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   1754篇
  免费   113篇
  国内免费   14篇
耳鼻咽喉   22篇
儿科学   30篇
妇产科学   16篇
基础医学   190篇
口腔科学   12篇
临床医学   164篇
内科学   490篇
皮肤病学   36篇
神经病学   66篇
特种医学   53篇
外科学   299篇
综合类   33篇
一般理论   4篇
预防医学   90篇
眼科学   34篇
药学   126篇
中国医学   18篇
肿瘤学   198篇
  2023年   18篇
  2022年   61篇
  2021年   81篇
  2020年   58篇
  2019年   79篇
  2018年   83篇
  2017年   45篇
  2016年   51篇
  2015年   50篇
  2014年   63篇
  2013年   89篇
  2012年   138篇
  2011年   155篇
  2010年   51篇
  2009年   59篇
  2008年   95篇
  2007年   85篇
  2006年   85篇
  2005年   86篇
  2004年   63篇
  2003年   56篇
  2002年   44篇
  2001年   31篇
  2000年   35篇
  1999年   35篇
  1998年   9篇
  1997年   12篇
  1996年   5篇
  1995年   5篇
  1994年   6篇
  1993年   10篇
  1992年   20篇
  1991年   17篇
  1990年   10篇
  1989年   12篇
  1988年   10篇
  1987年   22篇
  1986年   8篇
  1985年   13篇
  1984年   7篇
  1982年   2篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1974年   3篇
  1973年   2篇
  1937年   1篇
排序方式: 共有1881条查询结果,搜索用时 15 毫秒
881.
Ambrein and epicoprostanol were evaluated for their antioxidant potential in vitro by chemiluminescence (CL), as well as in vivo using lipid peroxides and glutathione levels as indicators in liver tissue of rats treated with adriamycin (doxorubicin) a well known free radicals producing drug. In the in vitro test, the inhibition in CL by ambrein was dose dependent. Both the high concentrations of ambrein (20-40 microg/ml) inhibited CL response significantly (P<0.05 and P<0.01, respectively) when compared to control. Similarly two low concentrations (5-20 microg/ml) of epicoprostanol inhibited CL significantly (P<0.001 and P<0.01, respectively) in comparison of DMSO control. The high concentration (40 microg/ml) of epicoprostanol behaved exceptionally and caused an increase in CL response that was more than control and significantly (P<0.001) higher than both the low concentrations. In the in vivo studies adriamycin treatment significantly (P<0.05) increased malondialdehyde (MDA) and decreased non-protein sulfhydryl (NP-SH) contents in the liver tissue of mice after 5 days treatment. Ambrein (25 and 50 mg/kg) treatment as a solo therapy at both the dose levels significantly (P<0.001) decreased MDA contents in the liver tissue. On the other hand, in the combined treatment the high dose effectively prevented any rise in MDA contents and it remained around the levels of ambrein alone. In the same experiment, adriamycin declined NP-SH contents significantly (P<0.001). Ambrein alone at both the dose levels caused a decline (P<0.01) in NP-SH contents when compared to adriamycin group. But in the combined treatment this decline in NP-SH was significantly (P<0.05) different from adriamycin alone. In the experiments dealing with epicoprostanol, adriamycin treatment increased MDA contents significantly (P<0.05) that declined significantly (P<0.001) with epicoprostanol (10- or 20mg/kg) treatment. In the same experiment co-treatment with adriamycin prevented any rise in MDA contents significantly (P<0.001) as it was observed in adriamycin alone group. Although, this treatment failed to prevent any decline in NP-SH contents either alone or in combination with adriamycin. Epicoprostanol itself had the comparative declining effect on the contents of NP-SH as seen in adriamycin group. From the results of our experiments it seems that ambrein at all concentrations behaves like antioxidant in in vitro studies but the same time it decreased NP-SH contents in vivo accompanied by a decline in MDA contents. Whereas, epicoprostanol at two low concentrations had a decline in CL indicating a possible antioxidant potential but the high concentration increased CL showing a tendency towards oxidant prospective. However, in animal studies it has shown a clear protection against adriamycin induced free radical damage.  相似文献   
882.
