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   6604篇
  免费   347篇
  国内免费   17篇
耳鼻咽喉   33篇
儿科学   191篇
妇产科学   185篇
基础医学   1054篇
口腔科学   264篇
临床医学   548篇
内科学   1231篇
皮肤病学   132篇
神经病学   674篇
特种医学   170篇
外科学   528篇
综合类   60篇
预防医学   700篇
眼科学   313篇
药学   494篇
中国医学   28篇
肿瘤学   363篇
  2023年   33篇
  2022年   88篇
  2021年   132篇
  2020年   85篇
  2019年   118篇
  2018年   139篇
  2017年   96篇
  2016年   140篇
  2015年   185篇
  2014年   208篇
  2013年   286篇
  2012年   453篇
  2011年   532篇
  2010年   265篇
  2009年   241篇
  2008年   435篇
  2007年   432篇
  2006年   405篇
  2005年   402篇
  2004年   364篇
  2003年   310篇
  2002年   326篇
  2001年   82篇
  2000年   63篇
  1999年   88篇
  1998年   104篇
  1997年   84篇
  1996年   68篇
  1995年   52篇
  1994年   49篇
  1993年   46篇
  1992年   46篇
  1991年   32篇
  1990年   22篇
  1989年   20篇
  1988年   43篇
  1987年   27篇
  1986年   25篇
  1985年   26篇
  1984年   21篇
  1983年   22篇
  1982年   20篇
  1981年   16篇
  1980年   24篇
  1979年   17篇
  1978年   15篇
  1974年   16篇
  1972年   16篇
  1968年   17篇
  1966年   16篇
排序方式: 共有6968条查询结果,搜索用时 15 毫秒
31.
European Journal of Clinical Microbiology & Infectious Diseases - This study determined the carriage rates and antimicrobial resistance (AMR) genes of enterococci from...  相似文献   
32.
4-Phenyl-1-(4-phenylbutyl)piperidine(4-PPBP) is a very potent ligand for σ (Sigma) receptors. The present study was undertaken to evaluate [3H]4-PPBPas a radioligand for in vivo labeling of cerebral σ receptors. After intravenous administration of [3H]4-PPBP to mice, there is high uptake of radioactivity in the brain. The regional distribution of radioactivity in the brain 2 h after intravenous injection of [3H]4-PPBP parallels the in vitro binding of the radioligand in rat brain (pons/medulla > cerebellum ≥ prefrontal cortex ≥ parietal cortex > hypothalamus > olfactory tubercle ≥ thalamus > hippocampus > striatum). Pretreatment with haloperidol (2 mg/kg) significantly decreases the radioactivity measured in the brain 30–120 min after injection of [3H]4-PPBP. Pretreatment with unlabeled 4-PPBP or ifenprodil also significantly decreases radioactivity in the brain 2 h after injection of [3H]4-PPBP, in a dosedependent manner. The in vivo binding of [3H]4-PPBP in the brain also is significantly inhibited by SL 82.0715, BMY 14802, 1,3-di-o-tolylguanidine (DTG), and (+)-enantiomers of pentazocine, SKF 10,047, and 3-PPP, but not by the corresponding (?)-enantiomers, consistent with stereoselectivity of inhibition obtained in in vitro binding studies. In contrast, pretreatment with dizocilpine and spiperone does not inhibit in vivo binding of [3H]4-PPBP. The results indicate that [3H]4-PPBP would be a suitable radioligand for in vivo labeling of σ receptors in brain. © 1995 Wiley-Liss, Inc.
  • 1 This article is a US Government work and, as such, is in the public domain in the United States of America
  • .  相似文献   
    33.
