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   16589篇
  免费   999篇
  国内免费   81篇
耳鼻咽喉   132篇
儿科学   425篇
妇产科学   418篇
基础医学   2618篇
口腔科学   662篇
临床医学   1376篇
内科学   3664篇
皮肤病学   341篇
神经病学   1964篇
特种医学   457篇
外科学   1462篇
综合类   41篇
一般理论   5篇
预防医学   1012篇
眼科学   275篇
药学   1349篇
中国医学   57篇
肿瘤学   1411篇
  2024年   18篇
  2023年   171篇
  2022年   394篇
  2021年   592篇
  2020年   360篇
  2019年   477篇
  2018年   574篇
  2017年   451篇
  2016年   522篇
  2015年   649篇
  2014年   738篇
  2013年   937篇
  2012年   1469篇
  2011年   1563篇
  2010年   776篇
  2009年   741篇
  2008年   1166篇
  2007年   1087篇
  2006年   1015篇
  2005年   928篇
  2004年   832篇
  2003年   754篇
  2002年   643篇
  2001年   78篇
  2000年   59篇
  1999年   71篇
  1998年   106篇
  1997年   94篇
  1996年   60篇
  1995年   57篇
  1994年   42篇
  1993年   30篇
  1992年   19篇
  1991年   18篇
  1990年   12篇
  1989年   23篇
  1988年   15篇
  1987年   22篇
  1986年   14篇
  1985年   14篇
  1984年   11篇
  1983年   15篇
  1982年   13篇
  1981年   12篇
  1980年   5篇
  1979年   5篇
  1978年   4篇
  1975年   3篇
  1973年   6篇
  1961年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
The capability of killing various tumors or cells infected by certain viruses is a property shared by natural killer (NK) cells and by a subset of cytolytic T lymphocytes (CTLs) termed NK-CTL. Recent analysis of the molecular basis in these phenomena, however, revealed rather different molecular mechanisms. Thus, while NK cell cytotoxicity is regulated by a complex balance between activating signals (delivered by non HLA-class I-specific triggering receptors) and inhibitory signals (delivered by HLA-class I-specific receptors) the effector function of NK-CTL reflects the TCR-mediated recognition of the poorly polymorphic HLA-E.  相似文献   
993.
994.
Selective uterine artery embolization in the management of uterine myomas   总被引:8,自引:0,他引:8  
OBJECTIVE: To evaluate the effectiveness of uterine artery embolization in women with uterine myomas in terms of the clinical results for the relief of related symptoms. DESIGN: A pilot study on 26 women affected by uterine single myoma. SETTING: Tertiary level care in an university hospital. PATIENT(S): Twenty-six patients, aged 32 to 54 years, suffering of menorrhagia, pelvic pain, and abdominal mass for single myoma, intramural localization. INTERVENTION(S): Selective uterine artery embolization performed under peridural anesthesia. MAIN OUTCOME MEASURE(S): We measured the x-ray dose to which patients were exposed. Color power Doppler ultrasound examinations were performed during the follow-up evaluations at 1 to 6 months and 1 year after the procedure. RESULT(S): Uterine artery embolization was successfully performed in 100% of cases. The mean fluoroscopy time was of 20 minutes during the procedure. The mean dose of x-ray absorbed by the ovary was estimated at 18.7 cGy and the mean dose of x-ray absorbed by the skin was 126.7 cGy. A reduction of myoma volume of 55% was found at 6 months' ultrasound examination and 75% at the 1-year examination. CONCLUSION(S): Patients are well satisfied and have short recovery times with this procedure. Uterine artery embolization may be a valid alternative to traditional surgery.  相似文献   
995.
Ultrasound is the screening modality of choice for evaluation of the fetal central nervous system (CNS). However, in cases of difficult diagnosis further fetal investigation is desirable. Due to ultrafast magnetic resonance imaging (MRI) techniques artifacts from fetal motions are minimized. MRI involves no exposure to radiation and hence appears to be safe. Due to the better soft tissue contrast, additional investigation by MRI may extend the sonographic diagnosis of fetal CNS-anomalies. Ultrasound and MRI are complementary imaging methods in the evaluation of the fetal CNS. The most important indications for ultrasound are screening for CNS anomalies and serial assessment of the dynamic of the disorder. The most important indications for fetal MRI are the "second opinion" and investigation by fetal MRI instead of postpartum MRI (especially in cases of planned postpartum intervention). In this article the indications and limitations of ultrasound and magnetic resonance imaging in the evaluation of the fetal CNS are discussed.  相似文献   
996.
997.
As screening mammography has become more frequently used to screen asvmptomatic women, the diagnosis of ductal carcrinoma in situ (DCIS) has become commonplace. Its treatment remains contentious, ranging from mastectomy to local excision alone. The goal of treatment for DCIS is breast conservation, however, as many as 25% of women with this diagnosis may require mastectomy. Although no clear selection criteria have been adopted to subdivide patients into groups best treated by either mastectomy or local excision with or without radiation therapy, many patients with DCIS are candidates for local excision alone, if the biology of the disease is favorable, the size is small, and the margins are negative. Radiation therapy added to local excision decreases the likelihood of recurrence; however, if there is recurrence when first radiation is employed, the patient's only remaining choice often is mastectomy.  相似文献   
998.
BACKGROUND: Under-reporting and misclassification of maternal deaths are common, even in countries with a high quality of death statistics. The aims of this study were to determine to what extent maternal deaths are under-reported in Austria and to determine factors that might explain under-reporting. METHODS: Confidential enquiries on maternal deaths for the period 1980-98 were linked with the official mortality statistics from Statistics Austria. Maternal deaths were classified as direct and indirect obstetric deaths. RESULTS: Between 1980 and 1998 a total of 119 maternal deaths (112 direct and seven indirect obstetric deaths) were registered at Statistics Austria. Confidential inquiries into maternal deaths accumulated 191 maternal deaths (an additional 43 direct obstetric deaths and 29 indirect obstetric deaths). Total under-reporting was 38% (95% CI 31-45). Significantly more indirect obstetrical deaths were under-reported (81%; 95% CI 64-92) than direct obstetrical deaths (28%; 95% CI 21-36). CONCLUSIONS: This study demonstrates the shortcomings of official registration of maternal deaths. Thus, maternal mortality cannot be seen as a reliable basis for health policy decisions.  相似文献   
999.
BACKGROUND: The possibility that changes in activated protein C anticoagulant activity may contribute to the hemostatic changes associated with pregnancy has been previously investigated, but the results of the studies are still controversial. METHODS: Nine hundred and sixty-one healthy nonpregnant and 711 normal pregnant women who were noncarriers of factor V Leiden at different weeks' gestation were included in a cross-sectional trial. Moreover, the APC ratio was repeatedly measured in 45 women throughout pregnancy. The activated protein C ratio was tested using the modified activated partial thromboplastin time-based assay. RESULTS: A significantly lower APC ratio was observed at 20-28 and 32-38 (p = 0.0001) weeks' gestation compared with nonpregnant values. The decrease in the APC ratio throughout pregnancy showed a significant trend (p = 0.014). In none of the subjects did the APC ratio reach the cut-off values for APC resistance. CONCLUSIONS: Our data confirm a reduction in the APC ratio throughout pregnancy. In our series, an APC ratio of less than 2.0 according to the cut-off point of our laboratory).  相似文献   
1000.
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