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   5197篇
  免费   313篇
  国内免费   40篇
耳鼻咽喉   28篇
儿科学   75篇
妇产科学   68篇
基础医学   644篇
口腔科学   137篇
临床医学   361篇
内科学   1154篇
皮肤病学   255篇
神经病学   368篇
特种医学   184篇
外科学   793篇
综合类   18篇
预防医学   182篇
眼科学   66篇
药学   586篇
中国医学   6篇
肿瘤学   625篇
  2023年   26篇
  2022年   71篇
  2021年   114篇
  2020年   59篇
  2019年   78篇
  2018年   114篇
  2017年   98篇
  2016年   109篇
  2015年   93篇
  2014年   101篇
  2013年   111篇
  2012年   193篇
  2011年   221篇
  2010年   139篇
  2009年   110篇
  2008年   191篇
  2007年   217篇
  2006年   208篇
  2005年   227篇
  2004年   191篇
  2003年   232篇
  2002年   224篇
  2001年   211篇
  2000年   229篇
  1999年   217篇
  1998年   81篇
  1997年   49篇
  1996年   59篇
  1995年   54篇
  1994年   48篇
  1993年   42篇
  1992年   148篇
  1991年   147篇
  1990年   110篇
  1989年   147篇
  1988年   109篇
  1987年   114篇
  1986年   86篇
  1985年   84篇
  1984年   59篇
  1983年   45篇
  1982年   31篇
  1979年   47篇
  1978年   28篇
  1977年   20篇
  1974年   27篇
  1970年   19篇
  1969年   22篇
  1968年   20篇
  1966年   20篇
排序方式: 共有5550条查询结果,搜索用时 15 毫秒
101.
PURPOSE: Stroma cells play a relevant role in tumor development and progression. We investigated the activity of herceptin (HER), a humanized monoclonal antibody widely used for the treatment of HER2-overexpressing epithelial cancer, toward stroma cell lines L87/4 and L88/5. EXPERIMENTAL DESIGN: We studied the antiproliferative potential of HER and role of human serum in HER activity. We also investigated the ability of HER to alter ancillary functions of L87/4 and L88/5, such as support to long-term hematopoiesis, growth factor production, breast cancer cell adhesion, and proliferation. RESULTS: Flow cytometry showed that HER2 membrane expression in L87/4 and L88/5 stroma cells was intermediate between the expression in HER2-negative/dim MCF-7 breast cancer cells and HER2-bright SK-BC3 breast cancer cells. HER2 gene amplification was not detected by fluorescence in situ hybridization in either stromal cell lines. HER significantly inhibited L87/4 and L88/5 proliferation. Mean ID(50)s were found to be 2000 and 1700 micro g/ml for L87/4 and L88/5, respectively, after 3-day exposure and 800 micro g/ml for both cell lines after 9-day exposure. The presence of 10% human serum in the culture increased HER inhibitory activity. IC(50) of stroma cells was found to be intermediate between HER2-bright breast cancer cells (SK-BC3) and HER2-negative/dim breast cancer cells (MCF-7). The drug did not significantly affect the ability of stroma cells to support long-term hematopoiesis in the cobblestone area forming cell assay. In contrast, in coculture assay, MCF7 cells demonstrated a worse adhesion and growth capability on HER-treated stroma layers when compared with untreated stroma. Moreover, HER significantly reduced vascular endothelial growth factor production by L88/5 cells. CONCLUSIONS: Our data support the novel finding that HER may have a relevant activity against stroma cells.  相似文献   
102.
Two case reports of femoral bone lesions simulating lumbar spinal disease are presented. Physical examination and case history were strongly suggestive of lumbar spinal pathology. In case 1, surgical resection of a venous hemangioma in the lumbar epidural space was performed but did not relieve pain. In case 2, conservative treatments for a protruded disk were performed for 3 months before an accurate diagnosis was made. After correct diagnoses were made, excision of the femoral tumors brought rapid relief of all abnormal findings in both cases. Compared with other causes of sciatica, femoral bone tumors are rare. However, careful attention should be paid to rule out these lesions if the diagnosis of a lumbar spinal disease is uncertain. Bone scintigraphy seems to be a sensitive diagnostic method to detect extraspinal osseous lesions.  相似文献   
103.
