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   3870篇
  免费   222篇
  国内免费   30篇
耳鼻咽喉   77篇
儿科学   89篇
妇产科学   66篇
基础医学   390篇
口腔科学   152篇
临床医学   394篇
内科学   803篇
皮肤病学   45篇
神经病学   230篇
特种医学   204篇
外科学   632篇
综合类   112篇
一般理论   1篇
预防医学   238篇
眼科学   128篇
药学   384篇
中国医学   42篇
肿瘤学   135篇
  2023年   67篇
  2022年   142篇
  2021年   203篇
  2020年   139篇
  2019年   153篇
  2018年   200篇
  2017年   123篇
  2016年   126篇
  2015年   114篇
  2014年   156篇
  2013年   214篇
  2012年   312篇
  2011年   312篇
  2010年   156篇
  2009年   118篇
  2008年   222篇
  2007年   217篇
  2006年   186篇
  2005年   132篇
  2004年   135篇
  2003年   125篇
  2002年   101篇
  2001年   52篇
  2000年   42篇
  1999年   44篇
  1998年   26篇
  1997年   18篇
  1996年   13篇
  1995年   21篇
  1994年   12篇
  1993年   13篇
  1992年   25篇
  1991年   17篇
  1990年   19篇
  1989年   24篇
  1988年   23篇
  1987年   27篇
  1986年   14篇
  1985年   9篇
  1984年   8篇
  1983年   8篇
  1982年   7篇
  1981年   4篇
  1980年   7篇
  1979年   7篇
  1976年   6篇
  1974年   5篇
  1972年   2篇
  1969年   3篇
  1968年   3篇
排序方式: 共有4122条查询结果,搜索用时 15 毫秒
21.
BACKGROUND AND OBJECTIVES: Internal carotid artery dissection has been extensively studied and well-described. Although there has been a recent increase in the number of reported cases of vertebral artery (VA) dissection, the clinical variety of presentation and the early warning symptoms have not been well-described before. Our objectives in this study include: (1) To determine the early symptoms and warning signs which may help the clinician in the early identification and treatment of patients with VA dissection. (2) To explore the variety of clinical presentation of VA dissection and its relation to prognosis. DESIGN AND SETTING: Retrospective analysis of hospital records in a tertiary academic centre for the period 1989-1999. RESULTS: Twenty-six patients were identified (13 men and 13 women). The mean age was 48. Possible precipitating factors were identified in 14 patients (53%). Sporting activity and chiropractic manipulations were the most common (15% and 11% respectively). Headache and/or neck pain was the prominent feature in 88% of patients and was a warning sign in 53%, preceding onset of stroke by up to 14 days. The most common clinical features included vertigo (57%), unilateral facial paresthesia (46%), cerebellar signs (33%), lateral medullary signs (26%) and visual field defects (15%). Bilateral VA dissection presented in six patients (24%). The most common region of dissection was the C1-C2 level (16 arteries, 51%). Intracranial VA dissection was found in eight arteries (25%). The majority of patients (83%) had favorable outcome. Poor prognosis was associated with (1) bilateral dissection; (2) intracranial VA dissection accompanied by subarachnoid hemorrhage. Only two patients reported stroke recurrence. CONCLUSIONS: Our findings show that VA dissection affects mainly middle age persons and involves both sexes equally. Headache and/or neck pain followed by vertigo or unilateral facial paresthesia is an important warning sign that may precede onset of stroke by several days. Although the majority of patients will have excellent prognosis, this was less likely in patients presenting with subarachnoid hemorrhage or bilateral VA dissection. Recurrence rate was low.  相似文献   
22.
