedicine》2014
Background and objective
The degeneration of the balance control system in the elderly and in many pathologies requires measuring the equilibrium conditions very often. In clinical practice, equilibrium control is commonly evaluated by using a force platform (stabilometric platform) in a clinical environment.In this paper, we demonstrate how a simple movement analysis system, based on a 3D video camera and a 3D real time model reconstruction of the human body, can be used to collect information usually recorded by a physical stabilometric platform.Methods
The algorithm used to reconstruct the human body model as a set of spheres is described and discussed. Moreover, experimental measurements and comparisons with data collected by a physical stabilometric platform are also reported. The measurements were collected on a set of 6 healthy subjects to whom a change in equilibrium condition was stimulated by performing an equilibrium task.Results
The experimental results showed that more than 95% of data collected by the proposed method were not significantly different from those collected by the classic platform, thus confirming the usefulness of the proposed system.Conclusions
The proposed virtual balance assessment system can be implemented at low cost (about 500$) and, for this reason, can be considered a home use medical device. On the contrary, astabilometric platform has a cost of about 10,000$ and requires periodical calibration. The proposed system does not require periodical calibration, as is necessary for stabilometric force platforms, and it is easy to use. In future, the proposed system with little integration can be used, besides being an emulator of a stabilometric platform, also to recognize and track, in real time, head, legs, arms and trunk, that is to collect information actually obtained by sophisticated optoelectronic systems. 相似文献97.
为了提高彩色图像加密的安全性和加密性能,设计了一种基于多混沌系统的彩色图像加密方法.将一个彩色图像分解为R、G、B三个灰度图像,使用MD5算法动态生成加密算法的初始值,然后使用三种不同的基于混沌的加密结构对三个图像进行加密.对R图像使用Feistel结构加密,其中Feistel结构的S一盒由Logistic混沌序列和Hyperhenon混沌序列组合产生;对G图像使用由Lorenz系统产生加密序列对图像进行代替和置换操作的加密结构;对B图像使用由分段线性混沌映射产生加密序列,然后加密图像的加密结构,再把加密后的图像结合起来生成加密后的图像.理论分析和实验结果表明,该加密方法能够较为有效地保证彩色图像加密的安全性. 相似文献
98.
99.
从手机银行的应用现状出发,阐述手机银行的技术架构以及常见的安全风险。结合国家等级保护及行业主管部门的相关技术要求,分析手机银行的各个层面的风险评估指标,并采取层次分析法确定各指标的权重,最后得出手机银行的总体安全情况。在此基础上形成的手机银行风险评价体系,可量化风险评估结果,为手机银行的风险管理提供依据。 相似文献
100.
为提高云数据中心的抗毁能力,针对软硬件日趋复杂化带来的诸多故障问题,以传统的服务器心跳检测机制为基础,结合云计算的特点,提出一种保证云数据中心有效运行的心跳检测与故障评估方案。在实验室搭建仿真平台进行实验,实验结果表明,该方案能够及时检测到节点故障,依据预先制定的故障等级评估标准,采用模糊综合法进行评估,为云数据中心的管理与运作提供参考依据与保障。 相似文献