全文获取类型
收费全文 | 4113篇 |
免费 | 459篇 |
国内免费 | 1篇 |
出版年
2022年 | 36篇 |
2021年 | 84篇 |
2020年 | 38篇 |
2019年 | 51篇 |
2018年 | 63篇 |
2017年 | 56篇 |
2016年 | 87篇 |
2015年 | 144篇 |
2014年 | 152篇 |
2013年 | 228篇 |
2012年 | 223篇 |
2011年 | 220篇 |
2010年 | 123篇 |
2009年 | 126篇 |
2008年 | 179篇 |
2007年 | 153篇 |
2006年 | 144篇 |
2005年 | 179篇 |
2004年 | 172篇 |
2003年 | 142篇 |
2002年 | 125篇 |
2001年 | 83篇 |
2000年 | 99篇 |
1999年 | 101篇 |
1998年 | 67篇 |
1997年 | 57篇 |
1996年 | 51篇 |
1995年 | 45篇 |
1994年 | 49篇 |
1993年 | 39篇 |
1992年 | 79篇 |
1991年 | 70篇 |
1990年 | 77篇 |
1989年 | 66篇 |
1988年 | 55篇 |
1987年 | 65篇 |
1986年 | 42篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 32篇 |
1982年 | 31篇 |
1980年 | 33篇 |
1979年 | 46篇 |
1978年 | 43篇 |
1977年 | 37篇 |
1975年 | 25篇 |
1974年 | 31篇 |
1973年 | 26篇 |
1971年 | 29篇 |
1967年 | 31篇 |
排序方式: 共有4573条查询结果,搜索用时 15 毫秒
91.
92.
Christopher C. Austin 《Molecular biotechnology》1995,4(1):100-101
This article presents a relatively quick and cost-effective DNA sequencing method that prevents the formation of stop-bands. This method uses a combination ofTaq and Sequenase that allows sequencing at both low and high temperatures. The ability to sequence at a high temperature appears to be the fundamental component in preventing stop-band formation in G + C rich regions. 相似文献
93.
J. Austin Burns Hazel Y. Wetzstein 《In vitro cellular & developmental biology. Plant》1995,31(2):72-78
Aggregates of globular and pre-globular stage somatic embryos from suspension cultures of pecan (Carya illinoensis Koch) were cultured on solidified media for embryo development. Embryo aggregates and pre-globular stage embryo masses were
given various treatments to further ontologic development. A 2- to 4-wk mild dehydration of the embryo aggregates suppressed
recurrent embryogenesis, promoted development of globular embryos into cotyledonary stage embryos, and enhanced plant development
beyond germination. Fine embryogenic tissue masses filtered from suspension formed cotyledonary-staged embryos when the collection
filters were plated on solified medium. The embryogenic capacity of preglobular stage embryo masses was compared between media
supplemented with varying concentrations of polyethylene glycol (molecular weight 8 000) vs. filter overlays. The filter paper
overlays were not necessary for embryo development. An inverse relationship was found between the number of embryos that developed
and the concentration of polyethylene glycol in the medium. However, this relationship was reversed for ability of embryos
to germinate and develop into a plant. 相似文献
94.
