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   1518篇
  免费   1篇
  国内免费   1篇
化学工业   3篇
金属工艺   1篇
机械仪表   1篇
建筑科学   1篇
能源动力   9篇
轻工业   1篇
石油天然气   1篇
无线电   3篇
一般工业技术   9篇
冶金工业   1484篇
自动化技术   7篇
  2017年   1篇
  2014年   1篇
  2013年   3篇
  2011年   3篇
  2009年   1篇
  2008年   2篇
  2007年   2篇
  2006年   2篇
  2005年   1篇
  2003年   4篇
  2002年   2篇
  2001年   1篇
  1999年   40篇
  1998年   431篇
  1997年   248篇
  1996年   160篇
  1995年   92篇
  1994年   82篇
  1993年   103篇
  1992年   6篇
  1991年   23篇
  1990年   18篇
  1989年   19篇
  1988年   28篇
  1987年   20篇
  1986年   16篇
  1985年   9篇
  1984年   1篇
  1983年   5篇
  1982年   4篇
  1981年   12篇
  1980年   23篇
  1979年   2篇
  1978年   3篇
  1977年   47篇
  1976年   92篇
  1975年   6篇
  1973年   1篇
  1972年   1篇
  1969年   1篇
  1968年   1篇
  1967年   1篇
  1955年   2篇
排序方式: 共有1520条查询结果,搜索用时 15 毫秒
151.
The topography of primary sensory cortical hand area following a monohemispheric lesion (sudden = stroke; progressive = neoplasm) was investigated in relationship with clinical recovery of sensorimotor deficits. Twenty seven patients with monohemispheric lesions were studied in a clinically stabilized condition. Functional informations from magnetoencephalography (MEG) were integrated with anatomical data from magnetic resonance imaging (MRI). MEG localizations of the neurons firing at early latencies in primary sensory cortex after separate stimulation of median nerve, thumb and little fingers of each hand were carried out. Characteristics of cerebral equivalent current dipoles (ECDs) activated by each contralateral stimulation, the 'hand extension' (i.e., the distance in millimetres between ECDs of first and fifth digits), as well as interhemispheric differences of the tested parameters were investigated. Finally, ECDs' locations were integrated with MRI. Lesions involving cortical (C) or subcortical (s.c.) areas receiving sensory input from the hand were often combined to increase interhemispheric asymmetry of the tested parameters (22% for C and 49% for s.c. lesions). This might be due to an activation of neuronal districts which in the affected hemisphere (AH) differ from those normally activated in the unaffected hemisphere (UH) and in the control population. Moreover, the 'hand extension' was enlarged on the AH--more frequently after a SC lesion--mainly due to a medial shift of the little finger ECD, combined to a tendency of both finger ECDs to shift frontally. After a C lesion, responses from the AH were often stronger than normal. Spatial reorganizations were also seen in the UH (7% of C and 14% of SC lesions). 'Hand extension' in the UH was selectively enlarged for the P30m only when combined with a similar enlargement in the AH. Significant interhemispheric asymmetries due to neuronal reorganization in the AH were associated with worse clinical outcomes compared to patients without asymmetries.  相似文献   
152.
Left ventricular wall motion abnormalities secondary to stress-induced myocardial ischemia can be detected with difficulty by mentally comparing echocardiographic images sequentially recorded on videotape. Digital stress-echocardiography, a combination of ultrasound imaging and digital archiving technologies, at least partially can overcome this problem: the technique is based on reviewing images at rest and after stress (exercise or pharmacological) side by side in dual- or quad-screen digital format, in a synchronized cine-loop, as if obtained simultaneously. This technique however is presently not widely used, due to the high cost of most commercially available systems. We have developed a digital stress-echo system, which is easy to use and relatively inexpensive, running on a Macintosh II personal computer with 8-bit graphics. The 2-D echocardiographic images recorded on videotape are digitized offline using a video digitizing board. The image can be displayed and analyzed using the public domain NIH image software developed by Wayne Rasband, without loss in image quality and resolution, particularly if using Super-VHS videotape. We have made a macro procedure for the montage in a quad-screen format of four digital recorded echocardiographic cardiac cycles of six frames that takes only a little more time than commercially available systems. In conclusion, the use of a personal computer and low-cost software may help to make digital stress-echo techniques more widely feasible in the clinical setting and increase the diagnostic power of the ultrasound technique in the evaluation of patients with known or suspected coronary artery disease.  相似文献   
153.
