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   1037篇
  免费   40篇
电工技术   12篇
综合类   1篇
化学工业   359篇
金属工艺   39篇
机械仪表   18篇
建筑科学   12篇
矿业工程   1篇
能源动力   18篇
轻工业   68篇
水利工程   4篇
石油天然气   2篇
无线电   86篇
一般工业技术   129篇
冶金工业   183篇
自动化技术   145篇
  2023年   10篇
  2022年   69篇
  2021年   107篇
  2020年   33篇
  2019年   20篇
  2018年   28篇
  2017年   25篇
  2016年   37篇
  2015年   23篇
  2014年   43篇
  2013年   75篇
  2012年   39篇
  2011年   51篇
  2010年   36篇
  2009年   41篇
  2008年   32篇
  2007年   33篇
  2006年   32篇
  2005年   25篇
  2004年   21篇
  2003年   12篇
  2002年   16篇
  2001年   6篇
  2000年   9篇
  1999年   18篇
  1998年   28篇
  1997年   28篇
  1996年   17篇
  1995年   12篇
  1994年   7篇
  1993年   16篇
  1992年   6篇
  1991年   7篇
  1990年   10篇
  1989年   7篇
  1988年   7篇
  1987年   6篇
  1985年   10篇
  1984年   5篇
  1983年   9篇
  1982年   8篇
  1981年   5篇
  1980年   3篇
  1978年   5篇
  1977年   3篇
  1976年   4篇
  1975年   5篇
  1973年   4篇
  1969年   3篇
  1967年   4篇
排序方式: 共有1077条查询结果,搜索用时 15 毫秒
101.
We studied the effect of inhaled nitric oxide (NO) on 80 patients who had undergone cardiac surgery in our center. The indications for receiving NO inhalation and the number of patients were as follows: Pp/Ps > 0.5 for pulmonary hypertension (PH) (n = 32; 21 children and 11 adults), severe PH crisis (n = 9), high pulmonary vascular tone (Glenn pressure more than 18 mm Hg after bidirectional Glenn operation) or arterial oxygen saturation (SaO2) less than 70% despite an FiO2 of 1.0 after Blalock-Taussig shunt (n = 6), mean pulmonary artery pressure (PAP) > 15 mm Hg and transpulmonary gradient (TPG) (mean PAP - left atrial pressure [LAP]) > 8 mm Hg after Fontan-type operation (n = 18), elevated pulmonary vascular tone (mean PAP > 30 mm Hg and left ventricular assist system [LVAS] flow rate < 2.5 L/min/m2) in patients with LVAS (n = 3), and impaired oxygenation (PaO2/FiO2 < 100 under positive end-expiratory pressure [PEEP] > 5 cm H2O) (n = 12). Low dose inhaled NO (10 ppm) had the following effects. In adult PH patients, it significantly reduced the mean PAP (from 37.3 to 27.0 mm Hg; average values are given) and increased the mean systemic arterial pressure (SAP) (64.7 to 75.3 mm Hg). In infant PH patients, it increased the mean SAP (51.8 to 56.1 mm Hg). In patients with a PH crisis, it significantly reduced the central venous pressure (CVP) (13.3 to 8.8 mm Hg) while increasing both the mean SAP (49.4 to 57.9 mm Hg) and PaO2/FiO2 (135 to 206). In patients after a Fontan-type operation, it significantly reduced the mean PAP (16.8 to 13.8 mm Hg) and TPG (9.5 to 5.8 mm Hg). In patients under LVAS, it reduced the CVP (11.7 to 8.0 mm Hg) and mean PAP (32.0 to 24.7 mm Hg). In impaired oxygenation patients, PaO2/FiO2 was increased (75 to 106). Sixty-five patients were all followed for 2.0-4.3 years (average, 3.1 years). All 65 patients remained free from oxygen requirement, and possible chronic adverse effects including the occurrence of malignant tumors or chronic inflammation in the respiratory tract were not observed.  相似文献   
102.
This study examined relationships between dissociative symptoms experienced in the immediate aftermath of the Oakland/Berkeley firestorm and contact with the fire, life events, demographic variables, and actions taken after learning about the fire. One hundred eighty-seven participants completed self-report measures about their experiences during and immediately following the fire. Dissociative symptoms were significantly related to contact with the fire, sex, and stressful life events. Also, dissociative symptoms were significantly related to engaging in certain activities, such as trying to get closer to the fire and going into blocked-off areas and crossing police barricades. These results suggest that dissociative symptoms may merit special attention in intervention focusing on the immediate aftermath of disaster.  相似文献   
103.