Objectives: To objectively evaluate the clinical and functional outcomes of cochlear implantation in an elderly population. Design: Retrospective comparative study. Setting: Neurotology unit at Manchester Royal Infirmary, a supraregional tertiary referral centre in collaboration with Adult Cochlear Implant Programme at The University of Manchester. Participants: All cochlear implant procedures (38) undertaken on post‐lingually deafened elderly patients (age range at the time of implantation 65–80 years, n = 34) in the period from 1989 to 2002. Main outcome measures: Medical and surgical outcomes. Audiological performance outcomes for isolated words, words in sentences in quiet and noise. Functional outcome measures used are self‐reported measures of the social, psychological and emotional aspects of quality of life, and the differences between expectations for functional outcomes and the realization of functional outcomes. They included expectation profiles, Glasgow Benefit inventory (GBI) and Glasgow Health Status Inventory Questionnaire (GHSI). Results: There was statistically significant improvement post‐implantation of both open and closed set test scores (P < 0.01). Eighty‐two percentage of patients were completely satisfied with their cochlear implants. Patients judged that implantation restored half the loss of quality of life that they had experienced as a result of severe‐profound deafness with a highly significant (P < 0.001) improvement in overall quality of life after implantation. The commonest post‐operative observation was transient mild pyrexia. Conclusions: The age of a cochlear implant candidate should not be a factor in the candidacy decision‐making process. The quality of life of our elderly recipients was significantly improved after cochlear implant.  相似文献   
23.
Background: Although native faith healers are found in all parts of Pakistan, where they practice in harmony with the cultural value system, their practice is poorly understood. This study investigated the prevalence, classification and treatment of mental disorders among attenders at faith healers. Method: The work of faith healers with 139 attenders was observed and recorded. The mental status of attenders was assessed using a two-stage design: screening using the General Health Questionnaire followed by diagnostic interview using the Psychiatric Assessment Schedule. Results: The classification used by faith healers is based on the mystic cause of disorders: saya (27%), jinn possession (16%) or churail (14%). Sixty-one percent of attenders were given a research diagnosis of mental disorder: major depressive episode (24%), generalized anxiety disorder (15%) or epilepsy (9%). There was little agreement between the faith healers' classification and DSM-IIIR diagnosis. Faith healers use powerful techniques of suggestion and cultural psychotherapeutic procedures. Conclusions: Faith healers are a major source of care for people with mental health problems in Pakistan, particularly for women and those with little education. Further research should assess methods of collaboration that will permit people with mental health problems to access effective and culturally appropriate treatment. Accepted: 9 June 2000  相似文献   
24.
We describe splenic infarction (SI), an infrequent condition, in an 82‐year‐old COVID‐19 patient with chronic atrial fibrillation (AF). COVID‐19 may cause thrombosis, and AF is a predisposing factor for splenic infarction. Suspicion of SI may be warranted in COVID‐19 patients with abdominal pain, especially if a predisposing factor exists.  相似文献   
25.
Coumarin and benzothiazole scaffolds can be found in a number of natural or synthetic antioxidants. In an effort to develop a novel radical scavenger and potential antioxidant, a series of coumarin derivatives containing 2‐methylbenzothiazoline motif and related compounds was synthesized and evaluated for their DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) and ABTS?+ (2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals scavenging activities. Among them, 7‐hydroxy‐3‐(2‐methyl‐2,3‐dihydrobenzo[d]thiazol‐2‐yl)‐2H‐chromen‐2‐one ( 3e ) has shown a significant free radical scavenging activity. From the structure–activity point of view, it was found that phenolic coumarin ring and benzothiazoline moiety in target compounds may contribute to the scavenging activity against free radicals.  相似文献   
26.
27.
