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   152711篇
  免费   13498篇
  国内免费   4123篇
耳鼻咽喉   964篇
儿科学   3415篇
妇产科学   2316篇
基础医学   26015篇
口腔科学   3607篇
临床医学   9193篇
内科学   24864篇
皮肤病学   2447篇
神经病学   14869篇
特种医学   4086篇
外国民族医学   29篇
外科学   14711篇
综合类   13760篇
现状与发展   17篇
预防医学   7357篇
眼科学   1416篇
药学   23898篇
  43篇
中国医学   5652篇
肿瘤学   11673篇
  2023年   2428篇
  2022年   5369篇
  2021年   6341篇
  2020年   5296篇
  2019年   6695篇
  2018年   6435篇
  2017年   5693篇
  2016年   5102篇
  2015年   5601篇
  2014年   8493篇
  2013年   8775篇
  2012年   7494篇
  2011年   8714篇
  2010年   7046篇
  2009年   7171篇
  2008年   7043篇
  2007年   6092篇
  2006年   5394篇
  2005年   4868篇
  2004年   4110篇
  2003年   3771篇
  2002年   2813篇
  2001年   2473篇
  2000年   2149篇
  1999年   2054篇
  1998年   1862篇
  1997年   1801篇
  1996年   1620篇
  1995年   1511篇
  1994年   1413篇
  1993年   1263篇
  1992年   1038篇
  1991年   922篇
  1990年   796篇
  1989年   705篇
  1988年   658篇
  1987年   672篇
  1986年   733篇
  1985年   1849篇
  1984年   2542篇
  1983年   1685篇
  1982年   1815篇
  1981年   1691篇
  1980年   1453篇
  1979年   1268篇
  1978年   1059篇
  1977年   903篇
  1976年   1012篇
  1975年   692篇
  1973年   652篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.

Background

The ZOE-50 (NCT01165177) and ZOE-70 (NCT01165229) phase 3 clinical trials showed that the adjuvanted recombinant zoster vaccine (RZV) was ≥90% efficacious in preventing herpes zoster in adults. Here we present a comprehensive overview of the safety data from these studies.

Methods

Adults aged ≥50 (ZOE-50) and ≥70 (ZOE-70) years were randomly vaccinated with RZV or placebo. Safety analyses were performed on the pooled total vaccinated cohort, consisting of participants receiving at least one dose of RZV or placebo. Solicited and unsolicited adverse events (AEs) were collected for 7 and 30?days after each vaccination, respectively. Serious AEs (SAEs) were collected from the first vaccination until 12?months post-last dose. Fatal AEs, vaccination-related SAEs, and potential immune-mediated diseases (pIMDs) were collected during the entire study period.

Results

Safety was evaluated in 14,645 RZV and 14,660 placebo recipients. More RZV than placebo recipients reported unsolicited AEs (50.5% versus 32.0%); the difference was driven by transient injection site and solicited systemic reactions that were generally seen in the first week post-vaccination. The occurrence of overall SAEs (RZV: 10.1%; Placebo: 10.4%), fatal AEs (RZV: 4.3%; Placebo: 4.6%), and pIMDs (RZV: 1.2%; Placebo: 1.4%) was balanced between groups. The occurrence of possible exacerbations of pIMDs was rare and similar between groups. Overall, except for the expected local and systemic symptoms, the safety results were comparable between the RZV and Placebo groups irrespective of participant age, gender, or race.

