全文获取类型
收费全文 | 3979篇 |
免费 | 205篇 |
国内免费 | 1篇 |
出版年
2023年 | 13篇 |
2022年 | 7篇 |
2021年 | 59篇 |
2020年 | 45篇 |
2019年 | 40篇 |
2018年 | 68篇 |
2017年 | 60篇 |
2016年 | 86篇 |
2015年 | 139篇 |
2014年 | 184篇 |
2013年 | 250篇 |
2012年 | 302篇 |
2011年 | 293篇 |
2010年 | 147篇 |
2009年 | 166篇 |
2008年 | 259篇 |
2007年 | 250篇 |
2006年 | 238篇 |
2005年 | 230篇 |
2004年 | 267篇 |
2003年 | 209篇 |
2002年 | 201篇 |
2001年 | 60篇 |
2000年 | 47篇 |
1999年 | 46篇 |
1998年 | 49篇 |
1997年 | 36篇 |
1996年 | 31篇 |
1995年 | 39篇 |
1994年 | 39篇 |
1993年 | 31篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 18篇 |
1989年 | 25篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 15篇 |
1985年 | 14篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1975年 | 11篇 |
1974年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4185条查询结果,搜索用时 187 毫秒
71.
Dissociability of the monomer ribosomes prepared from dry and imbibed pine (Pinus thunbergii) seed embryos was analyzed in sucrose density gradient containing a high salt buffer. Abnormal dissociation into the subunits
was observed with the ribosome preparation from dry seed embryos when compared with that from imbibed seed embryos, i.e. each
subunit peak was broader and localized at a lower site in sucrose density gradient. This indicates some change(s) in ribosomes
during imbibition of seeds. These ribosomal changes also progressedin vitro. That is, after incubation of ribosome preparation from dry seed embryos in a high salt buffer for 5 min at 30 C or in a
low salt buffer for 15 hr at 0 C, complete dissociation into the normal subunits was observed. No difference was found between
polyacrylamide gel electrophoresis patterns of ribosomal RNA from dry and imbibed seed embryos. These results suggest some
alteration in the protein components of ribosome during imbibition of pine seeds.
This paper is dedicated to Prof. Shyogo Sawamura, Utsunomiya University on his retirement in March, 1979. 相似文献
72.
The mechanism by which dihydroconiferyl alcohol (DCA) stimulatesindole-3-acetic acid (IAA)-induced elongation of cucumber hypocotylsections was studied. Although DCA did not affect the uptakeof IAA-5-3H by hypocotyl sections, the endogenous level of IAA-5-3Hin DCA-treated sections was much higher than in DCA untreatedones. IAA-5-3H in the incubation medium was degraded in thepresence of hypocotyl sections, and this degradation of IAAwas inhibited by DCA. An in vitro experiment with horseradishperoxidase revealed that DCA inhibited the IAA degrading activityof the oxidase, as did caffeic acid and ferulic acid. Theseresults suggested that DCA enhances IAA-induced cucumber hypocotylelongation by acting as an antioxidant of IAA. (Received June 4, 1975; ) 相似文献
73.
74.
A versatile, two-step chromatographic method using DEAE-Toyopearl(Toyo Soda, Japan) is described for purifying photosystem IIreaction center complex from digitonin extracts of spinach thylakoidmembranes. The method is very simple and brings about an approximatefour-fold increase in the specific activity, on a chlorophyllbasis, of 2,4-dichlorophenol-indophenol photoreduction with1,5-diphenylcarbazide (to about 2,000 µ electron equivalentsper mg chlorophyll per h), with an approximate 40 percent recoveryin chlorophyll. The SDS-polyacrylamide gel electrophoresis performedin the presence of 4 M urea in the analyzing gel shows fourpolypeptide bands of the photosystem II reaction center of about47, 43, 30 and 9 kilodaltons. The absorption and fluorescence properties, as well as the pigmentand chemical compositions and the above mentioned polypeptideprofile of the purified complex are essentially identical withthose of the preparations isolated by the previously describedmethod (Satoh 1982). The digitonin solubilization of thylakoid membranes destroysthe water splitting machinery, so that the purified complexshows no oxygen evolving activity, even although 0.60.7atoms of manganese per 50 chlorophyll molecules still remain. (Received March 19, 1985; Accepted July 19, 1985) 相似文献
75.
76.
