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   291160篇
  免费   21710篇
  国内免费   6361篇
耳鼻咽喉   3534篇
儿科学   5928篇
妇产科学   4484篇
基础医学   24380篇
口腔科学   7787篇
临床医学   31136篇
内科学   32679篇
皮肤病学   2771篇
神经病学   14376篇
特种医学   8772篇
外国民族医学   15篇
外科学   26545篇
综合类   47681篇
现状与发展   15篇
一般理论   24篇
预防医学   33812篇
眼科学   2802篇
药学   27662篇
  454篇
中国医学   33387篇
肿瘤学   10987篇
  2024年   4302篇
  2023年   6312篇
  2022年   10078篇
  2021年   13481篇
  2020年   13182篇
  2019年   14186篇
  2018年   12376篇
  2017年   11045篇
  2016年   10052篇
  2015年   9537篇
  2014年   18308篇
  2013年   19139篇
  2012年   16420篇
  2011年   17560篇
  2010年   14198篇
  2009年   12399篇
  2008年   11857篇
  2007年   12075篇
  2006年   10455篇
  2005年   9095篇
  2004年   7710篇
  2003年   6912篇
  2002年   5623篇
  2001年   4926篇
  2000年   4261篇
  1999年   3558篇
  1998年   3008篇
  1997年   2939篇
  1996年   2381篇
  1995年   2344篇
  1994年   2150篇
  1993年   1757篇
  1992年   1659篇
  1991年   1494篇
  1990年   1270篇
  1989年   1211篇
  1988年   1155篇
  1987年   996篇
  1986年   928篇
  1985年   2352篇
  1984年   2522篇
  1983年   1581篇
  1982年   2128篇
  1981年   1497篇
  1980年   1295篇
  1979年   1122篇
  1978年   914篇
  1977年   712篇
  1976年   835篇
  1975年   549篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
211.
Abstract: A cell line, BAD05, derived from B lymphocytes of an adenosine deaminase (ADA; EC 3,5,4,4)-deficient patient could not proliferate in a serum-free medium containing 100 μmol/l deoxyadenosine. When BAD05 was cultured with ADA-positive fibroblasts, the proliferation of BAD05 was improved. BAD05 cell density increased when the initially mixed ratio of fibroblasts/BAD05 was 1/10 or higher, but decreased when the ratio was 1/20 or lower. Deoxyadenosine concentrations in the medium and ATP and deoxyATP (dATP) levels in the BAD05 were measured after 4 hours of coculture at initial BAD05 cell densities of 1 × 105and 1 × 106cells/ml. Deoxyadenosine concentrations in the medium decreased as the density of fibroblasts increased. The dATP level decreased as the mixed ratio rose. The ratio of fibroblasts/BAD05 rather than the cell density of fibroblasts had a larger effect on the dATP levels in BAD05. Under our experimental conditions, ADA-negative cells proliferated well when the ratio of ADA-positive cells/ADA-negative cells was over 1/10.  相似文献   
212.
The objective of this study was to evaluate clinical history and self-perception of severity as predictors of asthma severity. A short-term longitudinal study was conducted in a family practice in Melbourne, Australia, utilizing peak flow monitoring, medication diary, and self-administered asthma severity questionnaire. Seventy-two asthmatic subjects with a positive bronchodilator or exercise test, aged between 6 and 79 years, were studied. Symptom and treatment items were correlated with peak flow variability and minimal peak expiratory flow rate (PEFR). An asthma severity scale was generated using the partial credit version of Item Response Theory and the participants' severity scores were validated against lung function tests and medication usage. Quantitative modeling procedures were used to investigate the interrelationships of factors associated with peak flow variability. Severity scores demonstrated significant relationships with peak flow variability (partial r = 0.34) and treatment items. Self-perceived severity of asthma in the preceding 2 weeks showed significant association with peak flow variability (partial rho = 0.46) and minimal PEFR (rho = -0.41). The severity module of the Monash Respiratory Questionnaire is a valid and reliable instrument. The most important symptoms appear to be the frequency of use of bronchodilator and frequency of nocturnal attacks. A carefully structured clinical history in conjunction with the peak flow criteria of variability and minimal peak flow rate would be appropriate in the evaluation of asthma severity. Patients' self-perception of the severity of their asthma needs further evaluation.  相似文献   
213.
