全文获取类型
收费全文 | 219649篇 |
免费 | 20566篇 |
国内免费 | 15419篇 |
专业分类
耳鼻咽喉 | 1901篇 |
儿科学 | 2190篇 |
妇产科学 | 2980篇 |
基础医学 | 26531篇 |
口腔科学 | 3685篇 |
临床医学 | 30814篇 |
内科学 | 32952篇 |
皮肤病学 | 2229篇 |
神经病学 | 12386篇 |
特种医学 | 8226篇 |
外国民族医学 | 138篇 |
外科学 | 21723篇 |
综合类 | 35424篇 |
现状与发展 | 55篇 |
一般理论 | 19篇 |
预防医学 | 13162篇 |
眼科学 | 6695篇 |
药学 | 22723篇 |
194篇 | |
中国医学 | 12355篇 |
肿瘤学 | 19252篇 |
出版年
2024年 | 692篇 |
2023年 | 3552篇 |
2022年 | 9180篇 |
2021年 | 11499篇 |
2020年 | 8600篇 |
2019年 | 7541篇 |
2018年 | 8038篇 |
2017年 | 7087篇 |
2016年 | 6658篇 |
2015年 | 10253篇 |
2014年 | 12555篇 |
2013年 | 10700篇 |
2012年 | 16011篇 |
2011年 | 17950篇 |
2010年 | 10524篇 |
2009年 | 8187篇 |
2008年 | 11117篇 |
2007年 | 11094篇 |
2006年 | 11233篇 |
2005年 | 11325篇 |
2004年 | 7004篇 |
2003年 | 6615篇 |
2002年 | 5506篇 |
2001年 | 4939篇 |
2000年 | 5355篇 |
1999年 | 5696篇 |
1998年 | 3528篇 |
1997年 | 3497篇 |
1996年 | 2813篇 |
1995年 | 2606篇 |
1994年 | 2143篇 |
1993年 | 1376篇 |
1992年 | 1891篇 |
1991年 | 1595篇 |
1990年 | 1290篇 |
1989年 | 1091篇 |
1988年 | 1014篇 |
1987年 | 890篇 |
1986年 | 726篇 |
1985年 | 525篇 |
1984年 | 336篇 |
1983年 | 243篇 |
1982年 | 149篇 |
1981年 | 145篇 |
1980年 | 111篇 |
1979年 | 142篇 |
1978年 | 49篇 |
1977年 | 53篇 |
1975年 | 57篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Yaobin Ouyang Gongmeizi Liu Wenting Xu Zhen Yang Nianshuang Li Chuan Xie Chun Zhou Jiang Chen Yin Zhu Junbo Hong Nonghua Lu 《Oncology Letters》2021,21(2)
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
62.
63.
Feng He Yuanjun Ma Shi Li Haozhe Ren Qian Liu Xiaohua Chen Hui Miao Tao Ye Qian Lu Zuge Yang Tianle Li Xin Tong Hongxu Yang Mian Zhang Helin Wang Yazhou Wang Shibin Yu 《Journal of bone and mineral research》2022,37(5):1044-1055
Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative disease for which the underlying mechanism still remains unclear. Compared with apoptosis and autophagy, necroptosis causes greater harm to tissue homeostasis by releasing damage-associated molecular patterns (DAMPs). However, the role of necroptosis and downstream key DAMPs in TMJOA is unknown. Here, rodent models of TMJOA were established by the unilateral anterior crossbite (UAC). Transmission electron microscopy (TEM) and immunohistochemistry of receptor interacting protein kinase 3 (RIPK3)/phosphorylation of mixed lineage kinase domain-like protein (pMLKL) were conducted to evaluate the occurrence of necroptosis in vivo. The therapeutic effects of blocking necroptosis were achieved by intra-articularly injecting RIPK3 or MLKL inhibitors and using RIPK3 or MLKL knockout mice. In vitro necroptosis of condylar chondrocyte was induced by combination of tumor necrosis factor alpha (TNFα), second mitochondria-derived activator of caspases (SMAC) mimetics and carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]- fluoromethylketone (z-VAD-fmk). The possible DAMPs released by necroptotic chondrocytes were screened by quantitative proteomics and blocked by specific antibody. Translucent cytosol, swollen organelles, and ruptured cell membranes, features of necroptosis, were frequently manifested in chondrocytes at the early stage of condylar cartilage degeneration in TMJOA, which was accompanied by upregulation of RIPK3/pMLKL. Inhibiting or knocking out RIPK3/MLKL significantly prevented cartilage degeneration. DAMPs released by necroptotic condylar chondrocytes, such as syndecan 4 (SDC4) and heat shock protein 90 (HSP90), were verified. Furthermore, blocking the function of SDC4 significantly attenuated the expression of TNFα in cartilage and synovium, and accordingly increased cartilage thickness and reduced synovial inflammation. Thus, the necroptotic vicious cycle of TNFα-SDC4-TNFα contributes to cartilage degeneration and synovitis, and can serve as a potential therapeutic target for treating TMJOA. © 2022 American Society for Bone and Mineral Research (ASBMR). 相似文献
64.
