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   691篇
  免费   26篇
耳鼻咽喉   1篇
儿科学   18篇
妇产科学   12篇
基础医学   74篇
口腔科学   19篇
临床医学   109篇
内科学   169篇
皮肤病学   76篇
神经病学   30篇
外科学   49篇
预防医学   71篇
眼科学   2篇
药学   81篇
肿瘤学   6篇
  2022年   10篇
  2021年   5篇
  2017年   7篇
  2016年   13篇
  2015年   10篇
  2014年   13篇
  2013年   30篇
  2012年   9篇
  2011年   7篇
  2010年   32篇
  2009年   37篇
  2007年   11篇
  2006年   8篇
  2004年   3篇
  2003年   5篇
  2002年   5篇
  2001年   7篇
  2000年   11篇
  1999年   13篇
  1998年   32篇
  1997年   36篇
  1996年   59篇
  1995年   47篇
  1994年   21篇
  1993年   25篇
  1992年   24篇
  1991年   15篇
  1990年   18篇
  1989年   14篇
  1988年   18篇
  1987年   10篇
  1986年   10篇
  1985年   9篇
  1984年   11篇
  1983年   7篇
  1982年   15篇
  1981年   17篇
  1980年   6篇
  1979年   9篇
  1978年   6篇
  1976年   5篇
  1975年   3篇
  1974年   3篇
  1971年   7篇
  1969年   5篇
  1958年   4篇
  1957年   9篇
  1956年   5篇
  1955年   4篇
  1954年   4篇
排序方式: 共有717条查询结果,搜索用时 15 毫秒
81.
BACKGROUND: Perineural invasion (PNI) in cutaneous squamous cell carcinoma (CSCC) may portend a poor prognosis for patients. p75NGFR (nerve growth factor receptor) is part of a membrane receptor complex that binds nerve growth factor. Its use for detecting PNI in CSCC in comparison with S-100 immunohistochemical staining has not been explored. OBJECTIVE : To determine whether detection of PNI may be improved by staining with p75NGFR compared with hematoxylin and eosin (H&E) and S-100. METHODS: Thirty-four cases of CSCC were retrospectively evaluated for the presence of PNI using standard H&E, as well as S-100 and p75NGFR immunohistochemical stains. Staining intensity was correlated to the presence or absence of PNI and tumor differentiation. RESULTS: The results showed a positive correlation between staining intensity and the presence of PNI detected by p75NGFR (p=.04). Using p75NGFR allowed for the detection of seven cases of PNI not detected by H&E alone. Five of these cases were detected by S-100, with two cases seen by p75NGFR only. Six cases of PNI were detected using S-100 not seen on H&E, with one case also not seen using p75NGFR. CONCLUSION: p75NGFR immunostaining increased detection of PNI compared with H&E. p75NGFR could serve as an alternative to S-100 in the detection of PNI or as part of an immunostaining panel for PNI detection.  相似文献   
82.
The purpose of this study was to determine if PTCA of the infarct related coronary artery (IRA) in the late phase of myocardial infarction (MI) can improve autonomic regulation of sinus rhythm and electrical stability of the myocardium measured by heart rate variability (HRV), QT, QTc, and its dispersion (QTd) and if any correlation exists among these measures. The study was performed in 25 patients (21 male, age: 50 ± 9 years, EF: 52%± 11%) in the late phase of MI (2.5 ± 1.5 months). HRV parameters were calculated automatically. QT, QTc, and QTd were measured manually from a 12-lead surface ECG (50 mm/s). All measurements were made before and 3–5 days after PTCA. Day and night parameters of HRV were sampled over two periods: 2 pm to 10 pm (day) and 10 pm to 6 am (night). Parameters of HRV measured from whole recordings were significantly higher after successful PTCA: SDRR (116 31 vs 128 ± 38 ms), SD (55 ± 17 vs 62 ± 22 ms), rMSSD (30 ± 13 vs 36 ± 14 ms) and HF (246 ± 103 vs 417 ± 224 ms2). Significant differences were found during daytime for SD, rMSSD, and HF, and during nighttime for SDRR, SDANN. QT interval duration, QT corrected to the heart rate, and QT dispersion were significantly lower after PTCA (QTd: 54 ± 15 vs 39 ± 12 ms). There was no correlation between HRV and QT values before PTCA. High correlations were found after the procedure, particularly between QTd and nighttime HRV. Conclusions: PTCA of IRA in the late phase of MI enhances sympathovagal regulation of the cardiac rhythm and the electrical stability of the heart, which may be prognostically important.  相似文献   
83.
