全文获取类型
收费全文 | 14821篇 |
免费 | 1536篇 |
国内免费 | 1523篇 |
专业分类
17880篇 |
出版年
2024年 | 45篇 |
2023年 | 218篇 |
2022年 | 527篇 |
2021年 | 838篇 |
2020年 | 613篇 |
2019年 | 771篇 |
2018年 | 765篇 |
2017年 | 552篇 |
2016年 | 738篇 |
2015年 | 930篇 |
2014年 | 1137篇 |
2013年 | 1130篇 |
2012年 | 1329篇 |
2011年 | 1216篇 |
2010年 | 723篇 |
2009年 | 699篇 |
2008年 | 753篇 |
2007年 | 652篇 |
2006年 | 519篇 |
2005年 | 468篇 |
2004年 | 485篇 |
2003年 | 494篇 |
2002年 | 440篇 |
2001年 | 376篇 |
2000年 | 285篇 |
1999年 | 238篇 |
1998年 | 155篇 |
1997年 | 116篇 |
1996年 | 121篇 |
1995年 | 75篇 |
1994年 | 79篇 |
1993年 | 61篇 |
1992年 | 59篇 |
1991年 | 64篇 |
1990年 | 52篇 |
1989年 | 34篇 |
1988年 | 30篇 |
1987年 | 27篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1950年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
苋科植物化学成分的研究进展 总被引:1,自引:0,他引:1
苋科植物有65个属,约1000余种,主要分布在热带、亚热带和温带地区.该科的很多植物具有良好的食用和药用价值,化学成分丰富,含有三萜类、甾体类、黄酮类、生物碱类、色素类和多肽类物质.为推动我国苋科植物资源的更深层次利用和开发,对苋科植物的化学成分研究概况做一综述. 相似文献
93.
利用基因诱捕技术进行小鼠基因剔除的初步研究 总被引:1,自引:0,他引:1
对利用基因诱捕技术进行小鼠基因剔除做了初步的探索,为进一步应用该技术进行小鼠基因功能研究奠定了基础.利用基因诱捕载体转染小鼠ES细胞,获得了36株neo基因单拷贝整合的诱捕ES细胞,其中14株细胞表达有活性的β半乳糖苷酶.将3株诱捕ES细胞分别经显微注射引入到受体囊胚中,再植入假孕母鼠的子宫中使其发育成小鼠.两株细胞得到了程度不同的嵌合体小鼠,其中一株诱捕ES细胞整合至生殖系.利用质粒拯救实验获得了诱捕载体整合位点附近的基因组序列,通过序列比对发现被诱捕的基因可能是一个新基因.X-gal染色结果显示,该基因的表达局限于小鼠腹部及肢芽的部位. 相似文献
94.
Dragon's blood may have radioprotective effects in radiation-induced rat brain injury 总被引:2,自引:0,他引:2
95.
96.
97.
98.
Jin Cui Xiaoqun Li Sicheng Wang Yiming Su Xiao Chen Liehu Cao Xin Zhi Zili Qiu Yao Wang Hao Jiang Biaotong Huang Fang Ji Jiacan Su 《Journal of cellular and molecular medicine》2020,24(11):6149-6161
Bone loss (osteopenia) is a common complication in human solid tumour. In addition, after surgical treatment of gynaecological tumour, osteoporosis often occurs due to the withdrawal of oestrogen. The major characteristic of osteoporosis is the low bone mass with micro-architectural deteriorated bone tissue. And the main cause is the overactivation of osteoclastogenesis, which is one of the most important therapeutic targets. Inflammation could induce the interaction of RANKL/RANK, which is the promoter of osteoclastogenesis. Triptolide is derived from the traditional Chinese herb lei gong teng, presented multiple biological effects, including anti-cancer, anti-inflammation and immunosuppression. We hypothesized that triptolide could inhibits osteoclastogenesis by suppressing inflammation activation. In this study, we confirmed that triptolide could suppress RANKL-induced osteoclastogenesis in bone marrow mononuclear cells (BMMCs) and RAW264.7 cells and inhibited the osteoclast bone resorption functions. PI3K-AKT-NFATc1 pathway is one of the most important downstream pathways of RANKL-induced osteogenesis. The experiments in vitro indicated that triptolide suppresses the activation of PI3K-AKT-NFATc1 pathway and the target point located at the upstream of AKT because both NFATc1 overexpression and AKT phosphorylation could ameliorate the triptolide suppression effects. The expression of MDM2 was elevated, which demonstrated the MDM-p53-induced cell death might contribute to the osteoclastogenesis suppression. Ovariectomy-induced bone loss and inflammation activation were also found to be ameliorated in the experiments in vivo. In summary, the new effect of anti-cancer drug triptolide was demonstrated to be anti-osteoclastogenesis, and we demonstrated triptolide might be a promising therapy for bone loss caused by tumour. 相似文献
99.
Chen Zhou Guowen Shen Fan Yang Jingling Duan Zhen Wu Mingqing Yang Yi Liu Xueli Du Xiaoling Zhang Shengjun Xiao 《Journal of cellular and molecular medicine》2020,24(11):6438-6447
Cisplatin resistance is one of the main obstacles in the treatment of advanced nasopharyngeal carcinoma (NPC). AKR1C1 is a member of the Aldo-keto reductase superfamily (AKRs), which converts aldehydes and ketones to their corresponding alcohols and has been reported to be involved in chemotherapeutic resistance of multiple drugs. The expression and function of AKR1C1 in NPC have not been reported until now. The aim of this research was to investigate the expression of AKR1C1 and it is role in cisplatin resistance in NPC. AKR1C1 protein expression was detected by immunohistochemistry in human NPC tissues and by Western blot assays in NPC and immortalized nasopharyngeal epithelial cells. The effects of AKR1C1 knock-down by siRNA on proliferation, migration and invasion in NPC cells were evaluated by CCK8, wound healing and transwell assays. To evaluate the effects of AKR1C1 silencing on cisplatin sensitivity in NPC cells, CCK8 assays were used to detect cell proliferation, flow cytometry was used to detect cell cycle distribution, and flow cytometry and DAPI staining were used to detect cell apoptosis. AKR1C1 down-regulation was associated with advanced clinicopathological characters such as larger tumor size, more lymphatic nodes involvement, with metastasis and later clinical stages, while AKR1C1 down-regulation was a good prognostic factor for overall survival (OS) in NPC patients. In vitro study showed that AKR1C1 was not directly involved in the malignant biological behaviours such as proliferation, cell cycle progression and migration of NPC cells, whereas AKR1C1 knock-down could enhance cisplatin sensitivity of NPC cells. These results suggest that AKR1C1 is a potential marker for predicting cisplatin response and could serve as a molecular target to increase cisplatin sensitivity in NPC. 相似文献
100.