Experimental and theoretical analysis of the influence of the lubricant on the temperature distribution in the tool during forging is presented. Finite element solution of the general diffusion equation is used to calculate the heat transfer contact between the die and the hot workpiece and during the interpass times. The results of calculations are compared with the results of measurements carried out using thermocouples inserted in the die. Two ways of modelling heat transfer through the contact surface are considered. The first treats a lubricant as a separate layer with the relevant thermal properties. The second assumes a temperature discontinuity at the interface and introduces the heat transfer coefficient. Insulating properties of various lubricants are compared. White-water lubricant shows the best insulating properties. The values of the heat transfer coefficient obtained from the inverse analysis vary from 2600 (without lubrication) to 1500 W/m2K (white lubricant).  相似文献   
104.
Extraction of arsenic(III) and arsenic(V) from sulfuric acid solution was studied. Cyanex® 923, Cyanex® 925, dialkyldithiophosphinic acids (Cyanex® 301), hydrophobic glycol (2‐ethylhexane‐1,3‐diol), and hydroxamic acids were used as extractants. The efficiency of extraction depended on extractant, diluent, valency of arsenic, and sulfuric acid concentration. Acidic reagents extracted As(III) better than As(V), while the opposite order of extraction efficiency was observed for the solvating extractants. The use of an aromatic diluent (toluene) was preferred. Toluene was found to be a better diluent for the Cyanex® 923 and Cyanex® 925 than Exxsol D 220/230 and octane. In the case of neo‐decanohydroxamic acids, the type of diluent had no significant effect on extraction of arsenic. The extraction of both As(III) and As(V) increased when the concentration of the sulfuric acid in the feed increased. The co‐extraction of sulfuric acid was observed. The extraction with hydroxamic acids was significantly slower in comparison to the extraction with other reagents. Extractant: arsenic species: sulfuric acid molar ratios were determined and they confirmed the composition of extracted species. Copyright © 2003 Society of Chemical Industry  相似文献   
105.
106.
107.
The systematic modification of a nickel–titanium-alloy by annealing in a complex gas atmosphere was investigated. A mixture of HCl and H2O in inert argon was chosen. The reaction kinetics was investigated at 600 °C, 700 °C and 800 °C. The reaction kinetics displayed a significant dependence on the temperature. It was monitored by means of a thermogravimetric balance that showed a quasi-parabolic scale growth at 600 °C, a paralinear or so called Tedmon kinetic at 700 °C with a distinct weight maximum after about 35 h, and finally a linear evaporation kinetic at 800 °C. This behaviour is attributed to the concurrent reactions of oxidation, chloridation and evaporation of corrosion products. The kinetics of these reactions is different for the two alloying elements and with respect to the equiatomic composition they are coupled to each other. Cross sections prove that a stochiometric titanium depletion is achieved leading to the formation of a Ni3Ti layer (d = 50 μm) which is in turn covered by a pure titanium oxide layer (d = 40 μm). The applicability of this technique for tailored surfaces with a high degree of biocompatibility is discussed.  相似文献   
108.
Specially designed B‐ring‐modified cobalamin derivatives were synthesized and tested as potential activators of soluble guanylyl cyclase (sGC). Herein, we disclose the influence of substituents at the c‐ and d‐positions in hydrophilic and hydrophobic cobyrinic acid derivatives on their capacities to activate sGC. The presence of the amide group at c‐/d‐position in cobyrinic acid derivatives strongly influence the level of sGC activation. Removal of the d‐position altogether has a profound effect for hydrophobic compounds. In contrast, little differences were observed in hydrophilic ones.  相似文献   
109.
110.
In this paper a numerically efficient method for designing a nearly optimal variable fractional delay (VFD) filter based on a simple and well-known window method is presented. In the proposed method a single window extracted from the optimal filter with fixed fractional delay (FD) is divided into even and odd part. Subsequently, the odd part is discarded and symmetric even part of the extracted window is used to design a family of nearly optimal filters with varying FD. In addition to window extraction, the proposed approach requires filter gain correction which is dependent on the desired FD. Optimum values of the gain correction factor as well as the extracted window can be computed beforehand, which allows us to design a nearly optimal FD filter with arbitrary FD at low numerical costs during runtime. On the basis of the proposed filter design method, the universal structure of VFD filter allowing for change of filter type and length has been proposed. In the paper, three FD filter optimality criteria are considered, which are maximal flatness, Chebyshev (minimax), and least squares.  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