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   661篇
  免费   30篇
  国内免费   2篇
耳鼻咽喉   8篇
儿科学   5篇
妇产科学   8篇
基础医学   81篇
口腔科学   22篇
临床医学   55篇
内科学   217篇
皮肤病学   21篇
神经病学   63篇
特种医学   15篇
外科学   78篇
预防医学   41篇
眼科学   2篇
药学   26篇
肿瘤学   51篇
  2024年   2篇
  2023年   1篇
  2022年   11篇
  2021年   24篇
  2020年   9篇
  2019年   21篇
  2018年   16篇
  2017年   6篇
  2016年   12篇
  2015年   23篇
  2014年   20篇
  2013年   44篇
  2012年   46篇
  2011年   45篇
  2010年   30篇
  2009年   29篇
  2008年   33篇
  2007年   35篇
  2006年   52篇
  2005年   55篇
  2004年   49篇
  2003年   38篇
  2002年   25篇
  2001年   5篇
  2000年   6篇
  1999年   3篇
  1998年   5篇
  1997年   8篇
  1996年   11篇
  1995年   6篇
  1994年   4篇
  1993年   2篇
  1992年   5篇
  1991年   5篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1986年   2篇
  1985年   1篇
  1983年   1篇
排序方式: 共有693条查询结果,搜索用时 31 毫秒
41.
OBJECTIVE: To characterize a complex chromosome rearrangement (CCR) previously detected by G-banding in peripheral blood lymphocytes, as 46,X,-2,-11,-22,-X,+mar 1+mar2+mar3+mar4 in a patient with primary amenorrhea. DESIGN: Case report. SETTING: University faculty of Medicine and hospital. PATIENT(S): A 36-year-old woman with primary amenorrhea. INTERVENTION(S): Fluorescence in situ hybridization (FISH). MAIN OUTCOME MEASURE(S): Use of commercially available M-FISH probe (24 colors simultaneously) and whole chromosome painting probes for chromosomes 2, 11, 22, and X to characterize the CCR. RESULT(S): The use of conventional and multiple FISH allowed the redefinition of the CCR, showing a cryptic insertion of chromosome 11 in marker 3 previously suspected by M-FISH. The combination of G-banding and FISH data revealed that four chromosomes and seven breakpoints, including 2q21, 2q31, 11q22.1, 11q22.3, 22q13.3, Xp11.21, and Xq24, were implicated in this CCR. CONCLUSION(S): This report confirms the importance of a combination of G-banding and FISH (M-FISH and conventional FISH) techniques to characterize the de novo CCR. These techniques also were useful in defining two possible critical chromosome regions, Xp11.21 and Xq24, in which genes of potential interest for a primary amenorrhea could be located.  相似文献   
42.
BACKGROUND: Preservation injury is a major cause of primary graft dysfunction in liver transplantation (LT). Oxidative damage is considered to be the first event leading to graft damage. Xanthine oxidoreductase (XOR) and neutrophil activation, two sources of reactive oxygen species, could play a role in the development of graft dysfunction. METHODS: We determined activities of XOR forms, polymorphonuclear elastase (PMN-E), aminotransferases, and hyaluronic acid in plasma of 20 patients undergoing LT. Samples were taken from the radial artery (RA) before the anhepatic phase; from the portal vein (PV) before reperfusion; from graft caval effluent (CE) at reperfusion; and from RA, PV, and the hepatic vein (HV) 10 and 90 min postreperfusion. RESULTS: The graft, but not recipient bowel, released XOR into blood (XOR in CE, median, 61.2 mU/g protein [range, 1.9-160.4 vs. undetectable in PV before reperfusion). Circulating XOR was transformed from dehydrogenase to reversible oxidase (XOrev) (XOrev-to-XOR ratio, 48.1% in CE and 65.1% in HV 90 min postreperfusion). Neutrophil activation was detected in the recipients before reperfusion, and in liver at early post-reperfusion (median PMN-E was 0.85 microg/g protein [range, 0.01-1.58] in RA before the anhepatic phase; 2.22 microg/g protein [range, 0.20-5.88] in PV prereperfu-sion; and 3.60 microg/g protein [range, 0.48-6.78] in HV 10 min postreperfusion). XOR, but none of the other markers, was higher in the CE of patients with moderate primary graft dysfunction than in those with slight primary graft dysfunction. CONCLUSIONS: XOR release and neutrophil activation are produced during LT, and they are potentially injurious mechanisms associated with this therapy.  相似文献   
43.
Elevated levels of matrix metalloproteinase-9 (MMP-9) associates with predictors of multiple sclerosis (MS) activity. We analysed serum levels and mRNA expression of MMP-9 and its inhibitor TIMP-1 in peripheral mononuclear cells of 14 MS patients after autologous hematopoietic stem cell transplantation (AHSCT). All but 2 patients stabilized after AHSCT. A significant decrease of MMP-9 levels was seen up to 36 months after AHSCT. TIMP-1 levels did not change. MMP-9 mRNA levels correlated with the CD4+ T cell count (p<0.0001). The significant and persistent change in MMP-9 activity after AHSCT may be caused in part by the effect of AHSCT in the CD4+ T cell count.  相似文献   
44.
Immunostaining of adenosine receptors in the hippocampus and cerebral cortex from necropsies of Alzheimer disease (AD) patients shows that there is a change in the pattern of expression and a redistribution of receptors in these brain areas when compared with samples from controls. Adenosine A1 receptor (A1R) immunoreactivity was found in degenerating neurons with neurofibrillary tangles and in dystrophic neurites of senile plaques. A high degree of colocalization for A1R and betaA4 amyloid in senile plaques and for A1R and tau in neurons with tau deposition, but without tangles, was seen. Additionally, adenosine A2A receptors, located mainly in striatal neurons in controls, appeared in glial cells in the hippocampus and cerebral cortex of patients. On comparing similar samples from controls and patients, no significant change was evident for metabotropic glutamate receptors. In the human neuroblastoma SH-SY5Y cell line, agonists for A1R led to a dose-dependent increase in the production of soluble forms of amyloid precursor protein in a process mediated by PKC. A1R agonist induced p21 Ras activation and ERK1/2 phosphorylation. Furthermore, activation of A1R led to and ERK-dependent increase of tau phosphorylation and translocation towards the cytoskeleton. These results indicate that adenosine receptors are potential targets for AD.  相似文献   
