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   426764篇
  免费   29214篇
  国内免费   9288篇
耳鼻咽喉   6862篇
儿科学   10370篇
妇产科学   7990篇
基础医学   29494篇
口腔科学   10932篇
临床医学   44362篇
内科学   49868篇
皮肤病学   5281篇
神经病学   21768篇
特种医学   9075篇
外国民族医学   51篇
外科学   61771篇
综合类   64391篇
现状与发展   19篇
一般理论   31篇
预防医学   37674篇
眼科学   9735篇
药学   33906篇
  557篇
中国医学   42254篇
肿瘤学   18875篇
  2024年   4316篇
  2023年   7861篇
  2022年   13178篇
  2021年   17706篇
  2020年   17007篇
  2019年   21829篇
  2018年   19236篇
  2017年   16005篇
  2016年   13562篇
  2015年   12741篇
  2014年   26536篇
  2013年   27086篇
  2012年   23325篇
  2011年   25087篇
  2010年   20143篇
  2009年   18199篇
  2008年   17653篇
  2007年   18022篇
  2006年   15746篇
  2005年   13740篇
  2004年   11275篇
  2003年   9851篇
  2002年   7720篇
  2001年   7023篇
  2000年   5848篇
  1999年   5063篇
  1998年   4175篇
  1997年   3981篇
  1996年   3348篇
  1995年   3156篇
  1994年   3013篇
  1993年   2391篇
  1992年   2362篇
  1991年   2041篇
  1990年   1747篇
  1989年   1571篇
  1988年   1484篇
  1987年   1303篇
  1985年   3947篇
  1984年   4943篇
  1983年   3437篇
  1982年   3899篇
  1981年   3634篇
  1980年   3228篇
  1979年   2946篇
  1978年   2561篇
  1977年   1936篇
  1976年   2169篇
  1975年   1650篇
  1974年   1434篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
RELATIONSHIP BETWEEN CORNEAL DELLEN AND TEARFILM BREAKUP TIME   总被引:1,自引:0,他引:1  
The BUT of 51 strabismus patients were measured before and after operation. The average pre-op BUT was 28.75 seconds(10.96"-91.80"). The post-op BUT in all operated eyes were reduced significantly, no matter what procedures had been performed and whether dellen appeared or not(P<0.01). The BUT in the group complicated dellen reduced from 23.22"(pre-op) to 8.61"(post-op). The incidence of dellen was 22.54% in this study. The incidence of dellen after rectus resection procedure(47.75%) was much higher than that after rectus recession(5.13%)(P<0.01). This study showed that dellen was closelyre related to the BUT and occurred more often in the eyes on which resection procedure was performed. It is considered that excessive lacrimation and elevation of the bulbar conjunctiva near the limbus may disturb the stability of the precornea tearfilm and cause the tearfilm break up earlier. Local corneal dehydration and dellen formation may be caused by reduced BUT. The incidence of dellen after operation may be higher if the cornea was carefully observed.  相似文献   
992.
A series of cures for ophthalmological diseases practised by saints are described, particularly the Saints Cosmas and Damian and the Saints Cyrus and John, the famous Anargyroi. In the xenones of the Byzantine churches and in the hospitals connected to these, therapeutic regimes, cures and surgical interventions took place at night during incubation, following the example of the ancient Asclepieia. This conclusion stands in spite of the fact that the authors describing the lives of the saints were often clergy who frequently cloak the true therapeutical cures by presenting them in a supernatural manner in order to stress the divine intervention of the saints. From the operations mentioned, it is clear that cataract surgery was among the operations most frequently practised.  相似文献   
993.
