全文获取类型
收费全文 | 1872篇 |
免费 | 128篇 |
专业分类
2000篇 |
出版年
2023年 | 4篇 |
2022年 | 23篇 |
2021年 | 30篇 |
2020年 | 16篇 |
2019年 | 21篇 |
2018年 | 30篇 |
2017年 | 12篇 |
2016年 | 51篇 |
2015年 | 99篇 |
2014年 | 94篇 |
2013年 | 112篇 |
2012年 | 154篇 |
2011年 | 159篇 |
2010年 | 102篇 |
2009年 | 84篇 |
2008年 | 85篇 |
2007年 | 103篇 |
2006年 | 79篇 |
2005年 | 86篇 |
2004年 | 108篇 |
2003年 | 78篇 |
2002年 | 83篇 |
2001年 | 49篇 |
2000年 | 44篇 |
1999年 | 41篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 12篇 |
1992年 | 20篇 |
1991年 | 17篇 |
1990年 | 12篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 10篇 |
1974年 | 4篇 |
1972年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有2000条查询结果,搜索用时 11 毫秒
71.
AMP-activated protein kinase (AMPK) is known as an important cellular energy sensor, but its in vivo role has not been fully understood. Recent studies provided surprising results that AMPK regulates cell polarity and mitosis under the control of tumour suppressor LKB1. Moreover, these newly found in vivo functions of AMPK are regulated by energy status in a cell autonomous manner. These findings provide novel insights into the physiological function of AMPK and the treatment of AMPK-related diseases such as cancer and diabetes. 相似文献
72.
Major linear antibody epitopes and capsid proteins differentially induce protective immunity against Theiler's virus-induced demyelinating disease. 总被引:1,自引:0,他引:1 下载免费PDF全文
Theiler's murine encephalomyelitis virus-induced immunologically mediated demyelinating disease (TMEV-IDD) in susceptible mice provides a relevant infectious model for multiple sclerosis. Previously, we have identified six major linear antibody epitopes on the viral capsid proteins. In this study, we utilized fusion proteins containing individual capsid proteins and synthetic peptides containing the linear antibody epitopes to determine the potential role of antibody response in the course of virus-induced demyelination. Preimmunization of susceptible mice with VPI and VP2 fusion proteins, but not VP3, resulted in the protection from subsequent development of TMEV-IDD. Mice free of clinical symptoms following preimmunizations with fusion proteins displayed high levels of antibodies to the capsid proteins corresponding to the immunogens. In contrast, the level of antibodies to a particular linear epitope, A1C (VP1(262-276)), capable of efficiently neutralizing virus in vitro increased with the progression of disease. Further immunization with synthetic peptides containing individual antibody epitopes indicated that antibodies to the epitopes are differentially effective in protecting from virus-induced demyelination. Taken together, these results suggest that antibodies to only certain linear epitopes are protective and such protection may be restricted during the early stages of viral infection. 相似文献
73.
Nguyen Phuong Thao Le Duc Dat Ninh Thi Ngoc Vu Anh Tu Tran Thi Hong Hanh Phan Thi Thanh Huong Nguyen Xuan Nhiem Bui Huu Tai Nguyen Xuan Cuong Nguyen Hoai Nam Pham Van Cuong Seo Young Yang Sohyun Kim Doobyeong Chae Young-Sang Koh Phan Van Kiem Chau Van Minh Young Ho Kim 《Bioorganic & medicinal chemistry letters》2013,23(6):1823-1827
Three new pyrrole oligoglycosides, astebatheriosides A–C (1–3), and a new furan oligoglycoside, astebatherioside D (4), were isolated from the starfish Asterina batheri by various chromatographic methods. Their structures were elucidated by spectroscopic and chemical methods. Compounds 2, 3, and 4 moderately inhibited IL-12 p40 production in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells (BMDCs) with IC50 values of 36.4, 31.6, and 22.8 μM, respectively. 相似文献
74.
A novel platelet aggregation inhibitor, sal-C, was purified to homogeneity from the venom of Korean snake (Agkistrodon halys brevicaudus). Several lines of experimental evidence clearly indicated that sal-C inhibits not only the collagen-induced platelet aggregation, but also the aggregation mediated by the cell surface glycoprotein IIb-IIIa (GP IIb-IIIa). We have isolated the cDNA encoding sal-C from the cDNA library of the snake venom gland and analyzed its complete nucleotide sequence. Sal-C is a single-chain polypeptide composed of 212 amino acids including 24 cysteines. The deduced polypeptide sequence of sal-C demonstrated considerable homology to previously described protein species of the collagen-induced platelet aggregation inhibitor family. Sal-C does not have the Arg-Gly-Asp (RGD) motif, but contains the Ser-Glu-Cys-Asp sequence. Interestingly, sal-C was found to inhibit GP IIb-IIIa binding to immobilized fibrinogen which is antagonized by the typical RGD motif of disintegrins. 相似文献
75.
Robert R. Dunn Nyeema C. Harris Robert K. Colwell Lian Pin Koh Navjot S. Sodhi 《Proceedings. Biological sciences / The Royal Society》2009,276(1670):3037-3045
The effects of species declines and extinction on biotic interactions remain poorly understood. The loss of a species is expected to result in the loss of other species that depend on it (coextinction), leading to cascading effects across trophic levels. Such effects are likely to be most severe in mutualistic and parasitic interactions. Indeed, models suggest that coextinction may be the most common form of biodiversity loss. Paradoxically, few historical or contemporary coextinction events have actually been recorded. We review the current knowledge of coextinction by: (i) considering plausible explanations for the discrepancy between predicted and observed coextinction rates; (ii) exploring the potential consequences of coextinctions; (iii) discussing the interactions and synergies between coextinction and other drivers of species loss, particularly climate change; and (iv) suggesting the way forward for understanding the phenomenon of coextinction, which may well be the most insidious threat to global biodiversity. 相似文献
76.
