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   3958篇
  免费   232篇
  国内免费   21篇
耳鼻咽喉   47篇
儿科学   70篇
妇产科学   42篇
基础医学   605篇
口腔科学   82篇
临床医学   227篇
内科学   946篇
皮肤病学   90篇
神经病学   270篇
特种医学   176篇
外科学   494篇
综合类   18篇
预防医学   108篇
眼科学   134篇
药学   305篇
中国医学   10篇
肿瘤学   587篇
  2023年   39篇
  2022年   86篇
  2021年   125篇
  2020年   66篇
  2019年   86篇
  2018年   104篇
  2017年   83篇
  2016年   96篇
  2015年   77篇
  2014年   118篇
  2013年   147篇
  2012年   222篇
  2011年   250篇
  2010年   150篇
  2009年   88篇
  2008年   195篇
  2007年   169篇
  2006年   211篇
  2005年   187篇
  2004年   202篇
  2003年   184篇
  2002年   188篇
  2001年   108篇
  2000年   122篇
  1999年   86篇
  1998年   48篇
  1997年   40篇
  1996年   34篇
  1995年   25篇
  1994年   20篇
  1993年   20篇
  1992年   64篇
  1991年   62篇
  1990年   67篇
  1989年   74篇
  1988年   41篇
  1987年   36篇
  1986年   47篇
  1985年   36篇
  1984年   32篇
  1983年   28篇
  1981年   14篇
  1980年   14篇
  1979年   20篇
  1978年   7篇
  1974年   7篇
  1973年   9篇
  1972年   8篇
  1971年   8篇
  1967年   10篇
排序方式: 共有4211条查询结果,搜索用时 15 毫秒
61.
In the present study we evaluated the cell density of lens epithelium and its relation to the degree of erythrocyte aldose reductase (AR) in patients with type 2 diabetes. This prospective clinical study included 46 eyes of patients with type 2 diabetes and 48 eyes of patients without diabetes mellitus (DM). Flat preparations of lens epithelial cells (LECs) attached to the anterior capsule were studied. Multiple regression analysis was performed to evaluate the association between lens cell density and age, gender, type of cataract, duration of diabetes, diabetic retinopathy (DR), the levels of glycosylated hemoglobin (HbA1c) and erythrocyte AR. The mean density of LECs of patients with type 2 diabetes was 4,141+/-508cells/mm(2), which was significantly lower than that of patients without DM (4,560+/-458cells/mm(2); p<0.0001). Multiple regression analysis revealed that the level of erythrocyte AR was correlated with the reduction of LECs in the eyes of patients with type 2 diabetes. The correlation between the density of LECs and the amount of erythrocyte AR was significant in the diabetic group with a high value of HbA1c (>6.5%) or with DR. These results suggest that the polyol pathway via AR may be associated with the reduction of epithelial cell density in the eyes of patients with DM.  相似文献   
62.
63.
64.
65.
Background: Achieving long-term gene expression in kidney will be beneficial for gene therapy of renal and congenital diseases, genetic studies constructing animal disease models, and the functional analysis of disease-related genes.

Purpose: The purpose of this study was to develop an in vivo long-term gene expression system in murine kidney using ?C31 integrase.

Methods: Gene expression in cultured RENCA, TCMK-1, and HEK293 cells was assessed. The long-term in vivo gene expression system in the kidney was achieved by co-transfecting 5?µg of pORF-luc/attB as a donor plasmid and 20?µg of pCMV-luc as a helper plasmid into the right kidney of mice by electroporation. Luciferase expression levels were measured to determine longevity of the expression.

Results: Significantly high luciferase expression levels were observed in cultured RENCA, TCMK-1, and HEK293 cells over 1 month compared with controls (non-integrase system). The luciferase cDNA sequence was integrated at a pseudo attP site termed mpsL1. In vivo luciferase expression levels in the integrase group were sustained and significantly higher than those in the control group over 2 months. Furthermore, ?C31 integrase-transfected cells had less genomic DNA damage caused by integrase expression.

