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   23989篇
  免费   1579篇
  国内免费   938篇
耳鼻咽喉   131篇
儿科学   329篇
妇产科学   429篇
基础医学   5360篇
口腔科学   303篇
临床医学   2292篇
内科学   4189篇
皮肤病学   450篇
神经病学   576篇
特种医学   416篇
外国民族医学   9篇
外科学   2686篇
综合类   3562篇
现状与发展   8篇
预防医学   1237篇
眼科学   201篇
药学   1165篇
  3篇
中国医学   225篇
肿瘤学   2935篇
  2024年   25篇
  2023年   326篇
  2022年   523篇
  2021年   773篇
  2020年   623篇
  2019年   605篇
  2018年   643篇
  2017年   615篇
  2016年   621篇
  2015年   682篇
  2014年   1119篇
  2013年   1204篇
  2012年   1026篇
  2011年   1305篇
  2010年   1041篇
  2009年   1071篇
  2008年   1143篇
  2007年   1292篇
  2006年   1150篇
  2005年   1129篇
  2004年   985篇
  2003年   839篇
  2002年   863篇
  2001年   780篇
  2000年   668篇
  1999年   598篇
  1998年   577篇
  1997年   550篇
  1996年   468篇
  1995年   363篇
  1994年   410篇
  1993年   355篇
  1992年   261篇
  1991年   226篇
  1990年   266篇
  1989年   168篇
  1988年   170篇
  1987年   123篇
  1986年   111篇
  1985年   196篇
  1984年   134篇
  1983年   97篇
  1982年   85篇
  1981年   80篇
  1980年   62篇
  1979年   49篇
  1978年   35篇
  1977年   24篇
  1976年   24篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Since cyclosporin A (CsA), a widely used immunosuppressive drug, strongly suppresses interleukin-2 (IL-2) secretion, it is frequently difficult to estimate T lymphocyte activation in early acute rejection. We found that, when evaluated based on HLA-DQ antigen expression, monocyte activation in the peripheral blood of renal transplantation patients was a very sharp parameter in diagosing acute rejection. All of 16 episodes of early acute rejection, which were relatively easily suppressed by steroid pulse therapy, showed a sharp increase in the proportion of HLA-DQ antigen-positive monocytes (DQ+ mono) and a quick return of DQ+ mono to previous values, along with a fall in serum creatinine levels. Since, however, HLA-DR antigen-positive T lymphocytes (DR +T) were markedly increased over a long period in episodes of therapy-resistant and chronic rejection, their prolonged high value was regarded as a parameter indicative of poor prognosis.  相似文献   
42.
43.
Between 10% and 25% of patients with newly diagnosed prostate cancer without bone metastases at the time of diagnosis will develop metastases during follow-up. To determine the value of clinical and biochemical parameters for assessment of prognosis at the time of diagnosis, a retrospective study was performed in 124 consecutive patients with newly diagnosed prostate cancer without bone metastases. The mean follow-up was 41 months, during which time 36 patients died and 15 patients developed metastases. Bone scans were classified from 0 (=normal) through 2 (=abnormal, but not typical for metastases) and were correlated with age, alkaline phosphatase (AP), prostate-specific antigen (PSA), tumour grade, T-stage and N-stage. In patients with a class 2 scan, additional roentgenograms and follow-up were used to exclude metastases at initial stage. All parameters, including therapy, were finally correlated with the development of metastases and survival. For survival 38 patients with proven metastases were used as controls. For all parameters tested, no statistically significant differences were found between the three bone scan classifications. The interval between diagnosis and the development of metastases ranged from 12 to 72 months. For the risk of development of metastases only PSA was found to be a significant correlate (P=0.0075). However, when tumour stages were clustered in limited disease (T0–2) and extensive disease (T3–4), the incidence of metastases was significantly higher in patients with extensive disease than in those with limited disease (P=0.0021). Finally, age, PSA and Anderson classification were found to be significant correlates of survival, but in stepwise analysis PSA was selected as the most prognostic variable (P<0.0001). In contrast with a typical pattern of metastases on bone scintigraphy, an abnormal scan (class 1 and 2) at the time of diagnosis is not a poor prognostic parameter of the risk of death. In conclusion, in patients with prostate cancer without bone metastases at the time of diagnosis, pretreatment PSA and tumour stage can be used for the assessment of risk of development of metastases during follow-up and survival. For this purpose, tumour stage should be clustered in limited and extensive disease. Received 14 April and in revised form 9 June 1997  相似文献   
44.
