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   3050篇
  免费   137篇
  国内免费   24篇
耳鼻咽喉   11篇
儿科学   81篇
妇产科学   100篇
基础医学   456篇
口腔科学   45篇
临床医学   284篇
内科学   534篇
皮肤病学   15篇
神经病学   396篇
特种医学   78篇
外科学   405篇
综合类   19篇
一般理论   1篇
预防医学   304篇
眼科学   15篇
药学   270篇
中国医学   3篇
肿瘤学   194篇
  2022年   36篇
  2021年   57篇
  2020年   25篇
  2019年   37篇
  2018年   56篇
  2017年   43篇
  2016年   59篇
  2015年   65篇
  2014年   89篇
  2013年   111篇
  2012年   201篇
  2011年   203篇
  2010年   100篇
  2009年   100篇
  2008年   193篇
  2007年   212篇
  2006年   175篇
  2005年   191篇
  2004年   172篇
  2003年   148篇
  2002年   151篇
  2001年   44篇
  2000年   36篇
  1999年   29篇
  1998年   37篇
  1997年   28篇
  1996年   16篇
  1995年   18篇
  1994年   24篇
  1992年   28篇
  1991年   18篇
  1990年   15篇
  1989年   20篇
  1988年   31篇
  1987年   32篇
  1986年   24篇
  1985年   37篇
  1984年   21篇
  1983年   22篇
  1981年   14篇
  1979年   26篇
  1978年   21篇
  1976年   13篇
  1975年   19篇
  1974年   26篇
  1973年   15篇
  1972年   19篇
  1971年   19篇
  1969年   17篇
  1968年   13篇
排序方式: 共有3211条查询结果,搜索用时 17 毫秒
991.
Peptic ulcer     
Várvölgyi C 《Orvosi hetilap》2006,147(28):1334-1335
  相似文献   
992.
Hormonal imprinting takes place perinatally at the first encounter between the hormone and its target receptor. This is needed for the normal finishment of the maturation of the receptor-signal transduction system. In excess of foreign molecules, which can also bind to the receptor, faulty imprinting develops with life-long consequences. Genistein, a soybean phytosteroid (isoflavone), has estrogen-like effects and can be bound by steroid receptors. In the present experiments, single neonatal treatment (imprinting) with 20 microg of genistein, or combined treatment with 20 microg of genistein+20 microg of benzpyrene was done and liver and thymus glucocorticoid receptors of adult male and female rats and uterine estrogen receptors were studied. There was no difference in the binding capacity of uterine estrogen receptors. Genistein treatment alone caused a significant reduction of liver glucocorticoid receptor density in males; however, there were no other significant alterations. After combined genistein+benzpyrene treatment, more.than half of the thymus and liver glucocorticoid receptor values significantly changed. The results call attention to the imprinting-modifying effect of a second (environmental) imprinter.  相似文献   
993.
The glucocorticoid receptor of the newborn thymus binds dexamethasone with the same specificity, as the adult ones. The best competitors of dexamethasone on the glucocorticoid receptor are dexamethasone itself and mifepristone (RU486). Estradiol can compete with dexamethasone on the glucocorticoid receptor. This is true in the case of newborn or adolescent thymus alike. Allylestrenol can slightly compete with dexamethasone on the glucocorticoid receptor in newborn, however this does not occur in adolescents. The other ligands - causing imprinting or imprinting like phenomenon earlier -- as tocopherol, menadione, retinoic acid, vitamin D(3) -- do not compete in vitro with dexamethasone on the thymic glucocorticoid receptor in newborn and adolescent animals. Possibilities of imprinting mechanism, considering the results are discussed.  相似文献   
994.