Impairments in intestinal absorptive and digestive processes have been described in several pathophysiological situations, such as in drug-induced diabetes, obesity and hypercholesterolaemia. Furthermore, there is evidence for the occurrence of β3-adrenoceptors in multiple regions of the gastrointestinal tract, but there are no data concerning their possible involvement on jejunal and ileal digestive and absorptive functions. In this work, we have measured the modifications of selective intestinal absorption and disaccharidase activities in alloxan-induced diabetic and in diet-induced obese and hypercholesterolaemic Wistar rats. The action of a β3-adrenergic agonist (Trecadrine) with hypoglycaemic and lipolytic properties on those gastrointestinal functions has been studied. Increases in the galactose uptake by intestinal rings and in both sucrase and maltase activities were found in diabetic rats. The results obtained after Trecadrine administration to diabetic rats led to an improvement of the altered values. On the other hand, our data show a decrease in sugar absorption and in disaccharidase activities in both obese and hypercholesterolaemic groups, probably related to the low carbohydrate and high fat content of these diets. An amelioration in sucrase activity was observed after treatment with Trecadrine. Finally, Trecadrine administration to control animals significantly inhibited galactose intestinal absorption, which was independently confirmed by additional in-vitro studies. Overall, these results could be attributed not only to an improvement in the pathophysiological condition (diabetes, obesity and hypercholesterolaemia), but also to a direct effect of the β3-adrenergic agonist on the intestinal absorption processes.  相似文献   
84.
This study has evaluated the possible role played by the l-arginine-nitric oxide pathway in the vasorelaxant action of the hydroalcoholic extract from Eugenia uniflora, and fractions from the extract, in rings of rat thoracic aorta. The addition of an increasing cumulative concentration of hydroalcoholic extract from E. uniflora (1–300 μg mL?1) caused a concentration-dependent relaxation response in intact endothelium-thoracic aorta rings pre-contracted with noradrenaline (30–100 nm). The IC50 value, with its respective confidence limit, and the maximum relaxation (Rmax) were 7.02 (4.77–10.00) μg mL?1 and 83.94 ± 3.04%, respectively. The removal of the endothelium completely abolished these responses. The nitric oxide synthase inhibitors Nω-nitro-l-arginine (l-NOARG, 30 μm) and Nω-nitro-l-arginine methyl ester (l-NAME, 30 μm), inhibited the relaxation (Rmax) to ?10.43 ± 7.81% and ?3.69 ± 2.62%, respectively. In addition, l-arginine (1 mm), but not d-arginine (1 mm), completely reversed inhibition by l-NOARG. Methylene blue (30 μm), a soluble guanylate cyclase inhibitor, reduced the relaxation induced by the extract to 14.60 ± 7.40%. These data indicate that in the rat thoracic aorta the hydroalcoholic extract, and its fractions, from the leaves of E. uniflora have graded and endothelium-dependent vasorelaxant effects.  相似文献   
85.
One of the main activities of the Italian Animal Health Programme(IAHP) in the Republic of Zambia, a bilateral project betweenthe Ministry of Agriculture of the Zambian Government and theGeneral Directorate for Development Cooperation of the ItalianMinistry of Foreign Affairs, is the control of Malignant Theileriosisin Southern Province, through immersion of cattle in dip tankscontaining an acaricide. There are potentially important healthrisks to farm workers and the environment as a result of thisintervention and these are discussed. The control measures undertaken,with special reference to health education programmes, are described.  相似文献   
86.
