全文获取类型
收费全文 | 1524篇 |
免费 | 120篇 |
专业分类
1644篇 |
出版年
2023年 | 12篇 |
2022年 | 14篇 |
2021年 | 41篇 |
2020年 | 19篇 |
2019年 | 43篇 |
2018年 | 29篇 |
2017年 | 28篇 |
2016年 | 53篇 |
2015年 | 86篇 |
2014年 | 67篇 |
2013年 | 93篇 |
2012年 | 116篇 |
2011年 | 98篇 |
2010年 | 60篇 |
2009年 | 61篇 |
2008年 | 79篇 |
2007年 | 67篇 |
2006年 | 70篇 |
2005年 | 56篇 |
2004年 | 61篇 |
2003年 | 52篇 |
2002年 | 45篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 30篇 |
1998年 | 14篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 12篇 |
1994年 | 19篇 |
1993年 | 9篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 8篇 |
1987年 | 14篇 |
1986年 | 21篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 14篇 |
1972年 | 7篇 |
排序方式: 共有1644条查询结果,搜索用时 15 毫秒
71.
72.
Nir Eynon Emiliya S. Nasibulina Lauren K. Banting Pawel Cieszczyk Agnieszka Maciejewska-Karlowska Marek Sawczuk Elvira A. Bondareva Roza R. Shagimardanova Maytal Raz Yael Sharon Alun G. Williams Ildus I. Ahmetov Alejandro Lucia Ruth Birk 《PloS one》2013,8(4)
Objective
The FTO A/T polymorphism (rs9939609) is a strong candidate to influence obesity-related traits. Elite athletes from many different sporting disciplines are characterized by low body fat. Therefore, the aim of this study was to assess whether athletic status is associated with the FTO A/T polymorphism.Subjects and Methods
A large cohort of European Caucasians from Poland, Russia and Spain were tested to examine the association between FTO A/T polymorphism (rs9939609) and athletic status. A total of 551 athletes were divided by type of sport (endurance athletes, n = 266 vs. sprint/power athletes, n = 285) as well as by level of competition (elite-level vs. national-level). The control group consisted of 1,416 ethnically-matched, non-athletic participants, all Europeans. Multinomial logistic regression analyses were conducted to assess the association between FTO A/T genotypes and athletic status/competition level.Results
There were no significantly greater/lesser odds of harbouring any type of genotype when comparing across athletic status (endurance athletes, sprint/power athletes or control participants). These effects were observed after controlling for sex and nationality. Furthermore, no significantly greater/lesser odds ratios were observed for any of the genotypes in respect to the level of competition (elite-level vs. national-level).Conclusion
The FTO A/T polymorphism is not associated with elite athletic status in the largest group of elite athletes studied to date. Large collaborations and data sharing between researchers, as presented here, are strongly recommended to enhance the research in the field of exercise genomics. 相似文献73.
The fluorescamine test for the rapid detection of trace amounts of uncoupled products from solid phase peptide synthesis is reported. This novel procedure can detect much smaller amounts of incomplete coupling with greater simplicity than has previously been possible. Since the test is carried out under mild conditions certain side reactions are circumvented. The fluorophor-resins are easily viewed under long wave ultraviolet light, are stable at room temperature, and may be used for quantitative evaluation. 相似文献
74.
Hurtado-Carneiro V Sanz C Roncero I Vazquez P Blazquez E Alvarez E 《Molecular neurobiology》2012,45(2):348-361
The anorexigenic peptide, glucagon-like peptide-1 (GLP-1), reduces glucose metabolism in the human hypothalamus and brain
stem. The brain activity of metabolic sensors such as AMP-activated protein kinase (AMPK) responds to changes in glucose levels.
The mammalian target of rapamycin (mTOR) and its downstream target, p70S6 kinase (p70S6K), integrate nutrient and hormonal
signals. The hypothalamic mTOR/p70S6K pathway has been implicated in the control of feeding and the regulation of energy balances.
Therefore, we investigated the coordinated effects of glucose and GLP-1 on the expression and activity of AMPK and p70S6K
in the areas involved in the control of feeding. The effect of GLP-1 on the expression and activities of AMPK and p70S6K was
studied in hypothalamic slice explants exposed to low- and high-glucose concentrations by quantitative real-time RT-PCR and
by the quantification of active-phosphorylated protein levels by immunoblot. In vivo, the effects of exendin-4 on hypothalamic
AMPK and p70S6K activation were analysed in male obese Zucker and lean controls 1 h after exendin-4 injection to rats fasted
for 48 h or after re-feeding for 2–4 h. High-glucose levels decreased the expression of Ampk in the lateral hypothalamus and treatment with GLP-1 reversed this effect. GLP-1 treatment inhibited the activities of AMPK
and p70S6K when the activation of these protein kinases was maximum in both the ventromedial and lateral hypothalamic areas.
