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   20619篇
  免费   1189篇
  国内免费   127篇
耳鼻咽喉   191篇
儿科学   399篇
妇产科学   218篇
基础医学   2348篇
口腔科学   568篇
临床医学   1364篇
内科学   5631篇
皮肤病学   677篇
神经病学   1105篇
特种医学   967篇
外科学   3802篇
综合类   94篇
一般理论   3篇
预防医学   571篇
眼科学   209篇
药学   1355篇
中国医学   39篇
肿瘤学   2394篇
  2023年   196篇
  2022年   415篇
  2021年   659篇
  2020年   338篇
  2019年   421篇
  2018年   555篇
  2017年   443篇
  2016年   493篇
  2015年   516篇
  2014年   666篇
  2013年   737篇
  2012年   1254篇
  2011年   1377篇
  2010年   749篇
  2009年   576篇
  2008年   1083篇
  2007年   1122篇
  2006年   1028篇
  2005年   942篇
  2004年   821篇
  2003年   723篇
  2002年   696篇
  2001年   454篇
  2000年   502篇
  1999年   413篇
  1998年   159篇
  1997年   135篇
  1996年   146篇
  1995年   102篇
  1994年   105篇
  1993年   109篇
  1992年   377篇
  1991年   329篇
  1990年   323篇
  1989年   330篇
  1988年   317篇
  1987年   298篇
  1986年   258篇
  1985年   244篇
  1984年   180篇
  1983年   166篇
  1979年   103篇
  1978年   71篇
  1977年   78篇
  1974年   76篇
  1973年   73篇
  1972年   74篇
  1971年   70篇
  1970年   80篇
  1969年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Clinical diagnosis of chronic cholecystitis is made based on diffuse hyperechoic thickening of the gallbladder wall as shown by ultrasonographic examination. We herein report three cases of chronic cholecystitis showing localized hypoechoic thickening of the gallbladder wall that mimicked gallbladder cancer by ultrasonography. Histologically, hypertrophy of the muscularis propria was a common characteristic finding in these three patients. A smooth surface of the inner hypoechoic layer of the thickened wall was considered to be a reliable finding in the differential diagnosis between this type of chronic cholecystitis and gallbladder cancer.  相似文献   
82.
A 77-year-old man, who underwent segmental pancreatectomy for intraductal papillary mucinous adenoma in 2001, was referred to our hospital with complaints of hematemesis and melena on January, 2004. Emergency upper gastrointestinal endoscopy showed a pulsating submucosal protrusion in the duodenal bulb, which was identified as a gastroduodenal arterial aneurysm measuring 1.5cm on abdominal CT imaging. Transcatheter arterial embolization of the aneurysm with metallic coils was successfully performed. Periodically repeated endoscopic examination has revealed the coils protruding into the duodenal lumen without any serious complication.  相似文献   
83.
To characterize apoptosis in keloids and the mechanisms responsible for this process, the expression of activated caspase-9 and -3 in fibroblasts obtained from keloids was analyzed. Immunohistochemistry revealed that the number of fibroblasts positive for terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) or activated caspase-9 or -3 was low but was significantly higher in keloid tissues than in normal scar tissues. Significant relationships between the number of caspase-positive fibroblasts and TUNEL-positive fibroblasts suggested that the activation of caspase-9 and -3 induces apoptosis in a subpopulation of keloid fibroblasts. All keloid fibroblast cell lines established in this study showed activation of caspase-9 and -3 after serum deprivation for 3 or 4 hours, as shown using Western blotting. Furthermore, serum deprivation-induced apoptosis in a keloid fibroblast line was blocked by a caspase-9 inhibitor (acetyl-Leu-Glu-His-Asp-al), indicating that activation of caspase-9 was necessary for the process of apoptosis in keloid fibroblasts. Although serum deprivation did not significantly change the level of apoptosis protease activating factor-1 in any of the lines, cytochrome c release was detected in cytosolic fractions of the lines after serum deprivation for 3 or 4 hours. These results strongly suggest that keloid fibroblasts are predisposed to apoptosis and cytochrome c release and that caspase-9 activation may underlie regulation of apoptosis in keloid fibroblasts in vivo.  相似文献   
84.
