全文获取类型
收费全文 | 918篇 |
免费 | 68篇 |
出版年
2021年 | 6篇 |
2019年 | 7篇 |
2018年 | 16篇 |
2017年 | 20篇 |
2016年 | 19篇 |
2015年 | 16篇 |
2014年 | 12篇 |
2013年 | 69篇 |
2012年 | 55篇 |
2011年 | 71篇 |
2010年 | 54篇 |
2009年 | 38篇 |
2008年 | 44篇 |
2007年 | 39篇 |
2006年 | 45篇 |
2005年 | 35篇 |
2004年 | 51篇 |
2003年 | 40篇 |
2002年 | 38篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1971年 | 6篇 |
1955年 | 8篇 |
1954年 | 27篇 |
1953年 | 8篇 |
1952年 | 9篇 |
1951年 | 9篇 |
1950年 | 7篇 |
1949年 | 7篇 |
排序方式: 共有986条查询结果,搜索用时 232 毫秒
91.
92.
BACKGROUND: A circadian rhythm of symptoms has been reported in allergic rhinitis and some studies have shown the dosing time of antihistamines to be of importance for optimizing symptom relief in this disease. The objective of this study was to examine the efficacy of morning vs. evening dosing of the antihistamine desloratadine at different time points during the day. METHODS: Patients >/= 18 years, with seasonal allergic rhinitis received desloratadine 5 mg orally once daily in the morning (AM-group) or evening (PM-group) for two weeks. Rhinorrhea, nasal congestion, sneezing and eye symptoms were scored morning and evening. Wilcoxon rank sum and 2-way ANOVA test were used. RESULTS: Six-hundred and sixty-three patients were randomized; 336 in the AM-group; 327 in the PM-group. No statistically significant differences were seen between the AM and PM group at any time points. In the sub-groups with higher morning or evening total symptom score no difference in treatment efficacy was seen whether the dose was taken 12 or 24 hours before the higher score time. There was a circadian variation in baseline total symptom score; highest during daytime and lowest at night. The circadian variation in symptoms was reduced during treatment. This reduction was highest for daytime symptoms. CONCLUSIONS: A circadian rhythm was seen for most symptoms being more pronounced during daytime. This was less apparent after treatment with desloratadine. No statistically significant difference in efficacy was seen whether desloratadine was given in the morning or in the evening. This gives the patients more flexibility in choosing dosing time. 相似文献
93.
94.
95.
96.
97.
Øverli Ø Korzan WJ Höglund E Winberg S Bollig H Watt M Forster GL Barton BA ØVerli E Renner KJ Summers CH 《Hormones and behavior》2004,45(4):235-241
Social stress is frequently used as a model for studying the neuroendocrine mechanisms underlying stress-induced behavioral inhibition, depression, and fear conditioning. It has previously been shown that social subordination may result in increased glucocorticoid release and changes in brain signaling systems. However, it is still an open question which neuroendocrine and behavioral differences are causes, and which are consequences of social status. Using juvenile rainbow trout of similar size and with no apparent differences in social history, we demonstrate that the ability to win fights for social dominance can be predicted from the duration of a behavioral response to stress, in this case appetite inhibition after transfer to a new environment. Moreover, stress responsiveness in terms of confinement-induced changes in plasma cortisol was negatively correlated to aggressive behavior. Fish that exhibited lower cortisol responses to a standardized confinement test were markedly more aggressive when being placed in a dominant social position later in the study. These findings support the view that distinct behavioral-physiological stress coping styles are present in teleost fish, and these coping characteristics influence both social rank and levels of aggression. 相似文献
98.
Oligosaccharides implicated in recognition are predicted to have relatively ordered structures 总被引:1,自引:0,他引:1
Fucosylated O- and N-linked glycans are essential recognition molecules in plants and animals. To understand how they impart their functions, through interactions with proteins, requires a detailed analysis of structure and dynamics, but this is presently lacking. In this study, the three-dimensional structure and dynamics of three fucosylated oligosaccharides are investigated using a combination of high field (800 MHz) nuclear magnetic resonance and long (50 ns) molecular dynamics simulations in explicit water. Predictions from dynamics simulations were in agreement with nuclear Overhauser cross-peak intensities. Similarly, a theory of weak alignment in neutral media resulted in reasonable predictions of residual dipolar couplings for the trisaccharide fucosyllactose. However, for larger penta- and hexasaccharides (LNF-1 and LND-1), the anisotropic component of the alignment was underestimated, attributed to shape irregularities of the fucosyl branches on an otherwise linear core, being more pronounced in a singly branched than a doubly branched oligosaccharide. Simulations, confirmed by experiment, predicted fucosylated molecules that are restricted to librations about a single average conformation. This restriction is partly due to microscopic water interactions, which act to stabilize intramolecular hydrogen bonds and maintain tight and ordered conformations; a view not forthcoming from simpler, nonaqueous simulations. Such a conclusion is crucial for understanding how these molecules interact with proteins and impart their recognition properties. 相似文献
99.
Qiao SW Bergseng E Molberg Ø Xia J Fleckenstein B Khosla C Sollid LM 《Journal of immunology (Baltimore, Md. : 1950)》2004,173(3):1757-1762
Celiac disease is an HLA-DQ2-associated disorder characterized by intestinal T cell responses to ingested wheat gluten proteins. A peptide fragment of 33 residues (alpha(2)-gliadin 56-88) produced by normal gastrointestinal proteolysis contains six partly overlapping copies of three T cell epitopes and is a remarkably potent T cell stimulator after deamidation by tissue transglutaminase (TG2). This 33-mer is rich in proline residues and adopts the type II polyproline helical conformation in solution. In this study we report that after deamidation, the 33-mer bound with higher affinity to DQ2 compared with other monovalent peptides harboring gliadin epitopes. We found that the TG2-treated 33-mer was presented equally effectively by live and glutaraldehyde-fixed, EBV-transformed B cells. The TG2-treated 33-mer was also effectively presented by glutaraldehyde-fixed dendritic cells, albeit live dendritic cells were the most effective APCs. A strikingly increased T cell stimulatory potency of the 33-mer compared with a 12-mer peptide was also seen with fixed APCs. The 33-mer showed binding maximum to DQ2 at pH 6.3, higher than maxima found for other high affinity DQ2 binders. The 33-mer is thus a potent T cell stimulator that does not require further processing within APC for T cell presentation and that binds to DQ2 with a pH profile that promotes extracellular binding. 相似文献
100.
Secretory protein enrichment and analysis: an optimized approach applied on cancer cell lines using 2D LC-MS/MS 总被引:1,自引:0,他引:1
Reliable methods for profiling secretory proteins are highly desirable for the identification of biomarkers of disease progression. Secreted proteins are often masked by high amounts of protein supplements in the culture medium. We have developed an efficient method for the enrichment and analysis of the secretome of different cancer cell lines, free of essential contaminants. The method is based on the optimization of cell incubation conditions in protein-free medium. Secreted proteins are concentrated and fractionated using a reversed-phase tC2 Sorbent, followed by peptide mass fingerprinting for protein identification. An average of 88 proteins were identified in each cancer cell line, of which more than 76% are known to be secreted, possess a signal peptide or a transmembrane domain. Given the importance of secreted proteins as a source for early detection and diagnosis of disease, this approach may help to discover novel candidate biomarkers with potential clinical significance. 相似文献