全文获取类型
收费全文 | 2125篇 |
免费 | 104篇 |
出版年
2022年 | 12篇 |
2021年 | 19篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 21篇 |
2017年 | 20篇 |
2016年 | 27篇 |
2015年 | 58篇 |
2014年 | 74篇 |
2013年 | 146篇 |
2012年 | 115篇 |
2011年 | 104篇 |
2010年 | 61篇 |
2009年 | 58篇 |
2008年 | 91篇 |
2007年 | 112篇 |
2006年 | 92篇 |
2005年 | 87篇 |
2004年 | 94篇 |
2003年 | 113篇 |
2002年 | 108篇 |
2001年 | 51篇 |
2000年 | 54篇 |
1999年 | 53篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 25篇 |
1993年 | 23篇 |
1992年 | 35篇 |
1991年 | 47篇 |
1990年 | 54篇 |
1989年 | 48篇 |
1988年 | 37篇 |
1987年 | 29篇 |
1986年 | 30篇 |
1985年 | 24篇 |
1984年 | 19篇 |
1983年 | 11篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1976年 | 10篇 |
1970年 | 12篇 |
1969年 | 10篇 |
1968年 | 9篇 |
1967年 | 8篇 |
排序方式: 共有2229条查询结果,搜索用时 718 毫秒
41.
The primary structure of human Rieske iron-sulfur protein of mitochondrial cytochrome bc1 complex deduced from cDNA analysis 总被引:2,自引:0,他引:2
We isolated a cDNA encoding human Rieske Fe-S protein of mitochondrial cytochrome bc1 complex from a fibroblast cDNA library by colony hybridization. The cDNA contains the nucleotide sequence encoding all of the amino acids (274 residues) comprising the putative precursor to the protein. Based on the known amino acid sequence of bovine Rieske Fe-S protein, the N-terminal extension sequence is presumed to be composed of 78 amino acids with a molecular weight of 8053. The mature protein consists of the same number of amino acid residues as that of its rat and bovine counterparts, having a homology of about 92% with the latter. 相似文献
42.
Summary
Panax ginseng hairy root cultures were established by infecting petiole segments with Agrobacterium rhizogenes strain 15834. Hairy root segments including root tips placed onto phytohormone-free 1/2 Murashige and Skoog solid medium and stored at 4 °C in the dark for 4 months, resumed elongation when the temperature was raised to 25 °C in the dark. For cryopreservation, a vitrification method was applied. Root tips precultured with 0.1 mg/l 2,4-D for 3 days and dehydrated with PVS2 solution for 8 minutes prior to immersion into liquid nitrogen had a survival rate of 60 % and could regenerate. The hairy roots regenerated from cryopreserved root tips grew well and showed the same ginsenoside productivity and patterns as those of the control hairy roots cultured continuously at 25 °C. The conservation of T-DNAs in the regenerated hairy roots was proved by PCR analysis.Abbreviations 1/2 MS
a half strength Murashige and Skoog (1962)
- B5
Gamborg B5 (Gamborg et al. 1968)
- WP
woody plant (Lloyd and McCown 1980)
- RC
root culture (Thomas and Davey 1982)
- RCI
root culture medium containing 100 mg/l myoinositol
- HF
phytohormone-free
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- TIBA
2,3,5-triiodobenzoic acid
- PCR
polymerase chain reaction
- PVS2
plant vitrification solution 2 (Sakai et al., 1990)
- FDA
fluorecein diacetate 相似文献
43.
Myosin molecules contacting an actin filament in the presence of ATP were found to regulate the filamental fluctuations due to ATP hydrolysis in a communicative manner along the filament. As an evidence of the occurrence of the communication, ATP-activated fluctuating displacements of the filament in the direction perpendicular to its longitudinal axis were identified to propagate at a finite velocity not less than about 0.2 μm/s unidirectionally along the filament. 相似文献
44.
Analysis of the multi-stem clump structure ofLitsea japonica Juss. growing in a coastal dwarf forest
The multi-stem clump structure of a coastal dwarf forest dominated byLitsea japonica Juss. was investigated in order to clarify the sprouting characteristics and self-maintenance of clumps by stem alternation.
