全文获取类型
收费全文 | 35111篇 |
免费 | 3050篇 |
国内免费 | 2926篇 |
专业分类
41087篇 |
出版年
2024年 | 97篇 |
2023年 | 447篇 |
2022年 | 1113篇 |
2021年 | 1916篇 |
2020年 | 1317篇 |
2019年 | 1616篇 |
2018年 | 1590篇 |
2017年 | 1171篇 |
2016年 | 1626篇 |
2015年 | 2147篇 |
2014年 | 2617篇 |
2013年 | 2757篇 |
2012年 | 3105篇 |
2011年 | 2869篇 |
2010年 | 1750篇 |
2009年 | 1625篇 |
2008年 | 1838篇 |
2007年 | 1606篇 |
2006年 | 1357篇 |
2005年 | 1170篇 |
2004年 | 1028篇 |
2003年 | 1017篇 |
2002年 | 860篇 |
2001年 | 686篇 |
2000年 | 603篇 |
1999年 | 557篇 |
1998年 | 340篇 |
1997年 | 284篇 |
1996年 | 298篇 |
1995年 | 248篇 |
1994年 | 234篇 |
1993年 | 176篇 |
1992年 | 217篇 |
1991年 | 177篇 |
1990年 | 162篇 |
1989年 | 111篇 |
1988年 | 82篇 |
1987年 | 73篇 |
1986年 | 53篇 |
1985年 | 58篇 |
1984年 | 22篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1966年 | 1篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Xiao LiWei Xing Shuping Zhuo Jin ZhouFeng Li Shi-Zhang QiaoGao-Qing Lu 《Bioresource technology》2011,102(2):1118-1123
Series of nanoporous carbons are prepared from sunflower seed shell (SSS) by two different strategies and used as electrode material for electrochemical double-layer capacitor (EDLC). The surface area and pore-structure of the nanoporous carbons are characterized intensively using N2 adsorption technique. The results show that the pore-structure of the carbons is closely related to activation temperature and dosage of KOH. Electrochemical measurements show that the carbons made by impregnation-activation process have better capacitive behavior and higher capacitance retention ratio at high drain current than the carbons made by carbonization-activation process, which is due to that there are abundant macroscopic pores and less interior micropore surface in the texture of the former. More importantly, the capacitive performances of these carbons are much better than ordered mesoporous carbons and commercial wood-based active carbon, thus highlighting the success of preparing high performance electrode material for EDLC from SSS. 相似文献
12.
Qibo Jiang Shuguang Li 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1999,727(1-2)
Gabapentin (GBP) is a new antiepileptic drug approved for clinical treatment of partial seizures in the USA. Serum GBP concentrations in 283 patients were studied using high-performance liquid chromatography with fluorescence detection. The standard curves were linear over a range of 60 ng to 15 μg/ml. The coefficient of variations were 3.4 to 8.8% and 1.4 to 9.8% for intra- and inter-assay studies, respectively. The lower limit of quantitation was 10 ng/ml. Of the 283 patients studied, 72.5% had GBP levels between 2 and 10 μg/ml, 14.8% were below 2 μg/ml and 12.7% above 10 μg/ml. The mean±S.E. of GBP in 283 patients was 5.38±0.23 μg/ml. Peak concentrations of more than 15 μg/ml and trough levels as low as 0.1 μg/ml were not uncommon. The method described was rapid, simple, highly sensitive and reproducible. Other antiepileptic drugs and endogenous compounds did not interfere with the assay. 相似文献
13.
14.
15.
Joong Kyu Kim Mark Klinger Jonathan Benjamin Yuanyuan Xiao David J. Erle Dan R. Littman Nigel Killeen 《PloS one》2009,4(8)
Signaling through the T cell antigen receptor (TCR) is important for the homeostasis of naïve and memory CD4+ T cells. The significance of TCR signaling in regulatory T (Treg) cells has not been systematically addressed. Using an Ox40-cre allele that is prominently expressed in Treg cells, and a conditional null allele of the gene encoding p56Lck, we have examined the importance of TCR signaling in Treg cells. Inactivation of p56Lck resulted in abnormal Treg homeostasis characterized by impaired turnover, preferential redistribution to the lymph nodes, loss of suppressive function, and striking changes in gene expression. Abnormal Treg cell homeostasis and function did not reflect the involvement of p56Lck in CD4 function because these effects were not observed when CD4 expression was inactivated by Ox40-cre.The results make clear multiple aspects of Treg cell homeostasis and phenotype that are dependent on a sustained capacity to signal through the TCR. 相似文献
16.
17.
Y. Jiang 《Biochimica et Biophysica Acta (BBA)/General Subjects》1994,1201(1):76-84
Proteolysis of the hydroxylase component of soluble methane monooxygenase (MMO) with trypsin yielded a protein which retained 50% activity in a standard MMO assay. In an H2O2-driven assay, in which H2O2 replaced two of the protein components, NADH and O2 used in the standard assay, the proteolysed hydroxylase retained full activity for ethane, propane and propene, but had a 2–3 fold increase with methane as substrate. Several crosslinking reagents have been tested for their ability to stabilise the proteolysed form of the hydroxylase. Using polyoxyethylene bis(imidazolyl carbonyl) (Mr 3350) as the crosslinking agent, increased thermostability of the hydroxylase was observed. Activated methoxypolyethylene glycol (Mr 5000) was used to modify the hydroxylase which was now soluble in organic solvents as well as water and could be activated by H2O2. The glycol-modified hydroxylase functioned well in organic solvents in the catalysis of propene oxidation. 相似文献
18.
19.
20.
Protection of iron-catalysed the radical damage to DNA and lipids by copper (II) bleomycin 总被引:3,自引:0,他引:3
J M Gutteridge F Xiao Change 《Biochemical and biophysical research communications》1981,99(4):1354-1360
The ability of Copper(II)-bleomycin to inhibit oxygen-free-radical damage to biomolecules has been assessed. This copper complex showed inhibitory properties towards iron-catalysed damage to phospholipid membranes and cell-free DNA. It was also able to prevent superoxide-dependent reduction of nitroblue tetrazolium (NBT). Unlike iron, copper-bleomycin does not damage DNA . This may result from a site-specific dismutation of superoxide radicals on the DNA molecule. 相似文献