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   7471篇
  免费   350篇
  国内免费   73篇
耳鼻咽喉   72篇
儿科学   127篇
妇产科学   158篇
基础医学   830篇
口腔科学   134篇
临床医学   463篇
内科学   1991篇
皮肤病学   154篇
神经病学   450篇
特种医学   264篇
外科学   1492篇
综合类   18篇
一般理论   1篇
预防医学   186篇
眼科学   187篇
药学   354篇
中国医学   14篇
肿瘤学   999篇
  2024年   6篇
  2023年   58篇
  2022年   100篇
  2021年   198篇
  2020年   116篇
  2019年   137篇
  2018年   211篇
  2017年   146篇
  2016年   166篇
  2015年   198篇
  2014年   249篇
  2013年   313篇
  2012年   534篇
  2011年   615篇
  2010年   344篇
  2009年   301篇
  2008年   552篇
  2007年   566篇
  2006年   500篇
  2005年   490篇
  2004年   448篇
  2003年   448篇
  2002年   387篇
  2001年   66篇
  2000年   48篇
  1999年   65篇
  1998年   101篇
  1997年   63篇
  1996年   64篇
  1995年   43篇
  1994年   55篇
  1993年   38篇
  1992年   32篇
  1991年   22篇
  1990年   17篇
  1989年   21篇
  1988年   29篇
  1987年   19篇
  1986年   10篇
  1985年   8篇
  1984年   15篇
  1983年   12篇
  1982年   14篇
  1981年   12篇
  1980年   8篇
  1978年   13篇
  1977年   10篇
  1976年   3篇
  1975年   7篇
  1974年   3篇
排序方式: 共有7894条查询结果,搜索用时 15 毫秒
141.
The cardiovascular and sympatholytic effects of combination therapy with guanabenz were examined in 26 patients (48 ± 13 years old [mean ± SD]) with stage 2 and 3 hypertension. Included in the study were patients under treatment with conventional antihypertensive drugs whose systolic and diastolic blood pressure was above 140 and 90 mmHg, respectively. Blood pressure, heart rate, and sympathetic parameters such as plasma concentration of norepinephrine and muscle sympathetic nerve activity at rest as well as during ambulatory conditions, 24-hour urinary excretion of norepinephrine, and low frequency (LF: 0.04–0.15 Hz)/high frequency (HF: 0.15–0.4 Hz) power ratio as a marker of cardiac sympathetic activity during 24 hours were examined before and after guanabenz (4–8 mg/d) combination therapy with first-line antihypertensive drugs such as diuretics. Left ventricular mass index (LVMI) was also calculated by conventional echocardiography. After 32 weeks of guanabenz combination therapy, systolic and diastolic blood pressure, heart rate, plasma and urinary excretion of norepinephrine, muscle sympathetic nerve activity, and LF/HF power ratio were significantly decreased, while neither LF nor HF power was changed. LVMI was also significantly decreased (270 ± 81 vs. 236 ± 83 g/m2, p < 0.005). These results indicate that guanabenz combination therapy inhibits sympathetic nerve activity under resting conditions as well as during ambulatory conditions and may accelerate regression of left ventricular hypertrophy in patients with moderate to severe hypertension.  相似文献   
142.
Aim: Because the procedure of balloon-occluded retrograde transvenous obliteration (B-RTO) causes extensive thrombosis of the major shunt that connects the spleen and gastric/renal venous systems, an increase in portal pressure is unavoidable. The aim of the present study was to assess the long-term outcome of B-RTO, including changes in esophageal varices. Methods: B-RTO was conducted in 22 patients with gastric varices, who were divided according to the severity of esophageal varices at baseline; there were no esophageal varices (n = 7), F(1) varices (n = 11), and F(2) varices (n = 4). The outcome measures included the development/worsening of esophageal varices after B-RTO and survival rates. Results: The cumulative bleeding-free probability for all 22 patients at 3 years after B-RTO was 100%. The overall 3-year survival was 94.4%. Seven patients who had no esophageal varices prior to B-RTO did not develop any after the procedure. Seven (63.6%) of the 11 patients with stage F(1) esophageal varices prior to B-RTO showed no changes in the varices after B-RTO, while two patients progressed to F(2) varices and two developed F(3) varices. The cumulative treatment-free probability of the esophageal varices at 24 months after B-RTO was 100% for patients without esophageal varices at baseline, 80.8% for patients with pre-existing F(1) varices, and 75% for those with pre-existing F(2) varices. Conclusion: Although the B-RTO procedure is considered useful for the treatment of gastric varices, changes in hemodynamics due to obliteration of this major shunt must be taken into account and observed closely.  相似文献   
143.