The size and age distribution of multi-stem clumps were analyzed using cumulative relative frequency curves.L. japonica had a large number of stems and an even height distribution or young age-biased distribution of stems within a clump. These
results indicated the sequential flushing of sprouts at high frequency. Height distribution within a clump ofL. japonica was relatively even compared to other species. This clump structure suggested the stable self-maintenance of individuals
in all ranges of size and age without disturbances. It originated specific sprouting characteristics as a response to the
severe stress of salty wind.Ardisia sieboldii Miq. had few stems within a clump. Although the stem height distribution of large individuals tended to be even, most clumps
had a large size-biased distribution of stem height which indicated simultaneous sprouting. From this structure, sprouts of
this species were thought to be of less significance in the stable self-maintenance of individuals thanL. Japonica. 相似文献
45.
M. Sunairi H. Tsuchiya T. Tsuchiya Y. Omura Y. Koyanagi M. Ozawa N. Iwabuchi H. Murooka M. Nakajima 《Journal of applied microbiology》1995,79(2):225-229
Anaaki disease causes severe damage to the red algae Porphyra yezoensis from which the Japanese traditional food 'nori'is produced. The causative agent of anaaki disease was isolated by several repeats of single-colony isolation and infection experiments, and was identified as Flavobacterium sp. LAD-1. The bacterium showed hydrolytic activity toward porphyran but not toward other polysaccharides composing the thallus of Porphyra , such as β-1,3-xylan or β-1,4-mannan. The bacterium also showed β-D-galactosidase activity. 相似文献
46.
Comparison of DNA methylation patterns among mouse cell lines by restriction landmark genomic scanning. 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Molecular and cellular biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
J Kawai K Hirose S Fushiki S Hirotsune N Ozawa A Hara Y Hayashizaki S Watanabe 《Molecular and cellular biology》1994,14(11):7421-7427
Restriction landmark genomic scanning (RLGS) is a novel method which enables us to simultaneously visualize a large number of loci as two-dimensional gel spots. By this method, the status of DNA methylation can efficiently be determined by monitoring the appearance or disappearance of spots by using a methylation-sensitive restriction enzyme. In the present study, using RLGS with NotI, we examined, in comparison with a brain RLGS profile, the status of DNA methylation of more than 900 loci among three types of mouse cell lines: the embryonal carcinoma cell line P19, the stable mesenchymal cell line 10T1/2, and our established neuroepithelial (EM) cell lines. We found that the relative numbers of RLGS spots which appeared were less than 3.3% of those surveyed in all cell lines examined. However, 5 to 14% of spots disappeared, the numbers increasing with an increase in the length of the culture period, and many spots were commonly lost in 10T1/2 and in three EM cell lines. Thus, for these cell lines, many more spots disappeared than appeared. However, the numbers of spots disappearing and appearing were well balanced, and the ratio in P19 cells was almost equal to that in liver cells in vivo. These RLGS experimental observations suggested that permanent cell lines such as 10T1/2 are hypermethylated and that our newly established EM cell lines are also becoming heavily methylated at common loci. On the other hand, methylation and demethylation seem to be balanced in P19 cells in a manner similar to that in in vivo liver tissue. 相似文献
47.
Koichiro Yoshihara Motokatsu Tsuyuki Asako Itaya Yasuharu Tanaka Tomoya Kamiya 《Molecular and cellular biochemistry》1994,135(2):143-151
HL-60 cells transferred from serum-supplemented to serum-free culture medium initially bound to culture plate tightly and then released from the plate on increasing the culture time and resumed exponential growth after about 8 h lag. At the initial stage of the culture, the cells became extremely sensitive to 3-aminobenzamide, a potent inhibitor of poly (ADP-ribose) polymerase, and, at 1 mM, 80 to 90% of the cells were lysed within 20 h, whereas the inhibitor was totally ineffective on the cell growth in serum-supplemented medium at the concentration. Non-inhibitory analogs of the inhibitor were ineffective. Assay of poly(ADP-ribose) polymerase activity in permeable cells indicated that a transient activation of the enzyme occurred during the culture in serum-free medium (the maximum activation was observed at 8 h of the culture). The cells conditioned in serum-free medium for 24 h acquired significant resistancy to the inhibitor. A low concentration of fibronectin (5 to 10/ml) and a relatively high concentration of bovine serum albumin (0.5 to 1 mg/ml) effectively blocked the cell attachment to plate and also the 3-aminobenzamide-induced cell lysis. These results suggest that poly(ADP-ribose) polymerase is involved in a process essential for HL-60 cells to adapt to a serumdeprived growth condition. 相似文献
48.
