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   23007篇
  免费   1706篇
  国内免费   89篇
耳鼻咽喉   158篇
儿科学   780篇
妇产科学   557篇
基础医学   3344篇
口腔科学   337篇
临床医学   2808篇
内科学   5051篇
皮肤病学   494篇
神经病学   2415篇
特种医学   406篇
外科学   2028篇
综合类   134篇
一般理论   28篇
预防医学   2554篇
眼科学   257篇
药学   1552篇
中国医学   43篇
肿瘤学   1856篇
  2024年   20篇
  2023年   219篇
  2022年   391篇
  2021年   765篇
  2020年   511篇
  2019年   765篇
  2018年   787篇
  2017年   579篇
  2016年   656篇
  2015年   717篇
  2014年   914篇
  2013年   1204篇
  2012年   1953篇
  2011年   1965篇
  2010年   1043篇
  2009年   876篇
  2008年   1526篇
  2007年   1572篇
  2006年   1553篇
  2005年   1443篇
  2004年   1326篇
  2003年   1178篇
  2002年   1033篇
  2001年   152篇
  2000年   96篇
  1999年   155篇
  1998年   193篇
  1997年   140篇
  1996年   135篇
  1995年   125篇
  1994年   87篇
  1993年   90篇
  1992年   49篇
  1991年   46篇
  1990年   47篇
  1989年   54篇
  1988年   38篇
  1987年   28篇
  1986年   38篇
  1985年   27篇
  1984年   41篇
  1983年   29篇
  1982年   25篇
  1981年   25篇
  1980年   21篇
  1978年   17篇
  1976年   21篇
  1974年   15篇
  1973年   15篇
  1972年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
To date, few studies have examined the personality characteristics and clinical predictors of impulsive behaviors in eating disorders (ED). The aim of this work was to study the prevalence of a wide range of impulsive behaviors in a sample of 554 ED subjects and to examine the predictors of these behaviors. Subjects were diagnosed according to DSM-IV criteria as having anorexia nervosa restricting type (ANR; n = 183), anorexia nervosa binge eating/purging type (ANBP; n = 65), bulimia nervosa purging type (BNP; n = 244), and bulimia nervosa nonpurging type (BNNP; n = 62). Nine different types of impulsive behaviors were assessed in these groups. About 55% of the whole sample reported at least one type of impulsive behavior, 35% more than one, and about 13% more than three. According to findings, impulsive and multi-impulsive subjects are characterized by the presence of purging behavior and by specific temperamental features such as high levels of novelty seeking and low persistence. The prediction of impulsive behavior is further improved by considering the presence of a history of childhood abuse, maternal psychiatric morbidity, and some specific psychological symptoms such as maturity fears, perfectionism, depression, and obsessive-compulsive symptoms. The presence of impulsive behavior appears to be associated with overall higher levels of psychiatric symptomatology and eating psychopathology, thus indicating that they are an important feature to be considered in the assessment and treatment of ED.  相似文献   
72.
The isolation of the Popeye gene family was based on its preferential expression in striated muscle tissue. Recently, a monoclonal antibody against chick Popdc1 (also known as Bves) became available and was used in this study to comparatively analyze the expression pattern of Popdc1 at both the protein and mRNA level during early chick embryogenesis. Using whole-mount immunohistochemistry, expression in the heart was first observed at Hamburger and Hamilton (HH) stage 10 in the presumptive left ventricular segment. Cardiac expression was confined to differentiated cardiac myocytes, and undifferentiated myocytes at the anterior and posterior pole showed little expression. After looping, the outer curvature myocardium showed prominent Popdc1 staining, whereas the inner curvature was unlabeled. Despite previous reports, Popdc1 protein was not detectable at any time point in the proepicardium, epicardium, or the smooth muscle layer of the coronary vessels. Whole-mount in situ hybridization using a full-length Popdc1 probe detected novel expression domains, which have not been described previously. Popdc1 mRNA was found in Hensen's node at HH stage 4, and by HH stage 5+, expression became asymmetric. In addition, Popdc1 mRNA was found in pharyngeal endoderm and in the notochordal plate. Subsequently, beginning at HH stage 9, Popdc1 mRNA expression was found in the cardiac mesoderm and expression was maintained in the heart in a pattern very similar to the one observed by antibody staining.  相似文献   
73.
