全文获取类型
收费全文 | 4692篇 |
免费 | 369篇 |
国内免费 | 236篇 |
出版年
2024年 | 8篇 |
2023年 | 42篇 |
2022年 | 75篇 |
2021年 | 125篇 |
2020年 | 96篇 |
2019年 | 121篇 |
2018年 | 189篇 |
2017年 | 137篇 |
2016年 | 193篇 |
2015年 | 287篇 |
2014年 | 291篇 |
2013年 | 383篇 |
2012年 | 414篇 |
2011年 | 375篇 |
2010年 | 217篇 |
2009年 | 181篇 |
2008年 | 237篇 |
2007年 | 240篇 |
2006年 | 231篇 |
2005年 | 170篇 |
2004年 | 144篇 |
2003年 | 143篇 |
2002年 | 104篇 |
2001年 | 113篇 |
2000年 | 95篇 |
1999年 | 73篇 |
1998年 | 38篇 |
1997年 | 44篇 |
1996年 | 22篇 |
1995年 | 30篇 |
1994年 | 35篇 |
1993年 | 20篇 |
1992年 | 50篇 |
1991年 | 37篇 |
1990年 | 50篇 |
1989年 | 41篇 |
1988年 | 21篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1971年 | 8篇 |
1970年 | 9篇 |
1968年 | 7篇 |
排序方式: 共有5297条查询结果,搜索用时 343 毫秒
151.
152.
Ruimin Mu Yujie He Sixiu Liu Xiangrong Wang Zhengqiu Fan 《Geomicrobiology journal》2013,30(7):516-521
One strain of algicidal bacterium which can inhibit Harmful algal blooms (HABs), FDT5, was isolated from activated sludge and found to have good algicidal effects on Microcystis aeruginosa. It was revealed that: The FDT5 was a Gram-negative bacterium and identified as Ochrobactrum sp.; The greater the initial bacterial cell density, the faster the degradation of chlorophyll a.; The algicidal efficiency was evaluated at the most favorable conditions which were a temperature of 30–35°C, a pH of 7.6 and complete darkness; The FDT5 strain lysed Microcystis aeruginosa not directly but by secreting metabolites which could withstand high temperatures and pressure. 相似文献
153.
154.
155.
Ana Casa?al Ulrich Zander Cristina Mu?oz Florine Dupeux Irene Luque Miguel Angel Botella Wilfried Schwab Victoriano Valpuesta José A. Marquez 《The Journal of biological chemistry》2013,288(49):35322-35332
Pathogenesis-related 10 (PR-10) proteins are involved in many aspects of plant biology but their molecular function is still unclear. They are related by sequence and structural homology to mammalian lipid transport and plant abscisic acid receptor proteins and are predicted to have cavities for ligand binding. Recently, three new members of the PR-10 family, the Fra a proteins, have been identified in strawberry, where they are required for the activity of the flavonoid biosynthesis pathway, which is essential for the development of color and flavor in fruits. Here, we show that Fra a proteins bind natural flavonoids with different selectivity and affinities in the low μm range. The structural analysis of Fra a 1 E and a Fra a 3-catechin complex indicates that loops L3, L5, and L7 surrounding the ligand-binding cavity show significant flexibility in the apo forms but close over the ligand in the Fra a 3-catechin complex. Our findings provide mechanistic insight on the function of Fra a proteins and suggest that PR-10 proteins, which are widespread in plants, may play a role in the control of secondary metabolic pathways by binding to metabolic intermediates. 相似文献
156.
Roberto Zenteno-Cuevas Francisco X Silva-Hernández Fabiola Mendoza-Damián Maria Dolores Ramírez-Hernández Karen Vázquez-Medina Lorena Widrobo-García Aremy Cuellar-Sanchez Raquel Mu?íz-Salazar Leonor Enciso-Moreno Lucia Monserrat Pérez-Navarro José Antonio Enciso-Moreno 《Memórias do Instituto Oswaldo Cruz》2013,108(6):718-723
Tuberculosis (TB) is an infectocontagious respiratory disease caused by members
of the Mycobacterium tuberculosis complex. A 7 base pair (bp)
deletion in the locus polyketide synthase
(pks)15/1 is described as polymorphic among members of the
M. tuberculosis complex, enabling the identification of
Euro-American, Indo-Oceanic and Asian lineages. The aim of this study was to
characterise this locus in TB isolates from Mexico. One hundred
twenty clinical isolates were recovered from the states of Veracruz and Estado
de Mexico. We determined the nucleotide sequence of a ± 400 bp fragment of the
locus pks15/1, while genotypic characterisation was
performed by spoligotyping. One hundred and fifty isolates contained the 7 bp
deletion, while five had the wild type locus. Lineages X (22%),
LAM (18%) and T (17%) were the most frequent; only three (2%) of the isolates
were identified as Beijing and two (1%) EAI-Manila. The wild type
pks15/1 locus was observed in all Asian lineage isolates
tested. Our results confirm the utility of locus pks15/1 as a
molecular marker for identifying Asian lineages of the M.
