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   969篇
  免费   50篇
  国内免费   6篇
耳鼻咽喉   11篇
儿科学   38篇
妇产科学   58篇
基础医学   114篇
口腔科学   6篇
临床医学   74篇
内科学   154篇
皮肤病学   18篇
神经病学   52篇
特种医学   31篇
外科学   276篇
综合类   40篇
一般理论   2篇
预防医学   49篇
眼科学   16篇
药学   37篇
  1篇
中国医学   16篇
肿瘤学   32篇
  2023年   4篇
  2022年   11篇
  2021年   19篇
  2020年   6篇
  2019年   17篇
  2018年   12篇
  2017年   13篇
  2016年   13篇
  2015年   15篇
  2014年   19篇
  2013年   28篇
  2012年   56篇
  2011年   52篇
  2010年   38篇
  2009年   38篇
  2008年   65篇
  2007年   63篇
  2006年   63篇
  2005年   44篇
  2004年   43篇
  2003年   37篇
  2002年   41篇
  2001年   41篇
  2000年   32篇
  1999年   23篇
  1998年   12篇
  1997年   8篇
  1996年   8篇
  1995年   7篇
  1994年   8篇
  1993年   6篇
  1992年   18篇
  1991年   21篇
  1990年   15篇
  1989年   21篇
  1988年   19篇
  1987年   21篇
  1986年   20篇
  1985年   12篇
  1984年   5篇
  1983年   8篇
  1982年   2篇
  1980年   2篇
  1979年   3篇
  1978年   7篇
  1973年   2篇
  1971年   1篇
  1969年   1篇
  1966年   1篇
  1958年   1篇
排序方式: 共有1025条查询结果,搜索用时 15 毫秒
101.
PURPOSE: An unexplained increase in the incidence of hypospadias has been reported, and yet to our knowledge the molecular events and their regulation leading to hypospadias remain unknown, although environmental compounds capable of endocrine activity are suspected. We screened on a global scale abnormalities in gene expression in human hypospadiac tissue compared to those in nonhypospadiac tissue. Additionally, microarray analysis of tissue from a pair of fraternal twins, including 1 with and 1 without hypospadias, served as a control for genetic variability. We hypothesized that gene expression would differ between hypospadiac vs nonhypospadiac tissue and fraternal twin data would show patterns similar to those of group data on hypospadiac and nonhypospadiac tissue. MATERIALS AND METHODS: Microarray analysis was performed on tissue from patients with and without hypospadias, and from a pair of fraternal twins, including 1 with and 1 without hypospadias. Analysis incorporated the expression of 22,000 genes. RESULTS: We found significant differences in gene expression, specifically with a group of genes, including CYR61, CTGF, ATF3 and GADD45beta, known to be responsive to estrogen or to interact with estrogen receptor. CONCLUSIONS: Our findings provide support for the hypothesis that endocrine active environmental compounds may contribute to the development of hypospadias. Additionally, regulation of these genes may have a role in formation of the urethra.  相似文献   
102.
广东地区223例皮肌炎与其并发症的临床分析   总被引:1,自引:0,他引:1  
目的:探讨广东地区皮肌炎与其各种并发症的关系及特点。方法:收集近20年来广东各地在中山大学孙逸仙纪念医院住院治疗的223例皮肌炎患者资料相关数据输入计算机,用数据库软件Microsoft Visual FoxPro version 5.0进行统计处理。结果:223例患者中并发心电图异常者80/178例(44.9%),肺部病变44例(19.7%),食道功能异常44例(19.7%),恶性肿瘤26例(11.7%),糖尿病13例(5.8%),与系统性红斑狼疮重叠8例(3.6%),高血压及血管炎各6例(2.7%),类风湿性关节炎4例(1.8%),红皮病3例(1.3%),肾功能衰竭1例。结论:广东地区皮肌炎患者常见的并发症是糖尿病、系统性红斑狼疮;恶性肿瘤发生率比北京地区高,以鼻咽癌为主,年龄偏低。间质性肺炎发生率相对较低;心电图异常及食道功能异常两地相近。  相似文献   
103.
104.
105.
In 22 dogs in which erection was induced by cavernous nerve stimulation, we analyzed the intracavernous pressure changes during detumescence without and with acute clamping of the aorta or electrostimulation of the lumbar sympathetic chains. Additionally, the degree of venous outflow obstruction was assessed by saline perfusion of the cavernous body during aortic occlusion. Detumescence had three distinct phases: an initial phase exhibiting a small pressure increase; a second phase showing a slow pressure decrease; and a third phase in which a fast decrease occurred. The first phase was abolished by aortic clamping, whereas the other phases were not significantly affected. Sympathetic stimulation abolished or prevented the second phase. Perfusion of the cavernous body during the second phase resulted in a pressure rise to off-scale values; however, when initiated during the terminal phase or in the nonstimulated penis, the pressure increase was slight. Our study indicates that the arterial flow rate influences the duration of the first phase of detumescence and that venous drainage is completely restored in the third phase. Furthermore, sympathetic stimulation causes an almost immediate full restoration of venous drainage, as cavernous perfusion initiated with an intracavernous pressure about twice as high as without sympathetic stimulation failed to increase pressure to off-scale values.  相似文献   
106.
Annals of Nuclear Medicine - Currently, neck ultrasound is the preferred preoperative imaging in patients with secondary/tertiary hyperparathyroidism, and the use of Tc-99m sestamibi scan is...  相似文献   
107.
108.

