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   1131篇
  免费   85篇
  国内免费   11篇
耳鼻咽喉   8篇
儿科学   39篇
妇产科学   37篇
基础医学   229篇
口腔科学   29篇
临床医学   92篇
内科学   197篇
皮肤病学   56篇
神经病学   113篇
特种医学   33篇
外科学   109篇
综合类   9篇
预防医学   98篇
眼科学   11篇
药学   91篇
中国医学   3篇
肿瘤学   73篇
  2024年   2篇
  2023年   8篇
  2022年   25篇
  2021年   45篇
  2020年   37篇
  2019年   38篇
  2018年   52篇
  2017年   36篇
  2016年   32篇
  2015年   47篇
  2014年   69篇
  2013年   71篇
  2012年   132篇
  2011年   131篇
  2010年   44篇
  2009年   35篇
  2008年   73篇
  2007年   67篇
  2006年   73篇
  2005年   50篇
  2004年   42篇
  2003年   23篇
  2002年   42篇
  2001年   7篇
  2000年   7篇
  1999年   5篇
  1998年   3篇
  1997年   9篇
  1996年   3篇
  1995年   6篇
  1994年   1篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   3篇
  1987年   1篇
排序方式: 共有1227条查询结果,搜索用时 15 毫秒
91.
PURPOSE: The aim of the study was to examine the role of Doppler ultrasonography of the portal vein in predicting esophageal variceal bleeding in patients with liver cirrhosis and portal hypertension by comparing the ultrasound data to the endoscopic findings. PATIENTS AND METHODS: 99 patients with liver cirrhosis and esophageal varices underwent color Doppler ultrasonography and esophagogastroduodenoscopy. The following portal hemodynamic parameters were analyzed: diameter and cross-sectional area, mean blood flow velocity, blood flow volume, perfusion pressure gradient, congestion index, and platelet count-to-spleen diameter ratio. Variceal characteristics, the size and the presence of red signs, were determined by endoscopic examination. RESULTS: Patients with variceal red signs had significantly higher values of portal diameter (1.538 +/- 0.246 vs. 1.243 +/- 0.167), cross-sectional area (1.286 +/- 0.448 vs. 0.945 +/- 0.256), blood flow volume (965.520 +/- 432.728 vs. 625.117 +/- 320.999) and congestion index (0.165 +/- 0.068 vs. 0.126 +/- 0.051) than patients without red signs, while the perfusion pressure gradient (0.260 +/- 0.087 vs. 0.447 +/- 0.271) and the platelet-to-spleen ratio (522.424 +/- 222.823 vs. 708.921 +/- 230.769) were lower. The same pattern of differences between the ultrasound parameters was found in patients with large varices comparing ones with red signs to the ones without them (diameter, 1.567 +/- 0.234 vs. 1.258 +/- 0.175; cross-section, 1.313 +/- 0.455 vs. 1.061 +/- 0.264; flow volume, 988.195 +/- 443.353 vs. 739.423 +/- 414.281; congestion index, 0.171 +/- 0.067 vs. 0.130 +/- 0.058; perfusion pressure gradient 0.247 +/- 0.078 vs. 0.501 +/- 0.379 and platelet-to-spleen ratio 479.930 +/- 184.302 vs. 699.094 +/- 316.171). Differences in values of ultrasonographic parameters were less obvious among groups of patients with different variceal sizes: only the diameter, cross-sectional area and blood flow volume were significantly different. The mean blood flow velocity did not depend on the variceal size or on the presence of red signs. The sensitivities and specificities of the analyzed parameters were 60-80% and 48.6-78.4%, respectively. CONCLUSIONS: Results suggest that color Doppler ultrasonography is a useful noninvasive method for evaluating the risk of esophageal variceal bleeding in patients with liver cirrhosis.  相似文献   
92.
The goal of this study was to determine the prevalence of sequence variants in the class I beta-tubulin (clone m40) gene and their occurrence in human tumors and cancer cell lines. DNA was isolated from 93 control individuals representing a wide variety of ethnicities, 49 paclitaxel-naive specimens (16 ovarian cancers, 17 non-small cell lung cancers, and 16 ovarian cancer cell lines), and 30 paclitaxel-resistant specimens (9 ovarian cancers, 9 ovarian cancer cell lines, and 12 ovarian cancer xenografts in nude mice). Denaturing high-performance liquid chromatography and direct sequence analysis detected two silent polymorphisms in exon 4, Leu217Leu (CTG/CTA) and Gly400Gly (GGC/GGT), with minor allele frequencies of 17 and 0.5%, respectively. Five nucleotide substitutions and one single-base deletion were detected in introns 1, 2, and 3 and in the 3' untranslated region. Analysis of 49 paclitaxel-naive and 30 paclitaxel-resistant specimens revealed no additional polymorphisms in the coding region. In addition, no amino acid replacements were found in chimpanzee, gorilla, and orangutan in comparison to human. Our data demonstrate a very high degree of sequence conservation in class I beta-tubulin, suggesting that all residues are important in tubulin structure and function. Individual variation in response to treatment with paclitaxel is not likely to be caused by genetic variations in the beta-tubulin drug target. Moreover, acquired mutations in class I beta-tubulin are unlikely to be a clinically relevant cause of drug resistance.  相似文献   
93.
