全文获取类型
收费全文 | 900篇 |
免费 | 91篇 |
专业分类
991篇 |
出版年
2023年 | 6篇 |
2022年 | 26篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 71篇 |
2014年 | 46篇 |
2013年 | 72篇 |
2012年 | 90篇 |
2011年 | 74篇 |
2010年 | 25篇 |
2009年 | 42篇 |
2008年 | 50篇 |
2007年 | 45篇 |
2006年 | 54篇 |
2005年 | 44篇 |
2004年 | 44篇 |
2003年 | 35篇 |
2002年 | 31篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1966年 | 1篇 |
1956年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有991条查询结果,搜索用时 17 毫秒
81.
Flavio M. Lopes Karla A. Batista Gustavo L. A. Batista Sydnei Mitidieri Luiz Artur M. Bataus Kátia F. Fernandes 《World journal of microbiology & biotechnology》2010,26(7):1155-1161
Three bacterial strains have been isolated from soil in which soybean had been continuously cropped and treated with Opera®, a fungicide containing epoxyconazole and pyraclostrobin. The three strains (1,805, 2,801 and 3,803), obtained from soil at 80–100 cm depth, were selected on medium containing 0.03% Opera®. Morphological examination revealed that the strains were Gram-negative, and two of them (1,805 and 2,801) exhibited polymorphism. The growth profiles demonstrated that 1,805 and 3,803 were more efficient growing in the presence of Opera® than 2,801. Maximum growth was reached between 24 and 48 h, however, 2,801 was not able to survive after this period. The total protein content produced by 1,805, 2,801 and 3,803 in liquid selective medium containing Opera® were 111.0 ± 0.02, 80.0 ± 0.05 and 130.5 ± 0.07 μg/ml, respectively. According to its biochemical and molecular features, strain 1,805 was identified as Klebsiella sp. On the basis of the characteristics presented (facultative anaerobic nature, polymorphic character and capacity of growing in the presence of Opera®) strain 1,805 seems to be able to degrade the epoxyconazole and pyraclostrobin. 相似文献
82.
Alcides AP Brazier JS Pinto LJ Balassiano IT Boente RF de Paula GR Ferreira EO Avelar KE Miranda KR Ferreira MC Domingues RM 《Antonie van Leeuwenhoek》2007,92(1):53-59
A total of 35 Brazilian isolates of Clostridium difficile from faecal stools and four isolates from hospital environments were analyzed by PCR ribotyping. A whole cell protein profile
(as an alternative for serogrouping), in vitro toxin production and susceptibility to vancomycin, metronidazole and clindamycin
were also investigated. All strains were typeable by both phenotypic and genotypic methods, and a total of 13 different PCR
ribotypes were identified, of which seven (132, 133, 134, 135, 136, 142 and 143) were considered new types and accounted for
78.5% of all samples evaluated (including hospital environments). A non-toxigenic C. difficile PCR ribotype 133 was detected in all children groups examined (inpatients, outpatients and healthy children), whilst toxigenic
PCR ribotypes 015, 131, 134 and 135 were associated mostly with symptomatic children. Serogroups G and D were disseminated
both in patients from the community and from the pediatric hospital, with group G prevalent among outpatient children. All
strains were susceptible to vancomycin and metronidazole but high levels of resistance to clindamycin were found, especially
among serogroups G and D. Co-existence of different ribotypes and serogroups in the same individual was observed. The new
seven ribotypes found in this investigation may represent strains characteristic of this region of Brazil. 相似文献
83.
Functional and crystal structure analysis of active site adaptations of a potent anti-angiogenic human tRNA synthetase 总被引:1,自引:0,他引:1
Yang XL Guo M Kapoor M Ewalt KL Otero FJ Skene RJ McRee DE Schimmel P 《Structure (London, England : 1993)》2007,15(7):793-805
Higher eukaryote tRNA synthetases have expanded functions that come from enlarged, more differentiated structures that were adapted to fit aminoacylation function. How those adaptations affect catalytic mechanisms is not known. Presented here is the structure of a catalytically active natural splice variant of human tryptophanyl-tRNA synthetase (TrpRS) that is a potent angiostatic factor. This and related structures suggest that a eukaryote-specific N-terminal extension of the core enzyme changed substrate recognition by forming an active site cap. At the junction of the extension and core catalytic unit, an arginine is recruited to replace a missing landmark lysine almost 200 residues away. Mutagenesis, rapid kinetic, and substrate binding studies support the functional significance of the cap and arginine recruitment. Thus, the enzyme function of human TrpRS has switched more to the N terminus of the sequence. This switch has the effect of creating selective pressure to retain the N-terminal extension for functional expansion. 相似文献
84.
Peña-Rico Miguel A. Bravo-D Humberto R. Roldan-Sabino Crisanto Castro-Cerritos Karla V. Huerta-Heredia Ariana Navarro-Mtz A. Karin 《Antonie van Leeuwenhoek》2022,115(1):89-102
Antonie van Leeuwenhoek - Bacillus thuringiensis is the major bioinsecticide worldwide produced due to the Cry protein activity. Several studies have been done to improve the... 相似文献
85.
Hydrobiologia - Theory predicts that species can only coexist if they are sufficiently different in their resource and/or microhabitat utilization; if their needs are too similar, the stronger... 相似文献
86.
