全文获取类型
收费全文 | 19730篇 |
免费 | 2017篇 |
国内免费 | 11篇 |
出版年
2022年 | 153篇 |
2021年 | 292篇 |
2020年 | 171篇 |
2019年 | 200篇 |
2018年 | 280篇 |
2017年 | 257篇 |
2016年 | 435篇 |
2015年 | 783篇 |
2014年 | 818篇 |
2013年 | 1075篇 |
2012年 | 1277篇 |
2011年 | 1273篇 |
2010年 | 866篇 |
2009年 | 768篇 |
2008年 | 1098篇 |
2007年 | 1095篇 |
2006年 | 1030篇 |
2005年 | 1056篇 |
2004年 | 1018篇 |
2003年 | 998篇 |
2002年 | 995篇 |
2001年 | 232篇 |
2000年 | 175篇 |
1999年 | 251篇 |
1998年 | 301篇 |
1997年 | 230篇 |
1996年 | 204篇 |
1995年 | 189篇 |
1994年 | 194篇 |
1993年 | 195篇 |
1992年 | 162篇 |
1991年 | 167篇 |
1990年 | 172篇 |
1989年 | 163篇 |
1988年 | 160篇 |
1987年 | 159篇 |
1986年 | 150篇 |
1985年 | 159篇 |
1984年 | 160篇 |
1983年 | 164篇 |
1982年 | 198篇 |
1981年 | 175篇 |
1980年 | 146篇 |
1979年 | 101篇 |
1978年 | 119篇 |
1977年 | 113篇 |
1976年 | 97篇 |
1975年 | 77篇 |
1974年 | 93篇 |
1973年 | 80篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Mario Penna Robert R. Capranica Jane Somers 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(1):73-82
Summary Twenty four castrated male, 6 intact male, and 11 intact female Hyla cinerea were injected subcutaneously with 25 g arginine-vasotocin (AVT) and induced to call 1 h later in response to the playback of a conspecific mating call. Eighteen castrated males and 8 intact females were implanted 5 mg androgen pellets for 3 weeks prior to the neuropeptide injection. Among castrated males, 6/9 testosterone (T) implanted, 4/9 dihydrotestosterone (DHT) implanted and 2/6 non implanted individuals produced calls after being administered AVT. 5/6 intact non implanted males and 6/8 T intact implanted females also called, and 3 intact non implanted females remained silent after the injection. Evoked calls had a mid-frequency spectral peak at about 1900 Hz which is absent in field-recorded mating calls of this species. Calls of implanted females and castrated non implanted males were shorter than those of castrated implanted and intact non implanted males. Audiograms measured before hormone implants showed dips of enhanced sensitivity at about 0.5, 0.9 and 3.0 kHz in males and females. After AVT injection, thresholds at frequencies within the 0.7–1.5 kHz range were increased in castrated males. Such reduction in sensitivity points to an inhibition of the auditory system during hormone induced vocal activation.Abbreviations
AVT
arginine-vasotocin
-
DHT
dihydrotestosterone
-
T
testosterone
-
TS
torus semicircularis 相似文献
122.
Mapping of genes on the linear chromosome of the bacterium Borrelia burgdorferi: Possible locations for its origin of replication 总被引:13,自引:0,他引:13
Iain G. Old Jane MacDougall Isabelle Saint Girons Barrie E. Davidson 《FEMS microbiology letters》1992,99(2-3):245-250
Molecular clones of Borrelia burgdorferi, aetiologic agent of Lyme borreliosis, were isolated and analysed by DNA sequence determination. This procedure yielded B. burgdorferi homologues of gidA, gyrB, gyrA, ftsA and ftsZ. The genes were located on the physical map of the B. burgdorferi linear chromosome. Also mapped were the genes fla and p60 while dnaA was mapped using a heterologous probe. gyrA and gyrB were found to be in tandem and were mapped, along with dnaA at the centre of the chromosome. gidA was located close to the left hand extremity of the chromosome. Because gyrB, dnaA and gidA are normally located within 50 kb of the origin of replication (oriC), we propose two possible sites for oriC in the B. burgdorferi linear chromosome. 相似文献
123.
Insertional inactivation of a gene which controls expression of vancomycin resistance on plasmid pHKK100 总被引:8,自引:0,他引:8
Sandra Handwerger Linda Discotto Jane Thanassi Michael J. Pucci 《FEMS microbiology letters》1992,92(1):11-14
Expression of inducible high level vancomycin resistance (Vmr) in enterococci appears to require other plasmid-encoded genes in addition to the previously described structural genes vanA and vanH. Tn917 mutagenesis was used to identify such a region in the Vmr plasmid pHKK100. Insertional inactivation of a 693-bp open reading frame upstream from vanH resulted in complete loss of Vmr. This putative 26,642-Da protein has been designated VanR. 相似文献
124.
Summary Somatic hybrid plants were recovered following fusion of leaf mesophyll protoplasts isolated from tomato (Lycopersicon esculentum) cultivar UC82 with protoplasts isolated from suspension cultured cells of L. chilense, LA 1959. Iodoacetate was used to select against the growth of unfused tomato protoplasts. Two somatic hybrids were recovered in a population of 16 regenerants. No tomato regenerants were recovered; all of the non-hybrid regenerants were L. chilense. The L. chilense protoplast regenerants were tetraploid. The hybrid nature of the plants was verified using species-specific restriction fragment length polymorphisms for the nuclear, chloroplast and mitochondrial genomes. The somatic hybrids had inherited the chloroplast DNA of the tomato parent, and portions of the mitochondrial DNA of the L. chilense parent. The somatic hybrids formed flowers and developed seedless fruit. 相似文献
125.
126.
127.
128.
Proteins that share conserved "zinc finger" motifs represent a class of DNA-binding proteins that have been shown to play a fundamental role in regulating gene expression and to be involved in a number of human hereditary and malignant disease states. We have isolated, characterized, and mapped zinc finger-encoding genes specific to human chromosome 11q to investigate their possible association in the molecular pathogenesis of several disease loci mapped to this chromosome. An arrayed chromosome 11q cosmid library was screened using a degenerate oligonucleotide corresponding to the H/C link consensus sequence of the Drosophila Kruppel zinc finger gene, resulting in the isolation of six putative zinc finger genes. Three of the genes (ZNF123, ZNF125, and ZNF126) were analyzed and shown to contain tandemly repeated zinc finger motifs of the C2-H2 class. All three novel genes were found to be expressed in normal adult human tissues, although the tissue-specific pattern of expression differs markedly. Isolated zinc finger genes were regionally mapped on chromosome 11 using fluorescence in situ suppression hybridization and demonstrated clustering of the genes at 11q13.3-11q13.4 and 11q23.1-11q23.2. Analysis of in situ hybridization to interphase nuclei demonstrated a maximum distance of 1 Mb separating distinct finger genes. This analysis defines two linked multigene families of zinc finger genes to chromosome bands associated with a high frequency of specific translocations associated with malignancies. 相似文献
129.
130.
Summary The regulatory sequences leading to the ovarian and fat body expression of yolk proteins 1 and 2 (YP1 and 2) of Drosophila melanogaster have been characterised in some detail. These genes (yp1 and yp2) share many enhancer elements, and some important regulatory sequences lie within the coding regions. We have begun to investigate the cis-regulation of the gene encoding yolk protein 3 (yp3). We describe a system for P element transformation using the complete and unaltered yp3 gene rather than reporter genes and describe sequences conferring correct expression in the ovary and carcass. 相似文献