Conclusions

No safety concerns arose, supporting the favorable benefit-risk profile of RZV.  相似文献   
42.
目的:通过3D打印的方法制备的不同重量比例的纳米羟基磷灰石/聚乳酸/聚乙烯醇(n-HA/PLA/PVA)复合膜,并对其相关性能检测。方法:采用3D打印技术制备不同重量比例的n-HA/PLA/PVA复合膜,分别为PLA/PVA复合膜、15%n-HA/PLA/PVA复合膜、50%n-HA/PLA/PVA复合膜、75%n-HA/PLA/PVA复合膜。扫描电镜下观察各组膜形态,对其力学性能、细胞毒性及动物实验相应指标进行检测。结果:扫描电镜下观察,n-HA/PLA/PVA复合膜呈现三维网状结构,各材料间相互结合,孔隙分布不均,大小不一。随着n-HA质量浓度的提高,电镜下见各材料间孔隙逐渐减小,形成结构均匀的复合膜。力学性能及吸水率检测中,随着nHA含量的增加,n-HA/PLA/PVA复合膜的拉伸强度及吸水率呈下降趋势;细胞毒性检测,不同比例复合膜的细胞增殖率无明显差别,无细胞毒性。动物实验测量牙周菌斑指数及龈沟出血指数未发现不同比例n-HA/PLA/PVA复合膜有统计学差异。结论:3D打印不同比例的n-HA/PLA/PVA复合膜具有良好的物理性能和细胞生物相容性,n-HA比例更高的复合膜可能具有更好的物理性能及良好的生物相容性。  相似文献   
43.
44.
Extensive research has indicated that miRNAs are crucial for the occurrence and progression of cancers. miR-451a, involved in breast cancer (BC), is one of the miRNAs. This study focused on the mechanism by which miR-451a regulates BC. The levels of miR-451a in BC tissues and cell lines were examined using quantitative real-time polymerase chain reaction (qRT-PCR). Kaplan‒Meier analysis showed that this was intimately related to the patient's overall survival rate. Functional experiments revealed the negative effects of miR-451a on the abilities of BC cells to multiply (tested by Cell Counting Kit-8), migrate (tested by wound healing assay), and invade (tested by Transwell assay) and its positive effects on apoptosis (tested by flow cytometry). Western blotting indicated that the expression of tumor-related proteins was affected by miR-451a. Moreover, in vivo experiments suggested that tumor growth was clearly restrained by an miR-451a agonist in a xenograft tumor model. Bioinformatic analysis indicated that miR-451a directly targeted Cyclin D2 (CCND2), as demonstrated by the luciferase reporter assay. An opposite change in the level of CCND2 and miR-451a in BC was indicated by qRT-PCR, western blotting, and immunohistochemistry. Subsequently, functional experiments and western blotting analysis confirmed that CCND2 accelerated BC progression, which was regulated by miR-451a. Cumulatively, research on miR-451a may be valuable for BC treatment.  相似文献   
45.
46.
The specific role of postsynaptic activity for the generation of a functional magnetic resonance imaging (fMRI) response was determined by a simultaneous measurement of generated field excitatory postsynaptic potentials (fEPSPs) and blood oxygen level-dependent (BOLD) response in the rat hippocampal CA1 region during electrical stimulation of the contralateral CA3 region. The stimulation electrode was placed either in the left CA3a/b or CA3c, causing the preferentially basal or apical dendrites of the pyramidal cells in the right CA1 to be activated. Consecutive stimulations with low-intensity stimulation trains (i.e., 16 pulses for 8 seconds) resulted in clear postsynaptic responses of CA1 pyramidal cells, but in no significant BOLD responses. In contrast, consecutive high-intensity stimulation trains resulted in stronger postsynaptic responses that came along with minor (during stimulation of the left CA3a/b) or substantial (during stimulation of the left CA3c) spiking activity of the CA1 pyramidal cells, and resulted in the generation of significant BOLD responses in the left and right hippocampus. Correlating the electrophysiologic parameters of CA1 pyramidal cell activity (fEPSP and spiking activity) with the resultant BOLD response revealed no positive correlation. Consequently, postsynaptic activity of pyramidal cells, the most abundant neurons in the CA1, is not directly linked to the measured BOLD response.  相似文献   
47.
ObjectivesVitamin D deficiency is prevalent among older adults. We aimed to study whether residential greenness could alter serum 25(OH)D concentrations as a possible mechanism of residential greenness's positive health effects.DesignA longitudinal cohort study.Setting and ParticipantsWe included older adults aged ≥65 years from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) with follow-up between 2012 and 2014.MethodsWe measured residential greenness by calculating annual average Normalized Difference Vegetation Index (NDVI) in a 500 m radius by using satellite images around each participant's residential address. Serum 25-hydroxyvitamin D (25(OH)D) concentration was dichotomized into 2 categories: nondeficiency (≥50 nmol/L) and deficiency (<50 nmol/L). We used the generalized estimating equation to examine the relationship between annual average NDVI and serum 25(OH)D.ResultsWe included 1336 participants in our analysis. The annual average NDVI was 0.49, and mean serum 25(OH)D was 43 nmol/L at baseline. Each 0.1-unit increase in annual average NDVI was associated with a 13% higher odds of vitamin D nondeficiency [95% confidence