People of Asir region of Saudi Arabia chew Caralluma sinaica (CS) to lower glucose level. To establish its utility in diabetes mellitus we have under taken this study. The effect of CS on streptozotocin (STZ)-induced diabetic model as well as effect on oral glucose tolerance test were studied. The extract was shown to have positive test for possessing following chemical constituents like phenolic alkaloids, glycosides, flavonoids, coumarins, steroids and tannins. Administration of CS in different doses (50, 100, 150 and 200mg/kg, p.o.) to normal animals caused significant (P<0.01) decrease in glucose level. Prior administration of either CS (100mg/kg, p.o.) or glibenclamide (GB) (5mg/kg, p.o.) blocked the rise of glucose caused by the streptozotocin. Antidiabetic activity of CS was compared with clinically available drug GB. Administration of CS (100mg/kg, p.o.) to diabetic rabbits for 30 days has been shown to decrease plasma glucose level to almost normal level (P<0.001). Liver and kidney weight expressed as percentage of body weight significantly (P<0.05; P<0.01) increased in diabetic rabbits versus normal control (CNT). CS significantly (P<0.05) reversed the increasing weight of liver caused by STZ but not GB. STZ induced lowering of glycogen content of liver and muscle was reversed by both CS and GB. STZ induced a significant (P<0.001) increase in renal glycogen content this was almost normalized by CS (P<0.001) whereas GB significantly decreased (P<0.002) glycogen content. In oral glucose tolerance test administration of glucose increased plasma glucose level significantly in the diabetic control over the 2-h period. Compared to diabetic control plasma glucose levels in rabbits given CS or GB were significantly lower at all the time points that blood was sampled after oral glucose load. Comparing with the GB treatment blood glucose lowering effect was more pronounced for diabetic rabbits given CS. All these effects could explain the basis for use of this plant extract to manage diabetes mellitus.  相似文献   
28.
29.
Although numerous health care interventions have been implemented in Pakistan, the high maternal and neonatal mortality rates still remain a challenge. Developed countries have reduced maternal and neonatal mortality rates by improving the skill and knowledge levels of nurse-midwives. This paper reviews maternal and neonatal health issues, challenges in current midwifery education, and the role of government and international agencies in Pakistan. The exact maternal and neonatal mortality rates in Pakistan are unknown; a census has not occurred since 1998, and data provided in more recent studies were presented in summary format. A number of factors that contribute to the high mortality rate could easily be controlled by using competent nurse-midwives throughout all levels of the Pakistani health care system. A reduction in the maternal mortality rate is likely to occur if the Pakistan government and international agencies work together to implement specific recommendations in maternal and neonatal health. These recommendations include: 1) holding an invitational conference; 2) strengthening the existing midwifery and Lady Health Visitor curricula; 3) pilot testing an expanded midwifery program; and 4) advocating for and obtaining political commitments and resources for midwifery education.  相似文献   
30.
Platelet-rich fibrin (PRF) as a rich source of effective growth factors has been used as a scaffold in tissue regeneration. It is known that PRF exhibits rapid degradability against enzymes, which should be decreased using crosslinking agents to reduce the release rate of growth factors and increase the effectiveness of tissue regeneration. In this study, a carbodiimide crosslinker with different concentrations (0.01%, 0.05%, 1%, and 2%) was used to modify and improve the properties of PRF gel. The crosslinked gels were evaluated with analyses such as SEM, swelling, degradability, mechanical strength, release test, cytotoxicity, and cell adhesion. The results showed that with increasing crosslinker concentration, the morphology of the fiber structure changes drastically, the swelling rate decreases from 300% (control) to 160% for the crosslinked gel, the degradation time for the control sample increases from 8 days to more than two weeks for the crosslinked gel, and the Young''s modulus increases from 0.15 MPa (control) to 0.61 MPa for the crosslinked samples. Growth factors also showed lower release with increasing crosslinking ratio. Cytotoxicity assays demonstrated that by increasing the crosslinker concentration to 1% w/v, no cytotoxicity was observed. Cellular studies with DAPI staining showed that the cells penetrated well into the gels and were well distributed, especially in gels with lower crosslinker concentrations. In addition, the modified PRF gel can be used as a scaffold for tissue regeneration.

1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride (EDC) as a crosslinker can improve the physical and mechanical properties of PRF gel by forming covalent bonds.  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