全文获取类型
收费全文 | 2423篇 |
免费 | 206篇 |
专业分类
2629篇 |
出版年
2023年 | 12篇 |
2022年 | 36篇 |
2021年 | 69篇 |
2020年 | 55篇 |
2019年 | 55篇 |
2018年 | 65篇 |
2017年 | 68篇 |
2016年 | 91篇 |
2015年 | 120篇 |
2014年 | 165篇 |
2013年 | 174篇 |
2012年 | 205篇 |
2011年 | 155篇 |
2010年 | 116篇 |
2009年 | 84篇 |
2008年 | 121篇 |
2007年 | 112篇 |
2006年 | 96篇 |
2005年 | 78篇 |
2004年 | 69篇 |
2003年 | 84篇 |
2002年 | 77篇 |
2001年 | 45篇 |
2000年 | 27篇 |
1999年 | 31篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 22篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1979年 | 18篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1972年 | 8篇 |
1970年 | 7篇 |
1968年 | 8篇 |
排序方式: 共有2629条查询结果,搜索用时 15 毫秒
51.
Thiago F. Rodrigues Aline M. B. Mantellatto Mariella Superina Adriano G. Chiarello 《Biological reviews of the Cambridge Philosophical Society》2020,95(1):1-21
Awareness of the natural ecological processes provided by organisms that benefit human well‐being has significantly progressed towards the goal of making conservation a mainstream value. Identifying different services and the species that provide them is a vital first step for the management and maintenance of these so‐called ecosystem services. Herein, we specifically address the armadillos, which play key functional roles in terrestrial ecosystems, including as ecosystem engineers, predators, and vectors of invertebrates and nutrients, although these roles have often been overlooked. Armadillos can control pests, disperse seeds, and be effective sentinels of potential disease outbreaks or bioindicators of environmental contaminants. They also supply important material (meat, medicines) and non‐material (learning, inspiration) contributions all over the Americas. We identify key gaps in the understanding of ecosystem services provided by armadillos and areas for future research required to clarify their functional role in terrestrial ecosystems and the services they supply. Such information will produce powerful arguments for armadillo conservation. 相似文献
52.
53.
54.
Human polypyrimidine tract-binding protein PTB is a multifunctional RNA-binding protein with four RNA recognition motifs (RRM1 to RRM4). PTB is a nucleocytoplasmic shuttle protein that functions as a key regulator of alternative pre-mRNA splicing in the nucleoplasm and promotes internal ribosome entry site-mediated translation initiation of viral and cellular mRNAs in the cytoplasm. Here, we demonstrate that PTB and its paralogs, nPTB and ROD1, specifically interact with mitochondrial (mt) tRNAThr both in human and mouse cells. In vivo and in vitro RNA-binding experiments demonstrate that PTB forms a direct interaction with the T-loop and the D-stem-loop of mt tRNAThr using its N-terminal RRM1 and RRM2 motifs. RNA sequencing and cell fractionation experiments show that PTB associates with correctly processed and internally modified, mature mt tRNAThr in the cytoplasm outside of mitochondria. Consistent with this, PTB activity is not required for mt tRNAThr biogenesis or for correct mitochondrial protein synthesis. PTB association with mt tRNAThr is largely increased upon induction of apoptosis, arguing for a potential role of the mt tRNAThr/PTB complex in apoptosis. Our results lend strong support to the recently emerging conception that human mt tRNAs can participate in novel cytoplasmic processes independent from mitochondrial protein synthesis. 相似文献
55.
56.
P. S. Springer E. A. Zimmer J. L. Bennetzen 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,77(6):844-850
Summary The structure and organization of the ribosomal DNA (rDNA) of sorghum (Sorghum bicolor) and several closely related grasses were determined by gel blot hybridization to cloned maize rDNA. Monocots of the genus Sorghum (sorghum, shattercane, Sudangrass, and Johnsongrass) and the genus Saccharum (sugarcane species) were observed to organize their rDNA as direct tandem repeats of several thousand rDNA monomer units. For the eight restriction enzymes and 14 cleavage sites examined, no variations were seen within all of the S. bicolor races and other Sorghum species investigated. Sorghum, maize, and sugarcane were observed to have very similar rDNA monomer sizes and restriction maps, befitting their close common ancestry. The restriction site variability seen between these three genera demonstrated that sorghum and sugarcane are more closely related to each other than either is to maize. Variation in rDNA monomer lengths were observed frequently within the Sorghum genus. These size variations were localized to the intergenic spacer region of the rDNA monomer. Unlike many maize inbreds, all inbred Sorghum diploids were found to contain only one rDNA monomer size in an individual plant. These results are discussed in light of the comparative timing, rates, and modes of evolutionary events in Sorghum and other grasses. Spacer size variation was found to provide a highly sensitive assay for the genetic contribution of different S. bicolor races and other Sorghum species to a Sorghum population. 相似文献
57.
