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   1319篇
  免费   102篇
  国内免费   16篇
耳鼻咽喉   16篇
儿科学   51篇
妇产科学   16篇
基础医学   195篇
口腔科学   35篇
临床医学   102篇
内科学   298篇
皮肤病学   38篇
神经病学   60篇
特种医学   119篇
外科学   155篇
综合类   113篇
预防医学   125篇
眼科学   10篇
药学   58篇
中国医学   3篇
肿瘤学   43篇
  2023年   6篇
  2022年   15篇
  2021年   36篇
  2020年   10篇
  2019年   33篇
  2018年   30篇
  2017年   24篇
  2016年   24篇
  2015年   32篇
  2014年   45篇
  2013年   43篇
  2012年   61篇
  2011年   57篇
  2010年   52篇
  2009年   52篇
  2008年   73篇
  2007年   57篇
  2006年   51篇
  2005年   51篇
  2004年   48篇
  2003年   28篇
  2002年   32篇
  2001年   33篇
  2000年   35篇
  1999年   37篇
  1998年   58篇
  1997年   48篇
  1996年   38篇
  1995年   23篇
  1994年   30篇
  1993年   27篇
  1992年   25篇
  1991年   14篇
  1990年   19篇
  1989年   16篇
  1988年   19篇
  1987年   29篇
  1986年   18篇
  1985年   16篇
  1984年   6篇
  1983年   10篇
  1982年   17篇
  1981年   6篇
  1980年   5篇
  1978年   10篇
  1977年   4篇
  1976年   9篇
  1975年   6篇
  1974年   3篇
  1970年   3篇
排序方式: 共有1437条查询结果,搜索用时 31 毫秒
91.
92.
Breast milk samples from three groups of Brazilian women were evaluated: G1, mothers delivering term babies of low birth weight (n=16); G2, mothers delivering preterm babies of appropriate birth weight (n = 20); G3, mothers delivering term babies of appropriate birth weight ( n = 30). Milk samples were obtained at 48 h and on the 7th, 15th, 30th and 60th days after delivery and they were analyzed for lysozyme and total IgA levels and for the presence of specific antibodies against Poliovirus types I, II, III, Rotavirus, Herpes simplex virus, Varicella zoster and Cytomegalovirus. The groups were not statistically different in relation to mother's age, parity, type of delivery or socio-economic levels. IgA levels were higher in both low-birth-weight groups (G1 & G2) compared to the control group (G3) throughout the study period. Lysozyme levels decreased up to the 15th day, increasing thereafter up to the 60th day in all groups. Specific antibodies were detected throughout the study period, with no differences among groups. We conclude that breast milk composition of mothers delivering low-birth-weight babies (G1 & G2) was similar despite the different gestational ages.  相似文献   
93.
The incidence of transient hypogammaglobulinaemia of infancy (THI) detected in a major paediatric centre over a 10 year period was examined. A total of 2468 subjects less than 2 years of age had an IgG measurement taken between July 1979 and March 1990. Subjects with known immunodeficiencies were excluded. Fifteen patients were classified as having THI with an initial IgG level less than the fifth centile followed by a second measurement within the normal range. A further 24 patients were identified as having possible THI with a single low IgG concentration. There were 60,174 live births each year in Victoria in the years 1979-88. This gives an incidence of proved THI of 23 per 10(6) births, and including proved and probable THI an incidence of 61 per 10(6) live births. Of those patients with proved THI 12/15 had symptoms of either atopic disease or food allergy/intolerance and three had gastrointestinal symptoms without any evidence of atopic disease. At presentation 12/15 (80%) were IgA deficient and 9/15 had IgM concentrations less than the 20th centile for age. It is suggested that in view of the preponderance of atopic and food intolerant patients that subclinical protein loss from the bowel due to allergic inflammation may be a contributing factor to the development of THI in some patients.  相似文献   
94.
95.