BACKGROUND: Peritonitis is a serious complication of peritoneal dialysis (PD). We studied the efficacy of imipenem/cilastatin monotherapy in the treatment of PD-related peritonitis. METHODS: We performed an open-label, randomized control study comparing imipenem/cilastatin monotherapy (treatment group) versus cefazolin plus ceftazidime (control group) in the treatment of PD peritonitis. The result was further compared to a historic group treated with cefazolin plus netilmycin. Outcome measures were primary response rate at day 10 and complete cure rate. RESULTS: We enrolled 51 patients in the treatment group, 51 in the control group, and identified 96 in the historic group. The primary response rate to the assigned antibiotics was 49.0%, 51.0%, and 49.0% for the treatment, control, and historic groups, respectively (p = 0.97). The primary response rate allowing for change in antibiotic was 82.4%, 90.2%, and 82.3%, respectively, for the three groups (p = 0.41). The complete cure rate was 72.5%, 80.4%, and 82.3%, respectively (p = 0.60). Tenckhoff catheter removal was needed in 6 cases in the treatment group, 6 cases in the control group, and 13 cases in the historic group (p = 0.90). CONCLUSIONS: We concluded that monotherapy of imipenem/cilastatin has similar efficacy compared to the two standard regimens of cefazolin plus ceftazidime or netilmycin in the treatment of PD peritonitis.  相似文献   
74.
Tissue ischemia, necrosis, and gangrene are uncommon but well-described complications of arterial catheterization in the neonate. Treatment options for progressive tissue necrosis following arterial embolization and/or vasospasm are limited in these patients secondary to unpredictable pharmacokinetics and risks associated with systemic anticoagulation or vasodilatation in newborns. We report a case of a multidose regimen of topical 2% nitroglycerin ointment for reversing severe tissue ischemia following peripheral arterial line placement. The favorable response in this infant suggests that topical nitroglycerin therapy should be considered as potential therapy to ameliorate the effects of vascular compromise following arterial line placement in neonates.  相似文献   
75.
There is a debate about the extent to which the effect of prenatal smoking on infant health outcomes is causal. Poor outcomes could be attributable to mother characteristics, which are correlated with smoking. I examine the importance of selection on the effect of prenatal smoking by using three British cohorts where the mothers' knowledge about the harms of prenatal smoking varied substantially. I find that the effect of smoking on the probability of a low birth weight birth conditional on gestation is slightly more than twice as large in 2000 compared with 1958, implying that selection could explain as much as 50% of the current association between smoking and birth outcomes. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
76.
The glucose deprivation-induced release of [3H]D-aspartate was studied in bovine and human retinas in a superfusion apparatus. [3H]D-aspartate release was significantly increased upon omitting glucose in the superfusion buffer. This effect was dependent on external Ca2+ because L- and N-type Ca2+-channel blockers, such as diltiazem (1 microM), nitrendipine (1 microM), and omega-conotoxin (100 nM), significantly reduced the effect of glucose-deprivation induced release of [3H]D-aspartate. Furthermore, while glutamate receptor agonists (L-glutamate, N-methyl-D-aspartate, but not kainate) potentiated the effects of glucose deprivation, antagonists (MK-801, MCPG, ifenprodil, and L-AP3) at these receptors blocked the glucose deprivation-induced release process. Taken together, these studies have demonstrated that under conditions of glucose deprivation, as may happen during ischemic events in vivo, the retinal glutamatergic nerve endings and/or glial cells promote the efflux of [3H]D-aspartate into the extracellular environment. This process appears to be receptor-mediated and dependent on extracellular Ca2+ and is similar to previous reports pertaining to brain tissues.  相似文献   
77.
