全文获取类型
收费全文 | 2068篇 |
免费 | 117篇 |
专业分类
2185篇 |
出版年
2022年 | 24篇 |
2021年 | 18篇 |
2020年 | 11篇 |
2019年 | 20篇 |
2018年 | 34篇 |
2017年 | 16篇 |
2016年 | 34篇 |
2015年 | 51篇 |
2014年 | 56篇 |
2013年 | 123篇 |
2012年 | 111篇 |
2011年 | 99篇 |
2010年 | 60篇 |
2009年 | 53篇 |
2008年 | 86篇 |
2007年 | 83篇 |
2006年 | 95篇 |
2005年 | 75篇 |
2004年 | 76篇 |
2003年 | 80篇 |
2002年 | 68篇 |
2001年 | 74篇 |
2000年 | 83篇 |
1999年 | 63篇 |
1998年 | 28篇 |
1997年 | 31篇 |
1996年 | 28篇 |
1995年 | 26篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 50篇 |
1991年 | 41篇 |
1990年 | 46篇 |
1989年 | 34篇 |
1988年 | 44篇 |
1987年 | 23篇 |
1986年 | 18篇 |
1985年 | 38篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 17篇 |
1981年 | 19篇 |
1980年 | 12篇 |
1979年 | 18篇 |
1978年 | 30篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1975年 | 8篇 |
1968年 | 7篇 |
1966年 | 9篇 |
排序方式: 共有2185条查询结果,搜索用时 15 毫秒
991.
992.
Yoko Ikehara Kazuhito Arai Nayuta Furukawa Tadashi Ohno Tatsuya Miyake Shinya Fushinobu Masahiro Nakajima Akimasa Miyanaga Hayao Taguchi 《The Journal of biological chemistry》2014,289(45):31550-31564
For Thermus caldophilus
l-lactate dehydrogenase (TcLDH), fructose 1,6-bisphosphate (FBP) reduced the pyruvate S0.5 value 103-fold and increased the Vmax value 4-fold at 30 °C and pH 7.0, indicating that TcLDH has a much more T state-sided allosteric equilibrium than Thermus thermophilus
l-lactate dehydrogenase, which has only two amino acid replacements, A154G and H179Y. The inactive (T) and active (R) state structures of TcLDH were determined at 1.8 and 2.0 Å resolution, respectively. The structures indicated that two mobile regions, MR1 (positions 172–185) and MR2 (positions 211–221), form a compact core for allosteric motion, and His179 of MR1 forms constitutive hydrogen bonds with MR2. The Q4(R) mutation, which comprises the L67E, H68D, E178K, and A235R replacements, increased Vmax 4-fold but reduced pyruvate S0.5 only 5-fold in the reaction without FBP. In contrast, the P2 mutation, comprising the R173Q and R216L replacements, did not markedly increase Vmax, but 102-reduced pyruvate S0.5, and additively increased the FBP-independent activity of the Q4(R) enzyme. The two types of mutation consistently increased the thermal stability of the enzyme. The MR1-MR2 area is a positively charged cluster, and its center approaches another positively charged cluster (N domain cluster) across the Q-axis subunit interface by 5 Å, when the enzyme undergoes the T to R transition. Structural and kinetic analyses thus revealed the simple and unique allosteric machinery of TcLDH, where the MR1-MR2 area pivotally moves during the allosteric motion and mediates the allosteric equilibrium through electrostatic repulsion within the protein molecule. 相似文献
993.
Ting Lei Zheng Huang Nobuhiko Ohno Bao Wu Takashi Sakoh Yurika Saitoh Ikuo Saiki Shinichi Ohno 《The journal of histochemistry and cytochemistry》2014,62(4):251-264
The microenvironments of organs with blood flow affect the metabolic profiles of cancer cells, which are influenced by mitochondrial functions. However, histopathological analyses of these aspects have been hampered by technical artifacts of conventional fixation and dehydration, including ischemia/anoxia. The purpose of this study was to combine the in vivo cryotechnique (IVCT) with fluorescent protein expression, and examine fluorescently labeled mitochondria in grafted melanoma tumors. The intensity of fluorescent proteins was maintained well in cultured B16-BL6 cells after cryotechniques followed by freeze-substitution (FS). In the subcutaneous tumors of mitochondria-targeted DsRed2 (mitoDsRed)-expressing cells, a higher number of cancer cells were found surrounding the widely opened blood vessels that contained numerous erythrocytes. Such blood vessels were immunostained positively for immunoglobulin M and ensheathed by basement membranes. MitoDsRed fluorescence was detected in scattering melanoma cells using the IVCT-FS method, and the total mitoDsRed volume in individual cancer cells was significantly decreased with the expression of markers of hypoxia. MitoDsRed was frequently distributed throughout the cytoplasm and in processes extending along basement membranes. IVCT combined with fluorescent protein expression is a useful tool to examine the behavior of fluorescently labeled cells and organelles. We propose that the mitochondrial volume is dynamically regulated in the hypoxic microenvironment and that mitochondrial distribution is modulated by cancer cell interactions with basement membranes. 相似文献
994.
