全文获取类型
收费全文 | 951篇 |
免费 | 90篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 22篇 |
2017年 | 20篇 |
2016年 | 40篇 |
2015年 | 33篇 |
2014年 | 54篇 |
2013年 | 57篇 |
2012年 | 88篇 |
2011年 | 70篇 |
2010年 | 61篇 |
2009年 | 52篇 |
2008年 | 67篇 |
2007年 | 71篇 |
2006年 | 48篇 |
2005年 | 41篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 34篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1980年 | 2篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1958年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有1041条查询结果,搜索用时 15 毫秒
41.
42.
Amy Lu Carola Borries Nancy M. Czekala Jacinta C. Beehner 《American journal of primatology》2010,72(12):1073-1081
Understanding female reproductive characteristics is important for assessing fertility, interpreting female behavior, and designing appropriate conservation and captive management plans. In primate species lacking morphological signs of receptivity, such as most colobines, determination of reproductive parameters depends on the analysis of reproductive hormones. Here, we use fecal hormone analysis to characterize cycle patterns (N=6 females) and gestation length (N=7 females) in a group of wild Phayre's leaf monkeys (Trachypithecus phayrei crepusculus) in Phu Khieo Wildlife Sanctuary, Thailand. We found that both fecal estrogen (fE) and progestin (fP) levels showed clear biological patterns indicative of ovulation and conception. However, because fP patterns were inadequate in determining the end of the luteal phase, we used fE rather than fP patterns to delineate menstrual cycle parameters. We found a mean cycle length of 28.4 days (N=10), with follicular and luteal phases of 15.4 (N=10) and 12.5 days (N=14), respectively. On average, females underwent 3.57 (N=7) cycles until conception. Average gestation length was 205.3 days (N=7), with fE levels increasing over the course of pregnancy. Overall, the reproductive characteristics found for Phayre's leaf monkeys were consistent with results for other colobine species, suggesting that fecal hormone monitoring, particularly for fE metabolites, can provide useful reproductive information for this species. Am. J. Primatol. 72:1073–1081, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
43.
Perrone A Deramo MT Spaccavento F Santarcangelo P Favoino B Antonaci S 《Cytobios》2001,106(Z1):125-134
Patients with chronic hepatitis C virus (HCV) infection (530 in toto), and 294 individuals with chronic liver disease of different aetiology, were enrolled in this study to investigate the prevalence of monoclonal gammopathies (MG) during chronic liver dysfunction. A monoclonal band was detected in 61 HCV+ patients and in nine HCV subjects only. In both instances, a correlation between MG presence and advanced age or degree of hepatic injury was noted. The prevalence of HCV genotype 2a was higher in HCV+ patients with, rather than in those without, MG. The MG+ HCV+ subjects did not exhibit human leukocyte antigen (HLA)-A33, B8, B65 and DR16 expression, while an increased frequency of DR15 structure was seen in the same group of individuals in comparison with MG- HCV+ patients and healthy donors. These findings suggest a possible relationship between HLA haplotype expression, virus genotypes and the occurrence of MG during the course of chronic HCV infection. 相似文献
44.
Stoesser G Baker W van den Broek A Garcia-Pastor M Kanz C Kulikova T Leinonen R Lin Q Lombard V Lopez R Mancuso R Nardone F Stoehr P Tuli MA Tzouvara K Vaughan R 《Nucleic acids research》2003,31(1):17-22
The EMBL Nucleotide Sequence Database (http://www.ebi.ac.uk/embl/) incorporates, organizes and distributes nucleotide sequences from all available public sources. The database is located and maintained at the European Bioinformatics Institute (EBI) near Cambridge, UK. In an international collaboration with DDBJ (Japan) and GenBank (USA), data are exchanged amongst the collaborating databases on a daily basis to achieve optimal synchronization. Webin is the preferred web-based submission system for individual submitters, while automatic procedures allow incorporation of sequence data from large-scale genome sequencing centres and from the European Patent Office (EPO). Database releases are produced quarterly. Network services allow free access to the most up-to-date data collection via FTP, Email and World Wide Web interfaces. EBI's Sequence Retrieval System (SRS) integrates and links the main nucleotide and protein databases plus many other specialized molecular biology databases. For sequence similarity searching, a variety of tools (e.g. Fasta, BLAST) are available which allow external users to compare their own sequences against the latest data in the EMBL Nucleotide Sequence Database and SWISS-PROT. All resources can be accessed via the EBI home page at http://www.ebi.ac.uk. 相似文献
45.