Galactokinase deficiency is an inborn error of metabolism that, if untreated, results in the development of cataracts in the first weeks of life. The disorder is rare worldwide, but has a high incidence among the Roma (Gypsies). In 1999, we reported the founder Romani mutation, P28T, identified in affected families from Bulgaria. Subsequent studies have detected the same mutation in Romani patients from different European countries. The screening of 803 unrelated control individuals of Romani ethnicity from Bulgaria, Hungary, and Spain has shown an overall carrier rate of 1:47 and an expected incidence of affected births about 1:10,000. Using disease haplotype analysis, the age of the P28T mutation was estimated at 750 y, preceding the splits of the proto-Roma into the numerous populations resident in Europe today. The findings suggest that the mutation has spread with the early diaspora of the Roma throughout Europe. Superimposed on this old distribution pattern is the new migration wave of the last decade, with large numbers of Roma moving to Western Europe as a result of the economic changes in the East and the wars in former Yugoslavia. The changing demographic pattern of Romani minorities can be expected to lead to a homogenization of the incidence of "private" Romani disorders and founder mutations. The P28T mutation is thus likely to account for a high proportion of galactokinase deficiency cases across Europe. Mutation-based pilot newborn screening programs would provide current incidence figures and help to design long-term prevention of infantile cataracts due to galactokinase deficiency.  相似文献   
995.
OBJECTIVES: Triploidy is a common cause of spontaneous abortion in the very early stages of pregnancy. It is very rare for a prenatal diagnostic center to discover triploidy in the third trimester of pregnancy. A pregnant woman in the third trimester was referred to our genetic counselling clinic because of abnormal ultrasound findings. We planned to test for the most common chromosomal abnormalities. METHODS: We performed ultrasound examination, chorionic villus sampling, karyotyping and fluorescent-polymerase chain reaction (F-PCR) and fragment analysis. RESULTS: We diagnosed a 69,XXX karyotype fetus in the 31st week of gestation, based on a short tandem repeat (STR) pattern typical for triploidy, which was confirmed by karyotyping. The comparison of the fetal and parental STR patterns showed maternal origin of the extra haploid chromosome set. CONCLUSIONS: STR analysis of fluorescent-PCR and DNA fragment analysis is a rapid and reliable alternative to karyotyping for detection of certain aneuploidies. The method is also suitable for the determination of the origin of the extra chromosome set.  相似文献   
996.
Cellular biology of somatostatin receptors   总被引:24,自引:0,他引:24  
Somatostatin, and the recently discovered neuropeptide cortistatin, exert their physiological actions via a family of six G protein-coupled receptors (sst1, sst2A, sst2B, sst3, sst4, sst5). Following the cloning of somatostatin receptors significant advances have been made in our understanding of their molecular, pharmacological and signaling properties although much progress remains to be done to define their physiological role in vivo. In this review, the present knowledge regarding neuroanatomical localization, signal transduction pathways, desensitization and internalization properties of somatostatin receptors is summarized. Evidence that somatostatin receptors can form homo- and heterodimers and can physically interact with members of the SSTRIP/Shank/ProSAP1/CortBP1 family is also discussed.  相似文献   
997.
Allium victorialis L. (Liliaceae, "Hon-Gyoujya Nin-Niku" in Japanese) was successively extracted with hexane, acetone, methanol and 70% methanol and the extracts were further separated into a total of twenty-five fractions by silica gel and ODS column chromatographies. The biological activities of these four extracts and 25 column fractions were compared. The cytotoxic activity of all extracts and fractions against two oral tumor cell lines was significantly higher than that against normal human gingival fibroblasts, suggesting their tumor-specific action. Three methanol column fractions [M2, M3, M6] and a 70% methanol column fraction [70M6] most effectively reversed the multidrug resistance (MDR) against L5178 mouse T cell lymphoma. The electron spin resonance (ESR) spectroscopy showed that methanol column fractions and 70% methanol extracts produced the highest amount of radical(s) and most efficiently scavenging O2*-, generated by the hypoxanthine-xanthine reaction system, suggesting that the same substances in these fractions display both prooxidant and antioxidant properties. They showed no anti-human immunodeficiency virus (HIV) or anti-Helicobacterpylori activity. These data suggest the medicinal efficacy of Allium victorialis extract.  相似文献   
998.
