首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1590457篇
  免费   26533篇
  国内免费   7048篇
电工技术   34774篇
综合类   6429篇
化学工业   275557篇
金属工艺   65811篇
机械仪表   45480篇
建筑科学   47676篇
矿业工程   11615篇
能源动力   50566篇
轻工业   121815篇
水利工程   16137篇
石油天然气   38056篇
武器工业   132篇
无线电   199424篇
一般工业技术   298790篇
冶金工业   203932篇
原子能技术   34347篇
自动化技术   173497篇
  2021年   15699篇
  2020年   12001篇
  2019年   14792篇
  2018年   17927篇
  2017年   17413篇
  2016年   22514篇
  2015年   17622篇
  2014年   28899篇
  2013年   88272篇
  2012年   37742篇
  2011年   51761篇
  2010年   44642篇
  2009年   52686篇
  2008年   47623篇
  2007年   45439篇
  2006年   46214篇
  2005年   41508篇
  2004年   43282篇
  2003年   43058篇
  2002年   41727篇
  2001年   39002篇
  2000年   37197篇
  1999年   37002篇
  1998年   58000篇
  1997年   46853篇
  1996年   40474篇
  1995年   33703篇
  1994年   31229篇
  1993年   31053篇
  1992年   26927篇
  1991年   24156篇
  1990年   24444篇
  1989年   23532篇
  1988年   22130篇
  1987年   20246篇
  1986年   19737篇
  1985年   23088篇
  1984年   22844篇
  1983年   20792篇
  1982年   19563篇
  1981年   19745篇
  1980年   18344篇
  1979年   18826篇
  1978年   18005篇
  1977年   18433篇
  1976年   20446篇
  1975年   16221篇
  1974年   15714篇
  1973年   15832篇
  1972年   13264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
When examined using continuous wave electron paramagnetic resonance and nuclear magnetic resonance spectrometers, the highT c superconductors give rise to intense, low field, ‘non-resonant’ absorption signals in the superconducting state. This phenomenon can be used as a highly sensitive, contactless technique for the detection and characterization of superconductivity even in samples containing only minute amounts of the superconducting phase. Further, it can also be applied to the determination of material parameters of interest such asJ c andH c2 in addition to being a powerful way of distinguishing between weak-link superconductivity and bulk superconductivity. The details of these aspects are discussed.  相似文献   
992.
An instrument is proposed for continuously tracking the Sun and measuring its height by the use of a laser gyrometer as measuring converter. The accuracy in photoelectric sighting on the Sun is improved by greatly reducing the light fluxes to be compared by screening out the central part of the Sun's image in the focal plane. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 7–9, March, 1994.  相似文献   
993.
The authors survey published results on the application of metal diffraction gratings as laser power or energy dividers when the laser beam is split into two approximately equal pans. The normal incidence of laser radiation on metal diffraction gratings of various profiles in the case of three propagating diffraction orders n=0, ±1 is discussed, along with the case of oblique incidence with only two propagating diffraction orders n=0 and n =–1.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 22–26, February, 1994.  相似文献   
994.
A method is given for calculating the monitoring reliability parameters (MRP) for an engineering system with allowance for the drift in the measurement error of the means of measurement (MM). The approach is based on introducing a biased MM error distribution into the traditional formulas for the conditional probabilities of spurious and unobserved failure. The bias at the center of the distribution is determined by the systematic error at the given instant. An example is given to illustrate the performance in MRP calculation.Translated from Izmeritel'naya Tekhnika, No. 1, pp. 12–13, January, 1994.  相似文献   
995.
Multifilament Ag-sheathed BiPbSrCaCuO (2223) superconducting tapes containing 49 filaments were fabricated by the powder-in-tube route and the roll-anneal process. The transport critical current densityJ c was 1.3×104 A cm–2 at 77 K and 7×104 A cm–2 at 4.2 K in self-field. A 12-m-long tape was used to construct superconducting solenoids (50, 28, and 14 mm internal diameters) generating dc fields 380–1070 G at 4.2 K. Measurements of the variation ofJ c with field (0–1.6 T) and bend strain (0–5%) are used to explain the performance of the solenoids. The critical bend strain of tapes was about 1.5%.  相似文献   
996.
997.
998.
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   
999.
Heterostructure Acoustic Charge Transport (HACT) devices have been fabricated with a new nondestructive sense (NDS) electrode structure that provides for the recovery of base-band signals without the use of an integrating capacitor. This electrode structure provides an output signal comprising an RF carrier at the SAW frequency, amplitude modulated by the sampled input signal which has been delayed by a period proportional to the output electrodes distance from the input diode. The output of the NDS electrode structure is subsequently demodulated to provide the base-band signal  相似文献   
1000.
A therapist's theoretical orientation is likely to influence every facet of the therapeutic process. We explore the relationship of therapeutic orientation and self-monitoring style. To test the hypothesis that high self-monitors would be more eclectic than low self-monitors, we surveyed 30 intake therapists at a child guidance center. Results supported the hypothesis; those frequently using more than one orientation had higher self-monitoring scores. Furthermore, self-monitoring correlated negatively with psychoanalytic endorsement, but in a positive direction with behavioral, systems and eclectic endorsements. Results are discussed in terms of training needs of those differing in self-monitoring style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号