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   69808篇
  免费   3320篇
  国内免费   481篇
耳鼻咽喉   722篇
儿科学   1569篇
妇产科学   815篇
基础医学   9161篇
口腔科学   1488篇
临床医学   4348篇
内科学   18120篇
皮肤病学   1477篇
神经病学   5196篇
特种医学   2653篇
外科学   12412篇
综合类   282篇
一般理论   9篇
预防医学   1932篇
眼科学   1313篇
药学   4619篇
中国医学   259篇
肿瘤学   7234篇
  2023年   327篇
  2022年   547篇
  2021年   1282篇
  2020年   681篇
  2019年   963篇
  2018年   1293篇
  2017年   1044篇
  2016年   1246篇
  2015年   1326篇
  2014年   1712篇
  2013年   2196篇
  2012年   3515篇
  2011年   3843篇
  2010年   2240篇
  2009年   2036篇
  2008年   3708篇
  2007年   4019篇
  2006年   4039篇
  2005年   4142篇
  2004年   4179篇
  2003年   4194篇
  2002年   4140篇
  2001年   1601篇
  2000年   1610篇
  1999年   1571篇
  1998年   1122篇
  1997年   890篇
  1996年   850篇
  1995年   743篇
  1994年   653篇
  1993年   694篇
  1992年   1044篇
  1991年   972篇
  1990年   883篇
  1989年   930篇
  1988年   850篇
  1987年   761篇
  1986年   667篇
  1985年   658篇
  1984年   480篇
  1983年   394篇
  1982年   247篇
  1981年   254篇
  1980年   229篇
  1979年   337篇
  1978年   281篇
  1977年   232篇
  1974年   188篇
  1973年   200篇
  1972年   197篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
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   
112.
Among the patients with liver cirrhosis (LC) who undergo the operation, the postoperative complications are not infrequent and sometimes prove fatal. The impaired hepatic function, especially the impaired reticuloendothelial system (RES) function, has been claimed to be a possible pathogenic factor for these complications. The present experimental and clinical studies were undertaken to investigate the RES function and the effect of preoperative OK-432 administration as an RES potentiator in LC. The results are as follows: 1) CCl4-induced LC rats were evaluated for RES global phagocytic function, Kupffer cell phagocytic function, plasma opsonic activity and plasma opsonic substances such as fibronectin, C3 and IgG. All parameters except IgG showed significant depression compared to those values in normal rats. However, the administration of OK-432 (0.1 KE/rat, ip) improved all these depressed parameters. The OK-432 administration also significantly improved the survival following panperitonitis in LC rats. 2) Among 18 LC patients with hepatocellular carcinoma undergoing partial hepatectomy, the RES global phagocytic function, plasma opsonic activity and plasma opsonic substances were evaluated. Same as the experimental study, all parameters except IgG were significantly depressed among the LC patients compared to those values in the patients with normal liver. However, the preoperative OK-432 administration (5 KE/day sc for 4 days) significantly improved these parameters and consequently decreased the postoperative complications. These results indicate that the preoperative RES activation by the OK-432 was effective and useful for the prevention of the postoperative complications in the LC patients.  相似文献   
113.
114.
We present a case of a 58-year-old man with diagnosis of lung adenocarcinoma invading the left atrium. He was treated with induction chemoradiotherapy for T4N1M0 disease, showing objective response. Then, a left upper lobectomy with a partial resection of the left atrium was performed without cardiopulmonary bypass. No residual tumor cells existed in the resected specimens, showing pathological complete response. Our case suggests that induction chemoradiotherapy prior to surgery can be an appropriate strategy among carefully selected patients with non-small cell lung cancer invading the left atrium.  相似文献   
115.
We previously reported that the Guardian Bio-Threat Alert (BTA) system could detect (detection limit: about 0.1 μg/ml) staphylococcal enterotoxin B (SEB), botulinum toxins (BTX) A and B, and ricin, with no interference by white-powdered materials or colored matrices. In this study, the capability of the BTA system was further assessed. With 10 min of preheating at 60°C, all toxins could be detected, but with preheating at 80°C, BTX A and B and ricin became undetectable. About 20% SEB could be detected after heating at 80°C, but this detection ability was completely removed after heating at 100°C. The effects of chemicals usually used for decontamination, such as sodium hypochlorite, hydrogen peroxide, formaldehyde, and sodium nitrite, on the detectability of SEB, BTX A, or ricin in the BTA system were also tested. The concentrations giving 50% line intensity for SEB, BTX A, and ricin were 3.1, 11, and 15 μM for sodium hypochlorite and 88, 210, and 60 mM for formaldehyde, respectively. The addition of hydrogen peroxide or sodium nitrite did not decrease the detectability even when used at high concentrations.  相似文献   
116.
We examined a gene polymorphism of a novel Z-disc-related protein, myospryn (cardiomyopathy-associated 5). We focused on one haplotype block associated with a tag single nucleotide polymorphism (SNP) that covered 16 of 27 coding SNPs with linkage disequilibrium (minor allele frequency 0.413). Screening a myospryn polymorphism (K2906N) in a general health check-up of a rural Japanese population revealed an association with cardiac diseases (p=0.0082). In further analysis of the interaction between K2906N and cardiac function in patients, K2906N was associated with the anteroseptal wall thickness of the left ventricle in a recessive model (p=0.0324) and with the ratio of the peak velocity of the early diastolic filling wave to the peak velocity of atrial filling (A/E) (p=0.0278). In an association study based on left ventricular wall thickness, we found a significant difference in the K2906N genotype between controls and patients with cardiac hypertrophy. These results suggest that the K2906N polymorphism could be clinically associated with left ventricular hypertrophy and diastolic dysfunction independent of known parameters. Although the precise mechanism underlying this association remains to be elucidated, treatment with angiotensin II induced an increase in heart myospryn mRNA level in vitro and in vivo. Our results suggest that the polymorphism of myospryn is associated with left ventricular hypertrophy, and an association between a Z-disc protein and cardiac adaptation in response to pressure overload.  相似文献   
117.