tuberculosis complex. This marker could be of great value in the
epidemiological surveillance of TB, especially in countries like Mexico, where
the prevalence of such lineages is unknown. 相似文献
157.
158.
Natalia Jiménez José Antonio Curiel Inés Reverón Blanca de las Rivas Rosario Mu?oz 《Applied and environmental microbiology》2013,79(14):4253-4263
Lactobacillus plantarum is a lactic acid bacterium able to degrade tannins by the subsequent action of tannase and gallate decarboxylase enzymes. The gene encoding tannase had previously been identified, whereas the gene encoding gallate decarboxylase is unknown. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of gallic-acid induced L. plantarum extracts showed a 54-kDa protein which was absent in the uninduced cells. This protein was identified as Lp_2945, putatively annotated UbiD. Homology searches identified ubiD-like genes located within three-gene operons which encoded the three subunits of nonoxidative aromatic acid decarboxylases. L. plantarum is the only bacterium in which the lpdC (lp_2945) gene and the lpdB and lpdD (lp_0271 and lp_0272) genes are separated in the chromosome. Combination of extracts from recombinant Escherichia coli cells expressing the lpdB, lpdC, and lpdC genes demonstrated that LpdC is the only protein required to yield gallate decarboxylase activity. However, the disruption of these genes in L. plantarum revealed that the lpdB and lpdC gene products are essential for gallate decarboxylase activity. Similar to L. plantarum tannase, which exhibited activity only in esters derived from gallic and protocatechuic acids, purified His6-LpdC protein from E. coli showed decarboxylase activity against gallic and protocatechuic acids. In contrast to the tannase activity, gallate decarboxylase activity is widely present among lactic acid bacteria. This study constitutes the first genetic characterization of a gallate decarboxylase enzyme and provides new insights into the role of the different subunits of bacterial nonoxidative aromatic acid decarboxylases. 相似文献
159.
Raquel Lebrero Elisa Rodríguez Rebeca Pérez Pedro A. García-Encina Raúl Muñoz 《Applied microbiology and biotechnology》2013,97(10):4627-4638
The removal of hydrophobic volatile organic compounds (VOCs) still remains the main restriction in the biological treatment of odorous emissions due to mass transfer limitations. The addition of a non-aqueous phase to conventional biotrickling filters (BTF) may overcome this limitation by enhancing VOCs transport from the gas to the microorganisms. This study compared the long-term and transient performance of a one- (1P) and two-liquid phase (2P; with silicone oil as non-aqueous phase) BTFs for the removal of four VOCs (butanone, toluene, alpha-pinene, and hexane) at empty bed residence times (EBRT) ranging from 47 to 6 s. Removal efficiencies (RE) >96 % were obtained for butanone, toluene, and alpha-pinene in both bioreactors regardless of the EBRT, while higher hexane REs were recorded in the 2P-BTF (81–92 %) compared to the 1P-BTF (60–97 %). The two-phase system always showed a more consistent performance, being able to better withstand step VOC concentration increases and starvation periods, although it was more affected by liquid recycling shutdowns due to a reduced VOC mass transfer. The analysis of the microbial communities showed a high biodiversity and richness despite the low C source spectrum and high community evenness and richness. In this context, the presence of silicone oil mediated the development of a highly different phylogenetic composition of the communities. 相似文献
160.
Ugo Mellone Beatriz Yáñez Rubén Limiñana A.-Román Muñoz Diego Pavón J.-Miguel González 《Bird Study》2013,60(4):516-521
Capsule Immature Short-toed Snake Eagles hatched in Spain leave their Sahelian wintering grounds to spend the summer in northern Africa. 相似文献