全文获取类型
收费全文 | 20610篇 |
免费 | 3559篇 |
国内免费 | 2784篇 |
专业分类
化学 | 15191篇 |
晶体学 | 241篇 |
力学 | 1404篇 |
综合类 | 179篇 |
数学 | 2251篇 |
物理学 | 7687篇 |
出版年
2024年 | 8篇 |
2023年 | 412篇 |
2022年 | 444篇 |
2021年 | 594篇 |
2020年 | 855篇 |
2019年 | 767篇 |
2018年 | 669篇 |
2017年 | 575篇 |
2016年 | 957篇 |
2015年 | 907篇 |
2014年 | 1154篇 |
2013年 | 1426篇 |
2012年 | 1892篇 |
2011年 | 1943篇 |
2010年 | 1289篇 |
2009年 | 1209篇 |
2008年 | 1397篇 |
2007年 | 1224篇 |
2006年 | 1243篇 |
2005年 | 1030篇 |
2004年 | 830篇 |
2003年 | 699篇 |
2002年 | 682篇 |
2001年 | 566篇 |
2000年 | 466篇 |
1999年 | 558篇 |
1998年 | 379篇 |
1997年 | 342篇 |
1996年 | 414篇 |
1995年 | 350篇 |
1994年 | 301篇 |
1993年 | 234篇 |
1992年 | 211篇 |
1991年 | 184篇 |
1990年 | 157篇 |
1989年 | 133篇 |
1988年 | 119篇 |
1987年 | 81篇 |
1986年 | 73篇 |
1985年 | 54篇 |
1984年 | 37篇 |
1983年 | 31篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1957年 | 5篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Target cell extraction coupled with LC‐MS/MS analysis for screening potential bioactive components in Ginkgo biloba extract with preventive effect against diabetic nephropathy 下载免费PDF全文
Jing‐ying Qiu Xu Chen Xiao‐xiao Zheng Xiang‐lan Jiang Dong‐zhi Yang Yan‐yan Yu Qian Du Dao‐quan Tang Xiao‐xing Yin 《Biomedical chromatography : BMC》2015,29(2):226-232
A rapid and useful approach for screening potential bioactive components in Ginkgo biloba extract (GBE) with preventive effect against diabetic nephropathy (DN) was developed using mesangial cells extraction coupled with high‐performance liquid chromatography tandem mass spectrometry (LC‐MS/MS) analysis. Mesangial cells were first divided into two groups according to their treatments with high glucose or high glucose plus GBE. After incubation for 4, 8, 12, 16, 24 and 48 h, the cells were harvested and extracted with 40% acetic acid in water before LC‐MS/MS analysis. Then, 19 compounds and five metabolites were found to selectively combine with mesangial cells. Notably, compounds including quercetin and rutin were identified or tentatively characterized according to the results of retention time and MS spectra, which is highly consistent with our previous reports that quercetin and rutin are potent protective agents against glomerulosclerosis in DN. Therefore, all these results indicate that target cell extraction coupled with LC‐MS/MS analysis can be successfully applied for predicting the bioactive components in GBE with preventive effect against DN. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
72.
73.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414
74.
75.
在中国科学技术大学夏季学期的研究型实验课程"化学科研基础训练"中开设"壳聚糖的制备与表征"综合实验,以龙虾壳为原料,通过除蛋白、脱盐、脱色、脱乙酰等一系列反应,制备得到目标产物壳聚糖。运用红外光谱、核磁共振仪、黏度法、滴定等对产品的结构及性能进行表征。 相似文献
76.
Mass concentration and isotopic values δ13C and 14C are presented for the water-insoluble refractory carbon(WIRC) component of total suspended particulates(TSP),collected weekly during 2003,as well as from October 2005 to May 2006 at the WMO-GAW Mt.Waliguan(WLG) site.The overall average WIRC mass concentration was(1183±120)ng/m3(n = 79),while seasonal averages were 2081 ±1707(spring),454±205(summer),650±411(autumn),and 1019±703(winter) ng/m3.Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer,although WIRC concentrations were typically higher,especially in winter and spring.The δ13C PDB value(-25.3 ± 0.8)%.determined for WIRC suggests that its sources are C3 biomass or fossil fuel combustion.No seasonal change in δ13C PDB was evident.The average percent Modern Carbon(pMC) for 14C in WIRC for winter and spring was(67.2 ± 7.7)%(n = 29).Lower pMC values were associated with air masses transported from the area east of WLG,while higher pMC values were associated with air masses from the Tibetan Plateau,southwest of WLG.Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event. 相似文献
77.
Highly dispersed palladium nanoclusters incorporated in amino‐functionalized silica spheres for the selective hydrogenation of succinic acid to γ‐butyrolactone 下载免费PDF全文
Highly dispersed palladium nanoclusters incorporated on amino‐functionalized silica sphere surfaces (Pd/SiO2‐NH2) were fabricated by a simple one‐pot synthesis utilizing 3‐(2‐aminoethylamino)propyltrimethoxysilane (AAPTS) as coordinating agent. Uniform palladium nanoclusters with an average size of 1.1 nm can be obtained during the co‐condensation of tetraethyl orthosilicate and AAPTS owing to the strong interaction between palladium species and amino groups in AAPTS. The palladium particle size can be controlled by addition of AAPTS and plays a significant role in the catalytic performance. The Pd/SiO2‐NH2 catalyst exhibits high catalytic activity for succinic acid hydrogenation with 100% conversion and 94% selectivity towards γ‐butyrolactone using 1,4‐dioxane as solvent at 240°C and 60 bar for 4 h. Moreover, the Pd/SiO2‐NH2 catalyst is robust and readily reusable without loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
78.
79.
80.