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   25958篇
  免费   1384篇
  国内免费   82篇
耳鼻咽喉   338篇
儿科学   1426篇
妇产科学   616篇
基础医学   2854篇
口腔科学   584篇
临床医学   1523篇
内科学   5537篇
皮肤病学   772篇
神经病学   1680篇
特种医学   816篇
外科学   3401篇
综合类   785篇
一般理论   15篇
预防医学   1283篇
眼科学   1381篇
药学   2360篇
中国医学   185篇
肿瘤学   1868篇
  2023年   160篇
  2022年   358篇
  2021年   932篇
  2020年   463篇
  2019年   593篇
  2018年   769篇
  2017年   520篇
  2016年   665篇
  2015年   616篇
  2014年   984篇
  2013年   1207篇
  2012年   1698篇
  2011年   1820篇
  2010年   968篇
  2009年   796篇
  2008年   1251篇
  2007年   1294篇
  2006年   1281篇
  2005年   1089篇
  2004年   995篇
  2003年   852篇
  2002年   778篇
  2001年   721篇
  2000年   723篇
  1999年   574篇
  1998年   232篇
  1997年   168篇
  1996年   151篇
  1995年   165篇
  1994年   121篇
  1993年   109篇
  1992年   393篇
  1991年   388篇
  1990年   362篇
  1989年   343篇
  1988年   293篇
  1987年   274篇
  1986年   247篇
  1985年   247篇
  1984年   177篇
  1983年   154篇
  1982年   81篇
  1981年   101篇
  1979年   166篇
  1978年   98篇
  1977年   86篇
  1975年   88篇
  1974年   104篇
  1973年   94篇
  1972年   119篇
排序方式: 共有10000条查询结果,搜索用时 227 毫秒
131.
132.
Fenfluramine, an amphetamine derivative used in the treatment of obesity, has been evaluated in vivo in the bone marrow cells of Swiss albino mice using two cytogenetic endpoints for assessing its genotoxic and clastogenic potentials. Concentrations of 0.75, 1.5, 3.0, and 5.0 mg/kg b.w. were administered orally for the study of sister chromatid exchange frequencies and chromosome aberrations (CA). SCE frequencies showed a positive dose response; 1.5 mg/kg being the minimum effective concentration. Fen caused a prolongation of cell cycle at all concentrations. Except for the minimum therapeutic dose (0.75 mg), all other doses (1.5, 3.0, and 5.0 mg) showed a significant increase in the percentage of damaged cells over that of the vehicle control. The degree of clastogenicity was directly proportional to the dosage used and inversely related with the duration of treatment. A gradual reduction of the clastogenic potential was observed after 12 and 24 hr of exposure, indicating that the maximum effect occurs at the middle or late synthetic phase of the cell cycle. This study, probably the first detailed screening of the drug for its genotoxicity, shows that Fen is moderately clastogenic and a DNA damaging agent in vivo.  相似文献   
133.
Several amino acid and peptide conjugates of 6-azacadeguomycin (6-amino-1-beta-D-ribofuranosyl-4,5-dihydro-4-oxopyrazolo[3,4-d]py rimidine- 3-carboxylic acid, 2) have been prepared in good yields, via a two-step procedure involving 1-hydroxybenzotriazole and 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide hydrochloride mediated coupling of 2 with an appropriately protected amino acid or peptide, followed by ammonolysis. Thus, condensation of 2 with L-phenylalanine methyl ester, glycine ethyl ester, and L-glutamic acid diethyl ester gave the corresponding protected linear nucleoside peptides (3, 5 and 7, respectively). Subsequent ammonolysis of 3, 5 and 7 furnished L-phenylalanine amide (4), glycine amide (6) and L-glutamic acid diamide (8) conjugates of 6-azacadeguomycin, respectively. Saponification of 7 gave the corresponding L-glutamic acid derivative 9. A similar coupling of 2 with L-phenylalaninyl-N epsilon-nitro-L-arginine methyl ester trifluoroacetate and subsequent ammonolysis (after catalytic hydrogenation) gave L-phenylalaninyl-L-arginine amide conjugate (12) of 6-azacadeguomycin. Compounds 2, 4, 6, 8, 9, and 12 were evaluated for their ability to potentiate T-cell responses to plant mitogens, in comparison with cadeguomycin (1). Compounds 4, 6, and 9 exhibited an increase in the T-cell proliferation in a dose-dependent manner.  相似文献   
134.