AIM: Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease (NAFLD), and progresses to the end stage of liver disease. Biochemical markers of liver fibrosis are strongly associated with the degree of histological liver fibrosis in patients with chronic liver disease. However, data are few on the usefulness of markers in NAFLD patients. The aim of this study was to identify better noninvasive predictors of hepatic fibrosis, with special focus on markers of liver fibrosis, type VI collagen 7S domain and hyaluronic acid. METHODS: One hundred and twelve patients with histologically proven NAFLD were studied. RESULTS: The histological stage of NAFLD correlated with several clinical and biochemical variables, the extent of hepatic fibrosis and the markers of liver fibrosis were relatively strong associated. The best cutoff values to detect NASH were assessed by using receiver operating characteristic analysis: type VI collagen 75 domain ≥5.0 ng/mL, hyaluronic acid ≥43 ng/mL. Both markers had a high positive predictive value: type VI collagen 7S domain, 86% and hyaluronic acid, 92%. Diagnostic accuracies of these markers were evaluated to detect severe fibrosis. Both markers showed high negative predictive values: type VI collagen 7S domain (≥5.0 ng/mL), 84% and hyaluronic acid (≥50 ng/mL), 78%, and were significantly and independently associated with the presence of NASH or severe fibrosis by logistic regression analysis. CONCLUSION: Both markers of liver fibrosis are useful in discriminating NASH from fatty liver alone or patients with severe fibrosis from patients with non-severe fibrosis.  相似文献   
144.
We present a case of esophageal carcinoma in which esophagectomy was not possible because of tuberculous fibrosing mediastinitis. A 77-year-old man was diagnosed with carcinoma of the thoracic esophagus and admitted to our hospital. Chest radiography on admission revealed no abnormality except pleural thickening of the pulmonary apices, suggesting a history of subclinical infection of tuberculous pleurisy. The patient underwent surgery with a curative intent. Thoracotomy revealed that the mediastinum had been replaced with dense fibrous tissues and was widely encased with laminar calcification. Esophagectomy was not performed because it was considered impossible to do so safely. Although diagnosis of fibrous mediastinitis was not made preoperatively, review of the preoperative computed tomographic scans revealed proliferation of mediastinal soft tissues that were associated with patchy and laminar calcifications. Tuberculous fibrosing mediastinitis is an uncommon but clinically important disease for physicians who are involved in the diagnosis and treatment of esophageal cancer.  相似文献   
145.
Objectives. The aim of this study was to clarify the prevalence and the predictive factors for undergoing total knee arthroplasty (TKA) among patients with rheumatoid arthritis (RA).

Methods. The data of 1,134 patients with RA who were enrolled in the Japanese nationwide cohort database NinJa in 2003 and consecutively followed up until 2009 were analyzed.

Results. Seventy-six patients underwent TKA during the observation period. The yearly progression of the modified Health Assessment Questionnaire or mHAQ score from 2003 to 2004, but not the yearly progression of the Disease Activity Score in 28 Joints or DAS28 or patient visual analog scale (VAS) score, was significantly higher in the patients who underwent TKA than those who did not.

Multivariate analysis showed that knee involvement in the disease, high Steinbrocker stage (III or IV), and high patient VAS score at the time of enrollment were powerful predictive factors, with hazard ratios of 4.01, 3.71, and 1.20, respectively.

