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   2510篇
  免费   111篇
  国内免费   16篇
耳鼻咽喉   8篇
儿科学   52篇
妇产科学   92篇
基础医学   349篇
口腔科学   36篇
临床医学   169篇
内科学   414篇
皮肤病学   28篇
神经病学   334篇
特种医学   52篇
外科学   336篇
综合类   5篇
预防医学   344篇
眼科学   27篇
药学   225篇
中国医学   2篇
肿瘤学   164篇
  2022年   12篇
  2021年   48篇
  2020年   14篇
  2019年   29篇
  2018年   48篇
  2017年   41篇
  2016年   48篇
  2015年   51篇
  2014年   72篇
  2013年   80篇
  2012年   161篇
  2011年   167篇
  2010年   89篇
  2009年   73篇
  2008年   136篇
  2007年   165篇
  2006年   153篇
  2005年   170篇
  2004年   155篇
  2003年   140篇
  2002年   139篇
  2001年   36篇
  2000年   36篇
  1999年   27篇
  1998年   25篇
  1997年   21篇
  1996年   11篇
  1992年   24篇
  1991年   25篇
  1990年   20篇
  1989年   14篇
  1988年   20篇
  1987年   23篇
  1986年   19篇
  1985年   24篇
  1984年   12篇
  1983年   14篇
  1982年   11篇
  1979年   24篇
  1978年   17篇
  1977年   9篇
  1976年   15篇
  1975年   22篇
  1974年   18篇
  1973年   20篇
  1972年   11篇
  1969年   10篇
  1968年   11篇
  1932年   9篇
  1931年   12篇
排序方式: 共有2637条查询结果,搜索用时 15 毫秒
71.
1. The offspring of female rats treated with a single dose of benzpyrene on day 15 of gestation showed in adulthood a significant relative decrease in the number of thymic glucocorticoid receptors, without an appreciable decrease in binding affinity. 2. There is experimental evidence that exposure to a hormone analogue in the early stage of organogenesis effects receptor development and the maternal organism fails to confer protection against that untoward influence.  相似文献   
72.
PURPOSE: To correlate prenatal sonographic diagnosis of cystic lung malformations with fetopathologic findings after termination of pregnancy. METHODS: We retrospectively analyzed the data of 16 terminated cases in which a cystic lung lesion was diagnosed pre- or postnatally. RESULTS: On average, prenatal diagnosis was established on the 21(st) gestational week (range, 19-26 weeks). The cause of termination was severe polyhydramnios in 4 cases, nonimmune fetal hydrops in 4 cases, other congenital malformation in 5 cases (renal malformation, 2 cases; congenital diaphragmatic hernia, 3 cases), and obstetrical conditions (intrauterine death, placental abruption, spontaneous abortion) in 3 cases. In 11 cases, congenital cystic adenomatoid malformation (CCAM) was the presumptive prenatal diagnosis. Autopsy confirmed the prenatal diagnosis in 6 of them, while in the other 5 cases, an enteric cyst, a laryngeal atresia, an unidentified tumor, a pulmonary hypoplasia, and an extralobar pulmonary sequestration were found on histologic examination. On the other hand, the autopsy revealed CCAM in those 5 cases in which other malformations were suggested prenatally. CONCLUSION: The prenatal sonographic diagnosis of CCAM is difficult. Our cases emphasize the important role of fetopathology even today in the verification of prenatal diagnosis based on sonographic examinations.  相似文献   
73.
BACKGROUND: The standard technique of radiotherapy (RT) after breast conserving surgery (BCS) is to treat the entire breast up to a total dose of 45-50 Gy with or without tumor bed boost. The majority of local recurrences occur in close proximity to the tumor bed. Thus, the necessity of whole breast radiotherapy has been questioned, and several centers have evaluated the feasibility and efficacy of sole tumor bed irradiation. The aim of this study was to review the current status, controversies, and future prospects of tumor bed irradiation alone after breast conserving surgery. MATERIAL AND METHODS: Published prospective trials evaluating the feasibility and efficacy of radiotherapy confined to the tumor bed following breast conserving surgery were reviewed in order to analyze treatment results. RESULTS: In three earlier studies, using tumor bed radiotherapy for unselected patients, the incidence of intra-breast relapse was reported in the range of 15.6-37%. However, in nine prospective phase I-II trials, sole brachytherapy (BT) with different dose rates, strict patient selection, and meticulous quality assurance, resulted in 95.6-100% local control rates. To date, only one phase III protocol has been initiated comparing the efficacy of tumor bed brachytherapy alone with conventional whole breast radiotherapy. The ideal extend of the planning target volume (PTV) for tumor bed radiotherapy alone has not been established yet. In most series, PTV was defined as the excision cavity with generous (1-3 cm) safety margins. Minimal requirement for PTV localization is the use of titanium clips to mark the walls of the excision cavity intraoperatively, but the combination of clip demarcation and three-dimensional (3-D) visual information obtained from cross-sectional images seems to be the best method to determine the target volume. 3-D virtual brachytherapy is also a promising method to minimize the chance of geographic miss. Recently developed techniques, such as intraoperative radiotherapy (IORT), as well as accelerated 3-D conformal external beam radiation therapy (3-D-CRT) were also found to be feasible for tumor bed radiotherapy alone. CONCLUSIONS: In spite of the existing arguments against limiting radiotherapy to the tumor bed after breast conserving surgery, results of phase I-II studies suggest that tumor bed radiotherapy alone might be an appropriate treatment option for selected breast cancer patients. Whole breast radiotherapy remains the standard radiation modality used in the treatment of breast cancer, and brachytherapy as the sole modality should be considered as investigational. Further phase-III trials are suggested to determine the equivalence of sole tumor bed radiotherapy, compared with whole breast radiotherapy. Preliminary results with recently developed techniques (CT-image based conformal brachytherapy, 3-D virtual brachytherapy, IORT, 3-D-CRT) are promising. However, more experience is required to define whether these methods might improve outcome for patients treated with tumor bed radiotherapy alone.  相似文献   
74.
