全文获取类型
收费全文 | 712篇 |
免费 | 38篇 |
国内免费 | 1篇 |
专业分类
751篇 |
出版年
2021年 | 9篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 8篇 |
2014年 | 19篇 |
2013年 | 36篇 |
2012年 | 33篇 |
2011年 | 39篇 |
2010年 | 17篇 |
2009年 | 26篇 |
2008年 | 40篇 |
2007年 | 43篇 |
2006年 | 34篇 |
2005年 | 35篇 |
2004年 | 33篇 |
2003年 | 49篇 |
2002年 | 46篇 |
2001年 | 15篇 |
2000年 | 6篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有751条查询结果,搜索用时 0 毫秒
91.
Mayumi Fujiwara Nonio Nagao Kazuaki Monden Masashi Misumi Katsuhiro Kageyama Kiyotaka Yamamoto Nobuhiko Miwa 《Free radical research》1997,27(1):97-104
Bovine aortic endothelial BAE-2 cells exposed to the peroxidizing agent, tert-butylhydroperoxide (t-BuOOH) or 2,4-nonadienal (NDE), suffered from disruption of cell membrane integrity and from reduction of mitochondrial dehydrogenase activity as assessed by fluorometry using ethidium homodimer and photometry using WST-1, respectively. The cells were protected from t-BuOOH-induced injury more markedly by L-ascorbic acid-2-O-phosphate (Asc2P) stably masked at the 2,3-enediol moiety, which is responsible for the antioxidant ability of L-ascorbic acid (Asc), than by Asc itself. In contrast, NDE-induced membrane disruption but not mitochondrial dysfunction was prevented by Asc2P, whereas Asc exhibited no prevention against both types of injury. The amount of intracellular Asc was 7.2- to 9.0-fold larger in Asc2P-administered BAE-2 cells, where the intact form Asc2P was not detected, than in Asc-administered cells as assessed by HPLC of cell extract with detection by coulometric ECD and W. During transmembrane influx into the cell, Asc2P was concentrated as highly as 70- to 90-fold relative to the extracellular Asc2P concentration, whereas Asc was 8-to 13-fold concentrated as estimated based on an intracellular water content of 0.59 pL/cell determined by [14C]PEG/gas chromatography. Thus, Asc2P but not Asc is highly concentrated in the aqueous phase of the cell after prompt dephosphorylation, and may thereby render the cell more resistant to t-BuOOH-peroxidation assumedly via scavenging of intracellular reactive oxygen species than to peroxidation with the less hydroplulic agent NDE. 相似文献
92.
93.
The mechanism of the lytic action of prymnesin, a toxin produced by the alga, Prymnesium parvum, was studied using liposomes as a model membrane system. Prymnesin showed severe damage to liposomes containing cholesterol but did not affect those without cholesterol. The requirement of cholesterol for the susceptibility to prymnesin was much more strict than the reported requirement for the susceptibility to polyene antibiotics. The net charge on the membranes was shown not to be important for the reaction. 相似文献
94.
Sequence determination of a new parrot bornavirus‐5 strain in Japan: implications of clade‐specific sequence diversity in the regions interacting with host factors 下载免费PDF全文
Ryo Komorizono Akiko Makino Masayuki Horie Tomoyuki Honda Keizo Tomonaga 《Microbiology and immunology》2016,60(6):437-441
In this study, the genome sequence of a new parrot bornavirus‐5 (PaBV‐5) detected in Eclectus roratus was determined. Phylogenetic analysis showed that the genus Bornavirus is divided into three major clades and that PaBV‐5 belongs to clade 2, which contains avian viruses that exhibit infectivity to mammalian cells. Sequence comparisons of the regions known to interact with host factors indicated that the clade 2 avian viruses possess sequences intermediate between the clade 1 mammalian viruses and the clade 3 avian viruses, suggesting that the identified regions might contribute to the differences in virological properties between the three clades. 相似文献
95.
Emi Takeda Kohei Kunimoto Yoshito Kawai Misumi Kataoka Kazuhiko Ishikawa Takashi Nakamura 《Extremophiles : life under extreme conditions》2016,20(5):733-745
O-Phosphoserine sulfhydrylase (OPSS) synthesizes cysteine from O-phospho-l-serine (OPS) and sulfide. We have determined the three-dimensional structures of OPSS from hyperthermophilic archaeon Aeropyrum pernix K1 (ApOPSS) in complex with aminoacrylate intermediate (AA) formed from pyridoxal 5′-phosphate with OPS or in complex with cysteine and compared them with that of ApOPSS. We found an orientational change of F225 at the active-site entrance and constructed an F225A mutant to examine its activities and AA stability and clarify the role of F225 in ApOPSS. The OPS and O-acetyl-l-serine (OAS) sulfhydrylase activities of the F225A mutant decreased by 4.2- and 15-fold compared to those of the wild-type (wt) ApOPSS, respectively. The ability of OPS and OAS to form AA also decreased by 12- and 27-fold, respectively. AA was less stable in the F225A mutant than in the wt ApOPSS. Simulated docking showed that leaving groups, such as phosphate and acetate, were oriented to the inside of the active site in the F225A mutant, whereas they were oriented to the entrance in the wt ApOPSS. These results suggest that F225 in ApOPSS plays important roles in maintaining the hydrophobic environment of AA from solvent water and in controlling the orientation of leaving groups. 相似文献
96.