    The authors studied a sample of students entering the first grade in the Osasco public school system in order to determine both the prevalence of anemia and nutritional status. Osasco is part of the Greater S o Paulo Metropolitan Area. Diagnosis of anemia was made through the hemoglobin concentration of blood from digital puncture. World Health Organization (WHO) levels were used to define anemia. Nutritional Status assessment. was made through weight/age and height/age indices, using Z score distribution and the National Center for Health Statistics (NCHS) reference levels. Prevalence of anemia was 51%. Prevalence levels varied according to the schools' geographic location: 56.9% in peripheral neighborhoods and 41.7% in central areas. Children with illiterate parents had a higher prevalence of this condition. Risk of anemia was higher for children who were over eight years of age when entering the first grade. Acute malnutrition was not found. Prevalence was higher than expected and points to the urgent need to establish an anemia control program for schoolchildren in this population.  相似文献   
    34.
    In order to better understand the natural history of chronic functional constipation, a questionnaire was applied to 163 children and infants, before beginning standardized treatment. Median age (range) at start was 3 mo(0-108 mo) but age at arrival at the Pediatric Gastroenterology Unit was 53 mo(2-146 mo). In 62.4% of the cases symptoms began before or up to 3 mo after cow's milk introduction and rarely around (-/+ 6 mo) toilet training. Possible complications appeared progressively, often at preschool or school age or as the first noticeable manifestation: recurrent abdominal pain (61.1%), fecal soiling (45.4%), fecal blood (35%), enuresis (23.3%), vomiting (19%), urinary infection (17.9%), urinary retention (8.6%). Abdominal distension was rarely detected on physical examination and was usually discrete. In conclusion, children attended in Botucatu begin their constipation at an early age, frequently associated with weaning,and important complications may ensue along years. This evolution should be avoided by prevention and early treatment of constipation.  相似文献   
    35.
    36.
    Background: The present study was performed to investigate the ultrastructure of deep retinal layers and choroid corresponding to the parapapillary chorioretinal atrophy in eyes with secondary angle-closure glaucoma. Methods: The glaucomatous eyes included two eyes enucleated due to iris ring melanoma with high intraocular pressure and one eye with neovascular glaucoma enucleated due to ocular pain. The control eyes included one eye enucleated due to choroidal malignant melanoma with normal intraocular pressure and one eye enucleated during surgery for supramandibular carcinoma. These eyes were studied with light and electron microscopy. Results: In the region of parapapillary chorioretinal atrophy of glaucomatous eyes, the retinal pigment epithelial cells showed degenerative changes, such as loss of basal in foldings and microvilli, degenerated mitochondria, vacuolar degeneration and irregular distribution of melanin granules. The photoreceptors were decreased in number in this area of glaucomatous eyes. The lumen of the choriocapillary vessels adjacent to the optic nerve was collapsed. Conclusion: These results elucidate the fine structures of deep retina and choroid in the region of parapapillary chorioretinal atrophy of glaucomatous eyes, and suggest that the reduced choroidal perfusion might be the pathogenetic mechanism of glaucomatous parapapillary chorioretinal atrophy.  相似文献   
    37.
    Summary The classical surgical treatment of unicameral bone cysts of the humerus with curettage and bone grafting is unreliable with approximately 40% failure rate. The author describes a technique of subperiosteal diaphyseal and metaphyseal resection and replacement with a section of fibula maintained in position with an intramedullary nail and further supported by massive tibial cortical and cancellous grafting. Consistent incorporation of the graft and excellent remodelling were observed in 36 patients so treated. No complications or recurrence were reported.
    Résumé Le traitement chirurgical «classique» des kystes solitaires de l'humérus par curettage et greffe osseuse ne donne pas des résultats constants, puisqu'il comporte environ 40% d'échecs. L'auteur décrit une technique de résection sous-périostée, diaphysaire et métaphysaire, avec remplacement par un fragment de péroné maintenu par enclouage centro-médullaire et complété par des greffons tibiaux cortico-spongieux. Une parfaite incorporation de la greffe et un excellent remodelage ont été obtenus dans les 36 cas traités de cette manière. Il n'y a eu ni complications, ni récidives.
      相似文献   
    38.