Furthermore, in vivo s.c. administration of exendin-4 modulated AMPK and p70S6K activities in those areas, in both fasted
and re-fed obese Zucker and lean control rats. 相似文献
75.
Pedro Jimenez‐Sandoval Ezequiel A. Madrigal‐Carrillo Hugo A. Santamaría‐Suárez Daniel Maturana Itzel Rentería‐González Claudia G. Benitez‐Cardoza Alfredo Torres‐Larios Luis G. Brieba 《Proteins》2018,86(7):802-812
Antibodies recognize protein targets with great affinity and specificity. However, posttranslational modifications and the presence of intrinsic disulfide‐bonds pose difficulties for their industrial use. The immunoglobulin fold is one of the most ubiquitous folds in nature and it is found in many proteins besides antibodies. An example of a protein family with an immunoglobulin‐like fold is the Cysteine Protease Inhibitors (ICP) family I42 of the MEROPs database for protease and protease inhibitors. Members of this protein family are thermostable and do not present internal disulfide bonds. Crystal structures of several ICPs indicate that they resemble the Ig‐like domain of the human T cell co‐receptor CD8α As ICPs present 2 flexible recognition loops that vary accordingly to their targeted protease, we hypothesize that members of this protein family would be ideal to design peptide aptamers that mimic protein‐protein interactions. Herein, we use an ICP variant from Entamoeba histolytica (EhICP1) to mimic the interaction between p53 and MDM2. We found that a 13 amino‐acid peptide derived from p53 can be introduced in 2 variable loops (DE, FG) but not the third (BC). Chimeric EhICP1‐p53 form a stable complex with MDM2 at a micromolar range. Crystal structure of the EhICP1‐p53(FG)‐loop variant in complex with MDM2 reveals a swapping subdomain between 2 chimeric molecules, however, the p53 peptide interacts with MDM2 as in previous crystal structures. The structural details of the EhICP1‐p53(FG) interaction with MDM2 resemble the interaction between an antibody and MDM2. 相似文献
76.
Summary Increasing data onDrosophila alcohol dehydrogenase (ADH) sequences have made it possible to calculate the rate of amino acid replacement per year, which is 1.7×10–9. This value makes this protein suitable for reconstructing phylogenetic relationships within the genus for those species for which no molecular data are available such asScaptodrosophila. The amino acid sequence ofDrosophila lebanonensis is compared to all of the already knownDrosophila ADHs, stressing the unique characteristic features of this protein such as the conservation of an initiating methionine at the N-terminus, the unique replacement of a glycine by an alanine at a very conserved position in the NAD domain of all dehydrogenases, the lack of a slowmigrating peptide, and the total conservation of the maximally hydrophilic peptide. The functional significance of these features is discussed.Although the percent amino acid identity of the ADH molecule inDrosophila decreases as the number of sequences compared increases, the conservation of residue type in terms of size and hydrophobocity for the ADH molecule is shown to be very high throughout the genusDrosophila. The distance matrix and parsimony methods used to establish the phylogenetic relationships ofD. lebanonensis show that the three subgenera,Scaptodrosophila, Drosophila, andSophophora separated at approximately the same time. 相似文献
77.
