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   2529篇
  免费   156篇
  国内免费   26篇
耳鼻咽喉   38篇
儿科学   41篇
妇产科学   60篇
基础医学   363篇
口腔科学   75篇
临床医学   150篇
内科学   451篇
皮肤病学   43篇
神经病学   239篇
特种医学   43篇
外科学   690篇
综合类   5篇
预防医学   86篇
眼科学   12篇
药学   153篇
中国医学   5篇
肿瘤学   257篇
  2023年   13篇
  2022年   13篇
  2021年   33篇
  2020年   26篇
  2019年   34篇
  2018年   43篇
  2017年   36篇
  2016年   41篇
  2015年   53篇
  2014年   58篇
  2013年   66篇
  2012年   108篇
  2011年   121篇
  2010年   78篇
  2009年   54篇
  2008年   89篇
  2007年   120篇
  2006年   129篇
  2005年   135篇
  2004年   125篇
  2003年   130篇
  2002年   134篇
  2001年   110篇
  2000年   80篇
  1999年   83篇
  1998年   42篇
  1997年   36篇
  1996年   30篇
  1995年   15篇
  1994年   11篇
  1993年   26篇
  1992年   70篇
  1991年   71篇
  1990年   37篇
  1989年   59篇
  1988年   45篇
  1987年   36篇
  1986年   44篇
  1985年   44篇
  1984年   28篇
  1983年   25篇
  1982年   15篇
  1979年   18篇
  1976年   13篇
  1974年   10篇
  1972年   10篇
  1971年   12篇
  1970年   17篇
  1969年   15篇
  1968年   13篇
排序方式: 共有2711条查询结果,搜索用时 31 毫秒
91.
92.
European Journal of Nuclear Medicine and Molecular Imaging - 18F-fluoromisonidazole (18F-FMISO) is the most widely used positron emission tomography (PET) tracer for imaging tumor hypoxia. Previous...  相似文献   
93.
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide considered to be a potent regulator of astrocytes. It has been reported that PACAP also affects astrocytoma cell properties, but the proliferative effects of this peptide in previous reports were inconsistent. The purpose of this study was to search for correlations between malignant potential, PACAP/PACAP receptor expression, and the proliferative potential of four astrocytoma cell lines (KNS-81, KINGS-1, SF-126, and YH-13). Immunohistochemical observations were performed using astrocyte lineage markers with a view to establishing malignant potential, which is inversely correlated to differentiation status in astrocytoma cells. YH-13 showed the most undifferentiated astrocyte-like status, and was immunopositive to a cancer stem cell marker, CD44. These observations suggest that YH-13 is the most malignant of the astrocytoma cell lines tested. Moreover, the strongest PAC1-R immunoreactivity was observed in YH-13 cells. Using real-time PCR analysis, no significant differences among cell lines were detected with respect to PACAP mRNA, but PAC1-R and VPAC1-R mRNA levels were significantly increased in YH-13 cells compared with the other cell lines. Furthermore, when cell lines were treated with PACAP (10?11 M) for 3 days, the YH-13 cell line, but not of the other cell lines, exhibited a significantly increased cell number. These results suggest that PACAP receptor expression is correlated with the malignant and proliferative potential of astrocytoma cell lines.  相似文献   
94.
95.
96.
1.2C–4Cr–4Mo–10W–3.5V–10Co–Fe high-speed steel (JIS SKH57; ISO HS10-4-3-10) is often manufactured via casting and forging. By applying powder metallurgy, the properties of the abovementioned material can be improved. In this study, the effects of sintering conditions on the formation of precipitates and pores are evaluated. Additionally, strength with and without hydrostatic pressure during sintering is evaluated via static bending and impact tests. Sintering via hot isostatic pressing (HIP) at 1463 K can effectively eliminate pores and prevent the coarsening of precipitates. Toughness and strength improved by 50% by applying HIP.  相似文献   
97.