    Zusammenfassung Mit Hilfe der beschriebenen Technik gelang es, Linsenepithelien über 40 Passagen zu züchten; zugleich fanden morphologische Alterungsveränderungen und Sauerstoffverbrauch der Zellen im Warburg-Apparat Beachtung. Vergleichbare Untersuchungen sind derzeit nicht bekannt. Morphologisch überwogen Alterationen wie Vergrößerung des Zelleibes neben bekannten Degenerationszeichen. Der Sauerstoffverbrauch von 2 l pro Stunde pro 105 Zellen zeigte sich in konstanter Höhe bis zur 39. Passage und sank dann abrupt auf etwa ein Viertel. Nachdem die Zellen ohne ersichtlichen Grund danach plötzlich starben, liegt die Folgerung nahe, daß der aerobe Stoffwechsel der Linsenepithelien unabhängig von ihrem Alter und ohne sich signifikant abzeichnenden Tagesrhythmus mit ihrem Überleben verbunden erscheint.
    Oxygen consumption and aging in longterm cultures of lens epithelia
    By means of the described technique lens epithelia were cultured in 40 subcultures; at the same time, both the morphological aging processes and oxygen consumption of the cells, were observed using the Warburg respirometer. To date comparable studies are not available. Morphologically, cell enlargement took place in conjunction with signs of degeneration. Oxygen consumption of 2 l per hour per 105 cells ±0.8 remained at a constant level without any significant diurnal rhythm up to subculture 39 and then suddenly fell to about one-fourth of the initial value. As the cells died of an unknown cause, it was concluded that the aerobic metabolism of lens epithelia seemed to be linked to survival without being age related.


    Herrn Prof. Dr. E. Schreck, dem damaligen Direktor der Klinik, in Dankbarkeit zum 70. Geburtstag  相似文献   
    39.
    Diffuse neuronal migration disorders associated with epilepsy can now be recognized by modern neuroimaging techniques, particularly high-resolution MRI. We report 10 patients with a recently described MRI picture of continuous or generalized band heterotopia underlying the cortical mantle, giving the appearance of a "double cortex." They have epilepsy, and almost all have mental retardation. The epileptic disorder varies in nature and degree of severity. Patients may present with infantile spasms, a Lennox-Gastaut syndrome, or other forms of secondary generalized or multifocal epilepsy. Response to medical treatment is variable. Callosotomy may lead to considerable reduction of drop attacks, present in 60%. Mental retardation is usually mild or moderate, and only rarely severe. It correlates with the type of epileptic syndrome, and is greater in patients with more disorganized cortex overlying the heterotopia. Recognition of this entity by MRI is important for appropriate diagnosis of the epileptic disorder, planning of therapeutic strategy, and prognosis.  相似文献   
    40.
    PURPOSE: Neurofibromatosis type 1 (NF1) is characterized by systemic development of neurofibromas. Early clinical diagnosis can be ambiguous, and genetic diagnosis can be prohibitively difficult. Dysregulation of a number of growth factors has been suggested to be a mechanism of pathogenesis. This study was performed to assess the contribution of circulating growth factors for diffuse tumorigenesis and the diagnostic value of circulating growth factor identification in serum. EXPERIMENTAL DESIGN: The growth stimulation of neurofibroma-derived cells by serum from NF1 patients was tested, and serum growth factor levels in a cohort of NF1 patients (n = 39) between the ages of 7 and 70 years were analyzed. RESULTS: Concentrations of midkine (MK) and stem cell factor, but not epidermal growth factor, were substantially increased in serum of NF1 patients when compared with healthy controls. Within the NF1 group, MK levels increased dramatically at puberty from an average of 0.79 ng/mL in patients <18 years to 1.18 ng/mL in patients >18 years old. Stem cell factor and MK concentrations above a defined threshold in serum of NF1 patients are of diagnostic benefit for 96% of patients in the cohort tested. Furthermore, serum from NF1 patients enhanced proliferation of human neurofibroma-derived primary Schwann cells and endothelial cells substantially better than normal serum. CONCLUSIONS: Enhanced circulating growth factor levels contribute to diffuse tumorigenesis in NF1 and may provide the basis for molecular diagnosis.  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