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   21249篇
  免费   2078篇
  国内免费   300篇
耳鼻咽喉   89篇
儿科学   1136篇
妇产科学   426篇
基础医学   2015篇
口腔科学   166篇
临床医学   1627篇
内科学   2552篇
皮肤病学   256篇
神经病学   1051篇
特种医学   2089篇
外国民族医学   9篇
外科学   1551篇
综合类   2027篇
现状与发展   2篇
一般理论   1篇
预防医学   3309篇
眼科学   68篇
药学   2788篇
  20篇
中国医学   484篇
肿瘤学   1961篇
  2024年   31篇
  2023年   374篇
  2022年   729篇
  2021年   934篇
  2020年   940篇
  2019年   896篇
  2018年   956篇
  2017年   819篇
  2016年   797篇
  2015年   731篇
  2014年   1599篇
  2013年   1688篇
  2012年   1205篇
  2011年   1415篇
  2010年   1106篇
  2009年   1102篇
  2008年   1063篇
  2007年   992篇
  2006年   770篇
  2005年   653篇
  2004年   550篇
  2003年   445篇
  2002年   389篇
  2001年   337篇
  2000年   305篇
  1999年   243篇
  1998年   203篇
  1997年   183篇
  1996年   157篇
  1995年   143篇
  1994年   149篇
  1993年   141篇
  1992年   111篇
  1991年   118篇
  1990年   97篇
  1989年   99篇
  1988年   85篇
  1987年   92篇
  1986年   75篇
  1985年   137篇
  1984年   109篇
  1983年   72篇
  1982年   80篇
  1981年   78篇
  1980年   86篇
  1979年   77篇
  1978年   53篇
  1977年   39篇
  1976年   40篇
  1973年   31篇
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
51.
The application of spin-echo magnetic resonance imaging sequences on non-invasive temperature imaging for temperature mapping of human limbs is investigated. In an in vitro expriment performed on a meat sample, the equilibrium magnetisation P and the spin-lattice relaxation time T1 are calculated from the values for the repetition time TR and the signal intensities obtained by a spin-echo sequence at different tissue temperatures tures as measured by a fibre-optic probe. T1 is linearly correlated to the tissue temperature, and P is linearly correlated to the reciprocal value of the absolute temperature. Both effects, taken together, lead to a non-linear dependency of the signal intensity on temperature. Therefore a TR leading to maximum temperature dependency of the signal intensity is calculated and used in the futher experiments. In the in vivo experiments, the lower legs of two volunteers are cooled from outside. Images are acquired with a spin-echo sequence (1.5T, TR=1200 ms, TE=10 ms). A rise in signal intensity in the muscle with falling skin temperature is observed, particularly in more peripheral muscle layers. This study shows that spin-echo sequences can be used to monitor temperature changes and temperature differences in living muscle tissue.  相似文献   
52.
We report an unusual case of anaphylaxis and hepatitic dysfunction in a child with the administration of the twenty-third course of high-dose methotrexate. The latter had been used as an adjuvant to prevent pulmonary metastases and the prior 22 courses had been well tolerated. An attempt to reinstate methotrexate after the twenty-third course was again followed by a similar reaction. © 1995 Wiley-Liss, Inc.  相似文献   
53.
A series of experiments evaluated the determinants of preference for mixtures of ethanol plus sucrose relative to sucrose in rats. One dipper served 10% ethanol mixed with 10% sucrose, and the second dipper served 10% sucrose. Lever presses operated each dipper according to a variable-interval 5-s schedule. In three experiments the subjects were given pre-session meals of sucrose (2.5–20 ml) or sucrose (20 ml) plus chow (5 or 10 g). Pre-session meals decreased responding maintained by sucrose but not responding maintained by ethanol mixture. In two experiments body weight was varied from 85% to 125% of the initial free-feeding values. Increases in body weight, like pre-session meals, decreased responding reinforced by sucrose, but typically did not decrease responding reinforced by ethanol mixture. Throughout most of the study, ethanol consumption remained at about 1.25 ml per half hour session (3–4 g/kg per 30 min). For example, pre-session access to ethanol mixture decreased within-session ethanol consumption, but total consumption, counting both sources, remained about 1.25 ml/session. The within-session patterns of responding also differed. Responding reinforced by ethanol mix decreased as a function of ethanol consumption, whereas responding reinforced by sucrose was relatively constant throughout the session. The simplest explanation of the results is that ethanol's pharmacological consequences regulated preference.  相似文献   
54.
作者以体模实验为基础。测定了不同管电压拍摄胸片时的病人剂量,考察了提高管电压对胶片影像质量的影响,结果表明,使用高电压拍摄胸片比使用低电压有利于降低病人剂量,在增加影像信息量,提高肋骨阴影区和纵膈区灶检出率方面更有较大优越性,此外,使用高电压技术不家利于延长X射线管的使用寿命。  相似文献   
55.
