全文获取类型
收费全文 | 8543篇 |
免费 | 672篇 |
国内免费 | 281篇 |
出版年
2024年 | 12篇 |
2023年 | 61篇 |
2022年 | 158篇 |
2021年 | 259篇 |
2020年 | 169篇 |
2019年 | 240篇 |
2018年 | 298篇 |
2017年 | 211篇 |
2016年 | 371篇 |
2015年 | 527篇 |
2014年 | 599篇 |
2013年 | 551篇 |
2012年 | 770篇 |
2011年 | 734篇 |
2010年 | 463篇 |
2009年 | 430篇 |
2008年 | 505篇 |
2007年 | 465篇 |
2006年 | 420篇 |
2005年 | 369篇 |
2004年 | 362篇 |
2003年 | 326篇 |
2002年 | 314篇 |
2001年 | 128篇 |
2000年 | 95篇 |
1999年 | 100篇 |
1998年 | 84篇 |
1997年 | 63篇 |
1996年 | 49篇 |
1995年 | 42篇 |
1994年 | 37篇 |
1993年 | 32篇 |
1992年 | 28篇 |
1991年 | 30篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1972年 | 6篇 |
1971年 | 5篇 |
1969年 | 4篇 |
排序方式: 共有9496条查询结果,搜索用时 359 毫秒
1.
Fang Chang An Yan Li-Na Zhao Wei-Hua Wu Zhenbiao Yang 《植物学报(英文版)》2007,49(8):1261-1270
A tip-focused Ca^2+ gradient is tightly coupled to polarized pollen tube growth, and tip-localized influxes of extracellular Ca^2+ are required for this process. However the molecular identity and regulation of the potential Ca^2+ channels remains elusive. The present study has implicated CNGC18 (cyclic nucleotide-gated channel 18) in polarized pollen tube growth, because its overexpression induced wider and shorter pollen tubes. Moreover, CNGC18 overexpression induced depolarization of pollen tube growth was suppressed by lower extracellular calcium ([Ca^2+]ex). CNGC18-yellow fluorescence protein (YFP) was preferentially localized to the apparent post-Golgi vesicles and the plasma membrane (PM) in the apex of pollen tubes. The PM localization was affected by tip-localized ROP1 signaling. Expression of wild type ROP1 or an active form of ROP1 enhanced CNGC18-YFP localization to the apical region of the PM, whereas expression of RopGAP1 (a ROP1 deactivator) blocked the PM localization. These results support a role for PM-Iocalized CNGC18 in the regulation of polarized pollen tube growth through its potential function in the modulation of calcium influxes. 相似文献
2.
3.
Secretion of Recombinant Pediocin PA-1 by Bifidobacterium longum, Using the Signal Sequence for Bifidobacterial α-Amylase
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gi-Seong Moon Yu-Ryang Pyun Myeong Soo Park Geun Eog Ji Wang June Kim 《Applied microbiology》2005,71(9):5630-5632
A recombinant DNA, encoding the chimeric protein of the signal sequence for bifidobacterial α-amylase mature pediocin PA-1, was introduced into Bifidobacterium longum MG1. Biologically active pediocin PA-1 was successfully secreted from the strain and showed bactericidal activity against Listeria monocytogenes and the same molecular mass as native pediocin PA-1. 相似文献
4.
5.
Circulating tumor cells (CTCs), shed from primary tumors and disseminated into peripheral blood, are playing a major role in metastasis. Even after isolation of CTCs from blood, the target cells are mixed with a population of other cell types. Here, we propose a new method for analyses of cell mixture at the single-cell level using a microfluidic device that contains arrayed electroactive microwells. Dielectrophoretic (DEP) force, induced by the electrodes patterned on the bottom surface of the microwells, allows efficient trapping and stable positioning of single cells for high-throughput biochemical analyses. We demonstrated that various on-chip analyses including immunostaining, viability/apoptosis assay and fluorescent in situ hybridization (FISH) at the single-cell level could be conducted just by applying specific reagents for each assay. Our simple method should greatly help discrimination and analysis of rare cancer cells among a population of blood cells. 相似文献
6.
Summary Production of tryptophan by a temperature sensitive recombinant microorganism (Escherichia coli W3110 trpLDtrpR
ts
tna
– (pCRT185)) was investigated. In a single-stage continous culture, at an elevated temperature, 42°C (derepressed condition), tryptophan concentration increased in an early phase of the fermentation, and then gradually decreased with time. The reduction in the production rate was mostly due to the segregation of the plasmid and subsequent increase of plasmid-free cells. However, the plasmid could be maintained stable at 37°C, with repressed condition oftrp-operon, over 200 generations. A two-stage continuous culture system, i.e. cell growth was maintained in the first stage at 37°C and gene expression was induced in the second stage at 42°C, was therefore tested to improve the performance of the fermentation system. Operation of the two-stage system showed that the plasmid stability was significantly improved, and the specific rate of tryptophan production was maintained almost constant for more than 500 hours in the second stage. 相似文献
7.
Gynheung An 《Molecular & general genetics : MGG》1987,207(2-3):210-216
Summary Expression of the three chlorophyll a/b binding protein (cab) genes of Arabidopsis thaliana was studied in transformed tobacco tissues. For each cab gene, approximately 1000 bp of the promoter region plus a portion of the structural gene was inserted into a promoter-expression vector such that a translational fusion between the cab gene and the promoter-less chloramphenicol acetyltransferase (cat) gene was formed. The constructed molecules were introduced into either cultured tobacco cells or tobacco leaves and the promoter activity was monitored as chloramphenicol acetyltransferase activity. The light-grown tissues exhibited 1.5- to 60-fold greater promoter activity than did dark-grown tissues. Expression of the cab promoters was tissue specific: activities were much stronger in green leaves than other tissues. The cab promoters were almost equally active in transformed calli or shoots derived from leaves. However, in cultured tobacco cells, one promoter was two to three times stronger than the other two. The chimeric gene fusion, cab-cat, segregated in the F1 generation as a dominant Mendelian trait. 相似文献
8.
Three distinct regulatory elements comprise the upstream promoter region of the nopaline synthase gene 总被引:5,自引:0,他引:5
Summary Fine deletion mutants were generated in the upstream control region of the nopaline synthase (nos) promoter to define the position and role of upstream regulatory elements. The results indicated that the 8 bp sequence (CAGAAACC) at -106/-113 and its inverted repeat (GGTTTCTG) at -140/-147 are important for promoter function. The downstream element appears more important than the upstream element since deletion of the former reduced promoter activity more significantly than deletion of the latter. Deletion of the element alone, however, did not abolish promoter function, whereas, deletion of the 10 bp potential Z-DNA-forming (Z) element located between the repeat elements nullified promoter activity. Therefore, it appears that the Z element is an essential upstream regulator and the repeated elements are upstream modulators of the nos promoter. These elements are functionally distinct since alteration of stereospecificity or insertion of short oligonucleotides between the elements did not significantly influence promoter activity. These regulatory elements were unable to function from 200 bp upstream of the CCAAT-TATA box region. 相似文献
9.
10.