Case: We present a case of HELLP syndrome occuring in a patient who at the age of 8 years had undergone a splenectomy for idiopathic thrombocytopenic purpura. She was diagnosed as having HELLP syndrome 37 weeks of gestation and had a cesarean section. Received: 4 June 1996 / Accepted: 7 October 1996  相似文献   
104.
The modifying effects of quinacrine administration during the post-initiation phase of carcinogenesis were investigated in hamsters treated with N -nitrosobis(2-oxopropyl)amine (BOP). Female Syrian hamsters were given three weekly s.c. injections of BOP at a dose of 10 mg/kg and then 300 or 100 ppm quinacrine in their diet for 37 weeks. Additional groups of animals received the BOP injection alone, or only the 300 ppm quinacrine treatment as BOP-negative controls. At week 40 of the experiment, all surviving animals were killed and development of proliferative lesions was assessed histopathologically. The multiplicity of pancreatic adenocarcinomas and dysplastic lesions per hamster was significantly higher ( P <0.01 and P <0.05) in the BOP/Q100 group (1.92 and 1.78) than in the BOP-alone group (1.07 and 0.79). The incidence of hepatocellular adenomas plus carcinomas was also significantly elevated ( P <0.05) in the BOP/Q300 and BOP/Q100 groups. In contrast, the multiplicity of lung adenomas plus adenocarcinomas was significantly decreased ( P <0.05) by the Q300 treatment. Neither the incidence nor the multiplicity of renal cell tumors (adenomas and carcinomas) or nephroblastomas significantly differed between the BOP-treated groups. Electron microscopic examination revealed an abundance of myeloid lamellar bodies filling the cytoplasm of hepatocytes and pancreatic ductular and acinar cells, and epithelial cells of the gallbladder in the quinacrine-treated animals, the degree being dose-dependent. Our results indicate that quinacrine enhances pancreatic and hepatic carcinogenesis in hamsters induced by BOP.  相似文献   
105.
Agaricus blazei Murrill, an edible mushroom, is widely used as a functional food due to its possible medicinal effects. Aqueous extracts are also used as food additive to provide an agreeable bitter taste. As a part of its safety assessment, the present 90-day subchronic toxicity study was performed in F344 rats. To establish a no-observed-adverse-effect level (NOAEL), rats were fed powder diet containing A. blazei Murrill aqueous extract at dose levels of 0 (basal diet), 0.63, 1.25, 2.5 and 5% (maximum) for 90 days. During the experiment, there were no remarkable changes in general appearance and no deaths occurred in any experimental group. Although serum blood urea nitrogen was slightly but significantly increased in males of the 2.5 and 5% groups, no related histopathological changes were observed in the kidney, and serum creatinine levels were rather reduced, suggesting the increase of blood urea nitrogen to be of little toxicological significance. Hematology, organ weight measurement and histopathological observation revealed no test compound-related toxicological changes. In conclusion, A. blazei Murrill extract even at 5% in the diet (2654 mg/kgb.w./day for male rats and 2965 mg/kgb.w./day for female rats) did not cause remarkable adverse effects in F344 rats. Thus, the NOAEL was concluded to be 5% in the diet.  相似文献   
106.
