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   13691篇
  免费   934篇
  国内免费   76篇
耳鼻咽喉   157篇
儿科学   392篇
妇产科学   178篇
基础医学   1652篇
口腔科学   292篇
临床医学   1586篇
内科学   3036篇
皮肤病学   231篇
神经病学   1262篇
特种医学   812篇
外科学   2096篇
综合类   130篇
一般理论   5篇
预防医学   952篇
眼科学   341篇
药学   798篇
中国医学   15篇
肿瘤学   766篇
  2023年   88篇
  2022年   172篇
  2021年   366篇
  2020年   203篇
  2019年   323篇
  2018年   393篇
  2017年   254篇
  2016年   324篇
  2015年   401篇
  2014年   477篇
  2013年   599篇
  2012年   1001篇
  2011年   974篇
  2010年   583篇
  2009年   479篇
  2008年   864篇
  2007年   859篇
  2006年   807篇
  2005年   749篇
  2004年   595篇
  2003年   579篇
  2002年   469篇
  2001年   188篇
  2000年   163篇
  1999年   204篇
  1998年   145篇
  1997年   154篇
  1996年   104篇
  1995年   96篇
  1994年   85篇
  1993年   61篇
  1992年   100篇
  1991年   114篇
  1990年   104篇
  1989年   123篇
  1988年   115篇
  1987年   104篇
  1986年   97篇
  1985年   122篇
  1984年   96篇
  1983年   63篇
  1982年   75篇
  1981年   54篇
  1980年   75篇
  1979年   81篇
  1978年   59篇
  1977年   45篇
  1976年   54篇
  1975年   43篇
  1971年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The purpose of this study was to clarify the issue of whether DSM-III-R (American Psychological Association [APA], 1987) over-or underdiagnoses autism by comparing this diagnostic system to a well-established objective measure of diagnosis, the Childhood Autism Rating Scale (CARS). A secondary goal was to determine which of the 16 criteria are the best discriminators of autism. DSM-III-R, CARS, and clinical diagnoses of 138 consecutive admissions to a statewide program for the diagnosis and treatment of autistic and related communication-handicapped individuals (Division TEACCH in North Carolina) were compared. Results indicated a generally high degree of agreement on the diagnosis of autism using the three systems. Within this tratment-oriented program, the CARS and clinical ratings diagnosed a greater number of cases as autistic than did the DSM-III-R criteria, suggesting that DSM-III-R slightly underdiagnosed autism. The criteria that most strongly related to the diagnosis of autism regardless of the system were lack of awareness of others, abnormal social play, an impaired ability to make friends, abnormal nonverbal communication, stereotypic body movements, and restricted range of interests.  相似文献   
32.
Twenty-nine New Zealand white rabbits were allocated to undergo insertion of either polytetrafluoroethylene (PTFE) (n = 22) or microporous silicone rubber (SR) (n = 7), 3-mm diameter, 10-mm long aortic grafts. Animals with PTFE grafts received aspirin (ASA) 10 mg/kg/d and dipyridamole (DPM) 10 mg/kg/d (n = 11) or placebo (n = 11). Autologous In-111-oxine-labeled platelets were reinfused on reestablishment of blood flow through the graft. Using gamma camera images, an external graft platelet accumulation index (E-GPAI) was calculated as the In-111 activity in the graft area to the reference aorta at 24, 48, and 72 hours post implantation. Mean E-GPAI +/- SEM values for the ASA/DPM (n = 4) and control groups (n = 7) were 1.13 +/- 0.16 and 1.34 +/- 0.05 (NS) at 24 hours, 1.20 +/- 0.16 and 1.33 +/- 0.07 (NS) at 48 hours, and 1.38 +/- 0.07 and 1.35 +/- 0.10 (NS) at 72 hours, respectively. A similar internal graft platelet accumulation index (I-GPAI) was constructed based on In-111 activity in excised grafts and reference aorta measured in a scintillation counter. Mean I-GPAI +/- SEM values for the PTFE ASA/DPM (n = 9) and control groups (n = 8) at 48 hours post implantation were 43.1 +/- 2.7 and 216.8 +/- 73.9 (P = 0.05), respectively. I-GPAI values for the SR grafts were 192.5 +/- 43.1. Conclusion: The E-GPAI was not sensitive enough to demonstrate the effect of antiplatelet medication on platelet accumulation on the PTFE grafts.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
33.
34.
Human seminal plasma from normal or patients with abnormal parameters of the ejaculates contains an inhibitory material that expresses potent in vitro inhibitory activity on PHA-M-induced blast transformation and NK activity. Using the test of inhibition of NK activity, the semen samples from individuals with higher concentrations of fructose had higher inhibitory activity. The results described herein suggest that inhibitory activity for blast transformation may be present in the prostatic fluid while the NK inhibition aspects are correlated with the vesicle-marker (fructose). Inhibition of the immune responses by human seminal plasma of the effector functions indicates the interesting implication that soluble factors may indirectly protect against or promote human autoimmune infertility disease.  相似文献   
35.