PARma is a complete data analysis software for AGO-PAR-CLIP experiments to identify target sites of microRNAs as well as the microRNA binding to these sites. It integrates specific characteristics of the experiments into a generative model. The model and a novel pattern discovery tool are iteratively applied to data to estimate seed activity probabilities, cluster confidence scores and to assign the most probable microRNA. Based on differential PAR-CLIP analysis and comparison to RIP-Chip data, we show that PARma is more accurate than existing approaches. PARma is available from http://www.bio.ifi.lmu.de/PARma 相似文献
58.
Bibiana S. O. Fam Guillermo Reales Pedro Vargas‐Pinilla Pamela Par Lucas H. Viscardi Vinicius A. Sortica Aline B. Felkl lvaro de O. Franco Aldo B. Lucion Claudio M. Costa‐Neto Alcides Pissinatti Francisco M. Salzano Vanessa R. Paixo‐Crtes Maria Ctira Bortolini 《American journal of primatology》2019,81(8)
Platyrrhini (New World monkeys, NWm) are a group of primates characterized by behavioral and reproductive traits that are otherwise uncommon among primates, including social monogamy, direct paternal care, and twin births. As a consequence, the study of Platyrrhine primates is an invaluable tool for the discovery of the genetic repertoire underlying these taxon‐specific traits. Recently, high conservation of vasopressin (AVP) sequence, in contrast with high variability of oxytocin (OXT), has been described in NWm. AVP and OXT functions are possible due to interaction with their receptors: AVPR1a, AVPR1b, AVPR2, and OXTR; and the variability in this system is associated with the traits mentioned above. Understanding the variability in the receptors is thus fundamental to understand the function and evolution of the system as a whole. Here we describe the variability of AVPR1b coding region in 20 NWm species, which is well‐known to influence behavioral traits such as aggression, anxiety, and stress control in placental mammals. Our results indicate that 4% of AVPR1b sites may be under positive selection and a significant number of sites under relaxed selective constraint. Considering the known role of AVPR1b, we suggest that some of the changes described here for the Platyrrhini may be a part of the genetic repertoire connected with the complex network of neuroendocrine mechanisms of AVP–OXT system in the modulation of the HPA axis. Thus, these changes may have promoted the emergence of social behaviors such as direct paternal care in socially monogamous species that are also characterized by small body size and twin births. 相似文献
59.
60.
Aline Marnef Maria Maldonado Anthony Bugaut Shankar Balasubramanian Michel Kress Dominique Weil Nancy Standart 《RNA (New York, N.Y.)》2010,16(11):2094-2107
We previously identified Xenopus Pat1a (P100) as a member of the maternal CPEB RNP complex, whose components resemble those of P-(rocessing) bodies, and which is implicated in translational control in Xenopus oocytes. Database searches have identified Pat1a proteins in other vertebrates, as well as paralogous Pat1b proteins. Here we characterize Pat1 proteins, which have no readily discernable sequence features, in Xenopus oocytes, eggs, and early embryos and in human tissue culture cells. xPat1a and 1b have essentially mutually exclusive expression patterns in oogenesis and embryogenesis. xPat1a is degraded during meiotic maturation, via PEST-like regions, while xPat1b mRNA is translationally activated at GVBD by cytoplasmic polyadenylation. Pat1 proteins bind RNA in vitro, via a central domain, with a preference for G-rich sequences, including the NRAS 5′ UTR G-quadruplex-forming sequence. When tethered to reporter mRNA, both Pat proteins repress translation in oocytes. Indeed, both epitope-tagged proteins interact with the same components of the CPEB RNP complex, including CPEB, Xp54, eIF4E1b, Rap55B, and ePAB. However, examining endogenous protein interactions, we find that in oocytes only xPat1a is a bona fide component of the CPEB RNP, and that xPat1b resides in a separate large complex. In tissue culture cells, hPat1b localizes to P-bodies, while mPat1a-GFP is either found weakly in P-bodies or disperses P-bodies in a dominant-negative fashion. Altogether we conclude that Pat1a and Pat1b proteins have distinct functions, mediated in separate complexes. Pat1a is a translational repressor in oocytes in a CPEB-containing complex, and Pat1b is a component of P-bodies in somatic cells. 相似文献