Karla?V.?Figueiredo Marciel?T.?Oliveira Emília?C.?P.?Arruda Bárbara?C.?F.?Silva Mauro?G.?SantosEmail author 《Acta Physiologiae Plantarum》2015,37(6):108
Jatropha curcas and Jatropha mollissima plants were evaluated under conditions of high (HSM) and low (LSM) soil moisture in a semi-arid environment, as changes in the content and concentration of epicuticular wax and the leaf metabolism which could have a relationship with drought tolerance. Besides epicuticular wax, gas exchange, antioxidant system and biochemical parameters of the photosynthetic metabolism were measured. The epicuticular wax content increased only in J. mollissima leaves 95 % under LSM, when compared with HSM conditions. Therefore, J. curcas invested less in the production of long-chain n-alkanes than did J. mollissima under LSM conditions. J. mollissima plants showed the highest CO2 assimilation rate during the HSM period compared to J. curcas. Both species showed high stability in some leaf biochemistry products, highlighting the highest sugar content, free amino acids, total soluble protein, and photosynthetic pigments in the leaves of J. mollissima plants under both of the soil moisture conditions. Moreover, the stability and performance of the different parameters, such as morphologic variables, seem to allow J. mollissima plants to tolerate semi-arid conditions. 相似文献
87.
Vibrio cholerae MARTX toxin heterologous translocation of beta‐lactamase and roles of individual effector domains on cytoskeleton dynamics 下载免费PDF全文
Jazel S. Dolores Shivani Agarwal Martina Egerer Karla J. F. Satchell 《Molecular microbiology》2015,95(4):590-604
The Vibrio cholerae MARTXVc toxin delivers three effector domains to eukaryotic cells. To study toxin delivery and function of individual domains, the rtxA gene was modified to encode toxin with an in‐frame beta‐lactamase (Bla) fusion. The hybrid RtxA::Bla toxin was Type I secreted from bacteria; and then Bla was translocated into eukaryotic cells and delivered by autoprocessing, demonstrating that the MARTXVc toxin is capable of heterologous protein transfer. Strains that produce hybrid RtxA::Bla toxins that carry one effector domain in addition to Bla were found to more efficiently translocate Bla. In cell biological assays, the actin cross‐linking domain (ACD) and Rho‐inactivation domain (RID) are found to cross‐link actin and inactivate RhoA, respectively, when other effector domains are absent, with toxin autoprocessing required for high efficiency. The previously unstudied alpha‐beta hydrolase domain (ABH) is shown here to activate CDC42, although the effect is ameliorated when RID is also present. Despite all effector domains acting on cytoskeleton assembly, the ACD was sufficient to rapidly inhibit macrophage phagocytosis. Both the ACD and RID independently disrupted polarized epithelial tight junction integrity. The sufficiency of ACD but strong selection for retention of RID and ABH suggests these two domains may primarily function by modulating cell signaling. 相似文献
88.
89.
Gregory S. Berns Peter F. Cook Sean Foxley Saad Jbabdi Karla L. Miller Lori Marino 《Proceedings. Biological sciences / The Royal Society》2015,282(1811)
The brains of odontocetes (toothed whales) look grossly different from their terrestrial relatives. Because of their adaptation to the aquatic environment and their reliance on echolocation, the odontocetes'' auditory system is both unique and crucial to their survival. Yet, scant data exist about the functional organization of the cetacean auditory system. A predominant hypothesis is that the primary auditory cortex lies in the suprasylvian gyrus along the vertex of the hemispheres, with this position induced by expansion of ‘associative′ regions in lateral and caudal directions. However, the precise location of the auditory cortex and its connections are still unknown. Here, we used a novel diffusion tensor imaging (DTI) sequence in archival post-mortem brains of a common dolphin (Delphinus delphis) and a pantropical dolphin (Stenella attenuata) to map their sensory and motor systems. Using thalamic parcellation based on traditionally defined regions for the primary visual (V1) and auditory cortex (A1), we found distinct regions of the thalamus connected to V1 and A1. But in addition to suprasylvian-A1, we report here, for the first time, the auditory cortex also exists in the temporal lobe, in a region near cetacean-A2 and possibly analogous to the primary auditory cortex in related terrestrial mammals (Artiodactyla). Using probabilistic tract tracing, we found a direct pathway from the inferior colliculus to the medial geniculate nucleus to the temporal lobe near the sylvian fissure. Our results demonstrate the feasibility of post-mortem DTI in archival specimens to answer basic questions in comparative neurobiology in a way that has not previously been possible and shows a link between the cetacean auditory system and those of terrestrial mammals. Given that fresh cetacean specimens are relatively rare, the ability to measure connectivity in archival specimens opens up a plethora of possibilities for investigating neuroanatomy in cetaceans and other species. 相似文献
90.
Scott T. Baker Shane M. Turgeon Erik D. Tulgren Jeanne Wigant Omeed Rahimi Karla J. Opperman Brock Grill 《Genetics》2015,199(1):151-156
We show that loss-of-function mutations in kinases of the MLK-1 pathway (mlk-1, mek-1, and kgb-1/jnk) function cell-autonomously in neurons to suppress defects in synapse formation and axon termination caused by rpm-1 loss of function. Our genetic analysis also suggests that the phosphatase PPM-1, like RPM-1, is a potential inhibitor of kinases in the MLK-1 pathway. 相似文献