全文获取类型
收费全文 | 99962篇 |
免费 | 9760篇 |
国内免费 | 5240篇 |
专业分类
电工技术 | 6503篇 |
技术理论 | 5篇 |
综合类 | 7128篇 |
化学工业 | 15781篇 |
金属工艺 | 5823篇 |
机械仪表 | 6639篇 |
建筑科学 | 8010篇 |
矿业工程 | 2993篇 |
能源动力 | 2725篇 |
轻工业 | 6810篇 |
水利工程 | 2148篇 |
石油天然气 | 5559篇 |
武器工业 | 992篇 |
无线电 | 12344篇 |
一般工业技术 | 11303篇 |
冶金工业 | 4435篇 |
原子能技术 | 1113篇 |
自动化技术 | 14651篇 |
出版年
2024年 | 521篇 |
2023年 | 1923篇 |
2022年 | 3676篇 |
2021年 | 4951篇 |
2020年 | 3696篇 |
2019年 | 2849篇 |
2018年 | 3141篇 |
2017年 | 3574篇 |
2016年 | 3077篇 |
2015年 | 4459篇 |
2014年 | 5593篇 |
2013年 | 6464篇 |
2012年 | 7047篇 |
2011年 | 7755篇 |
2010年 | 6801篇 |
2009年 | 6288篇 |
2008年 | 6340篇 |
2007年 | 5624篇 |
2006年 | 5275篇 |
2005年 | 4370篇 |
2004年 | 2813篇 |
2003年 | 2299篇 |
2002年 | 2192篇 |
2001年 | 1945篇 |
2000年 | 1764篇 |
1999年 | 1916篇 |
1998年 | 1540篇 |
1997年 | 1245篇 |
1996年 | 1181篇 |
1995年 | 1023篇 |
1994年 | 830篇 |
1993年 | 613篇 |
1992年 | 474篇 |
1991年 | 388篇 |
1990年 | 272篇 |
1989年 | 215篇 |
1988年 | 181篇 |
1987年 | 109篇 |
1986年 | 99篇 |
1985年 | 69篇 |
1984年 | 53篇 |
1983年 | 54篇 |
1982年 | 43篇 |
1981年 | 38篇 |
1980年 | 44篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
混合匹配规则的否定选择算法 总被引:1,自引:0,他引:1
针对目前基于免疫的检测器生成算法中,匹配规则单一造成的检测器质量低下的问题,提出一种基于混合匹配规则的否定选择算法,采用海明距离整体匹配的各段内R连续比特匹配的否定选择算法,即混合匹配否定选择算法,对算法的性能进行了分析.实验结果表明,该算法能够高效地产生所需要的检测器,提高了检测率,且降低了误报率. 相似文献
122.
This paper presents a transient axial dispersion model for an isothermal, catalytic fluidized bed reactor, which is frequently employed in synthetic production processes including coal gasification and liquefaction. A non-linear chemical reaction is considered to occur in the reactor. This model of a fluidized bed reactor takes into account the axial dispersion in the three phases, bubble, cloud-wake and emulsion. The physical properties along the axial coordinate are invariant in the model. Transient characteristics of the gas reactant, and the length of the transient period have been examined based on the model. The model compares favorably with experimental data in the steady state condition. 相似文献
123.
Paul S. K. Choi Liang T. Fan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1973,23(7):531-548
Mathematical models are developed for the transient behaviour of encapsulated enzyme reactor systems such as the continuous stirred tank reactor (CSTR) and the packed bed tubular reactor. The rate processes taking place in the encapsulated enzyme bed are approximated by using a combined rate control model of enzyme reaction and membrane diffusion. The change in transient substrate concentration is obtained by using the developed rate expression in the material balance over the substrate as a function of time for the CSTR and as a function of time and position for the packed bed tubular reactor. The effects of various parameters such as the enzymic reaction rate constant, Michaelis constant, diffusional resistance of membranes, and Peclet number on the substrate concentration distribution, which varies with respect to operating time, are investigated. This study affords insight into the transient operating characteristics of the encapsulated enzyme reactor system. The results should be useful in understanding the start-up performance of the reactor systems and to control such reactor systems at desired operating conditions. 相似文献
124.
