全文获取类型
收费全文 | 951篇 |
免费 | 55篇 |
专业分类
1006篇 |
出版年
2021年 | 10篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 18篇 |
2013年 | 26篇 |
2012年 | 40篇 |
2011年 | 33篇 |
2010年 | 22篇 |
2009年 | 16篇 |
2008年 | 28篇 |
2007年 | 37篇 |
2006年 | 28篇 |
2005年 | 31篇 |
2004年 | 33篇 |
2003年 | 28篇 |
2002年 | 24篇 |
2001年 | 25篇 |
2000年 | 37篇 |
1999年 | 18篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1975年 | 24篇 |
1974年 | 21篇 |
1973年 | 18篇 |
1972年 | 10篇 |
1971年 | 49篇 |
1970年 | 11篇 |
1969年 | 19篇 |
1968年 | 25篇 |
1967年 | 9篇 |
1966年 | 9篇 |
1965年 | 6篇 |
排序方式: 共有1006条查询结果,搜索用时 0 毫秒
41.
Two human liver UDP-glucuronosyltransferase cDNA clones, HLUG25 [Jackson, M. R., et al. (1987) Biochem. J. 242, 581-588] and UDPGTh-2 [Ritter, J. K., et al. (1990) J. Biol. Chem. 266, 7900-7906] have previously been shown to encode isozymes active in the glucuronidation of hyodeoxycholic acid (HDCA) and certain estrogen derivatives (estriols and 3,4-catechol estrogens), respectively. Here we report that the UDPGTh-2-encoded isoform (udpgth-2) and the HLUG25-encoded isoform (udpgth-1) have parallel aglycon specificities. Following expression in COS-1 cells, each isoform metabolized three types of dihydroxy- or trihydroxy-substituted ring structures, including the 3,4-catechol estrogen (4-hydroxyestrone), estriol and 17-epiestriol, and HDCA, but the udpgth-2 isozyme is 100-fold more efficient than udpgth-1. udpgth-1 and udpgth-2 are 86% identical overall (76 differences out of 528 amino acids), including 55 differences in the first 300 amino acids of the amino terminus, a domain which confers isoform substrate specificity. The data indicate that a high level of conservation in the amino terminus is not required for the preservation of substrate selectivity. Analysis of glucuronidation activity encoded by UDPGTh-1/UDPGTh-2 chimeric cDNAs constructed at their common restriction sites, SacI (codon 297), NcoI (codon 385), and HhaI (codon 469), showed that nine amino acids between residues 385 and 469 are important for catalytic efficiency, suggesting that this region represents a domain which is critical for catalysis but distinct from that responsible for aglycon selection.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
42.
María Fernanda Lammoglia Cobo Julia Ritter Regina Gary Volkhard Seitz Josef Mautner Michael Aigner Simon Vlkl Stefanie Schaffer Stephanie Moi Anke Seegebarth Heiko Bruns Wolf Rsler Kerstin Amann Maike Büttner-Herold Steffen Hennig Andreas Mackensen Michael Hummel Andreas Moosmann Armin Gerbitz 《PLoS pathogens》2022,18(4)
Reconstitution of the T cell repertoire after allogeneic stem cell transplantation is a long and often incomplete process. As a result, reactivation of Epstein-Barr virus (EBV) is a frequent complication that may be treated by adoptive transfer of donor-derived EBV-specific T cells. We generated donor-derived EBV-specific T cells by stimulation with peptides representing defined epitopes covering multiple HLA restrictions. T cells were adoptively transferred to a patient who had developed persisting high titers of EBV after allogeneic stem cell transplantation for angioimmunoblastic T-cell lymphoma (AITL). T cell receptor beta (TCRβ) deep sequencing showed that the T cell repertoire of the patient early after transplantation (day 60) was strongly reduced and only very low numbers of EBV-specific T cells were detectable. Manufacturing and in vitro expansion of donor-derived EBV-specific T cells resulted in enrichment of EBV epitope-specific, HLA-restricted T cells. Monitoring of T cell clonotypes at a molecular level after adoptive transfer revealed that the dominant TCR sequences from peptide-stimulated T cells persisted long-term and established an EBV-specific TCR clonotype repertoire in the host, with many of the EBV-specific TCRs present in the donor. This reconstituted repertoire was associated with immunological control of EBV and with lack of further AITL relapse. 相似文献
43.
Andreas Ritter Mourad Sanhaji Alexandra Friemel Susanne Roth Udo Rolle Frank Louwen Juping Yuan 《Cell cycle (Georgetown, Tex.)》2015,14(23):3755-3767
Mitotic centromere-associated kinesin (MCAK) is the best characterized member of the kinesin-13 family and plays important roles in microtubule dynamics during mitosis. Its activity and subcellular localization is tightly regulated by an orchestra of mitotic kinases, such as Aurora B. It is well known that serine 196 of MCAK is the major phosphorylation site of Aurora B in Xenopus leavis extracts and that this phosphorylation regulates its catalytic activity and subcellular localization. In the current study, we have addressed the conserved phosphorylation site serine 192 in human MCAK to characterize its function in more depth in human cancer cells. Our data confirm that S192 is the major phosphorylation site of Aurora B in human MCAK and that this phosphorylation has crucial roles in regulating its catalytic activity and localization at the kinetochore/centromere region in mitosis. Interfering with this phosphorylation leads to a delayed progression through prometa- and metaphase associated with mitotic defects in chromosome alignment and segregation. We show further that MCAK is involved in directional migration and invasion of tumor cells, and interestingly, interference with the S192 phosphorylation affects this capability of MCAK. These data provide the first molecular explanation for clinical observation, where an overexpression of MCAK was associated with lymphatic invasion and lymph node metastasis in gastric and colorectal cancer patients. 相似文献
44.