OBJECTIVES: We aimed to investigate both nocturnal spontaneous and morning growth hormone (GH)-releasing hormone (GHRH)-induced GH secretion in children on daily glucocorticoid treatment after liver transplantation and to evaluate the effect of pyridostigmine (an acetylcholinesterase inhibitor thought to reduce hypothalamic somatostatin tone) on GH secretion in these patients. DESIGN: We performed a randomized, single-blind, cross-over study. PATIENTS: We studied three male and three female juvenile patients, within a year of orthotopic liver transplantation and under immunosuppressive glucocorticoid therapy (mean dose +/- SEM, 5.92 +/- 0.63 mg/day) and five normal children (four males, one female). MEASUREMENTS: Both nocturnal spontaneous and morning GHRH-induced GH secretion were evaluated after administration of placebo, 1 tablet p.o., or pyridostigmine, 2 mg/kg p.o. RESULTS: Spontaneous GH. Placebo: in liver transplanted children nocturnal GH secretion (mean GH level 10.8 +/- 2.0 mU/l) was not significantly different with respect to normal children (mean GH level 12.8 +/- 1.2 mU/l); pyridostigmine: nocturnal GH secretion was significantly increased as compared to placebo in subjects with liver transplantation but not in normal children. GHRH test. Placebo: liver transplanted patients showed a blunted GH response to GHRH with respect to normal children; pyridostigmine: the GH responses to GHRH (P less than 0.05) increased as compared to placebo and did not differ significantly in the two groups. CONCLUSIONS: Our data suggest a steroid-mediated increase in hypothalamic somatostatin tone in liver transplanted children.  相似文献   
78.
79.
L-2-Hydroxyglutaric acid (LGA) is the biochemical hallmark of patients affected by the neurometabolic disorder known as L-2-hydroxyglutaric aciduria (LHGA). Although this disorder is predominantly characterized by severe neurological findings and pronounced cerebellum atrophy, the neurotoxic mechanisms of brain injury are virtually unknown. In the present study, we investigated the effect of LGA, at 0.25-5mM concentrations, on total creatine kinase (tCK) activity from cerebellum, cerebral cortex, cardiac muscle and skeletal muscle homogenates of 30-day-old Wistar rats. CK activity was measured also in the cytosolic (Cy-CK) and mitochondrial (Mi-CK) fractions from cerebellum. We verified that tCK activity was significantly inhibited by LGA in the cerebellum, but not in cerebral cortex, cardiac muscle and skeletal muscle. Furthermore, CK activity from the mitochondrial fraction was inhibited by LGA, whereas that from the cytosolic fraction of cerebellum was not affected by the acid. Kinetic studies revealed that the inhibitory effect of LGA on Mi-CK was non-competitive in relation to phosphocreatine. Finally, we verified that the inhibitory effect of LGA on tCK was fully prevented by pre-incubation of the homogenates with reduced glutathione (GSH), suggesting that this inhibition is possibly mediated by oxidation of essential thiol groups of the enzyme. Considering the importance of creatine kinase activity for energy homeostasis, our results suggest that the selective inhibition of this enzyme activity by increased levels of LGA could be possibly related to the cerebellar degeneration characteristically found in patients affected by L-2-hydroxyglutaric aciduria.  相似文献   
80.
Separate investigations have suggested that olanzapine, a D4 antagonist, decreases craving after a priming dose of alcohol and that the DRD4 variable number of tandem repeats (VNTR) polymorphism influences the expression of craving after a priming dose of alcohol. The present study tested the hypothesis that olanzapine may be differentially effective at reducing cue-elicited craving based on individual differences in DRD4 VNTR in a sample of heavy social drinkers. Participants were randomly assigned to receive olanzapine (5 mg) or a control medication (cyproheptadine, 4 mg) prior to consuming three alcoholic drinks. Participants completed subjective measures of craving and euphoria after each drink. Participants who were homozygous or heterozygous for the 7 (or longer) repeat allele of the DRD4 VNTR were classified as DRD4 L, while the other participants were classified as DRD4 S. The findings indicated that olanzapine reduces craving for alcohol at baseline for both DRD4 S and DRD4 L individuals, but only reduces craving after exposure to alcohol cues and after a priming dose of alcohol for DRD4 L individuals.  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