全文获取类型
收费全文 | 6743篇 |
免费 | 533篇 |
国内免费 | 1篇 |
专业分类
7277篇 |
出版年
2023年 | 42篇 |
2022年 | 116篇 |
2021年 | 192篇 |
2020年 | 118篇 |
2019年 | 132篇 |
2018年 | 155篇 |
2017年 | 124篇 |
2016年 | 218篇 |
2015年 | 393篇 |
2014年 | 421篇 |
2013年 | 494篇 |
2012年 | 624篇 |
2011年 | 559篇 |
2010年 | 367篇 |
2009年 | 353篇 |
2008年 | 456篇 |
2007年 | 416篇 |
2006年 | 358篇 |
2005年 | 300篇 |
2004年 | 266篇 |
2003年 | 288篇 |
2002年 | 258篇 |
2001年 | 50篇 |
2000年 | 36篇 |
1999年 | 65篇 |
1998年 | 50篇 |
1997年 | 46篇 |
1996年 | 27篇 |
1995年 | 35篇 |
1994年 | 36篇 |
1993年 | 31篇 |
1992年 | 28篇 |
1991年 | 17篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1974年 | 9篇 |
1973年 | 5篇 |
1970年 | 5篇 |
1969年 | 8篇 |
排序方式: 共有7277条查询结果,搜索用时 15 毫秒
101.
Belinda Martineau H. Jane Smith Caroline Dean Pamela Dunsmuir John Bedbrook Laurens J. Mets 《Plant molecular biology》1989,13(4):419-426
We report the successful transformation, via Agrobacterium tumefaciens infection, and regeneration of two species of the genus Flaveria: F. brownii and F. palmeri. We document the expression of a C3 plant gene, an abundantly expressed ribulose 1,5-bisphosphate carboxylase/oxygenase small subunit gene isolated from petunia, in these C4 plants. The organ-specific expression of this petunia gene in Flaveria brownii is qualitatively identical to its endogenous pattern of expression. 相似文献
102.
An electro-transformation procedure was established for Bacillus cereus ATCC 14579. Using early growth-stage culture and high electric field, the ectroporation efficiency was up to 2 x 10(9) cfu microg(-1) ml(-1) with pC194 plasmid DNA. The procedure was tested with three other plasmids, of various sizes, replication mechanisms and selection markers, and the transformation efficiencies ranged between 2 x 10(6) and 1 x 10(8) cfu microg(-1) ml(-)(1). The effects of two wall-weakening agents on electroporation rates were also evaluated. The transformation rate that was reached with our procedure is 10(3) times higher than that previously obtained with members of the Bacillus genus with similar plasmids, and 10(6) times superior than that achieved with available protocols for B. cereus. The proposed method is quick, simple, efficient with small rolling circle plasmids and large theta replicating plasmids with low copy number per cell, and suitable for many genetic manipulations that are not possible without high-efficiency transformation protocols. 相似文献
103.
Qiu Z Norflus F Singh B Swindell MK Buzescu R Bejarano M Chopra R Zucker B Benn CL DiRocco DP Cha JH Ferrante RJ Hersch SM 《The Journal of biological chemistry》2006,281(24):16672-16680
104.
105.
Age matters in the prevalence and clinical significance of ultra‐high‐risk for psychosis symptoms and criteria in the general population: Findings from the BEAR and BEARS‐kid studies 下载免费PDF全文
Benno G. Schimmelmann Chantal Michel Alexandra Martz-Irngartinger Caroline Linder Frauke Schultze-Lutter 《World psychiatry》2015,14(2):189-197
Early detection of psychosis is an important topic in psychiatry. Yet, there is limited information on the prevalence and clinical significance of high‐risk symptoms in children and adolescents as compared to adults. We examined ultra‐high‐risk (UHR) symptoms and criteria in a sample of individuals aged 8‐40 years from the general population of Canton Bern, Switzerland, enrolled from June 2011 to May 2014. The current presence of attenuated psychotic symptoms (APS) and brief intermittent psychotic symptoms (BLIPS) and the fulfillment of onset/worsening and frequency requirements for these symptoms in UHR criteria were assessed using the Structured Interview for Psychosis Risk Syndromes. Additionally, perceptive and non‐perceptive APS were differentiated. Psychosocial functioning and current non‐psychotic DSM‐IV axis I disorders were also surveyed. Well‐trained psychologists performed assessments. Altogether, 9.9% of subjects reported APS and none BLIPS, and 1.3% met all the UHR requirements for APS. APS were related to more current axis I disorders and impaired psychosocial functioning, indicating some clinical significance. A strong age effect was detected around age 16: compared to older individuals, 8‐15‐year olds reported more perceptive APS, that is, unusual perceptual experiences and attenuated hallucinations. Perceptive APS were generally less related to functional impairment, regardless of age. Conversely, non‐perceptive APS were related to low functioning, although this relationship was weaker in those below age 16. Future studies should address the differential effects of perceptive and non‐perceptive APS, and their interaction with age, also in terms of conversion to psychosis. 相似文献
106.