Tomi T Shibata Y Ikeda Y Taniguchi S Haik C Mataga N Shimada K Itoh S 《Biochimica et biophysica acta》2007,1767(1):22-30
A photosynthetic reaction center (RC) complex was isolated from a purple bacterium, Acidiphilium rubrum. The RC contains bacteriochlorophyll a containing Zn as a central metal (Zn-BChl a) and bacteriopheophytin a (BPhe a) but no Mg-BChl a. The absorption peaks of the Zn-BChl a dimer (P(Zn)), the accessory Zn-BChl a (B(Zn)), and BPhe a (H) at 4 K in the RC showed peaks at 875, 792, and 753 nm, respectively. These peaks were shorter than the corresponding peaks in Rhodobacter sphaeroides RC that has Mg-BChl a. The kinetics of fluorescence from P(Zn)(*), measured by fluorescence up-conversion, showed the rise and the major decay with time constants of 0.16 and 3.3 ps, respectively. The former represents the energy transfer from B(Zn)(*) to P(Zn), and the latter, the electron transfer from P(Zn) to H. The angle between the transition dipoles of B(Zn) and P(Zn) was estimated to be 36 degrees based on the fluorescence anisotropy. The time constants and the angle are almost equal to those in the Rb. sphaeroides RC. The high efficiency of A. rubrum RC seems to be enabled by the chemical property of Zn-BChl a and by the L168HE modification of the RC protein that modifies P(Zn). 相似文献
97.
98.
Kinetic study on ESR signal decay of nitroxyl radicals,potent redox probes for in vivo ESR spectroscopy,caused by reactive oxygen species 总被引:1,自引:0,他引:1
The effect of the chemical structure of nitroxyl spin probes on the rate at which ESR signals are lost in the presence of reactive oxygen species (ROS) was examined. When the spin probes were reacted with either hydroxyl radical (.OH) or superoxide anion radical (O(2)(.-)) in the presence of cysteine or NADH, the probes lost ESR signal depending on both their ring structure and substituents. Pyrrolidine nitroxyl probes were relatively resistant to the signal decay caused by O(2)(.-) with cysteine/NADH. Signal decay rates for these reactions correlated with reported redox potentials of the nitroxyl/oxoammonium couple of spin probes, suggesting that the signal decay mechanism in both cases involves the oxidation of a nitroxyl group. The apparent rate constants of the reactions between the spin probe and .OH and between the spin probe and O(2)(.-) in the presence of cysteine were estimated using mannitol and superoxide dismutase (SOD), respectively, as competitive standards. The rate constants for spin probes and .OH were in the order of 10(9) M(-1) s(-1), much higher than those for the probes and O(2)(.-) in the presence of cysteine (10(3)-10(4) M(-1) s(-1)). These basic data are useful for the measurement of .OH and O(2)(.-) in living animals by in vivo ESR spectroscopy. 相似文献
99.
Albert S. Reger Matthew P. Yang Shizuyo Koide-Yoshida Elaine Guo Shrenik Mehta Keizo Yuasa Alan Liu Darren E. Casteel Choel Kim 《The Journal of biological chemistry》2014,289(37):25393-25403
cGMP-dependent protein kinase (PKG)-interacting proteins (GKIPs) mediate cellular targeting of PKG isoforms by interacting with their leucine zipper (LZ) domains. These interactions prevent aberrant signaling cross-talk between different PKG isotypes. To gain detailed insight into isotype-specific GKIP recognition by PKG, we analyzed the type II PKG leucine zipper domain and found that residues 40–83 dimerized and specifically interacted with Rab11b. Next, we determined a crystal structure of the PKG II LZ-Rab11b complex. The PKG II LZ domain presents a mostly nonpolar surface onto which Rab11b docks, through van der Waals interactions. Contact surfaces in Rab11b are found in switch I and II, interswitch, and the β1/N-terminal regions. This binding surface dramatically differs from that seen in the Rab11 family of interacting protein complex structures. Structural comparison with PKG Iα and Iβ LZs combined with mutagenic analysis reveals that GKIP recognition is mediated through surface charge interactions. 相似文献
100.
Six serinal derivatives were synthesized and tested for their anti-human immunodeficiency virus type-1 (HIV-1) activity against HIV-1-infected cells. Of the 6 serinal derivatives tested, only N,O-didecanoyl serinal dimethylacetal (DDSD) was found to strongly suppress progeny virus production from acute HIV-1-infected CEM cells, while not suppressing the HIV-1 p24 production from latent HIV-1-infected ACH-2 cells after stimulation with phorbol 12-myristate 13-acetate. DDSD also inhibited the synthesis of HIV-1 proviral DNA at 20-50 microM, not only 1 h but also 24 h after HIV-1 infection. Taken together, DDSD is a potent inhibitor of HIV-1 production, and may become a unique leading compound for chemotherapy of acquired immunodeficiency syndrome. 相似文献