45.
BACKGROUND: Human immuno-deficiency virus (HIV) infection is one of the leading public health problems in our country. Preventive education has shown itself to be a useful tool for curtailing this disease. The objective of this study is that of assessing the effectiveness of a preventive intervention at the Secondary Schools in the Baix Ebre and Montsià areas of the Tortosa Healthcare District aimed at reducing the risk of HIV transmission and furthering the knowledge of this disease. METHOD: A pre/post intervention study was conducted with no control group. A total of 19 schools, corresponding to the fourth year of Compulsory Secondary Education and first year of "Bachillerato" studies were invited to participate. The activity consisted of a workshop 60-90 minutes in length, in conjunction with educational material. A questionnaire was used as the gauging tool. RESULTS: Twelve schools agreed to participate, a total of 896 answers having been gotten for the pre-test and 805 answers for the post-test. A statistically significant increase was found for 52% (10/19) of the items regarding the correct answers on the post-test. A statistically significant improvements was found in four of the five items (80%) related to attitudes, and in five of the eight (62.5%) items related to overall knowledge of this infection following the intervention. A statistically significant improvement regarding prevention-related knowledge was found solely in one of the six items (16.6%). CONCLUSIONS: Preventive activities in the form of participational workshops are a good way of furthering the knowledge and improving the attitudes regarding HIV/AIDS of the participating teenagers. As no curative treatment exists for this disease, prevention from the educational realm is of importance for curtailing increased HIV transmission.  相似文献   
46.
BACKGROUND AND STUDY AIMS: Disinfection and surveillance of it are important for ensuring safety in gastrointestinal endoscopy. The aim of this survey was to assess the current status of disinfection in gastrointestinal endoscopy units in Spain. MATERIALS AND METHODS: An anonymous questionnaire on cleaning and disinfection methods was sent to gastrointestinal endoscopy units at 244 public hospitals in Spain. A minimum standard of disinfection (MSD) was defined to evaluate the appropriateness of disinfection practices. RESULTS: A total of 144 centers responded (58 %). All units perform manual washing of endoscopes before disinfection. Automatic washers are available in only 23 % of the centers. Selective cleaning of internal channels is systematically performed in 85 % of the centers. Glutaraldehyde-based disinfectants are the most commonly employed (84 % of units). The time of exposure to the disinfectant is at least 10 min in 97 % of units, but 20 min or more in only 36 % of them. Endoscopic accessories are sterilized in 57 % of centers. The MSD was complied with by 79 % of the units evaluated. Compliance with the MSD was significantly lower in small units (P = 0.0005) performing small numbers of examinations per month. Quality control tests on the efficacy of disinfection methods are conducted at 66 % of the centers. Specialized personnel record disinfection procedures in 85 % of the centers and supervise them in 55 % of the centers. Half of the units have inadequate equipment and facilities. CONCLUSIONS: This survey suggests that cleaning and disinfection practices in gastrointestinal endoscopy units in Spain have improved in recent years, and that there is a good compliance with standard guidelines. Most units should improve their equipment and facilities in order to provide better comfort and safety for patients and staff.  相似文献   
47.
48.
49.
OBJECTIVE: Unsedated gastroscopy is unpleasant for some patients. The identification of factors related to tolerance would permit the selection of patients for sedation. The aim of the present study was to identify these factors. METHODS: Five hundred and nine patients underwent diagnostic gastroscopy after the administration of topical pharyngeal anaesthesia, without sedation. Patients were grouped as to whether they had undergone prior examinations or not. Tolerance was assessed with a visual analogue scale and a questionnaire. RESULTS: Two hundred and seventy-three (54%) patients underwent gastroscopy for the first time, and 236 (46%) patients had prior experience. Patient tolerance was poor in 84 of 273 (31%) patients undergoing gastroscopy for the first time, and in 61 of 236 (26%) patients with prior experience. Logistic regression analysis identified the following variables related to poor tolerance: (a) in patients undergoing gastroscopy for the first time: presence of gag reflex (odds ratio (OR) = 3.42, 95% confidence interval (CI) 1.90-6.17), apprehension (OR = 2.57, CI 1.33-4.95), young age (OR = 0.95, CI 0.93-0.98) and high level of anxiety (OR = 1.91, CI 0.96-3.89); (b) in patients with prior experience: apprehension (OR = 4.21, CI 1.93-9.20), poor tolerance of prior examinations (OR = 4.92, CI 1.93-12.5) and female (OR = 2.23, CI 1.09-4.57). CONCLUSIONS: The above-mentioned factors are predictive of poor tolerance, and may enable the identification of those patients who might benefit more from sedation for gastroscopy.  相似文献   
50.

