全文获取类型
收费全文 | 1864篇 |
免费 | 156篇 |
国内免费 | 181篇 |
出版年
2024年 | 5篇 |
2023年 | 24篇 |
2022年 | 47篇 |
2021年 | 93篇 |
2020年 | 80篇 |
2019年 | 84篇 |
2018年 | 60篇 |
2017年 | 62篇 |
2016年 | 74篇 |
2015年 | 115篇 |
2014年 | 137篇 |
2013年 | 148篇 |
2012年 | 173篇 |
2011年 | 146篇 |
2010年 | 112篇 |
2009年 | 88篇 |
2008年 | 118篇 |
2007年 | 69篇 |
2006年 | 62篇 |
2005年 | 56篇 |
2004年 | 46篇 |
2003年 | 39篇 |
2002年 | 43篇 |
2001年 | 36篇 |
2000年 | 34篇 |
1999年 | 37篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 14篇 |
1995年 | 25篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 15篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2201条查询结果,搜索用时 15 毫秒
161.
升振山姜的选育和生物学特性研究 总被引:2,自引:1,他引:1
采用杂交育种技术,以姜科(Zingiberaceae)植物草豆蔻(Alpinia hainanensis K.Schumann)为亲本,母本于1975年从广东引种,具乳白色小苞片;父本于1983年从广西引种,具淡粉红色小苞片.经多年多代分离、筛选和鉴定,从其杂交后代中选育出花卉新品种升振山姜(A.hainanensis... 相似文献
162.
检测旋毛虫感染大鼠血清中的总IgE、特异性IgE和观察IgE介导的肥大细胞脱颗粒,并进一步探讨抗体依赖的(肥大)细胞介导的细胞毒性(Antibody dependent cell mediated cytotoxicity,ADCC)在旋毛虫病免疫机理中的作用。采用雄性Wistar大鼠为旋毛虫感染的动物模型,将90只大鼠随机分为10组。试验时,以ELISA双抗体夹心法和间接法分别动态检测总IgE和特异性IgE;肥大细胞脱颗粒试验采用直接法;然后采用细胞培养法观察免疫血清对肥大细胞杀伤旋毛虫肌幼虫作用的影响。在免疫血清存在时,无论感染鼠还是正常鼠的肥大细胞对旋毛虫幼虫均有杀伤作用,但以感染鼠的作用更强。肥大细胞在ADCC效应机制中对杀伤旋毛虫肌幼虫发挥了重要的作用。 相似文献
163.
164.
165.
Chen J Li Q Zhang Y Yang P Zong Y Qu S Liu Z 《Journal of physiology and biochemistry》2011,67(2):153-163
The reported data indicate that oleic acid (OA) decreases cholesterol absorption. To explore the underlying mechanisms, the
effects of OA on the expression of cholesterol transport-related proteins (NPC1L1, ABCG5/8, ACAT2, MTP) and the unfolded protein
response (UPR) pathway were studied in CaCo-2 enterocytes by incubating CaCo-2 cells with taurocholate micelles or taurocholate
micelles containing different concentrations of OA (0.25–1.0 mM). We show that OA effectively induces XBP1 mRNA splicing,
a key component of the UPR signaling, and the expression of BiP and mature ATF6 proteins in a concentration-dependent manner,
leading to the induction of endoplasmic reticulum (ER) stress and activation of the UPR. Interestingly, OA decreases NPC1L1
expression in a dose-dependent manner while it has no effects on ABCG5 and MTP mRNA level or SREBP-2, ABCG8, and ACAT2 protein
level. In CaCo-2 cells treated with 1.0 mM OA, both the NPC1L1 mRNA level and the NPC1L1 protein expression in brush-border
membrane fractions were decreased by 39% and 37%, respectively (P < 0.01). A dose of 1 mM dithiothreitol (DTT), a positive control for ER stress induction, also decreases NPC1L1 mRNA and
protein expression by 27% and 23%, respectively (P < 0.05). Furthermore, 4-phenyl-butyric acid, an UPR inhibitor, blocks OA- and DTT-induced reduction on NPC1L1 mRNA and protein
levels. The results suggest that OA down-regulates NPC1L1 mRNA and protein expression via the induction of the UPR, which
may play an important role in reducing intestinal cholesterol absorption. 相似文献
166.
