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   47772篇
  免费   4149篇
  国内免费   1796篇
耳鼻咽喉   298篇
儿科学   927篇
妇产科学   2022篇
基础医学   9991篇
口腔科学   1665篇
临床医学   3901篇
内科学   4927篇
皮肤病学   1250篇
神经病学   2757篇
特种医学   1054篇
外国民族医学   20篇
外科学   3149篇
综合类   7220篇
现状与发展   12篇
一般理论   12篇
预防医学   3774篇
眼科学   940篇
药学   5399篇
  22篇
中国医学   1092篇
肿瘤学   3285篇
  2024年   60篇
  2023年   515篇
  2022年   1069篇
  2021年   1557篇
  2020年   1355篇
  2019年   1422篇
  2018年   1393篇
  2017年   1552篇
  2016年   1645篇
  2015年   1607篇
  2014年   2542篇
  2013年   3495篇
  2012年   2464篇
  2011年   2741篇
  2010年   2357篇
  2009年   2155篇
  2008年   2143篇
  2007年   2274篇
  2006年   2161篇
  2005年   1950篇
  2004年   1817篇
  2003年   1624篇
  2002年   1389篇
  2001年   1205篇
  2000年   1043篇
  1999年   929篇
  1998年   906篇
  1997年   857篇
  1996年   804篇
  1995年   765篇
  1994年   664篇
  1993年   618篇
  1992年   555篇
  1991年   500篇
  1990年   374篇
  1989年   376篇
  1988年   332篇
  1987年   243篇
  1986年   222篇
  1985年   396篇
  1984年   331篇
  1983年   230篇
  1982年   256篇
  1981年   206篇
  1980年   159篇
  1979年   106篇
  1978年   107篇
  1977年   66篇
  1976年   66篇
  1975年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
目的 探讨血清乙型肝炎病毒标志物不同表现模式对肾移植受者长期存活的影响。方法 对 62例血清乙型肝炎病毒标志物阳性者及 1 96例血清乙型肝炎病毒标志物全阴性者肾移植术后的肝功能、人肾均存活的存活率等指标进行随访和回顾性分析。结果 术后早期血清乙型肝炎病毒标志物阳性组与血清乙型肝炎病毒标志物阴性组比较 ,肝功能异常发生率的差异无显著性 (P >0 .0 5) ;术后中远期 ,HBsAg、HBeAg及抗 HBc阳性者的肝功能受损率明显高于血清乙型肝炎病毒标志物阴性组及HBsAg、抗 HBe、抗 HBc阳性者 (P <0 .0 5) ,其人肾均存活的存活率也最低 (P <0 .0 5)。结论 对HBsAg、抗 HBe及抗 HBc阳性者进行肾移植应慎重 ,而HBsAg、HBeAg及抗 HBc阳性者则不适宜接受肾移植  相似文献   
52.
We experienced a case of familial spontaneous pneumothorax in three generations. Six of 13 family members had episodes of spontaneous pneumothorax. It is well established that there are some diseases associated with human leukocyte antigen (HLA). We performed HLA phenotyping for HLA of A, B and C. In our study, we detected the HLA haplotype A2, B61 in three of 4 who had episodes of spontaneous pneumothorax. The HLA haplotype A2, B70 were also detected in three of 4 who had episodes. This suggests that familial spontaneous pneumothorax might have hereditary factors.  相似文献   
53.
用人喉癌手术切除标本建立了裸鼠移植瘤模型,已传至13代。原代移植成功率为66.7%,潜伏期30~70d;鼠间传代移植成功率为100%,潜伏期14~19d,生长稳定。经光学显微镜检查,各代移植瘤组织结构与原人喉癌组织基本一致。电镜检查证明,具有人喉癌特征,癌细胞间有大量桥粒,细胞浆中可见张力原纤维,有的张力原纤维与桥粒相连。细胞表面有较大的指状突,核膜较规则,胞浆中线粒体较多。  相似文献   
54.