According to survival analysis with TKA as an endpoint, patients with knee involvement in the disease at the time of enrollment had a significantly worse 5-year survival rate than did those without knee involvement (83.5% vs. 97.0%, respectively).

Conclusion. Several factors were elucidated as predictive factors for undergoing TKA among patients with RA.  相似文献   
146.
A 79-year-old man was referred to this department due to the presence of extrahepatic bile duct carcinoma with a tumor at the left chest wall. The lesion was suspected to be a metastasis of bile duct carcinoma to the left wall, however, computed tomography (CT) revealed no regional lymph node or liver metastases. In addition, cytological and pathological examinations did not show malignancy. At the time of admission, the white blood cell count was 21 460 cells/μL (neutrophils, 18 240 cells/μL) and this elevated to 106 040 before death. In addition, serum granulocyte colony-stimulating factor (G-CSF) was elevated. At 28 d after admission, the patient died. An autopsy showed a poorly differentiated adenocarcinoma with sarcomatous change, which had slightly invaded into the pancreas around the bile duct, and was found in the distal bile duct with multiple metastases to the chest wall, lung, kidney, adrenal body, liver, mesentery, vertebra and mediastinal and para-aortic lymph nodes, without locoregional lymph node and liver metastasis. The cancer cells showed positive immunohistochemical staining for anti-G-CSF antibody. This is believed to be the first report of an extrahepatic bile duct carcinoma that produces G-CSF. Since G-CSF-producing carcinoma and sarcomatous change of the biliary tract leads to poor prognosis, early diagnosis and treatment are needed. When infection is ruled out, the G-CSF in serum should be examined. In addition, examinations such as bonescintigraphy and chest CT should also be considered for distant metastasis.  相似文献   
147.
The mechanism responsible for cardiac depression in septic shock remains unknown. The present study examined whether nitric oxide (NO) overproduced by inducible NO synthase (iNOS) can inhibit aerobic energy metabolism and impair the myocardial function in endotoxin-treated rat hearts. Lipopolysaccharide (LPS) significantly decreased systolic blood pressure (BP) to 44% of control during the 48 h treatment. Hearts from control and LPS-treated rats were perfused in a Langendorff apparatus. After LPS injection, left ventricular (LV) developed pressure (LVDP) was significantly depressed, plasma NO2-/NO3- (NO(x)) concentration was markedly increased, and myocardial adenosine 5'-triphosphate (ATP), creatine phosphate (CrP), and the ratio of ATP/adenosine 5'-diphosphate were progressively decreased with time. Immunological examination showed a significant expression of iNOS protein in the LPS-treated myocytes. Aminoguanidine, an inhibitor of iNOS, significantly attenuated these LPS-induced functional and metabolic changes. Myocardial cyclic guanosine 3',5'-monophosphate (cGMP) content was significantly increased after LPS injection. Methylene blue, an inhibitor of soluble guanylate cyclase, blunted this increase in cGMP and significantly restored the LPS-induced contractile dysfunction 6 h after LPS injection. In addition, there was a significant negative correlation between LVDP and myocardial cGMP levels as well as a significant negative correlation between LVDP and plasma NO(x) levels. In contrast, 48 h after LPS injection, methylene blue no longer affected cardiac performance, and there was a significant positive correlation between LVDP and myocardial ATP content. Furthermore, the normalized activities (as a ratio of the citrate synthase activity) of mitochondrial NADH-CoQ reductase, succinate-CoQ reductase, and ATPase, were significantly inhibited, and the swelling or disruption of mitochondria cristae was seen in the 48 h LPS treatment. These LPS-induced functional and morphological disorders in the mitochondria were significantly improved by aminoguanidine. The findings suggest that sustained production of NO by iNOS leads to contractile dysfunction via cGMP in the early stage, but that it can directly impair the mitochondrial function, lower myocardial energy production, and contribute significantly to the myocardial dysfunction in the later stage of septic shock.  相似文献   
148.