Trenkwalder P, Plaschke M, Aulehner R, Lydtin H. Felodipine or Hydrochlorothiazide/Triamterene for Treatment of' Hypertension in the Elderly: Effects on Blood Pressure, Hypertensive Heart Disease, Metabolic and Hormonal Parameters.

The aim of the study was to compare the antihypertensive efficacy of either felodipine or the diuretic combination hydrochlorothiazide/triamterene in a group (n = 65) of elderly (≥70 years) hypertensives (office blood pressure ≥ 60/95 mmHg) with special regard to ambulatory blood pressure monitoring, hypertensive heart disease and metabolic parameters. This was a randomized, double-blind study with a treatment period of 6 months. Reduction of office and 24-hr ambulatory blood pressure was comparable with both treatment regimens; after 6 months, 18 of 29 patients in the felodipine group (62%) and 20 of 27 patients in the diuretic group (74%; p = 0.4) were controlled. While episodes of ischemic type ST-segment depression were significantly reduced in the felodipine group (from 49 to 9 episodes), there was no significant change in the diuretic group (from 24 to 21 episodes). Both regimens decreased left ventricular wall thickness, but the decline in left ventricular muscle mass index was significant only for felodipine. Felodipine did not induce any change in metabolic or hormonal parameters; the diuretic combination significantly increased serum creatinine, uric acid, plasma renin activity, and plasma prorenin. Thus, the antihypertensive efficacy of felodipine and the diuretic combination was comparable in elderly hypertensives; only felodipine, however, improved parameters of hypertensive heart diesease and showed a neutral metabolic and hormonal profile.  相似文献   
214.
An experimental study was conducted in guinea pigs for the predictive assessment of the beryllium alloy hazard in occupational exposure of the skin to beryllium compounds. Guinea pigs were sensitized to beryllium sulfate according to the maximized Magnusson and Kligman test, and challenged with beryllium alloys and metallic copper, beryllium and aluminum samples. Results showed a delayed skin hypersensitivity reaction in 30 to 60% of pre-sensitized guinea pigs challenged with copper-beryllium alloys and aluminum-beryllium alloy. An inflammatory follicular reaction was induced by copper in both controls and pre-sensitized guinea pigs.  相似文献   
215.
CMSS-VEPs are presented as a sensitive, non-invasive functional investigation technique of the visual function, applicable in clinical practice. New improvements of the technique are presented. The underlying neuronal mechanisms are discussed. The clinical use is illustrated in a case of optic neuritis.  相似文献   
216.
光照疗法对新生儿红细胞谷胱甘肽还原酶活性的影响   总被引:3,自引:0,他引:3  
作者对光照疗法(光疗)前及光疗后于口服维生素B_2(43例)和不予口服维生素B_2(17例)的黄疸新生儿的红细胞谷胱甘肽还原酶(GR)的活性进行了动态观察。结果显示,接受短期光疗的黄疸新生儿其红细胞GR活性较光疗前的GR活性有显著下降,光疗后予口服维生素B_2可使下降的红细胞GR活性回升,而不予补充维生素B_2者的红细胞GR活性继续下降。光疗的时间越长,红细胞GR活性的下降越明显,补充维生素B_2使红细胞GR活性回复到正常水平所需的时间也越长。短期光疗也可引起体内维生素B_2的降解,导致红细胞GR活性的下降,为避免因红细胞GR活性下降引起的红细胞额外破坏,对接受光疗的黄疸新生儿常规补充维生素B_2的是必要的。  相似文献   
217.