Testicular seminoma with elevated serum human chorionic gonadotropin level (hCG-positive seminoma) is regarded as more malignant than marker-negative seminoma, although Its prognosis is still unclear. To clarify the malignant potential of seminoma with hCG production, the serum levels of the beta subunit of hCG (β-hCG) and lactic acid dehydrogenase (LDH) were examined in 35 and 40 patients, respectively, and the Immunohistochemical expression of β-hCG examined in 45 tumors. The elevation of the LDH serum level correlated to the Invasive status, metestatic status and poor outcome, while that of the serum β-hCG level correlated only to the metastatic status. Immunohistochemical expression of β-hCG was observed in syncytiotrophoblastic giant cells in 11 tumors and a few mononuclear seminoma cells In 36 tumors. Expression was not associated with the malignancy potential, except where the expression In mononuclear cells Inversely correlated to the invasive status. These results suggest that most seminomas produce a slight amount of hCG; that an elevated hCG serum level Indicates the pressnce of metastatic tumors and mainly reflects an increase in tumor volume but not in cellular malignancy potential; and that the LDH serum level, rather than hCG, is more useful as a prognostic indicator for patients with seminoma.  相似文献   
55.
Abstract Several lines of evidence implicate protein kinase C (PKC) in the development of basal cell and squamous cell carcinomas, tumors which originate from epidermal keratinocytes. To examine PKC in a model relevant to human skin, we exposed normal human epidermal keratinocytes (NHEK) in serum-free media to a variety of PKC agonists and antagonists. NHEK PKC activity increased up to 10-fold within the 1st hour of exposure to tetradecanoyl phorbol acetate (TPA), and gradually returned to control values within 72 h. TPA-induced PKC activity was enhanced by pretreatment of cultures with protein and RNA synthesis inhibitors. TPA-induced growth arrest and differentiation was antagonized by staurosporine. Down-regulation by bryostatin pretreatment blocked TPA-stimulated differentiation. Our overall conclusion is that activation of PKC in cultured human keratinocytes is required for differentiation. These results are crucial to the analysis of compounds suspected of promoting or inhibiting epidermal tumors.  相似文献   
56.
57.
Isolated sperm from normo-, oligo- and astheno-spermic men were incubated for 20 h in medium supplemented with 8% heat-inactivated or untreated human serum, and in medium with heated or untreated serum deficient in complement factor C3. Before and after incubation, sperm motility was assessed by means of a computer-assisted semen analyser. The results did not show significant differences between the motility of sperm incubated in heated or untreated serum. It is concluded that heating of homologous serum is not necessary for preserving sperm motility and in some cases may even be disadvantageous.  相似文献   
58.
采用扫描电镜、透射电镜及光镜免疫金银法观察了31例慢性扁桃体炎患者和8例胎儿的扁桃体隐窝上皮结构及其中细胞的分布。电镜观察发现隐窝上皮表面存在三种类型微隐窝开口,其腔内有浸润细胞、异物及细菌。有三种特化上皮细胞(M细胞)覆盖于Ⅲ型微隐窝开口处,其结构与肠道M细胞相似,其数量随扁桃体炎的反复发作而减少。形态表明微隐窝是浸润细胞和外来抗原的出入口。M细胞与抗原的摄取及传递有关。光镜免疫金银法观察证明上皮浸润细胞中多数为OKT_s~+细胞,其中OKT_4~+者又占多数而OKT_s~+细胞较少,这些细胞是隐窝上皮参于免疫应答的结构基础。  相似文献   
59.
核酸原位杂交程序中探针和靶基因的加热变性和杂交为整个程序中最重要的环节,目前国内外最常用的方法是在切片上滴加DNA探针溶液后用盖玻片复盖组织,并加胶泥或其他封固剂封闭玻片四周,变性杂交后需拆除盖玻片,这一操作过程易损坏组织切片或出现干片、脱片。作者针对上述情况,对传统的核酸原位杂交方法中的部分程序加以改良,采用不加盖玻片直接在蒸汽中变性方法,经多次实验证明此方法稳定、可靠、简便,结果满意。  相似文献   
60.
Abstract: Lipid peroxidation, measured by malonyldial-dehyde (MDA) and vitamin E in red blood cells (RBC) and plasma, was investigated in 25 hemodialysis (HD) patients before and after 6 months rhEPO therapy. RBC-MDA was significantly elevated, but plasma MDA was in the reference range. After recombinant human erythro-poietin (rhEPO) treatment, the MDA level was significantly decreased in both compartments. Marked vitamin E deficiency was established in RBC as well as in plasma. rhEPO therapy restored vitamin E levels in both compartments. Our data suggest a possible positive rhEPO-antioxidant effect in HD patients.  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