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   5069篇
  免费   268篇
  国内免费   163篇
耳鼻咽喉   12篇
儿科学   33篇
妇产科学   46篇
基础医学   709篇
口腔科学   39篇
临床医学   302篇
内科学   565篇
皮肤病学   19篇
神经病学   153篇
特种医学   493篇
外科学   1764篇
综合类   344篇
现状与发展   1篇
预防医学   72篇
眼科学   15篇
药学   108篇
  1篇
中国医学   24篇
肿瘤学   800篇
  2024年   11篇
  2023年   116篇
  2022年   252篇
  2021年   282篇
  2020年   214篇
  2019年   226篇
  2018年   219篇
  2017年   164篇
  2016年   151篇
  2015年   204篇
  2014年   311篇
  2013年   360篇
  2012年   198篇
  2011年   205篇
  2010年   186篇
  2009年   215篇
  2008年   268篇
  2007年   251篇
  2006年   243篇
  2005年   194篇
  2004年   198篇
  2003年   136篇
  2002年   131篇
  2001年   141篇
  2000年   82篇
  1999年   93篇
  1998年   87篇
  1997年   59篇
  1996年   46篇
  1995年   33篇
  1994年   31篇
  1993年   36篇
  1992年   28篇
  1991年   13篇
  1990年   13篇
  1989年   10篇
  1988年   10篇
  1987年   13篇
  1986年   7篇
  1985年   16篇
  1984年   6篇
  1983年   6篇
  1982年   6篇
  1981年   4篇
  1980年   5篇
  1979年   2篇
  1978年   6篇
  1977年   4篇
  1976年   3篇
  1975年   4篇
排序方式: 共有5500条查询结果,搜索用时 0 毫秒
71.
椎板钩加压内固定在寰枢椎融合术中的应用   总被引:10,自引:2,他引:10  
目的 评价椎板钩加压内固定治疗寰枢椎不稳的临床效果。方法 对寰枢椎不稳者行C1-2 后路自体髂骨植骨、椎板钩(Apofix及Halifix)内固定术。包括齿状突骨折 6例 ,陈旧性齿突骨折伴横韧带断裂 1例 ,齿突骨折骨不连结 1例。术后颈椎X线片检查。结果 随访 3个月~ 5年 ,8例均获得骨性愈合。结论 对寰枢椎不稳可采用寰枢椎后路融合椎板钩内固定术治疗 ,椎板钩内固定术无需椎板下穿越钢丝 ,避免了钢丝断裂及松脱。而术前解剖复位是手术成功的主要措施。  相似文献   
72.
4种不同后路枕颈内固定方式的生物力学研究   总被引:1,自引:0,他引:1  
目的 评价4种不同后路枕颈内固定方式的生物力学稳定性.方法 选择6例新鲜尸体枕颈部标本,在标本完整状态(NS)、枕寰枢失稳模型(DS)、后路枕骨螺钉 C2椎弓根钉固定 纵棒固定(AF)、后路枕骨螺钉 C2椎弓根钉 C3侧块螺钉 纵棒固定(BF)、后路枕骨螺钉 C2椎弓根钉固定 C3椎板钩 纵棒固定(CF)、后路枕骨螺钉 C3椎板钩 C4椎板钩 纵棒固定(DF),共6种状态下,依次用KD-1型三维运动实验机进行测量相应节段的运动参数,并进行统计学分析.结果 1.齿状突及横韧带切除后,枕颈部会严重失稳,即DS组运动范围(ROM)较NS组明显增大10-12 %,具有显著性差异(P<0.05).2.枕颈失稳后,AF组ROM明显比DS组减小13-16 %(P<0.05),与NS组仅相差5-6 %(P>0.05).3.BF组ROM比失稳减小17-19 %(P<0.05),更加有效抑制了枕颈部失稳.4.CF组ROM比DS组减小18-23 %(P<0.05),亦有效抑制了枕颈部失稳.5.DF组ROM比DS组减小19-23 %(P<0.05),也能有效抑制了枕颈部失稳,但椎板钩有滑动现象,相邻节段代偿运动加大.结论 枕颈融合固定时,C2椎体骨质良好者,单纯C2椎弓根固定已足够稳定;在颈椎有C2椎弓根固定再加上C3侧块螺钉或C3椎板钩时,固定更坚强可靠,但多牺牲了一个椎体的活动度;颈椎以C3椎板钩 C4椎板钩固定时,也能达到可靠的枕颈固定,但有侧方滑动的趋势,同时固定的节段最长,邻近节段退变会加剧.  相似文献   
73.
目的 探讨遗传性非息肉病性结直肠癌(HNPCC)腺瘤及癌组织中环氧合酶2(COX-2)的表达及其与错配修复(MMR)基因蛋白表达、微卫星不稳定(MSI)之间的关系.方法 来源于33个HNPCC家系的大肠腺瘤28例、大肠癌14例,随机留取经病理确诊的32例散发大肠腺瘤和24例散发大肠癌标本作为对照;采用免疫组织化学和PCR技术,检测腺瘤及癌组织中COX-2、MMR基因(hMLH1、hMSH2、hMSH6)蛋白表达及BAT-25、BAT-26、D2S123、D5S346、D17S250 5个微卫星位点的MSI状态.结果 COX-2在HNPCC腺瘤及癌组织中高表达率分别为53.6%(15/28)、42.9%(6/14),在散发大肠腺瘤和大肠癌中高表达率分别为62.5%(20/32)、91.7%(22/24),HNPCC癌组织中的COX-2表达明显低于散发大肠癌(P<0.05).HNPCC大肠癌中MMR蛋白表达缺失率、高度微卫星不稳定(MSI-H)发生率[均为71.4%(10/14)]明显高于散发大肠癌[均为12.5%(3/24),均P<0.05].10例MMR蛋白表达缺失的HNPCC大肠癌中,8例为COX-2低表达;4例MMR蛋白表达阳性的HNPCC大肠癌全部为COX-2高表达.在MMR表达缺失的HNPCC大肠癌、HNPCC腺瘤、散发大肠癌中COX-2的表达均显著少于MMR表达阳性者(均P<0.05).MSI-H的HNPCC大肠癌、HNPCC大肠腺瘤、散发大肠癌中COX-2低表达率分别为80.0%(8/10)、66.7%(12/18)、66.7%(2/3);与微卫星稳定(MSS)组比较差异均有统计学意义(均P<0.05).结论 与散发性大肠癌相比,COX-2在HNPCC大肠癌组织中表达明显减少;COX-2在大肠腺瘤及癌组织中的表达率与MMR蛋白表达缺失和MSI-H呈明显的负相关;COX-2、MMR蛋白表达、MSI的检测对于进一步研究大肠肿瘤的发病途径及干预治疗具有重要意义.  相似文献   
74.
75.
Chromosomal and microsatellite instability in sporadic gastric cancer   总被引:5,自引:0,他引:5  
BACKGROUND: Gastric cancer can progress through two pathways of genomic instability: chromosomal (CIN) and microsatellite instability (MSI). It is hypothesized that these two pathways are not always independent and that some tumors show overlap between these two mechanisms. METHODS: A total of 98 sporadic gastric cancers were classified based on their MSI status, using microsatellite assay with BAT26. Evidence for CIN was investigated by identifying loss of heterozygosity (LOH) events on chromosome arms, 5q, 10p, 17p, 17q, and 18q, which are regions harboring tumor suppressor genes that are significant in gastric cancer development. RESULTS: Twelve tumors (12%) showed high-frequency MSI (MSI-H). Overall, 43 of the tumors (44%) had at least one LOH event, with most frequent chromosomal losses observed on 10p and 18q (30%, respectively), followed by 5q (21%), 17p (14%), and 17q (12%). Interestingly, overlap was observed between CIN and MSI pathways. Of 43 cancers with LOH events, four (9%) were also MSI-H. It was also found that 48% of cancers without MSI-H had no LOH events identified, comprising a subgroup of tumors that were not representative of either of these two pathways of genomic instability. CONCLUSION: These results suggest that molecular mechanisms of genomic instability are not necessarily independent and may not be fully defined by either the MSI or CIN pathways in sporadic gastric cancers.  相似文献   
