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   4949篇
  免费   93篇
  国内免费   7篇
电工技术   174篇
综合类   2篇
化学工业   839篇
金属工艺   114篇
机械仪表   109篇
建筑科学   99篇
矿业工程   1篇
能源动力   102篇
轻工业   395篇
水利工程   26篇
石油天然气   7篇
无线电   522篇
一般工业技术   854篇
冶金工业   1349篇
原子能技术   116篇
自动化技术   340篇
  2023年   17篇
  2022年   34篇
  2021年   71篇
  2020年   43篇
  2019年   47篇
  2018年   57篇
  2017年   41篇
  2016年   67篇
  2015年   42篇
  2014年   83篇
  2013年   225篇
  2012年   126篇
  2011年   203篇
  2010年   136篇
  2009年   168篇
  2008年   173篇
  2007年   148篇
  2006年   164篇
  2005年   139篇
  2004年   135篇
  2003年   149篇
  2002年   131篇
  2001年   99篇
  2000年   90篇
  1999年   138篇
  1998年   493篇
  1997年   341篇
  1996年   254篇
  1995年   135篇
  1994年   131篇
  1993年   144篇
  1992年   61篇
  1991年   58篇
  1990年   60篇
  1989年   54篇
  1988年   49篇
  1987年   32篇
  1986年   53篇
  1985年   58篇
  1984年   39篇
  1983年   41篇
  1982年   39篇
  1981年   44篇
  1980年   40篇
  1979年   27篇
  1978年   17篇
  1977年   28篇
  1976年   48篇
  1975年   13篇
  1973年   13篇
排序方式: 共有5049条查询结果,搜索用时 968 毫秒
61.
Sludge disintegration treatment by using simultaneously ultrasonic irradiation and electrolysis was investigated experimentally. A lab-scale diaphragm cell irradiated with ultrasound at a constant oscillating frequency of 20 kHz was used as a reactor. The batch experiments were carried out under different conditions of electric outputs of the ultrasonic generator, electric current for the electrolysis and different initial SS concentrations. A simultaneous treatment in the cathodic compartment without any chemical doses considerably facilitated the sludge solubilization, compared to the sonication alone. An increase in the electric current up to 400 mA under a constant ultrasonic density decreased the specific energy by 55% within the experimental range. The specific energy consumption was also reduced when the initial SS concentration increased. In addition, before carrying out the simultaneous treatment, a brief electrolysis was effective for further reduction of the specific energy and the acceleration of soluble COD generation.  相似文献   
62.
Changes in thermomechanical behavior with structural relaxation taking place in epoxy glasses were studied. Differential scanning calorimetry measurements and thermostimulated strain recovery tests were performed for specimens deformed and then aged under fixed strain. In the course of heating, the specimens started to absorb thermal energy, whereas plastic strain was still stable. At higher temperatures, plastic strain started recovery, which was accompanied by exothermic behavior of the specimen. With an increase in the aging duration, the endothermic peak signified and moved to a higher temperature. These results indicated that the longer the aging duration was, the harder the plastic strain and strain energy were frozen in the glassy structure. This freeze‐strain phenomenon was observed for crosslinked epoxy glass, as well as polymeric glasses with linear molecular structures, aged under strain. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   
63.
Roles of the JAK-STAT system in signal transduction via cytokine receptors   总被引:1,自引:0,他引:1  
JAK-STAT signaling pathways are known to play an essential role in the specific activation of interferon-inducible genes. Many cytokines interacting with the cytokine receptor superfamily also appear to activate these pathways. Recent evidence indicates that JAKs play an essential role(s) in cytokine receptor signaling, including both specific pathways linked to STATs and general pathways regulating cell growth and functions.  相似文献   
64.
BACKGROUND: The mechanism of ventricular tachycardia (VT) after correction of tetralogy of Fallot (TF) is poorly understood. The purpose of this study was to examine the histopathology of the arrhythmogenic area detected by intraoperative mapping. METHODS AND RESULTS: The patients were three men who underwent radical surgery for TF at age 3, 3, or 5 years, respectively. VT developed at 8, 9, or 11 years, respectively, after surgery, and shock developed during VT in every case. The ECG revealed monomorphic VT in two cases and polymorphic VT in one case. Induction of VT resulted in a wide left-axis deviation-pattern QRS with cycle lengths varying between 260 and 330 milliseconds. The VT origin was identified at the right ventricular outflow tract (RVOT). A radical operation was performed with the patient under cardiopulmonary bypass. On epicardial mapping, delayed activation of the RVOT was recorded during sinus rhythm, and clockwise circus movement of the macroreentry current during VT on the right ventricular free wall was documented in each case. The VTs were treated successfully by surgical resection and cryoablation of the myocardium. In every patient, histology of the myocardial specimens showed degeneration, adiposis, fibrosis, inflammatory cell infiltration, and scattered myocyte islets. These lesions corresponded anatomically to the area of myocardium in which delayed activation was evident during epicardial mapping. CONCLUSIONS: The results of this study indicate that patients with VT after radical correction of the TF have abnormal histopathological findings at the site of the prior right ventriculotomy scar. These lesions were noted within the region of delayed activation found during epicardial mapping and were found to be a part of the reentrant circuit.  相似文献   
65.
2 mol% Y2O3-ZrO2 polycrystals were annealed in water and under vacuum to highlight the effect of the presence of H2O on the low-temperature degradation transformation. The specimen surfaces with monoclinic phases transformed during annealing in the different environments were analyzed by X-ray photoelectron spectroscopy with special interest on the electron binding energy change of the constituent ions of the 2 mol% Y2O3-ZrO2 ceramics after the degradation transformation. It was found that no change occurred for the electron-bonding energies of core levels of zirconium ions after the transformation, whereas Y-OH bonds were formed during annealing in water. This result suggested a possibility that the preferred hydration of yttrium took place at the surface of Y2O3-partially-stabilized ZrO2, which is likely to be the reason for the low-temperature degradation accelerated by the presence of H2O.  相似文献   
66.
67.
We attempt to determine the utility of CERAD in detecting early Alzheimer's disease (AD). CERAD battery was administered to a group of 14 control subjects, 12 patients with possible dementia prodromes and to patients with Alzheimer's disease stratified according to severity (16 mild, 8 moderate). Other measures as some subtest of the Wechsler memory scale and the Rey Complex Figure Test were also applied. Delayed recall as well as logical memory of Wechsler memory scale were found to be the best discriminators for detecting very mild cases of AD (Prodromes) (p < 0.05). None of the memory test proved of value in staging the disorder. Visuospatial functions are better determinants of the progression of the illness. Fluency also distinguish between control subjects and very mild cases. These findings suggest that delayed recall memory and probably executive function are the most useful and sensitive indicators of Alzheimer's disease.  相似文献   
68.
69.
70.
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