Ki Jin Park Kyu Jin Sa Byeong Wan Kim Hee-Jong Koh Ju Kyong Lee 《Genes & genomics.》2014,36(2):179-189
We constructed a framework map using SSR markers in the F2 population derived from a cross between a waxy corn inbred line and a sweet corn inbred line. We constructed a genetic linkage map of the F2:3 population employing 295 SSR markers on 158 F2 individuals produced from the cross. The map comprised a total genomic length of 2,626.5 cM in 10 linkage groups and an average distance between markers of 8.9 cM. The number of loci per linkage group ranged from 27 (chr. 5) to 34 (chr. 7). The genetic distance per linkage group ranged from 213.6 cM (chr. 10) to 360.6 cM (chr. 2). Χ 2 tests revealed that 254 markers (86.1 %) distributed over all 10 chromosomes exhibited a Mendelian segregation ratio of 1:2:1. A total of 14 quantitative trait loci (QTLs) for days to silking (DTS), plant height (PH), ear height (EH), ear height ratio (ER), ear length (L-ear), and setted ear length (L-sear) were found in the 158 F2 progeny. They were mapped to chromosomes 1, 2, 3, 7, 8, and 10. Among them, one QTL was associated with DTS, three with PH, six with EH, one with ER, two with L-ear, and one QTL was related to L-sear. In our study, we found that four QTLs: qDTS1, qEH1a, qEH1b, and qPH1, were clustered between umc2390 and umc1603 on chromosome 1. These new QTLs identified by the present study could serve as useful molecular markers in selecting for yield and agronomic traits in maize. The results of this study may improve the identification and characterization of genes responsible for yield and agronomic traits in waxy corn and sweet corn. 相似文献
77.
Wang Y Kim JA Cheong YH Joshi Y Koh YJ Hur JS 《Journal of microbiology (Seoul, Korea)》2011,49(3):473-480
The reducing polyketide synthases found in filamentous fungi are involved in the biosynthesis of many drugs and toxins. Lichens
produce bioactive polyketides, but the roles of reducing polyketide synthases in lichens remain to be clearly elucidated.
In this study, a reducing polyketide synthase gene (U1PKS3) was isolated and characterized from a cultured mycobiont of Usnea longissima. Complete sequence information regarding U1PKS3 (6,519 bp) was obtained by screening a fosmid genomic library. A U1PKS3 sequence
analysis suggested that it contains features of a reducing fungal type I polyketide synthase with β-ketoacyl synthase (KS),
acyltransferase (AT), dehydratase (DH), enoyl reductase (ER), ketoacyl reducatse (KR), and acyl carrier protein (ACP) domains.
This domain structure was similar to the structure of ccRadsl, which is known to be involved in resorcylic acid lactone biosynthesis
in Chaetomium chiversii. The results of phylogenetic analysis located U1PKS3 in the clade of reducing polyketide synthases. RT-PCR analysis results
demonstrated that UIPKS3 had six intervening introns and that UIPKS3 expression was upregulated by glucose, sorbitol, inositol, and mannitol. 相似文献
78.
The hypoxia-inducible factor-1 (HIF-1) is the master regulator of the cellular response to hypoxia and its expression levels are tightly controlled through synthesis and degradation. It is widely accepted that HIF-1alpha protein accumulation during hypoxia results from inhibition of its oxygen-dependent degradation by the von Hippel Lindau protein (pVHL) pathway. However, recent data describe new pVHL- or oxygen-independent mechanisms for HIF-1alpha degradation. Furthermore, the hypoxia-induced increase in HIF-1alpha levels is facilitated by the continued translation of HIF-1alpha during hypoxia despite the global inhibition of protein translation. Recent work has contributed to an increased understanding of the mechanisms that control the translation and degradation of HIF-1alpha under both normoxic and hypoxic conditions. 相似文献
79.
80.
Analysis of recombinant DNA clones of the endogenous BALB/c murine leukemia virus WN1802N: variation in long terminal repeat length 总被引:1,自引:4,他引:1 下载免费PDF全文
L R Boone F E Myer D M Yang J O Kiggans C Koh R W Tennant W K Yang 《Journal of virology》1983,45(1):484-488
We analyzed 15 recombinant DNA clones of the unintegrated closed circular DNA intermediate of the BALB/c endogenous ecotropic murine leukemia virus WN1802N. Thirteen of these clones had an insert which corresponded to the complete murine leukemia virus genome. Of these, six contained a single long terminal repeat (LTR) and seven contained two LTRs. The viral genomes in nine clones had an LTR of 520 base pairs (bp), one had an LTR of 570 bp, three had an LTR of 600 bp, and one had an LTR of 670 bp. Restriction endonuclease analysis demonstrated that the size variability resides in the U3 region. Seven of eight clones which yielded infectious virus by DNA transfection had the 520-bp LTR, and the other had a 600-bp LTR. More detailed examination of plasmid subclones of three isolates with different-sized LTRs revealed that the approximate position which varies in the U3 region corresponds to the 72-bp repeat region of Moloney sarcoma virus. Possible consequences of these variations are discussed. 相似文献