全文获取类型
收费全文 | 118314篇 |
免费 | 9794篇 |
国内免费 | 4954篇 |
专业分类
电工技术 | 7074篇 |
技术理论 | 7篇 |
综合类 | 7585篇 |
化学工业 | 20414篇 |
金属工艺 | 6486篇 |
机械仪表 | 7314篇 |
建筑科学 | 9645篇 |
矿业工程 | 3436篇 |
能源动力 | 3533篇 |
轻工业 | 7670篇 |
水利工程 | 2097篇 |
石油天然气 | 7291篇 |
武器工业 | 876篇 |
无线电 | 13415篇 |
一般工业技术 | 14301篇 |
冶金工业 | 5509篇 |
原子能技术 | 1288篇 |
自动化技术 | 15121篇 |
出版年
2024年 | 551篇 |
2023年 | 2031篇 |
2022年 | 3522篇 |
2021年 | 4873篇 |
2020年 | 3735篇 |
2019年 | 3145篇 |
2018年 | 3389篇 |
2017年 | 3917篇 |
2016年 | 3298篇 |
2015年 | 4684篇 |
2014年 | 5709篇 |
2013年 | 6772篇 |
2012年 | 7419篇 |
2011年 | 7974篇 |
2010年 | 6962篇 |
2009年 | 6645篇 |
2008年 | 6437篇 |
2007年 | 6095篇 |
2006年 | 6351篇 |
2005年 | 5519篇 |
2004年 | 3763篇 |
2003年 | 3286篇 |
2002年 | 3077篇 |
2001年 | 2803篇 |
2000年 | 2948篇 |
1999年 | 3160篇 |
1998年 | 2671篇 |
1997年 | 2275篇 |
1996年 | 2098篇 |
1995年 | 1825篇 |
1994年 | 1473篇 |
1993年 | 1056篇 |
1992年 | 860篇 |
1991年 | 677篇 |
1990年 | 491篇 |
1989年 | 436篇 |
1988年 | 353篇 |
1987年 | 245篇 |
1986年 | 167篇 |
1985年 | 97篇 |
1984年 | 65篇 |
1983年 | 49篇 |
1982年 | 64篇 |
1981年 | 39篇 |
1980年 | 35篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1965年 | 3篇 |
1959年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Mei Xuan Xu Wen Guang Liu Yun Lin Guan Zuo Peng Bi Kang De Yao 《Polymer International》1995,38(2):205-209
The phase behavior of a hybrid polymer network (HPN) composed of poly[(propylene glycol maleate)-co-(propylene glycol phthalate)] crosslinked with styrene and polyester–urethane crosslinked with methylene-bis-ortho-chloroaniline was examined. The correlation between phase separation and impact strength of the HPNs is discussed. The composition of HPNs has an effect on their properties. 相似文献
43.
44.
The Uniform Geometrical Theory of Diffraction (UTD) has been successfully used in pattern analysis of airborne dipole antenna on the A-5 fighter in high-frequency region. In the analysis, several canonical problems are investigated first, then the complicated problem is calculated with compiling these canonical problems. The numerical results are compared with the experimental data, and good agreement has been seen. The effectiveness and practicality of the present analysis are thus verified. 相似文献
45.
Bugong Xu 《Automatic Control, IEEE Transactions on》1995,40(5):930-933
A new criterion for delay-independent stability of linear large scale time-delay systems is deduced by employing an improved Razumikhin-type theorem and the m-matrix properties. An illustrative example is given to demonstrate the superiority of the obtained results to those in the literature 相似文献
46.
47.
Xiao Sun Chow M.H.L. Leung F.H.F. Dehong Xu Yousheng Wang Yim-Shu Lee 《Power Electronics, IEEE Transactions on》2002,17(3):305-313
An analogue neural-network controller for UPS inverter applications is presented. The proposed neural-network controller is trained off-line using patterns obtained from a simulated controller, which had an idealized load-current-reference. Simulation results show that the proposed neural-network controller can achieve low total harmonic distortion under nonlinear loading condition and good dynamic responses under transient loading condition. To verify the performance of the proposed NN controller, a hardware inverter with an analogue neural network (NN) controller (using mainly operational amplifiers and resistors) is built. Additionally, for comparison purposes, a PI controller with optimized parameters is built. Experimental results confirm the simulation results and show the superior performance of the NN controller especially under rectifier-type loading condition. Implementing the analogue neural-network controller using programmable integrated circuits is also discussed 相似文献
48.
The copolymer from D ,L -lactide and poly(tetramethyene ether glycol) (PTMG) was prepared in bulk with an isotributyl aluminum–water–phosphoric acid complex catalyst as the initiator and characterized by H-NMR, GPC, and DSC. The effects of the temperature and the amount of PTMG on the polymerization rate and the molecular weight of copolymers were studied. The behavior of the degradation and delivery rate of Levonorgestrel microspheres in vitro was observed. The results show that the degradation and the delivery rate can be controlled by adjusting the molar rate of hydrophilic and hydrophobic segments of the copolymer © 1995 John Wiley & Sons, Inc. 相似文献
49.
两种具有电双稳态的全有机络合物 总被引:9,自引:0,他引:9
首次发现两种在室温下即具有电双稳态的全有机(有机-有机)络合物,分别称为MCA+TCNQ和BBDN+TCNQ。它们可在真空中制备成薄膜,在数伏电压的作用下,从高电阻至低电阻的跃迁时间小于100ns,因此可作为一次写入的存储器材料。根据我国目前最小刻线宽度的水平,可望在1.6cm2的SiO2平面上做出64Mb的存储器。 相似文献
50.
While the current definition of TCP friendliness has enabled a wide variety of traffic control protocols other than TCP, it still considerably restricts the design space of TCP-friendly traffic control protocols. For example, some multimedia streaming applications prefer a smooth sending rate on a time scale of tens of seconds, however, a UDP flow maintaining such a long smoothness time scale is naturally not TCP friendly by the current definition. In this paper, we propose an innovative method to relatively compare the degrees of TCP friendliness of different traffic control protocols, and use it to define a new class of TCP friendliness definitions, called stochastic TCP friendliness (STF). STF greatly expands the design space of TCP-friendly traffic control protocols, while still effectively maintaining the desired fairness of the Internet. To demonstrate the expanded design space, we also develop a new congestion control protocol, called TCP-friendly CBR-Like Rate Control (TFCBR), for multimedia streaming applications which do not require a high sending rate but prefer a smooth sending rate on a time scale of tens of seconds. TFCBR is stochastically TCP friendly, however, it is not TCP friendly by the current definition. 相似文献