Docosahexaenoic acid (DHA), a 22-carbon fatty acid with six double bonds, is one of the major polyunsaturated fatty acids in fish oils or in the mammalian central nervous system and is believed to be essential for neuronal plasticity and development. In the present study, we evaluated the effect of DHA on hippocampal neurotransmissions using anesthetized rats. Field excitatory postsynaptic potential (fEPSP) evoked by stimulation of the Schaffer collaterals was recorded from the CA1 stratum radiatum. Following intracerebroventricular injection of DHA 25 nmol, the fEPSP slope decreased gradually in 30 min and was eventually suppressed by about 30%. On the other hand, when fEPSP was evoked by stimulation of the perforant path was recorded in the molecular layer of the dentate gyrus, an increase in fEPSP slope occurred over a similar time course after DHA injection. These phenomena were independent of N-methyl-D-aspartate receptor activity. Linoleic acid, one of polyunsaturated fatty acids, was virtually ineffective. Furthermore, we investigated the effect of DHA on hippocampal synaptic plasticity. Although DHA did not alter the profile of paired-pulse facilitation, it inhibited the induction of long-term potentiation in the CA1 area but not in the dentate gyrus. Thus, DHA exerts regionally different effects on hippocampal neurotransmission and may be a good tool for clarifying physiological functions of the hippocampus.  相似文献   
107.
Steno-Occlusive Changes in the External Carotid System in Moyamoya Disease   总被引:1,自引:0,他引:1  
To evaluate the steno-occlusive changes in the external carotid system in moyamoya disease, cerebral angiograms of 39 moyamoya patients were retrospectively reviewed. There were 26 females and 13 males, age ranged from 4 to 62 years with a mean of 26 years. Initial symptoms were ischaemia in 27 patients, haemorrhage in 9, and none in 3. Stenosis, occlusion, and dilatation in the external carotid system were analysed angiographically. No stenosis or occlusion of the superficial temporal artery, middle meningeal artery, or occipital artery was observed in either preoperative or postoperative follow-up angiograms in any patients. Steno-occlusive changes do not occur in the external carotid system, but are confined in the internal carotid system in moyamoya disease.  相似文献   
108.
109.
A research by questionnaire was conducted at three medical institutions, on basic attributes and psychosocial states of alcoholics' as first time inpatient and respective families. After a year of research, additional study was conducted in regard of abstinence, treatment continuation as outpatient, participation in self-help groups, and family's participation in family groups. Outcomes of researches' statistical analyses showed significant differences concerning medical institutions and basic attributes for the items: treatment histories of alcoholism, treatment or inpatient in other medical departments and alcoholic's family history,; but these differences were considered to be associated with varied courses of referrals. In relation to medical institutions with patients and family's psychosocial states, there were no significant differences on the outcomes of five scales. As for the correlation between medical institutions with a year's prognoses there were no significant differences concerning abstinence and treatment continuation as outpatient. In case of participation in self-help groups and family groups, the prognoses showed significant differences but these differences were considered to be related to varied treatments and different helping ways of medical institutions and varied conditions of local communities for mentioned helps.  相似文献   
110.
We have reported that excess soybean treatment and iodine deficiency synergistically interact, resulting in remarkable induction of thyroid hyperplasias in rats. In the present study, modifying effects of excess soybean and iodine-deficient diets were investigated in the post-initiation phase of N-bis(2-hydroxypropyl)nitrosamine [DHPN]-initiated thyroid tumorigenesis in rats. AIN-93G in which casein was replaced with gluten was used as a basal diet to avoid possible iodine contamination. In Experiment 1, F-344 rats of both sexes were sc injected with DHPN at a dose of 2800 mg/kg body weight and then fed a diet containing 0%, 0.8%, 4%, or 20% defatted soybean for 12 weeks, with proportional replacement of gluten by soybean flour. Although no thyroid proliferative lesions were found in any group, the absolute thyroid weights were significantly (p < 0.01) elevated with the 20% soybean treatment. In Experiment 2, after similar sc injection of DHPN, rats were fed a basal diet or a diet containing 20% soybean under iodine normal or deficient conditions for 12 weeks. Soybean feeding to both sexes under iodine deficient but not normal conditions dramatically enhanced the development of thyroid follicular adenomas (p < 0.01) and adenocarcinomas (p < 0.05), in good agreement with decrease in thyroxine and increase in thyroid-stimulating hormone. Thus co-exposure to excess soybean and iodine deficiency results in synergistic promotion of DHPN-initiated thyroid tumorigenesis in rats, of which mechanisms appear to primarily involve effects on serum hormone levels.  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