Background

Cavernous nerve (CN) injury during radical prostatectomy (RP) causes CN degeneration and secondary penile fibrosis and smooth muscle cell (SMC) apoptosis. Pentoxifylline (PTX) is a phosphodiesterase inhibitor that further inhibits multiple cytokine pathways involved in nerve degeneration, apoptosis, and fibrosis.

Objectives

To evaluate whether PTX enhances erectile function in a rat model of CN injury.

Design, Setting and Interventions

Forty male Sprague-Dawley rats underwent CN crush injury and were randomized to oral gavage feeding of phosphate-buffered saline (vehicle) or PTX 25, PTX 50, or PTX 100 mg/kg per day. Ten animals underwent sham surgery and received vehicle treatment. Treatment continued for 28 d, followed by a wash-out period of 72 h. An additional eight rats underwent resection of the major pelvic ganglion (MPG) for tissue culture and examination of direct effects of PTX on neurite sprouting.

Measurements

Intracavernous pressure recording on CN electrostimulation, immunohistologic examination of the penis and the CN distal to the injury site, and length of neurite sprouts in MPG culture.

Results

Daily oral gavage feeding of PTX resulted in significant improvement of erectile function compared to vehicle treatment in all treated groups. After treatment with PTX 50 and PTX 100 mg/kg per day, the expression of neuronal nitric oxide synthase in the dorsal penile nerve was significantly higher than in vehicle-treated rats. Furthermore, PTX treatment prevented collagen deposition and SMC loss in the corpus cavernosum. In the CN, signs of Wallerian degeneration were ameliorated by PTX treatment. MPG culture in medium containing PTX resulted in a significant increase of neurite length.

