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   25931篇
  免费   1129篇
  国内免费   128篇
耳鼻咽喉   278篇
儿科学   638篇
妇产科学   459篇
基础医学   3540篇
口腔科学   424篇
临床医学   1613篇
内科学   6093篇
皮肤病学   396篇
神经病学   2339篇
特种医学   1021篇
外科学   4019篇
综合类   100篇
一般理论   6篇
预防医学   793篇
眼科学   495篇
药学   1684篇
中国医学   44篇
肿瘤学   3246篇
  2023年   106篇
  2022年   257篇
  2021年   438篇
  2020年   269篇
  2019年   332篇
  2018年   422篇
  2017年   371篇
  2016年   397篇
  2015年   420篇
  2014年   562篇
  2013年   712篇
  2012年   1183篇
  2011年   1302篇
  2010年   740篇
  2009年   669篇
  2008年   1106篇
  2007年   1232篇
  2006年   1222篇
  2005年   1234篇
  2004年   1212篇
  2003年   1202篇
  2002年   1197篇
  2001年   706篇
  2000年   771篇
  1999年   724篇
  1998年   353篇
  1997年   280篇
  1996年   268篇
  1995年   262篇
  1994年   251篇
  1993年   242篇
  1992年   666篇
  1991年   578篇
  1990年   573篇
  1989年   600篇
  1988年   536篇
  1987年   494篇
  1986年   450篇
  1985年   456篇
  1984年   278篇
  1983年   222篇
  1982年   114篇
  1979年   239篇
  1978年   144篇
  1977年   108篇
  1975年   103篇
  1974年   97篇
  1973年   97篇
  1970年   103篇
  1969年   116篇
排序方式: 共有10000条查询结果,搜索用时 30 毫秒
31.
The effect of ethylene glycol on rat hepatic microsomal cytochrome P-450 was studied in vitro and in vivo. The destruction of cytochrome P-450 was not seen in vitro. The addition of 1 mM NADPH also did not change. When ethylene glycol was added to drinking water at a concentration of 1.0% for 7 days, there was no change in the contents of microsomal protein, cytochrome P-450, b5 and heme. While NADPH-cytochrome C reductase activity of the exposed group did not change, NADH-ferricyanide reductase activity increased significantly.  相似文献   
32.
Serum level of sex hormone-binding globulin (SHBG) was measured by immunoradiometric assay in fifty two breast cancer patients and twenty nine healthy female volunteers. The results are as follows: 1) Although the serum SHBG concentration showed no significant difference between the breast cancer group and the healthy control group, the serum SHBG concentration in postmenopause was significantly higher in the breast cancer group (63.8 +/- 31.2nmol/ml/ml; mean +/- S.D.) than in the healthy control group (40.1 +/- 15.4nmol/ml). 2) Subsequently in the postmenopausal breast cancer group, the serum SHBG concentration was significantly higher in the estrogen receptor (ER)-negative cancer group (97.8 +/- 12.7nmol/ml) than in the ER-positive cancer group (55.8 +/- 32.1nol/ml). 3) No significant relationships were showed between the serum SHBG concentration and obesity or serum estradiol concentration in postmenopausal patients. 4) The serum SHBG concentration showed significant decrease 3 months after radical operation for breast cancer in postmenopausal patients. These results suggest the possibility of the SHBG synthesis in breast cancer tissue.  相似文献   
33.
The protective effect of prostaglandins (PGs) against cerebral hypoxia/anoxia was investigated with a variety of experimental models in relation to their CNS depressant effects in mice. Furthermore, the effect of PGs on the changes of cerebral energy metabolites and cyclic nucleotide was examined in hypoxic mice. Mice were given s.c. doses of PGs 30 min before tests. Among the PGs tested, treatment with PGD2, PGE1 and PGI2 Na showed a consistent and dose-dependent protection against cerebral anoxia induced by all models studied: histotoxic anoxia by KCN, hypobaric hypoxia, normobaric hypoxia and decapitation-induced gasping. However, PGA1, PGA2, PGB1, PGB2, PGE2, PGF1 alpha, PGF2 alpha and 6-keto-PGF1 alpha at a dose of 3 mg/kg were without effect against normobaric hypoxia and gasping duration. The three PGs, i.e. PGD2, PGE1 and PGI2 which showed anti-hypoxic effects decreased locomotor activity and potentiated hexobarbital-induced sleep. On the other hand, PGE2, PGA1, PGA2 and PGB2 also caused a decrease in locomotor activity. Similarly, PGE2 and PGA1 caused a potentiation of hexobarbital-induced sleep, but interestingly they did not cause clear-cut increase in cerebral resistance to hypoxia, in contrast with the former three PGs. Thus general depression of CNS function appears not to be responsible for the PGD2-, PGE1- and PGI2-induced increase in cerebral resistance to hypoxia. The levels of Cr-P and ATP were significantly reduced and those of ADP and AMP were markedly elevated in hypoxic brain, resulting in a decrease in a calculated energy charge potential. The lactate level and lactate/pyruvate ratio increased and the glucose level decreased markedly.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
34.
Use of nicardipine in the anesthetic management of pheochromocytoma   总被引:2,自引:0,他引:2  
  相似文献   
35.
