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   43759篇
  免费   1952篇
  国内免费   376篇
耳鼻咽喉   443篇
儿科学   954篇
妇产科学   488篇
基础医学   5813篇
口腔科学   727篇
临床医学   2620篇
内科学   11323篇
皮肤病学   1020篇
神经病学   3254篇
特种医学   1773篇
外科学   7564篇
综合类   176篇
一般理论   6篇
预防医学   1120篇
眼科学   1001篇
药学   2716篇
中国医学   170篇
肿瘤学   4919篇
  2023年   243篇
  2022年   496篇
  2021年   883篇
  2020年   469篇
  2019年   654篇
  2018年   912篇
  2017年   691篇
  2016年   884篇
  2015年   966篇
  2014年   1243篇
  2013年   1583篇
  2012年   2550篇
  2011年   2847篇
  2010年   1614篇
  2009年   1485篇
  2008年   2682篇
  2007年   2905篇
  2006年   2929篇
  2005年   2939篇
  2004年   3051篇
  2003年   3097篇
  2002年   3066篇
  2001年   461篇
  2000年   379篇
  1999年   529篇
  1998年   758篇
  1997年   640篇
  1996年   599篇
  1995年   501篇
  1994年   451篇
  1993年   487篇
  1992年   298篇
  1991年   288篇
  1990年   232篇
  1989年   217篇
  1988年   227篇
  1987年   172篇
  1986年   140篇
  1985年   144篇
  1984年   155篇
  1983年   119篇
  1982年   122篇
  1981年   151篇
  1980年   127篇
  1979年   80篇
  1978年   100篇
  1977年   76篇
  1976年   63篇
  1975年   50篇
  1974年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Patients with immune thrombocytopenia have an increased percentage of microthrombocytes/platelet fragments and megathrombocytes. It has been suggested that increased levels of platelet associated IgG (PA-IgG) found in these patients might be related to the presence of this abnormal platelet size distribution. In this study we used flow cytometry to investigate the distribution of PA-IgG within a population of platelets and, in particular, we examined the relationship between platelet size and PA-IgG determined simultaneously on individual platelets. Platelet samples from 10 normals and 31 thrombocytopenic patients were studied. PA-IgG was estimated using immunofluorescent FITC anti-IgG antibody. Binding of FITC anti-IgG to the platelets was quantitated in the flow cytometer as relative mean fluorescence (RMF) which was calibrated against values (in fg/plt of FITC anti-IgG) obtained by spectrofluorometry after solubilization of the platelets. A high correlation (r = 0.89) was found between flow cytometric RMF value and spectrofluorometric FITC anti-IgG values. The flow cytometric studies showed that platelet samples with abnormally elevated levels of FITC anti-IgG (greater than 1.7 fg/plt) not only have a higher percentage of platelets with elevated FITC anti-IgG, but that these platelets also have increased levels of FITC anti-IgG as compared to platelets from normal samples. Platelet size was measured by the amount of forward light scatter in the flow cytometer. A low but significant correlation (r = 0.33 +/- 0.12) was found between size (FALS) and fluorescent signals in samples with elevated FITC anti-IgG. The contribution of 10% of the smallest platelets by FALS and 10% of the largest platelets by FALS to the total levels of flow cytometer platelet fluorescence in these samples was only 4.4% and 19.4% respectively which was not higher than obtained with samples with normal levels of FITC anti-IgG. In conclusion, this study showed that increased levels of PA-IgG found among thrombocytopenic patients were not confined to any particular size class of platelets.  相似文献   
992.
993.
BACKGROUND: Neurohormonal and cytokine activation after acute myocardial infarction contribute to cardiac remodeling. This study aimed to examine the effects of tumor necrotic factor (TNF)-alpha and angiotensin II on cardiac remodeling and dysfunction after acute myocardial infarction. METHODS AND RESULTS: We performed isogenic heterotopic cardiac transplantation and simultaneous coronary ligation to produce myocardial infarction in the donor heart, and to evaluate the hearts of both donors and recipients in Lewis rats. The recipients in the ligation group showed significant body-weight loss, hyperthermia, tachycardia, hypotension and leukocytosis at day 7. A significant decrease in left ventricular fractional shortening and + dP/dt, and a significant increase in left ventricular enddiastolic dimension/body weight and left ventricular enddiastolic pressure were also observed in the recipient hearts in the ligation group at day 7. With the exception of the increased perivascular fibrosis, these recipient responses were no longer seen at day 21. TNF-alpha was significantly elevated not only in the plasma but also in the recipient hearts in the ligation group at day 7. In contrast, angiotensin II was significantly increased only in the infarct region of the donor hearts, but not in the plasma. Further, the recipients' transient left ventricular remodeling and dysfunction were completely abolished by the intravenous administration of chimeric TNF-alpha soluble receptor. CONCLUSIONS: We developed a novel heterotopic cardiac transplantation-coronary ligation model capable of inducing myocardial infarction in the absence of downstream hemodynamic effects, and allowing differential quantification of indexes of cardiac remodeling in vivo, such as the local and remote effects of angiotensin II and TNF-alpha on cardiac remodeling. Modification of activated cytokines, such as TNF-alpha induced by cardiac ischemic stress, might be a beneficial strategy for the treatment of cardiac dysfunction and subsequent cardiac remodeling after acute myocardial infarction.  相似文献   
994.
995.
996.