Summary In recent years models for the internal (intra-islet) regulation of hormone secretion have been proposed to explain how different islet cells might regulate each other by means of their respective secretory peptides. Models that emphasize the importance of a directed intra-islet blood flow and sequence of perfusion of islet cells rely on a certain type of islet microanatomy and vascular supply. The experimental studies underlying these models have partly been performed in dogs. To extend the incomplete morphological knowledge of the canine endocrine pancreas both canine islets of Langerhans and extrainsular cells have been analysed in immunostained serial semithin (0.5 m) sections. In addition to their occurrence within islets of Langerhans, all endocrine cell types are also found at extrainsular sites (about 9% of all endocrine cells) where they are distributed in different quantities among the epithelial lining of exocrine acini or excretory ducts and the connective tissue. There are continuous transitions from single extrainsular cells to small mono-and polycellular cell groups to islets. In a comprehensive analysis of whole islets, including computer-assisted three-dimensional reconstructions, the size, shape and vascularization of the islets as well as their cellular composition and the microtopology of islet cells have been studied. We have found marked intra-and inter-islet heterogeneities of the parameters investigated that are not compatible with concepts of a uniform and directed vascular perfusion of the various islet cell populations. Instead, their paracrine regulation may occur primarily via hormonal secretion into the intercellular spaces or vascular hormonal delivery to adjacent cells.  相似文献   
994.
The emergence of surgery during the Renaissance marked the birth of surgery as a discipline based on clinical observation and improvement of technical skill. Some of the most experienced surgeons dealing with pediatric problems were Paré, Phaer, Würtz and, especially, Hildanus, who described more than 150 cases in children. Some minor malformations were curable, and some major anomalies were described for the first time. Renaissance surgeons had no explanations for the etiology of diseases and malformations. In many instances, the imaginatio was considered to be responsible.  相似文献   
995.
The objective of the present study was to assess the relationship between the amount of lactate accumulated during complete ischaemia and the ensuing changes in extra- and intracellular pH (pHe and pHi, respectively). The preischaemic plasma glucose concentration of anaesthetized rats was varied by administration of glucose or insulin, pHe was determined in neocortex with ion-sensitive microelectrodes, and tissue lactate and CO2 contents were measured, tissue CO2 tension being known from separate experiments. The experiments were carried out in both normocapnic [arterial CO2 tension (PaCO2) approximately 40 mm Hg] and hypercapnic (PaCO2 approximately 80 mm Hg) animals. Irrespective of the preischaemic CO2 tension, DeltapHe was linearly related to tissue lactate content. Depending on the preischaemic glucose concentration, DeltapHe varied from <0.4 to >1.4 units. The results thus fail to confirm previous results that the changes in pHe describe two plateau functions (DeltapHe approximately 0.5 and 1.1, respectively), with a transition zone at tissue lactate contents of 17 - 20 mmol kg-1. Changes in pHi given in this study are based on the assumption of a uniform intracellular space. The pHi changed from a normal value of approximately 7.0 to 6.5, 6.1 and 5.8 at tissue lactate contents of 10, 20 and 30 mmol kg-1. The intrinsic (non-bicarbonate) buffer capacity, derived from these figures, was 23 mmol kg-1 pH-1. Some differences in pH and in HCO3- concentration between extra- and intracellular fluids persisted in the ischaemic tissue. These differences were probably caused by a persisting membrane potential in the ischaemic cells.  相似文献   
996.
Nineteen aneurysmal bone cysts and five angiomas of bone were treated by selective arterial embolization. The median follow-up was 22 months. In 17 patients healing occurred with complete relief of symptoms; in 11 of these almost complete ossification of the lesion resulted. In the remaining cases, little or no ossification was apparent but ossification may take 1 year or more to occur. No recurrence was observed in any of these cases. Recurrence occurred only in two cases. In one, growth of the recurrence stopped after a second embolization, and the X-rays showed no change. Selective arterial embolization represents a treatment of choice in aneurysmal bone cyst and angioma of bone especially of the spine, sacrum, or pelvis. In these sites embolization replaces surgery which might be hazardous due to intraoperative bleeding.Supported in part with Rizzoli Research Funds  相似文献   
997.
