全文获取类型
收费全文 | 1249篇 |
免费 | 101篇 |
专业分类
1350篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 31篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 30篇 |
2017年 | 19篇 |
2016年 | 41篇 |
2015年 | 48篇 |
2014年 | 61篇 |
2013年 | 63篇 |
2012年 | 98篇 |
2011年 | 101篇 |
2010年 | 55篇 |
2009年 | 48篇 |
2008年 | 59篇 |
2007年 | 74篇 |
2006年 | 69篇 |
2005年 | 58篇 |
2004年 | 42篇 |
2003年 | 48篇 |
2002年 | 38篇 |
2001年 | 16篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 6篇 |
1997年 | 14篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 10篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1964年 | 3篇 |
排序方式: 共有1350条查询结果,搜索用时 0 毫秒
101.
In humans, leukocyte cell-derived chemotaxin 2 (LECT2) is a 16kDa chemotactic protein that consists of 133 amino acids and three intramolecular disulphide bonds. Although it was originally demonstrated to have a chemotactic function in vitro, recent data sustain a further multifunctional role of LECT2 that extends from cell growth, differentiation, damage/repair process and carcinogenesis to autoimmune diseases. The in vivo function of LECT2 protein still remains obscure. In order to study the phylogeny of LECT2, a full-length cDNA clone of LECT2 gene, 720 bp in size, was isolated in rainbow trout (Oncorhynchus mykiss). Its deduced amino acid sequence of 156 residues, presents 40, 45 and 61% overall identity to human, mouse and carp LECT2 proteins, respectively. In contrast to mammalian LECT2 protein, trout LECT2 protein reveals two potential N-glycosylation sites. Phylogenetic analysis shows that trout LECT2 is clustered with the known homologous proteins. Trout LECT2 mRNA is predominately expressed in liver and spleen, showing lower expression in kidney, intestine, heart and brain. 相似文献
102.
103.
Stagos D Kazantzoglou G Theofanidou D Kakalopoulou G Magiatis P Mitaku S Kouretas D 《Mutation research》2006,609(2):165-175
Several in vivo and in vitro studies have shown that grape extracts could prevent certain steps in carcinogenesis and a few mechanisms have been proposed for this activity. In this study, the potential antimutagenic activity of methanolic and aqueous extracts from two Greek grape varieties of Vitis vinifera against DNA damage induced by reactive oxygen species (ROS) was assessed as a potential novel chemopreventive mechanism, using Salmonella typhimurium strain TA102. The two grape varieties were Assyrtiko (white grapes) and Mandilaria (red grapes), while the oxidant mutagens used were bleomycin (BLM) and hydrogen peroxide (H(2)O(2)). Since it has been considered that polyphenols present in grapes are their most potent biologically active compounds, we also tested the effects of polyphenol-rich fractions as well as some of the more common grape polyphenols on the activity of the two test mutagens. These polyphenols were quercetin, (+)-catechin, (-)-epicatechin, trans-resveratrol, gallic acid and protocatechuic acid. Almost all extracts showed inhibitory activity against both mutagens. On the other hand, polyphenol-rich fractions as well as individual polyphenols at concentrations found in the extracts either did not diminish or did enhance the activity of the mutagens. These results suggest that the protection of DNA from mutations induced by ROS may be one of the mechanisms accounting for the chemopreventive activity of grape extracts. However, it seems that this protective activity may not be attributed to polyphenols but rather to a synergism of many compounds in the grapes. 相似文献
104.
J L Puel S C Bledsoe R P Bobbin G Ceasar M Fallon 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1989,93(1):73-80
1. Salicylate actions on afferent nerve activity in the Xenopus lateral line and on cochlear potentials in guinea pig were investigated. 2. In the lateral line, salicylate (0.3-2.5 mM) suppressed spontaneous activity, water motion evoked excitation and responses to L-glutamate (1-2 mM) and kainate (10-20 microM). 3. In the guinea pig, salicylate (0.6-10 mM) suppressed the compound action potential (CAP) and increased N1 latency at low but not high sound intensities. 4. In the lateral line salicylate action may involve an antagonism of the hair-cell transmitter on the afferent nerve. 5. In the cochlea salicylate may suppress the active process or cochlear amplifier. 相似文献
105.
