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   71993篇
  免费   4460篇
  国内免费   3093篇
耳鼻咽喉   253篇
儿科学   1215篇
妇产科学   709篇
基础医学   7107篇
口腔科学   1419篇
临床医学   4266篇
内科学   8205篇
皮肤病学   1814篇
神经病学   6704篇
特种医学   1320篇
外国民族医学   5篇
外科学   4023篇
综合类   9318篇
现状与发展   3篇
预防医学   5229篇
眼科学   596篇
药学   17967篇
  16篇
中国医学   6965篇
肿瘤学   2412篇
  2024年   249篇
  2023年   1015篇
  2022年   1735篇
  2021年   2237篇
  2020年   2119篇
  2019年   1801篇
  2018年   1720篇
  2017年   2016篇
  2016年   2186篇
  2015年   2304篇
  2014年   4144篇
  2013年   4989篇
  2012年   4085篇
  2011年   4487篇
  2010年   3390篇
  2009年   3259篇
  2008年   3408篇
  2007年   3473篇
  2006年   3043篇
  2005年   2737篇
  2004年   2410篇
  2003年   2064篇
  2002年   1721篇
  2001年   1489篇
  2000年   1327篇
  1999年   1179篇
  1998年   1112篇
  1997年   1058篇
  1996年   1015篇
  1995年   944篇
  1994年   858篇
  1993年   724篇
  1992年   718篇
  1991年   657篇
  1990年   656篇
  1989年   623篇
  1988年   573篇
  1987年   516篇
  1986年   530篇
  1985年   796篇
  1984年   735篇
  1983年   539篇
  1982年   544篇
  1981年   505篇
  1980年   467篇
  1979年   329篇
  1978年   243篇
  1977年   194篇
  1976年   177篇
  1975年   120篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
31.
32.
The best test presently available to ascertain residual viability within an infarct-related area involves the use of fluorine-18 fluorodeoxyglucose (FDG) to detect the persistence of some cellular metabolism. Rest reinjection of thallium-201 is a less accurate alternative but is easy to perform. Iodinated fatty acids, which are used with standard gamma cameras, are proposed as markers of cellular metabolism. This study was performed to assess the value of 16-iodo-3-methyl-hexadecanoic acid (MIHA) as a marker of the residual cellular metabolism by comparison with FDG in patients with a recent myocardial infarction, and to evaluate its contribution compared with the201Tl stress-redistribution-reinjection technique. Stress-redistribution-reinjection201T1 imaging, rest MIHA imaging and glucoseloaded FDG imaging were performed in 22 patients with recent myocardial infarction. Out of the 628 myocardial segments obtained from the left ventricular analysis, 400 were hypoperfused (relative uptake <0.75 of maximum uptake on stress201T1 imaging), 177 of which were severely hypoperfused (relative uptake <0.50). Receiver operating characteristic (ROC) curves for predicting metabolic myocardial viability with FDG were derived from the results in respect of (a)201T1 activity during exercise, redistribution and reinjection and (b) MIHA up-take, using the two FDG thresholds most commonly considered to define metabolic viability (0.50 and 0.60). Analysis of the 400 hypoperfused segments demonstrated that201T1 reinjection was the most accurate test in predicting the presence of myocardial viability (area under the ROI curves=0.85 and 0.86 at the 0.50 and 0.60 FDG thresholds, respectively;P<0.05 vs other tests). The global predictive values of MIHA and201T1 reinjection were, respectively, 0.87 and 0.89 at the 0.50 FDG threshold (NS), and 0.82 and 0.87 at the 0.60 FDG threshold (NS). When only the 177 severely hypoperfused segments were considered,201T1 reinjection remained the most accurate test (accuracy 0.84 at the 0.50 FDG threshold and 0.82 at the 0.60 FDG threshold), while the accuracy of MIHA decreased significantly (0.78 at the 0.50 FDG threshold and 0.73 at the 0.60 FDG threshold,P<0.05 vs201T1 reinjection). In all circumstances, MIHA was less specific than201T1 reinjection for the detection of metabolic viability. In conclusion, in patients with recent myocardial infarction, MIHA accurately detects the persistence of metabolic viability, but is not superior to201T1.  相似文献   
33.
34.
The aim of this study was to investigate markers of serotonin and immune function in suicidal patients. Cytotoxic activity of natural killer cells (NK) and CD16 lymphocytes were studied in 28 suicide attempters and 26 healthy controls, and related in patients to 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid (CSF). Patients with CSF 5-HIAA below the median had significantly lower NK cell activity than other patients. CD16 cell frequency was significantly lower in patients than in controls, and patients also tended to have lower NK cell cytotoxicity than healthy controls. There were no statistically significant correlations between 4-hydroxy-3methoxyphenyl glycol (HMPG), homovanillic acid (HVA), CSF cortisol and NK cell activity. The results support the hypothesis of compromised immune function in suicidal patients with evidence of disordered serotonin function.  相似文献   
35.