目的:研究肺癌放射导向手术中肿瘤及正常组织P糖蛋白(P-gp)、Ki-67抗原表达与放射性核素摄取比(T/NT)的关系.方法:采用免疫组化方法和显微图像分析技术,测定32例接受放射导向手术的肺癌病人P-gp和Ki-67抗原表达,分析P-gp和Ki-67的标记指数(LI)与T/NT之间的相关性.结果:P-gp和Ki-67的LI和肺癌病人T/NT之间均有相关性(r=-0.61,P=0.0002; r=0.75,P=0.0001).结论:Ki-67的LI越高(肿瘤增殖越旺盛),T/NT值越高;P-gp阳性的肿瘤,T/NT值较低.  相似文献   
45.
BACKGROUND: Recent hospital and cancer registry data show increasing prostate cancer incidence in Nigeria, which was previously regarded as a low incidence region. This study investigates the prevalence of prostate cancer risk in a previously unscreened cohort of rural Nigerians. METHODS: Rural Nigerian men, 40 years and older, were screened by serum prostate-specific antigen (PSA) and digital rectal examination (DRE) and those with PSA >/= 4 ng/mL and/or abnormal DRE were referred for prostate biopsy. RESULTS: Of 200 consecutive men invited, 151 (75.5%) presented for screening, the mean age was 56.45 + 15.1 and 95 (61.6%) were >/= 50 years of age. Of the 140 who consented to a blood test, PSA correlated with age (r = 0.3, P < 0.01), 14 (10.0%) had abnormal PSA >/= 4 ng/mL, increasing from 3 (3.6%) in men < 60 years to 4 (50%) in men >/= 80 years. The rate was 13 (15.7%) for men >/= 50 years and there was no evidence of increased incidence of prostatitis in the community. Mean (median) PSA in ng/mL increased from 1.17 (0.60) in the youngest to 13.75 (4.45) in the oldest cohort. Of those who accepted DRE, 38 (29.0%) had an enlarged prostate, including two who had nodular prostate, one-third with symptoms, increasing from 4 (5.4%) in those < 50 years to 6 (75.0%) in men >/= 80 years. The proportion of men with PSA >/= 4 ng/mL among those with enlarged vs normal prostate is 27.0 to 3.4%, P < 0.001, and the pattern was similar for men >/= 60 years and those < 60 years of age. The 40 (32.0%) men referred for prostate biopsy defaulted mainly because they did not fully understand the need for further investigation because they were symptom free or afraid of the possible side-effects of the procedure or diagnosis of cancer. CONCLUSION: The proportion of men with PSA >/= 4 ng/mL is comparable to that of previously unscreened populations with high incidence of prostate cancer such as African-American men. A larger study is required to confirm these findings and intensify efforts to determine the prostate cancer detection rate by biopsy in this population. A prostate cancer awareness and education campaign will be useful in this community.  相似文献   
46.
目的 探讨前列腺特异抗原(PSA)和高分子量细胞角蛋白(CK34βE12)改良免疫组织化学染色法对前列腺癌鉴别诊断的作用。方法 对52例疑难病例采用改良免疫组织化学染色法检查。即在同一切片的一侧贴附可靠的阳性对照组织,应用微波处理,尽可能保存和修复抗原,在显微镜下严格控制显色等方法以达到最佳染色效果。结果3例前列腺不典型腺瘤样增生(AAH)、37例前列腺上皮内瘤(PIN)高表达PSA与CK34βE12;3例前列腺导管内癌也表达PSA及CK34βE12;9例前列腺腺癌仅表达PSA无CK34βE12表达;10例膀胱移行上皮癌均不表达PSA与CK34βE12。结论 PSA和CK34βE12的改良免疫染色可以作为前列腺癌鉴别诊断的工具之一,对指导临床治疗可发挥重要作用。  相似文献   
47.