107.
Polymorphic analysis of the three MHC-linked HSP70 genes 总被引:10,自引:0,他引:10
Three genes encoding members of the M
r 70 000 heat shock protein family (HSP70) are known to lie in the class III region of the human major histocompatibility complex. IN order to determine whether these genes or their protein products exhibit any polymorphism the three genes have been specifically amplified from genomic DNA and sequenced. The HSP70-1 and HSP70-2 genes encode the major heat-inducible HSP70. A comparison of the nucleotide sequences of these genes from B8, SC01, DR3, B18, F1C30, DR3, and B7, SC30, DR2 haplotypes has revelad only very limited sequence variation which is not associated with any amino acid polymorphism. The HSP70-Hom gene encodes a protein that is highly related to HSP70-1, but which is not heat-inducible. Nucleotide sequence analysis of this gene from different haplotypes has revealed a Met Thr amino acid substitution at residue 493 in a number of the haplotypes tested. This variable amino acid lies in the proposed peptide-binding site of the HSP70-Hom protein.
Address correspondence and offprint requests to: R. D. Campbell. 相似文献
108.
Pablo Suárez Cleusa Yoshiko Nagamachi Cecilia Lanzone Matias Maximiliano Malleret Patricia Caroline Mary O’Brien Malcolm Andrew Ferguson-Smith Julio Cesar Pieczarka 《PloS one》2015,10(12)
Sigmodontinae rodents represent one of the most diverse and complex components of the mammalian fauna of South America. Among them most species belongs to Oryzomyini and Akodontini tribes. The highly specific diversification observed in both tribes is characterized by diploid complements, which vary from 2n = 10 to 86. Given this diversity, a consistent hypothesis about the origin and evolution of chromosomes depends on the correct establishment of synteny analyzed in a suitable phylogenetic framework. The chromosome painting technique has been particularly useful for identifying chromosomal synteny. In order to extend our knowledge of the homeological relationships between Akodontini and Oryzomyini species, we analyzed the species Akodon montensis (2n = 24) and Thaptomys nigrita (2n = 52) both from the tribe Akodontini, with chromosome probes of Hylaeamys megacephalus (2n = 54) of the tribe Oryzomyini. The results indicate that at least 12 of the 26 autosomes of H. megacephalus show conserved synteny in A. montensis and 14 in T. nigrita. The karyotype of Akodon montensis, as well as some species of the Akodon cursor species group, results from many chromosomal fusions and therefore the syntenic associations observed probably represent synapomorphies. Our finding of a set of such associations revealed by H. megacephalus chromosome probes (6/21; 3/25; 11/16/17; and, 14/19) provides phylogenetic information for both tribes. An extension of these observations to other members of Akodontini and Oryzomyini tribes should improve our knowledge about chromosome evolution in both these groups. 相似文献
109.
110.
The Mre11 complex is required for ATM activation and the G2/M checkpoint 总被引:25,自引:0,他引:25 下载免费PDF全文
Carson CT Schwartz RA Stracker TH Lilley CE Lee DV Weitzman MD 《The EMBO journal》2003,22(24):6610-6620
The maintenance of genome integrity requires a rapid and specific response to many types of DNA damage. The conserved and related PI3-like protein kinases, ataxia-telangiectasia mutated (ATM) and ATM-Rad3-related (ATR), orchestrate signal transduction pathways in response to genomic insults, such as DNA double-strand breaks (DSBs). It is unclear which proteins recognize DSBs and activate these pathways, but the Mre11/Rad50/NBS1 complex has been suggested to act as a damage sensor. Here we show that infection with an adenovirus lacking the E4 region also induces a cellular DNA damage response, with activation of ATM and ATR. Wild-type virus blocks this signaling through degradation of the Mre11 complex by the viral E1b55K/E4orf6 proteins. Using these viral proteins, we show that the Mre11 complex is required for both ATM activation and the ATM-dependent G(2)/M checkpoint in response to DSBs. These results demonstrate that the Mre11 complex can function as a damage sensor upstream of ATM/ATR signaling in mammalian cells. 相似文献