A 22-year-old man was urgently admitted for pneumothorax. He continued complaining of exertional dyspnea and dry cough after the pneumothorax healed. About three months later, an atypical pulmonary mycobacteriosis by mycobacterium kansasii was identified. Exertional dyspnea increased after chemotherapy was administered, and the patient was readmitted because of difficulty in daily life activities. Chest radiographs and CT scans showed bilateral pulmonary hyperinflation and a narrowed heart shadow. There was also marked combined ventilatory impairment, as identified by a respiratory function test. Furthermore, the histological findings of surgically removed lung tissue revealed accumulation of lymphocytes in the wall of a small bronchus. Idiopathic bronchiolitis obliterans was diagnosed from the clinical course and clinical findings. The patient is now being monitored and is awaiting lung transplantation.  相似文献   
36.
OBJECTIVE: We investigated modulation of the short- and long-latency somatosensory evoked potentials (SEPs) in a forewarned reaction time task. METHODS: A pair of warning (auditory) and imperative stimuli (somatosensory) was presented with a 2 s interstimulus interval. In movement condition, subjects responded by grip movement with the ipsilateral hand to the somatosensory stimulation when the imperative stimulus was presented. In counting condition, they silently counted the number of imperative stimuli. The SEPs in response to the imperative stimuli were recorded. RESULTS: Frontal N30 and central N60 amplitudes were significantly smaller in the movement than in the counting or rest conditions. None of the short-latency components differed between the counting and rest conditions. In contrast to the short-latency components, P80 was significantly larger in the counting than in the rest condition, and showed a further increase from the counting to the movement condition. The N140 amplitude was significantly larger in the movement than the rest condition, but was not changed between the counting and the rest conditions. CONCLUSIONS: The attenuation of the frontal N30 and central N60, and the enhancement of the P80 and possibly the N140 resulted from the centrifugal mechanism. The present findings may show the different effects of voluntary movement on the early and subsequent cortical processing of the relevant somatosensory information requiring a behavioral response. SIGNIFICANCE: The present study demonstrated the differential modulation of short- and long-latency components of SEPs in a forewarned reaction time task.  相似文献   
37.
The so-called Potter's lesion, previously described as preneoplastic in the lymph nodes of C58 mice, develops frequently in autoimmune NZB mice. These lesions were characterized in the present study by bands or sheets of palestaining histiocytic cells in the cortex and medulla of the lymph node, and multiple small nodules of the same cells were found in the red pulp of the spleen and the liver. Electron microscopically, the cells had pleomorphic cytoplasm with long processes, electron-dense bodies, abundant mitochondria, and a characteristic labyrinth structure with many C-type viruses. Mac-1 antigen, IgG-Fc receptor, ferritin, and ACPase activity were identified on these cells. Intraperitoneally-injected iron colloids were found in the lesions of the spleen and liver but not in those of the lymph nodes. The lymph node lesions appeared when the mice were about 3 months of age and enlarged until the mice were around 10 months old, after which they gradually receded and were replaced by small vessels and fibroblastic cells. These data indicate that the lesions represent reactive hyperplasia of the macrophage system and may have no direct association with the development of malignant lymphoma in NZB mice.  相似文献   
38.
Perforin expression in lymphocytes infiltrated to human colorectal cancer   总被引:4,自引:0,他引:4  
Perforin (PFP) is a cytotoxic protein released from killer cells. PFP immunoreactivity in human peripheral blood lymphocytes (PBL) and tumour infiltrating lymphocytes (TIL) was investigated immunocytochemically with the aid of an anti-PFP monoclonal antibody. PFP was detected in the cytoplasm of 10% of PBL. We performed a double staining of PFP+ cells with Leu11b/CD16, Leu2a/CD8, or Leu3a/CD4 and showed that PFP was produced by 9% of CD8+ cells and 18% of CD16+ cells but not by CD4+ cells. In 28 colorectal cancer tissues, PFP immunoreactivity was observed in the lymphocytes infiltrating to the tumour stroma. The PFP+ cells were most numerous in Dukes A and decreased in number according to the progression of tumours. The PFP+ cells in TIL exhibited the same phenotypes as those in PBL but the PFP+ cells were more numerous in CD8+ cells than in CD16+ cells at all stages. This study represents the first evidence that PFP is mainly secreted from CD8+ cells in tumour tissues. It is hypothesised that the decrease in the number of PFP+ cells in accordance with tumour progression may reflect the suppression of the hosts local immunity.  相似文献   
39.
In ongoing reviews of 339 patients with surgically treated primary squamous cell carcinoma, there were 19 (5.6%) with concurrent gastric cancer and 11 (3.2%) with head and neck cancer. The incidences of intra-esophageal multiple occurrence of esophageal cancer are 27.3% and 26.3% in those with associated head and neck cancer and gastric cancer, respectively, and higher than 7.1% in those without such a concurrent cancer. There was no difference in the clinicopathological characteristics of those with concurrent head and neck and gastric cancers, except for the higher incidence of metachronous occurrence in the former. These findings suggest that, in cases of esophageal cancer associated with concurrent head and neck cancer and gastric cancer, intraesophageal multiplicity of the esophageal carcinoma is frequent and that preoperative serial evaluations is most important to design treatment and estimate the prognosis.  相似文献   
40.
The effects of 2,4-Dichlorophenoxyacetic acid on the growth rate, chemical composition, 14C-2,4-dichlorophenoxyacetic acid and 45Ca2+ uptake by Rhizobium sp. M 4 able to nodulate Arachis hypogaea were determined. Cellular growth was diminished by the presence of 10?3 M 2,4-dichlorophenoxyacetic acid in the medium. Alterations in cellular chemical composition, in 14C-2,4-dichlorophenoxyacetic acid and in 45Ca2+ uptake were found.  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