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   424044篇
  免费   39950篇
  国内免费   28499篇
耳鼻咽喉   3262篇
儿科学   5609篇
妇产科学   5088篇
基础医学   46619篇
口腔科学   7022篇
临床医学   58602篇
内科学   58621篇
皮肤病学   4732篇
神经病学   20477篇
特种医学   15843篇
外国民族医学   247篇
外科学   39247篇
综合类   77426篇
现状与发展   97篇
一般理论   47篇
预防医学   30920篇
眼科学   11923篇
药学   46040篇
  477篇
中国医学   26922篇
肿瘤学   33272篇
  2024年   1399篇
  2023年   6047篇
  2022年   15845篇
  2021年   20253篇
  2020年   15872篇
  2019年   13032篇
  2018年   13727篇
  2017年   13099篇
  2016年   12146篇
  2015年   18655篇
  2014年   23334篇
  2013年   21601篇
  2012年   31969篇
  2011年   35668篇
  2010年   24001篇
  2009年   19600篇
  2008年   24221篇
  2007年   24076篇
  2006年   22899篇
  2005年   21738篇
  2004年   14769篇
  2003年   14157篇
  2002年   11774篇
  2001年   10024篇
  2000年   9744篇
  1999年   9682篇
  1998年   5995篇
  1997年   5755篇
  1996年   4496篇
  1995年   4185篇
  1994年   3542篇
  1993年   2298篇
  1992年   2884篇
  1991年   2505篇
  1990年   2137篇
  1989年   1876篇
  1988年   1539篇
  1987年   1426篇
  1986年   1139篇
  1985年   824篇
  1984年   478篇
  1983年   352篇
  1982年   199篇
  1981年   236篇
  1980年   153篇
  1979年   214篇
  1978年   110篇
  1977年   80篇
  1974年   78篇
  1972年   78篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Programmed death ligand 1(PD-L1) mediated immune escape play important roles in the development of cancer. The gene polymorphism of PD-L1, in particular rs4143815 C?>?G, has been associated with the cancer risks, but with conflicting results. Therefore, this meta-analysis was aimed to assess the association between rs4143815 C?>?G and cancer susceptibility. A systematic literature search was performed to select the studies and the pooled odds ratio (OR) with 95% confidence interval (CI) was used to evaluate the strength of association. Eleven eligible studies containing 3711 cases and 3704 controls were enrolled in the meta-analysis. The results suggested that there is a strong association between rs4143815 C?>?G and the cancer risks (G vs. C: OR?=?1.386, 95% CI: 1.132–1.696, p?=?0.002; GG vs. CG?+?CC: OR?=?1.843 95% CI: 1.300–2.613, p?=?0.002; GG?+?CG vs. CC: OR?=?1.280, 95% CI: 1.040–1.576, p?=?0.020). Subgroup analysis based on cancer type suggested that PD-L1 rs4143815 C?>?G might increase the susceptibility to gastric cancer (G vs. C: OR?=?1.842, 95% CI: 1.403–2.418, p?<?0.001) and bladder cancer (G vs. C: OR?=?2.015, 95% CI: 1.556–2.608, p?<?0.001), and genotype GG carriers of PD-L1 rs4143815 C?>?G might have higher risks of HCC (GG vs. CG?+?CC: OR?=?2.226 95% CI: 1.562–3.172, p?<?0.001). PD-L1 rs4143815 C?>?G might confer an increased cancer risk, indicating this SNP may contribute to the pathogenesis of cancer and might be used as a potential biomarker to predict the susceptibility to cancer.  相似文献   
92.
93.
94.
目的采用图像融合技术获得T2WI与T2WI-FS的融合图像,评估其在肛瘘及肛周结构显示中的优势。 方法2016年6月至2018年6月,前瞻性选择中山大学附属第一医院29例肛瘘患者进行肛管磁共振(MR)检查,采用图像融合技术获取T2WI与T2WI-FS的融合图像T2WI-Fusion,利用Fisher score算法计算瘘管及肛门括约肌的组织间分辨力Fisher值、脂肪与肛门括约肌间的Fisher值,评估融合图像中瘘管及肛周结构的显示情况。采用改进的双刺激连续质量量表(DSCQS)对T2WI-FS、T2WI、增强3D-VIBE和T2WI-Fusion序列图像进行主观图像质量评价。 结果29例患者均成功获得T2WI与T2WI-FS的融合图像T2WI-Fusion。T2WI-Fusion、T2WI瘘管与括约肌间Fisher均值分别为6.46、3.31,T2WI-Fusion图像对瘘管的显示优于T2WI序列图像(P<0.001)。T2WI-Fusion、T2WI-FS脂肪与括约肌间Fisher均值分别为10.61、2.45,T2WI-Fusion图像对括约肌的显示优于T2WI-FS序列图像(P<0.001)。T2WI-Fusion对瘘管与括约肌的图像质量评价总评分均高于T2WI-FS、T2WI、增强3D-VIBE序列(P<0.001)。 结论MRI图像融合技术同时具备T2WI及T2WI-FS的优势,无需增加扫描序列及扫描时间,且操作简单,花费时间短,显著提高病变及肛周解剖结构的对比度和图像质量。  相似文献   
95.