Drugs purchased by a random sample (17 000) of the population of Jämtland county, Sweden, are continuously monitored. Patients who had been admitted to the county''s only hospital with acute cholecystitis and who were part of this sample were studied, and controls matched for age and sex were drawn from the sample. The purchase of thiazides and other drugs prescribed to the patients with acute cholecystitis was compared with that of the controls. The estimated relative risk of developing acute cholecystitis in patients who had purchased thiazides in the year before admission to hospital, as compared with those who had not, was 2.1 (95% confidence limit 1.1-3.9). As it has been reliably reported that the use of thiazides is not itself associated with cholelithiasis, the association found between thiazides and cholecystitis suggests that thiazides may increase the risk of acute cholecystitis developing in a patient with gall stones. 相似文献
45.
46.
Micaela Medina Magali Prez Flores Juan Francisco Goya Paula Ines Campanello Martin Alcides Pinazo Luis Javier Ritter Marcelo Fabian Arturi 《Austral ecology》2020,45(2):229-239
Deforestation is a global process that has strongly affected the Atlantic Forest in South America, which has been recognised as a threatened biodiversity hotspot. An important proportion of deforested areas were converted to forest plantations. Araucaria angustifolia is a native tree to the Atlantic Forest, which has been largely exploited for wood production and is currently cultivated in commercial plantations. An important question is to what extent such native tree plantations can be managed to reduce biodiversity loss in a highly diverse and vulnerable forest region . We evaluated the effect of stand age, stand basal area, as a measure of stand density, and time since last logging on the density and richness of native tree regeneration in planted araucaria stands that were successively logged over 60 years, as well as the differences between successional groups in the response of plant density to stand variables. We also compared native tree species richness in planted araucaria stands to neighbouring native forest. Species richness was 71 in the planted stands (27 ha sampled) and 82 in native forest (18 ha sampled) which approximate the range of variation in species richness found in the native forests of the study area. The total abundance and species richness of native trees increased with stand age and time since last logging, but ecological groups differed in their response to such variables. Early secondary trees increased in abundance with stand age 3–8 times faster than climax or late secondary trees. Thus, the change in species composition is expected to continue for a long term. The difference in species richness between native forest and planted stands might be mainly explained by the difference in plant density. Therefore, species richness in plantations can contribute to local native tree diversity if practices that increase native tree density are implemented. 相似文献
47.
Dave Lutgen Raphael Ritter Remi‐Andr Olsen Holger Schielzeth Joel Gruselius Philip Ewels Jesús T. García Hadoram Shirihai Manuel Schweizer Alexander Suh Reto Burri 《Molecular ecology resources》2020,20(5):1311-1322
The feasibility to sequence entire genomes of virtually any organism provides unprecedented insights into the evolutionary history of populations and species. Nevertheless, many population genomic inferences – including the quantification and dating of admixture, introgression and demographic events, and inference of selective sweeps – are still limited by the lack of high‐quality haplotype information. The newest generation of sequencing technology now promises significant progress. To establish the feasibility of haplotype‐resolved genome resequencing at population scale, we investigated properties of linked‐read sequencing data of songbirds of the genus Oenanthe across a range of sequencing depths. Our results based on the comparison of downsampled (25×, 20×, 15×, 10×, 7×, and 5×) with high‐coverage data (46–68×) of seven bird genomes mapped to a reference suggest that phasing contiguities and accuracies adequate for most population genomic analyses can be reached already with moderate sequencing effort. At 15× coverage, phased haplotypes span about 90% of the genome assembly, with 50% and 90% of phased sequences located in phase blocks longer than 1.25–4.6 Mb (N50) and 0.27–0.72 Mb (N90). Phasing accuracy reaches beyond 99% starting from 15× coverage. Higher coverages yielded higher contiguities (up to about 7 Mb/1 Mb [N50/N90] at 25× coverage), but only marginally improved phasing accuracy. Phase block contiguity improved with input DNA molecule length; thus, higher‐quality DNA may help keeping sequencing costs at bay. In conclusion, even for organisms with gigabase‐sized genomes like birds, linked‐read sequencing at moderate depth opens an affordable avenue towards haplotype‐resolved genome resequencing at population scale. 相似文献
48.
Steven A. Yukl Shahzada Khan Tsui-Hua Chen Martin Trapecar Frank Wu Guorui Xie Sushama Telwatte Daniel Fulop Alexander R. Pico Gregory M. Laird Kristen D. Ritter Norman G. Jones Chuanyi M. Lu Robert F. Siliciano Nadia R. Roan Jeffrey M. Milush Ma Somsouk Steven G. Deeks Peter W. Hunt Shomyseh Sanjabi 《Journal of virology》2021,95(2)
49.
Erich K. Ritter Juerg M. Brunnschweiler 《Marine and Freshwater Behaviour and Physiology》2013,45(2):111-113
The eyes and aspects of vision of the Amazonian manatee Trichechus inunguis NATTERER 1883: (Sirenia: mammalia) have been examined in five animals, in relation to previous findings for sirenians. This paper presents a review of previous findings confirming those upon gross ocular anatomy, retinal histology and ocular refraction. The confirmation of a primarily rod retina, high receptor: ganglion cell ratio and low refractive error under water were of note. A visual pigment based upon vitamin A1 and a difference spectrum of λ max at 505 nm was in agreement with Dartnalls nomogram. The findings suggest a retina more suited to low light levels and at best, moderate visual acuity, though motion perception appears present and a low degree of binocular vision possible. 相似文献
50.
Stefan Rüttermann Taina Trellenkamp Nora Bergmann Thomas Beikler Helmut Ritter Ralf Janda 《PloS one》2013,8(11)