76.
BACKGROUND & AIMS: Human liver cancer can be divided into 2 categories that are characterized by activation of beta-catenin and genomic instability. Here we investigate whether similar categories exist among 5 transgenic models of liver cancer, including c-myc, transforming growth factor-alpha, E2F-1, c-myc/transforming growth factor-alpha, and c-myc/E2F-1 mice. METHODS: The random amplified polymorphic DNA method was used to assess the overall genomic instability, and chromosomal loci affected by genomic alterations were determined by microsatellite analysis. beta-Catenin mutations and deletions were analyzed by polymerase chain reaction and sequencing screening. Cellular localization of beta-catenin and expression of alpha-fetoprotein, a prognostic marker of hepatocellular carcinoma, were investigated by immunohistochemistry. RESULTS: Liver tumors from the transgenic mice could be divided into 2 broad categories characterized by extensive genomic instability (exemplified by the c-myc/transforming growth factor-alpha mouse) and activation of beta-catenin (exemplified by the c-myc/E2F-1 mouse). The c-myc/transforming growth factor-alpha tumors displayed extensive genomic instability with recurrent loss of heterozygosity at chromosomes 1, 2, 4, 6, 7, 9, 12, 14, and X and a low rate of beta-catenin activation. The genomic instability was evident from the early dysplastic stage and occurred concomitantly with increased expression of alpha-fetoprotein. The c-myc/E2F-1 tumors were characterized by a high frequency of beta-catenin activation in the presence of a relatively stable genome and low alpha-fetoprotein levels. CONCLUSIONS: We have identified 2 prototype experimental models, i.e., c-myc/transforming growth factor-alpha and c-myc/E2F-1 mice, for the 2 categories of human hepatocellular carcinoma characterized by genomic instability and beta-catenin activation, respectively. These mouse models will assist in the elucidation of the molecular basis of human hepatocellular carcinoma.  相似文献   
77.
Patients with long-standing inflammatory bowel disease (IBD) have an increased risk of developing colorectal cancer (CRC). Many of the molecular alterations responsible for sporadic colorectal cancer, namely chromosomal instability, microsatellite instability, and hypermethylation, also play a role in colitis-associated colon carcinogenesis. Colon cancer risk in inflammatory bowel disease increases with longer duration of colitis, greater anatomic extent of colitis, the presence of primary sclerosing cholangitis, family history of CRC and degree of inflammation of the bowel. Chemoprevention includes aminosalicylates, ursodeox, ycholic acid, and possibly folic acid and statins. To reduce CRC mortality in IBD, colonoscopic surveillance with random biopsies remains the major way to detect early mucosal dysplasia. When dysplasia is confirmed, proctocolectomy is considered for these patients. Patients with small intestinal Crohn's disease are at increased risk of small bowel adenocarcinoma. Ulcerative colitis patients with total proctocolectomy and ileal pouch anal- anastomosis have a rather low risk of dysplasia in the ileal pouch, but the anal transition zone should be monitored periodically. Other extra intestinal cancers, such as hepatobiliary and hematopoietic cancer, have shown variable incidence rates. New endoscopic and molecular screening approaches may further refine our current surveillance guidelines and our understanding of the natural history of dysplasia.  相似文献   
78.
79.
80.
Purpose: To report the immediate and prolonged (one week) effects of elastic bandage (EB) on balance control in subjects with chronic ankle instability.