María Díez-León Jeff Bowman Steve Bursian Hélène Filion David Galicia Jeannette Kanefsky Angelo Napolitano Rupert Palme Albrecht Schulte-Hostedde Kim Scribner Georgia Mason 《PloS one》2013,8(11)
Wild carnivores in zoos, conservation breeding centres, and farms commonly live in relatively small, unstimulating enclosures. Under these captive conditions, in a range of species including giant pandas, black-footed ferrets, and European mink, male reproductive abilities are often poor. Such problems have long been hypothesized to be caused by these animals'' housing conditions. We show for the first time that rearing under welfare-improving (i.e., highly valued and stress-reducing) environmental enrichments enhances male carnivores'' copulatory performance: in mate choice competitions, enriched male American mink (Neovison vison) mated more often than non-enriched males. We screened for several potential mediators of this effect. First was physiological stress and its impact on reproductive physiology; second, stress-mediated changes in morphology and variables related to immunocompetence that could influence male attractiveness; and third, behavioural changes likely to affect social competence, particularly autistic-like excessive routine and repetition (‘perseveration’) as is reflected in the stereotypies common in captive animals. Consistent with physiological stress, excreted steroid metabolites revealed that non-enriched males had higher cortisol levels and lower androgen levels than enriched conspecifics. Their os penises (bacula) also tended to be less developed. Consistent with reduced attractiveness, non-enriched males were lighter, with comparatively small spleens and a trend to greater fluctuating asymmetry. Consistent with impaired social competence, non-enriched males performed more stereotypic behaviour (e.g., pacing) in their home cages. Of all these effects, the only significant predictor of copulation number was stereotypy (a trend suggesting that low bodyweights may also be influential): highly stereotypic males gained the fewest copulations. The neurophysiological changes underlying stereotypy thus handicap males sexually. We hypothesise that such males are abnormally perseverative when interacting with females. Investigating similar problems in other taxa would be worthwhile, since many vertebrates, wild and domestic, live in conditions that cause stereotypic behaviour and/or impair neurological development. 相似文献
106.
Brian P. Fallon Bryan Curnutte Kevin A. Maupin Katie Partyka Sunguk Choi Randall E. Brand Christopher J. Langmead Waibhav Tembe Brian B. Haab 《PloS one》2013,8(6)
The development of accurate clinical biomarkers has been challenging in part due to the diversity between patients and diseases. One approach to account for the diversity is to use multiple markers to classify patients, based on the concept that each individual marker contributes information from its respective subclass of patients. Here we present a new strategy for developing biomarker panels that accounts for completely distinct patient subclasses. Marker State Space (MSS) defines “marker states” based on all possible patterns of high and low values among a panel of markers. Each marker state is defined as either a case state or a control state, and a sample is classified as case or control based on the state it occupies. MSS was used to define multi-marker panels that were robust in cross validation and training-set/test-set analyses and that yielded similar classification accuracy to several other classification algorithms. A three-marker panel for discriminating pancreatic cancer patients from control subjects revealed subclasses of patients based on distinct marker states. MSS provides a straightforward approach for modeling highly divergent subclasses of patients, which may be adaptable for diverse applications. 相似文献
107.
Menno J. Oudhoff Frann Antignano Alistair L. Chenery Kyle Burrows Stephen A. Redpath Mitchell J. Braam Georgia Perona-Wright Colby Zaph 《PLoS pathogens》2016,12(9)
The intestine is a common site for a variety of pathogenic infections. Helminth infections continue to be major causes of disease worldwide, and are a significant burden on health care systems. Lysine methyltransferases are part of a family of novel attractive targets for drug discovery. SETD7 is a member of the Suppressor of variegation 3-9-Enhancer of zeste-Trithorax (SET) domain-containing family of lysine methyltransferases, and has been shown to methylate and alter the function of a wide variety of proteins in vitro. A few of these putative methylation targets have been shown to be important in resistance against pathogens. We therefore sought to study the role of SETD7 during parasitic infections. We find that Setd7
-/- mice display increased resistance to infection with the helminth Trichuris muris but not Heligmosomoides polygyrus bakeri. Resistance to T. muris relies on an appropriate type 2 immune response that in turn prompts intestinal epithelial cells (IECs) to alter differentiation and proliferation kinetics. Here we show that SETD7 does not affect immune cell responses during infection. Instead, we found that IEC-specific deletion of Setd7 renders mice resistant to T. muris by controlling IEC turnover, an important aspect of anti-helminth immune responses. We further show that SETD7 controls IEC turnover by modulating developmental signaling pathways such as Hippo/YAP and Wnt/β-Catenin. We show that the Hippo pathway specifically is relevant during T. muris infection as verteporfin (a YAP inhibitor) treated mice became susceptible to T. muris. We conclude that SETD7 plays an important role in IEC biology during infection. 相似文献
108.
109.
Calmodulin has been a subject of intense scrutiny since its discovery because of its unusual properties in regulating the functions of about 100 diverse target enzymes and structural proteins. The original and to date only crystal conformation of native eukaryotic Ca(2+)-calmodulin (Ca(2+)-CaM) is a very extended molecule with two widely separated globular domains linked by an exposed long helix. Here we report the 1.7 A X-ray structure of a new native Ca(2+)-CaM that is in a compact ellipsoidal conformation and shows a sharp bend in the linker helix and a more contracted N-terminal domain. This conformation may offer advantages for recognition of kinase-type calmodulin targets or small organic molecule drugs. 相似文献
110.
Guilhem Mansion Gerald Parolly Andrew A. Crowl Evgeny Mavrodiev Nico Cellinese Marine Oganesian Katharina Fraunhofer Georgia Kamari Dimitrios Phitos Rosemarie Haberle Galip Akaydin Nursel Ikinci Thomas Raus Thomas Borsch 《PloS one》2012,7(11)