全文获取类型
收费全文 | 101597篇 |
免费 | 1020篇 |
国内免费 | 825篇 |
专业分类
103442篇 |
出版年
2023年 | 95篇 |
2022年 | 180篇 |
2021年 | 291篇 |
2020年 | 155篇 |
2019年 | 236篇 |
2018年 | 12058篇 |
2017年 | 10844篇 |
2016年 | 7731篇 |
2015年 | 1045篇 |
2014年 | 730篇 |
2013年 | 884篇 |
2012年 | 4898篇 |
2011年 | 13425篇 |
2010年 | 12371篇 |
2009年 | 8513篇 |
2008年 | 10197篇 |
2007年 | 11787篇 |
2006年 | 676篇 |
2005年 | 882篇 |
2004年 | 1254篇 |
2003年 | 1291篇 |
2002年 | 1070篇 |
2001年 | 446篇 |
2000年 | 367篇 |
1999年 | 170篇 |
1998年 | 74篇 |
1997年 | 58篇 |
1996年 | 55篇 |
1995年 | 59篇 |
1994年 | 58篇 |
1993年 | 72篇 |
1992年 | 95篇 |
1991年 | 107篇 |
1990年 | 74篇 |
1989年 | 75篇 |
1988年 | 75篇 |
1987年 | 51篇 |
1986年 | 48篇 |
1985年 | 48篇 |
1984年 | 39篇 |
1983年 | 46篇 |
1982年 | 20篇 |
1981年 | 23篇 |
1979年 | 23篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1975年 | 16篇 |
1972年 | 258篇 |
1971年 | 279篇 |
1962年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
Melissa A. Partridge Sumana Gopinath Simon J. Myers Jens R Coorssen 《Journal of chemical biology》2016,9(1):9-18
An initial proteomic analysis of the cuprizone mouse model to characterise the breadth of toxicity by assessing cortex, skeletal muscle, spleen and peripheral blood mononuclear cells. Cuprizone treated vs. control mice for an initial characterisation. Select tissues from each group were pooled, analysed in triplicate using two-dimensional gel electrophoresis (2DE) and deep imaging and altered protein species identified using liquid chromatography tandem mass spectrometry (LC/MS/MS). Forty-three proteins were found to be uniquely detectable or undetectable in the cuprizone treatment group across the tissues analysed. Protein species identified in the cortex may potentially be linked to axonal damage in this model, and those in the spleen and peripheral blood mononuclear cells to the minimal peripheral immune cell infiltration into the central nervous system during cuprizone mediated demyelination. Primary oligodendrocytosis has been observed in type III lesions in multiple sclerosis. However, the underlying mechanisms are poorly understood. Cuprizone treatment results in oligodendrocyte apoptosis and secondary demyelination. This initial analysis identified proteins likely related to axonal damage; these may link primary oligodendrocytosis and secondary axonal damage. Furthermore, this appears to be the first study of the cuprizone model to also identify alterations in the proteomes of skeletal muscle, spleen and peripheral blood mononuclear cells. Notably, protein disulphide isomerase was not detected in the cuprizone cohort; its absence has been linked to reduced major histocompatibility class I assembly and reduced antigen presentation. Overall, the results suggest that, like experimental autoimmune encephalomyelitis, results from the standard cuprizone model should be carefully considered relative to clinical multiple sclerosis. 相似文献
94.
Tapas K. Nandi Hridoy R. Bairagya Bishnu P. Mukhopadhyay K. Sekar Dipankar Sukul Asim K. Bera 《Journal of biosciences》2009,34(1):27-34
The role of invariant water molecules in the activity of plant cysteine protease is ubiquitous in nature. On analysing the
11 different Protein DataBank (PDB) structures of plant thiol proteases, the two invariant water molecules W1 and W2 (W220
and W222 in the template 1PPN structure) were observed to form H-bonds with the Ob atom of Asn 175. Extensive energy minimization and molecular dynamics simulation studies up to 2 ns on all the PDB and solvated
structures clearly revealed the involvement of the H-bonding association of the two water molecules in fixing the orientation
of the asparagine residue of the catalytic triad. From this study, it is suggested that H-bonding of the water molecule at
the W1 invariant site better stabilizes the Asn residue at the active site of the catalytic triad. 相似文献
95.