997.
AIM: Human beta-defensin (HBD)-1 and HBD-2 are endogenous antimicrobial peptides. Unlike HBD-1, the HBD-2 expression is augmented by Helicobacter pylori (H pylori). We sought to determine HBD-1 and HBD-2 concentrations in gastric juice during H pylori infection. METHODS: HBD-1 and HBD-2 concentrations were measured by radioimmunoassay in plasma and gastric juice of 49 H pylori-infected and 33 uninfected subjects and before and after anti-H pylori treatment in 13 patients with H pylori-associated gastritis. Interleukin (IL)-1beta and IL-8 concentrations in gastric juice were measured by enzyme-linked immunosorbent assay (ELISA). Histological grades of gastritis were determined using two biopsy specimens taken from the antrum and corpus. Reverse phase high performance liquid chromatography (RP-HPLC) was used to identify HBD-2. RESULTS: HBD-2 concentrations in gastric juice, but not in plasma, were significantly higher in H pylori-positive than -negative subjects, albeit the post-treatment levels were unchanged. Immunoreactivity for HBD-2 was exclusively identified in H pylori-infected mucosa by RP-HPLC. HBD-2 concentrations in gastric juice correlated with histological degree of neutrophil and mononuclear cell infiltration in the corpus. IL-1beta levels correlated with those of IL-8, but not HBD-2. Plasma and gastric juice HBD-1 concentrations were similar in H pylori-infected and uninfected subjects. CONCLUSION: Our results place the beta-defensins, especially HBD-2, in the front line of innate immune defence. Moreover, HBD-2 may be involved in the pathogenesis of H pylori-associated gastritis, possibly through its function as immune and inflammatory mediator.  相似文献   
998.
The objective of this study was to estimate postprandial hypertriglycemia by a newly designed oral fat-loading test. Twenty-three healthy normolipidemic volunteers were orally administered a test meal consisting of a mixture of Telmeal 2.0 and 20 g of salt-free butter after fasting for 12 h. To measure the levels of total cholesterol (T-Cho), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), remnant-like particle-cholesterol (RLP-C), lipoprotein (a) [Lp (a)], free fatty acid, apolipoproteins (Apos), plasma glucose (PG), immunoreactive insulin (IRI), and high-sensitivity C-reactive protein (hs-CRP), venous blood samples were collected before the meal and at each hour until 9 h after fat-loading. The levels of both TG and RLP-C were drastically elevated at 2 h after fat-loading and these levels remained high until 4 h (p < 0.01). A significant correlation between TG and RLP-C was also observed at 2, 3 and 4 h, and the values of the correlation coefficients (r) were 0.837, 0.838, and 0.908, respectively. In contrast, the levels of T-Cho, HDL-C, Lp (a), Apos, PG, and hs-CRP did not change. Furthermore, there were no gastrointestinal symptoms during or after the study. These results strongly suggested that this newly designed fat-loading test was very useful for evaluating postprandial hypertriglycemia, including remnant concentrations.  相似文献   
999.
AIM: The aim of this study was to evaluate the anti-atherogenic outcomes of pioglitazone, a thiazolidinedione derivative, in type 2 diabetic patients. METHODS: Eight patients with poor diabetic control were treated with 15 mg of pioglitazone for 4 months. Blood samples were collected monthly, and the levels of fasting plasma glucose (FPG), HbA1c, and lipids, such as triglycerides, total cholesterol, low-density lipoprotein-cholesterol, and high-density lipoprotein-cholesterol, were measured. Other parameters, including immunorecative insulin (IRI), remnant-like particle-cholesterol (RLP-C), adiponectin, plasminogen activator inhibitor type 1 (PAI-1), tumor necrosis factor (TNF)- alpha , leptin, brain natriuretic peptide (BNP), and high-sensitivity (hs)-C-reactive protein (CRP), were examined at the beginning and end of the study. In addition, clinically adverse side-effects were evaluated. RESULTS: Treatment with pioglitazone significantly decreased the levels of HbA1c, FPG, the homeostasis model assessment of insulin resistance (HOMA-IR) index, RLP-C, PAI-1, TNF- alpha , and hs-CRP, but not the level, IRI, lipids, or leptin. In contrast, adverse side-effects, including body weight gain, liver dysfunction and edema, were not observed during this study. CONCLUSION: These results strongly suggested that treatment with pioglitazone has a greater clinical benefit for the prevention of atherosclerosis, including coronary heart diseases, without any adverse side-effects.  相似文献   
1000.
Gallbladder involvement in patients with renal cell carcinoma (RCC) is extremely rare. We present a report of a 61-year-old man with a synchronous RCC metastasis to the gallbladder presenting as an intraluminal polypoid mass simulating primary gallbladder carcinoma. Enhanced abdominal computed tomography demonstrated a well-enhanced polypoid lesion in the gallbladder. Intraoperative rapid pathological examination of the gallbladder tumor showed clear cell-type cancerous cells. Microscopically, tumor cells of both the resected kidney and gallbladder had round uniform nuclei, clear cytoplasm, and well-defined cytoplasmic borders, forming alveolar patterns. Immunohistochemically, the tumor cells were negative for cytokeratin 7 (CK7) and carcinoembryonic antigen (CEA), which is usually positive in primary clear cell carcinoma of the gallbladder. Therefore, the final diagnosis was RCC with a synchronous gallbladder metastasis.  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