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   95295篇
  免费   7459篇
  国内免费   145篇
耳鼻咽喉   910篇
儿科学   3169篇
妇产科学   2822篇
基础医学   11826篇
口腔科学   1628篇
临床医学   13972篇
内科学   17594篇
皮肤病学   1432篇
神经病学   9359篇
特种医学   2815篇
外国民族医学   37篇
外科学   10615篇
综合类   1359篇
一般理论   113篇
预防医学   11327篇
眼科学   1708篇
药学   5879篇
  3篇
中国医学   141篇
肿瘤学   6190篇
  2022年   649篇
  2021年   1543篇
  2020年   959篇
  2019年   1605篇
  2018年   1843篇
  2017年   1372篇
  2016年   1502篇
  2015年   1665篇
  2014年   2271篇
  2013年   3743篇
  2012年   5303篇
  2011年   5646篇
  2010年   3065篇
  2009年   2818篇
  2008年   5012篇
  2007年   5673篇
  2006年   5429篇
  2005年   5206篇
  2004年   5070篇
  2003年   4787篇
  2002年   4648篇
  2001年   1901篇
  2000年   1817篇
  1999年   1753篇
  1998年   1158篇
  1997年   1002篇
  1996年   911篇
  1995年   810篇
  1994年   759篇
  1993年   701篇
  1992年   1407篇
  1991年   1389篇
  1990年   1309篇
  1989年   1257篇
  1988年   1077篇
  1987年   1212篇
  1986年   1106篇
  1985年   1139篇
  1984年   966篇
  1983年   827篇
  1982年   656篇
  1981年   608篇
  1980年   560篇
  1979年   830篇
  1978年   634篇
  1977年   575篇
  1976年   566篇
  1975年   487篇
  1974年   600篇
  1973年   541篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Fetal scalp blood sampling (FSBS), in conjunction with fetal heart rate monitoring, is a method of fetal surveillance that may avoid cesarean delivery of the healthy fetus or indicate the need for immediate delivery of a compromised fetus. Some researchers have recently begun to question the efficacy of FSBS. In this article, three nurse-midwives discuss FSBS as a tool in assessing fetal well-being during labor and consider whether FSBS is a nurse-midwifery procedure.  相似文献   
12.
Changes on serial assessments of brain MRI lesion load are used for monitoring therapeutic efficacy in patients with multiple sclerosis (MS). We assessed the accuracy and reliability of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences for measurement of lesion volume using a semiautomated contour technique. Cranial CSE and FSE examinations of 18 patients with secondary progressive MS were studied. The mean lesion load was slightly higher with the CSE sequence (p = 0.002). Intraobserver variability was significantly higher for FSE than for CSE, according to both the coefficient of variation between two measurements (mean 2.48 % and 1.35 % respectively, p < 0.05) and back-transformed 95 % limits of agreement (1.005–1.060 for FSE; 0.988–1.019 for CSE). Although FSE sequences are quicker and the total lesion volume measurements are similar to those obtained with CSE, the poorer reproducibility raises doubts about the use of FSE to replace CSE in clinical trials. Received: 26 March 1996 Accepted: 4 April 1996  相似文献   
13.
Effects of hypothermia on testicular ischemia   总被引:14,自引:0,他引:14  
The ischemic effects of prolonged testicular torsion have been well documented; however, prevention or arrest of the damaging effects of prolonged ischemia has been incompletely studied. Two groups of Sprague-Dawley rats were subjected to varying lengths of bilateral testicular ischemia. Group I underwent normothermic ischemia for two, four, and six hours. Likewise, Group II underwent similar time periods of ischemia, however, after thirty minutes of normothermic ischemia the scrotum of each animal was placed into an ice bath maintained at 4C. Two weeks postoperatively, bilateral orchiectomy was performed. Histology of the testes of the two groups was compared. Neither group revealed significant destruction of the germinal epithelium after two hours of ischemia. Group I revealed only 25% preservation of the germinal epithelium at four hours and only 8% preservation at six hours of ischemia. In contrast, Group II which received ice showed 90% preservation of germinal epithelium at four hours and 85% preservation at six hours of ischemia. We conclude that external ice application significantly preserves seminiferous tubules at four and six hours of ischemic injury in the rat testicle.  相似文献   
14.
BACKGROUND: The aim was to determine the influence of the socioeconomic status of the family and the hygienic practices in the home on the prevalence of head lice infestation in children. METHODS: The study was carried out by analyzing the answers to a standardized epidemiological questionnaire given to parents of school children aged 4-17 in Bet Shemesh, a medium-sized urban town 25 km from Jerusalem. RESULTS: Of 3,000 questionnaires distributed, 958 (31.9%) were completed and returned. The majority of the children (72.4%) had been previously infested with lice. Half of them had other family members, mainly brothers and sisters, who had been infested in the past with lice. In 97.5% of the families the mother was responsible for examining the children for lice, and for carrying out treatment when infestation was present. An association was found between presence of lice infestation and mother's education, age of child, and frequency of shampooing, combing, and examination for lice. There was no association between infestation rates and mother's country of origin, crowding in the home, and the sharing of combs, brushes, hats, scarves, towels, and clothes. CONCLUSIONS: There is evidence that the incidence of lice infestation depends on the hygienic practices in the home rather than on the socioeconomic status of the family or sharing of personal articles among family members.  相似文献   
15.
