全文获取类型
收费全文 | 7742篇 |
免费 | 641篇 |
国内免费 | 1篇 |
出版年
2023年 | 18篇 |
2022年 | 25篇 |
2021年 | 73篇 |
2020年 | 63篇 |
2019年 | 109篇 |
2018年 | 154篇 |
2017年 | 114篇 |
2016年 | 237篇 |
2015年 | 363篇 |
2014年 | 422篇 |
2013年 | 435篇 |
2012年 | 551篇 |
2011年 | 558篇 |
2010年 | 349篇 |
2009年 | 329篇 |
2008年 | 450篇 |
2007年 | 434篇 |
2006年 | 393篇 |
2005年 | 397篇 |
2004年 | 399篇 |
2003年 | 349篇 |
2002年 | 313篇 |
2001年 | 302篇 |
2000年 | 241篇 |
1999年 | 212篇 |
1998年 | 73篇 |
1997年 | 75篇 |
1996年 | 54篇 |
1995年 | 58篇 |
1994年 | 37篇 |
1993年 | 27篇 |
1992年 | 77篇 |
1991年 | 84篇 |
1990年 | 50篇 |
1989年 | 54篇 |
1988年 | 46篇 |
1987年 | 44篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1979年 | 19篇 |
1978年 | 22篇 |
1977年 | 23篇 |
1976年 | 24篇 |
1974年 | 24篇 |
1973年 | 19篇 |
1971年 | 20篇 |
1970年 | 17篇 |
排序方式: 共有8384条查询结果,搜索用时 28 毫秒
1.
2.
3.
Sitagliptin attenuates sympathetic innervation via modulating reactive oxygen species and interstitial adenosine in infarcted rat hearts 下载免费PDF全文
Tsung‐Ming Lee Wei‐Ting Chen Chen‐Chia Yang Shinn‐Zong Lin Nen‐Chung Chang 《Journal of cellular and molecular medicine》2015,19(2):418-429
We investigated whether sitagliptin, a dipeptidyl peptidase‐4 (DPP‐4) inhibitor, attenuates arrhythmias through inhibiting nerve growth factor (NGF) expression in post‐infarcted normoglycemic rats, focusing on adenosine and reactive oxygen species production. DPP‐4 bound adenosine deaminase has been shown to catalyse extracellular adenosine to inosine. DPP‐4 inhibitors increased adenosine levels by inhibiting the complex formation. Normoglycemic male Wistar rats were subjected to coronary ligation and then randomized to either saline or sitagliptin in in vivo and ex vivo studies. Post‐infarction was associated with increased oxidative stress, as measured by myocardial superoxide, nitrotyrosine and dihydroethidium fluorescent staining. Measurement of myocardial norepinephrine levels revealed a significant elevation in vehicle‐treated infarcted rats compared with sham. Compared with vehicle, infarcted rats treated with sitagliptin significantly increased interstitial adenosine levels and attenuated oxidative stress. Sympathetic hyperinnervation was blunted after administering sitagliptin, as assessed by immunofluorescent analysis and western blotting and real‐time quantitative RT‐PCR of NGF. Arrhythmic scores in the sitagliptin‐treated infarcted rats were significantly lower than those in vehicle. Ex vivo studies showed a similar effect of erythro‐9‐(2‐hydroxy‐3‐nonyl) adenine (an adenosine deaminase inhibitor) to sitagliptin on attenuated levels of superoxide and NGF. Furthermore, the beneficial effects of sitagliptin on superoxide anion production and NGF levels can be reversed by 8‐cyclopentyl‐1,3‐dipropulxanthine (adenosine A1 receptor antagonist) and exogenous hypoxanthine. Sitagliptin protects ventricular arrhythmias by attenuating sympathetic innervation via adenosine A1 receptor and xanthine oxidase‐dependent pathways, which converge through the attenuated formation of superoxide in the non‐diabetic infarcted rats. 相似文献
4.
5.
Binding of peptides with basic residues to membranes containing acidic phospholipids. 总被引:16,自引:4,他引:12 下载免费PDF全文
There are clusters of basic amino acids on many cytoplasmic proteins that bind transiently to membranes (e.g., protein kinase C) as well as on the cytoplasmic domain of many intrinsic membrane proteins (e.g., glycophorin). To explore the possibility that these basic residues bind electrostatically to monovalent acidic lipids, we studied the binding of the peptides Lysn and Argn (n = 1-5) to bilayer membranes containing phosphatidylserine (PS) or phosphatidylglycerol (PG). We made electrophoretic mobility measurements using multilamellar vesicles, fluorescence and equilibrium binding measurements using large unilamellar vesicles, and surface potential measurements using monolayers. None of the peptides bound to vesicles formed from the zwitterionic lipid phosphatidylcholine (PC) but all bound to vesicles formed from PC/PS or PC/PG mixtures. None of the peptides exhibited specificity between PS and PG. Each lysine residue that was added to Lys2 decreased by one order of magnitude the concentration of peptide required to reverse the charge on the vesicle; equivalently it increased by one order of magnitude the binding affinity of the peptides for the PS vesicles. The simplest explanation is that each added lysine binds independently to a separate PS with a microscopic association constant of 10 M-1 or a free energy of approximately 1.4 kcal/mol. Similar, but not identical, results were obtained with the Argn peptides. A simple theoretical model combines the Gouy-Chapman theory (which accounts for the nonspecific electrostatic accumulation of the peptides in the aqueous diffuse double layer adjacent to the membrane) with mass action equations (which account for the binding of the peptides to greater than 1 PS). This model can account qualitatively for the dependence of binding on both the number of basic residues in the peptides and the mole fraction of PS in the membrane. 相似文献
6.
