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   382篇
  免费   5篇
  国内免费   2篇
电工技术   23篇
化学工业   94篇
金属工艺   8篇
机械仪表   14篇
建筑科学   2篇
能源动力   7篇
轻工业   35篇
水利工程   4篇
无线电   15篇
一般工业技术   81篇
冶金工业   51篇
原子能技术   21篇
自动化技术   34篇
  2023年   1篇
  2022年   5篇
  2021年   10篇
  2020年   3篇
  2019年   4篇
  2018年   2篇
  2017年   2篇
  2016年   9篇
  2015年   5篇
  2014年   5篇
  2013年   18篇
  2012年   19篇
  2011年   21篇
  2010年   8篇
  2009年   13篇
  2008年   15篇
  2007年   15篇
  2006年   11篇
  2005年   14篇
  2004年   11篇
  2003年   14篇
  2002年   8篇
  2001年   6篇
  2000年   6篇
  1999年   15篇
  1998年   20篇
  1997年   13篇
  1996年   19篇
  1995年   5篇
  1994年   14篇
  1993年   15篇
  1992年   5篇
  1991年   4篇
  1990年   8篇
  1989年   5篇
  1988年   3篇
  1987年   5篇
  1986年   3篇
  1985年   3篇
  1984年   6篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1979年   4篇
  1978年   3篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
排序方式: 共有389条查询结果,搜索用时 15 毫秒
1.
2.
We present the case of a patient in whom hypotension, sudden cardiopulmonary arrest, and coma developed after a massive dose of a seemingly harmless cathartic agent. The diagnosis of hypermagnesemia was made 9 hours after the patient's admission, when the serum magnesium concentration was 21.7 mg/dL (8.9 mmol/L). The patient's condition improved with IV calcium, saline solution infusion, and cardiorespiratory support. The elimination half-life of magnesium in this case was 27.7 hours. Few cases have been reported in which patients have survived with serum levels greater than 18 mg/dL (7.4 mmol/L). This case provides evidence that hypermagnesemia may occur in patients with normal kidney function. The diagnosis of hypermagnesemia should be considered in patients who present with symptoms of hyporeflexia, lethargy, refractory hypotension, shock, prolonged QT interval, respiratory depression, or cardiac arrest.  相似文献   
3.
4.
In the drying of coated films with dispersed pigments, such as floppy disks, the structure of the film is formed during the drying process and depends on the drying condition. It is important to understand the structure formation during drying for the design of the dryer and die better quality of the product. We measured die drying characteristics of the film and determined the structure of dried film experimentally. A qualitative model for the structure formation during drying of the coated film is suggested.  相似文献   
5.
6.
The behaviour of copper ions in low thermal expansion glass-ceramics prepared from Cu2O · Al2O3 ·nSiO2 glasses, or in-spodumene type Cu2O · Ae2O3 ·nSiO2 crystals included in the glass-ceramics on heating in air was investigated. On hewing at 300 to 500° C, the copper ions behaved as in the corresponding glasses. Cuprous ions in the glass-ceramics or-spondumene type crystals were oxidized into the cupric state, and at the same time an equal amount of cuprous ions to those oxidized were expelled out of the specimen for the requirement of electrical charge neutrality and then reacted with oxygen to form CuO on the surface. The oxidation of cuprous ions and the decrease of the copper content of the-spondumene type crystals brought about a considerable decrease in the lattice spooings.  相似文献   
7.
Summary Polysilanes with an optically active alkoxy group, i.e., (S)-(+)-2-butoxy, (R)-(-)-2-butoxy, (S)-(-)-2-methyl-1-butoxy, and (S)-(+)-3,7-dimethyl-1-octoxy, at the terminal positions, the chiral carbon centers of which were located at the α, β, and γ positions relative to the oxygen, respectively, were prepared, and the effect of the position of chiral center of the terminal optically active group on the induction of optical activity in polysilanes was investigated. The circular dichroism (CD) spectra of these polymers showed positive Cotton signals around 340 nm at temperatures below -20 °C, but the intensities were small, indicating that the optically active groups at the terminal positions have some ability, albeit small, to induce optical activity to the polysilanes. Further, the optically active (S)-(+)-2-butoxy and (R)-(-)-2-butoxy groups did not control the helical sense direction of the polymers, despite the different chiral stimuli from the 2-butoxy groups introduced to the terminal positions. To control the helical structure of polysilanes by the use of optically active terminal groups, appropriate optically active groups are required.  相似文献   
8.
This paper describes relationships between characteristics of a magnetically anisotropic slot wedge and voltage higher harmonics in an ac exciting synchronous generator terminal due to permeance ripple caused by an open-slot-type rotor. From the relationships obtained, practical guidelines were formulated for machine designs applying the magnetically anisotropic slot wedge. The results are as follows.
  • 1 (1) Equivalent permeability of the magnetically anisotropic slot wedge became isotropic wedge permeability for air-gap flux ripple.
  • 2 (2) Two ways were identified to reduce voltage-higher harmonics by using the slot wedges.
  • 3 (3) The level of leakage flux passing through the anisotropic slot wedge was determined only by its permeability in the width direction.
  • 4 (4) Effectiveness of the magnetic anisotropic slot wedges inserted into the stator slots was verified from experimental results using a model machine of the open- slot-type rotor.
  相似文献   
9.
This paper presents an experimental demonstration to determine electron temperature (T(e)) with unknown spectral sensitivity (transmissivity) in a Thomson scattering system. In this method, a double-pass scattering configuration is used and the scattered lights from each pass (with different scattering angles) are measured separately. T(e) can be determined from the ratio of the signal intensities without knowing a real chromatic dependence in the sensitivity. Note that the wavelength range for each spectral channel must be known. This method was applied to the TST-2 Thomson scattering system. As a result, T(e) measured from the ratio (T(e,r)) and T(e) measured from a standard method (T(e,s)) showed a good agreement with <∣T(e,r) - T(e,s)∣∕T(e,s)> = 7.3%.  相似文献   
10.
Abstract

Single-walled carbon nanotubes (SWCNT) prepared by a DC-Arc-Discharge and purified by a hydrothermal treatment followed by several steps of procedures including heating, burning, extracting and acid-washing are investigated by a conventional STM technique morphologically and spectroscopically. The electical resistivities of compacted pellets (mats) of SWCNT are measured as a function of temperature in the range from the room-temperature to 1.5K. The behaviors seems to be essentially originated in the metallic nature of individual SWCNT.  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