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   1131篇
  免费   97篇
  国内免费   6篇
耳鼻咽喉   13篇
儿科学   59篇
妇产科学   35篇
基础医学   177篇
口腔科学   18篇
临床医学   100篇
内科学   185篇
皮肤病学   11篇
神经病学   76篇
特种医学   69篇
外科学   100篇
综合类   94篇
一般理论   2篇
预防医学   109篇
眼科学   56篇
药学   47篇
中国医学   1篇
肿瘤学   82篇
  2021年   15篇
  2020年   4篇
  2019年   14篇
  2018年   23篇
  2017年   12篇
  2016年   16篇
  2015年   30篇
  2014年   49篇
  2013年   50篇
  2012年   64篇
  2011年   59篇
  2010年   39篇
  2009年   52篇
  2008年   40篇
  2007年   57篇
  2006年   62篇
  2005年   36篇
  2004年   36篇
  2003年   29篇
  2002年   22篇
  2001年   29篇
  2000年   24篇
  1999年   31篇
  1998年   45篇
  1997年   23篇
  1996年   27篇
  1995年   17篇
  1994年   31篇
  1993年   20篇
  1992年   18篇
  1991年   24篇
  1990年   15篇
  1989年   21篇
  1988年   15篇
  1987年   11篇
  1986年   21篇
  1985年   23篇
  1984年   13篇
  1983年   5篇
  1982年   4篇
  1981年   7篇
  1980年   10篇
  1979年   7篇
  1978年   13篇
  1977年   13篇
  1976年   8篇
  1975年   8篇
  1974年   4篇
  1972年   8篇
  1970年   5篇
排序方式: 共有1234条查询结果,搜索用时 15 毫秒
1.
Symptoms of tobacco withdrawal. A replication and extension   总被引:19,自引:0,他引:19  
Smokers (n = 315) who wished to quit were randomly assigned in a double-blind manner to groups using either nicotine or placebo gum. Self-reported and observed symptoms of tobacco withdrawal were collected before cessation and at follow-ups of 1 to 2 weeks, 1 month, and 6 months. Self-reported and/or observed anger, anxiety, craving, difficulty concentrating, hunger, impatience, and restlessness were the most prominent symptoms of tobacco withdrawal. These symptoms had returned to precessation levels by 1 month except increased weight, hunger, and craving continued for 6 months in many smokers. Nicotine gum decreased most symptoms, including craving and hunger but not weight. Abstinent smokers with more intense withdrawal were not more likely to relapse. Abstinent smokers who gained more weight were less likely to relapse.  相似文献   
2.
Background. Extensive questioning of patients with a wide variety of skin disorders led to the impression that nocturnal overheating was probably an important factor in the initiation and the perpetuation of many skin disorders. Methods. In order to test the hypothesis, 12 “clean-skinned” subjects (6M/6F) aged 18 to 45 years were monitored electronically every 30 seconds during an 8 hour sleep period (2300 to 0700 hours), sleeping under a standard 10 tog duvet. Results. All the subjects were too hot by 3 to 4°C. All showed changes in their EEG patterns with reduced REM sleep, increased awakenings, and all showed changes in their sleep stage patterns. In addition, they all showed evidence of increased sweating in the “heat-sink” area. Conclusions. The mechanisms where by such changes could be implicated in the precipitation and perpetuation of skin disease are discussed. “Lifestyle” modification as a very effective, noninvasive, therapeutic regime is recommended. Further research along these lines would probably be very valuable and instructive.  相似文献   
3.
4.
5.
Nicotine vs placebo gum in general medical practice   总被引:5,自引:1,他引:4  
J R Hughes  S W Gust  R M Keenan  J W Fenwick  M L Healey 《JAMA》1989,261(9):1300-1305
Three hundred fifteen smokers who attended a family practice clinic and wished to quit smoking were assigned in a random, double-blind manner to receive either nicotine (2 mg) or placebo gum. Smokers initially received brief advice from a physician and nurse, a slide presentation and written materials (29 to 35 minutes), and a single follow-up visit (12 to 20 minutes) one week after cessation. After corrections for marital status and income, 10% of those who received nicotine gum and 7% of those who received placebo gum reported continuous abstinence for 11 months and passed observer and biochemical verification (this difference was not statistically significant). We conclude that, when used in a nonselected group of smokers along with a brief intervention in a general medical practice, the pharmacologic effects of nicotine gum to increase cessation are either small or nonexistent.  相似文献   
6.