Summary In idiopathic recurrent calcium urolithiasis (RCU) in men (n=37) the metabolic effects of oral tripotassium citrate (PC) were investigated in a longitudinal field study. The patients were either normo- (n=22) or hypocitraturic (n=15). Laboratory examinations were performed before, and after 3, 6, and more than 12 months of medication. Acceptance of PC was poor, mainly because of the salty taste of the tablet preparation chosen, and a number of participants dropped out of the study. In the remaining participants, compliance was acceptable when evaluated on the basis of urinary potassium and undesired side effects did not occur. In the short term (up to 3 months), PC evoked compensated metabolic alkalosis (pH and citrate in urine increased; blood gases remained normal), a drop in urinary calcium, together with increasing oxaluria, hydroxyapatite supersaturation, and calcium phosphate crystalluria. In the long term (>12 months) PC urinary pH and citrate dissociated, in that pH returned to pretreatment baseline values, whereas citrate stayed at high levels. In normocitraturics but not in hypocitraturics, urinary urea and sodium in creased with PC. Hypocitraturics appeared to be less sensitive to the effects of PC, as reflected by the relatively small rise in urinary pH and citrate, and they maintained higher mean levels of indicators of bone metabolism (osteocalcin, alkaline phosphatase, hydroxyproline) despite continuous administration of PC. It was concluded that although the PC tablet preparation was effective it may not be an ideal anti-stone drug treatment in the long term and that, especially in hypocitraturiecs, the intrinsic metabolic defect of RCU may not be sufficiently well controlled.  相似文献   
998.
To perform a breast reduction under local anesthesia we need a large amount of anesthetic with lasting effects. For this I use a solution of 25 cc of lidocaine, 25 cc of bupivacaine, and 1 cc of epinephrine in 350 cc of saline solution. The bupivacaine allows a 4–6-hour operation. Once the breast is infiltrated, a great amount of anesthetic is lost in the incision, in the dissection, and in the resected tissue. Thus, a low dose remains subcutaneously to be metabolized by the liver. The serum lidocaine levels are low during these operations, as demonstrated by fluorescence polarization immunoassay. Under analgesic sedation the submammary sulcus and the retroglandular space are infiltrated, blocking the perforants of the intercostal nerves, under the areola, beneath the skin where the incision is made and where the aerola is placed. This procedure has been applied to many techniques of breast reduction by modifying the infiltration under the incision lines. For hypertrophy up to 1000 g, 200–300 cc of anesthetic solution is used for both breasts at one stage, while for gigantomastia, about 400 cc of anesthetic is used, infiltrating and reducing one after the other. As the blood loss is minimal and the recovery very fast, with an appropriate adhesive bandage and a soutien, the patient could be discharged in the afternoon. Our experience includes 94 reduction mastoplasties with local anesthesia, and also 74 other mastoplasties with equally good results. There were no patient complaints and, in general, they felt very comfortable, awakening without pain or side effects.  相似文献   
999.
1000.
A recent review of the results of gastroplasties done at the University of Alberta Hospital showed that there was a high incidence of late weight loss failure. Therefore a new operation, gastroplasty/distal gastric bypass, has been performed on 263 patients. This operation results in a profound (mean greatest percentage excess weight loss of 87% at approximately 2 years) and lasting weight loss (mean final percentage excess weight loss of 78%) at 4 years, range 2-7.5 years post-operatively. Only 0.9% of patients failed to maintain at least a 40% excess weight loss. The operation achieves its effect through a moderate restriction that permits patients to eat normal table food from the time of discharge and with a mild malabsorption that is not ordinarily associated with diarrhea or notable deficiencies. Certain patients required debanding of the stoma and others developed staple-line eventration. Neither of these events after long-term follow-up resulted in weight loss failure nor in other serious side-effects. It is concluded that moderate failure of the gastroplasty stoma and staple line does not necessarily result in weight loss failure, because the malabsorptive portion of the operation remains intact. Low hemoglobin occurred in 16% of cases and deficiency of serum iron in 34%; a much smaller number of patients had chronic or intermittent deficiencies of these entities. Correction was easily achieved with oral replacement. Deficiencies in albumin, calcium, phosphorus and folate were rarely seen and minimal elevation of serum AST values occurred in just over 1% of patients. Chronic deficiencies or elevations were not seen in these patients. Stomal ulcer occurred in 6% of patients and bleeding associated with stomal ulcer in 1%. Half the patients with ulcer were managed with H2 blockers, the other half with vagotomy. Both forms of treatment when individualized effectively prevent re-ulceration.  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