First described in 1955 in New Jersey, epizootic haemorrhagic disease (EHD) causes a severe clinical disease in wild and domestic ruminants worldwide. Epizootic haemorrhagic disease outbreaks occur in deer populations each year from summer to late autumn. The etiological agent is EHD virus (EHDV) which is a double‐stranded segmented icosahedral RNA virus. EHD virus utilizes point mutations and reassortment strategies to maintain viral fitness during infection. In 2018, EHDV serotype 2 was predominantly detected in deer in Illinois. Whole genome sequencing was conducted for two 2018 EHDV2 isolates (IL41747 and IL42218) and the sequence analyses indicated that IL42218 was a reassortant between different serotypes whereas IL41747 was a genetically stable strain. Our data suggest that multiple strains contribute to outbreaks each year.  相似文献   
96.
文章回顾中医体质研究40年来在6大理论创新、3大技术创新、4大转化应用、2大学术平台方面取得的辉煌成就。展望未来,中医体质研究将积极策应国家需求,进一步发挥其原创优势、深化理论研究、完善技术方法、加快平台建设、提升服务能力,为实施“健康中国”战略作贡献。  相似文献   
97.
Two new 11-methoxyl substituted triterpenoids, named as mimengosides J (1) and K (2), along with seven known compounds, were isolated from the fruits of Buddleja lindleyana. Their structures were elucidated on the basis of spectroscopic analysis. In addition, the new ones were evaluated for protective effects against damage of SH-SY5Y cells induced by 1-methyl-4-phenylpyridinium ion (MPP+) and the results indicated that those may be one of the candidate compositions of Buddleja lindleyana for the treatment of neurodegenerative disease.

  相似文献   

98.
99.
ObjectiveTo investigate the feasibility of transnasal heated humidified high flow nasal cannula oxygen therapy (HFNC) in the treatment of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) with respiratory failure in elderly patients. MethodsA total of 176 elderly patients with AECOPD complicated with respiratory failure who were hospitalized at Peking University Shougang Hospital from December 2016 to January 2022 were enrolled, including 82 patients in an HFNC group and 94 patients in an NPPV group. After treatment, pulse oxygen saturation (SPO2), arterial partial pressure of carbon dioxide (PaCO2), oxygenation index (OI), respiratory rate (RR), heart rate (HR), mean arterial pressure (MAP), comfort score, discharge rate, rate of endotracheal intubation, rate of transfer to intensive care unit (ICU), and mortality were compared between the two groups. The independent sample t-test was used for comparison between the two groups. Statistical data are expressed in percentage or number of cases and the χ2 test was used for their comparisons. ResultsThe SPO2 values at 30 min, 1 h, and 6 h were significantly higher in the HFNC group than in the NPPV group (t=-2.049,-2.618, and -3.314, P=0.043, 0.010, and 0.001, respectively). SPO2 before discharge was significantly lower than that of the NPPV group (t=2.162, P=0.033), but OI at each time point and before discharge had no statistical significance (P>0.05). MAP at 6 h was significantly higher in the HFNC group than in the NPPV group (t=-2.209, P=0.029), but within the normal range. HRs at 2 h and 3 h in the HFNC group were significantly higher than those of the NPPV group (t=-2.199 and -2.336, P=0.030 and 0.021, respectively). There were no significant differences in RR, HR, or MAP between the two groups at other time points and before discharge (P>0.05). There was no significant difference in PaCO2 between the two groups (P>0.05). Comfort score in the HFNC group was significantly higher than that of the NPPV group (t=-46.807, P<0.001). There were no significant differences in discharge rate, ICU transfer rate, endotracheal intubation rate, and mortality between the two groups (P>0.05). ConclusionHFNC is as effective as NPPV in treating elderly patients with AECOPD complicated with type Ⅰ or mild type Ⅱ respiratory failure, and HFNC is more comfortable than NPPV.  相似文献   
100.
目的对比不同术式对肝内胆管结石再次手术效果,探讨肝段或肝叶切除术的优势。 方法回顾性分析2011年8月至2014年8月收治的79例肝内胆管结石再次手术患者资料,依据术式不同分为肝段(叶)切除术组(甲组,n=38)和非肝段(叶)切除术组(乙组,n=41)两组。应用SPSS 19.0软件对所有临床数据进行统计学分析,手术相关指标等以( ±s)的形式表示,组间比较采用独立t检验;术后并发症发生情况及预后情况等计数资料以例(%)的形式表示,采用χ2检验;P<0.05差异有统计学意义。 结果两组患者术中出血量、手术时间及术后住院时间相比,差异无统计学意义(P>0.05);甲组患者的术后并发症发生率5.3%(2/38)显著低于乙组22.0%(9/41)(P<0.05);甲组残留结石发生率、症状复发率2.6%(1/38)、 0(0/41)均显著低于乙组17.1%(7/41)、 12.2%(5/41)(P<0.05),差异有统计学意义(P<0.05);但两组患者的病死率2.6%(1/38)和0(0/41)相比,差异无统计学意义(P>0.05)。 结论肝段(叶)切除术能够有效改善肝内胆管结石再次手术效果,值得推广。  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