全文获取类型
收费全文 | 5060篇 |
免费 | 271篇 |
国内免费 | 150篇 |
出版年
2023年 | 58篇 |
2022年 | 94篇 |
2021年 | 126篇 |
2020年 | 123篇 |
2019年 | 149篇 |
2018年 | 156篇 |
2017年 | 106篇 |
2016年 | 125篇 |
2015年 | 173篇 |
2014年 | 263篇 |
2013年 | 345篇 |
2012年 | 225篇 |
2011年 | 253篇 |
2010年 | 213篇 |
2009年 | 234篇 |
2008年 | 246篇 |
2007年 | 268篇 |
2006年 | 225篇 |
2005年 | 211篇 |
2004年 | 194篇 |
2003年 | 168篇 |
2002年 | 179篇 |
2001年 | 131篇 |
2000年 | 93篇 |
1999年 | 73篇 |
1998年 | 80篇 |
1997年 | 85篇 |
1996年 | 92篇 |
1995年 | 47篇 |
1994年 | 64篇 |
1993年 | 44篇 |
1992年 | 44篇 |
1991年 | 45篇 |
1990年 | 50篇 |
1989年 | 37篇 |
1988年 | 33篇 |
1987年 | 36篇 |
1986年 | 22篇 |
1985年 | 40篇 |
1984年 | 43篇 |
1983年 | 29篇 |
1982年 | 43篇 |
1981年 | 50篇 |
1980年 | 39篇 |
1979年 | 40篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 7篇 |
1973年 | 11篇 |
排序方式: 共有5481条查询结果,搜索用时 31 毫秒
991.
目的:构建以减毒沙门氏菌为载体的小鼠肝炎病毒DNA疫苗,研究该疫苗的免疫原性。方法:以小鼠肝炎病毒S1基因的重组真核表达质粒pVAX1—S1免疫BALB/c小鼠,ELISA检测其诱导抗体产生情况;再将重组质粒pVAX1—S1电转化到减毒鼠伤寒沙门氏菌SL7207中,构建运送S1基因的重组减毒沙门氏菌SL7207(pVAX1—S1),口服免疫BALB/c小鼠,间接免疫荧光试验鉴定减毒沙门氏菌运送的DNA疫苗的免疫原性。结果:与pVAX1空载体对照组相比,重组真核表达质粒pVAX1—S1免疫组二免及三免后抗体水平分别存在显著性差异(P〈0.05)和极显著性差异(P〈0.01)。减毒沙门氏菌运送的DNA疫苗SL7207(pVAX1—S1)诱导小鼠产生了特异性的血清抗体。结论:构建的重组减毒沙门氏菌SL7207(pVAX1—S1)具有良好的免疫原性,可诱导小鼠产生特异性的体液免疫应答。这为进一步研制冠状病毒新型基因疫苗奠定了基础。 相似文献
992.
Niisato E Nagai J Yamashita N Abe T Kiyonari H Goshima Y Ohshima T 《Developmental neurobiology》2012,72(11):1447-1457
Collapsin response mediator proteins (CRMPs) are a family of cytosolic phosphoproteins that consist of 5 members (CRMP 1–5). CRMP2 and CRMP4 regulate neurite outgrowth by binding to tubulin heterodimers, resulting in the assembly of microtubules. CRMP2 also mediates the growth cone collapse response to the repulsive guidance molecule semaphorin‐3A (Sema3A). However, the role of CRMP4 in Sema3A signaling and its function in the developing mouse brain remain unclear. We generated CRMP4?/? mice in order to study the in vivo function of CRMP4 and identified a phenotype of proximal bifurcation of apical dendrites in the CA1 pyramidal neurons of CRMP4?/? mice. We also observed increased dendritic branching in cultured CRMP4?/? hippocampal neurons as well as in cultured cortical neurons treated with CRMP4 shRNA. Sema3A induces extension and branching of the dendrites of hippocampal neurons; however, these inductions were compromised in the CRMP4?/? hippocampal neurons. These results suggest that CRMP4 suppresses apical dendrite bifurcation of CA1 pyramidal neurons in the mouse hippocampus and that this is partly dependent on Sema3A signaling. © 2012 Wiley Periodicals, Inc. Develop Neurobiol, 2012 相似文献
993.
994.
995.
To assess the contribution of singlet molecular oxygen [O2 (1Δg)] to lipid peroxidation in vivo, this study combined gas chromatography-mass spectrometry with thin layer chromatography to analyse peroxidized lipids in the skin of hairless mice. Hydroxyoctadecenoate isomers and unconjugated hydroxyoctadecadienoate isomers derived from peroxidized oleic acid and linoleic acid, respectively, which are specific to O2 (1Δg)-dependent oxygenation, were detected in the skin of live mice under ordinary feeding conditions. Short-term ultraviolet A (UVA)-irradiation of the skin in vivo elevated levels of the unconjugated hydroxyoctadecadienoate isomers significantly, whereas the irradiation of skin homogenate in vitro increased levels of all isomers derived from both O2 (1Δg) and free radical-dependent oxygenation to a much greater extent. This is the first report to demonstrate the occurrence of O2 (1Δg)-specific oxygenation of unsaturated fatty acids in living animals. 相似文献
996.
