全文获取类型
收费全文 | 26319篇 |
免费 | 1908篇 |
国内免费 | 1174篇 |
出版年
2024年 | 42篇 |
2023年 | 427篇 |
2022年 | 636篇 |
2021年 | 991篇 |
2020年 | 1052篇 |
2019年 | 1519篇 |
2018年 | 1041篇 |
2017年 | 701篇 |
2016年 | 730篇 |
2015年 | 914篇 |
2014年 | 1749篇 |
2013年 | 2010篇 |
2012年 | 1410篇 |
2011年 | 1707篇 |
2010年 | 1324篇 |
2009年 | 1164篇 |
2008年 | 1322篇 |
2007年 | 1272篇 |
2006年 | 1069篇 |
2005年 | 1045篇 |
2004年 | 949篇 |
2003年 | 768篇 |
2002年 | 722篇 |
2001年 | 425篇 |
2000年 | 417篇 |
1999年 | 402篇 |
1998年 | 328篇 |
1997年 | 270篇 |
1996年 | 269篇 |
1995年 | 262篇 |
1994年 | 252篇 |
1993年 | 176篇 |
1992年 | 195篇 |
1991年 | 144篇 |
1990年 | 139篇 |
1989年 | 123篇 |
1988年 | 99篇 |
1987年 | 86篇 |
1986年 | 81篇 |
1985年 | 120篇 |
1984年 | 157篇 |
1983年 | 123篇 |
1982年 | 143篇 |
1981年 | 89篇 |
1980年 | 110篇 |
1979年 | 100篇 |
1978年 | 66篇 |
1977年 | 66篇 |
1976年 | 54篇 |
1974年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Suzanne Camus Sergio Menéndez Kenneth Fernandes Nelly Kua Geng Liu Dimitris P. Xirodimas David P. Lane Jean-Christophe Bourdon 《Cell cycle (Georgetown, Tex.)》2012,11(8):1646-1655
The discovery that the single p53 gene encodes several different p53 protein isoforms has initiated a flurry of research into the function and regulation of these novel p53 proteins. Full-length p53 protein level is primarily regulated by the E3-ligase Mdm2, which promotes p53 ubiquitination and degradation. Here, we report that all of the novel p53 isoforms are ubiquitinated and degraded to varying degrees in an Mdm2-dependent and -independent manner, and that high-risk human papillomavirus can degrade some but not all of the novel isoforms, demonstrating that full-length p53 and the p53 isoforms are differentially regulated. In addition, we provide the first evidence that Mdm2 promotes the NEDDylation of p53β. Altogether, our data indicates that Mdm2 can distinguish between the p53 isoforms and modify them differently. 相似文献
2.
Jeremy D. Hogan Katharine M. Jack Fernando A. Campos Urs Kalbitzer Linda M. Fedigan 《American journal of primatology》2019,81(7)
Primates have long been used as indicator species for assessing overall ecosystem health. However, area‐wide census methods are time consuming, costly, and not always feasible under many field conditions. Therefore, it is important to establish whether monitoring a subset of a population accurately reflects demographic changes occurring in the population at large. Over the past 35 years, we have conducted 15 area‐wide censuses in Sector Santa Rosa, Costa Rica. These efforts have revealed important trends in population growth patterns of capuchin monkeys following the protection and subsequent regeneration of native forests. During this same period, we have also intensively studied a subset of the capuchin groups. Comparing these two datasets, we investigate whether the population structures of the closely monitored groups are reliable indicators of area‐wide demographic patterns. We compare the overall group size and the individual age/sex class compositions of study groups and nonstudy groups (i.e., those contacted during area‐wide censuses only). Our study groups contained more individuals overall with a larger proportion of infants, and there were indications that the proportion of adult and subadult males was lower. These differences can be ascribed either to sampling errors or real differences attributable to human presence and/or better habitat quality for the study groups. No other sex/age classes differed, and major demographic changes were simultaneously evident in both study and nonstudy groups. This study suggests that the Santa Rosa capuchin population is similarly impacted by large‐scale ecological patterns observable within our study groups. 相似文献
3.
《Cell reports》2020,30(4):1152-1163.e4
- Download : Download high-res image (170KB)
- Download : Download full-size image
4.
《Cell reports》2020,30(3):725-738.e4
- Download : Download high-res image (167KB)
- Download : Download full-size image
5.
R Liang 《Biochemical and biophysical research communications》1984,120(3):741-746
Primary cell cultures were prepared from breast muscles of 11 day 4 hour-embryonic chicks. Cytoplasmic RNAs were isolated from the cultured cells at various time intervals from day 3 to day 8. A [P32] DNA probe complementary to messenger RNA of myosin heavy chain was used to hybridize with the RNAs after gel electrophoresis. A transient species of polyadenylated RNA with a decreased mobility in electrophoresis was detected during a period of time when contractions of syncytial fibers were first observed. 相似文献
6.
7.
D E Bowman 《Biochemical and biophysical research communications》1979,87(1):78-84
The oxidized B chain of insulin was used as a simple model for further consideration of limited proteolysis with low substrate:enzyme ratios. With low B chain:trypsin ratios, the ordinarily slower cleavage rate of the -Lys29-Ala30 bond essentially equaled the cleavage saturation rate of the -Arg22-Gly23 bond. This led to the disappearance of octapeptide which ordinarily forms most rapidly. Heptapeptide and alanine, formed mainly by cleavage of the octapeptide, decreased somewhat at high enzyme relative levels. Trypsin added to B chain formed a single chromatographic peak. 相似文献
8.
Yunfan Sun Liang Wu Yu Zhong Kaiqian Zhou Yong Hou Zifei Wang Zefan Zhang Jiarui Xie Chunqing Wang Dandan Chen Yaling Huang Xiaochan Wei Yinghong Shi Zhikun Zhao Yuehua Li Ziwei Guo Qichao Yu Liqin Xu Jia Fan 《Cell》2021,184(2):404-421.e16
- Download : Download high-res image (233KB)
- Download : Download full-size image
9.
10.
Variability and genetics of spacer DNA sequences between the ribosomal-RNA genes of hexaploid wheat (Triticum aestivum) 总被引:1,自引:0,他引:1
C. E. May R. Appels 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1987,74(5):617-624
Summary Using restriction enzyme digests of genomic DNA extracted from the leaves of 25 hexaploid wheat (Triticum aestivum L. em. Thell.) cultivars and their hybrids, restriction fragment length polymorphisms of the spacer DNA which separates the ribosomal-RNA genes have been examined. (From one to three thousand of these genes are borne on chromosomes 1B and 6B of hexaploid wheat). The data show that there are three distinct alleles of the 1B locus, designated Nor-B1a, Nor-B1b, and Nor-B1c, and at least five allelic variants of the 6B locus, designated Nor-B2a, Nor-B2b, Nor-B2c, Nor-B2d, and Nor-B2e. A further, previously reported allele on 6B has been named Nor-B2f. Chromosome 5D has only one allelic variant, Nor-D3. Whereas the major spacer variants of the 1B alleles apparently differ by the loss or gain of one or two of the 133 bp sub-repeat units within the spacer DNA, the 6B allelic variants show major differences in their compositions and lengths. This may be related to the greater number of rDNA repeat units at this locus. The practical implications of these differences and their application to wheat breeding are discussed. 相似文献