全文获取类型
收费全文 | 48955篇 |
免费 | 3744篇 |
国内免费 | 4868篇 |
出版年
2023年 | 789篇 |
2022年 | 927篇 |
2021年 | 1236篇 |
2020年 | 1273篇 |
2019年 | 1969篇 |
2018年 | 1729篇 |
2017年 | 1414篇 |
2016年 | 1298篇 |
2015年 | 1263篇 |
2014年 | 2423篇 |
2013年 | 3077篇 |
2012年 | 1894篇 |
2011年 | 2283篇 |
2010年 | 1741篇 |
2009年 | 2263篇 |
2008年 | 2349篇 |
2007年 | 2594篇 |
2006年 | 2303篇 |
2005年 | 1885篇 |
2004年 | 1603篇 |
2003年 | 1584篇 |
2002年 | 1434篇 |
2001年 | 1229篇 |
2000年 | 1008篇 |
1999年 | 847篇 |
1998年 | 795篇 |
1997年 | 762篇 |
1996年 | 732篇 |
1995年 | 748篇 |
1994年 | 762篇 |
1993年 | 665篇 |
1992年 | 653篇 |
1991年 | 646篇 |
1990年 | 482篇 |
1989年 | 511篇 |
1988年 | 462篇 |
1987年 | 442篇 |
1986年 | 419篇 |
1985年 | 672篇 |
1984年 | 897篇 |
1983年 | 721篇 |
1982年 | 761篇 |
1981年 | 599篇 |
1980年 | 615篇 |
1979年 | 549篇 |
1978年 | 438篇 |
1977年 | 404篇 |
1976年 | 375篇 |
1974年 | 246篇 |
1973年 | 258篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
81.
《Cell》2021,184(25):6138-6156.e28
82.
Robert Blake II Elizabeth A. Shute James Waskovsky Arthur P. Harrison JR. 《Geomicrobiology journal》2013,30(3-4):173-192
Abstract Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state. Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions 相似文献
83.
Satoko Iwahori Daisuke Kohmon Junya Kobayashi Yuhei Tani Takashi Yugawa Kenshi Komatsu 《Cell cycle (Georgetown, Tex.)》2014,13(3):471-481
Ataxia-telangiectasia mutated (ATM) plays crucial roles in DNA damage responses, especially with regard to DNA double-strand breaks (DSBs). However, it appears that ATM can be activated not only by DSB, but also by some changes in chromatin architecture, suggesting potential ATM function in cell cycle control. Here, we found that ATM is involved in timely degradation of Cdt1, a critical replication licensing factor, during the unperturbed S phase. At least in certain cell types, degradation of p27Kip1 was also impaired by ATM inhibition. The novel ATM function for Cdt1 regulation was dependent on its kinase activity and NBS1. Indeed, we found that ATM is moderately phosphorylated at Ser1981 during the S phase. ATM silencing induced partial reduction in levels of Skp2, a component of SCFSkp2 ubiquitin ligase that controls Cdt1 degradation. Furthermore, Skp2 silencing resulted in Cdt1 stabilization like ATM inhibition. In addition, as reported previously, ATM silencing partially prevented Akt phosphorylation at Ser473, indicative of its activation, and Akt inhibition led to modest stabilization of Cdt1. Therefore, the ATM-Akt-SCFSkp2 pathway may partly contribute to the novel ATM function. Finally, ATM inhibition rendered cells hypersensitive to induction of re-replication, indicating importance for maintenance of genome stability. 相似文献
84.
Maturity Onset Diabetes of the Young (MODY) is a heterogeneous group of genetic diseases characterized by a primary defect in insulin secretion and hyperglycemia, non-ketotic disease, monogenic autosomal dominant mode of inheritance, age at onset less than 25 years, and lack of auto-antibodies. It accounts for 2–5% of all cases of non-type 1 diabetes. MODY subtype 2 is caused by mutations in the glucokinase (GCK) gene. In this study, we sequenced the GCK gene of two volunteers with clinical diagnosis for MODY2 and we were able to identify four mutations including one for a premature stop codon (c.76C>T). Based on these results, we have developed a specific PCR-RFLP assay to detect this mutation and tested 122 related volunteers from the same family. This mutation in the GCK gene was detected in 21 additional subjects who also had the clinical features of this genetic disease. In conclusion, we identified new GCK gene mutations in a Brazilian family of Italian descendance, with one due to a premature stop codon located in the second exon of the gene. We also developed a specific assay that is fast, cheap and reliable to detect this mutation. Finally, we built a molecular ancestry model based on our results for the migration of individuals carrying this genetic mutation from Northern Italy to Brazil. 相似文献
85.
86.
87.
Bugreev D. V. Sinitsyna O. I. Buneva V. N. Nevinsky G. A. 《Russian Journal of Bioorganic Chemistry》2003,29(3):249-261
Data on the interaction of DNA type I topoisomerases from the murine and human placenta cells with specific and nonspecific oligonucleotides of various structures and lengths are summarized. The relative contributions of various contacts between the enzymes and DNA that have previously been detected by X-ray analysis to the total affinity of the topoisomerases for DNA substrates are estimated. Factors that determine the differences in the enzyme interactions with specific and nonspecific single- and double-stranded DNAs are revealed. The results of the X-ray analysis of human DNA topoisomerase I are interpreted taking into account data on the comprehensive thermodynamic and kinetic analysis of the enzyme interaction with the specific and nonspecific DNAs. 相似文献
88.
89.
90.
We studied the impulse activity of neurons of the basal and lateral amygdalar nuclei generated when experimental animals (rats) performed fast stereotyped food-procuring movements by the forelimb. Within the basolateral amygdala, there are neurons whose activity is related to different stages of getting off the food, and according to the characteristics of their spiking these neurons should be divided into a number of subpopulations. Activation forestalling the movement initiation by 0.5-1.0 sec was observed in most neurons of the basolateral amygdala; this is considered a manifestation of excitation related to a motivation component of the food-procuring behavior. Activation of amygdalar neurons following movement initiation can result from generation in this structure of additional excitation necessary for successful performance of a complete food-procuring motor cycle. 相似文献