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   12040篇
  免费   759篇
  国内免费   51篇
耳鼻咽喉   193篇
儿科学   195篇
妇产科学   241篇
基础医学   1824篇
口腔科学   1042篇
临床医学   974篇
内科学   2785篇
皮肤病学   268篇
神经病学   800篇
特种医学   216篇
外科学   1407篇
综合类   38篇
一般理论   6篇
预防医学   1248篇
眼科学   119篇
药学   963篇
中国医学   152篇
肿瘤学   379篇
  2023年   140篇
  2022年   259篇
  2021年   482篇
  2020年   308篇
  2019年   400篇
  2018年   500篇
  2017年   342篇
  2016年   361篇
  2015年   420篇
  2014年   533篇
  2013年   698篇
  2012年   961篇
  2011年   1150篇
  2010年   538篇
  2009年   441篇
  2008年   684篇
  2007年   717篇
  2006年   624篇
  2005年   509篇
  2004年   422篇
  2003年   359篇
  2002年   363篇
  2001年   232篇
  2000年   243篇
  1999年   184篇
  1998年   53篇
  1997年   47篇
  1996年   27篇
  1995年   31篇
  1994年   43篇
  1993年   25篇
  1992年   96篇
  1991年   56篇
  1990年   63篇
  1989年   57篇
  1988年   40篇
  1987年   34篇
  1986年   32篇
  1985年   35篇
  1984年   24篇
  1980年   17篇
  1979年   19篇
  1978年   23篇
  1976年   15篇
  1975年   18篇
  1974年   15篇
  1973年   23篇
  1971年   21篇
  1970年   19篇
  1969年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
To assess the efficacy of quinolones in the prophylaxis of infections in neutropenic patients with acute non-lymphocytic leukemia, and to evaluate the emergence of quinolone resistance in two University Hospitals in Brazil, we retrospectively compared 101 consecutive episodes of neutropenia managed with quinolone prophylaxis between 1989 and November 1993, and 26 previous episodes without prophylaxis, and reviewed the results of in vitro sensitivity of Gram-negative strains to quinolones in the same period. Prophylaxis with quinolones resulted in less episodes of bacteremias (21% vs. 69%, p=10(-7)), including Gram-negative bacteremias (6% vs. 38%, p=10(-5)), with no statistically significant difference in the death rate (18% vs. 31%, p=0.14, 95% confidence interval -6-32). The resistance of Gramnegative strains to quinolones rose from 7% to 18% between 1990 and 1993 (p=10(-5)). The resistance against ceftazidime and amikacin, the agents used in the empirical antibiotic therapy, increased in the same proportion as the quinolones. Given the limited benefit of quinolones as prophylaxis and the increasing number of quinolone-resistant Gram-negative strains observed in our hospitals, the use of quinolones as prophylaxis must be seriously questioned. A stricter control of the use of quinolones in these hospitals might decrease resistance.  相似文献   
102.
Anthropometric measures of 120 female adolescents were analyzed, 60 of them from a low socio-economic level (LSEL),and 60 from a high socio-economic level (HSEL), with 30 obese and 30 non-obese in each group, in an attempt to verify differences between the socio-economic levels in relation to the body-composition and the distribution of fat throughout the body. The weight,height, upper arm circumference and 4 skin folds (triceps, biceps,subscapular and suprailiac) were measured, and the arm muscle area, arm fat area and percentage of body fat were estimated. Those who were obese from LSEL presented an average height lower (p<0.05) than the obese from HSEL, and a greater proportion of this group presented a height deficit for their age. The arm muscle area was greater (p<0.05) in the obese from HSEL, but the percentage of body fat was similar in the two groups as well as the measures of the isolated skin folds. The increase in fat in the obese from LSEL, when compared with the non-obese, was 2.8 times greater than the muscle. In the HSEL, this increase was 1.3 times greater. It was concluded that the obese from both socio-economic levels presented different types of obesity in relation to body composition,but were similar in relation to body fat distribution.  相似文献   
103.
Data from the Hospital Information System (SIH-SUS) were linked to data from the AIDS Case Reporting System (Sinan) to assess the level of under-reporting of AIDS cases in the city of Rio de Janeiro. A high level of unreported cases(42.7%) was observed for patients treated in hospitals under Brazil's Unified Health System in the city of Rio. Bivariate analysis showed an association between reporting to the Sinan and age, principal diagnosis, and type of hospital.  相似文献   
104.
The incidence of meiotic abnormalities and their relationship with different spermatogenic parameters was assessed in 103 male patients with presumably idiopathic severe oligoasthenozoospermia (motile sperm concentration < or = 1.5 x 10(6)/ml). Meiosis on testicular biopsies was independently evaluated by two observers. Meiotic patterns included normal meiosis and two meiotic abnormalities, i.e. severe arrest and synaptic anomalies. A normal pattern was found in 64 (62.1%), severe arrest in 21 (20.4%) and synaptic anomalies in 18 (17.5%). The overall rate of meiotic abnormalities was 37.9%. Most (66.7%) meiotic abnormalities occurred in patients with a sperm concentration < or = 1 x 10(6)/ml. In this group, total meiotic abnormalities were found in 57.8% of the patients; of these, 26.7% had synaptic anomalies. When the sperm concentration was < or = 0.5 x 10(6)/ml, synaptic anomalies were detected in 40% of the patients. In patients with increased follicle stimulating hormone (FSH) concentrations, total meiotic abnormalities occurred in 54.8% (synaptic anomalies in 22.6%). There were statistically significant differences among the three meiotic patterns in relation to sperm concentration (P < 0.001) and serum FSH concentration (P < 0.05). In the multivariate analysis, sperm concentration < or = 1 x 10(6)/ml and/or FSH concentration > 10 IU/l were the only predictors of meiotic abnormalities.  相似文献   
105.