7.
The variability in plasma and urine equine procaine measurement between three independent laboratories using current methods led to the development of a sensitive, reliable, and reproducible high-performance liquid chromatographic method. Standardbred mares were administered either a penicillin G procaine preparation intramuscularly or procaine hydrochloride subcutaneously, and blood and urine were collected at defined time intervals. By HPLC the detection limits for procaine in plasma and urine were 1 and 10 ng/mL, respectively. In contrast procaine in plasma could not be detected by GC-NPD, while the urinary detection limit was 50 ng/mL. The concentration of fluoride in the collection tubes and repetitive freeze-thawing modified plasma procaine measurement. Urinary pH was a factor in estimation of urine procaine levels with greater recovery and reproducibility of results at pH 5 as compared to pH 7. This HPLC method provides a simple, sensitive, and reliable quantitation of procaine in equine plasma and urine.  相似文献   
8.
9.
Quality assurance of a helical tomotherapy machine   总被引:2,自引:0,他引:2  
Helical tomotherapy has been developed at the University of Wisconsin, and 'Hi-Art II' clinical machines are now commercially manufactured. At the core of each machine lies a ring-gantry-mounted short linear accelerator which generates x-rays that are collimated into a fan beam of intensity-modulated radiation by a binary multileaf, the modulation being variable with gantry angle. Patients are treated lying on a couch which is translated continuously through the bore of the machine as the gantry rotates. Highly conformal dose-distributions can be delivered using this technique, which is the therapy equivalent of spiral computed tomography. The approach requires synchrony of gantry rotation, couch translation, accelerator pulsing and the opening and closing of the leaves of the binary multileaf collimator used to modulate the radiation beam. In the course of clinically implementing helical tomotherapy, we have developed a quality assurance (QA) system for our machine. The system is analogous to that recommended for conventional clinical linear accelerator QA by AAPM Task Group 40 but contains some novel components, reflecting differences between the Hi-Art devices and conventional clinical accelerators. Here the design and dosimetric characteristics of Hi-Art machines are summarized and the QA system is set out along with experimental details of its implementation. Connections between this machine-based QA work, pre-treatment patient-specific delivery QA and fraction-by-fraction dose verification are discussed.  相似文献   
10.
Serologic detection of Actinobacillus pleuropneumoniae infections in swine have been problematic due to antigenic cross-reactivity of Apx toxins, lipopolysaccharide, and outer membrane proteins between A. pleuropneumoniae serotypes and other bacterial species. To maximize serologic specificity and sensitivity, we developed an assay that uses highly purified A. pleuropneumoniae capsular polysaccharide (CP) conjugated to biotin, which is then bound to streptavidin-coated enzyme-linked immunosorbent assay (CP-BS-ELISA) plates. This assay was used to test a panel of 240 serum samples from pigs prior to challenge, after challenge with bacterial species other than A. pleuropneumoniae, or after challenge with A. pleuropneumoniae serotype 1, 5, or 7. Overall assay results for the individual sera tested were reproducible on the same day and on separate days. The sensitivity of the assay was 100% by ELISAs with biotin-CPs of serotypes 1 and 7 and 87.5% by ELISAs with biotin-CP of serotype 5. Specificity was 100% by ELISAs with biotin-CPs of serotypes 1 and 5 and 94.5% by ELISAs with biotin-CP of serotype 7. The biotin-CPs of at least three A. pleuropneumoniae serotypes could be combined for use in a screening assay to detect antibodies to CPs from strains of different serotypes. In conclusion, the CP-BS-ELISA proved to be a serotype-specific and species-specific assay with high sensitivity for the identification of pigs exposed to A. pleuropneumoniae.  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