125.
Temperature control curve is the key to achieving temperature control and crack prevention of high concrete dam during construction,and its rationality depends on the accurate measurement of temperature stress.With the simulation testing machine for the temperature stress,in the present study,we carried out the deformation process tests of concrete under three temperature curves:convex,straight and concave.Besides,we not only measured the early-age elastic modulus,creep parameters and stress process,but also proposed the preferred type.The results show that at early age,higher temperature always leads to greater elastic modulus and smaller creep.However,the traditional indoor experiments have underestimated the elastic modulus and creep development at early age,which makes the calculated value of temperature stress too small,thus increasing the cracking risk.In this study,the stress values of the three curves calculated based on the strain and early-age parameters are in good agreement with the temperature stress measured by the temperature stress testing machine,which verifies the method accuracy.When the temperature changes along the concave curve,the law of stress development is in consistent with that of strength.Under this condition,the stress fluctuation is small and the crack prevention safety of the concave type is higher,so the concave type is better.The test results provide a reliable basis and support for temperature control curve design and optimization of concrete dams. 相似文献
126.
Multibody System Dynamics - A recursive rotational-coordinate-based formulation of a planar Euler–Bernoulli beam is developed, where large displacements, deformations, and rotations are... 相似文献
127.
While the significance of oscillator dynamics and coupling structure to synchronization behaviors has been well addressed in the literature, little attention has been paid to the possible influence of coupling functions. In the present paper, adopting the scheme of dual-channel time-delayed couplings, we investigate how the synchronization behaviors of networked chaotic oscillators are influenced by parameters in the coupling functions. It is found that, with the introduction of the second coupling channel, the synchronization region, as calculated according to the method of master stability function (MSF), can be largely modified. In particular, by a slight change of the time delay, it is found that the synchronization region can be significantly adjusted, or even switched from non-existing to existing. We demonstrate this interesting phenomenon for both situations of processing and propagation induced time delays, as well as for different coupling functions. Our studies shed new light on the mechanism of chaos synchronization, and may potentially be used for the control of complex network dynamics. 相似文献
128.
张帆 《吉林化工学院学报》2015,(7):76-79
采用目标追求的入世、出世量表筛选出入世水平高组(70名)和低组(72)大学生,出世水平高组(68名)和低组(71名)大学生,探讨不同入世、出世水平大学生在奖学金申请、选修课和求职应聘三种决策任务领域上的框架效应及其在性别上的特点。结果发现:(1)不同出入世水平大学生在决策任务上的框架效应特点不同,入世水平高分组和低分组、出世水平高分组和低分组在奖学金申请问题上均出现了经典的框架效应;(2)在奖学金申请问题上,男性被试和女性被试的选择出现了明显的经典的框架效应。 相似文献
129.
专业建设是高等学校最重要的教学基本建设,是教育教学工作的基础和重要生命线,是高等学校人才培养的重要依托。加强本科品牌专业的建设可提升学校本科专业建设的整体水平,提高学校本科人才培养质量、效益和竞争力。文章围绕如何开展品牌专业建设,结合学校实际,着重从品牌专业内涵、建设原则、内容和评价办法等方面进行了阐述。 相似文献
130.
采用介质阻挡放电(DBD)降解常压下流动态的邻二甲苯模拟废气,系统地考察了放电极值电压,气体的初始质量浓度、停留时间以及相对湿度等工艺参数对邻二甲苯降解的影响,并初步探讨了邻二甲苯的降解产物.实验研究结果表明:在7.0kV的放电极间电压下,邻二甲苯的初始质量浓度为1 500mg/m3,停留时间为9s,其去除率可达到80%以上.降解产物主要为CO2、H2O以及苯甲酸、苯乙酸、苯乙醛等有机物,并且经降解后产物的生物可生化性得到提高,因而为后续的等离子-生物法联合处理VOCs提供了依据. 相似文献