Carol J. Quaife Gary W. Hoyle Glenda J. Froelick Seth D. Findley E. Edward Baetge Richard R. Behringer Joseph P. Hammang Ralph L. Brinster Richard D. Palmiter 《Transgenic research》1994,3(6):388-400
We cloned and sequenced the mouse phenylethanolamineN-methyltransferase (PNMT) gene which encodes the enzyme that catalyses the conversion of norepinephrine to epinephrine. The ability of various length sequences flanking the mouse or human PNMT genes to direct expression of reporter genes in transgenic mice was examined. We show that 9 kb of 5 flanking sequences from the cloned mouse PNMT gene can direct expression of theEscherichia coli -galactosidase (lacZ) gene to predicted regions of the adrenal, eye can direct in the adult transgenic mouse. The transgene was also expressed during development, in the myelencephalon, adrenal medulla and dorsal root ganglia. PNMT-producing cells were ablated by expression of the diphtheria toxin (DT-A) gene driven by the human PNMT promoter, resulting in abnormalities in the adrenal medulla, eye and testis. The hPNMT8
kb-DT-A line presents a model with which to examine the developmental ramifications of deletion of PNMT-producing cell populations from the adrenal medulla and retina. 相似文献
997.
电针对帕金森病模型小鼠黑质铁染色细胞和铁蛋白表达的影响 总被引:1,自引:0,他引:1
目的探讨电针防治帕金森病的作用机制。方法采用1-甲基-4-苯基1,2,3,6四氢吡啶腹腔注射建立帕金森病小鼠模型,利用组织化学技术以及免疫组织化学技术观察电针对帕金森病小鼠脑黑质铁染色细胞和铁蛋白表达的影响。结果模型组1周、2周、4周小鼠黑质铁染色阳性细胞的数量较正常组明显增多,染色强度也明显增强(P〈0.001;P〈0.01;P〈0.001),电针在3个存活期内均可明显减少帕金森病小鼠黑质铁阳性细胞的数量和染色强度(P〈0.001;P〈0.05;P〈0.001);模型组1周、2周黑质部位铁蛋白的表达与正常组相比都有不同程度下降(P〈0.01;P〈0.001),而电针组2周帕金森病小鼠黑质铁蛋白的表达与模型组相比显著增加(P〈0.01)。结论电针可以通过降低脑内铁的含量,同时增加铁蛋白的表达,从而提高帕金森病模型小鼠脑抗氧化能力,达到保护黑质多巴胺能神经元的目的。 相似文献
998.
不同遗传背景的小鼠2-细胞期胚胎经过电融合后,胚胎的融合效率和四倍体胚胎的发育能力存在着一定的差异。本试验采用C57(C57×C57)、ICR(ICR×ICR)、BALB/c(BALB/c×BALB/c)、B6D2F2(B6D2F1×B6D2F1)、B6C3D2F2(B6C3F1×B6D2F1)品系的二倍体2-细胞期胚胎在相同的条件下经过电融合处理,结果表明:小鼠四倍体胚胎的获得效率受小鼠遗传背景的影响,远交系小鼠胚胎B6D2F2和B6C3D2F2的融合率显著高于近交系C57,ICR和BALB/c(P<0.05);四倍体胚胎在体外的发育情况也受其遗传背景的影响,在桑椹胚发育率和囊胚发育率上B6D2F2和B6C3D2F2品系的四倍体胚胎都显著高于C57和BALB/c品系的四倍体胚胎(P<0.05);杂合和纯系遗传背景的小鼠四倍体胚胎囊胚细胞数目相比具有显著差异(P<0.05或P<0.01);不同遗传背景的小鼠四倍体胚胎着床率间不存在显著差异(P>0.05);杂合背景的小鼠四倍体胚胎得到5只发育至13.5dpc(dayspostcoitum,dpc)的胎儿,纯合背景的小鼠四倍体胚胎得到0只发育至11dpc的胎儿。 相似文献
999.
目的 研究不同培养条件分离和克隆小鼠ES细胞集落的效率。方法 以PMEF饲养层、NIH3T3细胞饲养层或培养液中加入LIF为培养条件 ,分离和克隆昆明小鼠ES细胞集落 ,比较其效率。结果 饲养层的培养条件明显优于培养液中加入LIF的培养条件 ;有饲养层的培养条件下 ,桑椹胚的ES细胞集落出现率显著低于囊胚 ;两种饲养层培养囊胚 ,其ES细胞集落的出现率差异无显著性。结论 以PMEF或NIH3T3细胞作饲养层 ,培养昆明小鼠的囊胚 ,适时离散ICM ,是比较理想的分离ES细胞集落的方法。 相似文献
1000.
Testa G Schaft J van der Hoeven F Glaser S Anastassiadis K Zhang Y Hermann T Stremmel W Stewart AF 《Genesis (New York, N.Y. : 2000)》2004,38(3):151-158
Alteration of the mouse genome through homologous recombination in embryonic stem (ES) cells is the most accurate and versatile way to dissect gene function in a vertebrate model. Most often, a selectable marker is used to create a knockout allele by replacing an essential part of the gene. However, knockout strategies are limited because the mutation is present constitutively. Conditional approaches based on the Cre-loxP site-specific recombination (SSR) system address this limitation; however, it requires that all parts of the targeted gene remain in ES cells. Here we report success with a "knockout-first" strategy that ablates gene function by insertion of RNA processing signals without deletion of any of the target gene. Incorporation of site-specific recombination target sites creates a multipurpose allele for both knockout and conditional applications. 相似文献