Attitudes to and perception of health care delivery are consideredto be important factors for patient compliance in diabetes.To Investigate insulin-treated diabetic patients' use of, experienceof and attitudes to diabetes care a questionnaire was sent to561 patients, 20–50 years old, living in northern Sweden.Four hundred and eighty-eight patients (87%) participated inthe study. Data were analysed against social, medical and geographicalbackground factors. Female patients more often than men hadseen an ophthalmologist (93 versus 87%, p<0.05), a diabetesnurse specialist (74 versus 64%, p<0.05) and a chiropodist(49 versus 30%, p<0.001) at least once during the courseof their diabetes. Women also used the services of a medicalsocial worker (17 versus 10%, p-0.05) or a psychologist (14versus 8%, p<0.01) more often. More men than women were satisfiedwith the health care they had at the onset (65 versus 38%, p<0.001),but no gender difference in attitude to their present care wasfound. Diabetic patients with chronic complications comparedto those without were less satisfied both with the care theyreceived at the onset of diabetes (40 versus 61%, p<0.001)and at the time they answered the questionnaire (59 versus 72%,p<0.01). Patients in the most sparsely populated health districtwere more seldom able to be seen by the same physician (70 versus93% and 94%, p<0.001) and patient-physician continuity waspoorer over a 3 year period (48 versus 80%, p<0.001). Basedon results of this study, we conclude that use of, experienceof and attitudes to diabetes care are primarily related to genderand sickness factors. Living in sparsely populated areas probablyaffects the use and continuity of hearth care depending on themeans available. The differences demonstrated might be an argumentfor planning more individualized care for diabetic patientsin the future.  相似文献   
87.
88.
A conformational analysis of Piv-l-Pro-d-Pro-OMe was performed in the solid state using i.r. absorption and X-ray diffraction. The tertiary amide bond is in the trans conformation, whereas the tertiary peptide bond is in the cis conformation. The sequence of the, ø angles is F, F*. The preferred conformations of the pivaloylamino group, the pyrrolidine rings, and the ester moiety are also discussed.  相似文献   
89.
Electrophysiological effects of H2-receptor blockade 200 mg cimetidine IV on sinus node (SN) function and atrioventricular (AV) conduction were evaluated. Tests were performed in 21 people in basal state (group I), and in 14 people (group II) after autonomic blockade (AB) (propranolol 0.2 mg/kg, and atropine 0.04 mg/kg). We analyzed sinus cycle length (SCL), sinus node recovery time (SNRT), corrected sinus node recovery time (CSNRT), and secondary pause (SP) as the longest sinus pause after incremental overdrive pacing, sinoatrial conduction time (Strauss method) (SACT), Wenckebach point (WP), and blood pressure (BP). In group I, cimetidine prolonged SCL (717 ± 98 vs 860 ± 138 msec P < 0.001), SNRT (1161 ± 153 vs 1263 ± 163 msec P < 0.002), SP (943 ± 183 vs 1072 ± 187 msec P < 0.001), SACT (121 ± 20 msec vs 149 ± 21 msec P < 0.002), and lowered rate at which AV nodal Wenckebach point were observed (169 ± 24 vs 160 ± 26 beats/min P < 0.02). The drug did not produce significant change of the CSNRT (439 ± 121 vs 402 ± 107 msec. In group II, after AB cimetidine prolonged SCL (643 ± 79 vs 656 ± 86 msec P < 0.05), SP (686 ± 114 vs 717 ± 109 msec P < 0.05) and lowered WP (170 ± 19 vs 166 ± 19 beats/min P < 0.02) significantly. The effects of cimetidine, after AB on SNRT (894 ± 180 vs 920 ± 164 msec, CSNRT (243 ± 99 vs 255 ± 85 msec), SACT (85 ± 20 msec vs 90 ± 22 msec) were not significant. We conclude that H2-receptor blockade decreases SN automatically, prolongs SACT and AV conduction in man. The study suggests that histamine takes part in regulation of electrophysiological properties of the human heart in vivo.  相似文献   
90.
Summary. Each of three scoring systems, and oscillatory frequency, had significantly poorer correlation with fetal outcome than reporting the cardiotocograph (CTG) as either 'reactive' or 'non-reactive'. There was no significant difference in the intra- and inter-observer variability when the CTG was reported in this way.  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