生精丸治疗男性不育60例临床研究   总被引:1,自引:0,他引:1  
目的观察生精丸对男性不育的治疗作用.方法选择120例男性不育患者,随机分为治疗组和对照组.每组60例,分别给予生精丸和五子衍宗丸治疗.治疗前后以WLJY-9000伟力彩色精子质检系统进行精液参数分析,并检测血液睾酮(T)水平,同时观察病人服用生精丸期间有无明显不良反应.结果治疗组精子密度、活率、活力以及运动参数和睾酮水平等指标均明显高于对照组(P<0.05),痊愈率、显效率及总有效率亦高于对照组(P<0.05),且服药期间无明显的不良反应.结论生精丸有从整体上纠正精液异常的功效,能使病人精子数量、质量、睾酮水平得到提高.  相似文献   
56.
In 7 patients (5 girls, 2 boys) with the EMG or Wiedemann-Beckwith syndrome, statural growth, bone age (BA), weight and pubertal development were studied longitudinally. Height was above the 90th percentile (%) for chronological age (CA) after age 2 years, reaching an average of 2.5 SD above the mean at or after puberty. Adult or attained height also exceeded significantly (P<0.015) parental (genetic) target height by 13.2 cm on the average. In one girl, adult height prognosis (190 cm) could be reduced to an adult height of 183 cm by high-dose estrogen treatment. In most children, growth velocity remained above the 90th % up to 4–6 years of age and normalized thereafter. In all patients studied, bone age was markedly advanced and particularly so during the first 4 years after birth. Weight was above the 90th–97th % during infancy and early childhood and remained there, appropriate or slightly subnormal for height, until adulthood, except for 3 girls who reached and maintained the 50th % during or after puberty. Spontaneous pubertal development occurred within normal limits for CA and around the 50th % for BA. Except for the marked bone age acceleration, the reason for the increased statural growth and adult height in patients with the EMG syndrome is still unknown.  相似文献   
57.
目的:探讨儿童在X线体检中减少照射剂量的方法。方法:应用东芝500mA遥控X线机、FJ-427型热释光剂量仪等设备,对100名3~5岁儿童体检时,随机分成两个对照组、每组50名,分别接受胸透或平片检查,对检查测得数据均进行统计学处理。结果:胸透时胸部接受的照射剂量是平片的22倍多,其它部位接受的X线散射剂量平均值之比亦在20~30倍之间。结论:在儿童X线体检中应采用常规胸片替代胸透,可以有效地降低其辐射危害。  相似文献   
58.
不同营养支持方式对肠外瘘患者人体组成改善作用之比较   总被引:1,自引:1,他引:0  
目的观察不同营养支持方式对肠外瘘患者人体组成的改善作用。方法30例肠外瘘患者分成两组各15例,分别给予全肠外营养支持(TPN)或全肠内营养支持(TEN),观察10d前后患者人体组成及血清胰岛素样生长因子-1(IGF-1)的变化。结果10d后所有患者的体重指数(BMI)与体细胞群(BCM)显著改善,而TEN组患者10d前后BCM增加幅度更明显,分别为(27.5±0.8)kg和(29.0±0.6)kg,Day10与Day0相比,P<0.01。两组患者总体水(TBW)与细胞内水(ICW)均增加,尤其ICW,Day10与Day0相比,TEN组P<0.01;TPN组P<0.05。血清IGF-1在两组患者治疗后均有显著上升,TEN组增加幅度更明显,Day0为(175.0±32.9)ng/ml,Day10为(255.5±34.1)ng/ml,与Day0比较,P<0.01;与TPN组比较,P<0.05。IGF-1的变化与BCM的改善显著正相关(r2=0.16,P<0.05)。结论营养支持治疗能显著改善肠外瘘患者的体细胞群,纠正细胞内、外水的异常分布,而EN作用更明显。  相似文献   
59.
60.
Physical inactivity, excess adiposity and premature mortality   总被引:5,自引:0,他引:5  
The purpose of this report is to review the evidence that physical inactivity and excess adiposity are related to an increased risk of all‐cause mortality, and to better identify the independent contributions of each to all‐cause mortality rates. A variance‐based method of meta‐analysis was used to summarize the relationships from available studies. The summary relative risk of all‐cause mortality for physical activity from the 55 analyses (31 studies) that included an index of adiposity as a covariate was 0.80 [95% confidence interval (CI) 0.78–0.82], whereas it was 0.82 [95% CI 0.80–0.84] for the 44 analyses (26 studies) that did not include an index of adiposity. Thus, physically active individuals have a lower risk of mortality by comparison to physically inactive peers, independent of level of adiposity. The summary relative risk of all‐cause mortality for an elevated body mass index (BMI) from the 25 analyses (13 studies) that included physical activity as a covariate was 1.23 [95% CI 1.18–1.29], and it was 1.24 [95% CI 1.21–1.28] for the 81 analyses (36 studies) that did not include physical activity as a covariate. Studies that used a measure of adiposity other than the BMI show similar relationships with mortality, and stratified analyses indicate that both physical inactivity and adiposity are important determinants of mortality risk.  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