Mondher Jaziri Kayo Yoshimatsu Jacques Homès Koichiro Shimomura 《Plant Cell, Tissue and Organ Culture》1994,38(2-3):257-262
Hairy root cultures of Atropa belladonna L. were established by infection either with Agrobacterium rhizogenes ATCC 15834 or MAFF 03-01724, and transgenic plants were obtained from both hairy root cultures. Doubly transformed roots were induced by re-infection of the leaf segments of transgenic Atropa belladonna plants (A. rhizogenes 15834) with MAFF 03-01724. Shoots and viviparous leaves were regenerated from the doubly transformed roots. The genetic transformation was determined by the opine assay (agropine, mannopine and/or mikimopine) and polymerase chain reaction. Physiological changes and tropane alkaloid biosynthesis in the hairy roots (singly and doubly transformed) were investigated. The alkaloid content in the doubly transformed root strain was intermediate as compared to the root strains which were singly transformed. On the other hand endogenous IAA levels in doubly transformed roots were significantly decreased compared to both singly transformed roots.Abbreviations BA
benzyladenine
- IAA
indoleacetic acid
- NAA
naphthaleneacetic acid
- PCR
polymerase chain reaction
-
t-ZR
trans-zeatin 相似文献
49.
Haruo Takeshita Toshihiro Yasuda Daita Nadano Reiko Iida Masao Nakanaga Etsuko Tenjo Kazumi Sawazaki Koichiro Kishi 《Human genetics》1994,94(3):224-230
The main isozyme patterns of desialylated blood plasma or serum -l-fucosidase (FUCA) were found to be almost identical to those of semen, urine, placental extracts, and leukocyte lysates, when detected by polyacrylamide gel isoelectric focusing, and activity staining using the fluorogenic substrate 4-methylumbelliferyl--l-fucopyranoside. Three phenotypes (1, 2-1, and 2) determined from plasma samples were identical to the phenotypes from urine and leukocyte lysates from the same individuals. A population study of plasma samples collected from 485 Japanese individuals indicated that the frequencies of the FUCA11
* and FUCA12
* alleles were 0.7505 and 0.2495, respectively. The mean plasma enzyme activities (+SD) of the three phenotypes were 318.8 ± 116.7 nmol/ml per h for type 1, 268.0 ± 108.3 nmol/ml per h for type 2-1, and 233.2 ± 84.4 nmol/ml per h for type 2. The mean activities of types 1 and 2 suggest that, on average, the FUCA11
* gene product in plasma has about 1.4 times the activity of FUCA12
*. 相似文献
50.
ts7, a temperature-sensitive mutant defective in neuraminidase (NA) of influenza B/Kanagawa/73, lacks NA enzymatic activity at the nonpermissive temperature (37.5 C). When MDCK cells were infected with the mutant at the permissive temperature (32 C) and exposed to pH 5.2 medium, extensive cell fusion occurred. In contrast, at the nonpermissive temperature cells did not show cell fusion at all unless they were pretreated with trypsin, suggesting that at 37.5 C the hemagglutinin (HA) of ts7 is expressed at the cell surface in an uncleaved form. It was also found that the replacement of RNA segment 6 of ts7 with that of wild-type B/Lee resulted in the emergence of low pH-induced fusion activity as well as NA enzymatic activity at the incubation temperature of 37.5 C and that the addition of bacterial NA to the cultures infected with ts7 at 37.5 C early in infection brought about low pH-induced cell fusion. We suggest that the removal of neuraminic acid from the carbohydrate moiety of HA by NA is essential for the cleavage of HA by cellular protease. 相似文献