全文获取类型
收费全文 | 35250篇 |
免费 | 3610篇 |
国内免费 | 1484篇 |
专业分类
电工技术 | 1814篇 |
技术理论 | 2篇 |
综合类 | 2002篇 |
化学工业 | 6726篇 |
金属工艺 | 1881篇 |
机械仪表 | 2193篇 |
建筑科学 | 2059篇 |
矿业工程 | 684篇 |
能源动力 | 1349篇 |
轻工业 | 3112篇 |
水利工程 | 629篇 |
石油天然气 | 1424篇 |
武器工业 | 193篇 |
无线电 | 4505篇 |
一般工业技术 | 5164篇 |
冶金工业 | 1454篇 |
原子能技术 | 449篇 |
自动化技术 | 4704篇 |
出版年
2024年 | 172篇 |
2023年 | 667篇 |
2022年 | 1089篇 |
2021年 | 1433篇 |
2020年 | 1093篇 |
2019年 | 1105篇 |
2018年 | 1209篇 |
2017年 | 1239篇 |
2016年 | 1395篇 |
2015年 | 1434篇 |
2014年 | 1855篇 |
2013年 | 2170篇 |
2012年 | 2315篇 |
2011年 | 2641篇 |
2010年 | 2145篇 |
2009年 | 2019篇 |
2008年 | 1923篇 |
2007年 | 1837篇 |
2006年 | 1700篇 |
2005年 | 1459篇 |
2004年 | 1124篇 |
2003年 | 1180篇 |
2002年 | 1342篇 |
2001年 | 1226篇 |
2000年 | 847篇 |
1999年 | 764篇 |
1998年 | 564篇 |
1997年 | 454篇 |
1996年 | 429篇 |
1995年 | 351篇 |
1994年 | 228篇 |
1993年 | 185篇 |
1992年 | 166篇 |
1991年 | 117篇 |
1990年 | 91篇 |
1989年 | 82篇 |
1988年 | 65篇 |
1987年 | 52篇 |
1986年 | 42篇 |
1985年 | 23篇 |
1984年 | 17篇 |
1983年 | 11篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Chun Hu Ji Zhao Li G.P. Liu P. Worley E. White J. Kjar R. 《Electron Device Letters, IEEE》1995,16(2):61-63
The effects of the plasma etching process induced gate oxide damages on device's low frequency noise behavior are investigated on MOSFET's fabricated with different field plate perimeter to gate area ratio antennas. Abnormal 1/f noise spectrum with a shoulder centered in the frequency range of 100 and to 1 kHz was frequently observed in small geometry devices, and it is attributable to a nonuniform distribution of oxide traps induced by plasma etching process 相似文献
43.
44.
Kim S. Jeong S. Lee Y.T. Kim D.-H. Lim J.-S. Seo K.-S. Nam S. 《Electronics letters》2002,38(13):622-623
A new ultra-wideband, low-loss and small-size coplanar waveguide (CPW) to coplanar strip (CPS) transition which can be used from DC to 110 GHz is presented. The proposed transition connects CPW with CPS by the reformed air-bridge. Two ground planes of CPW are tied at their ends by a line and the centre of the line is connected to the ground strip of CPS by another line. Owing to the symmetry of the proposed structure, the currents of two ground planes of CPW are combined with the same phase and transferred to the ground strip of CPS. With height of 3 μm, the signal line of CPW passes over two connecting lines and is connected to the signal strip of CPS. For the back-to-back transition structure, insertion loss <1 dB and return loss >15 dB are obtained from 0.5 to 110 GHz 相似文献
45.
A quartz microbalance technique has been used to study the growth of4He and H2 adsorbed on sodium. In contrast to cesium, adsorption of4He and H2 do occur on a sodium surface. 相似文献
46.
应用色谱—质谱(GC-MS)及裂解色谱-质谱(PGC-MS)测定了乙烯基三甲基硅烷等离子体聚合反应中的气体冷凝物及聚合物,研究推导了等离子体聚合反应历程。单体在气相中被电子撞击,然后扩散到基底,在基底发生链增长和链终止反应。 相似文献
47.
In conformity with the principle of Design for Manufacture,feature-based design strate-(?)es have been developed.As the“feature”is relevant to the“macro process plan”and“macro NCprograms”,obviously,“feature”is beyond the power of conventional solid modellers.Neverthe-less,substantial breakthrough has not been made in the solid modeling field,except“feature at-taching”or“feature recognizing”methods have been taken on.In this paper,the theory,concepts,system architecture,and algorithm principles of solid modeling tool system have beenrepresented.The practice of Feature Solid Modeling Tool System (FSMTS) developed atHuazhong University has proved that the tool may be a new foundation of Feature-Based Design. 相似文献
48.
叠后地震剖面的线性化波阻抗反演 总被引:4,自引:0,他引:4
本文提出了由井旁道出发逐道进行的叠后地震剖面的线性化波阻抗反演方法。每一道反演采用逐次线性化对波阻抗进行修正,反演的纵向分辨率为一个采样时间间隔,并以合成记录道与实际地震道的相似系数作为迭代收敛准则,已处理的地震道波阻抗作为下一道反演初始值。实际资料处理表明,该方法具有较高的分辨率和运算速度快的优点。 相似文献
49.
50.
Using measurements collected at network monitors to infer network conditions is a promising approach for network-centric monitoring. In this context, an important question arises: given the number and locations of network monitors, how much network management resources (e.g., the number of measurements) are needed to obtain an accurate estimate of network states? We define the scalability of measurement-based network monitoring as the growth rate of the number of measurements required for accurate network monitoring/inference with respect to the size of a network. We develop a framework for investigating the scalability in the context of multicast inference with the monitors at the edges of a network. In such a framework, network monitoring/inference can be formulated as probability density estimation of network states. The growth rate is characterized through the sample complexity, which is the number of measurements needed to accurately estimate the density. The missing data framework is introduced to estimate the growth rate, where the missing data reflect unavailable measurements at the unobservable nodes without resident monitors, and the underlying nodal packet losses. We show that when the missing information is mainly due to the number of unobservable nodes, the number of measurements needed grows linearly with the size of the network, and the measurement-based inference approach is, thus, scalable. When the missing information is mainly due to the underlying nodal packet losses, the number of measurements needed grows faster than linear with the size of the network, and the measurement-based inference approach is, thus, not scalable. Our results provide guidelines for accessing feasibility of the measurement-based inference approach, and the number of probes required. We give numerical examples to illustrate some of our results 相似文献