Takao Hikita Akihisa Ohno Masato Sawada Haruko Ota Kazunobu Sawamoto 《Journal of neurochemistry》2014,128(6):790-797
New neurons generated in the ventricular‐subventricular zone in the post‐natal brain travel toward the olfactory bulb by using a collective cell migration process called ‘chain migration.’ These new neurons show a saltatory movement of their soma, suggesting that each neuron cycles through periods of ‘rest’ during migration. Here, we investigated the role of the resting neurons in chain migration using post‐natal mouse brain, and found that they undergo a dynamic morphological change, in which a deep indentation forms in the cell body. Inhibition of Rac1 activity resulted in less indentation of the new neurons in vivo. Live cell imaging using a Förster resonance energy transfer biosensor revealed that Rac1 was activated at the sites of contact between actively migrating and resting new neurons. On the cell surface of resting neurons, Rac1 activation coincided with the formation of the indentation. Furthermore, Rac1 knockdown prevented the indentation from forming and impaired migration along the resting neurons. These results suggest that Rac1 regulates a morphological change in the resting neurons, which allows them to serve as a migratory scaffold, and thereby non‐cell‐autonomously promotes chain migration.
995.
Three hundred and forty-nine autopsy cases of schistosomiasis japonica were divided into two groups, based on the pathomorphology. Frequent regressive hepatic lesions such as active schistosomal lesion and destruction of limiting plates characterized the first group. The second group showed reparative hepatic lesions such as regeneration of the collapsed parenchyma, newly formed limiting plates and subsequent narrowing and disappearance of fibrous septa. Complications of liver cirrhosis and hepatocellular carcinoma related to viral hepatitis B and/or C also increased. Clonorchiasis was consistently found in both groups. 相似文献
996.
Cytokine regulation in experimentally-induced Schistosoma japonicum egg granuloma formation 总被引:3,自引:0,他引:3
The formation of granulomas in host tissues in response to trapped Schistosoma japonicum eggs is central to the etiology of schistosomiasis. However, analysis of the host hypersensitivity reactions that result in granuloma formation, in schistosome infection, is not without difficulty. This is due, in part, to the fact that the parasites continuously deposit their eggs as clusters. In order to synchronize host reactions, we established an experimental model of hepatic granuloma formation whereby in vitro laid schistosome eggs are implanted directly into normal and cytokine-deficient mice livers. This model, validated by comparison with an infection model, was used to analyze cytokine regulation of granuloma formation around S. japonicum eggs. Combined models of implantation and cercarial infection were also studied. With special reference to IL-4, IL-13, IFN-γ and IL-18, our in vitro schistosome egg implantation model has shed new light on the roles of cytokines in both the acute and chronic stages of schistosome egg-induced granuloma formation. 相似文献
997.
Nobutake Akiyama Yuji Ohno Yosinobu Manome 《Biochemical and biophysical research communications》2009,381(4):612-618
Several fusion proteins of mouse Interleukins (mILs) and the enhanced green fluorescent protein (EGFP) were expressed in fibroblast and epithelial cells. Among these proteins, the mIL-31 derivative was the most efficiently secreted into the medium in a N-glycosylation-dependent manner. From the analysis of deletion mutants, the minimal structure for constitutive secretions consisted of a signal peptide and N-glycosylation. Introduction of the signal sequence from mIL-31 to human p53 protein failed to secrete the products, but further addition of the N-glycosylation site resulted in constitutive secretion of biologically active p53 protein into the medium in the N-glycosylated form. In this report, we showed the importance of N-glycosylation for constitutive protein secretions, especially using non-polarized cells. 相似文献
998.