75.
76.
Tourette syndrome (TS) is a neurodevelopmental disorder with a complex genetic etiology. Through an international collaboration, we genotyped 42 single nucleotide polymorphisms (p < 10−3) from the recent TS genomewide association study (GWAS) in 609 independent cases and 610 ancestry‐matched controls. Only rs2060546 on chromosome 12q22 (p = 3.3 × 10−4) remained significant after Bonferroni correction. Meta‐analysis with the original GWAS yielded the strongest association to date (p = 5.8 × 10−7). Although its functional significance is unclear, rs2060546 lies closest to NTN4, an axon guidance molecule expressed in developing striatum. Risk score analysis significantly predicted case–control status (p = 0.042), suggesting that many of these variants are true TS risk alleles. Ann Neurol 2014;76:310–315  相似文献   
77.
It is generally believed that proopiomelanocortin (POMC) is expressed exclusively by neurons in the adult rodent brain. Unbeknownst to most researchers, however, Pomc in situ hybridization studies in the rat show specific labeling in the ventral wall of the hypothalamic third ventricle, which is formed by specialized ependymal cells, called tanycytes. Here we characterized this non‐neuronal POMC expression in detail using in situ hybridization and immunohistochemical techniques, and report two unique characteristics. First, POMC mRNA and precursor protein expression in non‐neuronal cells varies to a great degree as to the extent and abundance of expression. In brains with low‐level expression, POMC mRNA and protein was largely confined to a population of tanycytes within the infundibular stalk/caudal median eminence, termed here γ tanycytes, and a subset of closely located β and α2 tanycytes. In brains with high‐level expression, POMC mRNA and protein was observed in the vast majority of α2, β, and γ tanycytes. This variability was observed in both adult males and females; of 41 rats between 8 and 15 weeks of age, 17 had low‐, 9 intermediate‐, and 15 high‐level POMC expression in tanycytes. Second, unlike other known POMC‐expressing cells, tanycytes rarely contained detectable levels of adrenocorticotropin or α‐melanocyte–stimulating hormone. The results indicate either a dynamic spatiotemporal pattern whereby low and high POMC syntheses in tanycytes occur periodically in each brain, or marked interindividual differences that may persist throughout adulthood. Future studies are required to examine these possibilities and elucidate the physiologic importance of POMC in tanycytes. J. Comp. Neurol. 525:411–441, 2017. © 2016 Wiley Periodicals, Inc.  相似文献   
78.
New methods for the diagnosis of acute pulmonary embolism   总被引:1,自引:0,他引:1  
INTRODUCTION: Pulmonary embolism is a high mortality cardiovascular disease, which is difficult to diagnose even today. AIM AND METHOD: In this study the symptoms and the results of diagnostic methods were analysed in 81 patients with acute pulmonary embolism, admitted during a one-year period to Kaposi Mór County Hospital. The patient records were examined with special emphasis on the diagnostic value of novel methods such as D-dimer assay and chest computed tomography scanning along with the routine techniques used in the management of pulmonary embolism. RESULTS: In all patients ECG, in 88% of the cases chest X-ray, in 57% blood gas analysis and in 53% D-dimer assay results were evaluated. 14.8% of the patients died during hospitalisation. The following diagnostic imaging procedures were undertaken: in 80.2% of the cases lung scan, in 59.3% echocardiography and in 8.7% of the cases spiral computed tomography scan were prepared. In 12.3% of all cases thrombolysis proved necessary. The results were compared with data from International Cooperative Pulmonary Embolism Registry Study, which analyses 2454 patient cases. CONCLUSION: It is foreseen that the increasing use of echocardiography, lower limb ultrasound and highly informative spiral computed tomography scanning as an additional means in pulmonary embolism diagnostics may in some cases spare the use of pulmonary scintigraphy.  相似文献   
79.
80.
Cystic fibrosis (CF) is the most common autosomal recessive disorder in Caucasians. The most frequent mutation associated with cystic fibrosis has been identified as the 3 bp deletion Delta F 508. While existing polymerase chain reactions (PCR) (allele specific amplification) used to screen for CF are both sensitive and specific, we tested the prenatal application of fluorescent polymerase chain reaction and subsequent DNA fragment analysis that appears to be fast and sensitive. DNA samples (n=146) isolated from amniotic fluid (n=108), chorion villus biopsies (n=6), and human peripheral blood (n=32) were analyzed for the presence of Delta F 508 using the fluorescent method. Of these, 10 carriers of Delta F 508 mutation were detected. We achieved the same results with conventional PCR and fluorescent PCR.  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