A new genus of Nippostrongylinae, Malvinema n. gen., with 3 coparasitic species M. frederici n. sp., M. carolinae n. sp., and M. victoriae n. sp. from the intestine of the water rat, Scapteromys aquaticus Thomas (Rodentia: Muridae), from the northeast of Buenos Aires Province, Argentina, is proposed in this study. The new genus shows similarities to 2 Neotropical Nippostrongylinae: Carolinensis (Travassos, 1937) by some characters of the synlophe and Stilestrongylus Freitas, Lent and Almeida, 1937, by the pattern of the caudal bursa. It is characterized by a synlophe with triple or quadruple gradient of size of the ridges, lateromedian, decreasing from the largest left and right ridges. The gradient situated in the right ventral quadrant is always present. The caudal bursa shows a pattern of type 1-4. Malvinema frederici possesses a synlophe with 17 ridges and an axis of orientation inclined at 45 degrees from the sagittal axis; M. carolinae possesses a synlophe with 22-24 ridges and an axis of orientation almost merged with the sagittal axis. Both species have a caudal bursa with the right lobe enlarged transversally. Malvinema victoriae possesses a synlophe with 22-24 ridges, an axis of orientation inclined at 45 degrees from the sagittal axis, and a caudal bursa with the right lobe enlarged vertically. 相似文献
46.
47.
Zickermann V Bostina M Hunte C Ruiz T Radermacher M Brandt U 《The Journal of biological chemistry》2003,278(31):29072-29078
Membrane-bound complex I (NADH:ubiquinone oxidoreductase) of the respiratory chain is considered the main site of mitochondrial radical formation and plays a major role in many mitochondrial pathologies. Structural information is scarce for complex I, and its molecular mechanism is not known. Recently, the 49-kDa subunit has been identified as part of the "catalytic core" conferring ubiquinone reduction by complex I. We found that the position of the 49-kDa subunit is clearly separated from the membrane part of complex I, suggesting an indirect mechanism of proton translocation. This contradicts all hypothetical mechanisms discussed in the field that link proton translocation directly to redox events and suggests an indirect mechanism of proton pumping by redox-driven conformational energy transfer. 相似文献
48.
49.
Acetogens reduce CO2 to acetate via the acetyl-CoA pathway and have been classically thought of as obligately anaerobic bacteria. Nearly 100 acetogenic
species from 20 different genera have been isolated to date. These isolates are able to use very diverse electron donors and
acceptors, and it is thus very likely that the in situ activities of acetogens are very diverse and not restricted to acetogenesis. Since acetogens constitute a very phylogenetically
diverse bacteriological group, it should be anticipated that they can inhabit, and have impact on, diverse habitats. Indeed,
they have been isolated from a broad range of habitats, including oxic soils and other habitats not generally regarded as
suitable for acetogens. Although the ecological impact of acetogens is determined by the in situ manifestation of their physiological potentials, assessing their in situ activities is difficult due to their physiological and phylogenetic diversities. This mini-review will highlight a few of
the physiological and ecological realities of acetogens, and will focus on: (i) metabolic diversities and regulation, (ii)
phylogenetic diversity and molecular ecology, and (iii) the capacity of acetogens to cope with oxic conditions under both
laboratory and in situ conditions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
50.