Background. This cross-sectional study was carried out to assess the perceptions and level of knowledge of a Pakistani urban population regarding presentations, risk factors, and screening of cancers. Methods. From 4 tertiary care hospitals, 439 subjects were recruited through convenient sampling method and interviewed using a standard questionnaire. Results. More than 90% of subjects demonstrated poor knowledge. Good knowledge was associated with female gender, being married, higher socioeconomic status, and level of education. Conclusions. Our sample demonstrates an inadequate knowledge regarding the presentations, risk factors, and screening of cancers. Efforts aiming to correct these deficiencies might result in a successful and cost-effective model for primary and secondary prevention of major cancers in Pakistan.  相似文献   
883.
Age may have a different contribution to normal lung function values in those aged less than 25 years, as compared to older individuals. We report regression equations predicting ventilatory parameters in this age group, as none have been reported from Pakistan. The study was conducted on students of King Edward Medical College Lahore, Pakistan. Participants had never smoked and reported no respiratory symptoms. In addition to anthropometric data, forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF) and forced expiratory flow at 50% of FVC (FEF50) were measured. Equations predicting normal values of these parameters were derived using SPSS (Chicago, Illinois, U.S.A.) P < or = 0.05 was treated as statistically significant. Of the students, 519 took part in the study. All four parameters correlated significantly (P < 0.001) and positively with height. FEF50 had a negative correlation with age in both sexes (P < 0.05). The correlation of other parameters with age was variable and not statistically significant. On multiple regression, height featured as an independent predictor in equations for all parameters. The contribution of age as an independent predictor of ventilatory function was, once again, variable. Independent variables were retained in the raw form as their transformation did not improve the goodness of fit of the derived equations. Only height and age emerged as independent predictors of ventilatory function. Values derived from the equations presented in this study were less than those for height and age matched white Caucasians. Such differences were greater than the 'Asian correction factors'.  相似文献   
884.
Spinal cord stimulation (SCS) has traditionally been applied to the treatment of neuropathic pain with good to excellent outcomes. Visceral pain syndromes can be just as debilitating and disabling as somatic and neuropathic pain, however, there seems to be a general lack of consensus on appropriate treatment strategies for these disorders. We present here several case studies to demonstrate the viscerotomal distribution of abdominal visceral pain pathways and the application of traditional SCS techniques for its management. Nine patients, experiencing abdominal visceral pain due to various conditions including chronic nonalcoholic pancreatitis, post‐traumatic splenectomy, and generalized abdominal pain secondary to laparotomies, were treated with SCS. Efficacy of treatment was evaluated using the Visual Analog Scale (VAS) for pain intensity and a reduction, if any, in opioid intake. There was an overall mean reduction of 4.9 points in the VAS score for pain intensity and a substantial (> 50%) decrease in narcotic use. All patients were followed for more than one year with excellent outcomes and minimal complications. We conclude, based on these case reports, that SCS might be an effective, nondestructive, and reversible treatment modality for abdominal visceral pain disorders.  相似文献   
885.
Hamid Kamal Khan     
  相似文献   
886.
Pharmacological stress agents for evaluation of ischemic heart disease.   总被引:1,自引:0,他引:1  
Ischemic heart disease is the leading cause of death in the developed countries for those older than 65 years of age. In patients suspected to have coronary artery disease a stress test should be performed to identify the vulnerability of the myocardium to ischemia. As a rule of thumb, the evaluation of coronary artery disease is best done by exercise stress test. In patients who are not able to exercise adequately, pharmacological stress agents are used. The commonly used agents are the coronary vasodilators, adenosine and dipyridamole and the catecholamines, dobutamine and arbutamine. These agents are combined with imaging techniques to increase the sensitivity and specificity of the test. These agents have been widely used and have an excellent safety profile. Another advantage in using pharmacological stress agents is that they do not affect the image quality, especially with echocardiography and magnetic resonance imaging. Ongoing developments hold promise for safer and more reliable pharmacological stress agents in the future.  相似文献   
887.
888.