Locus Heterogeneity for Waardenburg Syndrome is Predictive of Clinical Subtypes 总被引:5,自引:4,他引:1
下载免费PDF全文
![点击此处可从《American journal of human genetics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lindsay A. Farrer Kathleen S. Arnos James H. Asher Clinton T. Baldwin Scott R. Diehl Thomas B. Friedman Jacquie Greenberg Kenneth M. Grundfast Christopher Hoth Anil K. Lalwani Barbara Landa Kate Leverton Aubrey Milunsky Robert Morell Walter E. Nance Valerie Newton Rajkumar Ramesar Valluri S. Rao Jennifer E. Reynolds Theresa B. San Agustin Edward R. Wilcox Ingrid Winship Andrew P. Read 《American journal of human genetics》1994,55(4):728-737
Waardenburg syndrome (WS) is a dominantly inherited and clinically variable syndrome of deafness, pigmentary changes, and distinctive facial features. Clinically, WS type I (WS1) is differentiated from WS type II (WS2) by the high frequency of dystopia canthorum in the family. In some families, WS is caused by mutations in the PAX3 gene on chromosome 2q. We have typed microsatellite markers within and flanking PAX3 in 41 WS1 kindreds and 26 WS2 kindreds in order to estimate the proportion of families with probable mutations in PAX3 and to study the relationship between phenotypic and genotypic heterogeneity. Evaluation of heterogeneity in location scores obtained by multilocus analysis indicated that WS is linked to PAX3 in 60% of all WS families and in 100% of WS1 families. None of the WS2 families were linked. In those families in which equivocal lod scores (between −2 and +1) were found, PAX3 mutations have been identified in 5 of the 15 WS1 families but in none of the 4 WS2 families. Although preliminary studies do not suggest any association between the phenotype and the molecular pathology in 20 families with known PAX3 mutations and in four patients with chromosomal abnormalities in the vicinity of PAX3, the presence of dystopia in multiple family members is a reliable indicator for identifying families likely to have a defect in PAX3. 相似文献
95.
96.
97.
Partial sequencing and mapping of clones from two maize cDNA libraries 总被引:11,自引:0,他引:11
98.
99.
The homologous operons for P1 and P7 plasmid partition are autoregulated from dissimilar operator sites 总被引:12,自引:3,他引:9
Finbarr Hayes Lyndsay Radnedge Michael A. Davis Stuart J. Austin 《Molecular microbiology》1994,11(2):249-260
The plasmid-partition regions of the P1 and P7 plasmid prophages in Escherichia coli are homologues which each encode two partition proteins, ParA and ParB. The equivalent PI and P7 proteins are closely related. In each case, the proteins are encoded by an operon that is autoregulated by the ParA and ParB proteins in concert. This regulation is species-specific, as the P1 proteins are unable to repress the P7 par operon and vice versa. The homologous ParA proteins are primarily responsible for repression and bind to regions that overlap the operon promoter in both cases. The DNA-binding domain of the P7 auto-repressor lies in the amino-terminal end of the P7 ParA protein. This region includes a helix-turn-helix motif that has a clear counterpart in the P1 ParA sequence. However, despite the common regulatory mechanism and the similarity of the proteins involved in repression, the promoter-operator sequences of these two operons are very different in sequence and organization. The operator is located downstream of the promoter in P1 and upstream of it in P7, and the two regions show little, if any, homology. How these differences may have arisen from a common ancestral form is discussed. 相似文献
100.
J. Geddes R. Newton G. Young S. Bailey C. Freeman R. Priest 《BMJ (Clinical research ed.)》1994,308(6932):816-819
OBJECTIVE--To determine whether the prevalence of schizophrenia among the homeless population of Edinburgh resident in hostels has changed between 1966 and 1992. DESIGN--Comparison of two cross sectional surveys. SETTINGS--Hostels for homeless people in Edinburgh. SUBJECTS--In 1966 a random sample of 98 residents of three common lodging houses. In 1992 a random sample of 198 residents of nine hostels. MAIN OUTCOME MEASURE--Prevalence of schizophrenia. RESULTS--The prevalence of schizophrenia in 1992 was 12/136 (9%) compared with 20/79 (25%) in 1966 (odds ratio 0.29; 95% confidence interval 0.13 to 0.62; P = 0.001). Adjustment for confounding by age, current hostel, and duration of unemployment by means of logistic regression produced an adjusted odds ratio of 0.22 (0.08 to 0.58). CONCLUSIONS--The prevalence of schizophrenia was lower in 1992 even after other changes in the population resident in hostels occurring between 1966 and 1992 were taken into account. The findings are not consistent with an increase in the prevalence of schizophrenia among homeless people despite a 66% reduction in adult psychiatric beds in the region during 1966-92. 相似文献