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   33868篇
  免费   3389篇
  国内免费   38篇
耳鼻咽喉   414篇
儿科学   1048篇
妇产科学   956篇
基础医学   4674篇
口腔科学   752篇
临床医学   3573篇
内科学   7043篇
皮肤病学   440篇
神经病学   2724篇
特种医学   1085篇
外国民族医学   9篇
外科学   4370篇
综合类   745篇
一般理论   28篇
预防医学   3919篇
眼科学   824篇
药学   2379篇
中国医学   37篇
肿瘤学   2275篇
  2021年   455篇
  2020年   253篇
  2019年   455篇
  2018年   518篇
  2017年   449篇
  2016年   421篇
  2015年   453篇
  2014年   716篇
  2013年   1105篇
  2012年   1560篇
  2011年   1617篇
  2010年   855篇
  2009年   758篇
  2008年   1422篇
  2007年   1560篇
  2006年   1511篇
  2005年   1400篇
  2004年   1277篇
  2003年   1254篇
  2002年   1271篇
  2001年   1129篇
  2000年   1177篇
  1999年   987篇
  1998年   349篇
  1997年   321篇
  1996年   348篇
  1995年   306篇
  1994年   307篇
  1993年   290篇
  1992年   916篇
  1991年   909篇
  1990年   821篇
  1989年   763篇
  1988年   673篇
  1987年   691篇
  1986年   691篇
  1985年   672篇
  1984年   548篇
  1983年   427篇
  1982年   330篇
  1981年   281篇
  1980年   253篇
  1979年   530篇
  1978年   321篇
  1977年   257篇
  1976年   277篇
  1975年   315篇
  1974年   353篇
  1973年   293篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
151.
Platelet or whole blood serotonin content did not differ significantly in patients with major depression compared to healthy controls, but within the patient group, platelet serotonin levels correlated negatively with severity of depression (r = -0.49, p = 0.007). Levels were 39% lower in patients who had made a suicide attempt compared to nonattempter patients (47.2 +/- 27.3 versus 77.6 +/- 41.7 ng/10(8) platelets, p = 0.04). Conversely, comorbid borderline personality disorder (85.3 +/- 41.5 ng/10(8) platelets) was associated with 31% greater platelet serotonin content than nonborderline patients (58.9 +/- 31.1 ng/10(8) platelets) and 27% greater than healthy controls (62.4 +/- 19.8 ng/10(8) platelets). A pronounced seasonal variation in whole blood and platelet serotonin content was found in both patients and controls, largely due to lower levels in summer. Excluding cases tested in the summer abolished the statistically significant differences in patients with and without comorbid borderline personality disorder (BPD). Nevertheless, BPD attempters had lower serotonin levels than BPD nonattempters but higher serotonin levels than non-BPD attempters. Current hostility and a life-time history of aggression were positively correlated with platelet serotonin content (r = 0.44, p = 0.04 and r = 0.41, p = 0.06). This study provides evidence for an association between lower platelet serotonin content and depression and suicidal behavior, and association of higher platelet serotonin content and comorbid borderline personality disorder and behavior traits such as aggressivity.  相似文献   
152.
153.
In a hospital setting in Sicily, we assessed a screening instrument developed for a prevalence survey of parkinsonism, peripheral neuropathies, stroke, and epilepsy. The subjects consisted of (1) hospital patients with any of the above-mentioned diseases, to investigate sensitivity; and (2) hospital visitors free of all these diseases, to investigate specificity. The standard for comparison was a clinical evaluation based on specified criteria. Trained interviewers administered the screening instrument, asking subjects to answer symptom questions and to perform simple physical tasks. For the questions and tasks together, the sensitivity estimates were 100% for parkinsonism (n = 21), 96% for peripheral neuropathies (n = 22), 96% for stroke (n = 22), and 96% for epilepsy (n = 22), while the specificity estimate was 86% (n = 21). Analogous estimates were computed for the set of questions, for the set of tasks, and for each question and task individually. Despite limitations in our approach, we concluded that the screening instrument would be adequate for its intended use.  相似文献   
154.
The purpose of this study was to determine the accuracy of FirstTemp (Intelligent Medical Systems, Carlsbad, CA) tympanic thermometer readings compared with core body temperatures obtained via pulmonary artery catheter (PAC). Five measurements were obtained on 19 cardiovascular surgery patients. Tympanic thermometer measurements tended to be higher than PAC measurements. However, most of the differences were not clinically significant. Differences found between right and left ear measurements were most likely due to poor measurement technique. When the correct technique is used, nurses can be confident that tympanic temperature readings are clinically accurate.  相似文献   
155.