Résumé  Le saccharose, administré à une concentration d’au moins 12% chez le nouveau-né à terme (24% chez le prématuré), en petite quantité (0,05 à 2 ml), dans une seringue ou mieux dans une tétine, 2 minutes avant la réalisation d’un soin douloureux avec effraction cutanée (microprélèvement, ponction veineuse), permet de réduire, plus rarement d’abolir, les comportements de détresse et/ou de douleur (pleurs et manifestations faciales). Il s’agit d’un moyen simple, non médicamenteux, et utilisable partout, qui doit pouvoir représenter une aide non négligeable chez les nouveau-nés, pour la prise en charge de la douleur provoquée par des soins modérément douloreux. Il peut être utilisé seul, mais son action limitée rend préférable de l’envisager comme technique adjuvante. Son mode d’action reste encore peu clair, ainsi que sa tolérance en cas d’administrations pluri-quotidiennes.
Summary  Sucrose of at least 12% concentration delivered to full-term infants (24% concentration for preterm infants), in a small volume of 0.05 to 2 ml, through a syringue or better through a pacifier, 2 minutes before blood sample such as heel-stick or venipuncture, can attenuate or hardly abolish stress and/ or pain (crying and facial expressions). It is a simple non pharmacological treatment, helpful in the management of pain related to moderate painful procedures. As it exerts moderate effects, it is better used as an adjuvant treatment than used alone. Mechanisms of effects are not clear yet, as well as the occurrence of adverse effects when repeated daily administrations.
  相似文献   
218.
目的 探讨普萘洛尔和低剂量兰索拉唑长期维持治疗对预防肝硬化门脉高压消化道出血的疗效。方法 1 1 9例肝硬化门脉高压患者随机分为 3组 :Ⅰ组 :给予口服普萘洛尔加上护肝治疗。Ⅱ组 :联合给予低剂量兰索拉唑和普萘洛尔。Ⅲ组 :仅给予护肝治疗。兰索拉唑维持服药 6个月 ,普萘洛尔及一般对症治疗维持 1年。观察治疗前后各组患者所伴发溃疡、门脉高压性胃病 (PHG)、急性胃黏膜病变 (AGML)情况 (发生率 ) ,各组消化道出血的复发率、门静脉直径 (PVD)、脾静脉直径 (SVD)的变化。结果 经 1年观察 ,结果显示 ,普萘洛尔组、联合治疗组、对照组出血的复发率分别为 1 5 0 %、2 2 %、48 5 % ,组Ⅰ、组Ⅱ复发率显著低于组Ⅲ ,同时 ,组Ⅰ与组Ⅱ间的差异有显著性意义。治疗可见组Ⅰ、组Ⅱ患者所伴发的溃疡、PHG、AGML明显改善 ,PVD、SVD缩小。结论 普萘洛尔组联合抑制酸维持治疗 ,可预防引起消化道出血多种病因 ,较单用普萘洛尔的疗效好  相似文献   
219.
A historical mortality study of a cohort of employees of a gold mining and refining company was carried out in Salsigne, France. A major goal of the study was to investigate the relationship between lung cancer mortality and exposure to arsenic, radon, silica, and other contaminants of the working environment. A twofold excess of lung cancer was found both among miners and smelters, mainly concentrated among workers who had experienced exposure to past levels of arsenic, radon, and silica. The consistency of the results in the mine and the refinery are suggestive of a carcinogenic risk from both soluble and insoluble arsenic, although the potential role of other factors cannot be dismissed. © 1994 Wiley-Liss, Inc.  相似文献   
220.
用蛋白胨、三油酸甘油酯、鼠肝、葡萄糖等材料模拟血清标本,通过测定该血清中蛋白、血脂、谷丙转氨酶、血糖以及部分物理参数,探讨了模拟血清从外观和实验项目上满足实验教学的可行性。结果表明,模拟血清实用、简便易得,既能解决医学生物化学实验教学标本来源困难问题,又能防止实验室污染和节省大量实验经费。  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