全文获取类型
收费全文 | 1457篇 |
免费 | 109篇 |
出版年
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 30篇 |
2015年 | 43篇 |
2014年 | 40篇 |
2013年 | 78篇 |
2012年 | 72篇 |
2011年 | 65篇 |
2010年 | 53篇 |
2009年 | 57篇 |
2008年 | 69篇 |
2007年 | 86篇 |
2006年 | 68篇 |
2005年 | 62篇 |
2004年 | 69篇 |
2003年 | 60篇 |
2002年 | 52篇 |
2001年 | 31篇 |
2000年 | 48篇 |
1999年 | 42篇 |
1998年 | 14篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 26篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 25篇 |
1988年 | 20篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1979年 | 22篇 |
1978年 | 9篇 |
1977年 | 13篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1973年 | 11篇 |
1971年 | 6篇 |
1970年 | 13篇 |
1968年 | 6篇 |
排序方式: 共有1566条查询结果,搜索用时 15 毫秒
1.
Hoshino Atsushi; Abe Yukihide; Saito Norio; Inagaki Yoshishige; Iida Shigeru 《Plant & cell physiology》1997,38(8):970-974
The Japanese morning glory carrying the recessive mutable speckledallele with the dominant speckled-activator bears colorlessflowers with fine and round colored spots distributed over thecorolla whereas the plant without the speckled-activator producespale yellow flowers. Previous chemical analysis has indicatedthat a mutation in the gene for flavanone 3-hydroxylase (F3H)is a likely candidate for the speckled allele. However, theF3HmRNA without sequence alteration accumulates normally inthe pale yellow flowers, indicating that the speckled alleleis neither the F3H gene nor a regulatory gene acting on theF3H gene expression. (Received April 4, 1997; Accepted June 2, 1997) 相似文献
2.
3.
Pancreatic islets of Langerhans consist of endocrine cells, primarily α, β and δ cells, which secrete glucagon, insulin, and somatostatin, respectively, to regulate plasma glucose. β cells form irregular locally connected clusters within islets that act in concert to secrete insulin upon glucose stimulation. Due to the central functional significance of this local connectivity in the placement of β cells in an islet, it is important to characterize it quantitatively. However, quantification of the seemingly stochastic cytoarchitecture of β cells in an islet requires mathematical methods that can capture topological connectivity in the entire β-cell population in an islet. Graph theory provides such a framework. Using large-scale imaging data for thousands of islets containing hundreds of thousands of cells in human organ donor pancreata, we show that quantitative graph characteristics differ between control and type 2 diabetic islets. Further insight into the processes that shape and maintain this architecture is obtained by formulating a stochastic theory of β-cell rearrangement in whole islets, just as the normal equilibrium distribution of the Ornstein-Uhlenbeck process can be viewed as the result of the interplay between a random walk and a linear restoring force. Requiring that rearrangements maintain the observed quantitative topological graph characteristics strongly constrained possible processes. Our results suggest that β-cell rearrangement is dependent on its connectivity in order to maintain an optimal cluster size in both normal and T2D islets. 相似文献
4.
5.
Three O-methyltransferases which catalyze S-adenosyl-L-methionine (SAM)-dependent O-methylation of licodione (LMT), flavone/flavonol (FMT), and caffeic acid (CMT) were separated from the callus culture of Glycyrrhiza echinata, and characteristic differences between their pH optima and Mg2+ requirement for activity were demonstrated. The activity of LMT, which is involved in retrochalcone (echinatin) biosynthesis, but not of FMT or CMT, was found to be stimulated when suspension-cultured G. echinata cells were treated with yeast extract (YE), which causes rapid production of echinatin in the cells. Cycloheximide suppressed both the YE-induced echinatin formation and LMT enhancement. The results indicate a selective induction of retrochalcone pathway in Glycyrrhiza cells in response to stress.Abbreviations SAM
S-adenosyl-L-methionine
- LMT, SAM
licodione 2-O-methyltransferase
- FMT, SAM
flavone/flavonol O-methyltransferase
- CMT, SAM
caffeate 3-O-methyltransferase
- OMT
O-methyltransferase
- CH
cycloheximide
- YE
yeast extract
This paper is Part 47 in the series Studies on Plant Tissue Cultures. For Part 46, see Ayabe S, Iida K, Furuya T (1986) Phytochemistry: in press 相似文献
6.
K Sobue K Kanda I Miyamoto K Iida I Yahara R Hirai A Hiragun 《Experimental cell research》1989,181(1):256-262
With fluorescence and interference reflection microscopy (IRM), we compared the regional distribution of calspectin, its interacting proteins (nonerythroid protein 4.1 and calpactin), alpha-actinin, and vinculin in NRK cells and their avian sarcoma virus (ASV)- or temperature-sensitive (ts) Rous sarcoma virus (RSV)-transformed cells. The localization of these cytoskeletal proteins was determined with the specific antibodies. In NRK cells, alpha-actinin and vinculin were concentrated at adhesion plaques. By contrast, calspectin was distributed throughout the cytoplasm, but not concentrated at adhesion plaques. In ASV- and ts RSV-transformed cells, all three cytoskeletal proteins were concentrated at dot structures representing cellular feet. Nonerythroid protein 4.1 and calpactin were diffusely distributed throughout the cytoplasm of NRK cells and their transformed counterparts. In the case of calpactin, a part of this protein was excluded near regions of the terminal ends of stress fibers. These two proteins did not show the restricted location at the dot structures of transformed cells. From these findings, it is apparent that the accumulation of calspectin into dot structures is a specific event for cell transformation induced by the src protein. 相似文献
7.
