全文获取类型
收费全文 | 94024篇 |
免费 | 9398篇 |
国内免费 | 6313篇 |
专业分类
电工技术 | 6657篇 |
技术理论 | 4篇 |
综合类 | 11086篇 |
化学工业 | 21554篇 |
金属工艺 | 2548篇 |
机械仪表 | 4799篇 |
建筑科学 | 5453篇 |
矿业工程 | 2925篇 |
能源动力 | 2267篇 |
轻工业 | 5830篇 |
水利工程 | 2692篇 |
石油天然气 | 6363篇 |
武器工业 | 1628篇 |
无线电 | 5889篇 |
一般工业技术 | 8652篇 |
冶金工业 | 2216篇 |
原子能技术 | 486篇 |
自动化技术 | 18686篇 |
出版年
2024年 | 396篇 |
2023年 | 1198篇 |
2022年 | 2042篇 |
2021年 | 2530篇 |
2020年 | 2733篇 |
2019年 | 2383篇 |
2018年 | 2408篇 |
2017年 | 2690篇 |
2016年 | 3328篇 |
2015年 | 3463篇 |
2014年 | 5536篇 |
2013年 | 5461篇 |
2012年 | 6731篇 |
2011年 | 7597篇 |
2010年 | 5657篇 |
2009年 | 6036篇 |
2008年 | 5608篇 |
2007年 | 6910篇 |
2006年 | 6169篇 |
2005年 | 5448篇 |
2004年 | 4393篇 |
2003年 | 3890篇 |
2002年 | 3189篇 |
2001年 | 2728篇 |
2000年 | 2299篇 |
1999年 | 1872篇 |
1998年 | 1483篇 |
1997年 | 1126篇 |
1996年 | 929篇 |
1995年 | 775篇 |
1994年 | 635篇 |
1993年 | 479篇 |
1992年 | 344篇 |
1991年 | 263篇 |
1990年 | 204篇 |
1989年 | 188篇 |
1988年 | 105篇 |
1987年 | 76篇 |
1986年 | 51篇 |
1985年 | 45篇 |
1984年 | 54篇 |
1983年 | 50篇 |
1982年 | 32篇 |
1981年 | 27篇 |
1980年 | 13篇 |
1979年 | 28篇 |
1978年 | 18篇 |
1977年 | 18篇 |
1976年 | 9篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
含氨烷基聚硅氧烷的研究进展 总被引:1,自引:0,他引:1
对含氨烷基聚硅氧烷的研究进行综述,着重介绍含氨烷基聚硅氧烷的种类,性能特点,制备方法及应用等。 相似文献
102.
103.
Namoi Shibasaki Ryousuke Obika Toshikuni Yonemoto Teiriki Tadaki 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):201-208
Suspension cultures of tobacco cells were studied using airlift and rotary-drum bioreactors. The effect of initial concentrations of a major substrate, sucrose, on the growth and production of a secondary metabolite, phenolic compounds, was investigated. The dry weights and total concentrations of the phenolic compounds increased with the initial sucrose concentration in both bioreactors. Both bioreactors were found to have the same tendency for the effect of initial sucrose concentration. The structured model, presented previously was modified by considering that sucrose was hydrolyzed to glucose and fructose by an enzymatic reaction. The previous and the new models were applied to the above two sets of experimental data obtained with two bioreactors, independently. The hydrolysis of sucrose was elucidated to contribute slightly to the overall kinetics of growth and secondary metabolite production in these cultures. Furthermore, the levels of shear damage in each bioreactor were quantitatively compared based on the death rate constant, ki, which is one of the model constants. 相似文献
104.
Helena Szczerbicka 《Performance Evaluation》1992,14(3-4):217-226
In this paper the performability analysis of fault-tolerant computer systems using a hierarchical decomposition technique is presented. A special class of queueing network (QN) models, the so-called BCMP [4], and generalized stochastic Petri nets (GSPN) [1] which are often used to separately model performance and reliability respectively, have been combined in order to preserve the best modelling features of both.
A conceptual model is decomposed into GSPN and BCMP submodels, which are solved in isolation. Then, the remaining GSPN portion of the model is aggregated with flow-equivalents of BCMP models, in order to compute performability measures. The substitutes of BCMP models are presented by means of simple GSPN constructs, thereby preserving the 1st and 2nd moments of the throughput. A simple example of a data communication system where failed transmissions are corrected, is presented. 相似文献
105.
红外热成象技术可以有效地用于股骨头坏死疾病的诊断和针刺治疗效果的评价,效果优于其它常规方法。 相似文献
106.
SynthesisandCrystalStructureofRE[CH2(CH2)4CONC4H9]3(NO3)3(RE=Dy,La)WangHanzhang(王汉章),XuQingfeng(徐庆锋),QianPu(钱朴)SunJianping(孙建... 相似文献
107.
Duane J. Lewis 《Journal of the American Ceramic Society》1991,74(10):2410-2413
Mixed-oxide systems are of interest in a variety of technical ceramic applications. The key in many systems is to achieve a high degree of homogeneity, approaching the molecular level. A technique for producing mixed oxides via direct oxidation of mixtures of organometallic compounds is discussed as a potential route. Preliminary work performed on producing mullite is discussed. 相似文献
108.
本文对Lurgi低压法甲醇工艺中压力的参变效应进行了探讨.通过计算机模拟,给出了合成压力变化的效应情况.计算结果表明煤头小型低压法甲醇装置的合成压力应高于大型装置的合成压力,其值在7.3~8.0MPa之间可取得最佳的节能降耗效果. 相似文献
109.
Marcus T. Schmitz Bashir M. Al-Hashimi Petru Eles 《Design Automation for Embedded Systems》2002,6(4):401-424
In this paper, we introduce the LOPOCOS (Low Power Co-synthesis) system, a prototype CAD tool for system level co-design. LOPOCOS targets the design of energy-efficient embedded systems implemented as heterogeneous distributed architectures. In particular, it is designed to solve the specific problems involved in architectures that include dynamic voltage scalable (DVS) processors. The aim of this paper is to demonstrate how LOPOCOS can support the system designer in identifying energy-efficient hardware/software implementations for the desired embedded systems. Hence, highlighting the necessary optimization steps during design space exploration for DVS enable architectures. The optimization steps carried out in LOPOCOS involve component allocation and task/communication mapping as well as scheduling and dynamic voltage scaling. LOPOCOS has the following key features, which contribute to this energy efficiency. During the voltage scaling valuable power profile information of task execution is taken into account, hence, the accuracy of the energy estimation is improved. A combined optimization for scheduling and communication mapping based on genetic algorithm, optimizes simultaneously execution order and communication mapping towards the utilization of the DVS processors and timing behaviour. Furthermore, a separation of task and communication mapping allows a more effective implementation of both task and communication mapping optimizationsteps. Extensive experiments are conducted to demonstrate the efficiency of LOPOCOS. We report up to 38% higher energy reductions compared to previous co-synthesis techniques for DVS systems. The investigations include a real-life example of an optical flow detection algorithm. 相似文献
110.
聚苯硫醚酰胺的合成与表征 总被引:7,自引:1,他引:6
用4-氯苯甲酰4′-氯苯胺和硫化钠为原料在常压下合成了聚苯硫醚酰胺,并对其进行了表征。结果表明所合成的产物为结晶性聚合物,并且有较高的热稳定性。 相似文献