Transaxillary subpectoral augmentation mammaplasty combines the advantages of an axillary located scar with those of a submuscular pocket. However, according to the classical technique, the caudal extension of the pectoral fascia prevents the prosthesis from filling completely the inferior breast pole, thus creating a double submammary fold and/or an excessive fullness of the superior quadrants. In order to overcome this limit Barnett (1990) proposed to disrupt the caudal extension of the pectoral fascia along with its insertions to the submammary fold, thus allowing the implant to lie in a submuscular plane superiorly and in a subglandular/subcutaneous one inferiorly. In this paper the authors present their clinical experience with this new surgical technique.  相似文献   
154.
Swan-Ganz catheter-induced pulmonary artery (PA) rupture is rare, with an incidence of 0.016 to 0.2 per cent, but it remains the most dreaded complication in the placement of these catheters with a mortality above 50 per cent. We report two cases of PA rupture after catheter placement. Both patients were managed nonoperatively and without any invasive procedure. They both stopped bleeding after the initial episode and were discharged a few days later. We believe that in the absence of high-risk factors, such as pulmonary hypertension and systemic anticoagulation, PA rupture from a Swan-Ganz catheter can be successfully treated by withdrawal of the catheter and supportive care.  相似文献   
155.
The most frequent metabolic cause of myoglobinuria seems to be carnitine palmitoyl-transferase II deficiency. The authors describe a case, trying to explain the peculiarities and the importance, for the prognosis, of the residual enzymatic activity. The genetical etiology of the disease emphasize the role of hygienic behavior and of the L-carnitine as pathogenetic therapy.  相似文献   
156.
157.
158.
Rapid, quantitative, and objective determination of the susceptibilities of human cytomegalovirus (HCMV) clinical isolates to ganciclovir has been assessed by an assay that uses a fluorochrome-labeled monoclonal antibody to an HCMV immediate-early antigen and flow cytometry. Analysis of the ganciclovir susceptibilities of 25 phenotypically characterized clinical isolates by flow cytometry demonstrated that the 50% inhibitory concentrations (IC50s) of ganciclovir for 19 of the isolates were between 1.14 and 6.66 microM, with a mean of 4.32 microM (+/-1.93) (sensitive; IC50 less than 7 microM), the IC50s for 2 isolates were 8.48 and 9.79 microM (partially resistant), and the IC50s for 4 isolates were greater than 96 microM (resistant). Comparative analysis of the drug susceptibilities of these clinical isolates by the plaque reduction assay gave IC50s of less than 6 microM, with a mean of 2.88 microM (+/-1.40) for the 19 drug-sensitive isolates, IC50s of 6 to 8 microM for the partially resistant isolates, and IC50s of greater than 12 microM for the four resistant clinical isolates. Comparison of the IC50s for the drug-susceptible and partially resistant clinical isolates obtained by the flow cytometry assay with the IC50s obtained by the plaque reduction assay showed an acceptable correlation (r2 = 0.473; P = 0.001), suggesting that the flow cytometry assay could substitute for the more labor-intensive, subjective, and time-consuming plaque reduction assay.  相似文献   
159.
160.
GL Saksagansky 《Vacuum》1973,23(6):207-210
A review of the All-Union Conference on High-Vaccum Physics and Technology is presented, which was held on 5–7 October 1971 in Leningrad. The conference was organized by the Vacuum Apparatus and Instrument Committee of the Scientific Technical Society of the USSR Instrument Making Industry. New investigation results concerning vacuum physics and making ultra-high-vacuum apparatus, instruments and equipment were considered.  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