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   1267篇
  免费   56篇
  国内免费   6篇
耳鼻咽喉   4篇
儿科学   65篇
妇产科学   24篇
基础医学   185篇
口腔科学   11篇
临床医学   65篇
内科学   284篇
皮肤病学   17篇
神经病学   57篇
特种医学   38篇
外科学   208篇
综合类   5篇
预防医学   55篇
眼科学   28篇
药学   68篇
肿瘤学   215篇
  2024年   1篇
  2023年   7篇
  2022年   23篇
  2021年   37篇
  2020年   21篇
  2019年   18篇
  2018年   21篇
  2017年   23篇
  2016年   17篇
  2015年   28篇
  2014年   41篇
  2013年   44篇
  2012年   70篇
  2011年   119篇
  2010年   46篇
  2009年   46篇
  2008年   72篇
  2007年   86篇
  2006年   99篇
  2005年   96篇
  2004年   74篇
  2003年   66篇
  2002年   88篇
  2001年   12篇
  2000年   10篇
  1999年   25篇
  1998年   22篇
  1997年   12篇
  1996年   17篇
  1995年   16篇
  1994年   15篇
  1993年   13篇
  1992年   4篇
  1991年   8篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1987年   4篇
  1986年   7篇
  1985年   4篇
  1984年   2篇
  1980年   2篇
  1978年   2篇
  1975年   1篇
  1971年   1篇
  1969年   1篇
  1968年   2篇
  1966年   1篇
排序方式: 共有1329条查询结果,搜索用时 15 毫秒
71.
An 88-year-old woman presented with a supratentorial primitive neuroectodermal tumor (PNET) manifesting as disturbance of consciousness and left hemiplegia. Magnetic resonance imaging showed a large mass lesion in the right frontotemporal region. She underwent biopsy of the lesion that confirmed the diagnosis of PNET. Her poor condition only allowed chemotherapy with methyl 6-[3-(2-chloroethyl)-3-nitrosoureido]-6-deoxy-alpha-D-glucopyranoside (MCNU), vincristine, and prednisolone to be performed. The patient died approximately 6 months after diagnosis due to enlargement of the tumor. Supratentorial PNET is a rare tumor, especially in adults. Multimodal therapy consisting of gross total or subtotal resection, radiation therapy, and chemotherapy is generally considered necessary for patients with supratentorial PNET. However, the condition of each patient should be considered in determining the therapeutic plan, especially in the case of extremely aged patients, since supratentorial PNET is malignant and long-term survival is rare despite aggressive treatment.  相似文献   
72.
PURPOSE: We assayed whether high serum carotenoids and antioxidative substances decrease the risk of urothelial cancer in a case-control study nested in a community based cohort in Japan, that is the Japan Collaborative Cohort Study. MATERIALS AND METHODS: Information on subject life-styles and serum were collected in 1988 to 1990 and subjects were followed as late as 1999. Individuals who had or died of urothelial cancer and controls were matched for study area, sex and age. Serum was stored at -80C and analyzed in 2003. Of 14,097 male and 25,662 female subjects 40 to 79 years old there were 42 cases, which were matched to 124 controls. RESULTS: The OR for the highest to lowest tertile of serum concentration was 0.28 (95% CI 0.07 to 1.15, trend p = 0.08) for beta-carotene, 0.36 (95% CI 0.10 to 1.27, trend p = 0.10) for total carotenes and 0.31 (95% CI 0.09 to -1.09, trend p = 0.09) for total carotenoids after adjustment for smoking in addition to matching variables. High concentrations of tocopherols and xanthophylls slightly tended to decrease the risk of urothelial cancer. In contrast, serum retinol, oxidized low density lipoprotein and Cu/Zn-superoxide dismutase were not associated with urothelial cancer risk. CONCLUSIONS: Our results suggest that high serum carotenoids may decrease the risk of urothelial cancer with carotenes more effective than xanthophylls.  相似文献   
73.
74.
We have examined ischemic tolerance induced by electroconvulsive shock before exposure to forebrain ischemia. Subjects were 40 rats, which were randomly allocated to control, single ECS (sECS), repeated ECS (rECS) or sham group. sECS group and rECS group received ECS only once 2 days before the subsequent 8-min forebrain ischemia and once a day for 9 consecutive days until 2 days before the exposure to ischemia, respectively. Forebrain ischemia was produced by modified bilateral carotid artery occlusion technique. Control group underwent brain ischemia without ECS pretreatment. Sham group received ECS without following exposure to ischemia. Pyramidal cell injury of the hippocampal CA1 sector was microscopically examined on the 7th day after the ischemic exposure or the sham operation. Damage of the pyramidal cells was assessed by the injury ratio, which was ratio of non-viable pyramidal cells to the whole pyramidal cells. The injury ratios of CA1 pyramidal cells in sECS, rECS and control groups were 30.5 +/- 10.8 (n=10), 42.3 +/- 18.4% (n=10) and 90.4 +/- 2.9% (n=9), respectively. The injury ratios in sECS and rECS groups were lower than the ratio in control group (p<0.01), while the ratios of sECS and rECS groups were not different. The pyramidal cells in sham group were intact. Our results indicate that both preconditionings of sECS and rECS have a potency to induce delayed tolerance against temporary forebrain ischemia, though the potency was not different between sECS and rECS. Electroconvulsive shock may be added to the list of preconditioning stimuli to protect brain against ischemic neuronal damage.  相似文献   
75.
