全文获取类型
收费全文 | 48224篇 |
免费 | 4298篇 |
国内免费 | 3278篇 |
出版年
2024年 | 72篇 |
2023年 | 477篇 |
2022年 | 1335篇 |
2021年 | 2255篇 |
2020年 | 1562篇 |
2019年 | 1874篇 |
2018年 | 1840篇 |
2017年 | 1335篇 |
2016年 | 1923篇 |
2015年 | 2847篇 |
2014年 | 3305篇 |
2013年 | 3525篇 |
2012年 | 4227篇 |
2011年 | 3776篇 |
2010年 | 2408篇 |
2009年 | 2012篇 |
2008年 | 2368篇 |
2007年 | 2151篇 |
2006年 | 1909篇 |
2005年 | 1614篇 |
2004年 | 1513篇 |
2003年 | 1385篇 |
2002年 | 1285篇 |
2001年 | 1044篇 |
2000年 | 939篇 |
1999年 | 907篇 |
1998年 | 565篇 |
1997年 | 474篇 |
1996年 | 473篇 |
1995年 | 455篇 |
1994年 | 410篇 |
1993年 | 284篇 |
1992年 | 414篇 |
1991年 | 338篇 |
1990年 | 360篇 |
1989年 | 314篇 |
1988年 | 221篇 |
1987年 | 196篇 |
1986年 | 178篇 |
1985年 | 149篇 |
1984年 | 141篇 |
1983年 | 113篇 |
1982年 | 95篇 |
1981年 | 73篇 |
1980年 | 51篇 |
1979年 | 86篇 |
1978年 | 58篇 |
1977年 | 56篇 |
1975年 | 61篇 |
1973年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Chen Chen Raymond Dagnino Jr. Charles Q. Huang James R. McCarthy Dimitri E. Grigoriadis 《Bioorganic & medicinal chemistry letters》2001,11(24):3165-3168
Cyclizations of alkylhydrazines with N-acyl-S-methylisothioureas, readily synthesized from acyl chlorides, sodium thioisocyanate, dialkylamines then methyl iodide in a one-pot reaction, gave 1-alkyl-3-dialkylamino-5-phenyltriazoles 7 as major products. The regioisomers were assigned through the use of NOE NMR experiments. While bearing a N-bis(cyclopropyl)methyl-N-propylamino group, this series of compounds shows very good binding affinity on the human CRF1 receptor. Among them, 1-methyl-3-[N-bis(cyclopropyl)methyl-N-propylamino]-5-(2,4-dichlorophenyl)-1H-[1,2,4]triazole 7a had the best binding affinity for the CRF1 receptor (Ki=9 nM). 相似文献
24.
25.
Jian Xiao Dan Chen Xiu-Xian Lin Shi-Fang Peng Mei-Fang Xiao Wei-Hua Huang Yi-Cheng Wang Jing-Bo Peng Wei Zhang Dong-Sheng Ouyang Yao Chen 《PloS one》2016,11(2)
Ginsenoside compound K (CK), a rare ginsenoside originating from Panax Ginseng, has been found to possess unique pharmacological activities specifically as anti-cancers. However, the role of cytochrome P450s (CYPs) in the metabolism of CK is unclear. In this study, we screened the CYPs for the metabolism of CK in vitro using human liver microsomes (HLMs) or human recombinant CYPs. The results showed that CK inhibited the enzyme activities of CYP2C9 and CYP3A4 in the HLMs. The Km and Vmax values of CK were 84.20±21.92 μM and 0.28±0.04 nmol/mg protein/min, respectively, for the HLMs; 34.63±10.48 μM and 0.45±0.05 nmol/nmol P450/min, respectively, for CYP2C9; and 27.03±5.04 μM and 0.68±0.04 nmol/nmol P450/min, respectively, for CYP3A4. The IC50 values were 16.00 μM and 9.83 μM, and Ki values were 14.92 μM and 11.42μM for CYP2C9 and CYP3A4, respectively. Other human CYP isoforms, including CYP1A2, CYP2A6, CYP2D6, CYP2E1, and CYP2C19, showed minimal or no effect on CK metabolism. The results suggested that CK was a substrate and also inhibitors for both CYP2C9 and CYP3A4. Patients using CK in combination with therapeutic drugs that are substrates of CYP2C9 and CYP3A4 for different reasons should be careful, although the inhibiting potency of CK is much poorer than that of enzyme-specific inhibitors. 相似文献
26.
27.
Bing-Ren Huang 《中国科学:生命科学英文版》2010,53(4):531-532
<正>During the Chinese New Year holidays in 2008, Professor Zhang Nai-Heng, former chair of the Department of Biochemistry, Beijing Medical College, informed me of the sad news that Professor Ray Wu had passed away in Ithaca, New York on 相似文献
28.
Zhaohua Zhang LiLi Ge Shanshan Zhang Jue Wang Wen Jiang Qian Xin Yun Luan 《Journal of cellular and molecular medicine》2020,24(23):13938
The aim of the study was to explore the mechanism of mesenchymal stem cell‐derived exosomes (MSC‐EXO) to protect against experimentally induced pulmonary hypertension (PH). Monocrotaline (MCT)‐induced rat model of PH was successfully established by a single intraperitoneal injection of 50 mg/kg MCT, 3 weeks later the animals were treated with MSC‐EXO via tail vein injection. Post‐operation, our results showed that MSC‐EXO could significantly reduce right ventricular systolic pressure (RVSP) and the right ventricular hypertrophy index, attenuate pulmonary vascular remodelling and lung fibrosis in vivo. In vitro experiment, the hypoxia models of pulmonary artery endothelial cell (PAEC) and pulmonary vascular smooth muscle cell (PASMC) were used. We found that the expression levels of Wnt5a, Wnt11, BMPR2, BMP4 and BMP9 were increased, but β‐catenin, cyclin D1 and TGF‐β1 were decreased in MSC‐EXO group as compared with MCT or hypoxia group in vivo or vitro. However, these increased could be blocked when cells were transfected with Wnt5a siRNA in vitro. Taken together, these results suggested that the mechanism of MSC‐EXO to prevent PH vascular remodelling may be via regulation of Wnt5a/BMP signalling pathway. 相似文献
29.
30.
Ying Jin Dan Long Juan Li Ruichao Yu Yueming Song Jie Fang Xi Yang Shu Zhou Shishu Huang Zhihe Zhao 《Journal of cellular physiology》2019,234(9):14838-14851
Bone and tooth, fundamental parts of the craniofacial skeleton, are anatomically and developmentally interconnected structures. Notably, pathological processes in these tissues underwent together and progressed in multilevels. Extracellular vesicles (EVs) are cell-released small organelles and transfer proteins and genetic information into cells and tissues. Although EVs have been identified in bone and tooth, particularly EVs have been identified in the bone formation and resorption, the concrete roles of EVs in bone and tooth development and diseases remain elusive. As such, we review the recent progress of EVs in bone and tooth to highlight the novel findings of EVs in cellular communication, tissue homeostasis, and interventions. This will enhance our comprehension on the skeletal biology and shed new light on the modulation of skeletal disorders and the potential of genetic treatment. 相似文献