Prostaglandin E1 (PGE1) has several potential therapeutic effects, including cytoprotection, vasodilation, and inhibition of platelet aggregation. This study investigates the protective action of PGE1 against hepatic ischemia/reperfusion injury in vivo using a complementary DNA microarray. PGE1 or saline was continuously administered intravenously to mice in which the left lobe of the liver was made ischemic for 30 minutes and then reperfused. Livers were harvested 0, 10, and 30 minutes postreperfusion. Messenger RNA was extracted, and the samples were labeled with two different fluorescent dyes and hybridized to the RIKEN set of 18,816 full-length enriched mouse complementary DNA microarrays. Serum alanine aminotransferase and aspartate aminotransferase levels at 180 minutes postreperfusion were significantly lower in the PGE1-treated group than in the saline-treated group. The cDNA microarray analysis revealed that the genes encoding heat-shock protein (HSP) 70, glucose-regulated protein 78, HSP86, and glutathione S-transferase were upregulated at the end of the ischemic period (0 minutes postreperfusion) in the PGE1 group. Our results suggested that PGE1 induces HSPs immediately after ischemia reperfusion. HSPs might therefore play an important role in the protective effects of PGE1 against ischemia/reperfusion injury of the liver.  相似文献   
85.
BACKGROUND: Although there is increasing evidence suggesting that the vagus nerve functions as a connector between the nervous and immune systems in animals, little is known about the role of the vagus nerve in postoperative acute phase response in humans. MATERIALS AND METHODS: The extent of fever and acute phase protein response and the production of inflammatory cytokine during the early postoperative period were compared among the patients who had undergone total gastrectomy including truncal vagotomy (n = 13), those having distal gastrectomy with division of vagal branches (n = 14), and the patients with vagal nerve preserving gastrectomy (n = 12). RESULTS: There was no significant difference in serum levels of C-reactive protein, alpha-1-antirypsin, and interleukin-6 among the three groups. Also, postoperative maximum body temperature was similar. CONCLUSIONS: Vagotomy did not influence acute phase response after gastric cancer surgery. A multipathway mechanism for acute phase response including the induction of fever is suggested.  相似文献   
86.
Severe liver disease is an unusual but potentially fatal complication of sickle-cell disease (SCD). Liver transplantation has been complicated by ongoing SCD and thrombosis. We reviewed 214 pediatric transplants done at our institution from 1990 to 2005. Three patients were transplanted for complications of SCD, including intrahepatic cholestasis and viral hepatitis. Overall patient and graft survival was 66%. One patient died after 6 years from a subdural hematoma. There were not any incidences of graft loss, primary nonfunction, or thrombosis. All 3 patients required between 1 and 4 postoperative transfusions to keep hemoglobin (Hgb) >9 g/dL with an S fraction of less than 25%. One patient required a preoperative transfusion for a hemoglobin S (HbS) fraction of 30%. Mean follow-up has been 4.2 years (range, 2.6-5.4 years). All 3 children continued to suffer sequelae from their SCD. One child suffered from recurrent sickle-cell hepatopathy and chronic graft failure. In conclusion, children with SCD can in rare instances develop acute and chronic liver failure. These children can be successfully transplanted with good outcomes. Careful attention must be paid to HbS fraction and hemoglobin level to prevent sickling and vascular thrombosis. Unfortunately, liver transplant cannot alter the natural course of the disease.  相似文献   
87.
