全文获取类型
收费全文 | 1272篇 |
免费 | 93篇 |
专业分类
1365篇 |
出版年
2023年 | 5篇 |
2022年 | 20篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 25篇 |
2018年 | 32篇 |
2017年 | 19篇 |
2016年 | 29篇 |
2015年 | 54篇 |
2014年 | 57篇 |
2013年 | 67篇 |
2012年 | 97篇 |
2011年 | 103篇 |
2010年 | 48篇 |
2009年 | 54篇 |
2008年 | 83篇 |
2007年 | 96篇 |
2006年 | 62篇 |
2005年 | 54篇 |
2004年 | 64篇 |
2003年 | 54篇 |
2002年 | 46篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 17篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 14篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1971年 | 8篇 |
1969年 | 3篇 |
1967年 | 3篇 |
1966年 | 5篇 |
排序方式: 共有1365条查询结果,搜索用时 15 毫秒
41.
42.
Akagi T Kamei D Tsuchiya N Nishina Y Horiguchi H Matsui M Kamma H Yamada M 《Gene》2000,245(2):267-273
The human DNA- and RNA-binding protein JKTBP is a new member of heterogeneous nuclear ribonucleoproteins (hnRNPs) that are involved in mRNA biogenesis. We cloned and characterized a mouse homolog and studied its expression in mouse tissues. The cDNA encoded a 301-residue polypeptide. There is only a single amino acid difference between the mouse and human sequences. Northern blotting indicated ubiquitous but varied expressions of approximately 1.4 and 2.8kb mRNAs in various tissues. Immunoblotting indicated that the amounts of protein of about 38kDa were higher in the brain and testis than in other tissues. An additional protein of about 53kDa was found in the brain and testis. Germ cell-deficient W/W(v) mutant mice and aged mice had the reduced amounts of JKTBP in the testes. Immunohistochemical staining indicated cell type-specific expression of JKTBP in tissues: neurons and spermatocytes displayed strong signal intensities. The signals were confined to the nucleus. The amount of 38kDa JKTBP was estimated to be approximately 1.3x10(7) molecules per HL-60 cell. These results indicate that JKTBP is an abundant, highly conserved nuclear protein. 相似文献
43.
44.
Homeotic transformation of stamens into pistil-like structures (called pistillody) has been reported in cytoplasmic substitution (alloplasmic) lines of bread wheat (Triticum aestivum) having the cytoplasm of a wild relative species, Aegilops crassa. Our previous studies indicated that pistillody is caused by alterations of the class B MADS-box gene expression pattern associated with mitochondrial gene(s) in the Ae. crassa cytoplasm. To elucidate the nuclear gene involved in the cross-talk between pistillody-related mitochondrial gene(s) and nuclear homeotic genes, we performed cDNA subtraction analysis using cDNAs derived from young spikes of a pistillody line and a normal line. As a result, we identified a protein kinase gene, WPPK1 (wheat pistillody-related protein kinase 1), which is upregulated in the young spikes of the pistillody line. RT-PCR analysis indicated that WPPK1 is strongly expressed in pistils and pistil-like stamens in the pistillody line, suggesting that it is involved in the formation of pistil-like stamens as well as pistils. The full-length cDNA sequence for WPPK1 showed high similarity with a flowering plant PVPK-1 protein kinase, and phylogenetic analysis indicated that it is a member of AGC group protein kinases. Furthermore, a phosphorylation assay indicated that it has protein kinase activity. In situ hybridization analysis revealed that WPPK1 is expressed in developing pistils and pistil-like stamens as well as in their primordia. These indicate that in the alloplasmic line, WPPK1 plays a role in formation and development of pistil-like stamens. 相似文献
45.
In most dicotyledonous plants, leaf pavement cells exhibit complex jigsaw puzzle-like cell morphogenesis during leaf expansion. Although detailed molecular biological information and mathematical modeling of this jigsaw puzzle-like cell morphogenesis are now available, a full understanding of this process remains elusive. Recent reports have highlighted the importance of three-dimensional (3D) structures (i.e., anticlinal and periclinal cell wall) in understanding the mechanical models that describe this morphogenetic process. We believe that it is important to acquire 3D shapes of pavement cells over time, i.e., acquire and analyze four-dimensional (4D) information when studying the relationship between mechanical modeling and simulations and the actual cell shape. In this report, we have developed a framework to capture and analyze 4D morphological information of Arabidopsis thaliana cotyledon pavement cells by using both direct water immersion observations and computational image analyses, including segmentation, surface modeling, virtual reality and morphometry. The 4D cell models allowed us to perform time-lapse 3D morphometrical analysis, providing detailed quantitative information about changes in cell growth rate and shape, with cellular complexity observed to increase during cell growth. The framework should enable analysis of various phenotypes (e.g., mutants) in greater detail, especially in the 3D deformation of the cotyledon surface, and evaluation of theoretical models that describe pavement cell morphogenesis using computational simulations. Additionally, our accurate and high-throughput acquisition of growing cell structures should be suitable for use in generating in silico model cell structures. 相似文献
46.