interval (CI): 1.01, 1.26]. The association was stronger among men [odds ratio (OR): 1.17, 95% CI: 1.02, 1.35] than women (OR: 1.08, 95% CI: 0.91, 1.29) and also stronger among those who were free of activities of daily living (ADL) disability at baseline (OR: 1.12, 95% CI: 1.00, 1.25). During the follow-up period, the participants who lived in greener areas were more likely to have an improved, rather than stable or deteriorated, vitamin D status (OR: 1.94, 95% CI: 1.51, 2.51).Conclusions and ImplicationsOur study suggests that higher levels of residential greenness are associated with higher serum 25(OH)D concentrations, which has implications for prevention of vitamin D deficiency among older adults.  相似文献   
48.
Helicobacter pylori (H. pylori) is a main risk factor for gastric cancer (GC). Epithelial-mesenchymal transition (EMT) is involved in the development and progression of H. pylori-associated GC. However, the exact molecular mechanism of this process remains unclear. The AKT/GSK3β signaling pathway has been demonstrated to promote EMT in several types of cancer. The present study investigated whether H. pylori infection induced EMT, and promoted the development and metastasis of cancer in the normal gastric mucosa, and whether this process was dependent on AKT activation. The expression levels of the EMT-associated proteins, including E-cadherin and N-cadherin, were determined in 165 gastric mucosal samples of different disease stages by immunohistochemical analysis. The expression levels of E-cadherin, N-cadherin, AKT, phosphorylated (p-)AKT (Ser473), GSK3β and p-GSK3β (Ser9) were further determined in H. pylori-infected Mongolian gerbil gastric tissues and cells co-cultured with H. pylori by immunohistochemical analysis and western blotting. The results indicated that the expression levels of the epithelial marker E-cadherin were decreased, whereas the expression levels of the mesenchymal marker N-cadherin were increased during gastric carcinogenesis. Their expression levels were associated with H. pylori infection. Furthermore, H. pylori infection resulted in downregulation of E-cadherin expression and upregulation of N-cadherin expression in Mongolian gerbils and GES-1 cells. In addition, an investigation of the associated mechanism of action revealed that p-AKT (Ser473) and p-GSK3β (Ser9) were activated in GES-1 cells following co-culture with H. pylori. Furthermore, following pretreatment of the cells with the AKT inhibitor VIII, the expression levels of E-cadherin, N-cadherin, p-AKT and p-GSK3β did not show significant differences between GES-1 cells that were co-cultured with or without H. pylori. The levels of p-AKT and p-GSK3β were increased in H. pylori-infected Mongolian gerbils. In conclusion, the present study demonstrated that H. pylori infection activated AKT and resulted in the phosphorylation and inactivation of GSK3β, which in turn promoted early stage EMT. These effects were AKT-dependent. This mechanism may serve as a prerequisite for GC development.  相似文献   
49.
50.
Mammalian spermatogenesis is a well-organized process of cell development and differentiation. Meiosis expressed gene 1 (MEIG1) plays an essential role in the regulation of spermiogenesis. To explore potential mechanisms of MEIG1''s action, a yeast two-hybrid screen was conducted, and several potential binding partners were identified; one of them was membrane occupation and recognition nexus repeat containing 3 (MORN3). MORN3 mRNA is only abundant in mouse testis. In the testis, Morn3 mRNA is highly expressed in the spermiogenesis stage. Specific anti-MORN3 polyclonal antibody was generated against N-terminus of the full-length MORN3 protein, and MORN3 expression and localization was examined in vitro and in vivo. In transfected Chinese hamster ovary cells, the antibody specifically crossed-reacted the full-length MORN3 protein, and immunofluorescence staining revealed that MORN3 was localized throughout the cytoplasm. Among multiple mouse tissues, about 25 kDa protein, was identified only in the testis. The protein was highly expressed after day 20 of birth. Immunofluorescence staining on mixed testicular cells isolated from adult wild-type mice demonstrated that MORN3 was expressed in the acrosome in germ cells throughout spermiogenesis. The protein was also present in the manchette of elongating spermatids. The total MORN3 expression and acrosome localization were not changed in the Meig 1-deficient mice. However, its expression in manchette was dramatically reduced in the mutant mice. Our studies suggest that MORN3 is another regulator for spermatogenesis, probably together with MEIG1.  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