A Imai K Iida T Tamaya 《Comparative biochemistry and physiology. B, Comparative biochemistry》1990,97(3):617-621
1. Stimulated inositolphospholipid turnover has been proposed as a signal-transducing mechanism in many cell types. It appears to be initiated by stimulation of hydrolysis of inositolphospholipid by a phospholipase C. 2. In human endometrial fibroblasts, estradiol was observed to cause sequential enhancement of [32P]phosphate incorporation into phosphatidic acid (PA) and phosphatidylinositol (PI), indicating an accelerating effect of estradiol on inositolphospholipid turnover. Specific 32P-radioactivity in the gamma-phosphate of ATP was increased in response to estradiol. Estrone or estriol were without any effects. 3. To investigate possible mechanisms by which estradiol activates a phospholipase C enzyme in the fibroblasts, the plasma membrane fraction isolated from the fibroblasts was exposed to estradiol in the presence of guanosine triphosphate (GTP) to detect inositol trisphosphate (IP3) production. The IP3 production was Ca2+ dependent, a dependency not affected by estradiol. 4. However, ATP decreased the Ca2+ concentration required for IP3 production in a dose-dependent manner; adenosine diphosphate (ADP), cytidine triphosphate (CTP) showed no effects. 5. These findings from cell and cell-free systems might suggest that estradiol stimulates a phospholipase C, as a result of enhancement of intracellular ATP synthesis, but not as a result of a direct effect on the enzyme molecule or direct activation of receptor-phospholipase C unit. 6. This may give us new insight into estrogen-stimulated cellular phenomenon through some mechanisms other than that classically associated with the action of estrogen. 相似文献
8.
9.
The KKRKK sequence is involved in heat shock-induced nuclear translocation of the 18-kDa actin-binding protein, cofilin. 总被引:9,自引:0,他引:9
The exposure of cultured mammalian cells to elevated temperatures induces the translocation of actin and cofilin into the nuclei and the formation of intranuclear bundles of actin filaments decorated by cofilin (actin/cofilin rods). Cofilin has a stretch of five basic amino acids, KKRKK, which was assumed to be the sequence involved in the heat shock-dependent accumulation of cofilin in nuclei. To examine this possibility, the site-directed mutagenesis technique was employed to alter the KKRKK sequence of cofilin to KTLKK and the mutated cofilin was expressed under the human beta-actin promoter in transfectants of mouse C3H-2K cell line. All the recombinants derived from porcine cofilin cDNA were constructed so as to possess an extra-nonapeptide at their N-termini when expressed; their intracellular distribution could, therefore, be discriminated from that of endogenous cofilin using the indirect immunofluorescence method with polyclonal antibodies directed against the extra-peptide. The results clearly showed that the mutated cofilin possessing KTLKK instead of KKRKK did not translocate into the nuclei in response to heat shock whereas a recombinant cofilin with the unaltered sequence of KKRKK responded to heat shock and formed intranuclear rods together with actin. Although in vitro actin binding experiments showed that KTLKK-cofilin has a weaker affinity to actin filaments than KKRKK-cofilin, KTLKK-cofilin was found to form cytoplasmic actin/cofilin rods when transformants were incubated in NaCl buffer. Furthermore, we have noted that endogenous cofilin present in cells expressing KTLKK-cofilin behaved normally, translocated into nuclei and formed intranuclear actin/cofilin rods upon heat shock. These results suggest that the KKRKK sequence of cofilin functions as a nuclear location signal upon heat shock. 相似文献
10.
Sequence rearrangement in JC virus DNAs molecularly cloned from immunosuppressed renal transplant patients. 总被引:7,自引:2,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)
Y Yogo T Kitamura C Sugimoto K Hara T Iida F Taguchi A Tajima K Kawabe Y Aso 《Journal of virology》1991,65(5):2422-2428
From nonimmunocompromised individuals, we have recently identified a possible archetypal JC virus DNA sequence from which various regulatory sequences of JC virus isolates derived from patients with progressive multifocal leukoencephalopathy (PML) could have evolved. In this study, we analyzed the regulatory sequences of JCV DNAs cloned from urine samples of a PML risk group (renal transplant patients on immunosuppressive therapy). A number of JC virus DNAs were molecularly cloned from virions excreted in the urine of eight patients. Furthermore, fragments containing the regulatory region were amplified by the polymerase chain reaction and subsequently molecularly cloned from cell-associated JC virus excreted in the urine of two patients. The regulatory regions in all clones were analyzed with restriction enzymes, and those in representative clones were sequenced. We found that clones with the archetypal regulatory sequence were predominant in all urine samples, but a few clones carried regulatory sequences that diverged from the archetypal sequence by deletion or duplication. The finding that sequence rearrangement in the archetypal regulatory region occurs in the course of infection in immunosuppressed hosts is consistent with the adaptation hypothesis which has been put forward to explain the divergence of the regulatory regions in PML-derived JC virus isolates. 相似文献