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   8341篇
  免费   398篇
  国内免费   45篇
耳鼻咽喉   82篇
儿科学   153篇
妇产科学   97篇
基础医学   1081篇
口腔科学   118篇
临床医学   511篇
内科学   2222篇
皮肤病学   152篇
神经病学   692篇
特种医学   271篇
外科学   1296篇
综合类   29篇
预防医学   295篇
眼科学   106篇
药学   706篇
中国医学   40篇
肿瘤学   933篇
  2023年   35篇
  2022年   66篇
  2021年   123篇
  2020年   57篇
  2019年   82篇
  2018年   115篇
  2017年   106篇
  2016年   118篇
  2015年   119篇
  2014年   151篇
  2013年   219篇
  2012年   320篇
  2011年   356篇
  2010年   226篇
  2009年   187篇
  2008年   331篇
  2007年   416篇
  2006年   404篇
  2005年   421篇
  2004年   384篇
  2003年   405篇
  2002年   407篇
  2001年   321篇
  2000年   336篇
  1999年   342篇
  1998年   111篇
  1997年   93篇
  1996年   85篇
  1995年   94篇
  1994年   94篇
  1993年   85篇
  1992年   239篇
  1991年   247篇
  1990年   219篇
  1989年   204篇
  1988年   209篇
  1987年   174篇
  1986年   184篇
  1985年   147篇
  1984年   97篇
  1983年   80篇
  1982年   48篇
  1981年   32篇
  1980年   29篇
  1979年   78篇
  1978年   40篇
  1977年   27篇
  1976年   24篇
  1975年   14篇
  1969年   11篇
排序方式: 共有8784条查询结果,搜索用时 15 毫秒
171.
172.
The aim of the present study was to investigate the relationships between insulin resistance and soluble E-selectin, body mass index (BMI), leptin, and serum lipid profile including triglycerides in nonobese Japanese type 2 diabetic patients. A total of 97 nonobese Japanese type 2 diabetic patients aged 43 to 84 years were examined. The duration of diabetes was 11.2 +/- 0.8 years. In conjunction with BMI and fasting concentrations of plasma glucose, serum lipids (triglycerides, total cholesterol, and high-density lipoprotein cholesterol) and serum insulin, soluble E-selectin, and leptin were also measured. The low-density lipoprotein (LDL) cholesterol level was calculated using the Friedewald formula. Insulin resistance was estimated by the homeostasis model assessment. The subjects were divided into 2 groups according to the value of insulin resistance estimated by the homeostasis model assessment. Values greater than 2.5 were indicative of the insulin-resistant state, and values less than 2.5 were indicative of the insulin-sensitive state. The insulin-resistant group had significantly higher levels of E-selectin, leptin, triglycerides, total and LDL cholesterol, and diastolic blood pressure as compared with the insulin-sensitive group. There was, however, no significant difference in age, sex, diabetes duration, BMI, systolic blood pressure, HbA1c, and high-density lipoprotein cholesterol between the 2 groups. Univariate regression analysis showed that insulin resistance was positively correlated to E-selectin (r = 0.305, P = .003), BMI (r = 0.283, P = .006), leptin (r = 0.296, P = .004), HbA1c (r = 0.241, P = .018), serum triglycerides (r = 0.385, P < .001), serum total (r = 0.240, P = .019) and LDL cholesterol (r = 0.254, P = .013) levels, and systolic (r = 0.247, P = .024) and diastolic (r = 0.305, P = .006) blood pressure. Multiple regression analyses showed that insulin resistance was independently predicted by serum E-selectin (F = 18.4), serum leptin (F = 14.0) and serum triglycerides (F = 20.0) levels, which explained 45.0% of the variability of insulin resistance. From these results, it can be concluded that in conjunction with serum triglycerides and serum leptin, serum E-selectin is another important independent factor associated with insulin resistance in nonobese Japanese type 2 diabetic patients.  相似文献   
173.
Dissection of the sinus of Valsalva is an extremely rare accident during percutaneous coronary intervention (PCI), but it can lead to serious complications such as dissection of the ascending aorta. We experienced a localized dissection of the right coronary cusp without coronary artery involvement that was induced by a guiding catheter during PCI in a patient with acute myocardial infarction. The localized dissection showed pooling of the contrast medium in the acute phase, but it subsided spontaneously after 12 days without any sequelae. Manipulation of the guiding catheter should be performed with great caution not only in the coronary artery but also in the sinus of Valsalva.  相似文献   
174.
A 57-year-old man who had worked as a welder for about 40 years was admitted to our hospital. Every year he had had medical examinations in his workplace. On March 17, 1999, there was no finding of pneumoconiosis, but he had worked in a tunnel on a special arc welding project from December 20, 1999 to January 10, 2000. On admission, chest radiography revealed reticular shadows in the middle and lower lung fields. CT scans showed ground-glass opacities in both lungs. Serum iron was high (231 micrograms/dl) and serum ferritin was extremely high (2,309 ng/ml). Many iron particles were detected in the alveoli of the transbronchial biopsy specimen, and also in the sputum. A pathological diagnosis of siderosis was therefore made, and, considering the patient's occupation, the condition was termed arc welder's lung. This rapidly developing case was characterized by reticular shadows on chest radiography.  相似文献   
175.
