全文获取类型
收费全文 | 37837篇 |
免费 | 3643篇 |
国内免费 | 1705篇 |
专业分类
电工技术 | 2581篇 |
技术理论 | 1篇 |
综合类 | 2339篇 |
化学工业 | 6458篇 |
金属工艺 | 2149篇 |
机械仪表 | 2405篇 |
建筑科学 | 2894篇 |
矿业工程 | 1132篇 |
能源动力 | 1052篇 |
轻工业 | 3060篇 |
水利工程 | 683篇 |
石油天然气 | 1814篇 |
武器工业 | 293篇 |
无线电 | 4600篇 |
一般工业技术 | 4813篇 |
冶金工业 | 1665篇 |
原子能技术 | 493篇 |
自动化技术 | 4753篇 |
出版年
2024年 | 207篇 |
2023年 | 759篇 |
2022年 | 1515篇 |
2021年 | 1806篇 |
2020年 | 1398篇 |
2019年 | 1118篇 |
2018年 | 1263篇 |
2017年 | 1395篇 |
2016年 | 1195篇 |
2015年 | 1623篇 |
2014年 | 2057篇 |
2013年 | 2316篇 |
2012年 | 2466篇 |
2011年 | 2572篇 |
2010年 | 2143篇 |
2009年 | 2175篇 |
2008年 | 2112篇 |
2007年 | 1849篇 |
2006年 | 1927篇 |
2005年 | 1546篇 |
2004年 | 1017篇 |
2003年 | 1053篇 |
2002年 | 997篇 |
2001年 | 870篇 |
2000年 | 835篇 |
1999年 | 874篇 |
1998年 | 732篇 |
1997年 | 605篇 |
1996年 | 534篇 |
1995年 | 491篇 |
1994年 | 357篇 |
1993年 | 281篇 |
1992年 | 254篇 |
1991年 | 168篇 |
1990年 | 144篇 |
1989年 | 128篇 |
1988年 | 96篇 |
1987年 | 61篇 |
1986年 | 34篇 |
1985年 | 38篇 |
1984年 | 22篇 |
1983年 | 27篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 17篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Balasa F. Catthoor F. Hugo De Man 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》1995,3(2):157-172
Memory cost is responsible for a large amount of the chip and/or board area of customized video and image processing system realizations. In this paper, we present a novel technique-founded on data-flow analysis which allows one to address the problem of background memory size evaluation for a given nonprocedural algorithm specification, operating on multidimensional signals with affine indexes. Most of the target applications are characterized by a huge number of signals, so a new polyhedral data-flow model operating on groups of scalar signals is proposed. These groups are obtained by a novel analytical partitioning technique, allowing to select a desired granularity, depending on the application complexity. The method incorporates a way to tradeoff memory size with computational and controller complexity 相似文献
73.
Fan Chu Hong-Tao Sun Liang-Ying Zhang Xi Yao 《Journal of the American Ceramic Society》1992,75(11):2939-2944
Based on a linear voltage ramp method, ultraslow dielectric relaxation of undoped BaTiO3 ceramic has been carefully measured over the temperature range between − 180° and +120°C. Temperature dependence of the dielectric constant in the frequency range from 10 −5 to 10−1 Hz can be obtained using Kramers–Kronig equations. Close to the Curie temperature, the dielectric constant increases so rapidly that the Curie peak is overwhelmed. Two kinds of relaxation processes were observed in this experiment. Ferroelectric domain and mobile charge are proposed to be responsible for the relaxation over the temperature range. With temperature increasing, Maxwell–Wagner relaxation associated with mobile charge gradually dominates. From relaxation time constants at various temperatures, relaxation activation energies about 0.06 and 0.09 eV are identified. 相似文献
74.
丁苯胶乳改性道路沥青的推广应用 总被引:2,自引:0,他引:2
用丁苯胶乳对胜利100号沥青进行改性试验.发现随着胶乳掺量的增加.沥青的高温性能、粘结性能改善幅度也大。但综合考虑沥青生产成本等因素.认为:对丁苯胶乳改性胜利100号道路沥青.掺胶量控制在2%即可满足一般高等级道路工程的需要。文中还介绍了丁苯胶乳沥青近年来的推广使用情况并做了相应的技术经济分析和建议。 相似文献
75.