目的:采用巢式RT-PCR方法,检测前列腺癌合并骨转移的患者外周血中前列腺特异抗原(PSA)、前列腺特异膜抗原(PSMA)和人腺体激肽释放酶mRNA的表达,探讨其临床意义.方法:应用巢式RT-PCR的方法,检测外周血中PSA、PSMA和hK2mRNA表达.结果:巢式PCR能够检测到经淋巴细胞稀释的LNCaP细胞的PSA、PSM和hK2mRNA的灵敏度,稀释浓度分别为10-6、10-6及10-7.检测初发伴骨转移的前列腺癌患者外周血PSA、PSMA和hK2mRNA的阳性率分别为59.45%、51.35%、59.46%,其中三种检测同时阳性的为32.43%;检测接受内分泌治疗后出现骨转移的前列腺癌患者的阳性率分别为57.14%、85.71%、83.33%,其中三种检测同时阳性的为52.48%.局限性前列腺癌患者、健康男性及健康女性的检测结果均为阴性.以β-actin mRNA做为内参照,所有临床标本检测均为阳性.结论:采用巢式RT-PCR检测前列腺癌患者外周血PSMA、hK2和PSA mRNA有助于发现进入循环系统的前列腺癌细胞,提示隐匿性转移的存在.PSMA和hK2较适合用于内分泌治疗后患者的检测.三种指标联合检测有助于提高敏感性.  相似文献   
48.
Splenic T cells from myelin basic protein (MBP)-immunised Lewis rats were activated to transfer experimental autoimmune encephalomyelitis (EAE) by co-culture with MBP-pulsed lymphoid dendritic cells (DC). MBP-pulsed DC could be kept for at least 24 h at 37 degrees C in antigen-free medium without affecting their ability subsequently to activate encephalitogenic T cells. However, MBP-pulsed DC were rendered much less stimulatory after a 6 h, but not 2 h, secondary incubation with ovalbumin. Thus, although encephalitogenic complexes between MBP and DC appear very stable in the absence of competing antigens, in their presence, antigen exchange can take place over a period of a few hours; this has positive implications for therapy of EAE by antigen competition.  相似文献   
49.
血清TPS浓度在消化道肿瘤中价值的研究   总被引:4,自引:0,他引:4  
共选择30例消化道肿瘤病人,其中食管癌,胃癌,大肠癌各10例,设健康献血者30例,对两组血清特异型组织多肽抗原浓度进行了检测,结果肿瘤组血清TPS浓度明显高于健康人。消化道肿瘤阳性检出经达70%,其中食管癌80%,胃癌60%,大肠癌70%。消化道肿瘤合并淋巴转移阳性检出率达76.9%,其中食管癌100%,胃癌66.7%,大肠癌70.0%。随着病程发展,血清TPS浓度呈现升高趋势。  相似文献   
50.
人抗HBsAg噬菌体抗体Fab段基因的序列分析及表达   总被引:3,自引:0,他引:3  
对已建的噬菌体抗体库分离出来的人抗-HBs克隆进行了序列分析和表达研究,发现4个克隆中3个克隆的重链和轻链完全相同,DNA序列分析表明VH分别属于VH1亚群和Ⅱ亚群,其轻链VL分别属于VλⅡ亚群和VλⅠ亚群。构建了可溶性Fab段表达载体,显示出在细菌中表达的Fab段抗体与HBsAg特异性结合,这说明所筛选出来的噬菌体抗体具有HBdisplay status  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