65.
目的:肌少症对老年肝癌术后恢复及预后的影响。方法:选取2015年1月至2017年12月收治的114例老年肝癌,根据有无合并肌少症,分为肌少症组(n=35)和非肌少症组(n=79)。比较两组患者的术后恢复及生存情况。结果:肌少症组总并发症发生率、住院时间和30 d再入院率均高于对照组,差异均有统计学意义(P<0.05)。肌少症组中位生存时间为25.9个月,1年、2年、3年累积总生存率为74.3%、51.1%、24.5%,而非肌少症组中位生存时间为35.7个月,1年、2年、3年累积总生存率为87.3%、75.6%、49.4%,差异有统计学意义(P=0.004)。单因素分析结果显示,老年肝癌术后预后与Charlson合并症指数(CCI)、肌少症、巴塞罗那分期(BCLC)、甲胎蛋白、肿瘤大小、肿瘤个数、肿瘤分化程度、微血管侵犯(MVI)相关(P<0.05)。Cox多因素分析结果显示,CCI、肌少症、BCLC分期、肿瘤个数、MVI是老年肝癌术后预后的独立危险因素(P<0.05)。结论:肌少症会增加老年肝癌患者术后并发症发生率,延长住院时间,影响术后恢复,同时也会降低总生存率。 相似文献
66.
67.
68.
69.
The objective of this study was to investigate the absorption behavior of chikusetsusaponin IVa (CHS‐IVa) in the rat intestine using single‐pass intestinal perfusion (SPIP) and to classify CHS‐IVa into the biopharmaceutics classification system (BCS). The equilibrium solubility of CHS‐IVa was determined by the shaker method. The absorption mechanism of CHS‐IVa in the intestine was studied by comparing the Peff of different concentrations of CHS‐IVa. The intestinal site dependence of CHS‐IVa absorption was studied by comparing the Peff of the same concentration of CHS‐IVa in different intestinal segments. The relationship between CHS‐IVa and intestinal efflux protein was studied by perfusion with an efflux protein inhibitor. The permeability of CHS‐IVa was investigated by comparing the Peff of CHS‐IVa and the reported value. The solubility of CHS‐IVa over the pH range 1.0–7.5 was 14.4 ± 0.29 to 16.9 ± 0.34 mg/ml. The Peff of CHS‐IVa in the duodenum was 1.76 × 10?3 to 2.00 × 10?3 cm/min. The Peff of CHS‐IVa in the jejunum was 1.26 × 10?3 to 1.39 × 10?3 cm/min. The Peff of CHS‐IVa in the ileum was 1.25 × 10?3 to 1.31 × 10?3 cm/min. The Peff of CHS‐IVa in the colon was 1.02 × 10?3 to 1.08 × 10?3 cm/min. There was no statistical difference of the Peff in the four segments at different CHS‐IVa concentrations. The Peff of CHS‐IVa (0.07, 0.7 and 7.0 mg/ml) were all notably smaller than the reported Peff (3.00 × 10?3 cm/min) in the jejunum. The Peff of CHS‐IVa was not influenced by verapamil (P‐gp inhibitor), indomethacin (MRP inhibitor) and pantoprazole (BCRP inhibitor). CHS‐IVa was classified as high solubility, low permeability and BCS III. The main absorptive tracts were the upper intestinal tracts and the rank order of intestinal permeability was duodenum > jejunum ≈ ileum > colon. The transport mechanism of CHS‐IVa in all intestinal segments might be primarily passive transport. CHS‐IVa was not a substrate of P‐gp, MRP and BCRP. 相似文献
70.
Pengfei Liu 《Remote sensing letters.》2019,10(7):659-668
This letter proposed a new and effective total generalized variation (TGV) induced spatial difference prior model for variational pansharpening problem, which aimed to estimate a high-resolution (HR) multispectral (MS) image from its low-resolution (LR) version and the corresponding HR panchromatic (Pan) image of the same earth scene. In addition to using the local spectral consistency constraint for spectral information preserving, this letter particularly exploited the spatial difference prior between the HR-MS and Pan images, and hence proposed a new TGV-induced spatial difference prior term for spatial information preserving. Then, an efficient optimization algorithm was designed for solving the proposed model under the fast iterative shrinkage-thresholding algorithm (FISTA) framework. Finally, the experimental results validated that the proposed method performed higher spatial and spectral qualities than various methods in both the subjective and objective aspects. 相似文献