Consequent to the promising results reported with 99mTc(V)-DMSA for imaging certain types of soft tissue tumors, we have developed methods to prepare this radiopharmaceutical in three ways: from freshly prepared reagents, through the use of a two component kit and use of the standard renal DMSA kit by a modified recipe. The 99mTc(V)-DMSA complex has been subjected to paper electrophoretic and chromatographic procedures and also biodistribution studies. The distinctly different behaviour of this new product compared to that of the well known renal DMSA complex has been clearly established. Scintiimaging in a preliminary clinical trial in patients with medullary carcinoma of the thyroid has been encouraging.  相似文献   
135.
This article describes the immediate effect of verapamil, a calcium antagonist, on pulmonary functions in bronchial asthma. The effect of oral administration of 80 mg of verapamil or placebo was studied in a randomized double-blind manner in 30 extrinsic asthmatic subjects. No significant bronchodilator effect was observed with verapamil administration. There were no significant changes in heart rate and blood pressure after verapamil.  相似文献   
136.
We report meningioma of the floor of the anterior cranial fossa with bilateral, symmetrical intraorbital extension, describing the findings on plain films and CT.  相似文献   
137.
OBJECTIVE: To determine the impact of nutritional status on peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD) in a developing country. METHODS: 56 patients with end-stage renal disease on CAPD were randomly selected for this study. These patients were assessed for nutritional status and peritonitis episodes. Nutritional parameters were assessed by anthropometry, diet, body mass index (BMI), Nutritional Risk Index (NRI), serum albumin level, and Subjective Global Assessment (SGA). Based on SGA, patients were categorized into either group 1 (malnutrition, n = 31) or group 2 (normal nutritional status, n = 25). Peritonitis was considered the primary outcome and was compared between the two groups. RESULTS: Demographic profiles, Kt/V, creatinine clearance, and mean follow-up of the two groups were similar. Number of peritonitis episodes was significantly higher in patients with malnutrition (25/31) compared to patients with normal nutritional status (4/25) (p = 0.001). Mean peritonitis rate per patient per year was also significantly higher in patients with malnutrition (0.99 +/- 1.07) compared to patients with normal nutritional status (0.18 +/- 0.42) (p = 0.007). On univariate analysis, malnutrition based on SGA (p = 0.009), NRI (p = 0.02), serum albumin level (p = 0.005), and calorie intake (p = 0.006) was a significant predictor of peritonitis. On multivariate Cox regression analysis, only SGA (p = 0.001, odds ratio 0.08, 95% confidence interval 0.02-0.36) was found to be a significant predictor of peritonitis. On general linear model, the observed power of prediction of peritonitis was 0.96 based on SGA. On Kaplan-Meier survival analysis, peritonitis-free survival in patients with normal nutrition (42 months) was significantly higher compared to patients with malnutrition (21 months) based on SGA (log rank p = 0.003). CONCLUSION: We conclude that peritonitis rate is high in patients with malnutrition and that malnutrition indices, especially SGA, can predict the peritonitis rate in CAPD patients.  相似文献   
138.
139.
Cardiac injuries--a clinical and autopsy profile   总被引:3,自引:0,他引:3  
One hundred two patients sustaining cardiac injuries over a 4-year period were analysed to highlight the natural history of the cardiac injuries. There were 45 blunt, 36 stab, and 21 gunshot injuries. The injury involved the ventricle in 85, atrium in seven, pulmonary artery in five cases, and resulted in crush injury to the heart in the remaining five cases. Thirty-three patients (32.3%) died on the scene and 58 (56.9%) died during the transportation. Only 11 patients (10.8%) reached the hospital alive, and ten of these patients survived following thoracotomy and repair of the cardiac injury. The factors influencing the natural course of cardiac injury were analysed: 2.2% of patients with blunt cardiac trauma reached the hospital alive compared to 19.4% with stab and 14.3% with gunshot injuries; ventricular injuries had a greater prehospital mortality compared to atrial or pulmonary artery injuries; 11.3% of patients sustaining injury to right ventricle reached the hospital alive compared to 3% of those with left ventricular injuries. These data emphasize the need for rapid transport, immediate recognition, and aggressive surgical management, to make a favourable impact on the natural history of cardiac injuries.  相似文献   
140.

Background  

The purpose of this study was to characterize total homocysteine (tHcy) levels at birth in preterm and term infants and identify associations with intraventricular hemorrhage (IVH) and other neonatal outcomes such as mortality, sepsis, necrotizing enterocolitis, bronchopulmonary dysplasia, and thrombocytopenia.  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