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   3152967篇
  免费   234052篇
  国内免费   4416篇
耳鼻咽喉   43542篇
儿科学   103004篇
妇产科学   85927篇
基础医学   464998篇
口腔科学   88497篇
临床医学   289771篇
内科学   607235篇
皮肤病学   69377篇
神经病学   251066篇
特种医学   117746篇
外国民族医学   726篇
外科学   465601篇
综合类   66405篇
现状与发展   14篇
一般理论   1292篇
预防医学   254185篇
眼科学   73861篇
药学   234120篇
  16篇
中国医学   5813篇
肿瘤学   168239篇
  2019年   25498篇
  2018年   34827篇
  2017年   26237篇
  2016年   29262篇
  2015年   33317篇
  2014年   46928篇
  2013年   71156篇
  2012年   97357篇
  2011年   103818篇
  2010年   61424篇
  2009年   58244篇
  2008年   97815篇
  2007年   104285篇
  2006年   104807篇
  2005年   101983篇
  2004年   97713篇
  2003年   94066篇
  2002年   91301篇
  2001年   139606篇
  2000年   142976篇
  1999年   120729篇
  1998年   35406篇
  1997年   31329篇
  1996年   31747篇
  1995年   30049篇
  1994年   27891篇
  1993年   26066篇
  1992年   94825篇
  1991年   92767篇
  1990年   90376篇
  1989年   87450篇
  1988年   80603篇
  1987年   79051篇
  1986年   74629篇
  1985年   71439篇
  1984年   53644篇
  1983年   46211篇
  1982年   27671篇
  1979年   50268篇
  1978年   36205篇
  1977年   30167篇
  1976年   28668篇
  1975年   30931篇
  1974年   37274篇
  1973年   35829篇
  1972年   33792篇
  1971年   31844篇
  1970年   29707篇
  1969年   28285篇
  1968年   26130篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
981.
982.
OBJECTIVE: To evaluate the reproducibility of sonographic measurement of the lower uterine segment in pregnant women at term. METHODS: Two independent observers performed transabdominal sonography on 129 women between 36 and 38 weeks of gestation who had had a previous Cesarean section. Sonography was performed when the patients had a full and a half-full bladder; in 100 patients, the measurements were also performed transvaginally, with the patients having an empty bladder. Agreement was quantified by the intraclass correlation coefficient and, using a cut-off of 3.5 mm, by the kappa coefficient. RESULTS: The intraobserver agreement was generally high (intraclass correlation coefficient > 0.90). The interobserver agreement was higher on transvaginal (intraclass correlation coefficient, 0.94) compared with transabdominal (0.70 and 0.84, with full and half-full bladder, respectively) ultrasound. The kappa coefficient was 0.75 transvaginally, compared with 0.34 and 0.54 using the transabdominal approach, with full and half-full bladder, respectively. CONCLUSION: The agreement between two observers for sonographic transvaginal measurement of the lower uterine segment can be considered good, compared with poor to moderate agreement using the transabdominal approach.  相似文献   
983.
Mucosal trypsin, a protease-activated receptor (PAR) stimulant, may have an endogenous bronchoprotective role on airway smooth muscle. To test this possibility the effects of lumenal trypsin on airway tone in segments of pig bronchus were tested. Bronchial segments from pigs were mounted in an organ chamber containing Kreb's solution. Contractions were assessed from isovolumetric lumen pressure induced by acetylcholine (ACh) or carbachol added to the adventitia. Trypsin, added to the airway lumen (300 microg x mL(-1)), had no immediate effect on smooth muscle tone but suppressed ACh-induced contractions after 60 min, for at least 3 h. Synthetic activating peptides (AP) for PAR1, PAR2 or PAR3 were without effect, but PAR4 AP caused rapid, weak suppression of contractions. Lumenal thrombin was without effect and did not prevent the effects of trypsin. Effects of trypsin were reduced by N(omega)-nitro-L-arginine methyl ester but not indomethacin. Trypsin, thrombin and PAR4 AP released prostaglandin E2. Adventitially, trypsin, thrombin and PAR4 AP (but not PAR2 AP) relaxed carbachol-toned airways after <3 min. The findings of this study show that trypsin causes delayed and persistent bronchoprotection by interacting with airway cells accessible from the lumen. The signalling mechanism may involve nitric oxide synthase but not prostanoids or protease-activated receptors.  相似文献   
984.
