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排序方式: 共有575条查询结果,搜索用时 671 毫秒
141.
Sato Y Hatta M Karim MF Sawa T Wei FY Sato S Magnuson MA Gonzalez FJ Tomizawa K Akaike T Yoshizawa T Yamagata K 《The Journal of biological chemistry》2012,287(27):23236-23245
142.
Kozlowski PM Kamachi T Kumar M Yoshizawa K 《Journal of biological inorganic chemistry》2012,17(2):293-300
Density functional theory analysis was performed to elucidate the impact of one-electron reduction upon the initial step of
adenosylcobalamin-dependent enzymatic catalysis. The transition state (TS) corresponding to the Co–C bond cleavage and subsequent
hydrogen abstraction from the substrate was located. The intrinsic reaction coordinate calculations predicted that the reaction
consisting of Co–C5′ bond cleavage in [CoIII(corrin•)]–Rib (where Rib is ribosyl) and hydrogen-atom abstraction from the CH3–CH2–CHO substrate occurs in a concerted fashion. The computed activation energy barrier of the reaction (15.0 kcal/mol) was lowered
by approximately 54.5% in comparison with the reaction involving the positively charged cofactor model (Im–[CoIII(corrin)]–Rib+, where Im is imidazole; energy barrier = 33.0 kcal/mol). The Im base was detached during the TS search in the reaction involving
the one-electron-reduced analogue. Thus, to compare the energetics of the two reactions, the axial Im ligand detachment energy
for the Im–[CoIII(corrin•)]–Rib model was computed [7.6 kcal/mol (gas phase); 4.6 kcal/mol (water)]. Consequently, the effective activation energy
barrier for the reaction mediated by the Im-off [CoIII(corrin•)]–Rib was estimated to be 22.6 kcal/mol, which implied an overall 31.5% reduction in the energetic demands of the reaction.
Considering that the lengthened Co–Naxial bond has been observed in X-ray crystal structure studies of B12-dependent mutases, the catalytic impact induced by one-electron reduction of the cofactor is expected to be higher in the
presence of the enzymatic environment. 相似文献
143.
Yoshizawa S 《Biochimie》2012,94(7):1588-1594
Micro and nanotechnologies have originally contributed to engineering, especially in electronics. These technologies enable fabrication and assembly of materials at micrometer and nanometer scales and the manipulation of nano-objects. The power of these technologies has now been exploited in analyzes of biologically relevant molecules. In this review, the use of micro and nanotechnological tools in RNA research is described. 相似文献
144.
Kayoko Sasaki-Fukatsu Ryuichi Koga Naruo Nikoh Kazunori Yoshizawa Shinji Kasai Minoru Mihara Mutsuo Kobayashi Takashi Tomita Takema Fukatsu 《Applied microbiology》2006,72(11):7349-7352
The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria. The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation “Candidatus Riesia pediculicola” for the louse symbionts. 相似文献
145.
Kita-Tsukamoto K Wada M Yao K Kamiya A Yoshizawa S Uchiyama N Kogure K 《FEMS microbiology letters》2006,258(2):320-320
To rapidly identify natural isolates of marine bioluminescent bacteria, we developed amplified ribosomal DNA restriction analysis (ARDRA) methods. ARDRA, which is based on the restriction patterns of 16S rRNA gene digested with five enzymes (EcoRI, DdeI, HhaI, HinfI, RsaI), clearly distinguished the 14 species of marine bioluminescent bacteria currently known, which belong to the genera Vibrio, Photobacterium, and Shewanella. When we applied ARDRA to 129 natural isolates from two cruises in Sagami Bay, Japan, 127 were grouped into six ARDRA types with distinctive restriction patterns; these isolates represented the bioluminescent species, P. angustum, P. leiognathi, P. phosphoreum, S. woodyi, V. fischeri, and V. harveyi. The other two isolates showing unexpected ARDRA patterns turned out to have 16S rRNA gene sequences similar to P. leiognathi and P. phosphoreum. Nevertheless, ARDRA provides a simple and fairly robust means for rapid identification of the natural isolates of marine bioluminescent bacteria, and is therefore useful in studying their diversity. 相似文献
146.
