全文获取类型
收费全文 | 97265篇 |
免费 | 7374篇 |
国内免费 | 3431篇 |
专业分类
电工技术 | 4465篇 |
技术理论 | 2篇 |
综合类 | 4523篇 |
化学工业 | 16680篇 |
金属工艺 | 4427篇 |
机械仪表 | 4998篇 |
建筑科学 | 7066篇 |
矿业工程 | 1996篇 |
能源动力 | 2683篇 |
轻工业 | 7127篇 |
水利工程 | 1819篇 |
石油天然气 | 3229篇 |
武器工业 | 624篇 |
无线电 | 10106篇 |
一般工业技术 | 12846篇 |
冶金工业 | 9295篇 |
原子能技术 | 985篇 |
自动化技术 | 15199篇 |
出版年
2024年 | 316篇 |
2023年 | 1358篇 |
2022年 | 2646篇 |
2021年 | 3625篇 |
2020年 | 2693篇 |
2019年 | 2369篇 |
2018年 | 2603篇 |
2017年 | 2904篇 |
2016年 | 2773篇 |
2015年 | 3597篇 |
2014年 | 4526篇 |
2013年 | 6503篇 |
2012年 | 6076篇 |
2011年 | 6976篇 |
2010年 | 5928篇 |
2009年 | 5708篇 |
2008年 | 5867篇 |
2007年 | 5376篇 |
2006年 | 4898篇 |
2005年 | 4095篇 |
2004年 | 2878篇 |
2003年 | 2485篇 |
2002年 | 2326篇 |
2001年 | 1865篇 |
2000年 | 1535篇 |
1999年 | 1567篇 |
1998年 | 1380篇 |
1997年 | 1234篇 |
1996年 | 1170篇 |
1995年 | 1132篇 |
1994年 | 969篇 |
1993年 | 866篇 |
1992年 | 741篇 |
1991年 | 505篇 |
1990年 | 564篇 |
1989年 | 506篇 |
1988年 | 415篇 |
1987年 | 414篇 |
1986年 | 363篇 |
1985年 | 451篇 |
1984年 | 441篇 |
1983年 | 345篇 |
1982年 | 316篇 |
1981年 | 297篇 |
1980年 | 290篇 |
1979年 | 284篇 |
1978年 | 249篇 |
1977年 | 228篇 |
1976年 | 210篇 |
1975年 | 196篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
11.
Yang C.W. Fang Y.K. Lin C.S. Tsair Y.S. Chen S.M. Wang W.D. Wang M.F. Cheng J.Y. Chen C.H. Yao L.G. Chen S.C. Liang M.S. 《Electronics letters》2003,39(21):1499-1501
A novel technique to form high-K dielectric of HfSiON by doping base oxide with Hf and nitridation with NH/sub 3/, sequentially, is proposed. The HfSiON gate dielectric demonstrates excellent device performances such as only 10% degradation of saturation drain current and almost 45 times of magnitude reduction in gate leakage compared with conventional SiO/sub 2/ gate at the approximately same equivalent oxide thickness. Additionally, negligible flatband voltage shift is achieved with this technique. Time-dependent dielectric breakdown tests indicate that the lifetime of HfSiON is longer than 10 years at V/sub dd/=2 V. 相似文献
12.
13.
14.
A.S. Fomichev I. David S.M. Lukyanov Yu.E. Penionzhkevich N.K. Skobelev O.B. Tarasov 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1994,350(3):605-607
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval. 相似文献
15.
14 medicated hypertensive, 15 nonmedicated mild hypertensive, 39 normotensive, and 13 hypotensive adults participated in a 1–2 hr laboratory experiment that assessed each S's symptoms, moods, and estimates of systolic blood pressure (SBP) relative to actual SBP levels. Several self-reports and autonomic measures were collected during and after each of 22 tasks. Within-S correlations indicated that all Ss could estimate SBP at levels greater than chance. Further, 68% of the Ss evidenced at least 1 significant symptom–SBP correlation. Although medicated hypertensives believed they could estimate their BP more accurately than other groups, they were actually no more accurate than the other Ss. They also evidenced far fewer empirically derived symptom–SBP and emotion–SBP correlations than any other group. Overall, blood pressure (BP) beliefs were largely inaccurate. If these erroneous beliefs can be eliminated, Ss may be able to estimate BP fluctuations more accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
Lewis Gloria J.; Greenburg Sharon L.; Hatch David B. 《Canadian Metallurgical Quarterly》1988,19(1):81
We report the results of the first national survey of psychologists in private practice regarding their participation in peer consultation groups. The sample (71% return) was drawn from 800 randomly selected psychologists listed in the National Register of Health Service Providers in Psychology. We found that 23% of the sample currently belonged to peer consultation groups, and 24% had belonged in the past. Of those not currently in groups, 61% expressed the desire to belong if one were available. There were virtually no significant demographic differences between current members and nonmembers. We examined the following group characteristics: formation, length of existence, size, membership, leadership, theoretical orientation, range of experience, time and place, content, and group process. Groups tended to be small, informal, and leaderless; however, we found great variation among groups on all dimensions. Findings also showed a high degree of satisfaction with membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
18.
心电地图仪中工频干扰的一种滤除方法 总被引:1,自引:0,他引:1
在心电地图仪中记录到的体表心电信号往往由于电磁的影响而引进工频干扰.基于体表心电信号中工频干扰的特点,作者提出了一种滤除工频干扰的方法,即就单独—胸导联信号通过提高频谱的分辨率来估计工频干扰的频率;基于最小均方误差准则来估计各导联信号中工频干扰的幅度和相位。文中还给出了该算法的流程图和滤波性能分析。模拟结果表明了该算法的有效性。应用该算法对心电地图仪中的工频干扰进行对消,取得了满意的结果。 相似文献
19.
Control law design for rotorcraft fly-by-wire systems normally attempts to decouple the angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds should be adopted. Moreover, because of the large changes that occur in the aircraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be ‘robust’. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique minimizes cross-coupling given an anticipated set of parameter variations for the range of flight conditions of concern. Results are presented in this paper of an analysis of the pitch/roll coupling of the UH-60 Black Hawk helicopter in near-hovering flight. A robust crossfeed is designed that shows significant improvement in decoupling perfomance and robustness over the fixed-gain or single point dynamic compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant precompensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft. 相似文献
20.