Subdural hygroma is a frequent delayed complication of head trauma. Most hygromas are clinically 'silent' and a few cases have shown slow deterioration in the chronic stage. We report a case of subdural hygroma showing unique radiological findings and rapid deterioration. A 74-years-old female presented with a mild headache and consciousness disturbance after head injury. Computed tomography showed a midline shift as a result of two components piling up in the subdural space; the outer components showed low density, the inner components high density. Magnetic resonance imaging demonstrated that these two subdural components were subdural hygroma and subarachnoid hematoma. Simple burr hole irrigation, rather than large craniotomy, was thought to be more appropriate treatment to reduce the mass effect. Simple burr hole irrigation was performed to remove the subdural hygroma and the patient showed an excellent recovery. Careful examination of the radiological findings prevented an unnecessary procedure in this case. A possible mechanism of this phenomenon is discussed.  相似文献   
88.
Abstract: A cell line, BAD05, derived from B lymphocytes of an adenosine deaminase (ADA; EC 3,5,4,4)-deficient patient could not proliferate in a serum-free medium containing 100 μmol/l deoxyadenosine. When BAD05 was cultured with ADA-positive fibroblasts, the proliferation of BAD05 was improved. BAD05 cell density increased when the initially mixed ratio of fibroblasts/BAD05 was 1/10 or higher, but decreased when the ratio was 1/20 or lower. Deoxyadenosine concentrations in the medium and ATP and deoxyATP (dATP) levels in the BAD05 were measured after 4 hours of coculture at initial BAD05 cell densities of 1 × 105and 1 × 106cells/ml. Deoxyadenosine concentrations in the medium decreased as the density of fibroblasts increased. The dATP level decreased as the mixed ratio rose. The ratio of fibroblasts/BAD05 rather than the cell density of fibroblasts had a larger effect on the dATP levels in BAD05. Under our experimental conditions, ADA-negative cells proliferated well when the ratio of ADA-positive cells/ADA-negative cells was over 1/10.  相似文献   
89.
Two cases of Trichosporon beigelli pneumonia in severely immunocompromised patients are reported. At autopsy, Trichosporon beigelii was detected in all lobes in one patient who had a small cell lung cancer. Polymycotic infection involving Trichosporon beigelii and Aspergillus was proved in the other patient who had a non-Hodgkin's lymphoma. Miconazole therapy was not effective against Trichosporon beigelii infection in both cases. Although diagnosis and management are difficult, Trichosporon beigelii must be considered as a cause of visceral opportunistic fungal infection.  相似文献   
90.
The authors examined pulmonary hemodynamics with respect to underlying diseases, severity and type of chronic respiratory failure, and the incidence and effect of home oxygen therapy (HOT) in 155 patients with chronic lung diseases (old pulmonary tuberculosis (OTB) 45, chronic pulmonary emphysema (CPE) 54, chronic bronchitis (CBR) 42 and fibrosing lung disease (FLD) 14). They underwent right heart catheterization during a stable period, while breathing room air. The arterial PO2 ranged from 64.3 +/- 9.7 Torr (CBR) to 69.9 +/- 10.0 Torr (CPE), and the mean pulmonary arterial pressure ranged from 17.3 +/- 4.6 mmHg (CPE) to 20.6 +/- 5.4 mmHg (OTB). The incidence of pulmonary hypertension (PH, PA mean greater than or equal to 20 mmHg) was 53.3% in OTB, 40% in CBR, 35.7% in FLD, 23.8% in CPE, 69% in respiratory failure, 40% in quasi-respiratory failure, and 2.1% in non-respiratory failure. The percentage of patients who received HOT was 84.5% in respiratory failure and 54.1% in quasi-respiratory failure. Comparing Type I with Type II chronic respiratory failure, the incidence of PH was lower in the former than the latter (38.3% vs 80.6%), whereas HOT was applied to an equal percentage of patients (67.4%) in both groups. The effect of HOT was evaluated in 11 patients with chronic respiratory failure. The mean pulmonary arterial pressure was 22.7 +/- 4.7 mmHg before HOT, and decreased to 20.7 +/- 5.6 mmHg after 24.5 +/- 10.1 months of HOT. Although this difference was not significant statistically, this result suggests the desirable effect of HOT on pulmonary hemodynamics.  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