The spermatogonial transplantation system was applied to evaluate stem cell kinetics and niche quality and to produce gene-modified animals using the stem cells after homologous recombination-based selection. This study was designed to determine whether the transplanted spermatogonia were able to proliferate and differentiate in male rats expressing the c-myc transgene under control of the human metallothionein IIA promoter (MT-myc Tg rats). Donor testicular cells were prepared from heterozygous chicken beta actin (CAG)/enhanced green fluorescent protein (EGFP)-transgenic rats (EGFP Tg rats) during the second week after birth and injected into the seminiferous tubules of the MT-myc Tg rats (line-A and -B; both subfertile) or rats pretreated with busulfan to remove endogenous spermatogonia. Three to four months after transplantation, cell colonies with EGFP fluorescence were detected in 36% (4/11), 40% (8/20), and 71% (5/7) of the transplanted testes in line-A MT-myc Tg rats, line-B MT-myc Tg rats, and busulfan-treated rats, respectively. No EGFP-positive colonies were detected when wild-type male rats were used as recipients (0/7; testis-basis). The histopathological and immunofluorescent examination of the serial sections from the transplanted testes showed normal spermatogenesis of the donor spermatogonia, but atrophy of the recipient seminiferous tubules. Microinsemination with round spermatids and mature spermatozoa derived from EGFP-positive testes in line-A rats resulted 26% (10/39 transferred) and 23% (11/48 transferred) full-term offspring, respectively. Thus, the MT-myc Tg male rats were suitable as potent recipients for spermatogonial transplantation without any chemical pretreatment to remove the endogenous spermatogonia. 相似文献
147.
148.
Janice M. Yoshizawa Aaron W. Fay Chi Chung Lee Yilin Hu Markus Walter Ribbe 《Journal of biological inorganic chemistry》2010,15(3):421-428
The cofactors of Mo-, V-, Fe-dependent nitrogenases are believed to be highly homologous in structure despite the different
types of heterometals (Mo, V, and Fe) they contain. Previously, a precursor form of the FeMo cofactor (FeMoco) was captured
on NifEN, a scaffold protein for FeMoco biosynthesis. This all-Fe precursor closely resembles the Fe/S core structure of the
FeMoco and, therefore, could reasonably serve as a precursor for all nitrogenase cofactors. Here, we report the heterologous
incorporation of V and Fe into the NifEN-associated FeMoco precursor. EPR and activity analyses indicate that V and Fe can
be inserted at much reduced efficiencies compared with Mo, and incorporation of both V and Fe is enhanced in the presence
of homocitrate. Further, native polyacrylamide gel electrophoresis experiments suggest that NifEN undergoes a significant
conformational rearrangement upon metal insertion, which allows the subsequent NifEN–MoFe protein interactions and the transfer
of the cofactor between the two proteins. The combined outcome of these in vitro studies leads to the proposal of a selective
mechanism that is utilized in vivo to maintain the specificity of heterometals in nitrogenase cofactors, which is likely accomplished
through the redox regulation of metal mobilization by different Fe proteins (encoded by nifH, vnfH, and anfH, respectively), as well as the differential interactions between these Fe proteins and their respective scaffold proteins
(NifEN and VnfEN) in the Mo-, V-, and Fe-dependent nitrogenase systems. 相似文献
149.
150.
Kaori Ohtani Hideki Hirakawa Kousuke Tashiro Satoko Yoshizawa Satoru Kuhara Tohru Shimizu 《Anaerobe》2010,16(3):258-264
Clostridium perfringens, a Gram-positive anaerobic pathogen, is a causative agent of human gas gangrene that leads to severe rapid tissue destruction and can cause death within hours unless treated immediately. Production of several toxins is known to be controlled by the two-component VirR/VirS system involving a regulatory RNA (VR-RNA) in C. perfringens. To elucidate the precise regulatory network governed by VirR/VirS and VR-RNA, a series of microarray screening using VirR/VirS and VR-RNA-deficient mutants was performed. Finally, by qRT-PCR analysis, 147 genes (30 single genes and 21 putative operons) were confirmed to be under the control of the VirR/VirS-VR-RNA regulatory cascade. Several virulence-related genes for alpha-toxin, kappa-toxin, hyaluronidases, sialidase, and capsular polysaccharide synthesis were found. Furthermore, some genes for catalytic enzymes, various genes for transporters, and many genes for energy metabolism were also found to be controlled by the cascade. Our data indicate that the VirR/VirS-VR-RNA system is a global gene regulator that might control multiple cellular functions to survive and multiply in the host, which would turn out to be a lethal flesh-eating infection. 相似文献