Chymase is known to generate angiotensin II in the vascular wall. In this study we investigated a novel role for chymase other than angiotensin II production in vascular proliferation after balloon injury. Chymase promoted the migration of vascular smooth muscle cells in the matrix-coated invasion chambers and activated promatrix metalloproteinase-2 obtained from the culture medium of vascular smooth muscle cells. Two weeks after balloon injury, significant neointimal formation was found in dog carotid arteries. After injury, active matrix metalloproteinase-2 was increased in parallel with the augmentation of chymase activity that was seen in the proliferating region of the vascular wall. The oral administration of NK3201 (1 mg/kg per day), a chymase inhibitor, prevented neointimal formation and significantly suppressed both active matrix metalloproteinase-2 and chymase activities 2 weeks after injury. These results suggest that chymase inhibitors can prevent the development of intimal hyperplasia via the inhibition of matrix metalloproteinase-2 activation in balloon-injured arteries.  相似文献   
118.
Obstructive sleep apnea syndrome (OSAS) is recognized as one of the risk factors of hypertension and cardiovascular disorders. In the current study, we hypothesized that the hypoxic stress and oxidative stress caused by obstructive sleep apnea would increase circulating adrenomedullin (ADM) levels in untreated OSAS patients as compared to an age and body mass index (BMI)-matched control group and an age-matched, but normal-BMI control group. We further hypothesized that nasal continuous positive airway pressure (nCPAP) treatment may decrease OSAS-induced hypoxic stress, oxidative stress and ADM levels. To examine these hypotheses, we measured circulating ADM and reactive oxygen species (ROS) from leukocytes before and after nCPAP therapy in OSAS patients. The circulating levels of ADM and amount of ROS in untreated OSAS patients were significantly greater than those in the controls. No differences in ADM levels were found between the increased-BMI controls and normal-BMI controls. We observed that nCPAP treatment decreased sleep apneas, nocturnal oxyhemoglobin desaturation, the circulating ADM, and ROS production by leukocytes in OSAS patients. The ADM levels were associated with the magnitude of oxyhemoglobin desaturation rather than the number of sleep apneas. These observations suggest that nCPAP therapy could reduce OSAS-induced nocturnal hypoxemia, generation of ROS, and ADM in patients with OSAS.  相似文献   
119.
BACKGROUND: Optimal feeding practice in the first year of life is crucial for the survival and health of infants, and has long-term consequences in later life. However, non-optimal feeding practices exist widely. The present study aims to explore various constraints to optimal feeding practices in the first year of life of infants in urban areas of Beijing, China. METHODS: A cross-sectional study was conducted in urban areas of Beijing from 4 July to 20 August, 1998. Two hundred and fifty-one mothers of infants aged 6-12 months were chosen from six child health centers in three different urban districts in Beijing. A self-administered structured questionnaire was used to collect data regarding feeding practices and potentially related factors. RESULTS: Feeding practice for most of the infants was in accordance with the national and international recommendations. However, the rate of incidence of exclusive breast-feeding at 3 months of age was lower than that recommended by the World Health Organisation (WHO) (55.8%), and the introduction of solid/semisolid food before 4 months of age was found in approximately 19.3% of the infants. Cow's milk was given to 21.2% of infants from 6 months of age as the sole source of milk or as a supplement. Maternal education level (OR = 2.44, 95% CI: 1.42-4.19, P < 0.05), employment (OR = 2.05, 95% CI: 1.13-3.74, P < 0.05) and antenatal nonexclusive breast-feeding plans (OR = 4.10, 95% CI: 2.24-7.50, P < 0.001) were found to be correlated to inappropriate feeding practices. CONCLUSIONS: The feeding practices for most of the urban infants was found to be in accordance with the Chinese government and WHO recommendations; however, non-optimal feeding practices presenting as the early cessation of breast-feeding and the introduction of solid/semisolid foods existed. Information regarding optimal feeding practices should be disseminated to mothers and medical professionals in China, to ensure optimal infant health.  相似文献   
120.
Small bowel transplantation (SBT) is associated with a high incidence of infectious complications because of ischemia/reperfusion (I/R) mucosal injury concomitant with potent immunosuppression. In this study, we evaluated whether the cavitary two-layer method (cTLM) could reduce I/R injury and allow early mucosal restoration, particularly after prolonged preservation and transplantation. Canine heterotopic segmental SBT was performed immediately without preservation (group 1), after 24-h preservation in UW solution (group 2) or by the cTLM (group 3). The graft samples were taken 1 h after reperfusion and on days 1, 4 and 7. We assessed graft mucosa with detailed microscopic and electromicroscopic analyses. In Group 3, histological injury and cell apoptosis after transplantation were significantly alleviated and rapidly recovered to a similar level of group 1. The mucosal restoration was morphologically completed within 4 days. In contrast, in group 2, more pronounced mucosal injury and delayed recovery were noted. Crypt cell proliferation activity was well maintained in groups 1 and 3 throughout the experimental period. Our ultrastructural analysis suggested that mitochondrial integrity achieved by the cTLM was a basal mechanism under the prompt mucosal restoration. The cTLM could reduce I/R injury, facilitate mucosal regeneration and restore the nearly normal structure early after SBT.  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