16.
OBJECTIVE AND DESIGN: Bacterial products as well as the host airway inflammatory responses contribute to the pathogenesis of Pseudomonas infections. We sought to determine if Pseudomonas elastase (PE) induces mitogen-activated protein (MAP) kinase activity in association with interleukin-8 (IL-8) production by alveolar epithelial cells. METHODS: We utilized Western blot analysis to detect phosphorylation of signaling intermediates and ELISA was used to measure IL-8 production. RESULTS: We found that PE induces phosphorylation of the extracellular signal-regulated (ERK1/2) proteins of the MAPK pathway in A549 epithelial cells. Similar results were obtained using primary cultures of rabbit alveolar type II epithelial cells. PE also enhanced IL-8 production, which was abolished in the presence of the ERK activation inhibitor U0126. CONCLUSIONS: We conclude that PE activates the ERK1/2 arm of the MAPK pathway and that activation of this pathway results in enhanced IL-8 production. The results demonstrate that PE may augment pulmonary inflammation via cellular signaling that regulates expression of IL-8.  相似文献   
17.
Infection is a common and serious complication of severe head injury. Immunocompetence in 25 severely head injured patients was investigated by measuring: (1) delayed-type hypersensitivity (DTH) skin test responses to common antigens; (2) phytohaemagglutinin (PHA) stimulated peripheral blood lymphocyte (PBL): blastogenesis, phenotype expression, and lymphokine production; (3) lymphokine-activated killer (LAK) cytotoxicity, antibody dependent cellular cytotoxicity (ADCC) and natural killer (NK) cytotoxicity; and (4) immunoglobulin and complement levels. The incidence of anergy to DTH skin testing was 100%. There was a decrease in PHA stimulated: PBL blastogenesis (p = 0.002), T-cell expression (p = 0.018), helper T-cell expression (p less than 0.001), interleukin-2 receptor expression (p less than 0.001), interleukin-2 production (p = 0.035) and gamma-interferon production (p less than 0.001). LAK cytotoxicity was depressed following incubation with IL-2 (p less than 0.001). There was no significant decrease in immunoglobulin levels and all acute phase reactants tested increased. The results of this study indicate that the cellular arm of immune response, including lymphocyte activation and cytokine production, is suppressed following severe head injury. The lack of enhancement in LAK cytotoxicity following incubation of PBLs with interleukin-2 suggests that factors other than decreased interleukin-2 production, such as the inherent lymphocyte dysfunction, other soluble mediators or suppressor cells, may be responsible for the reduction in cellular immunity observed following severe head injury.  相似文献   
18.
A retrospective analysis of the results of 27,801 cervical smears from one year in a community laboratory was undertaken. This represented 23,820 individual patients. Abnormalities were seen in 9.3% of patients. Three point seven percent of patients had benign abnormalities, 5.5% had cervical intraepithelial neoplasia and 0.1% had major abnormalities. The incidence of cervical epithelial abnormality was highest in the 15-34 age group but major abnormalities were seen most often in the 55+ age group. Human papillomavirus was more commonly seen in the youngest age group. The presence of inflammation was reported in 65% of the smears. Thirty percent of smears had no endocervical cells and 0.6% were grossly inadequate. Fifteen percent of patients had repeat smears and 3% of total smears were judged unnecessary. Forty two point six percent of patients less than 55 years of age in the laboratory population base had a smear but only 7.9% of those over 55.  相似文献   
19.
Nursing diagnosis as a critical component of the nursing process provides a common taxonomy to describe problems that nurses can treat and is a convenient, logical way to reference nursing standards. Theory is translated into practice with the use of population-specific prototype care guides and a written orders system. Nurses in leadership are responsible for providing the necessary resources to promote professional growth and facilitate desired change. Recommendations to assist with the implementation of nursing diagnosis are identified in Table 1. The system is dependent on staff nurses' professional commitment to learning and willingness to actively participate in change. Involvement of staff nurses continues to be a critical factor in the improvement of nursing practice.  相似文献   
20.
Previous studies have shown that stimulation of adrenergic receptors in the brain increases the expression of the immediate early gene (IEG), c-fos, in vivo (Mol. Brain Res., 6(1989) 39-45). The present study was undertaken to determine whether this also holds for other IEGs which have been shown to be activated in brain cell culture by adrenergic agonists. Both yohimbine injection and stressful stimulation, two treatments causing brain norepinephrine (NE) release, were found to cause a parallel, transient activation of at least 5 IEGs (c-fos, nur77, tis-7, zif-268 and tis-21) in the rat cortex. Genes that are not immediate early (beta-actin, NGF and HSP70) were found not to be affected in the interval used (6 h). The responses were mediated predominantly by beta-adrenoceptors with some contribution from alpha 1 receptors. The parallel activation of multiple genes by noradrenergic receptors may enable the coding of different biochemical responses to the activation of different receptors.  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