Mycophenolate mofetil (MMF) used in a triple-drug regimen has been shown to decrease acute rejection rates, compared to a double-drug regimen. The impact of MMF on late acute rejection (LAR) episodes has not been well described. To investigate the risk of LAR (rejection > or = 6 months post-transplantation) data from the Scientific Registry of Transplant Recipients (SRTR) were used. We studied adult primary liver transplant recipients transplanted between June 1, 1995, and April 30, 2004, with hepatitis C virus (HCV) (n = 3356), hepatitis B virus (HBV) (n = 550) or a nonviral (n = 5740) primary cause of liver disease who were recorded as receiving continuous 3-(MMF + Tacro + steroids) versus 2-drug (Tacro + steroids) therapy for at least 6 months immediately post transplantation. Kaplan-Meier analysis showed significantly lower LAR rates 4 years post-transplant in 3- versus 2-drug HCV, HBV and nonviral disease patients. Multivariate regression confirmed 3- versus 2-drug therapy to be associated with a decreased risk of LAR. Late graft survival was significantly lower at 4 years post-transplant for patients with LAR 6-12 months post-transplantation versus patients with early rejection (78.0% vs. 87.0%, p < 0.001) and no rejection (88.1%, p < 0.001). Three-drug versus 2-drug therapy for a minimum of 6 months may offer a better treatment strategy to avoid the consequences and expense of LAR episodes.  相似文献   
985.
背景与研究目的:静脉曲张破裂出血是肝硬化的一个主要并发症,与6周内20%的死亡率有关。目前国际指南推荐肝硬化患应常规行上消化道内镜检查(食管胃十二指肠内镜检查,EGD)来筛查是否有食管静脉曲张。新近出现的食管胶囊内镜在对胃食管反流和Barrett食管的研究中已经显示出准确的诊断效应。该研究比较胶囊内镜和EGD对肝硬化患食管胃底静脉曲张和门脉高压性胃病的检出率。患与方法:在3个中心进行了先导试验。有进行EGD临床指征的肝硬化患,在EGD检查后48h内用胶囊内镜来筛查或监视食管静脉曲张。研究采用盲法,即由1名事先不知道患病史和EGD检查结果的研究评估胶囊视频成像。结果:在32例纳入的患中,EGD和胶囊内镜检查发现有食管静脉曲张23例患。有1例患经胶囊内镜发现有轻度静脉曲张,但EGD未检出。胶囊内镜和EGD诊断食管静脉曲张和门脉高压性胃病的总体一致性分别为96.9%和90.6%。没有与胶囊内镜相关的不良事件。  相似文献   
986.
987.
Subjective (non-recordable) tinnitus is the conscious perception of a phantom sound, and a very frequent, sometimes disabling, condition. Even if subjective tinnitus is often related to peripheral hearing loss, neurophysiological and functional imaging studies provide increasing evidence for an involvement both auditory and non-auditory central nervous pathways in the generation of tinnitus and related distress. Repetitive transcranial magnetic stimulation (rTMS) has been proposed to relieve tinnitus by reducing auditory cortex hyperexcitability associated with this condition. This paper will review the first clinical results reported in auditory cortex rTMS studies, with special reference to the pathophysiology of tinnitus processing and the mechanisms of action of rTMS. Although rTMS appears to be a very promising tool for the diagnosis and the treatment of tinnitus patients, available knowledge is still very limited at the moment. Further basic research and clinical studies are needed in order to optimize the parameters of stimulation (stimulus frequency, cortical target definition) and to validate the application of this technique in the management of patients with disabling tinnitus.  相似文献   
988.
989.
OBJECTIVES: This study investigates posttraumatic stress disorder (PTSD) and its associated risk factors in a random, national, Canadian sample of United Nations peacekeeping veterans with service-related disabilities. METHODS: Participants included 1016 male veterans (age < 65 years) who served in the Canadian Forces from 1990 to 1999 and were selected from a larger random sample of 1968 veterans who voluntarily and anonymously completed a general health survey conducted by Veterans Affairs Canada in 1999. Survey instruments included the PTSD Checklist-Military Version (PCL-M), Center for Epidemiological Studies-Depression Scale (CES-D), and questionnaires regarding life events during the past year, current stressors, sociodemographic characteristics, and military history. RESULTS: We found that rates of probable PTSD (PCL-M score > 50) among veterans were 10.92% for veterans deployed once and 14.84% for those deployed more than once. The rates of probable clinical depression (CES-D score > 16) were 30.35% for veterans deployed once and 32.62% for those deployed more than once. We found that, in multivariate analyses, probable PTSD rates and PTSD severity were associated with younger age, single marital status, and deployment frequency. CONCLUSIONS: PTSD is an important health concern in the veteran population. Understanding such risk factors as younger age and unmarried status can help predict morbidity among trauma-exposed veterans.  相似文献   
990.
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