Su Kang Kim Il GyuKo Hae Jeong Park Joo-Ho Chung Kyu Bong Cho Oh Young Kwon Kyeong Hun Park Young Sub Ahn Chun Geon Park Young Ock Kim 《Saudi Journal of Biological Sciences》2018,25(1):66-70
The prostatic hyperplasia in benign prostatic hyperplasia (BPH) leads to obstructive micturition symptoms. Previous studies showed that pontine micturition center (PMC), ventrolateral periaqueductal gray (vlPAG), and medial preopticnucleus (MPA) regions in the brain have been known to regulate the urinary bladder function. The present study shows the influences of Panax ginseng on nerve growth factor (NGF) expressions in PMC, vlPAG, and MPA regions in the brain. Wistar rats were used for the present study. The rats split into four groups; 4 groups (n = 6) in control group, BPH-induced group, BPH-induced and P. ginseng-treated group, and BPH-induced and finasteride-treated group. BPH in rats was induced by testosterone and the animals were evaluated for NGF expression in PMC, vlPAG, and MPA regions in the brain. The NGF expression was identified using immunohistochemistry (IHC). The NGF expression by IHC showed spots with dark brown color. In our results, NGF expressions in PMC, vlPAG, and MPA regions in the brainstem of the BPH-induced group showed increase than the control animal. These increased NGF expressions in three regions were decreased using treatment with P. ginseng (200 mg/kg). These results suggest that P. ginseng has therapeutic effects on the symptoms of BPH and is associated with the regulation of NGF expression in the brain. In conclusion, the administration of P. ginseng helps nerve growth factor activation. 相似文献
7.
Aleksandr Sverzhinsky Shuo Qian Lin Yang Marc Allaire Isabel Moraes Dewang Ma Jacqueline W. Chung Manuela Zoonens Jean-Luc Popot James W. Coulton 《The Journal of membrane biology》2014,247(9-10):1005-1018
Nutrient import across Gram-negative bacteria’s outer membrane is powered by the proton-motive force, delivered by the cytoplasmic membrane protein complex ExbB–ExbD–TonB. Having purified the ExbB4–ExbD2 complex in the detergent dodecyl maltoside, we substituted amphipol A8-35 for detergent, forming a water-soluble membrane protein/amphipol complex. Properties of the ExbB4–ExbD2 complex in detergent or in amphipols were compared by gel electrophoresis, size exclusion chromatography, asymmetric flow field-flow fractionation, thermal stability assays, and electron microscopy. Bound detergent and fluorescently labeled amphipol were assayed quantitatively by 1D NMR and analytical ultracentrifugation, respectively. The structural arrangement of ExbB4–ExbD2 was examined by EM, small-angle X-ray scattering, and small-angle neutron scattering using a deuterated amphipol. The amphipol-trapped ExbB4–ExbD2 complex is slightly larger than its detergent-solubilized counterpart. We also investigated a different oligomeric form of the two proteins, ExbB6–ExbD4, and propose a structural arrangement of its transmembrane α-helical domains. 相似文献
8.
9.
Jin-Gyun Lee Kimberly Q. McKinney Yong-Yook Lee Hae-Na Chung Antonis J. Pavlopoulos Kook Y. Jung Woong-Ki Kim Marcelo J. Kuroda David K. Han Sunil Hwang 《PloS one》2015,10(5)
Though the rhesus monkey is one of the most valuable non-human primate animal models for various human diseases because of its manageable size and genetic and proteomic similarities with humans, proteomic research using rhesus monkeys still remains challenging due to the lack of a complete protein sequence database and effective strategy. To investigate the most effective and high-throughput proteomic strategy, comparative data analysis was performed employing various protein databases and search engines. The UniProt databases of monkey, human, bovine, rat and mouse were used for the comparative analysis and also a universal database with all protein sequences from all available species was tested. At the same time, de novo sequencing was compared to the SEQUEST search algorithm to identify an optimal work flow for monkey proteomics. Employing the most effective strategy, proteomic profiling of monkey organs identified 3,481 proteins at 0.5% FDR from 9 male and 10 female tissues in an automated, high-throughput manner. Data are available via ProteomeXchange with identifier PXD001972. Based on the success of this alternative interpretation of MS data, the list of proteins identified from 12 organs of male and female subjects will benefit future rhesus monkey proteome research. 相似文献
10.