全文获取类型
收费全文 | 617篇 |
免费 | 54篇 |
国内免费 | 222篇 |
出版年
2024年 | 4篇 |
2023年 | 19篇 |
2022年 | 11篇 |
2021年 | 33篇 |
2020年 | 23篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 20篇 |
2016年 | 13篇 |
2015年 | 15篇 |
2014年 | 33篇 |
2013年 | 18篇 |
2012年 | 39篇 |
2011年 | 43篇 |
2010年 | 21篇 |
2009年 | 28篇 |
2008年 | 27篇 |
2007年 | 30篇 |
2006年 | 21篇 |
2005年 | 61篇 |
2004年 | 64篇 |
2003年 | 24篇 |
2002年 | 22篇 |
2001年 | 22篇 |
2000年 | 67篇 |
1999年 | 24篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 7篇 |
1995年 | 11篇 |
1994年 | 17篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有893条查询结果,搜索用时 17 毫秒
41.
42.
43.
Stefferl A Schubart A Storch M Amini A Mather I Lassmann H Linington C 《Journal of immunology (Baltimore, Md. : 1950)》2000,165(5):2859-2865
Experimental autoimmune encephalomyelitis (EAE) induced by sensitization with myelin oligodendrocyte glycoprotein (MOG) is a T cell-dependent autoimmune disease that reproduces the inflammatory demyelinating pathology of multiple sclerosis. We report that an encephalitogenic T cell response to MOG can be either induced or alternatively suppressed as a consequence of immunological cross-reactivity, or "molecular mimicry" with the extracellular IgV-like domain of the milk protein butyrophilin (BTN). In the Dark Agouti rat, active immunization with native BTN triggers an inflammatory response in the CNS characterized by the formation of scattered meningeal and perivascular infiltrates of T cells and macrophages. We demonstrate that this pathology is mediated by a MHC class II-restricted T cell response that cross-reacts with the MOG peptide sequence 76-87, I GEG KVA LRIQ N (identities underlined). Conversely, molecular mimicry with BTN can be exploited to suppress disease activity in MOG-induced EAE. We demonstrate that not only is EAE mediated by the adoptive transfer of MOG74-90 T cell lines markedly ameliorated by i.v. treatment with the homologous BTN peptide, BTN74-90, but that this protective effect is also seen in actively induced disease following transmucosal (intranasal) administration of the peptide. These results identify a mechanism by which the consumption of milk products may modulate the pathogenic autoimmune response to MOG. 相似文献
44.
The presence or absence of cyanogenic glycosides was determined for individuals from nine populations of Sambucus canadensis L. (elderberry) of east-central Illinois. In most of the populations tested, all or most of the individuals did not produce these compounds, in one, all were cyanogenic, whereas in another population this trait was highly variable. Addition of the enzyme emulsin to negative tests did not result in any further release of cyanide. The glycoside responsible is (S)-sambunigrin. 相似文献
45.
This article introduces a new method to represent bone surface geometry for simulations of joint contact. The method uses the inner product of two basis functions to provide a mathematical representation of the joint surfaces. This method guarantees a continuous transition in the direction of the surface normals, an important property for computation of joint contact. Our formulation handles experimental data that are not evenly distributed, a common characteristic of digitized data of musculoskeletal morphologies. The method makes it possible to represent highly curved surfaces, which are encountered in many anatomical structures. The accuracy of this method is demonstrated by modeling the human knee joint. The mean relative percentage error in the representation of the patellar track surface was 0.25% (range 0-1.56%) which corresponded to an absolute error of 0.17mm (range 0-0.16mm). 相似文献
46.
T Banaszak A LaJeunesse TC Trench RK 《Journal of experimental marine biology and ecology》2000,249(2):219-233
We tested the hypothesis that there is a relation between phylotypes (phylogenetic types, as determined by restriction fragment length polymorphism (RFLP) and partial sequence analysis of the small subunit ribosomal RNA gene (SSUrDNA)) and the synthesis of mycosporine-like amino acids (MAAs) by symbiotic dinoflagellates under the influence of ultraviolet radiation (UV-B/A) and photosynthetically active radiation (PAR). We exposed 27 isolates of symbiotic dinoflagellates simultaneously to UV-B/A and PAR, and subsequently determined the MAAs present in cell extracts and in the media. The algae used included 24 isolates of Symbiodinium spp. originating from jellyfishes, sea anemones, zoanthids, scleractinians, octocorals, and bivalves, and three others in the genera Gymnodinium, Gloeodinium and Amphidinium from a jellyfish, an hydrocoral and a flatworm, respectively. In this study, all of the phylotype A Symbiodinium spp. synthesized up to three identified MAAs. None of the 11 cultured phylotypes B and C Symbiodinium spp. synthesized MAAs. The three non-Symbiodinium symbionts also synthesized up to three MAAs. The results support a conclusion that phylotype A Symbiodinium spp. have a high predilection for the synthesis of MAAs, while phylotypes B and C do not. Synthesis of MAAs by symbiotic dinoflagellates in culture does not appear to relate directly to depths or to the UV exposure regimes from which the consortia were collected. 相似文献
47.
48.
CC to TT mutation in the mitochondrial DNA of normal skin: relationship to ultraviolet light exposure 总被引:1,自引:0,他引:1
We have previously reported that ultraviolet (UV)-specific (CC to TT) mutations in p53 gene can be detected in normal skin. This, however, cannot be used as a cumulative marker of UV exposure, since cells with the p53 mutation acquire a clonal growth advantage. Moreover, a large skin biopsy is necessary for each assay. In order to circumvent these problems, we have measured mitochondrial (Mt) DNA mutations; there are more than 1000 copies of the Mt genome per cell, and Mt genes are not directly involved in cell growth. We have established a sensitive allele-specific polymerase chain reaction (AS-PCR) assay capable of detecting one CC to TT mutation in Mt DNA among 10(7) wild-type genes using a mismatch allele-specific primer. With this assay, we found no mutation-positive samples from internal non-exposed tissue (stomach, colon, and blood) (0/50). In contrast, 17 out of 111 skin samples were positive: the mutation frequency in positive samples was around 10(7)-10(-6) (10-100 copies of mutant in 10(8) wild-type Mt DNA). In normal skin tissue, the prevalence of positive samples was higher in those from exposed sites (13/51) than in those from less-exposed sites (1/26) (p<0.05). However, a quantitative correlation between sunlight exposure and the accumulation of mutations was not found. We conclude that the UV exposure-associated CC to TT mutation in Mt DNA can be detected in normal skin, but that further studies are required to develop this as a quantitative marker for UV exposure. 相似文献
49.
50.
粉防己碱抑制血管平滑肌细胞增殖及对HSP70和p53表达的影响 总被引:11,自引:0,他引:11
目的:观察粉防己碱(Tet)对VSMC增殖的作用及对热应激蛋白70kd(HSP70)及其mRNA和抑癌基因p53mRNA的影响。方法:用内皮素建立培养的血管平滑肌细胞增殖模型。采用氚-胸腺嘧啶核苷([3H]TdR)掺入法流式细胞术,Western及Northernblot杂交方法。结果:Tet能逆转内皮素所致的[3H]TdR掺入量增多(P<0.01),阻止血管平滑肌细胞由静止期(G0/G1期)进入DNA合成期(S期)和有丝分裂期(G2/M期),并能逆转内皮素引起的HSP70及mRNA表达增强(P<0.01或P<0.05),p53抑癌基因mRNA表达减弱(P<0.05)。结论:Tet能抑制血管平滑肌细胞增殖,与HSP70及p53的调控有关 相似文献