Hiroki Shimada Kei-Ichi Hirai Eriko Simamura Toshihisa Hatta Hiroki Iwakiri Keiji Mizuki Taizo Hatta Tatsuya Sawasaki Satoko Matsunaga Yaeta Endo Shigeomi Shimizu 《The Journal of biological chemistry》2009,284(42):28642-28649
Paraquat (PQ), a herbicide used worldwide, causes fatal injury to organs upon high dose ingestion. Treatments for PQ poisoning are unreliable, and numerous deaths have been attributed inappropriate usage of the agent. It is generally speculated that a microsomal drug-metabolizing enzyme system is responsible for PQ toxicity. However, recent studies have demonstrated cytotoxicity via mitochondria, and therefore, the cytotoxic mechanism remains controversial. Here, we demonstrated that mitochondrial NADH-dependent PQ reductase containing a voltage-dependent anion channel 1 (VDAC1) is responsible for PQ cytotoxicity. When mitochondria were incubated with NADH and PQ, superoxide anion (O2˙̄) was produced, and the mitochondria ruptured. Outer membrane extract oxidized NADH in a PQ dose-dependent manner, and oxidation was suppressed by VDAC inhibitors. Zymographic analysis revealed the presence of VDAC1 protein in the oxidoreductase, and the direct binding of PQ to VDAC1 was demonstrated using biotinylated PQ. VDAC1-overexpressing cells showed increased O2˙̄ production and cytotoxicity, both of which were suppressed in VDAC1 knockdown cells. These results indicated that a VDAC1-containing mitochondrial system is involved in PQ poisoning. These insights into the mechanism of PQ poisoning not only demonstrated novel physiological functions of VDAC protein, but they may facilitate the development of new therapeutic approaches.Paraquat (PQ2; methyl viologen, 1,1′-dimethyl-4,4′-bipyridinium dichloride) is an effective herbicide used in more than 120 countries (1). Although it is classified as a low hazard compound, PQ is hazardous when used improperly and has been found responsible for thousands of deaths worldwide because of intentional overdose and high levels of occupational and accidental exposure especially in developing countries (1). Direct exposure to PQ causes severe irritation to the eyes and skin, and ingestion of concentrated products may result in fatal injury to lungs because of edema, hemorrhage, and subsequent fibrosis as well as damage to other organs (2). Additionally, PQ has emerged as a risk factor for Parkinson disease (3). The acute toxicity of PQ in mammals is mediated by reactive oxygen species (ROS) produced by a cyclic oxidation-reduction reaction (4). It is generally speculated that NADPH-cytochrome P450 reductase in microsomal drug-metabolizing enzyme systems is responsible for the production of ROS (5). However, we previously observed that the initial ultrastructural alterations associated with PQ exposure occurred only in mitochondria and not in the endoplasmic reticulum in pulmonary cells in vivo (6) and in vitro (7). In addition, several reports have suggested the cytotoxicity of PQ via mitochondrial dysfunction (8–10). Despite the development of a number of treatments for PQ poisoning, the efficacy and reliability of currently available treatments have remained limited because of an insufficient understanding of PQ cytotoxicity (2).We recently discovered that active NADH-dependent oxidoreductase located on the mitochondrial outer membrane reduced PQ to a radical form that spontaneously formed superoxide anion (O2˙̄) and destroyed mitochondria (11–13). Furthermore, we demonstrated that 1) PQ was initially metabolized to monopyridone in the cytosol and subsequently hydroxylated by the microsomes and 2) the induction of drug-metabolizing enzymes and the administration of a ROS scavenger reduced PQ toxicity in mice (11, 14). These results indicate that the mitochondrial system, not the microsomal system, is responsible for PQ toxicity. We verified that enzymes in the electron transport chain and NADH-cytochrome b5 reductase, an NADH-dependent oxidoreductase in the outer membrane, were not involved in this reaction (11, 12). A voltage-dependent anion channel (VDAC), an abundant pore-forming protein in the outer membrane, exerts numerous physiological functions as a channel; it regulates both the metabolite flux of mitochondria and transmembrane potential, and plays a role in apoptosis. Recently, it was reported that NADH regulates VDAC function (15), and an isoform of VDAC localized in the plasma membrane possesses NADH-ferricyanide reductase activity (16). Therefore, we attempted to determine whether or not NADH-PQ oxidoreductase on mitochondria is responsible for PQ cytotoxicity and if VDAC participates in this activity. 相似文献
999.
1000.
Ken-ichiro Inoue Hirohisa Takano Eiko Koike Rie Yanagisawa Toshio Oda Hiroshi Tamura Yoshiyuki Adachi Ken-ichi Ishibashi Naohito Ohno 《Respiratory research》2009,10(1):68