全文获取类型
收费全文 | 9244篇 |
免费 | 700篇 |
国内免费 | 991篇 |
专业分类
10935篇 |
出版年
2024年 | 24篇 |
2023年 | 124篇 |
2022年 | 312篇 |
2021年 | 508篇 |
2020年 | 379篇 |
2019年 | 450篇 |
2018年 | 375篇 |
2017年 | 276篇 |
2016年 | 408篇 |
2015年 | 582篇 |
2014年 | 700篇 |
2013年 | 782篇 |
2012年 | 888篇 |
2011年 | 765篇 |
2010年 | 491篇 |
2009年 | 465篇 |
2008年 | 531篇 |
2007年 | 466篇 |
2006年 | 386篇 |
2005年 | 297篇 |
2004年 | 293篇 |
2003年 | 260篇 |
2002年 | 213篇 |
2001年 | 146篇 |
2000年 | 130篇 |
1999年 | 129篇 |
1998年 | 82篇 |
1997年 | 62篇 |
1996年 | 52篇 |
1995年 | 60篇 |
1994年 | 64篇 |
1993年 | 40篇 |
1992年 | 36篇 |
1991年 | 43篇 |
1990年 | 31篇 |
1989年 | 23篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Liu Na Si Yanhong Zhang Ying Guo Shoudong Qin Shucun 《Journal of physiology and biochemistry》2021,77(4):683-694
Journal of Physiology and Biochemistry - Cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) belong to the same gene family. Liver-specific expression of CETP... 相似文献
92.
【目的】探讨新城疫病毒全基因序列中非编码序列的分子演化规律。【方法】结合本研究室2012年自产蛋下降鸭群中分离测序的一株鸭源新城疫病毒全序列,从GenBank下载35株不同基因型新城疫病毒全长cDNA序列,获取非编码序列,分别绘制引导序列、尾随序列、F-HN及HN-L基因间隔序列(IGS)的遗传进化树,比较编码基因内5’及3’UTR序列核苷酸序列替代特点。【结果】非编码序列的长度及位置高度保守,而其核苷酸基因序列在不断发生变异,且变异趋势与编码基因序列相一致。【结论】新城疫病毒在整个基因组上编码和非编码序列同步发生变异。 相似文献
93.
草鱼呼肠孤病毒RNA聚合酶基因的表达与产物纯化 总被引:1,自引:0,他引:1
草鱼呼肠孤病毒是引起草鱼出血病的主要病原,隶属于呼肠孤病毒科水生呼肠孤病毒属.序列分析表明,GCRV S2 片段长为3 877核苷酸,编码一个分子量为138kDa 的蛋白VP2,具有RNA聚合酶性质.为进一步了解该病毒 RNA聚合酶特性,本研究在对GCRV RNA聚合酶基因(GCRV-RdRp)保守区(约1.5kb)重组质粒pR/RRp高效表达的基础上,分别构建了编码GCRV RNA聚合酶保守区N端与C端部分基因的 pR/RRpN及pR/RRpC重组表达载体,并在原核细胞中获得成功表达.筛选的重组表达菌株经IPTG诱导培养,得到分子量分别为98kDa、103kDa的目的表达融合蛋白.Western blot分析表明,该表达产物与兔抗GCRV-VP2血清呈阳性反应.通过ProBond柱亲和层析,纯化了融合有6个组氨酸的重组表达产物,并获得约90%纯的目的蛋白.上述结果为GCRV RNA聚合酶特性分析提供了依据. 相似文献
94.
Yongjun Du Ping Li Zhiqun Chen Yanru Lin Yahong Wang Yuanxia Qin 《Entomologia Experimentalis et Applicata》2013,146(3):357-363
The sex pheromone of Phyllonorycter ringoniella (Matsumura) (Lepidoptera: Gracillariidae) has been identified to be a blend of (Z)‐10‐tetradecenyl acetate (Z10‐14:OAc) and E4,Z10‐tetradecadienyl acetate (E4,Z10‐14:OAc) in Japan, Korea, and China. However, the commercial product based on previous results is not attractive enough to be used for monitoring and controlling apple leafminer populations in the field. We re‐investigated the attractiveness of the two pheromone components, singly and in blends, in apple orchards in Shangdong and Shaanxi, the main apple‐growing provinces in China. Our results revealed that Z10‐14:OAc alone was not attractive to P. ringoniella male moths in the field, but E4,Z10‐14:OAc alone not only was strongly attractive but caught more males than any of the blends of Z10‐14:OAc and E4,Z10‐14:OAc tested. The most attractive blend ratios differed slightly for the two locations. No clear dose–response relationship was obtained for the 2:8 blend of Z10‐14:OAc and E4,Z10‐14:OAc. However, the dose–response field study of E4,Z10‐14:OAc alone showed that 1 mg per lure achieved the highest moth catch. These findings differ from the previous report of the best pheromone blend in China. Our data showed that E4,Z10‐14:OAc is the major component of the pheromone of P. ringoniella. 相似文献
95.