In this paper we report the occurrence of changes in the migration of certain isoenzymes of a cloned strain (MAV-CINVESTAV) ofEntamoeba histolytica. This strain was isolated from an asymptomatic carrier and showed an initial nonpathogenic zymodeme I. The transfer of polyxenic trophozoites from Robinson's medium (7% serum) to Jones' medium (30% serum) provoked changes in isoenzyme expression, resulting in the conversion of zymodeme I to a zymodeme that was similar to the XVII zymodeme except for two slow-running bands and a single fast-running band that were detected for hexokinase (HK). This XVII-like zymodeme reverted to zymodeme I when trophozoites were cultured under monoxenic conditions in TY1-S-33 medium (10% serum). When we cultured cloned strain MAV-CINVESTAV under axenic conditions in TY1-S-33 medium, trophozoites expressed a pathogenic zymodeme with two fast-running HK bands and a betaphosphoglucomutase band. In addition, phagocytosis and the ability of the trophozoites to destroy cell-culture monolayers were expressed only in trophozoites cultured under axenic conditions. The axenization procedure required the presence of liveFusobacterium symbiosum and is also described herein.Abbreviations HK hexokinase - ME l-malate: NADP+ oxidoreductase - GPI glucose phosphate isomerase - PGM phosphoglucomutase - P pathogenic - NP nonpathogenic - px polyxenic - mx monoxenic - ax axenic  相似文献   
96.
Michael  AS; Mafee  MF; Valvassori  GE; Tan  WS 《Radiology》1985,154(2):413-419
A retrospective review of the dynamic CT studies performed in our institution on head and neck lesions, excluding the brain, was carried out. Five basic types of density vs. time curves were obtained. Dynamic CT scanning is valuable in the differential diagnosis, management, and followup of such cases; its usefulness as an imaging modality in diagnosis and followup of hemangiomas is stressed.  相似文献   
97.
BACKGROUND: Ischemic mitral regurgitation has been associated with diminished survival compared with nonischemic mitral regurgitation. Conversion from mitral valve replacement to valve repair has improved prognosis, but it is unclear whether ischemic mitral regurgitation remains an independent predictor of outcome after mitral valve repair. METHODS: Five hundred thirty-five patients undergoing mitral valve repair (primarily rigid ring annuloplasty) with or without coronary bypass from 1993 through 2002 were reviewed retrospectively (ischemic mitral regurgitation, n = 141; nonischemic mitral regurgitation, n = 394). A Cox proportional hazards model evaluated survival as a function of 9 simultaneous covariates: ischemic versus nonischemic mitral regurgitation, age, sex, number of medical comorbidities, ejection fraction, New York Heart Association class, coronary disease, reoperation, and year of operation. RESULTS: According to univariable analysis, patients with ischemic mitral regurgitation had greater age, higher comorbidity, lower ejection fraction, higher New York Heart Association, and higher reoperation rate (all P < .001) compared with those having nonischemic mitral regurgitation. Univariable 30-day mortality was as follows: 4.3% for patients with ischemic mitral regurgitation versus 1.3% for patients with nonischemic mitral regurgitation (P = .01). Unadjusted 5-year mortality was as follows: 44% +/- 5% for patients with ischemic mitral regurgitation versus 16% +/- 3% for patients with nonischemic mitral regurgitation (P < .001). In the multivariable model, however, only the number of preoperative comorbidities and advanced age were independent predictors of survival (P < .0001), whereas ischemic mitral regurgitation, sex, ejection fraction, New York Heart Association class, coronary disease, reoperation, and year of operation did not achieve significance (all P > .19). After being adjusted for differences in all preoperative risk factors, survival was not statistically different between ischemic mitral regurgitation and nonischemic mitral regurgitation (P = .33). CONCLUSIONS: With routine application of rigid ring annuloplasty, long-term patient survival is more influenced by baseline patient characteristics and comorbidity than by ischemic cause of mitral regurgitation per se. Future risk assessment and decision making should be based on patient condition and should not be biased by ischemic cause of mitral regurgitation.  相似文献   
98.
99.
Concern exists about the risk of nephrotoxicity using tenofovir (TDF) in HIV-infected patients. We performed a retrospective case-control study including 122 consecutive TDF-naive patients who started treatment with TDF-containing regimens and 194 patients receiving antiretroviral therapy with other antiretroviral drugs. During a 12-month observation period 5 (4.1%) patients in the TDF group versus 1 (0.5%) in the control group developed grade 1 or higher serum creatinine elevations (p = 0.018). Only 2 (1.6%) patients discontinued TDF treatment as a result of serum creatinine level elevations. In 4 of the 5 patients developing creatinine elevations TDF was combined with lopinavir-ritonavir. The use of TDF in clinical practice during a 12-month period is associated with low risk of mild renal failure. Further studies to assess long-term renal safety of this drug are needed.  相似文献   
100.
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