From cats prepared for chronic pollygraphic recording of sleep patterns, records were obtained for 8 hr, after (1) intracerebroventricular (i.c.v.) injection of artificial cerebrospinal fluid (aCSF), day 1; (2) i.c.v. injection of interleukin-1 (Il-1), day 2; and (3) injection of aCSF, day 3. Three doses of Il-1 were tested. The dose of 40 nmol totally inhibited sleep, whereas the dose of 10 nmol slightly prolonged sleep. The dose of 20 nmol of Il-1 elicited sleep and a body temperature increase. Total sleep (TS) time was significantly increased, due mainly to the significant increase in non-REM (NREM) sleep as compared to control day 1. REM sleep was also increased, but this increase did not reach statistical significance. Wakefulness (W) was significantly reduced. At this time cats were febrile. On day 3, a further significant increase in TS occurred. NREM was significantly increased compared with day 1, whereas the increase in REM sleep was significant compared to both day 1 and day 2. At this time body temperature was normal. The increase in REM sleep on days 2 and 3 resulted entirely from the significant increase in the number of REM periods. The results show that Il-1 at a dose of 20 nmol has sleep-promoting effects on NREM and REM sleep concomitant with pyrogenic effects. These two responses differed in their time courses and were not correlated (correlation coefficients were all nonsignificant).  相似文献   
94.
95.
Two promising ancillary tests used in the diagnosis of mesothelioma include GLUT-1 immunohistochemical analysis and fluorescence in situ hybridization (FISH) testing for the p16 deletion. This study compared the diagnostic usefulness of p16 FISH and GLUT-1 immunohistochemical analysis in the diagnosis of mesothelial proliferations in 158 cases with a diagnosis of benign (45.4%), atypical (10.4%), or malignant/mesothelioma (44.2%). Of the 70 benign cases, none had a deletion of p16 and 5 cases (7%) were positive for GLUT-1. Of the 68 mesotheliomas, 40 (59%) had a deletion of p16 (sensitivity, 59%; specificity, 100%) and 27 (40%) were positive for GLUT-1 (sensitivity, 40%; specificity, 93%). GLUT-1 showed lower sensitivity in pleural (56% vs 70%) and peritoneal (29% vs 51%) mesotheliomas (P = .004). Our results demonstrate that p16 FISH is a more sensitive and specific test than GLUT-1 immunohistochemical analysis and can be a more reliable ancillary tool to support the diagnosis of mesothelioma.  相似文献   
96.
Oncocytic mucoepidermoid carcinoma poses diagnostic challenge because of its histologic overlap with other oncocytic salivary gland lesions, including Warthin tumor. Although the prognostic value of the t(11;19) MECT1-MAML2 fusion gene has been established in mucoepidermoid carcinoma, its diagnostic use in discriminating oncocytic mucoepidermoid carcinoma from histologic mimics is unexplored. We evaluated the translocation status in 14 cases of oncocytic mucoepidermoid carcinoma using a MAML2-11q21 break-apart probe spanning the entire chromosome region of the MAML2 gene and correlated these findings with clinicopathologic parameters including age, sex, stage, predominant growth pattern, grade, and p63 immunostaining pattern. All oncocytic mucoepidermoid carcinomas were parotid tumors with a mean patient age of 54.6 years (range, 9-85) and a female to male ratio of 5:2. Grade distribution was as follows: low grade, 9; intermediate grade, 2; and high grade, 3. The histologic patterns observed were as follows: solid, 4; cystic, 8 (of these, 5 had Warthin-like lymphoid stroma); and mixed, 2. Solid oncocytic mucoepidermoid carcinomas showed a diffuse p63 staining pattern, whereas cystic oncocytic mucoepidermoid carcinomas showed staining of the outer layer of intermediate cells ranging from a bilayer to areas of complex multilayering and plaque-like proliferation. Ten (71%) of the 14 cases showed a MAML2 rearrangement by fluorescence in situ hybridization. No correlation was seen between rearrangement status and histologic grade, growth pattern, or p63 staining pattern. However, we demonstrate that the presence of MAML2 rearrangement can be used as supportive evidence to distinguish oncocytic mucoepidermoid carcinoma from other oncocytic lesions.  相似文献   
97.
Objective Although there are extensive data on the relationship between personality and stress reactivity in adults, there is little comparable empirical research with adolescents. This study examines the simultaneous relationships between long term functioning (personality, defenses) and observed stress reactivity (affect) in adolescents. Methods High school students (N = 169; mean age 16; 73 girls) were asked to participate in two conditions of the Stress Induced Speech Task (SIST): Free Association and Stressful Situation. Immature and mature defenses, distress and restraint personality dimensions, and negative and positive affect were examined. Results Greater reported use of immature defenses was significantly associated with negative affect, whereas greater reported use of mature defenses was significantly associated with greater positive affect. Although personality style was also a significant predictor of negative affect across two out of three conditions, defenses were better overall predictors of affect than were personality dimensions. Gender was also a significant predictor of negative affect, wherein girls reported more negative affect than boys. Discussion Defenses and personality style predict affective response during a moderately stressful task. Immature defenses and, to a lesser extent, the distress personality dimension predict mobilization of negative affect, whereas mature defenses predict the reporting of positive affect. These results relate to processes central to psychotherapy: defensive responding, personality style, and affective reactivity during the recounting of stressful events.  相似文献   
98.
99.
100.
The effect of intensive long-term physical activity on phospholipid fatty acid (FA) composition has not been studied thoroughly. We determined plasma and erythrocyte phospholipid FA status of professional basketball and football players. Our results showed differences in plasma FA profile not only between sportsmen and sedentary subjects, but also between two groups of sportsmen. Plasma FA profile in basketball players showed significantly higher proportion of n-6 FA (20:3, 20:4, and 22:4) and total polyunsaturated FA (PUFA) than controls, while football players had higher palmitoleic acid (16:1) than basketball players and controls. Total PUFA and 22:4 were also higher in basketball than in football players. Erythrocyte FA profile showed no differences between football players and controls. However, basketball players had higher proportion of 18:0 than controls, higher saturated FA and lower 18:2 than two other groups, and higher 22:4 than football players. These findings suggest that long-term intensive exercise and type of sport influence FA profile.  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