We report a 57-year-old woman with a primary hepatic carcinoid tumor who had been suffering from symptoms due to carcinoid syndrome and carcinoid heart disease for more than 9 years. Long-term injection of octreotide acetate was fairly effective to relieve the symptoms due to carcinoid syndrome, but its tumor contraction effect was not confirmed. The massive ascites in the follow-up period appeared to be diminished to a certain extent by timely chemotherapy including cisplatin. The patient died of multi-organ failure about 9 years after the onset of disease. Autopsy confirmed a primary hepatic carcinoid tumor with limited distant metastases.  相似文献   
76.
77.
Thre newly isolated human rotaviruses in MA104 cells were used as antigens in the neutralization test of paired sera of infants and young children with acute gastroenteritis during three epidemic seasons. Twenty-three of 41 paired sera (56%) from outpatients with acute gastroenteritis responded with development of NT antibody to one, two, or three antigens. Of 23 paired sera which showed significant rises of antibody to any strain, 20 paired sera (87%) responded to strain Hochi, 15 cases (65%) to strain Ito, and 16 cases (70%) to strain Nemoto. Ten of 14 cases that were seronegative to any isolated strain at onset of illness showed significant rises of antibodies to three strains. Three strains were determined to be subgroup 2 by RNA pattern and were recently found to be similar if not identical to serotype 3 and 4 by Wyatt et al. The neutralization test showed extensive immunologic cross-reativity among these strains. The rate of acquisition of serum antibody by age was similar with the three antigens.  相似文献   
78.
The worldwide increase of type 2 diabetes in youth is a critical problem. It is important to prevent the development of type 2 diabetes in high-risk individuals. In many patients with type 2 diabetes, hyperglycemia can be reduced with appropriate changes in diet and exercise. However, some patients with persistent HbA1c levels >7.5% need pharmacological therapy to improve their metabolic control. A variety of oral hypoglycemic agents, including alpha-glucosidase inhibitors, sulfonylureas and metformin, are available. Metformin is widely used in pediatric patients and is considered to be the most effective oral agent. In some cases, combination therapy with metformin and sulfonylureas or use of insulin is more effective to stabilize glycemia. The approach to insulin therapy in type 2 diabetes often differs from that used in type 1 diabetes. The therapeutic approach to childhood type 2 diabetes should be individually tailored.  相似文献   
79.
Extraskeletal osteosarcoma is a rare malignant soft-tissue tumor. There are few reports describing the radiological findings of this tumor, especially concerning its MRI and scintigraphic appearance. We report a 58-year-old man with extraskeletal osteosarcoma in the thigh. Radiographs showed small foci of mineralization in the mass. The tumor showed low intensity on T1-weighted images and predominantly high intensity on T2-weighted images, and the tumor was heterogeneously well enhanced on Gd-DTPA-enhanced T1-weighted images. Bone scintigraphy showed extraskeletal uptake in the tumor, and thallium-201 scintigraphy revealed marked inhomogeneous accumulation.  相似文献   
80.
Thymidine phosphorylase (TP) catalyzes the reversible conversion of thymidine to thymine, thereby generating 2-deoxy-D-ribose-1-phosphate, which upon dephosphorylation forms 2-deoxy-D-ribose (D-dRib), a degradation product of thymidine. We have previously shown that D-dRib promotes angiogenesis and chemotaxis of endothelial cells and also confers resistance to hypoxia-induced apoptosis in some cancer cell lines. 2-Deoxy-L-ribose (L-dRib), a stereoisomer of D-dRib, can inhibit D-dRib anti-apoptotic effects and suppressed the growth of KB cells overexpressing TP (KB/TP cells) transplanted into nude mice. In this study, we examined the ability of L-dRib to suppress metastasis of KB/TP cells using two different models of metastasis. The antimetastatic effect of L-dRib was first investigated in a liver-metastasis model in nude mice inoculated with KB/TP cells. Oral administration of L-dRib for 28 days at a dose of 20 mg/kg/day significantly reduced the number of metastatic nodules in the liver and suppressed angiogenesis and enhanced apoptosis in KB/TP metastatic nodules. Next, we compared the ability of L-dRib and tegafur alone or in combination to decrease the number of metastatic nodules in organs in the abdominal cavity in nude mice receiving s.c. of KB/TP cells into their backs. L-dRib (20 mg/kg/day) was significantly (P < 0.05) more efficient than tegafur (100 mg/kg/day) in decreasing the number of metastatic nodules in organs in the abdominal cavity. By in vitro invasion assay, L-dRib also reduced the number of invading KB/TP cells. L-dRib anti-invasive activity may be mediated by its ability to suppress the enhancing effect of TP and D-dRib on both mRNA and protein expression of vascular endothelial growth factor and interleukin-8 in cultured KB cells. These findings suggest that L-dRib may be useful in a clinical setting for the suppression of metastasis of tumor cells expressing TP.  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