The steroid-binding properties of recombinant glucocorticoid receptor: a putative role for heat shock protein hsp90 总被引:2,自引:0,他引:2
Y Ohara-Nemoto P E Str?mstedt K Dahlman-Wright T Nemoto J A Gustafsson J Carlstedt-Duke 《The Journal of steroid biochemistry and molecular biology》1990,37(4):481-490
The steroid-binding domain of the human glucocorticoid receptor was expressed in Escherichia coli either as a fusion protein with protein A or under control of the T7 RNA polymerase promoter. The recombinant proteins were found to bind steroids with the normal specificity for a glucocorticoid receptor but with reduced affinity (Kd for triamcinolone acetonide approximately 70 nM). Glycerol gradient analysis of the E. coli lystate containing the recombinant protein indicated no interaction between the glucocorticoid receptor fragment and heat shock proteins. However, synthesis of the corresponding fragments of glucocorticoid receptor in vitro using rabbit reticulocyte lystate resulted in the formation of proteins that bound triamcinolone acetonide with high affinity (Kd 2nM). Glycerol gradient analysis of these proteins, with and without molybdate, indicated that the in vitro synthesised receptor fragments formed complexes with hsp90 as previously shown for the full-length rat glucocorticoid receptor. Radiosequence analysis of the recombinant steroid-binding domain expressed in E. coli and affinity labelled with dexamethasone mesylate identified binding of the steroid to Cys-638 predominantly. However, all cysteine residues within the steroid-binding domain were affinity labelled to a certain degree indicating that the recombinant protein has a structure similar to the native receptor but more open and accessible. 相似文献
77.
Chikayuki Morimoto Shinichiro Asakawa Emiko Kuribayashi-Okuma Yoshikazu Nemoto Jinping Li 《Nucleosides, nucleotides & nucleic acids》2020,39(5):744-759
AbstractTo elucidate roles of the intestine in uric acid (UA) metabolism, we examined ABCG2 expression, tissue UA content and xanthine oxidoreductase (XOR) activity in different intestinal segments. Male SD rats were assigned to control group or oxonic acid-induced hyperuricemia (HUA) group. In control rats, ABCG2 was present both in villi and crypts in each segment. Tissue UA content and XOR activity were relatively high in duodenum and jejunum. However, in HUA rats, tissue UA content was significantly elevated in the ileum, whereas it remained unaltered in other segments. Moreover, ABCG2 expression in the HUA group was upregulated both in the villi and crypts of the ileum. These data indicate that the ileum may play an important role in the extra-renal UA excretion. 相似文献
78.
Satsuki Tsuji Naoki Shibata Hayato Sawada Masayuki Ushio 《Molecular ecology resources》2020,20(5):1323-1332
Recent advances in environmental DNA (eDNA) analysis using high‐throughput sequencing (HTS) enable evaluation of intraspecific genetic diversity in a population. As the intraspecific genetic diversity provides invaluable information for wildlife conservation and management, there is an increasing demand to apply eDNA analysis to population genetics and the phylogeography by quantitative evaluation of intraspecific diversity. However, quantitative evaluations of intraspecific genetic diversity using eDNA is not straightforward because the number of eDNA sequence reads obtained by HTS may not be an index of the quantity of eDNA. In this study, to quantitatively evaluate genetic diversity using eDNA analysis, we applied a quantitative eDNA metabarcoding method using the internal standard DNAs. We targeted Ayu (Plecoglossus altivelis altivelis) and added internal standard DNAs with known copy numbers to each eDNA sample obtained from three rivers during the library preparation process. The sequence reads of each Ayu haplotype were successfully converted to DNA copy numbers based on the relationship between the copy numbers and sequence reads of the internal standard DNAs. In all rivers, the calculated copy number of each haplotype showed a significant positive correlation with the haplotype frequency estimated by a capture‐based survey. Furthermore, estimates of genetic indicators such as nucleotide diversity based on the eDNA copy numbers were comparable with those estimated based on a capture‐based study. Our results demonstrate that eDNA analysis with internal standard DNAs enables reasonable quantification of intraspecific genetic diversity, and this method could thus be a promising tool in the field of population genetics and phylogeography. 相似文献
79.
80.
Molecular and Cellular Biochemistry - The aims of this study were to investigate the impact of caloric restriction (CR) on cardiac senescence in an animal model of diabetes and examine the signal... 相似文献