Hepatic resection for colorectal metastases   总被引:3,自引:1,他引:3  
PURPOSE: Hepatic resection affords the best hope of survival for patients with colorectal carcinoma metastatic to the liver. However, recurrences are observed in about 60 percent of patients after curative hepatic resection. The purpose of this study was to examine the prognostic factors of patients undergoing curative hepatic resection for colorectal metastases. METHODS: Between April 1984 and September 1997, 168 patients underwent curative hepatic resection for colorectal metastases. The clinicopathologic factors studied for prognostic value were gender, age, primary site, nodal status of primary tumor, time of metastases, preoperative serum level of carcinoembryonic antigen, hepatic tumor size and distribution, number of metastases, type of hepatic resection, resection margin, presence of micrometastases in resected specimen and microscopic fibrous pseudocapsule between the hepatic tumor and surrounding hepatic parenchyma, nodal status of hepatoduodenal ligament, adjuvant regional chemotherapy, and perioperative transfusion. RESULTS: The overall survival was 42 percent at three years and 26 percent at five years, including a 3.5 percent 60-day surgical mortality rate. Thirty-one percent of patients had micrometastases located at a median distance of 3 mm from the metastatic tumor edge. Presence of microscopic fibrous pseudocapsule was observed in 28 percent of patients. Univariate and multivariate analyses showed that significant prognostic factors for survival were nodal status of primary tumor, number of metastases, resection margin, microscopic fibrous pseudocapsule, and adjuvant regional chemotherapy. CONCLUSIONS: We conclude that 1) hepatic resection is effective in select patients with colorectal metastases; 2) adequate resection margin and adjuvant regional chemotherapy can improve outcome; and 3) microscopic fibrous pseudocapsule may offer additional postoperative information as an independent prognostic factor.Presented at the 11th Biennial Scientific Meeting of the Asian Pacific Association for the Study of the Liver, Perth, Western Australia, February 16 to 20, 1998.  相似文献   
98.
Two patients underwent valve surgery using the minimally invasive approach. A 51-year-old man underwent mitral valve repair for chronic mitral regurgitation due to prolapse of the posterior mitral leaflet. The left-half of his sternum was cut in "C" shape below the level of the second intercostal space, and all of the arterial or venous cannulas were inserted via this single access. A 37-year-old man underwent aortic valve replacement for aortic valve regurgitation due to infective endocarditis. Right upper partial sternotomy between the first and fourth intercostal space was selected for this aortic valve surgery. The median skin incisions were as small as 12 and 9 cm. Postoperative recovery was very smooth. Minimally invasive approach using selected partial sternotomy provides acceptable results with a good exposure, and is an alternative approach to valve surgery.  相似文献   
99.
OBJECTIVES: Crohn's disease (CD) is recognized to be a vascular endothelial-associated disease. Angiotensin I-converting enzyme (ACE) exists mainly in endothelial cells. There are some reports on serum ACE levels in patients with CD, but the ACE level is still controversial. Recently, genetic control of serum ACE levels by ACE gene polymorphisms (classified as II, ID, and DD) has been suggested. Although we must consider such polymorphisms to elucidate ACE levels in patients with CD, there is no report about this. METHODS: We studied 341 healthy controls (male/female = 178/162), 39 patients with CD (31/8), 43 patients with ulcerative colitis (UC) (22/21) and 19 patients with infectious enterocolitis (8/11). The polymorphism in intron 16 of the ACE gene was examined by PCR. Serum ACE levels were measured by the method of Kasahara. RESULTS: Serum ACE levels in patients with CD and UC were significantly lower than in healthy controls, irrespective of the genotype of ACE (genotype II: CD 7.0+/-2.5 [mean +/- SD], UC 7.1+/-3.3, controls 11.8+/-2.9, genotype ID: CD 9.7+/-4.1, UC 11.4+/-4.6, controls 15.2+/-3.6, genotype DD: CD 13.9+/-5.8, UC 10.7+/-3.6, controls 19.3+/-3.9 IU/L, controls vs CD, UC; p < 0.01, 0.05). However, there was no significant difference in serum ACE levels between CD and UC. CONCLUSIONS: Considering ACE gene polymorphism, serum ACE levels in patients with inflammatory bowel disease are lower than in controls. Serum ACE levels reflect a part of the pathogenesis of inflammatory bowel disease.  相似文献   
100.
AIM: To investigate the effect of HER-2/neu protein overexpression on chemoresistance and prognosis in patients with epithelial ovarian carcinoma. METHODS: A total of 141 ovarian carcinoma tissues surgically resected between 1987 and 2003 were assessed by immunohistochemistry (IHC). The characteristic of the patients and immunohistochemical results were compared by chi2-test. Survival analysis was performed by the Kaplan-Meier method and the log-rank test. RESULTS: HER-2/neu overexpression was detected in 18 cases (12.8%). There were no significant differences in histopathological subtypes (P = 0.3550), FIGO stages (P = 0.8858), or residual tumor size at first surgery (P = 0.6607) between the cases with HER-2/neu overexpression and the cases without HER-2/neu overexpression. Among the 58 cases which responded to chemotherapy, only five cases (8.6%) showed HER-2/neu overexpression. However, among the 38 cases which did not respond to chemotherapy, eight cases (21.1%) showed HER-2/neu overexpression. Overexpression of HER-2/neu had a tendency to relate with chemoresistance of epithelial ovarian carcinoma, but there were no statistically significant differences (P = 0.0817). No association was observed between HER-2/neu overexpression and cumulative survival rate (P = 0.4970). CONCLUSIONS: The results of the current study show that although HER-2/neu overexpression has a tendency to be associated with chemoresistance, it can not be a prognostic factor for the patients with epithelial ovarian carcinoma.  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