全文获取类型
收费全文 | 1513篇 |
免费 | 82篇 |
国内免费 | 2篇 |
出版年
2023年 | 15篇 |
2022年 | 41篇 |
2021年 | 73篇 |
2020年 | 37篇 |
2019年 | 40篇 |
2018年 | 75篇 |
2017年 | 47篇 |
2016年 | 58篇 |
2015年 | 76篇 |
2014年 | 100篇 |
2013年 | 90篇 |
2012年 | 101篇 |
2011年 | 75篇 |
2010年 | 52篇 |
2009年 | 54篇 |
2008年 | 77篇 |
2007年 | 78篇 |
2006年 | 55篇 |
2005年 | 50篇 |
2004年 | 58篇 |
2003年 | 43篇 |
2002年 | 29篇 |
2001年 | 23篇 |
2000年 | 32篇 |
1999年 | 17篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 16篇 |
1991年 | 15篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有1597条查询结果,搜索用时 968 毫秒
131.
M. Y. Hossain Z. F. Ahmed A. B. M S. Islam S. Jasmine J. Ohtomi 《Zeitschrift fur angewandte Ichthyologie》2010,26(4):550-553
The present study aims to estimate the size at first sexual maturity and fecundity for female Gudusia chapra from the lower Ganges River, northwestern Bangladesh. A total of 250 female specimens, 3.60–13.70 cm in standard length (SL) and 1.00–43.60 g in body weight (BW), were collected during March–August 2006. The gonadosomatic index (GSI) for females was calculated by the equation, GSI (%) = (GW/BW) × 100. The size at first sexual maturity of females was estimated by the relationship between their gonadosomatic index and standard length. The specimen larger (≥8.00 cm in SL) than first size at sexual maturity was used for the estimation of fecundity. The size at first sexual maturity for female G. chapra was considered to be 8.00 cm SL in the Ganges River. The mean total fecundity was 20200 ± 6500 and ranged from 10800 to 36200. This study should be useful for fisheries biologists/managers to impose adequate regulations for sustainable‐fishery management in the Ganges River and elsewhere in Bangladesh. 相似文献
132.
133.
G. Taret M. Sevilla V. Wornoayporn A. Islam S. Ahmad C. Caceres A. S. Robinson M. J. B. Vreysen 《Journal of Applied Entomology》2010,134(3):207-215
The codling moth Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is a serious pest of pome fruit worldwide and the sterile insect technique (SIT) provides an environmentally acceptable approach for its control. As the pest is present in both the southern and northern hemispheres it would be possible for a rearing facility in the northern hemisphere to supply sterile moths to an SIT programme in the southern hemisphere during the northern winter and vice versa. This could greatly improve the economics of moth production and the running costs of rearing facilities. However in order to develop this concept, it is important to assess if populations of codling moth from different geographical regions share mating compatibility. Twelve different laboratory and field populations from both hemispheres were sampled and field cage bisexual mating compatibility tests were carried out between selected combinations. The index of sexual isolation (ISI) and the female and male relative performance index (FRPI and MRPI, respectively) were calculated for each mating combination. In only two of the combinations was there a slight but significant deviation from random mating. There were also some significant differences in mating duration between the homotypic matings and the duration of a particular homotypic mating seemed to depend on the origin of the other population in the cage. It was concluded that there exist no barriers to mating between populations of codling moth from many parts of the world and that it would be feasible for sterile moths to be shipped from one rearing facility to SIT programmes in other parts of the world. 相似文献
134.
Md. Tofazzal Islam Yukiharu Fukushi 《World journal of microbiology & biotechnology》2010,26(7):1163-1170
We observed that 2,4-diacetylphloroglucinol (DAPG), a major antimicrobial metabolite produced by a rhizoplane bacterium Pseudomonas fluorescens ECO-001 inhibited mycelial growth of a damping-off phytopathogen Aphanomyces
cochlioides AC-5 through inducing excessive branching and curling in the hyphae. This study aimed to unravel the mode of action of DAPG
caused excessive branching, curling and growth inhibition of AC-5 hyphae by detecting localized changes in the cortical filamentous
actin (F-actin) organization by rhodamine-conjugated phalloidin. Confocal laser scanning microscopic observations revealed
that both living bacteria and DAPG severely disrupted the organization of F-actin in the A. cochlioides hyphae in a similar manner. Furthermore, an inhibitor of F-actin polymerization, latrunculin B also induced similar growth
inhibition, excessive branching and caused disruption of F-actin in the AC-5 hyphae. Our results suggested that growth inhibition
and excessive branching induced in A. cochlioides by DAPG is likely to be linked to the disruption of F-actin cytoskeleton in the affected hyphae. This is the first report
on disruption of cytoskeleton of a eukaryotic A. cochlioides by a well-known biocontrol metabolite DAPG secreted from a prokaryotic bacterium ECO-001. 相似文献
135.