The mutation in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene has been determined in two brothers affected with Lesch-Nyhan syndrome. Female members of the family who are at risk for being heterozygous carriers of the HPRT mutation were also studied to determine whether they carry the mutation. DNA sequencing revealed that the boys' mother is heterozygous for the mutation in her somatic cells, but that three maternal aunts are not heterozygous. Such carrier information is important for the future pregnancy plans of at-risk females. The mutation, an A-->T transversion at cDNA base 590 (590A-->T), results in an amino acid change of glutamic acid to valine at codon 197, and has not been reported previously in a Lesch-Nyhan syndrome male. This mutation is designated HPRTBrasil.  相似文献   
106.
While prevalence of uterine leiomyoma is high, its presentation affecting the urinary tract is uncommon. We contribute the cases of two adult women with symptoms of nephritic colic and urinary retention. Etiology was acute obstruction of the urinary tract due to previously asymptomatic urine myomas. Management in both patients was surgery, using hysterectomy to resolve the urinary obstruction. A brief review of the literature is included.  相似文献   
107.
This paper concerns the minimum sum of absolute errors regression. It is a more robust alternative to the popular least squares regression whenever there are outliers in the values of the response variable, or the errors follow a long tailed distribution, or the loss function is proportional to the absolute errors rather than their squared values. We use data from a study of interstitial lung disease to illustrate the method, interpret the findings, and contrast with least squares regression. We point out some of the problems with the least squares analysis and show how to avoid these with the minimum sum of absolute errors analysis.  相似文献   
108.
Oral administration of an infusion of lemongrass (Cymbopogon citratus) fresh leaves to rats produced a dose-dependent analgesia for the hyperalgesia induced by subplantar injections of either carrageenin or prostaglandin E2, but did not affect that induced by dibutyryl cyclic AMP. These results indicate a peripheral site of action which was confirmed with the essential oil obtained by steam distillation of the leaves. Silica gel column fractionation of the essential oil allowed the identification of myrcene as the major analgesic component in the oil. Identification of the components was made by thin-layer chromatography and checked by mass spectrometry. The peripheral analgesic effect of myrcene was confirmed by testing a standard commercial preparation on the hyperalgesia induced by prostaglandin in the rat paw test and upon the contortions induced by intraperitoneal injections of iloprost in mice. In contrast to the central analgesic effect of morphine, myrcene did not cause tolerance on repeated injection in rats. This analgesic activity supports the use of lemongrass tea as a "sedative" in folk medicine. Terpenes such as myrcene may constitute a lead for the development of new peripheral analgesics with a profile of action different from that of the aspirin-like drugs.  相似文献   
109.
INTRODUCTION: Knowledge accumulation is overfilling the thematic content of medical graduation. Medical Schools must be alert to define a minimal content related with the most frequent disturbs. We intent to suggest topics for the minimal content, to the program of Neurology in medical graduation. METHOD: 1. To identify the places where young doctors are working outside the School Hospital (SH): we analysed the answers of the letters sent to 6415 resident - doctors (RD) in S?o Paulo's State and we made personal interview with 201 RD. 2. To verify the most frequent neuropsychiatric disturbs (ND) in the population: we made the analysis of the patient's diagnostic records in emergency room of three institutions: Municipal of Taubaté-SP, Municipal of S?o José dos Campos-SP and Faculty of Medicine of S?o Paulo Santa Casa de Misericórdia. RESULTS: 1. The RD are young and, outside the SH, they work in other emergency services. 2. The most frequent diagnosis in institutions were listed: alcoholism, cerebrovascular disease, coma, cranial trauma, dementia, dizziness, epilepsy, facial paralysis, faint, headache, hemiplegia or paraplegia, meningitis, others paralysis, periferical neuropathy and psychiatric disorders. CONCLUSIONS: Those diagnostics most frequent are relevant topics of the programmatic content to the program of Neurology in medical graduation.  相似文献   
110.
PURPOSE: To evaluate whether lower literacy is associated with poorer knowledge and more negative attitudes and beliefs toward colorectal cancer screening among veterans without recent colorectal cancer screening. PATIENTS AND METHODS: Three hundred seventy-seven male veterans, age 50 years and older, who had not undergone recent colorectal cancer screening, were surveyed about their knowledge, attitudes, and beliefs regarding colorectal cancer screening. Patients' literacy was assessed with the Rapid Estimate of Adult Literacy in Medicine, an individually administered screening test for reading. RESULTS: Thirty-six percent of the 377 men had an eighth grade literacy level or higher. Men with lower literacy were 3.5 times as likely not to have heard about colorectal cancer (8.8% v 2.5%; P =.006), 1.5 times as likely not to know about screening tests (58.4% v 40.9%; P =.0001), and were more likely to have negative attitudes about fecal occult blood testing (FOBT), but not about flexible sigmoidoscopy. Specifically, men with lower literacy skills were two times as likely to be worried that FOBT was messy (26.7% v 13.3%; P =.008), 1.5 times as likely to feel that FOBT was inconvenient (28.7% v 18%; P =.05), and four times as likely to state they would not use an FOBT kit even if their physician recommended it (17.9% v 4.0%; P =.02). CONCLUSION: Limited literacy may be an overlooked barrier in colorectal cancer screening among veterans.  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