Background

A new, simple and accurate stability-indicating reverse phase high performance liquid chromatography method was developed and validated during the early stage of drug development of an oral lyophilizate dosage form of cetirizine dihydrochloride.

Methods

For RP-HPLC analysis it was used an Eclipse XDB C8 column 150 mm × 4.6 mm, 5 μm (Agilent columns, Barcelona, Spain) as the stationary phase with a mobile phase consisted of a mixture of 0.2 M K2HPO4 pH 7.00 and acetonitrile (65:35, v/v) at a flow rate of 1 mL min −1. Detection was performed at 230 nm using diode array detector. The method was validated in accordance with ICH guidelines with respect to linearity, accuracy, precision, specificity, limit of detection and quantification.

Results

The method results in excellent separation between the drug substance and its stress-induced degradation products. The peak purity factor is >950 for the drug substance after all types of stress, which confirms the complete separation of the drug substance peak from its stress induced degradation products.Regression analysis showed r2 > 0.999 for cetirizine dihydrochloride in the concentration range of 650 μg mL −1 to 350 μg mL−1 for drug substance assay and a r2 > 0.999 in the concentration range of 0.25 μg mL−1 to 5 μg mL−1 for degradation products. The method presents a limit of detection of 0.056 μg mL −1 and a limit of quantification of 0.25 μg mL−1. The obtained results for precision and accuracy for drug substance and degradation products are within the specifications established for the validation of the method.

Conclusions

The proposed stability-indicating method developed in the early phase of drug development proved to be a simple, sensitive, accurate, precise, reproducible and therefore useful for the following stages of the cetirizine dihydrochloride oral lyophilizate dosage form development.  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