Conclusions

PTX treatment following CN injury in rats improved erectile recovery, enhanced nerve regeneration, and preserved the corpus cavernosum microarchitecture. The clinical availability of this compound merits application in penile rehabilitation studies following RP in the near future.  相似文献   
109.
The IGF family plays an important role in implantation and placental physiology. IGF-II is abundantly expressed by placental trophoblasts, and IGF binding protein (IGFBP)-4, a potent inhibitor of IGF actions, is the second most abundant IGFBP in the placental bed, expressed exclusively by the maternal decidua. Proteolysis of IGFBP-4 results in decreased affinity for IGF peptides, thereby enhancing IGF actions. In the current study, we have identified the IGFBP-4 protease and its inhibitor in human trophoblast and decidualized endometrial stromal cell cultures, and we have investigated their regulation in an effort to understand control of IGF-II bioavailability at the placental-decidual interface in human implantation. IGFBP-4 protease activity was detected in conditioned media (CM) from human trophoblasts and decidualized endometrial stromal cells using (125)I-IGFBP-4 substrate. Identification of the IGFBP-4 protease as pregnancy-associated plasma protein-A (PAPP-A) was confirmed by specific immunoinhibition and immunodepletion of the IGFBP-4 protease activity with specific PAPP-A antibodies. The IGFBP-4 protease activity was IGF-II-dependent in trophoblast CM. In decidualized stromal CM, PAPP-A/IGFBP-4 protease activity was also IGF-II-dependent, but was evident only when IGF-II was added in molar excess of the predominant IGFBP in decidualized stromal cell CM, IGFBP-1, supporting bioavailable IGF-II as a key cofactor of IGFBP-4 proteolysis by PAPP-A. Cultured first and second trimester human trophoblasts (n = 5) secreted PAPP-A into CM with mean +/- SEM levels of 172.4 +/- 32.8 mIU/liter.10(5) cells, determined by specific ELISA. PAPP-A in trophoblast CM (n = 3) and did not change in the presence of IGF-II (1-100 ng/ml). Cultured human endometrial stromal cells (n = 4) secreted low levels of PAPP-A (6.25 +/- 3.6 mIU/liter.10(5) cells). A physiological inhibitor of PAPP-A, the proform of eosinophil major basic protein (proMBP), was detected in trophoblast CM at levels of 1853 +/- 308 mIU/liter.10(5) cells, determined by specific ELISA, and was nearly undetectable in CM of human endometrial stromal cells. Upon in vitro decidualization of endometrial stromal cells with progesterone, PAPP-A levels in CM increased nearly 9-fold without a concomitant change in proMBP. In contrast to the experiments with trophoblasts, IGF-II and the IGF analogues, Leu(27) IGF-II, and Des (1-6) IGF-II, resulted in a dose-dependent decrease of PAPP-A levels in decidualized endometrial stromal CM by 70-90%, and a dose-dependent increase in proMBP of 14- to 41-fold. The data demonstrate conclusively that the IGF-II-dependent IGFBP-4 protease of human trophoblast and decidual origin is PAPP-A. Furthermore, the differential regulation of decidual PAPP-A and proMBP by insulin-like peptides supports a role for trophoblast-derived IGF-II as a paracrine regulator of these maternal decidual products that have the potential to regulate IGF-II bioavailability at the trophoblast-decidual interface. Overall, the data underscore potential roles for a complex family of enzyme (PAPP-A), substrate (IGFBP-4), inhibitor (proMBP), and cofactor (IGF-II) in the placental bed during human implantation.  相似文献   
110.
BACKGROUND: Leprosy is characterized by a spectrum of clinical manifestations that depend on the type of immune response against the pathogen. Patients may undergo immunological changes known as "reactional states" (reversal reaction and erythema nodosum leprosum) that result in major clinical deterioration. The goal of the present study was to assess the effect of Toll-like receptor 2 (TLR2) polymorphisms on susceptibility to and clinical presentation of leprosy. METHODS: Three polymorphisms in TLR2 (597C-->T, 1350T-->C, and a microsatellite marker) were analyzed in 431 Ethiopian patients with leprosy and 187 control subjects. The polymorphism-associated risk of developing leprosy, lepromatous (vs. tuberculoid) leprosy, and leprosy reactions was assessed by multivariate logistic regression models. RESULTS: The microsatellite and the 597C-->T polymorphisms both influenced susceptibility to reversal reaction. Although the 597T allele had a protective effect (odds ratio [OR], 0.34 [95% confidence interval {CI}, 0.17-0.68]; P= .002 under the dominant model), homozygosity for the 280-bp allelic length of the microsatellite strongly increased the risk of reversal reaction (OR, 5.83 [95% CI, 1.98-17.15]; P= .001 under the recessive model). These associations were consistent among 3 different ethnic groups. CONCLUSIONS: These data suggest a significant role for TLR-2 in the occurrence of leprosy reversal reaction and provide new insights into the immunogenetics of the disease.  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