BACKGROUND: Cancer pain is highly prevalent and commonly undertreated. This study was designed to determine whether dissemination of a clinical protocol for pain management would improve outcomes in community oncology practices. PATIENTS AND METHODS: A pain management protocol was developed based on accepted guidelines. After baseline assessment, oncology practices were randomly assigned to 'analgesic protocol' (AP) sites, where oncologists implemented the guidelines in a group of lung or prostate cancer patients, or to 'physician discretion' (PD) sites, where customary treatment was continued. Patients treated on protocol and a comparison group of patients with pain due to breast cancer or myeloma were monitored for change in pain using the Brief Pain Inventory, and for change in other symptoms or mood. RESULTS: The protocol terminated early because of poor accrual. We compared groups using proportions of patients who had no or mild pain at follow-up. Although measures of protocol adherence did not suggest the occurrence of major practice change, the proportion of lung or prostate cancer patients with no or mild pain increased significantly from baseline for those treated at AP sites compared with those treated at PD sites. There was no significant difference between the breast and myeloma patients treated at AP sites versus those treated at PD sites. CONCLUSION: A protocol for cancer pain management can improve pain control. Diffusion of these benefits to other patients was not confirmed. Given the small sample size, these findings require confirmation in a larger trial.  相似文献   
36.
37.
Molecular characterization of in vivo mutation at the human hypoxanthine phosphoribosyltransferase (hprt) locus has revealed a broad spectrum of mutation, both with regard to germ-line mutation in Lesch-Nyhan and gout patients, and somatic mutation in 6-thioguanine resistant T-lymphocytes from healthy individuals. The pattern of missense mutation shows a non-random distribution with a preferential location to codons for amino acids which are identical in human and the two parasites Schistosoma mansoni and Plasmodium falciparum. Although these 'evolutionary conserved' amino acids account for only 32% of the amino acids in the human hprt protein, they are involved in 76% of the missense mutations at the hprt locus in human T-lymphocytes, 67% in Lesch-Nyhan patients (with severe hprt-deficiency), but only 43% in gout patients (with partial hprt deficiency). This observation supports the notion that evolutionary conserved amino acids constitute functionally important sites in the hprt enzyme, and missense mutations affecting these amino acids will often lead to complete loss of enzyme activity. Substitutions of 'non-conserved' amino acids cause less severe hprt-deficiency (as seen in the gout patients), or may even escape clinical diagnosis. These considerations are important for the understanding of structure-activity relationships in the hprt protein, possible differences between hprt mutational spectra in germ-line and somatic cells, and the mutational spectra induced by specific exogeneous mutagens.  相似文献   
38.
39.
40.
Objective: The infant with a functional single ventricle (SV) and unobstructed pulmonary blood flow (UPBF) requires early protection of the pulmonary vascular bed to ensure suitability for a subsequent Fontan procedure. Systemic obstruction by aortic arch obstruction, subaortic stenosis, or combination of both, has been widely recognized as an important risk factor for poor outcome in children with SV–UPBF who are palliated with pulmonary artery banding (PAB). We reviewed our experience with primary PAB in the subset of patients with SV–UPBF to identify risk factors for subsequent palliative procedures and Fontan completion. Methods: Between January 1990 and May 2004, 80 patients (median age, 14 days) with functional SV and UPBF underwent PAB as their primary palliative procedure. Thirty-five neonates had concomitant aortic coarctation or interrupted aortic arch repair (44%). A Damus–Kaye–Stansel procedure was subsequently performed in 19 patients, and subaortic resection or ventricular septal defect or bulboventricular foramen enlargement was performed in five. Results: There were 4 operative deaths, and 15 late deaths. The actuarial overall survival is 84% at 1 year, 76% at 5 and 15 years. Follow-up is complete in all but six children at a mean interval of 4.9±3.7 years (range, 2 months–15 years). Thirty-seven patients (49%; 37 of 76) have undergone the hemi-Fontan procedure (with three hospital deaths) and 40 patients (53%; 40 of 76; 12 children without previous hemi-Fontan) have undergone the completion Fontan procedure without mortality or Fontan takedown. Conclusion: In infants with single ventricle physiology with or without systemic outflow obstruction and unobstructed pulmonary blood flow, a strategy of pulmonary artery banding carries acceptable operative and mid-term mortality in a high-risk group of patients. Pulmonary artery banding does not compromise performance of subsequent Damus–Kaye–Stansel procedure or completion Fontan palliation.  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