Cui S Zhang D Jiang S Pu H Hu Y Guo H Chen M Su T Zhu C 《Fish & shellfish immunology》2011,31(2):173-181
Macrophage migration inhibitory factor (MIF) is an important cytokine and plays a crucial role as a pivotal regulator of innate immunity. In this study, a MIF cDNA was identified and characterized from the pearl oyster Pinctada fucata (designated as PoMIF). The full-length of PoMIF was 1544 bp and consisted of a 5'-untranslated region (UTR) of 45 bp, a 3'-UTR of 1139 bp with a polyadenylation signal (AATAAA) at 12 nucleotides upstream of the poly (A) tail. The open reading frame (ORF) of PoMIF was 360 bp which encoded a polypeptide of 120 amino acids with an estimated molecular mass of 13.3 kDa and a predicted pI of 6.1. SMART analysis showed that PoMIF contained the catalytic-sites P2 and K33 for tautomerase activity, a motif C??GSV?? for oxidoreductase activity and a MIF family signature D??PCGSVEVYSIGALG??. Homology analysis revealed that the PoMIF shared 40.3-65.5% similarity and 26.9-45.0% identity to other known MIF sequences. PoMIF mRNA was constitutively expressed in seven selected tissues of healthy pearl oysters, with the highest expression level in digestive gland. Eight hours after P. fucata was injected with Vibrio alginolyticus, the expression of PoMIF mRNA was significantly up-regulated in digestive gland, gills, hemocytes and intestine. The cDNA fragment encoding mature protein of PoMIF was subcloned to expression vector pRSET and transformed into Escherichia coli BL21 (DE3). The recombinant PoMIF (rPoMIF) was expressed and purified under optimized conditions. Function analysis showed that rPoMIF had oxidoreductase activity and could utilize dithiothreitol (DTT) as reductant to reduce insulin. 相似文献
167.
Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite, which has emerged as an important signaling mediator participating in the regulation of multiple cellular processes. The discovery of a family of S1P receptors, together with the more recently identified intracellular targets, has provided fundamental understanding of the multi-faceted actions of S1P. Evidence from both in vitro and in vivo studies has implicated the S1P signaling system in the control of immunity, inflammation and many associated diseases. Enigmatically, S1P appears to have both pro- and anti-inflammatory effects depending on the cell context. Here, we review this emerging area and argue for a pivotal role for S1P, as a key mediator of the cytokine network, acting through juxtacrine signaling in the immune system. 相似文献
168.
Shinichiro Maruyama Toshinobu Suzaki Andreas PM Weber John M Archibald Hisayoshi Nozaki 《BMC evolutionary biology》2011,11(1):105
Background
Euglenophytes are a group of photosynthetic flagellates possessing a plastid derived from a green algal endosymbiont, which was incorporated into an ancestral host cell via secondary endosymbiosis. However, the impact of endosymbiosis on the euglenophyte nuclear genome is not fully understood due to its complex nature as a 'hybrid' of a non-photosynthetic host cell and a secondary endosymbiont. 相似文献169.
目的:探讨重组干扰质粒pshRNA-COX-2对人肝癌细胞Hep3B裸鼠皮下移植瘤生长和肿瘤血管生成的抑制作用。方法:重组干扰质粒pshRNA-COX-2转染Hep3B细胞并筛选后,RT-PCR和Western blot检测COX-2mRNA和蛋白表达,RT-PCR检测VEGFmRNA表达。将被成功转染的Hep3B细胞种植于裸鼠皮下,测量肿瘤大小,4周后处死裸鼠,免疫组织化学法检测肿瘤组织中COX-2蛋白表达和肿瘤微血管密度(MVD)。结果:与未转染细胞相比,干扰组COX-2mRNA和蛋白表达抑制率分别为65.3%和52.8%(P<0.05),干扰组VEGFmRNA表达抑制率为56.5%(P<0.05)。干扰组瘤体大小明显小于阴性组和空白组(P<0.01)。干扰组COX-2得分和MVD均明显低于阴性组和空白组(P<0.01)。结论:pshRNA-COX-2通过抑制COX-2表达明显抑制人肝癌细胞Hep3B裸鼠皮下移植瘤生长和肿瘤血管生成。 相似文献
170.