96.
Yahui Gao Jianping Jiang Shaohua Yang Jie Cao Bo Han Yachun Wang Yi Zhang Ying Yu Shengli Zhang Qin Zhang Lingzhao Fang Bonnie Cantrell Dongxiao Sun 《BMC genomics》2018,19(1):972
Background
Paratuberculosis is a contagious, chronic and enteric disease in ruminants, which is caused by Mycobacterium avium subspecies paratuberculosis (MAP) infection, resulting in enormous economic losses worldwide. There is currently no effective cure for MAP infection or a vaccine, it is thus important to explore the genetic variants that contribute to host susceptibility to infection by MAP, which may provide a better understanding of the mechanisms of paratuberculosis and benefit animal genetic improvement. Herein we performed a genome-wide association study (GWAS) to identify genomic regions and candidate genes associated with susceptibility to MAP infection in dairy cattle.Results
Using Illumina Bovine 50?K (54,609 SNPs) and GeneSeek HD (138,893 SNPs) chips, two analytical approaches were performed, GRAMMAR-GC and ROADTRIPS in 937 Chinese Holstein cows, among which individuals genotyped by the 50?K chip were imputed to HD SNPs with Beagle software. Consequently, 15 and 11 significant SNPs (P?<?5?×?10??5) were identified with GRAMMAR-GC and ROADTDRIPS, respectively. A total of 10 functional genes were in proximity to (i.e., within 1?Mb) these SNPs, including IL4, IL5, IL13, IRF1, MyD88, PACSIN1, DEF6, TDP2, ZAP70 and CSF2. Functional enrichment analysis showed that these genes were involved in immune related pathways, such as interleukin, T cell receptor signaling pathways and inflammatory bowel disease (IBD), implying their potential associations with susceptibility to MAP infection. In addition, by examining the publicly available cattle QTLdb, a previous QTL for MAP was found to be overlapped with one of regions detected currently at 32.5?Mb on BTA23, where the TDP2 gene was anchored.Conclusions
In conclusion, we identified 26 SNPs located on 15 chromosomes in the Chinese Holstein population using two GWAS strategies with high density SNPs. Integrated analysis of GWAS, biological functions and the reported QTL information helps to detect positional candidate genes and the identification of regions associated with susceptibility to MAP traits in dairy cattle.97.
Zidong Zhang Shuhui Chen Xiujie Ji Chen Qin Huimin Wang Peitao Xie Runhua Fan 《Plasmonics (Norwell, Mass.)》2016,11(2):373-379
Metamaterials are artificial periodic structures with negative permittivity and permeability. Several interesting properties can be obtained in metamaterials, such as negative index behavior, which can be used for building perfect lenses, cloaking, antennas, etc. As the metamaterial’s properties are determined by its structure, the key challenge is to reduce the fabrication cost of the periodic structure on the micrometer or nanometer scale for realistic applications. In this paper, we experimentally demonstrate a new one-step method for the fabrication of a large-area infrared metamaterial at extremely low cost. A metallic mesh is used as a shadow mask during the pulsed laser deposition (PLD) process to fabricate a FeNi/SiC/FeNi multilayer sandwich structure on Si substrate (cm2 level). The sample shows a strong absorption peak in the infrared frequency range, and the absorption intensity changes with the sample’s geometry. 相似文献
98.
99.
100.
A 3.5-kb DNA fragment containing the dnaA region of Mycobacterium smegmatis has been hypothesized to be the chromosomal origin of replication or oriC (M. Rajagopalan et al., J. Bacteriol. 177:6527-6535, 1995). This region included the rpmH gene, the dnaA gene, and a major portion of the dnaN gene as well as the rpmH-dnaA and dnaA-dnaN intergenic regions. Deletion analyses of this region revealed that a 531-bp DNA fragment from the dnaA-dnaN intergenic region was sufficient to exhibit oriC activity, while a 495-bp fragment from the same region failed to exhibit oriC activity. The oriC activities of plasmids containing the 531-bp sequence was less than the activities of those containing the entire dnaA region, suggesting that the regions flanking the 531-bp sequence stimulated oriC activity. The 531-bp region contained several putative nine-nucleotide DnaA-protein recognition sequences [TT(G/C)TCCACA] and a single 11-nucleotide AT-rich cluster. Replacement of adenine with guanine at position 9 in five of the putative DnaA boxes decreased oriC activity. Mutations at other positions in two of the DnaA boxes also decreased oriC activity. Deletion of the 11-nucleotide AT-rich cluster completely abolished oriC activity. These data indicate that the designated DnaA boxes and the AT-rich cluster of the M. smegmatis dnaA-dnaN intergenic region are essential for oriC activity. We suggest that M. smegmatis oriC replication could involve interactions of the DnaA protein with the putative DnaA boxes as well as with the AT-rich cluster. 相似文献