The Kasabach-Merritt syndrome is characterized by thrombocytopenia and localized coagulopathy associated with a hemangioma. Most techniques applied to eradicate the tumor or accelerate its involution (surgery, radiation therapy, embolization) are invasive and require transfusion of large amounts of blood products. In some cases, medical treatment is the only alternative. Efficacy of steroids and antifibronolytic agents has already been described, but even this approach is associated with the administration of blood products. We report two cases of infants with Kasabach-Merritt syndrome associated with cardiac and hepatic hemangiomas. At admission, both had signs of cardiac failure. They were successfully treated with prednisone and epsilon-aminocaproic acid (EACA). Blood products were not required once the diagnosis was made. These observations have important implications for the management of patients with Kasabach-Merritt syndrome because they show that even in severe cases blood transfusions can be avoided by the use of prednisone and EACA.  相似文献   
36.
We report the case of a patient with delayed methotrexate (MTX)-induced leukoencephalopathy who showed a marked improvement both in clinical and neuroimaging findings after a high-dose of the active form of folinic acid (leucovorin) treatment. The patient developed progressive affective impairment accompanied by headache, nausea and vomiting after treatment with MTX during the chemotherapy for acute lymphoblastic leukemia, and diagnosed as delayed type MTX-induced leukoencephalopathy. After an intravenous injection of high-dose folinic acid (total 1920 mg), neurological deficits and white matter changes dramatically improved in a few weeks. Although delayed MTX-induced leukoencephalopathy may cause irreversible brain damage, an early treatment with high dose leucovorin may thus facilitate the marked improvement of clinical findings and white matter abnormalities.  相似文献   
37.
Glutamate is the primary excitatory amino acid in the mammalian central nervous system. Normal excitation of glutamate receptors initiates the stimulation of phospholipases and lipases with the generation of second messengers that are necessary for normal cell function. The overstimulation of glutamate receptors can initiate a cascade of biochemical events including stimulation of membrane phospholipid turnover, excessive calcium entry, abnormal phosphorylation, and proteolysis. These events may be responsible for neuronal injury and degeneration found in Alzheimer disease, ischemia, spinal cord trauma, epilepsy, and Huntington disease.  相似文献   
38.
检测了74例正常足月妊娠妇女和56例妊娠期肝内胆汁淤积症(ICP)患血清甘胆酸(CG)的浓度,结果ICP患血CG浓度显升高(13.52±9.54mg/L),为正常孕妇(2.67±1.92mg/L)的5~10倍,根据血CG浓度将ICP患分为〈10、10~20,〉20mg/L3组,将3组胎儿出生情况与正常组相对照,结果显示血CG浓度〈10mg/L组羊水胎粪污染率及新生儿窒息率与正常组无差异,而  相似文献   
39.
As an octanoic acid 13CO2 breath test is frequently used to test gastric emptying of solid food, the purpose of the present study was to study whether oxidative breakdown of octanoic acid is affected by severe liver disease. The design of our study was twofold. First, cirrhotic patients (n = 82) of varying severity were compared with healthy controls (n = 17). Values of half-time, time point of maximal expiration and cumulative recovery of octanoic acid breath tests (OBT) were not significantly different between them. Secondly, cirrhotic patients (n = 10) were studied before placement of transjugular intrahepatic portosystemic shunt, 4-7 days later and 1-2 months later. Values of half-time, time point of maximal expiration and cumulative recovery of consecutive OBTs did not change significantly. The OBT may therefore be a suitable test in the future to detect delayed gastric emptying of solids in cirrhotic patients with reduced liver function and portal hypertension.  相似文献   
40.
BACKGROUND: Allergen extracts are unstable, heat labile or susceptible to proteases. Stability of allergen extracts is important for proper diagnosis and therapy of allergic disorders. OBJECTIVE: The present study was undertaken to determine the preservation and stabilization conditions of Imperata cylindrica (Ic) grass pollen extract. METHODS: The Ic extract was kept with 0.1 mepsilon-aminocaproic acid (EACA), 0.75 m sucrose, 5% glycerol, 0.03% human serum albumin (HSA) or 0.4% phenol for different time periods. The extracts were stored for 3, 6 and 12 months each at 4 degrees C, 4 degrees C with daily exposure to room temperature (RT) for 1 h, and RT. The quality of extracts was analysed by SDS-PAGE, Western blot, ELISA, ELISA inhibition and skin test. RESULTS: Extracts kept with EACA and sucrose retained most of the protein bands followed by glycerol as determined by SDS-PAGE and Western blot during all storage periods and conditions in comparison with standard extracts. The extracts kept with HSA, phenol and without preservative (WP) showed protein degradation below 33 kDa after 3 months storage at all conditions. However, a 67-kDa allergen was stable in these extracts. EACA extract required 75 to 120 ng of protein for 50% inhibition in IgE binding under different conditions, whereas standard extract required 70 ng for the same. ELISA also demonstrated high allergenic reactivity of EACA extract. ID test on allergy patients with EACA extract demonstrated same allergenic potency as that of standard extract. CONCLUSION: EACA is the best preservative/stabilizing agent of Ic pollen extract, followed by sucrose and glycerol. Ic extract kept with phenol, HSA and without preservative showed degradation within 3 months. EACA preserved extract is equally potent as that of standard extract up to 1 year's storage.  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