刍议小型水电站项目收购风险管理 总被引:1,自引:0,他引:1
相对于其他项目的收购风险评估,小型水电站(电站总装机容量5万kW以下)收购有其特殊性。在总结和归纳小型水电站特点的基础上,结合一般项目收购风险评估方法,分析项目收购各个阶段存在的风险和对策。为有收购水电项目意向的企业和个人提供决策依据。图1幅。 相似文献
76.
Degradation Behaviors of Metal-Induced Laterally Crystallized n-Type Polycrystalline Silicon Thin-Film Transistors Under DC Bias Stresses 总被引:1,自引:0,他引:1
Min Xue Mingxiang Wang Zhen Zhu Dongli Zhang Man Wong 《Electron Devices, IEEE Transactions on》2007,54(2):225-232
Device degradation behaviors of typical-sized n-type metal-induced laterally crystallized polycrystalline silicon thin-film transistors were investigated in detail under two kinds of dc bias stresses: hot-carrier (HC) stress and self-heating (SH) stress. Under HC stress, device degradation is the consequence of HC induced defect generation locally at the drain side. Under a unified model that postulates, the establishment of a potential barrier at the drain side due to carrier transport near trap states, device degradation behavior such as asymmetric on current recovery and threshold voltage degradation can be understood. Under SH stress, a general degradation in subthreshold characteristic was observed. Device degradation is the consequence of deep state generation along the entire channel. Device degradation behaviors were compared in low Vd-stress and in high Vd-stress condition. Defect generation distribution along the channel appears to be different in two cases. In both cases of SH degradation, asymmetric on current recovery was observed. This observation, when in low Vd-stress condition, is tentatively explained by dehydrogenation (hydrogenation) effect at the drain (source) side during stress 相似文献
77.
Application of model predictive control strategy based on fuzzy identification to an SP-100 space reactor 总被引:1,自引:0,他引:1
In this work, a model predictive control method combined with fuzzy identification, is applied to the design of the thermoelectric (TE) power control in the SP-100 space reactor. The future TE power is predicted by using the fuzzy model identified by a subtractive clustering method of a fast and robust algorithm. The objectives of the proposed fuzzy model predictive controller are to minimize both the difference between the predicted TE power and the desired power, and the variation of control drum angle that adjusts the control reactivity. Also, the objectives are subject to maximum and minimum control drum angle and maximum drum angle variation speed. The genetic algorithm that is effective in accomplishing multiple objectives is used to optimize the fuzzy model predictive controller. A lumped parameter simulation model of the SP-100 nuclear space reactor is used to verify the proposed controller. The results of numerical simulations to check the performance of the proposed controller show that the TE generator power level controlled by the proposed controller could track the target power level effectively, satisfying all control constraints. 相似文献
78.
以乙醇为溶剂,正硅酸乙酯(TEOS,tetraethoxysilane)在氢氧化铵催化下水解缩聚为纳米尺度的无定型SiO2溶胶颗粒,二甲基二乙氧基硅烷(DDS,dimethyldiethoxysilane)在盐酸催化下水解缩聚为线状聚二甲基硅氧链.用混合溶胶在玻璃基片上旋转镀膜,然后于80℃空气气氛下热处理.实验证明通过DDS将疏水的双甲基链引入镀膜胶体,使膜兼具疏水性和减反射性能.利用激光散射粒度分析仪和电子显微镜研究了溶胶颗粒的粒度变化和聚集情况等溶胶微结构,用物理吸附仪研究了膜的孔结构,考察了热处理前后膜的疏水性和透射谱,得到了溶胶微结构与膜性能之间的关联. 相似文献
79.
本文通过对蜂窝陶瓷载体成型过程的分析,指出在其成型过程中存在的问题,提出了采用液压同步剪解决这些问题的方法。论文分析了同步剪的工作原理,给出了其液压原理图及其设计特点。 相似文献
80.