Valuable biological information can be obtained by monitoring the movement of organisms. However, the choice of monitoring
method becomes highly restricted when following small organisms (<100 mm), especially in aquatic ecosystems. Stable isotopes
are being increasingly used in this respect but rarely at the local spatial scale, i.e. 10–1000 s of metres. We sought to
identify movement of small fishes between a main river channel and its tributary. Little overlap in isotope baseline was detected
between the two channels despite some temporal variability in δ15N of baseline indicator organisms in the main river. The individuals of two small cyprinid fish species (Leuciscus souffia and Alburnoides bipunctatus) of all the size classes (40–100 mm) caught within the tributary showed considerable heterogeneity in δ15N values. Classification and discriminant analysis on isotope-derived data distinguished two significantly different groups.
Moreover, this result was supported by further sampling of fish caught in the main river (in May and December 2006). Alternative
hypotheses, such as dietary differences, biological factors, temporal shifts and spatial differences in diet, did not explain
δ15N variability. This application of stable isotopes at a relatively small spatial and temporal scales further demonstrates
its potential as a tool for ecologists. 相似文献
96.
N.T. Nguyen M. Liu H. Katayama T. Takemura I. Kasuga 《Letters in applied microbiology》2021,72(3):275-282
Colistin is one of the antibiotics of last resort for human health. However, the dissemination of the plasmid-mediated colistin resistance gene mcr-1 is of great concern globally. In the One Health framework, the environment is an important component for managing antimicrobial resistance. However, little information is available concerning the prevalence of mcr-1 in water environments. We aimed to reveal the prevalence of mcr-1 in different water environments in Hanoi, Vietnam. Quantitative PCR was applied to detect mcr-1 in four urban drainages receiving untreated domestic wastewater, three rivers, five lakes and two groundwater samples. Urban drainages contained higher concentrations of mcr-1, suggesting that urban residents carry the gene. The class 1 integron-integrase gene was identified as a good surrogate of antibiotic resistance genes including mcr-1. A significant correlation was found between the levels of mcr-1 and the human-specific cross-assembly phage, which is an indicator of human faecal pollution. These results indicated that the primary source of mcr-1 in urban water environments is human faeces, which is consistent with the fact that most domestic wastewater is untreated in Hanoi. The control of untreated wastewater is critical for alleviating the spread of mcr-1 in water environments in Vietnam. 相似文献
97.
98.
99.
Mingyue Wang Pranab K Mukherjee Jyotsna Chandra Ali Abdul Lattif Thomas S McCormick Mahmoud A Ghannoum 《BMC microbiology》2008,8(1):31
Background
We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed. 相似文献100.
Dana M. Bergstrom George R. Stewart Patricia M. Selkirk Susanne Schmidt 《Oecologia》2002,130(2):309-314
'15N signatures of fossil peat were used to interpret past ecosystem processes on tectonically active subantarctic Macquarie Island. By comparing past vegetation reconstructed from the fossil record with present-day vegetation analogues, our evidence strongly suggests that changes in the '15N signatures of fossil peat at this location reflect mainly past changes in the proportion of plant nitrogen derived from animal sources. Associated with uplift above sea level over the past 8,500 years, fossil records in two peat deposits on the island chronicle a change from coastal vegetation with fur and elephant seal disturbance to the existing inland herbfield. Coupled with this change are synchronous changes in the '15N signatures of peat layers. At two sites 15N-enriched peat '15N signatures of up to +17 were associated with a high abundance of pollen of the nitrophile Callitriche antarctica (Callitrichaceae). At one site fossil seal hair was also associated with enriched peat '15N. Less 15N enriched '15N signatures (e.g. -1.9 to +3.9) were measured in peat layers which lacked animal associated C. antarctica and Acaena spp. Interpretation of a third peat profile indicates continual occupation of a ridge site by burrowing petrels for most of the Holocene. We suggest that 15N signatures of fossil peat remained relatively stable with time once deposited, providing a significant new tool for interpreting the palaeoecology. 相似文献