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   29350篇
  免费   1187篇
  国内免费   65篇
耳鼻咽喉   444篇
儿科学   796篇
妇产科学   531篇
基础医学   4462篇
口腔科学   704篇
临床医学   2443篇
内科学   5720篇
皮肤病学   980篇
神经病学   2743篇
特种医学   1525篇
外国民族医学   23篇
外科学   4241篇
综合类   99篇
一般理论   9篇
预防医学   1469篇
眼科学   534篇
药学   2248篇
中国医学   61篇
肿瘤学   1570篇
  2021年   247篇
  2020年   198篇
  2019年   256篇
  2018年   432篇
  2017年   400篇
  2016年   524篇
  2015年   608篇
  2014年   604篇
  2013年   909篇
  2012年   1423篇
  2011年   1494篇
  2010年   870篇
  2009年   813篇
  2008年   1400篇
  2007年   1535篇
  2006年   1542篇
  2005年   1545篇
  2004年   1455篇
  2003年   1417篇
  2002年   1398篇
  2001年   889篇
  2000年   970篇
  1999年   828篇
  1998年   342篇
  1997年   241篇
  1996年   225篇
  1995年   164篇
  1994年   158篇
  1993年   135篇
  1992年   376篇
  1991年   412篇
  1990年   389篇
  1989年   350篇
  1988年   287篇
  1987年   300篇
  1986年   252篇
  1985年   261篇
  1984年   215篇
  1983年   142篇
  1982年   140篇
  1979年   216篇
  1978年   157篇
  1977年   139篇
  1975年   161篇
  1974年   153篇
  1973年   178篇
  1972年   160篇
  1971年   142篇
  1970年   143篇
  1967年   131篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
Hepatitis B virus (HBV) DNA is detectable in a number of liver transplant candidates who are negative for hepatitis B surface antigen (HBsAg). After liver transplantation (LT), such patients may have molecular and/or serologic evidence of HBV replication. However, clinical disease from reactivation of occult HBV infection after LT has not been described. We report a patient who underwent LT for cryptogenic cirrhosis and had to be retransplanted twice for hepatic artery thrombosis. The patient was negative for HBsAg and positive for anti-hepatitis B core (HBc) and anti-HBs before all LT procedures and developed acute hepatitis B shortly after receiving the third graft. The HBV strain isolated at that time exhibited an unusual in frame insertion of a CAG motif within the HBV polymerase (HBV(INS+)). HBV(INS+) was detected retrospectively as a minor species in pretransplantation sera and the explanted native liver by insertion-specific polymerase chain reaction. This case in an occult HBV carrier shows that clinically apparent, endogenous reinfection of the graft may occur with minor HBV variants that are not detectable in pretransplantation samples by standard diagnostic procedures. This has implications for the analysis of sources of acute hepatitis B in patients after LT and possibly for consideration of antiviral prophylaxis in anti-HBc/anti-HBs/HBV DNA-positive patients.  相似文献   
82.
In depressed patients as well as healthy controls, a positive relationship between hippocampal volume and trait anxiety has been reported. This study sought to explore the possible inter-relation between hippocampal volume and trait anxiety further. Magnetic resonance imaging at 7 T was used to measure hippocampal volumes in a rat model of extremes in trait anxiety (experiment 1) and in a Wistar population with normal anxiety-related behavior (experiment 2). In addition to anxiety-related behavior, potentially confounding factors (depression-like, exploratory, and locomotor behavior) were assessed. Experiment 1 globally supported the hypothesis of a positive relationship between hippocampus volume and trait anxiety but did not allow for ruling out possible confounds arising from cosegregation of other behavioral traits. Experiment 2 yielded strong evidence for a negative relationship which was specific for trait anxiety. Thus, the relationship between hippocampal volume and anxiety may be more complex than expected. Interestingly, anxiety-related behavior in experiment 2 had a stronger influence on hippocampal volume than depression-like behavior. In the light of hippocampal volume loss in anxiety disorder and frequent comorbidity of anxiety and depression, this finding suggests that further research into the relationship between anxiety and hippocampal volume may be critical for understanding hippocampal contributions to normal and pathological behavior.  相似文献   
83.
84.
Abstract: Preformed, xenoreactive natural antibodies (XNA) and complement (C) are involved in the initiation of vascular rejection of organs transplanted between discordant species, presumably by stimulating donor organ endothelial cells (EC). Although C is known to play a role in the activation of EC, it has not been clear whether the antibodies serve only to anchor the initial components of C, and thus permit the C cascade to proceed, or whether the antibodies themselves deliver a signal to the EC. We have tested affinity-purified human IgM containing XNA (IgM-XNA) for its ability to stimulate in vitro the up-regulation of genes in pig EC. Northern blot analysis shows that IgM, which contains XNA, stimulates mRNA accumulation for certain genes (including IL-8, PAI-1, and ECI-7, a new gene that we have found is associated with EC activation), but not others known to be up-regulated in response to TNF, IL-1 or LPS. Our results show that XNA provide a signal to EC, and thus may themselves participate in activation of EC and consequent vascular rejection.  相似文献   
85.