It was reported that neuronal nitric oxide synthase (nNOS) was expressed only in gonadotrophs and folliculo-stellate cells in the anterior lobe of the pituitary gland. However, recent studies have demonstrated the occurrence of nNOS in the somatotrophs and lactotrophs. In the present study, we investigated effects of growth hormone-releasing hormone (GHRH), gonadotropin-releasing hormone (GnRH), and 17β-estradiol on nitric oxide (NO) release in cultured rat anterior pituitary cells in vitro. The NO 2 level in the incubation medium of the rat anterior pituitary cells was dependent on the cell density. Pretreatment with 10 μM 17β-estradiol resulted in an increase in medium NO 2 level. GHRH and GnRH failed to change medium NO 2 levels, but they elicited increases in medium NO 2 levels in estrogen-treated cells. The GHRH-induced increase in NO 2 level was inhibited by Nχ-nitro-l-arginine methyl ester, a NOS inhibitor. These findings suggest that GnRH and GHRH could activate nNOS in the gonadotrophs and the somatotrophs, respectively.  相似文献   
176.
Non-specific aggression to endocrine alpha and beta cells as well as exocrine pancreas has been suggested in fulminant type 1 diabetes (FT1DM), while its effect on glucagon secretion and exocrine function is unknown. Here, we report a FT1DM case with exocrine pancreatic insufficiency and enhanced glucagon response to meal ingestion.  相似文献   
177.
T cell subpopulations and interleukin 2 (IL-2) production of T cells in peripheral blood from patients with acute viral hepatitis (AVH) and chronic active hepatitis (CAH) were studied to elucidate the change of T cells functions during the exacerbation of viral hepatitis. The ratio of the number of CD4-positive cells to CD8-positive cells (CD:CD8 ratio) was increased in many patients with AVH. During exacerbation of CAH, the CD4:CD8 ratio was higher than that during remission (p less than 0.01), due to a decrease in the number of CD8-positive cells. IL2 production of T cells in AVH and CAH with bridging necrosis was higher than that of T cells in normal controls (p less than 0.01, p less than 0.05, respectively). T cells from patients with CAH produced more IL2 during exacerbation than during remission (p less than 0.01). IL2 production of T cells and the CD4:CD8 ratio (p less than 0.005, p less than 0.01). The change in T cell subpopulations in AVH and during exacerbation of CAH was found to induce an immunological condition, in which T cells easily produce IL2, which induces a proliferation of cytotoxic T cells.  相似文献   
178.
Programmable cells: interfacing natural and engineered gene networks   总被引:10,自引:0,他引:10       下载免费PDF全文
Novel cellular behaviors and characteristics can be obtained by coupling engineered gene networks to the cell's natural regulatory circuitry through appropriately designed input and output interfaces. Here, we demonstrate how an engineered genetic circuit can be used to construct cells that respond to biological signals in a predetermined and programmable fashion. We employ a modular design strategy to create Escherichia coli strains where a genetic toggle switch is interfaced with: (i) the SOS signaling pathway responding to DNA damage, and (ii) a transgenic quorum sensing signaling pathway from Vibrio fischeri. The genetic toggle switch endows these strains with binary response dynamics and an epigenetic inheritance that supports a persistent phenotypic alteration in response to transient signals. These features are exploited to engineer cells that form biofilms in response to DNA-damaging agents and cells that activate protein synthesis when the cell population reaches a critical density. Our work represents a step toward the development of "plug-and-play" genetic circuitry that can be used to create cells with programmable behaviors.  相似文献   
179.
A large-scale prospective study was conducted in 3810 Japanese elderly (> or =65 years old) patients with asthma or chronic obstructive pulmonary disease (COPD) who had been treated with sustained-release theophylline tablets (THEODUR) at a dose of 400 mg/day for 1-6 months, in principle. Among 3798 protocol-complying patients (mean age: 73.8 +/- 0.10 years, 1997 with COPD), 261 theophylline-related adverse events were observed in 179 (4.71%) patients. The 5 most frequently observed adverse events were "nausea" (40 episodes, 1.05%), "loss of appetite" (22 episodes, 0.56%), "hyperuricemia" (16 episodes, 0.42%), "palpitation" (15 episodes, 0.39%), and "increased alkaline phosphatase" (11 episodes, 0.28%). No convulsions were reported. Six patients had serious adverse events. The incidence of theophylline-related adverse events was higher in patients with hepatic disease (odds ratio: 1:1.81) and in patients with arrhythmia (odds ratio: 1:1.88). Blood drug concentration measurements in 736 patients indicated that the drug levels were < or =15 microg/ml in 641 patients (87.1%), and no correlation was noted between dose and theophylline-related adverse events. These results suggest that sustained-release theophylline can be used safely in elderly patients with asthma or COPD.  相似文献   
180.
Coronary spasm is associated with chronic low-grade inflammation.   总被引:1,自引:0,他引:1  
BACKGROUND: Coronary spasm plays an important role in the pathogenesis of ischemic heart disease and it may be associated with low-grade inflammation. METHODS AND RESULTS: Intracoronary injection of acetylcholine was done in 199 patients (99 men, 100 women, mean age, 64.5+/-11.0 years) with chest pain and normal coronary angiograms. According to the results of the provocation test, the study subjects were divided into 2 groups: the spasm group of 112 patients and the non-spasm group of 87 patients. Clinical data including high-sensitivity C-reactive protein (hs-CRP) and other coronary risk factors were compared between the 2 groups. Serum levels of hs-CRP were significantly higher in the spasm group than in the non-spasm group (median: 1.2 mg/L vs 0.5 mg/L, p<0.005). Multivariate analysis showed that hs-CRP and smoking history were independently associated with coronary spasm with an odds ratio of 2.28 (p=0.027) and 2.25 (p=0.037), respectively, with a hs-CRP value of > or = 2 mg/L as cutoff point. CONCLUSIONS: Minor elevations of the serum hs-CRP level are significantly associated with coronary spasm, suggesting that chronic low-grade inflammation may be involved in the pathogenesis of coronary spasm.  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