Analysis of ethylene‐induced gene regulation during carposporogenesis in the red seaweed Grateloupia imbricata (Rhodophyta) 下载免费PDF全文
Pilar Garcia‐Jimenez Montserrat Montero‐Fernández Rafael R. Robaina 《Journal of phycology》2018,54(5):681-689
Ethylene favors carposporogenesis in the red seaweed Grateloupia imbricata. Analyses of cystocarp development in vitro in thalli treated with ethylene suggest an interconnection between polyamine and ethylene biosynthesis pathways. Yet, little is known about molecular mechanisms underlying carposporogenesis. Here, we used droplet digital PCR to analyze genes encoding enzymes related to polyamine (Spermidine [Spd] synthase) and ethylene (ACC synthase) synthesis; a pivotal compound of both pathways (S‐adenosyl methionine synthase, SAMS); the gene that encodes amine oxidase, which is involved in polyamine degradation, and a candidate gene involved in seaweed reproduction (ornithine decarboxylase, ODC). In addition, we analyzed genes encoding proteins related to stress and reactive oxygen species, ascorbate peroxidase (APX), cytochrome P450 and WD 40. We characterized gene expression in fertilized and fertile thalli from G. imbricata that were exposed to ethylene for 15 min at two time points after treatment (1 and 7 d). The differential gene expression of SAMS, Spd synthase, ACC synthase, and cytochrome P450 was related to disclosure and development of cystocarps in fertilized thalli that transitioned from having no visible cystocarps at 1 d to developing cystocarps at 7 d. Likewise, cytochrome P450 was associated with cystocarp disclosure and maturation. In addition, amine oxidase and APX were involved in fine‐tuning polyamine and reactive oxygen species during carposporogenesis, respectively, whereas WD 40 did so in relation to ethylene signaling. Expression of the candidate gene ODC was increased when cystocarps were not visible (fertilized thalli, 1d), as previously described. This analysis suggests developmental stage‐specific roles for these genes during carposporogenesis. 相似文献
78.
Detection of nuclear lamin B epitopes in oocyte nuclei from mice, sea urchins, and clams using a human autoimmune serum 总被引:2,自引:0,他引:2
Somatic nuclei typically contain two or three major proteins, the lamins A, B, and C or their antigenically related equivalents, interspersed between the chromatin and its attachment site, the inner nuclear membrane. The late oocyte nuclear envelopes of the previously investigated Xenopus and Spisula germinal vesicles, however, have no chromatin attached and only one lamin-like protein. Since mouse and sea urchin germinal vesicles have chromatin attached, we tested them for the possible presence of more than one lamin. In both species we found two different lamins incorporated in their nuclear envelope structure. One lamin is recognized by anti-lamin B and the other by anti-lamin AC antibodies. Spisula germinal vesicles were found to contain not only the nuclear envelope-bound lamin (clamin), but also a 65-kDa protein cross-reactive with anti-lamin B antibodies. This protein is present unattached to any structure and is apparently soluble. Our findings provide a possible explanation of the early presence of lamin B in pronuclei of mouse and sea urchin contrary to the late appearance of a lamin B equivalent in amphibian embryos. In Spisula, as in Xenopus, the presence of a lamin B equivalent could not be documented in the nuclear envelopes of early embryos, indicating that a separate lamin B equivalent is not essential for chromatin binding to the envelope in these species during early embryogenesis. The results also indicate that the nuclear complement of structural proteins might vary substantially in the same cell type of different species. 相似文献
79.
Identification of the gene encoding an N-acetylpuromycin N-acetylhydrolase in the puromycin biosynthetic gene cluster from Streptomyces alboniger. 下载免费PDF全文
The biologically inactive compound N-acetylpuromycin is the last intermediate of the puromycin antibiotic biosynthetic pathway in Streptomyces alboniger. Culture filtrates from either this organism or Streptomyces lividans transformants harboring the puromycin biosynthetic gene cluster cloned in low-copy-number cosmids contained an enzymic activity which hydrolyzes N-acetylpuromycin to produce the active antibiotic. A gene encoding the deacetylase enzyme was located at one end of this cluster, subcloned in a 2.5-kb DNA fragment, and expressed from a high-copy-number plasmid in S. lividans. 相似文献
80.
Roscinto Ian C. Lumbres Jennifer A. Palaganas Sheryll C. Micosa Kenneth A. Laruan Elvira D. Besic Chung-Weon Yun Young-Jin Lee 《Landscape and Ecological Engineering》2014,10(2):361-368
This study was conducted to assess the floral composition of the Alno communal mixed forest in the Philippines. A quadrat method of vegetational analysis was used for the assessment of trees, shrubs, saplings, and seedlings. A total of 78 species belonging to 43 families were identified in this communal forest. For the assessment of grasses, herbs, ferns, and other low-lying vegetation, the line intercept method was used. A total of 31 species belonging to 20 families were found using this method. The diversity (Shannon–Wiener) indices of this communal forest are 3.2129 and 2.3870 for the quadrat method and line intercept method, respectively. The most dominant species in this area is Pinus kesiya Royle ex Gordon (Benguet pine) with an importance value of 64.19 %. Endemic species in the area also connote ecological importance, being considered a good indication of the status of habitats and ecosystems of this communal forest. 相似文献