全文获取类型
收费全文 | 4539篇 |
免费 | 468篇 |
国内免费 | 1篇 |
出版年
2022年 | 24篇 |
2021年 | 46篇 |
2020年 | 24篇 |
2018年 | 53篇 |
2017年 | 45篇 |
2016年 | 86篇 |
2015年 | 120篇 |
2014年 | 143篇 |
2013年 | 176篇 |
2012年 | 234篇 |
2011年 | 268篇 |
2010年 | 171篇 |
2009年 | 140篇 |
2008年 | 231篇 |
2007年 | 227篇 |
2006年 | 237篇 |
2005年 | 258篇 |
2004年 | 252篇 |
2003年 | 211篇 |
2002年 | 236篇 |
2001年 | 54篇 |
2000年 | 45篇 |
1999年 | 64篇 |
1998年 | 78篇 |
1997年 | 64篇 |
1996年 | 49篇 |
1995年 | 52篇 |
1994年 | 50篇 |
1993年 | 47篇 |
1992年 | 37篇 |
1991年 | 44篇 |
1990年 | 33篇 |
1989年 | 48篇 |
1988年 | 35篇 |
1987年 | 43篇 |
1986年 | 30篇 |
1985年 | 49篇 |
1984年 | 50篇 |
1983年 | 32篇 |
1982年 | 56篇 |
1981年 | 49篇 |
1980年 | 53篇 |
1979年 | 54篇 |
1978年 | 39篇 |
1977年 | 37篇 |
1976年 | 40篇 |
1975年 | 33篇 |
1974年 | 36篇 |
1973年 | 38篇 |
1969年 | 24篇 |
排序方式: 共有5008条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
56.
57.
58.
Function of the human immunodeficiency virus types 1 and 2 Rev proteins is dependent on their ability to interact with a structured region present in env gene mRNA. 总被引:15,自引:10,他引:5
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The interaction of the human immunodeficiency virus type 1 (HIV-1) Rev protein with a structured region in env mRNA (the Rev-responsive element [RRE]) mediates the export of structural mRNAs from the nucleus to the cytoplasm. We demonstrated that unlike HIV-1 Rev, which functions with both the HIV-1 and HIV-2 RREs, HIV-2 Rev functions only with the HIV-2 RRE. Rev-RRE binding studies suggested that the lack of nonreciprocal complementation stems from the inability of HIV-2 Rev to interact with HIV-1 RRE RNA. Maintenance of RNA secondary structure, rather than the primary nucleotide sequence, appeared to be the major determinant for interaction of both HIV-1 and HIV-2 Rev with the HIV-2 RRE. Moreover, the binding domain of the HIV-2 RRE recognized by HIV-1 Rev was dissimilar to the binding domain of the HIV-1 RRE, in terms of both secondary structure and primary nucleotide sequence. Our results support the hypothesis that function of HIV Rev proteins and possibly the functionally similar Rex proteins encoded by the human T-cell leukemia viruses (HTLVs) HTLV-I and HTLV-II is controlled by the presence of RNA secondary structure generated within the RRE RNA. 相似文献
59.
The kinetics of gravitropism and of amyloplast sedimentation were studied in dark-grown protonemata of the moss Ceratodon purpureus (Hedw.) Brid. The protonemata grew straight up at a rate of 20–25 m·h– in nutrient-supplemented agar. After they were oriented to the horizontal, upward curvature was first detected after 1–1.5 h and reached 84° by 24 h. The tip cells exhibited an amyloplast zonation, with a tip cluster of nonsedimenting amyloplasts, an amyloplast-free zone, and a zone with pronounced amyloplast sedimentation. This latter zone appears specialized more for lateral than for axial sedimentation since amyloplasts sediment to the lower wall in horizontal protonemata but do not fall to the basal wall in vertical protonemata. Amyloplast sedimentation started within 15 min of gravistimulation; this is within the 12–17-min presentation time. The data support the hypothesis that some amyloplasts function as statoliths in these cells.This work was supported by the National Aeronautics and Space Administration grant NAGW-780. We thank Professor E. Hartmann and J. Schwuchow for providing Ceratodon cultures, Dr. John Z. Kiss and Jeff Young for valuable discussions, and Professor Rainer Hertel (University of Freiburg, FRG) for bringing this material to our attention. 相似文献
60.
Fred J. Genthner Janeshwar Upadhyay Robert P. Campbell Barbara R. Sharak Genthner 《Microbial ecology》1990,20(1):283-288
Culturable counts of antibiotic resistant, genetically engineeredPseudomonas fluorescens were determined on antibiotic-containing plate count agar during starvation in water. Prior to starvation, colony counts
obtained on all media separated into two groups. The mean of the colony counts on plate count agar with or without tetracycline
(4.9 × 106 ml−1) was significantly higher than the mean colony counts on plate count agar containing either nalidixic acid or nalidixic acid
plus tetraclycline (2.5×106 ml−1). After 20 days of starvation the highest mean colony counts continued to be obtained on plate count agar (7.2 × 106 ml−1) with slightly, but significantly, lower counts obtained on plate count agar containing either nalidixic acid (5.6 × 106 ml−1) or tetraclycline (1.5×106 ml−1). A combination of nalidixic acid and tetracycline in plate count agar, however, dramatically reduced colony counts (8.3
× 102 ml−1) after this starvation period. The addition of catalase to plate count agar containing nalidixic acid and tetracycline negated
the effect caused by this combination of antibiotics. When colony counts obtained over the entire 20 day incubation were considered,
the addition of MgSO4 to plate count agar containing nalidixic acid and tetracycline resulted in a significant increase in colony counts. Other
combinations of antibiotics, nalidixic acid+carbenicillin, nalidixic acid+kanamycin, streptomycin+tetracycline, streptomycin+carbenicillin,
rifampicin+tetracycline, rifampicin+carbenicillin, and rifampicin+kanamycin, did not inhibit colony formation of starved cells.
Antibiotic resistant strains ofP. putida andEscherichia coli also displayed sensitivity to the combination of nalidixic acid and tetracycline in plate count agar after starvation. 相似文献