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   887篇
  免费   55篇
  国内免费   4篇
耳鼻咽喉   6篇
儿科学   21篇
妇产科学   34篇
基础医学   68篇
口腔科学   22篇
临床医学   111篇
内科学   197篇
皮肤病学   25篇
神经病学   11篇
特种医学   94篇
外科学   65篇
综合类   81篇
预防医学   75篇
眼科学   30篇
药学   59篇
  1篇
中国医学   19篇
肿瘤学   27篇
  2022年   14篇
  2021年   18篇
  2020年   19篇
  2019年   22篇
  2018年   28篇
  2017年   17篇
  2016年   15篇
  2015年   37篇
  2014年   32篇
  2013年   47篇
  2012年   42篇
  2011年   47篇
  2010年   47篇
  2009年   41篇
  2008年   42篇
  2007年   37篇
  2006年   17篇
  2005年   17篇
  2004年   20篇
  2003年   24篇
  2002年   10篇
  2001年   13篇
  2000年   5篇
  1999年   12篇
  1998年   28篇
  1997年   24篇
  1996年   29篇
  1995年   25篇
  1994年   24篇
  1993年   16篇
  1992年   4篇
  1990年   5篇
  1989年   15篇
  1988年   16篇
  1987年   13篇
  1986年   9篇
  1985年   12篇
  1984年   9篇
  1983年   8篇
  1982年   11篇
  1981年   4篇
  1980年   10篇
  1978年   7篇
  1977年   5篇
  1976年   9篇
  1975年   5篇
  1973年   6篇
  1971年   6篇
  1970年   6篇
  1965年   3篇
排序方式: 共有946条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
Assisted hatching   总被引:1,自引:0,他引:1  
Assisted hatching entails the opening or thinning of the zona pellucida before embryo transfer in order to improve the results of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). The technique can be performed mechanically, chemically or with a laser beam. A piezoelectric method has also been described. Meta-analyses of randomised trials have shown that assisted hatching increases the clinical pregnancy, implantation and on-going pregnancy rates in patients with poor prognosis for IVF and ICSI, particularly those with repeated implantation failure. The technique is not without risks, and has been associated with an increased incidence of monozygotic twinning. Nevertheless, it remains an invaluable tool in assisted reproductive technology.  相似文献   
66.
67.
Eudragit RL (ERL) and RS (ERS) are polymethacrylate co-polymers, used in film coating of sustained release dosage forms, possessing some hydrophilic properties due to the presence of quaternary ammonium groups (QAG), where ERL contains more of such groups, hence more permeable, than ERS. However, because these groups ionize in solution, they undergo electrostatic interaction with negatively charged species. This phenomenon was utilized in this study to introduce modification in the film properties of ERL and ERS by interaction with lactic acid (LA). Thermal and mechanical analyses were carried out on polymeric free films. DSC showed a shift in Tg of the film while 1H NMR spectroscopy revealed a significant deshielding in the peak of QAGs protons after interaction with LA. Stress-strain test showed an increase in three mechanical parameters of the new film (containing LA): tensile strength to modulus ratio, relative surface energy and toughness index, indicating an enhancement in the mechanical stress resistance. Tablets coated with LA-containing films showed an increase in the release rate and extent and good stability upon aging, compared to those coated with the original film.  相似文献   
68.
OBJECTIVE: To conduct a meta-analysis of randomized controlled studies to evaluate abdominal ultrasound-guided embryo transfer compared to the clinical touch method. DESIGN: Meta-analysis. SETTING: Four studies performed in academic research centers in Barcelona, Vizcaya, Hong Kong, and Madrid. PATIENT(S): A total of 2,051 patients: 1,024 received ultrasound-guided embryo transfers and 1,027 received clinical touch method transfers. INTERVENTION(S): Fourteen studies were retrieved from the literature, but only four of them fitted our selection criteria. The meta-analysis was conducted using the RevMan software with the Peto-modified Mantel-Haenszel method and the fixed effect model. MAIN OUTCOME MEASURE(S): The primary outcome measures were the clinical pregnancy and ongoing pregnancy rates. The secondary outcome measures were the incidences of ectopic pregnancies, miscarriage rate, multiple pregnancies, and difficult transfers. RESULT(S): Compared to the clinical touch method, abdominal ultrasound-guided transfer significantly increased the clinical pregnancy rate and the ongoing pregnancy rate. There was no effect on the incidence of ectopic pregnancy, multiple pregnancy, or miscarriage rate. CONCLSUION(S): Ultrasound-guided embryo transfer increases the clinical pregnancy and ongoing pregnancy rates significantly compared to the clinical touch method.  相似文献   
69.
BACKGROUND: Laminins (Lns) are a family of extracellular matrix glycoproteins located in the basement membrane (BM) of epithelial cells. They exist as heterotrimers composed of an alpha, beta, and gamma chain. Presently, five alpha (alpha1-5), three beta (beta1-3), and three gamma (gamma1-3) chains have been identified with different combinations of these chains resulting in 14 laminin heterotrimers thus far identified (1, 3-5). METHODS: In this study, using immunohistochemistry with chain-specific antibodies, we characterized the expression of the alpha1 (Lns-1/3), alpha3 (Lns 5,6,7), and alpha5 (Lns 10/11) chains in fetal, newborn, infant, prepubertal, and adult benign and malignant prostate glands. RESULTS: In general, alpha1 expression was higher in normal fetal prostate glands and declined by full-term birth, whereas the alpha3 and alpha5 chains remained highly expressed in the adult normal glands. In carcinoma alpha1 (Lns 1/3) and alpha5 (Lns 5,6,7) are lost, whereas alpha5 (Lns 10/11) persists. CONCLUSIONS: Alpha 1 (Lns 1/3) is prominent in BM, but is replaced by a laminin matrix rich in alpha3 (Lns 5,6,7) and alpha5 (Lns 10/11) in benign adult prostate glands. In carcinoma, both alpha1 (Lns-1/3) and alpha3 (Lns 5,6,7) are not expressed with persistence of a BM rich in alpha5 (Lns 10/11).  相似文献   
70.
Conclusion Our case report highlights the possibility of tackling mediastinal, pericardial and pleural problems with regional anesthesia alone even if the surgery requires opening of the pleura.  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