Steroid receptor was assessed immunohistochemically in 158 samples of normal breast for variation through the menstrual cycle. Patterns and intensity of reaction were used in a semi-quantitative scoring system to examine the influence of cycle phase, cycle type, parity and age. The changes in oestrogen receptor for natural cycle and oral contraceptive (OC) cycles indicated down-regulation by progestins. Progesterone receptor did not vary significantly in natural cycles, but increased steadily through OC cycles. This study provides strong evidence that both oestrogen and progesterone influence breast epithelium, but dissimilarities from the endometrium are apparent. The interval since pregnancy had a significant negative effect on frequency and score of oestrogen receptor and score of progesterone receptor. Multivariate analysis established the phase of cycle and OC use as independent significant influences on oestrogen receptor. The interval since pregnancy was an independent significant factor for both oestrogen and progesterone receptor presence.  相似文献   
156.
157.
The epidemiology of myasthenia gravis in central and western Virginia.   总被引:4,自引:0,他引:4  
We conducted a study of the epidemiology of myasthenia gravis (MG) in four locations in central and western Virginia from 1970 through 1984. The population surveyed was 555,851 in 1984. A total of 73 new cases of MG occurred during the survey period, producing an overall average annual incidence rate of 9.1 per million. The point prevalence rate in 1980 was 13.4 per 100,000, and in 1984 it was 14.2. Approximately 15% of the population was black, and we found that incidence and prevalence rates for the black population were higher than the corresponding white population. When the population was subdivided into <50 and 50+ age groups, the incidence and prevalence were significantly higher in the older group. The rates we report here are higher than rates reported from any other locality. The reasons for the higher rates include optimal case identification, survey of a population with a higher incidence, and increasing aging of the population.  相似文献   
158.
159.
Guidelines recommend that patients with COPD are stratified arbitrarily by baseline severity (FEV1) to decide when to initiate combination treatment with a long-acting β2-agonist and an inhaled corticosteroid. Assessment of baseline FEV1 as a continuous variable may provide a more reliable prediction of treatment effects. Patients from a 1-year, parallel-group, randomized controlled trial comparing 50 μg salmeterol (Sal), 500 μg fluticasone propionate (FP), the combination (Sal/FP) and placebo, (bid), were categorized post hoc into FEV1 <50% and FEV1 ≥50% predicted subgroups (n=949/513 respectively). Treatment effects on clinical outcomes – lung function, exacerbations, health status, diary card symptoms, and adverse events – were investigated. Treatment responses based on a pre-specified analysis explored treatment differences by severity as a continuous variable. Lung function improved with active treatment irrespective of FEV1; Sal/FP had greatest effect. This improvement appeared additive in milder disease; synergistic in severe disease. Active therapy significantly reduced exacerbation rate in patients with FEV1 <50% predicted, not in milder disease. Health status and breathlessness improved with Sal/FP irrespective of baseline FEV1; adverse events were similar across subgroups. The spirometric response to Sal/FP varied with baseline FEV1, and clinical benefits were not restricted to patients with severe disease. These data have implications for COPD management decisions, suggesting that arbitrary stratifications of baseline severity are not necessarily indicative of treatment efficacy and that the benefits of assessing baseline severity as a continuous variable should be assessed in future trials.  相似文献   
160.
This prospective, open, randomized clinical study compared the efficacy and tolerability of norfloxacin and ciprofloxacin in adult patients with complicated urinary tract infection, defined as infection in the presence of an underlying anatomic or functional abnormality of the urinary tract. Seventy-two patients were randomized, 37 received norfloxacin (400 mg orally twice daily for 10-21 days) and 35 received ciprofloxacin (500 mg orally every 12 hours for 14-21 days). Patients were clinically assessed, and urine cultures were obtained following two to four days of therapy, and five to nine days and four to six weeks after discontinuation of therapy. Seventy-two percent of the norfloxacin group and 79 percent of the ciprofloxacin group were considered cured. This difference was not significant. One failure of norfloxacin therapy was associated with the emergence of resistant Pseudomonas aeruginosa. Following norfloxacin therapy, in 2 patients superinfections developed with resistant organisms (Staphylococcus epidermidis [1] and Pseudomonas maltophilia [1]). Twelve patients, 6 in each group, experienced adverse reactions, which were considered related to the study drug therapy in only four instances. Our results indicated comparable efficacy and tolerability of norfloxacin and ciprofloxacin in the treatment of complicated urinary tract infection in adults.  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