Y Inoue H Itoh M Aoki S Ogawa T Yamane T Baba N Tachibana M Kohno Y Oishi K Kobayashi-Hattori 《Bioscience, biotechnology, and biochemistry》2012,76(8):1549-1551
Two weeks of feeding soy peptides containing 2% collagen peptides increased the levels of type I and III tropocollagen and their mRNAs. In contrast, the diet did not increase the mRNA levels of rat hyaluronan synthases, serine palmitoyltransferase (the rate-limiting enzyme of ceramide synthesis), and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase (the key enzyme of cholesterol synthesis). These results suggest that feeding of soy peptides with collagen peptides specifically enhanced the tropocollagen level in the skin. 相似文献
47.
Tanaka M Machida Y Nishikawa Y Akagi T Morishima I Hashikawa T Fujisawa T Nukina N 《Biochemistry》2002,41(32):10277-10286
To examine the effects of aggregation-inducing motifs related to neurodegenerative diseases on amyloid formation of host protein, we prepared several chimera myoglobins, in which various aggregation-inducing motifs were inserted. The focused aggregation-inducing motifs included five (R5) or two (R2) oligopeptide repeats in yeast Sup35p, five octapeptide repeats (OPR) in the human prion protein, a nonamyloid beta component (NAC) in alpha-synuclein, and tandem repeats of 50 glutamines (Q50). Circular dichroism and infrared spectroscopies suggested that the OPR, R5, and Q50 motifs formed an antiparallel beta sheet as well as a random coil, whereas the R2 and NAC motifs mainly formed random coils. The OPR, R5, and Q50 mutants, but not the R2 and NAC mutants, readily formed the SDS-resistant aggregates under physiological condition, and electron microscopy revealed that the aggregates contained amyloid fibrils. The destabilization and increase in gyration radius of the OPR, R5, and Q50 mutants correlated with the tendency to form amyloid fibrils. A control mutant bearing a nonamyloidgenic sequence was also moderately destabilized but did not form amyloid fibrils. Therefore, we concluded that the OPR, R5, and Q50 motifs, even in a quite stable protein such as myoglobin, led the host protein to formation of amyloid fibrils under physiological condition. 相似文献
48.
H. Akagi Y. Yokozeki A. Inagaki K. Mori T. Fujimura 《Molecular genetics and genomics : MGG》2001,266(3):471-480
We have isolated a new family of mobile elements, Micron, which occur within microsatellites dispersed throughout the rice (Oryza sativa) genome. The first of these segments, Micron 001, was found in a microsatellite consisting of a (TA)n sequence upstream of the rice phytochrome A (phyA) gene. PCR analysis of related rice species suggests that Micron 001 integrated into this microsatellite locus prior to the divergence of the two wild species O. rufipogon and O. barthii from a common ancestor. Micron elements are short (393-bp), possess subterminal inverted repeats and the single strands have the potential to form stable secondary structures via several internal repeats. Aside from the absence of terminal inverted repeats, these characteristics resemble those of MITEs (Miniature Inverted-Repeat Transposable Elements). We estimate that 100-200 copies of Micron-related sequences are present in the rice nuclear genome, while the chloroplast and mitochondrial genomes lack this sequence. Nineteen homologs of Micron 001 exhibited extremely high nucleotide sequence conservation (greater than 90%), suggesting a recent spread of Micron elements within the genus Oryza. Surprisingly, nucleotide sequence alignments showed that all of the Micron elements are flanked on both sides by microsatellite sequence consisting mainly of (TA)n. Twenty-three elements were mapped to seven separate chromosomes. Therefore Micron elements form a family of dispersed, highly conserved repeats. This is the first report of a transposable element that targets microsatellite loci. 相似文献
49.
Aberrant chloroplasts in transgenic rice plants expressing a high level of maize NADP-dependent malic enzyme 总被引:16,自引:0,他引:16
NADP-dependent malic enzyme (NADP-ME) is a major decarboxylating enzyme in NADP-ME-type C4 species such as maize and Flaveria. In this study, chloroplastic NADP-ME was transferred to rice (Oryza sativa L.) using a chimeric gene composed of maize NADP-ME cDNA under the control of rice light-harvesting chlorophyll-a/b-binding protein (Cab) promoter. There was a 20- to 70-fold increase in the NADP-ME activity in leaves of transgenic rice
compared to that in wild-type rice plants. Immunocytochemical studies by electron microscopy showed that maize NADP-ME was
mostly localized in chloroplasts in transgenic rice plants, and that the chloroplasts were agranal without thylakoid stacking.
Chlorophyll content and photosystem II activity were inversely correlated with the level of NADP-ME activity. These results
suggest that aberrant chloroplasts in transgenic plants may be caused by excessive NADP-ME activity. Based on these results
and the known fact that only bundle sheath cells of NADP-ME species, among all three C4 subgroups, have agranal chloroplasts, we postulate that a high level of chloroplastic NADP-ME activity could strongly affect
the development of chloroplasts.
Received: 27 January 1999 / Accepted: 20 January 2000 相似文献
50.
Sohsuke Yamada Tomoyuki Koyama Hirotsugu Noguchi Yuki Ueda Ryo Kitsuyama Hiroya Shimizu Akihide Tanimoto Ke-Yong Wang Aya Nawata Toshiyuki Nakayama Yasuyuki Sasaguri Takumi Satoh 《PloS one》2014,9(11)