Discussion and conclusion: These results demonstrated that the ?C31 integrase system could produce long-term (2 months) in vivo gene expression in mouse kidney.  相似文献   
66.
BACKGROUND: The clinical significance of the white blood cell (WBC) count on admission in relation to the duration of ischemia in acute myocardial infarction (AMI) remains unclear. METHODS AND RESULTS: The relationship of the WBC count on admission to myocardial reperfusion was examined in 135 patients with recanalization of an anterior AMI within 6 h of symptom onset. Patients were classified according to the WBC count on admission: Group L (n=75), WBC count <12,000 cells/mm(3) and group H (n=60), WBC count >or=12,000 cells/mm(3). Peak creatine kinase (CK) was higher and impaired myocardial reperfusion, defined as a myocardial blush grade of 0/1, was more frequent in group H than in group L. Among the patients in group H, those with early (3 h) recanalization; however, peak CK and the incidence of impaired myocardial reperfusion were similar in these subgroups of patients. Multivariate analysis showed that WBC count >or=12,000 cells/mm(3) on admission was an independent predictor of impaired myocardial reperfusion in patients with early recanalization (odds ratio 7.9, p=0.04), but not in those with late recanalization. CONCLUSIONS: A higher WBC count may be associated with progression of myocardial damage after recanalization in patients with early recanalization of an anterior AMI.  相似文献   
67.
The amino acid sequences of the Env V3 region of HIV-1 subtype E in Thailand were highly variable in the samples obtained from 1995 to 1997, compared with the previously reported sequences in samples obtained from 1990 to 1993. The sequences of the V3 region in the samples from five provinces in Thailand revealed that the variability was much higher in the samples from Bangkok and Ubonrachathani than in those from Chiangmai, Prathumthani, and Trang. There was no apparently different level of diversity at the V3 region in the samples from symptomatic and asymptomatic individuals. The V3 loop motif in most (66.7%) of the samples was GPGQ, although this motif was more heterogeneous in the samples from Bangkok and Ubonrachathani than in those from the other three provinces. The N-linked glycosylation sites in the V3 region among these samples were relatively conserved. There was no apparent difference in the presence of positively charged amino acids at positions 306 and 320 between the samples from symptomatic and asymptomatic individuals.  相似文献   
68.
Annals of Nuclear Medicine - Although previous studies have investigated age and gender effects on striatal subregional dopamine transporter (DaT) binding, these studies were mostly based on a...  相似文献   
69.
It is now well recognized that hemophagocytic syndrome (HPS) is occasionally associated with malignant lymphomas. However, its association with Hodgkin's disease has been only rarely reported. We present here a 72-year-old woman manifesting with HPS as the primary and solitary clinical symptom of Hodgkin's disease. She had been suffering from high-grade fever and anemia for more than a month. Based on the findings in bone marrow aspirates, she was diagnosed as having HPS. In spite of extensive surveys including various cultures, serological tests for collagen disease, abdominal and cardiac sonography, chest computed tomography (CT), and renal biopsy, the origin of the fever was not determined. She was treated with steroid pulse therapy and then referred. Radiological studies revealed only mild hepatosplenomegaly and small lymph node swellings around celiac and common hepatic arteries. Reevaluation of the bone marrow specimen revealed the infiltration of small numbers of CD30-, CD15-, and EBER-1-positive large-sized lymphocytes with bizarre nucleus. Under the diagnosis of Hodgkin's disease, she was treated with combination chemotherapy containing pirarubicin, cyclophosphamide, vincristine, and prednisolone. However, it was not effective and she died of rapidly progressive hepatic failure on the 5th day of the chemotherapy. Autopsy was performed, which showed proliferation of lymphoma cells in para-aortic lymph nodes. We believe that diagnostic survey to rule out the underlying lymphoma should be vigorously performed for patients with hemophagocytic syndrome of unknown origin.  相似文献   
70.
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