全文获取类型
收费全文 | 56950篇 |
免费 | 5093篇 |
国内免费 | 2658篇 |
专业分类
电工技术 | 3499篇 |
技术理论 | 8篇 |
综合类 | 3627篇 |
化学工业 | 9419篇 |
金属工艺 | 2934篇 |
机械仪表 | 3273篇 |
建筑科学 | 3980篇 |
矿业工程 | 1505篇 |
能源动力 | 1754篇 |
轻工业 | 3486篇 |
水利工程 | 1096篇 |
石油天然气 | 2830篇 |
武器工业 | 646篇 |
无线电 | 6946篇 |
一般工业技术 | 6766篇 |
冶金工业 | 4372篇 |
原子能技术 | 697篇 |
自动化技术 | 7863篇 |
出版年
2024年 | 255篇 |
2023年 | 909篇 |
2022年 | 1802篇 |
2021年 | 2459篇 |
2020年 | 1819篇 |
2019年 | 1523篇 |
2018年 | 1694篇 |
2017年 | 1804篇 |
2016年 | 1623篇 |
2015年 | 2279篇 |
2014年 | 2702篇 |
2013年 | 3432篇 |
2012年 | 3571篇 |
2011年 | 3783篇 |
2010年 | 3321篇 |
2009年 | 3227篇 |
2008年 | 3109篇 |
2007年 | 2944篇 |
2006年 | 2974篇 |
2005年 | 2468篇 |
2004年 | 1852篇 |
2003年 | 1620篇 |
2002年 | 1671篇 |
2001年 | 1530篇 |
2000年 | 1318篇 |
1999年 | 1379篇 |
1998年 | 1695篇 |
1997年 | 1269篇 |
1996年 | 957篇 |
1995年 | 763篇 |
1994年 | 556篇 |
1993年 | 535篇 |
1992年 | 340篇 |
1991年 | 280篇 |
1990年 | 195篇 |
1989年 | 189篇 |
1988年 | 154篇 |
1987年 | 93篇 |
1986年 | 101篇 |
1985年 | 87篇 |
1984年 | 33篇 |
1983年 | 31篇 |
1982年 | 40篇 |
1981年 | 36篇 |
1980年 | 34篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1977年 | 39篇 |
1976年 | 71篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Hsing-Chung Liang Wen-Chin Ho Ming-Chieh Cheng 《Reliability, IEEE Transactions on》2005,54(2):358-365
In this paper, we discuss some strategies for identifying unrepairable memories, and from that to introduce a novel theorem that can make more precise identification. A new algorithm for searching repair solutions is also proposed, which characterizes the rows, and columns of defective memory cells with revised effective coefficients. We have simulated it on many generated example maps, and compared it with the previous algorithms to verify its efficiency. It's combined with those arranged strategies of judging unrepairability to generate a complete flow. The complete algorithm has also been run on many examples with various memory sizes, defect numbers, and distribution types. The simulation results further show that identifying unrepairability in advance can help the reconfiguration procedure run much faster than searching solutions directly. 相似文献
22.
A new frequency notched ultra-wideband microstrip slot antenna with a parasitic tuning stub is proposed. The antenna is similar in configuration to a conventional microstrip slot antenna; by introducing a parasitic open-circuit tuning stub, flexible frequency notched function is achieved. Several properties of the antenna, such as frequency notched function, antenna transfer function and gain, have been investigated. As is reported, the operation bandwidth of the antenna is 2.91-11.16 GHz, in which a frequency notched band of 5.10-5.85 GHz has been achieved. Furthermore, good ultra-wideband linear transmission performance over the entire operation frequency range has also been achieved. 相似文献
23.
介绍了子午轮胎硫化的各种介质性能要求及介质供应工艺流程,分析了各种介质的质量要求.介绍了系统各参数的控制调节项目及运行技术管理的一些措施. 相似文献
24.
25.
Xiaojun Xie Yonghong Cheng Hong Wang Qian Wang Xiaolin Chen Caixin Sun 《Ceramics International》2008,34(4):689-693
In the ideal A2B2O6O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi1.5ZnNb1.5−xTaxO7 (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores. 相似文献
26.
27.
A new torque estimator for switched reluctance motor (SRM) drives based on 2-D rotary regression analysis is presented in this paper. The proposed torque estimator is composed of a bicubic regressive polynomial as a function of rotor position and input current. The regressive coefficients can be computed offline or online from the torque characteristics acquired either experimentally or from numerical computation. Furthermore, a torque estimation method by taking mutual coupling into consideration is proposed. It can be seen that the estimated and experimentally obtained self-coupling and mutual-coupling torque characteristics are in good agreement with each other. In addition, the dynamic torque waveforms with and without the mutual coupling, estimated by the proposed estimator, are found to be virtually the same as those obtained from the bicubic spline interpolation for SRM drives with single-pulse voltage, hysteresis current chopping, as well as with voltage pulse width modulation control. The success of all the case studies being reported is a good validation of the usefulness and accuracy of the proposed real-time torque estimator that, as described in this paper, can be used to quickly estimate the instantaneous output torque of SRM drives. 相似文献
28.
Junwei Fu Zhengbiao Zhang Zhenping Cheng Jian Zhu Wei Zhang Xiulin Zhu 《Polymer Bulletin》2008,61(3):287-297
A novel reversible addition-fragmentation chain transfer (RAFT) reagent bearing triphenylamine (TPA)
group, 4-diphenylamino-dithiobenzoic acid benzyl ester (DDABE), was designed and synthesized. It was used
in the RAFT polymerizations of styrene (St) and methyl acrylate (MA) to prepare end-functionalized polymers.
The results of the polymerization showed that the RAFT polymerizations could be well controlled using DDABE
as the RAFT agent. Number-average molecular weight (Mn,GPC) increased linearly
with monomer conversion, and molecular weight distributions were relatively narrow (PDI<
1.50). The results of chain-extension reaction, 1H NMR spectra and UV/Vis
spectra confirmed that most of the polymers chains were end-capped by the functional triphenylamine
(TPA) groups. The effect of feed molar ratios of St/DDABE/AIBN on polymerization was investigated. 相似文献
29.
Jiang Minhong Gu Zhengfei Cheng Gang 《中国稀土学报(英文版)》2005,23(6):723-723
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC. 相似文献
30.
中央空调系统由制冷主机房、水子系统、风子系统以及楼宇自控(BA)等部分组成。制冷主机房是中央空调系统的心脏部分,它是由若干台制冷主机,一次冷冻水子系统,二次冷冻水子系统、冷却水子系统、冷却塔、控制柜等组成。它的运行状况直接关系到中央空调系统的能耗,本文将叙述新锦江大酒店制冷主机房建设中的几点节能措施。 相似文献