Labeling index (LI), apoptosis, levels of 2 pro-apoptotic cytokines tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta(TGF-beta), and the number of monocyte/macrophage cells that are the likely source of the cytokines were simultaneously measured in plastic-embedded bone marrow (BM) biopsy sections of 145 patients with myelodysplastic syndromes (MDS). TNF-alpha was correlated with TGF-beta (P = .001) and with monocyte/macrophage cells (P = .003). Patients with excess blasts in their marrows had a higher TGF-beta level (P = .01) and monocyte/macrophage number (P = .05). In a linear regression model,TGF-beta emerged as the most significant biological difference between patients who have excess of blasts and those who do not (P = .01). We conclude that in addition to TNF-alpha, TGF-beta also plays a significant role in the initiation and pathogenesis of MDS, and that a more precise definition of its role will likely identify better preventive and therapeutic strategies.  相似文献   
889.
The Asian Pacific Association for the Study of the Liver (APASL) set up a Working Party on Portal Hypertension in 2002, with a mandate to develop consensus guidelines on various clinical aspects of portal hypertension relevant to disease patterns and clinical practice in the Asia-Pacific region. Variceal bleeding is a consequence of portal hypertension, which, in turn, is the major complication of liver cirrhosis. Primary prophylaxis to prevent the first bleed from varices is one of the most important strategies for reducing the mortality in cirrhotic patients. Experts predominantly from the Asia-Pacific region were requested to identify the different aspects of primary prophylaxis and develop the consensus guidelines. The APASL Working Party on Portal Hypertension evaluated the various therapies that have been used for the prevention of first variceal bleeding. A 2-day meeting was held on January 12 and 13, 2007, at New Delhi, India, to discuss and finalize the consensus statements. Only those statements that were unanimously approved by the experts were accepted. These statements were circulated to all the experts and were subsequently presented at the annual conference of the APASL at Kyoto, Japan, in March 2007.  相似文献   
890.
Rosuvastatin, a new statin, has been shown to possess a number of advantageous pharmacological properties, including enhanced HMG‐CoA reductase binding characteristics, relative hydrophilicity, and selective uptake into/activity in hepatic cells. Cytochrome P450 (CYP) metabolism of rosuvastatin appears to be minimal and is principally mediated by the 2C9 enzyme, with little involvement of 3A4; this finding is consistent with the absence of clinically significant pharmacokinetic drug‐drug interactions between rosuvastatin and other drugs known to inhibit CYP enzymes. Dose‐ranging studies in hypercholesterolemic patients demonstrated dose‐dependent effects in reducing low‐density lipoprotein cholesterol (LDL‐C) (up to 63%), total cholesterol, and apolipoprotein (apo) B across a 1‐ to 40‐mg dose range and a significant 8.4% additional reduction in LDL‐C, compared with atorvastatin, across the dose ranges of the two agents. Rosuvastatin has also been shown to be highly effective in reducing LDL‐C, increasing high‐density lipo‐protein cholesterol (HDL‐C), and producing favorable modifications of other elements of the atherogenic lipid profile in a wide range of dyslipidemic patients. In patients with mild to moderate hypercholesterolemia, rosuvastatin has been shown to produce large decreases in LDL‐C at starting doses, thus reducing the need for subsequent dose titration, and to allow greater percentages of patients to attain lipid goals, compared with available statins. The substantial LDL‐C reductions and improvements in other lipid measures with rosuvastatin treatment should facilitate achievement of lipid goals and reduce the requirement for combination therapy in patients with severe hypercholesterolemia. In addition, rosuvastatin's effects in reducing triglycerides, triglyceride‐containing lipoproteins, non‐HDL‐C, and LDL‐C and increasing HDL‐C in patients with mixed dyslipidemia or elevated triglycerides should be of considerable value in enabling achievement of LDL‐C and non‐HDL‐C goals in the numerous patients with combined dyslipidemias or metabolic syndrome who require lipid‐lowering therapy. Rosuvastatin is well tolerated alone, and in combination with fenofibrate, extended‐release niacin, and cholestyramine, and has a safety profile similar to that of currently marketed statins. A large, long‐term clinical trials program is under way to investigate the effects of rosuvastatin on atherosclerosis and cardiovascular morbidity and mortality.  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