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   3557篇
  免费   20篇
  国内免费   1篇
电工技术   12篇
综合类   2篇
化学工业   56篇
金属工艺   3篇
机械仪表   18篇
建筑科学   31篇
能源动力   6篇
轻工业   24篇
水利工程   5篇
石油天然气   2篇
无线电   74篇
一般工业技术   63篇
冶金工业   3210篇
原子能技术   2篇
自动化技术   70篇
  2022年   4篇
  2021年   3篇
  2020年   4篇
  2018年   12篇
  2017年   4篇
  2016年   4篇
  2015年   14篇
  2014年   6篇
  2013年   22篇
  2012年   18篇
  2011年   17篇
  2010年   19篇
  2009年   15篇
  2008年   24篇
  2007年   21篇
  2006年   20篇
  2005年   15篇
  2004年   15篇
  2003年   19篇
  2002年   10篇
  2001年   9篇
  2000年   18篇
  1999年   130篇
  1998年   1045篇
  1997年   612篇
  1996年   400篇
  1995年   187篇
  1994年   193篇
  1993年   186篇
  1992年   24篇
  1991年   17篇
  1990年   28篇
  1989年   25篇
  1988年   28篇
  1987年   20篇
  1986年   16篇
  1985年   23篇
  1984年   2篇
  1983年   7篇
  1982年   25篇
  1981年   19篇
  1980年   23篇
  1979年   2篇
  1978年   9篇
  1977年   88篇
  1976年   163篇
  1975年   5篇
  1973年   2篇
  1972年   2篇
  1965年   2篇
排序方式: 共有3578条查询结果,搜索用时 715 毫秒
1.
2.
3.
BACKGROUND: An increasing demand for cardiac allografts for the treatment of end-stage cardiac failure has led to a shift in the traditional views about donor criteria. The use of allografts exposed to high concentrations of carbon monoxide is still under discussion. The current literature on this topic is contradictory. We describe our experience with orthotopic cardiac transplantation, using cardiac allografts after carbon monoxide poisoning. METHODS: Between March 13, 1989 and August 1, 1996, 770 orthotopic heart transplantations were performed in our center. Within this period, we accepted five cardiac allografts from brain-dead, carbon monoxide-poisoned donors. Donor history showed carbon monoxide intoxication in all cases. At the time of organ explantation, donor hemodynamic parameters were feeble in all patients. RESULTS: The postoperative course was uneventful in three of the five recipients. The overall 3-year survival rate in this small group is 40%. Induction therapy or rescue therapy with mono/polyclonal antibodies was not necessary. Myocardial right-ventricular biopsies did not show any specific signs of carbon monoxide poisoning. CONCLUSIONS: In our opinion, cardiac allografts from donors exposed to carbon monoxide can be transplanted successfully in infants and adults, if there are no signs of severe hemodynamic dysfunction in the presence of a normal central venous pressure and low-dose support with catecholamines and there are no electrocardiographic changes in combination with elevated transaminase. With extended donor criteria, the hearts of carbon monoxide-poisoned victims could increase the number of suitable organs and lower the death rate of patients on the United Network for Organ Sharing and Eurotransplant International Foundation waiting lists.  相似文献   
4.
5.
The purpose of this study was to identify the optimal knot construction for interrupted dermal sutures. A synthetic braided absorbable suture, sizes 3-0 and 5-0, was selected for this evaluation. With reproducible mechanical performance tests, we determined that the construction of secure knots without ears required one additional throw as compared with secure knots with 3-mm ears. The direction of applied tension did not alter knot security, with the exception of granny knots, which required an extra throw when tension was applied parallel to the suture loop. Because interrupted dermal knot construction is accomplished without knot ears and with an applied tension parallel to the wound, one additional throw must be added to the knot to ensure knot security.  相似文献   
6.
7.
Degenerate oligonucleotide primers were used in a polymerase chain reaction (PCR) to amplify a region of the recA sequence of Streptococcus gordonii Challis. The resulting PCR fragment was cloned into the suicide vector pAM6199 and introduced into strain Challis, giving rise to recombination-deficient strains in which the recA gene was specifically inactivated.  相似文献   
8.
The muscular tissue of the vestibular folds was investigated in plastinated serial sections of 32 normal adult larynges. Three muscular systems could be distinguished. A posterolateral muscle layer was found to be developed at the lateral margin of the posterior part of the vestibular fold. Its fibers extended in a sagittal direction, and their contraction probably resulted in an adduction of the entire tissue of the vestibular fold towards the midline. Within the anterior part of the vestibular fold, an anterolateral muscle sheet was seen to attach to the thyroid cartilage. An anteromedial muscular system consisted of scattered groups of muscle fibers situated medially and dorsally to the laryngeal ventricle and saccule. These fibers were presumed to exert a downward pressure on the vestibular folds, in addition to an adductor function. According to clinical experience, adductor movements of the vestibular folds can be trained, even in cases with a recurrent laryngeal nerve lesion, in order to produce a compensatory voice. Thus, the muscles of the vestibular folds are probably innervated by the superior laryngeal nerve.  相似文献   
9.
10.
We report the growth of highly C-axis orientation of Sr x Ba1−x Nb2O6 (SBN) thin films on p-type (100) Si substrates by using a potassium-substituted SBN template layer with the sol–gel method. The crystallization of SBN thin films was found closely related to the potassium ion doping concentration and the postannealing temperature of the K-SBN template layer. Secondary ion mass spectrometry analysis showed that potassium elements were accumulated at the interface of the template layer and silicon substrate. SBN films postannealed at 750 °C with K-SBN template layer has a smaller full width at half maximum of X-ray rocking curve of 2.45° than that of 5.40° for the pure SBN films. By introducing a template layer, the surface morphologies of SBN films fabricated on silicon substrate were greatly improved.  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