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   1639篇
  免费   2篇
电工技术   1篇
综合类   2篇
化学工业   6篇
金属工艺   1篇
建筑科学   4篇
矿业工程   1篇
轻工业   7篇
无线电   1篇
一般工业技术   1篇
冶金工业   1615篇
自动化技术   2篇
  2022年   1篇
  2015年   3篇
  2014年   2篇
  2013年   2篇
  2010年   1篇
  2009年   3篇
  2008年   2篇
  2006年   5篇
  2005年   1篇
  2004年   1篇
  2003年   4篇
  2000年   1篇
  1999年   54篇
  1998年   500篇
  1997年   301篇
  1996年   192篇
  1995年   105篇
  1994年   69篇
  1993年   94篇
  1992年   12篇
  1991年   22篇
  1990年   17篇
  1989年   11篇
  1988年   18篇
  1987年   17篇
  1986年   13篇
  1985年   11篇
  1983年   4篇
  1982年   4篇
  1981年   14篇
  1980年   19篇
  1979年   1篇
  1978年   3篇
  1977年   51篇
  1976年   81篇
  1975年   2篇
排序方式: 共有1641条查询结果,搜索用时 15 毫秒
961.
A Heller-Dor procedure was performed by laparotomy (group A: n = 8) or by laparoscopy (group B: n = 12) after failure of one to 17 sessions of intraluminal dilatations (n = 13) or as a primary treatment of oesophageal achalasia (n = 7). The oesophagomyotomy was extended over the thoracic oesophagus by thoracoscopy in two patients having vigorous achalasia. Injury to the oesophageal mucosa occurred in two group A patients who had previously been dilated. At follow-up (range: 1 to 113 months), 6 patients of group A (75%) and 10 of group B(83.3%) had no residual dysphagia. The four patients (group A: n = 2; group B: n = 2) who complained of heartburn prior to the operation were asymptomatic, only one group A patient developed symptoms of reflux, and oesophageal pH-monitoring was normal in the 6 group B patients investigated at follow-up. The laparoscopic approach reduces the magnitude of the operation, and the magnified overview permits precise dissection of the intraparietal adhesions which may develop after numerous sessions of dilatation.  相似文献   
962.
PURPOSE: Vascularized flaps for repeat hypospadias repair are often limited. We report our experience with the dartos flap in children undergoing secondary hypospadias and complex urethral repair. MATERIALS AND METHODS: The dartos flap is fibroadipose tissue between the scrotal skin and tunica vaginalis layers with its vascular pedicle based at the penoscrotal angle. The flap reaches the distal penile shaft without tension. Eight patients 1 to 17 years old (mean age 6) underwent urethral surgery and an interposed dartos flap procedure in 1994 to 1995. RESULTS: Of 6 patients cosmesis was excellent in 84%, erections were straight in 100%, and urinary streams were of good quality and without fistula in 100% after repeat hypospadias surgery. Following staged repair for anterior urethral valves a urethrocutaneous fistula developed in 1 patient and following urethral duplication repair results were excellent in 1. Mean followup was 1 year. CONCLUSIONS: The dartos flap is easy to mobilize and it provides excellent coverage for repeat proximal hypospadias surgery, since the dartos remains undisturbed. We endorse its use for complex urethral surgery and believe that the extra layer of closure helps to prevent urethrocutaneous fistulas.  相似文献   
963.
964.
965.
Serum cortisol response to the 1-mg overnight dexamethasone suppression test was studied in 221 depressed patients and 109 nondepressed psychiatric controls. Nonsuppression distinguished patients with primary unipolar depression (65/146) from patients with secondary unipolar depression (0/42) and nondepressed controls (0/109). Furthermore, nonsuppression distinguished the three familial subtypes of primary unipolar depressive illness: familial pure depressive disease (FPDD; 38/50 patients), sporadic depressive disease (SDD; 24/55 patients), and depression spectrum disease (3/41 patients). Moderate elevations in baseline serum cortisol levels were found in FPDD, SDD, and bipolar depression. Medication did not affect the results. The data suggest that the depressive syndrome is composed of separate illnesses, each of which has a distinctive pattern of hypothalamic-pituitary-adrenal axis activity during the depressed state as well as a specific clinical and familial psychiatric history.  相似文献   
966.
Infusions of epinephrine or levarterenol bitartrate into a rabbit nerve-muscle preparation decreased the force of the evoked twitch of anterior tibial and gastrocnemius-soleus muscles. The adverse effect of the catecholamines was not directly on skeletal muscle. The alpha-receptor blocking drug phenoxybenzamine hydrochloride prevented the adverse effect of the catecholamines if it was given prior to catecholamine infusions and unmasked a weak augmentation of twitch tension. Taken with the finding of abnormal accumulation of catecholamine in human dystrophic muscles, the production of an experimental myopathy resembling human dystrophy by the monoamine oxidase inhibitor pargyline hydrochloride, and the finding of excessive levels of catecholamines in the tissues and urine of dystrophic animals, these experiments support the hypothesis that catecholamines could play a pathogenetic role in some dystrophic diseases of muscle.  相似文献   
967.
Young adult guinea pigs were studied 6 and 9 weeks after silastic capsules containing 5 alpha-hydrotestosterone (5 alpha-DHT) and methandrostenolone (Dianabol) were implanted. DHT was more effective in causing testicular atrophy and was apparently more androgenically potent in sustaining the size of the seminal vesicles. Both steroids led to hypertrophy of the masseter muscle and increase in gastrocnemius protein concentration. Cardiac tissue was sensitive to the effects of these steroids, particularly to the larger amounts of absorbed Dianabol, in terms of increases in DNA concentration and transient loss of tissue sodium, potassium, and calcium. All alterations in muscle composition occurred in the total absence of change in tissue water. Hypernatremia and hyperkalemia was present in steroid-treated animals with significant loss of urinary potassium in DHT-treated guinea pigs. Adrenal atrophy and the lowering of circulating cortisol was further indicative of effects upon adrenocortical function and the regulation of electrolyte balance.  相似文献   
968.
An instrumented spatial linkage was used to measure the total motion in a canine shoulder as the dog was engaged in a variety of activities, including walking on a level carousel track, as well as over a hurdle, up and down a step, and up and down a ramp placed on the same track. For each activity, the motion data were analyzed, using 2 procedures. First, the linkage data and the joint contour data were combined by computer, and the motion was represented by a series of sequential computer drawings showing the scapular and humeral articular surfaces in their proper relative positions for selected increments of time during the various activities described. As an alternate but approximate method for describing the relative humeral-scapular motion, rotations about 3 mutually perpendicular axes through the average center of the shoulder joint were determined.  相似文献   
969.
Morbidity after closure of a colostomy is low if a simple antiseptic technique of intraperitoneal closure is used. In 26 patients there was no example of major wound sepsis and only 2 faecal fistulas both of which rapidly closed spontaneously. A randomized study of preoperative bowel preparation incorporating an elemental diet showed no apparent advantage for this method using our criteria for assessment.  相似文献   
970.
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