全文获取类型
收费全文 | 6306篇 |
免费 | 545篇 |
国内免费 | 251篇 |
专业分类
电工技术 | 299篇 |
综合类 | 334篇 |
化学工业 | 1005篇 |
金属工艺 | 351篇 |
机械仪表 | 334篇 |
建筑科学 | 441篇 |
矿业工程 | 195篇 |
能源动力 | 150篇 |
轻工业 | 379篇 |
水利工程 | 115篇 |
石油天然气 | 271篇 |
武器工业 | 54篇 |
无线电 | 836篇 |
一般工业技术 | 852篇 |
冶金工业 | 683篇 |
原子能技术 | 58篇 |
自动化技术 | 745篇 |
出版年
2024年 | 40篇 |
2023年 | 112篇 |
2022年 | 228篇 |
2021年 | 302篇 |
2020年 | 189篇 |
2019年 | 170篇 |
2018年 | 190篇 |
2017年 | 213篇 |
2016年 | 180篇 |
2015年 | 258篇 |
2014年 | 285篇 |
2013年 | 336篇 |
2012年 | 353篇 |
2011年 | 400篇 |
2010年 | 361篇 |
2009年 | 328篇 |
2008年 | 350篇 |
2007年 | 282篇 |
2006年 | 287篇 |
2005年 | 206篇 |
2004年 | 149篇 |
2003年 | 144篇 |
2002年 | 120篇 |
2001年 | 125篇 |
2000年 | 134篇 |
1999年 | 162篇 |
1998年 | 247篇 |
1997年 | 164篇 |
1996年 | 119篇 |
1995年 | 79篇 |
1994年 | 77篇 |
1993年 | 65篇 |
1992年 | 37篇 |
1991年 | 32篇 |
1990年 | 26篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 29篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 34篇 |
1956年 | 8篇 |
排序方式: 共有7102条查询结果,搜索用时 31 毫秒
11.
We have fabricated and tested a high-Tc dc-SQUID magnetometer patterned on a YBCO thin film deposited on a SrTiO3 bicrystal substrate. The measurement of noise spectrum at 77 K showed that the magnetometer has a white noise of 333 fT/Hz1/2 without superconducting shield, corresponding to a flux sensitivity of 14.5 μΦ0/Hz1/2. We constructed a test system for eddy current non-destructive evaluation of conducting aluminum plates by using the magnetometer. Flaws over 10 mm below the surface can be clearly identified. By mapping the magnetic field distribution, we can locate the flaw position. The signals caused by flaw were expanded due to the use of double-D type driving coil with a wider central slit. The experimental results confirmed that this test system could operate in a magnetic unshielded environment. 相似文献
12.
石蜡微胶囊中脲醛树脂壁材渗透性的研究 总被引:7,自引:0,他引:7
利用差示扫描量热法研究了石蜡微胶囊中脲醛树脂壁材对水及甲苯的渗透性 ,结果表明 ,水不能透过脲醛树脂壁材 ,而甲苯则易透过脲醛树脂壁材。因此 ,该石蜡微胶囊不能用于芳香族溶剂存在的场合。 相似文献
13.
一种探测二维电磁目标的新方法 总被引:2,自引:0,他引:2
电磁目标的探测对通信而言有着十分重要的意义。本文描述一种收敛迅速、结果准确、抗强随机噪声的探测二维电磁目标的新方法。首先从体等效原理出发得到一个积分方程组,此方程组可求解散射问题。随后,对此方程组求变分,变形后得到散射场变化与介电参数变化之间关系的矩阵方程,即反演方程。文中列举了几个例子,通过数值实验结果证明本法收敛速度快、反演精度高、适应复杂目标的能力强,能抗强随机噪声干扰 相似文献
14.
1. Animal studies have shown that angiotensin II has a biphasic effect on urinary sodium excretion. To examine whether this is also true in man, we studied seven salt-replete male subjects in a single-blind placebo-controlled manner. 2. While undergoing maximum diuresis, subjects were infused with 0, 1, 2, 5 or 10 ng of angiotensin II min-1 kg-1 over 80 min. Subjects were studied while seated, and stood every 20 min for urine collection. 3. Angiotensin II produced a dose-dependent antidiuretic effect. The urine flow rate, in ml/min expressed as the change from baseline with increasing dose of angiotensin, was: +3.4 +/- 1.77, -1.26 +/- 0.49 (P < 0.05), -2.75 +/- 1.23 (P < 0.05), -4.21 +/- 0.82 (P < 0.05) and -6.51 +/- 1.07 (P < 0.01). 4. In contrast, the effect of angiotensin II on sodium excretion showed a flat dose-response curve beyond 5 ng min-1 kg-1. The urinary sodium excretion, in mumol/min expressed as the change from baseline with increasing dose of angiotensin, was: 9.5 +/- 21.2, -18.9 +/- 29.6, -37.0 +/- 11.6 (P < 0.05), -67.7 +/- 19.6 (P < 0.01) and -63.8 +/- 14.3 (P < 0.01). 5. The fractional distal reabsorption of sodium, determined by using the lithium clearance technique, showed a rise with all doses of angiotensin II used and reached statistical significance with the top two doses. 6. Unlike antidiuresis, antinatriuresis after graded doses of angiotensin II in human subjects showed a flat dose-response curve beyond 5 ng min-1 kg-1. Pressor doses of angiotensin II also have a significant effect on the distal tubule in promoting sodium reabsorption. 相似文献
15.
16.
17.
18.
Mesh network resiliency using GMPLS 总被引:4,自引:0,他引:4
Lang J.P. Drake J. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2002,90(9):1559-1564
The generalized multiprotocol label switching (GMPLS) is being developed as the control plane for the evolving photonic network. We describe how GMPLS can be used with mesh networks to provide efficient network resiliency. In particular we examine the key aspects of GMPLS that are used to support protection and restoration. We also study the various protection and restoration techniques, and we highlight the tradeoffs between recovery time and resource redundancy 相似文献
19.
Magnetic induction micromachine-part I: Design and analysis 总被引:1,自引:0,他引:1
Most microscale electric and magnetic machines studied in the last decade lack the power density to support many practical applications. This paper introduces a design for a magnetic induction machine that offers power densities in excess of 200 MW/m/sup 3/ and efficiencies of up to 50%, while providing more than 10 W of mechanical power. This is a substantial performance increase in MEMS electromagnetic machines studied to date. 相似文献
20.
Blair J.D. Correale A. Jr. Cranford H.C. Dombrowski D.A. Erdelyi C.K. Hoffman C.R. Lamphere J.L. Lang K.W. Lee J.K. Mullen J.M. Norman V.R. Oakland S.F. 《Solid-State Circuits, IEEE Journal of》1989,24(6):1647-1655
The authors describe a 9.02×9.02-mm chip built in 1-μm CMOS with two levels of metal and an additional mask level for fabricating capacitors. It contains both analog and digital circuits and has provisions for self-test. The function includes the transmitter, receiver, protocol handler, an microprocessor, as well as interfaces for RAM/ROM storage, IBM PC bus, IBM PS/2 bus, IBM 3174 bus, and Motorola 68000 bus. The physical design terrains are formed by 24K circuits of standard cell gates, a 10K-circuit equivalent hand-honed custom microprocessor, and an analog macro. The chip operates from a single 5-V supply, and the power consumption is 0.8 W nominal at 16 Mb/s. The chip can also be operated at 4 Mb/s 相似文献