Md. Tofazzal Islam 《World journal of microbiology & biotechnology》2010,26(4):629-637
The biocontrol bacterium Lysobacter sp. SB-K88 suppresses damping-off disease in sugar beet and spinach caused by Aphanomyces cochlioides and Pythium sp. through characteristic plant colonization and antibiosis against the pathogens. This study aimed to unravel further details on mode of antagonism of SB-K88 against a damping-off pathogen A. cochlioides AC-5. The SB-K88 substantially inhibited growth and decomposed AC-5 mycelia and suppressed the release of zoospores from the hyphae. The excised root tips of sugar beet seedlings from seeds previously inoculated with SB-K88 were less attractive to AC-5 zoospores. Although aerial growth was not affected, however, root hairs of SB-K88 inoculated sugar beet seedlings were remarkably shorter and thicker than those of uninoculated control. When exposed to zoospores, the SB-K88 inhibited motility of zoospores and/or caused lysis, and then aggregated around the dead cystospores or lysed residues within 3–6 h likely to be micro-predatory behavior to a eukaryotic organism. Confocal laser scanning microscopic analysis revealed that number of lipid bodies and activities of mitochondria were markedly increased in the affected hyphae compared with control hyphae as visualized by established vital stains. Taken together, these results suggest that Lysobacter sp. SB-K88 suppresses damping-off diseases through exerting multifaceted antagonistic effects against the peronosporomycetes. 相似文献
136.
Cecilia Andrésen Shah Jalal Daniel Aili Yi Wang Sohidul Islam Anngelica Jarl Bo Liedberg Bengt Wretlind Lars‐Göran Mårtensson Maria Sunnerhagen 《Protein science : a publication of the Protein Society》2010,19(4):680-692
The self‐assembling MexA‐MexB‐OprM efflux pump system, encoded by the mexO operon, contributes to facile resistance of Pseudomonas aeruginosa by actively extruding multiple antimicrobials. MexR negatively regulates the mexO operon, comprising two adjacent MexR binding sites, and is as such highly targeted by mutations that confer multidrug resistance (MDR). To understand how MDR mutations impair MexR function, we studied MexR‐wt as well as a selected set of MDR single mutants distant from the proposed DNA‐binding helix. Although DNA affinity and MexA‐MexB‐OprM repression were both drastically impaired in the selected MexR‐MDR mutants, MexR‐wt bound its two binding sites in the mexO with high affinity as a dimer. In the MexR‐MDR mutants, secondary structure content and oligomerization properties were very similar to MexR‐wt despite their lack of DNA binding. Despite this, the MexR‐MDR mutants showed highly varying stabilities compared with MexR‐wt, suggesting disturbed critical interdomain contacts, because mutations in the DNA‐binding domains affected the stability of the dimer region and vice versa. Furthermore, significant ANS binding to MexR‐wt in both free and DNA‐bound states, together with increased ANS binding in all studied mutants, suggest that a hydrophobic cavity in the dimer region already shown to be involved in regulatory binding is enlarged by MDR mutations. Taken together, we propose that the biophysical MexR properties that are targeted by MDR mutations—stability, domain interactions, and internal hydrophobic surfaces—are also critical for the regulation of MexR DNA binding. 相似文献
137.
138.