In this article, we review the current status, indication, technical aspects, controversies, and future prospects of boost irradiation after breast conserving surgery (BCS). BCS and radiotherapy (RT) of the conserved breast became widely accepted in the last decades for the treatment of early invasive breast cancer. The standard technique of RT after breast conservation is to treat the whole breast up to a total dose of 45 to 50 Gy. However, there is no consensus among radiation oncologists about the necessity of boost dose to the tumor bed. Generally accepted criteria for identification of high risk subgroups, in which boost is recommended, have not been established yet. Further controversy exists regarding the optimal boost technique (electron vs. brachytherapy), and their impact on local tumor control and cosmesis. Based on the results of numerous retrospective and recently published prospective trials, the European brachytherapy society (GEC-ESTRO), as well as the American Brachytherapy Society has issued their guidelines in these topics. These guidelines will help clinicians in their medical decisions. Some aspects of boost irradiation still remain somewhat controversial. The final results of prospective boost trials with longer follow-up, involving analyses based on pathologically defined subgroups, will clarify these controversies. Preliminary results with recently developed boost techniques (intraoperative RT, CT-image based 3D conformal brachytherapy, and 3D virtual brachytherapy) are promising. However, more experience and longer follow-up are required to define whether these methods might improve local tumor control for breast cancer patients treated with conservative surgery and RT.  相似文献   
999.
AIMS: This study was designed to compare the prenatal ultrasound findings and postmortem pathologic findings of fetuses with trisomy 18. STUDY DESIGN: Of 22,150 fetal chromosome analyses, 70 fetuses with trisomy 18 were diagnosed between 1990 and 2004. Sonographic and perinatal autopsy findings were compared by organ system and their correlation was assigned to 1 of 3 categories. RESULTS: There were 164 separate major structural abnormalities found on autopsy. Of them, sonography detected 72 (43.9%). Among major defects the agreement was more than 75% of all abnormalities of these systems: central nervous system (80%), abdominal abnormalities (87.5%) and cystic hygroma (100%). Whereas, the sensitivity of sonography was lower in these organ systems: cardiac system (66.6%), facial abnormalities (26.3%), urinary system (27.3%) and extremities (8.7%). The rate of additional findings at autopsy was 56.1% and involved mainly 2 organ systems: face (including ear) and extremities (including hands and feet). Some ultrasound findings (n=15) were not confirmed at autopsy in our series. CONCLUSIONS: This study confirms that perinatal autopsy provides additional information in many fetuses with trisomy 18. Besides obstetricians, pediatricians and geneticists, specialized perinatal pathologists have an important role in the multidisciplinary management of prenatally diagnosed fetal malformations. In addition, examining the correlation between sonography and pathologic findings may indicate potential markers for sonographic screening of trisomy 18.  相似文献   
1000.
This study tested the hypothesis that nitric oxide (NO) synthesized from inducible NO synthase (iNOS) is responsible for the cardiac dysfunction observed after burn and smoke inhalation injury. Twelve sheep received 40% third-degree burn and smoke inhalation under halothane anesthesia. The animals were divided into two groups: a MEG group [iNOS was inhibited with mercaptoethylguanidine (MEG), a selective inhibitor of iNOS, n=6] and a control group (n=6). The control group showed a significant increase in NO2/NO3 (NOx) concentration, metabolite of NO, in plasma after 24 h, whereas the MEG group did not. In the control group, cardiac depression was observed immediately after injury associated with hemoconcentration. Cardiac function returned to a normal level within 6 h following injury. In the control group cardiac dysfunction was observed again after 24 h although the hemoconcentration peaked at 24 h after injury and then began to resolve. In the MEG group, cardiac depression and hemoconcentration were not observed. The present data suggest that cardiac depression seen with this combination injury consists of two phases and that the later phase is mediated by iNOS–NO.  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