Background We developed and evaluated the clinical usefulness of a scoring system that subclassified type Vi pit patterns. Methods We studied 119 colon cancer lesions (pTis, n = 26; pT1, n = 93) and 22 tubular adenoma lesions with severe atypia in which a type Vi pit pattern was visible under a stereomicroscope. Four type Vi pit pattern formation appearances (existing pits, marginal irregularities of the gland duct, narrowing of the gland duct lumen, and unclear outline of the gland duct) were defined, and the relationship between each appearance and the invasive depth of the cancer was evaluated. Results When the four type Vi pit pattern appearances were considered in a logistic regression analysis, the odds of a more invasive submucosal cancer were significantly increased by the appearance of marginal irregularities, a narrowed lumen, and an unclear outline. In the logistic regression analysis results, when 0.63 was used as the cutoff score for prediction of a more invasive submucosal cancer, 80 cases in the less invasive group were classified correctly (specificity, 1.0), whereas 53 (86.9%) of the 61 cases in the more invasive group were classified correctly (sensitivity, 0.869). Conclusions It is important first to understand the usability and limitations of objective scoring of type V pit pattern findings and then to apply this score to the determination of cancer depth in order to accurately identify lesions suitable for endoscopic treatment.  相似文献   
149.
This study was designed to clarify the mechanism of tolerance that occurs during prolonged administration of a beta-agonist in relation to membrane phospholipid degradation and to elucidate the effect of diltiazem, a calcium antagonist. Guinea pigs were divided into 3 groups: (1) control—physiological saline (0.5 ml) was injected once a day for 7 successive days; (2) metaproterenol (Mp)—Mp was injected intraperitoneally (10 mg/kg/day) for 7 successive days; (3) Mp + diltiazem—diltiazem was injected intraperitoneally (20 mg/kg/day) 30 min before Mp injection for 7 successive days. The number of beta-adrenoceptors and the 10−5 M (−)-isoproterenol-stimulated adenylate cyclase activity were significantly decreased in the metaproterenol group. Diltiazem reduced these decreases. Phospholipase activity was increased and phosphatidylcholine and phosphatidylethanolamine levels were decreased in the metaproterenol group. Diltiazem also reduced these changes. These results suggest that the degradation of membrane phospholipids by phospholipase may be involved in a decrease in beta-adrenergic response caused by successive administration of metaproterenol. Diltiazem protects membrane phospholipids from phospholipase attack, which in turn maintains beta-adrenergic responsiveness. Part of this study was presented at the Annual Meeting of the American Thoracic Society, May 12, 1987, New Orleans, Louisiana  相似文献   
150.
We investigated the relationship between insulin-resistance (IR) and remnant-like particle cholesterol (RLP-C) using 472 subjects (174 men and 298 women) randomly selected from inhabitants of two rural communities in Japan, Tanno and Sobetsu. The level of fasting immunoreactive insulin (FIRI), fasting blood glucose (FBS), total cholesterol (TC), triglyceride (TG), HDL cholesterol, LDL cholesterol, and RLP-C were measured in each subject. Homeostasis model assessment (HOMA-R) was used as an indicator of IR. The subjects were divided into two groups according to the value of HOMA-R: an IR group of subjects with HOMA-R > approximately equal to 1.73 and a normal (NR) group of subjects with HOMA-R <1.73. There was a significant positive correlation between HOMA-R and RLP-C. The value of RLP-C was higher in the IR group than in the NR group (7.1 vs. 3.9 mg/dl in men and 5.3 vs. 3.6 mg/dl in women). The frequency of hyper RLP cholesterolemia (RLP-C > approximately equal to 7.5 mg/dl) was higher in the IR than in the NR group (23.7 vs. 6.6% in men and 20.3 vs. 6.6% in women). The results of multiple regression analysis showed that HOMA-R was closely related to RLP-C. The results of this study suggest that RLP-C is closely associated with IR syndrome.  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