Hirai K Martinkova M Igarashi J Saiful I Yamauchi S El-Mashtoly S Kitagawa T Shimizu T 《Journal of inorganic biochemistry》2007,101(8):1172-1179
Heme-regulated eIF2alpha kinase (HRI) is an important enzyme that modulates protein synthesis during cellular emergency/stress conditions, such as heme deficiency in red cells. It is essential to identify the heme axial ligand(s) and/or binding sites to establish the heme regulation mechanism of HRI. Previous reports suggest that a His residue in the N-terminal region and a Cys residue in the C-terminal region trans to the His are axial ligands of the heme. Moreover, mutational analyses indicate that a residue located in the kinase insertion (KI) domain between Kinase I and Kinase II domains in the C-terminal region is an axial ligand. In the present study, we isolate the KI domain of mouse HRI and employ site-directed mutagenesis to identify the heme axial ligand. The optical absorption spectrum of the Fe(III) hemin-bound wild-type KI displays a broad Soret band at around 373nm, while that of the Fe(II) heme-bound protein contains a band at 422nm. Spectral titration studies conducted for both the Fe(III) hemin and Fe(II) heme complexes with KI support a 1:1 stoichiometry of heme iron to protein. Resonance Raman spectra of Fe(III) hemin-bound KI suggest that thiol is the axial ligand in a 5-coordinate high-spin heme complex as a major form. Electron spin resonance (ESR) spectra of Fe(III) hemin-bound KI indicate that the axial ligands are OH(-) and Cys. Since Cys385 is the only cysteine in KI, the residue was mutated to Ser, and its spectral characteristics were analyzed. The Soret band position, heme spectral titration behavior and ESR parameters of the Cys385Ser mutant were markedly different from those of wild-type KI. Based on these spectroscopic findings, we conclude that Cys385 is an axial ligand of isolated KI. 相似文献
139.
Clostridium thermocellum, a cellulolytic, thermophilic anaerobe, has potential for commercial exploitation in converting fibrous biomass to ethanol.
However, ethanol concentrations above 1% (w/v) are inhibitory to growth and fermentation, and this limits industrial application of the organism. Recent work with ethanol-adapted
strains suggested that protein changes occurred during ethanol adaptation, particularly in the membrane proteome. A two-stage
Bicine-doubled sodium dodecyl sulfate-polyacrylamide gel electrophoresis protocol was designed to separate membrane proteins
and circumvent problems associated with membrane protein analysis using traditional gel-based proteomics approaches. Wild-type
and ethanol-adapted C. thermocellum membranes displayed similar spot diversity and approximately 60% of proteins identified from purified membrane fractions
were observed to be differentially expressed in the two strains. A majority (73%) of differentially expressed proteins were
down-regulated in the ethanol-adapted strain. Based on putative identifications, a significant proportion of these down-regulated
proteins were involved with carbohydrate transport and metabolism. Approximately one-third of the up-regulated proteins in
the ethanol-adapted species were associated with chemotaxis and signal transduction. Overall, the results suggested that membrane-associated
proteins in the ethanol-adapted strain are either being synthesized in lower quantities or not properly incorporated into
the cell membrane. 相似文献
140.
The brefeldin A-inhibited guanine nucleotide-exchange protein, BIG2, regulates the constitutive release of TNFR1 exosome-like vesicles 总被引:1,自引:0,他引:1
Islam A Shen X Hiroi T Moss J Vaughan M Levine SJ 《The Journal of biological chemistry》2007,282(13):9591-9599
The type I, 55-kDa tumor necrosis factor receptor (TNFR1) is released from cells to the extracellular space where it can bind and modulate TNF bioactivity. Extracellular TNFR1 release occurs by two distinct pathways: the inducible proteolytic cleavage of TNFR1 ectodomains and the constitutive release of full-length TNFR1 in exosome-like vesicles. Regulation of both TNFR1 release pathways appears to involve the trafficking of cytoplasmic TNFR1 vesicles. Vesicular trafficking is controlled by ADP-ribosylation factors (ARFs), which are active in the GTP-bound state and inactive when bound to GDP. ARF activation is enhanced by guanine nucleotide-exchange factors that catalyze replacement of GDP by GTP. We investigated whether the brefeldin A (BFA)-inhibited guanine nucleotide-exchange proteins, BIG1 and/or BIG2, are required for TNFR1 release from human umbilical vein endothelial cells. Effects of specific RNA interference (RNAi) showed that BIG2, but not BIG1, regulated the release of TNFR1 exosome-like vesicles, whereas neither BIG2 nor BIG1 was required for the IL-1beta-induced proteolytic cleavage of TNFR1 ectodomains. BIG2 co-localized with TNFR1 in diffusely distributed cytoplasmic vesicles, and the association between BIG2 and TNFR1 was disrupted by BFA. Consistent with the preferential activation of class I ARFs by BIG2, ARF1 and ARF3 participated in the extracellular release of TNFR1 exosome-like vesicles in a nonredundant and additive fashion. We conclude that the association between BIG2 and TNFR1 selectively regulates the extracellular release of TNFR1 exosome-like vesicles from human vascular endothelial cells via an ARF1- and ARF3-dependent mechanism. 相似文献