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   5302篇
  免费   110篇
  国内免费   5篇
电工技术   19篇
化学工业   277篇
金属工艺   33篇
机械仪表   69篇
建筑科学   78篇
矿业工程   1篇
能源动力   57篇
轻工业   189篇
水利工程   26篇
石油天然气   2篇
无线电   247篇
一般工业技术   593篇
冶金工业   3608篇
原子能技术   10篇
自动化技术   208篇
  2022年   18篇
  2021年   33篇
  2020年   21篇
  2019年   28篇
  2018年   67篇
  2017年   70篇
  2016年   40篇
  2015年   39篇
  2014年   49篇
  2013年   108篇
  2012年   107篇
  2011年   114篇
  2010年   120篇
  2009年   96篇
  2008年   74篇
  2007年   95篇
  2006年   65篇
  2005年   91篇
  2004年   69篇
  2003年   65篇
  2002年   58篇
  2001年   37篇
  2000年   54篇
  1999年   177篇
  1998年   1100篇
  1997年   665篇
  1996年   436篇
  1995年   213篇
  1994年   215篇
  1993年   214篇
  1992年   47篇
  1991年   27篇
  1990年   43篇
  1989年   53篇
  1988年   37篇
  1987年   35篇
  1986年   35篇
  1985年   38篇
  1984年   18篇
  1983年   16篇
  1982年   30篇
  1981年   29篇
  1980年   39篇
  1979年   14篇
  1978年   21篇
  1977年   109篇
  1976年   194篇
  1975年   20篇
  1973年   11篇
  1969年   8篇
排序方式: 共有5417条查询结果,搜索用时 31 毫秒
1.
Combined photochemical arylation, “nuisance effect” (SNAr) reaction sequences have been employed in the design of small arrays for immediate deployment in medium-throughput X-ray protein–ligand structure determination. Reactions were deliberately allowed to run “out of control” in terms of selectivity; for example the ortho-arylation of 2-phenylpyridine gave five products resulting from mono- and bisarylations combined with SNAr processes. As a result, a number of crystallographic hits against NUDT7, a key peroxisomal CoA ester hydrolase, have been identified.  相似文献   
2.
3.
4.
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   
5.
A high prevalence of epilepsy (up to 1.3%) was observed in an area hyperendemic for onchocerciasis in the province of Bururi, Burundi. Following this observation, epileptics and controls were examined in 2 communes (administrative units) with different endemicity for onchocerciasis. Altogether, onchocerciasis was more frequent in epileptics (81.8%) than in controls from the same households (68.3%; P < 0.05). This difference was more marked in the hyperendemic area. Other possible causes of epilepsy, including cysticercosis, were infrequent (18 possible cases among 110 epileptics). During this survey, 9 epileptics with growth retardation were seen. They showed most characteristics of Nakalanga syndrome, which was described from Uganda. All 9 such cases were suffering from onchocerciasis. These findings give more evidence of a possible association between onchocerciasis and epilepsy, and between onchocerciasis and Nakalanga syndrome.  相似文献   
6.
7.
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   
8.
9.
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   
10.
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   
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