全文获取类型
收费全文 | 2196篇 |
免费 | 135篇 |
国内免费 | 123篇 |
出版年
2024年 | 7篇 |
2023年 | 56篇 |
2022年 | 60篇 |
2021年 | 114篇 |
2020年 | 106篇 |
2019年 | 93篇 |
2018年 | 98篇 |
2017年 | 54篇 |
2016年 | 50篇 |
2015年 | 121篇 |
2014年 | 146篇 |
2013年 | 167篇 |
2012年 | 72篇 |
2011年 | 97篇 |
2010年 | 52篇 |
2009年 | 88篇 |
2008年 | 93篇 |
2007年 | 121篇 |
2006年 | 80篇 |
2005年 | 82篇 |
2004年 | 67篇 |
2003年 | 63篇 |
2002年 | 73篇 |
2001年 | 35篇 |
2000年 | 37篇 |
1999年 | 31篇 |
1998年 | 34篇 |
1997年 | 25篇 |
1996年 | 27篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 21篇 |
1991年 | 20篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 13篇 |
1985年 | 36篇 |
1984年 | 31篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1975年 | 4篇 |
1974年 | 5篇 |
排序方式: 共有2454条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
《Cell reports》2020,30(6):1835-1847.e9
5.
Hubert L. Dulieu 《Mutation research》1974,25(3):289-304
A greenish-yellow mutant was obtained after treatment of seeds of Nicotiana tabacum L. var. Xanthi n.c. with ethyl methanesulfonate (EMS). Two genetically independent mutations (a1 and a2) were isolated. The first mutation (a1) antagonizes the function of its partially dominant a1+ allele. The second mutation (a2) is amorphous but strongly interacts with a1.Among the nine possible genotypes at the two loci, five varied in somatic cells. The heterozygous state a1+/a1 strongly increased the frequency of both spontaneous and induced variations. However, two homozygotes also showed variations.Variants were isolated from induced and spontaneous non-reciprocal and reciprocal variations within paliside tissues by bud induction in vitro. They were genetically tested. In this first paper, only non-reciprocal variations are reported.Green variants from the greenish-yellow (J1) dihybrid a1+/a1a2+/a2 clone had two genotypes: the first was due to true reversions of a1 to a1+, whereas the second was due to amorphous a10 mutations from a1. These a10 mutations may well be deletions.The lightest yellow variants from J1 were due to mutations either from a1+ into a1 or from a2+ into a2.Deletions at the a1+?a1 locus led to either yellow variations when a1+ was lost, or to false reversions when the antagonistic allele a1 was lost.Amorphous alleles at the a1+?a1 locus were also isolated from tissues other than J+. They gave zygotic lethality (s) that probably varied with the size of the deletions. Thus, true reversions and deletions at the a1+?a1 locus could be distinguished from one another by progeny tests.Other variants showed higher frequencies of spontaneous variations (instability). Somatic changes observed in these unstable systems were due to modifications at the marker loci. The genetic nature of this instability is not yet known.There is strong evidence that the genetic events involved in these non-reciprocal variations were deletions, conversions and point mutations. True reversions from a1 into a1+ and new mutations from a1+ into a1 were obtained only from a1+/a1. It was therefore supposed that the changes observed took place only in heterozygotes, and the conversion hypothesis was made. Attempts are being made to prove that conversions do exist in higher plants, and to find out if this process, as deletions, is induced by radiation. 相似文献
6.
7.
8.
I. N. Suwastika T. Toop H. R. Irving C. A. Gehring 《Plant biology (Stuttgart, Germany)》2000,2(1):1-3
Abstract: An increasing body of evidence suggests that in plants, as in vertebrates, biologically active natriuretic peptide (NP) hormones play an important role in the regulation of the osmotic and ionic balance. The evidence includes isolation and immunoaffinity purification of biologically active natriuretic peptide analogues (irPNP) from ivy that promoted stomatal opening and specifically, rapidly and transiently increased cGMP levels in root conductive tissue. In this study we demonstrate that I125 -rat atrial natriuretic peptide (rANP) binds to plasma membranes from leaf and stem tissue of Tradescantia multiflora and importantly, both unlabelled rANP and irPNP can competitively displace that binding. In addition, tissue section autoradiography reveals specific in situ binding of I125 -rANP to leaf and stem tissue. The findings are consistent with the presence of a biologically active NP system in plants and suggest that NPs signal through a dedicated receptor system. 相似文献
9.
10.
Gas chromatography-mass spectrometric analyses of purified extracts from cultures of Rhizobium phaseoli wild-type strain 8002, grown in a non-tryptophan-supplemented liquid medium, demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol (IEt), indole-3-aldehyde and indole-3-methanol (IM). In metabolism studies with 3H-, 14C- and 2H-labelled substrates the bacterium was shown to convert tryptophan to IEt, IAA and IM; IEt to IAA and IM; and IAA to IM. Indole-3-acetamide (IAAm) could not be detected as either an endogenous constituent or a metabolite of [3H]tryptophan nor did cultures convert [14C]IAAm to IAA. Biosynthesis of IAA in R. phaseoli, thus, involves a different pathway from that operating in Pseudomonas savastanio and Agrobacterium tumefaciens-induced crown-gall tumours.Abbreviations IAA
indole-3-acetic acid
- IAld
indole-3-aldehyde
- IAAm
indole-3-acetamide
- IEt
indole-3-ethanol
- IM
indole-3-methanol
- HPLC-RC
high-performance liquid chromatography-radio counting
- GC-MS
gas chromatography-mass spectrometry 相似文献