Material and methods: Twenty-eight individuals successfully completed the study protocol, of whom 14 were randomly assigned to the EB group (7 men, 7 women) and 14 were assigned to the non-standardised tape (NST) group (9 men, 5 women). To objectively measure postural sway we used computerised dynamic posturography (CDP) with sensory organisation test (SOT) and unilateral stance (US) test. We analysed the following SOT parameters: the composite SOT score, the composite SOT strategy and the SOT condition 2 and its strategy. In addition, we studied the centre of gravity (COG) sway velocity with open eyes and close eyes during the US test.

Results: Repeated measures ANOVA showed a significant effect for time in composite SOT score (F=?34.98; p=?<0.01), composite SOT strategy (F=?12.082; p=?0.02), and COG sway with open eyes (F=?3.382; p=?0.039) in EB group and NST group. Therefore, there were improvements in balance control after bandage applications (defined as better scores in SOT parameters and decreased COG sway in US test). However, no differences between groups were observed in the most relevant parameters.

Conclusions: This study did not observe differences between EB and NST during the follow-up in the majority of measurements. Several outcome measures for SOT and US tests improved in both groups immediately after bandage applications and after one week of use. EB of the ankle joint has no advantage as compared to the non-standardised tape.
  • Implications for rehabilitation
  • Elastic bandage (EB) of the ankle joint has no advantage as compared to the non-standardised tape.

  • The effects of the bandages could be due to a greater subjective sense of security.

  • It is important to be prudent with the use of bandage, since a greater sense of safety could also bring with it a greater risk of injury.

  • The application of the bandage on subjects with chronic ankle instability (CAI) should be prolonged and used alongside other physiotherapy treatments.

  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