The aim of this study was to compare the efficacy and safety of a monomethoxypolyethylene glycol (mPEG) modified grass pollen mix allergen preparation (mPEG-gm) and a partly purified grass pollen mix allergen preparation (gm) in hyposensitization (HS), evaluating both products at two dose levels. Thirty adult patients with allergic rhinoconjunctivitis were allocated into two treatment groups based on their sensitivity to conjunctival provocation tests (CPT). Treatment was given in a double-blind manner. The starting dose was 20 BU and was approximately doubled weekly up to 20,000 BU the first year and 120,000 BU the second year. Skin testing and CPT were performed before treatment and at each dose level. All patients reached 20,000 BU the first year. Twenty-five patients continued the second year. Twenty-one of those reached 120,000 BU (9/12 on mPEG-gm and 12/13 on gm). The frequency of general side effects was reduced by about 50% with the mPEG grass mix compared with native grass mix. A significant improvement in the conjunctival sensitivity was found in both treatment groups the second year (120,000 BU) but not the first year (20,000 BU). Seventy-eight percent of the patients in the gm group and 50% in the mPEG-gm group improved by CPT (not statistically significant). The skin sensitivity was reduced after 1 year at low dose in 69% of the gm-treated patients and 33% of the mPEG treated patients. After the second year at high dose levels, the skin sensitivity decreased in all patients.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
86.
We report on the hypothalamic-pituitary-gonadal function in 2 male infants with the Smith-Lemli-Opitz (SLO or RSH) syndrome. Both infants had abnormal external genitalia. Basal and LHRH stimulated plasma gonadotropins were normal for age (1 month). Plasma testosterone, androstenedione, and dehydroepiandrosterone sulfate were normal for age and sex. Some forms of congenital adrenal hyperplasia (17,20-desmolase deficiency, 17α-hydroxylase deficiency, and 3β-hydroxysteroid dehydrogenase deficiency) were ruled out by hormonal studies. The endocrinological findings indicate a normal hypothalamic-pituitary-gonadal function and a normal adrenal steroid biosynthesis in these 2 patients. A partial androgen receptor defect causing the genital malformations seems possible in one patient. Whether 5α-reductase deficiency is the cause of the male pseudohermaphroditism in SLO syndrome remains the subject of future studies. © 1992 Wiley-Liss, Inc.  相似文献   
87.
Plasma levels of the beta-carboline, abecarnil (isopropyl 6-(benzyloxy)-4-(methoxymethyl)-9H-pyrido [3,4-b]indole-3- carboxylate, ZK112119) which is presently under development as an anxiolytic, were measured by HPLC with fluorescence detection in six healthy male volunteers given 30 micrograms/kg i.v. and 5 and 10 mg p.o. Following i.v. injection, plasma levels declined biphasically with half-lives of 6 min and 3.4 h. The total clearance was 13 ml/min/kg. After oral administration, maximum concentrations were reached after 2 h. The bioavailability was approximately 60%. The terminal half-life after p.o. administration was 7 h. No clinically relevant changes in ECG, vital signs or standard laboratory measurements occurred. Eight different adverse reactions were noted by the subjects. The most frequently reported side-effects were tiredness, dizziness, unsteady gait and lack of concentration.  相似文献   
88.
The new ordinance on X-ray irradiation, which was passed on 8 January 1987 and comes into force on 1 January 1988, is designed to keep radiation exposure during X-ray examinations to the minimum absolutely necessary. This is to be achieved not only by improving the specialist qualifications of the personnel concerned, but also by improved quality control. Substantial changes in X-ray diagnosis procedures will be introduced with the expected guidelines on implementation of the new decree.  相似文献   
89.
Activation of mature lymphocytes requires in addition to the TCR contact with the corresponding antigen the binding of the CD8 or CD4 co-receptors to MHC class I or class II proteins respectively. To investigate the contribution of the CD8-class I interaction to the elimination of autoreactive T cells during negative selection in the thymus we generated two types of transgenic mice. One set expressed a modified Kb molecule which contained a human HLA-A2 alpha 3 domain, thereby missing the binding residues for the murine CD8 molecules. The second set of mice expressed an anti-Kb specific TCR. Both lines were crossed and in the resulting double transgenic mice the development of Kb-reactive T cells was followed with an anti-clonotypic antibody. Surprisingly, efficient clonal deletion in the thymus was still observed, although the reduced CD8-class I adhesion abrogated effector functions in vivo and in vitro. These results imply that even T cells with intermediate affinity for self are negatively selected in the thymus despite the fact that they are not able to react against self antigens in the periphery. Thus a safety window is created which decreases the risk of autoaggression.  相似文献   
90.
ObjectiveTo assess the social disability of people with different psychiatric disorders.MethodsCross-site survey in five psychiatric hospitals (Dresden, Wrocław, London, Michalovce and Prague). Working-aged patients diagnosed (ICD-10) with schizophrenia and related disorders (F2), affective disorders (F3), anxiety disorders (F4), eating disorders (F5) and personality disorders (F6), were assessed at admission (n = 969) and 3 months after discharge (n = 753) using the Brief Psychiatric Rating Scale and the Groningen Social Disability Schedule. The main outcome measure was Interviewer-rated social disability.ResultsDuring acute episodes patients with personality, eating and schizophrenic disorders functioned less effectively than those with affective or anxiety disorders. After controlling for age and severity of psychopathology, there was no significant effect of the diagnosis (during remission), sex, education and history of disorder on disability. Site, employment and partnership were significant factors for the level of social disability in both measure points.ConclusionSeverity of psychopathological symptoms, not the diagnosis of a mental disorder, was the most significant factor in determining the level of social functioning, particularly during the remission period. Site, employment and partnership appeared as significant factors influencing the level of social disability.  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