全文获取类型
收费全文 | 2689篇 |
免费 | 156篇 |
专业分类
2845篇 |
出版年
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 62篇 |
2020年 | 33篇 |
2019年 | 44篇 |
2018年 | 54篇 |
2017年 | 52篇 |
2016年 | 79篇 |
2015年 | 112篇 |
2014年 | 132篇 |
2013年 | 174篇 |
2012年 | 226篇 |
2011年 | 194篇 |
2010年 | 141篇 |
2009年 | 120篇 |
2008年 | 188篇 |
2007年 | 140篇 |
2006年 | 140篇 |
2005年 | 152篇 |
2004年 | 146篇 |
2003年 | 125篇 |
2002年 | 103篇 |
2001年 | 18篇 |
2000年 | 35篇 |
1999年 | 37篇 |
1998年 | 22篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 20篇 |
1994年 | 10篇 |
1993年 | 14篇 |
1992年 | 18篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 24篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1967年 | 5篇 |
1966年 | 3篇 |
排序方式: 共有2845条查询结果,搜索用时 15 毫秒
71.
Ogino Takumi Yamaguchi Terumi Uehara Takuya Kainoh Yooichi Shimoda Masami 《Applied Entomology and Zoology》2020,55(1):115-120
Applied Entomology and Zoology - The minute pirate bug Orius sauteri (Poppius) (Heteroptera: Anthocoridae) is a major natural enemy of micro-pests and is expected to be an effective pest-control... 相似文献
72.
We sequenced nucleosomal DNA fragments of the filamentous ascomycetes Aspergillus nidulans and Aspergillus oryzae and then mapped those sequences on their genomes. We compared the GC content and nucleosome density in the exonic and intronic regions in the genes of A. nidulans and A. oryzae. Although the GC content and nucleosome density in the exonic regions tended to be higher than those in the intronic regions, the difference in the distribution of the GC content was more notable than that of the nucleosome density. Next, we compared the GC content and nucleosome density in the exonic regions of 9616 orthologous gene pairs. In both Aspergillus species, the GC content did not correlate with the nucleosome density. In addition, the Spearman's rank correlation coefficient (ρ = 0.51) between the GC content of the exonic regions of the 9616 orthologous gene pairs was higher than that (ρ = 0.31) of the nucleosome densities of A. nidulans and A. oryzae. These results strongly suggest that the GC content in the exons of the orthologous gene pairs has been conserved during evolution but the nucleosome density has varied throughout. 相似文献
73.
Hirokazu Matsumoto Yumiko Shimizu Atsuko Tanaka Takuya Nogi Ichiro Tabuchi Kenji Oyama Masaaki Taniguchi Hideyuki Mannen Shinji Sasazaki 《Molecular biology reports》2013,40(4):3231-3237
Genetic analyses have contributed to improvements of economically important traits derived from adipose tissue such as fatty acid composition in beef. Elongation of very long chain fatty acids (ELOVL) genes encode for the enzymes that play an important role in elongation of long-chain fatty acids. In this study, we aimed to discover genetic polymorphisms of ELOVL gene family in cattle populations to develop genetic markers. As a result, five synonymous mutations were detected in the coding regions of the ELOVL1, ELOVL2, ELOVL3 and ELOVL5 genes. In addition, six mutations were identified in promoter region of the ELOVL5. Two of five mutations in the promoter region of ELOVL5 were expected to alter the ELOVL5 expression and influence the economic traits, because of the high synteny of the region which was essential for activation of Elovl5 in mouse. Therefore, we performed association analysis between the genotypes and traits and our result revealed that T allele of g.-110T>C in ELOVL5 gene promoter indicated significantly thinner subcutaneous fat thickness (TT, 2.39 cm; CT, 2.35 cm) than that of C allele (CC, 2.68 cm) in a Japanese Black population. Our results suggest that the g.-110T>C is a useful genetic marker for the breeding in beef cattle. 相似文献
74.
Saori Umeki Ryoichi Suzuki Yasuo Ema Masayuki Shimojima Yorihiro Nishimura Masaru Okuda Takuya Mizuno 《Journal of cellular biochemistry》2013,114(6):1271-1285
P‐selectin glycoprotein ligand‐1 (PSGL‐1) is an adhesive molecule that is known to be a ligand for P‐selectin. An anti‐adhesive property of PSGL‐1 has not been previously reported. In this study, we show that PSGL‐1 expression is anti‐adhesive for adherent cells and we have elucidated the underlying mechanism. Overexpression of PSGL‐1 induced cell rounding and floating in HEK293T cells. Similar phenomena were demonstrated in other adherent cell lines with overexpression of PSGL‐1. PSGL‐1 overexpression inhibits access of antibodies to cell surface molecules such as integrins, HLA and CD25. Cells transfected with PSGL‐1 deletion mutants that lack a large part of the extracellular domain and chimeric construct expressing extracellular CD86 and intracellular PSGL‐1 only showed rounded morphology, but there are no floating cells. These results indicated that PSGL‐1 causes steric hindrance due to the extended structure of its extracellular domain that is highly O‐glycosylated, but intracellular domain also has some effect on cell rounding. This study implies that PSGL‐1 has Janus‐faced functions, being both adhesive and anti‐adhesive. J. Cell. Biochem. 114: 1271–1285, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
75.
Masatsugu Toyota Takuya Furuichi Masahiro Sokabe Hitoshi Tatsumi 《Plant physiology》2013,163(2):543-554
Gravity is a critical environmental factor affecting the morphology and functions of organisms on the Earth. Plants sense changes in the gravity vector (gravistimulation) and regulate their growth direction accordingly. In Arabidopsis (Arabidopsis thaliana) seedlings, gravistimulation, achieved by rotating the specimens under the ambient 1g of the Earth, is known to induce a biphasic (transient and sustained) increase in cytoplasmic calcium concentration ([Ca2+]c). However, the [Ca2+]c increase genuinely caused by gravistimulation has not been identified because gravistimulation is generally accompanied by rotation of specimens on the ground (1g), adding an additional mechanical signal to the treatment. Here, we demonstrate a gravistimulation-specific Ca2+ response in Arabidopsis seedlings by separating rotation from gravistimulation by using the microgravity (less than 10−4g) conditions provided by parabolic flights. Gravistimulation without rotating the specimen caused a sustained [Ca2+]c increase, which corresponds closely to the second sustained [Ca2+]c increase observed in ground experiments. The [Ca2+]c increases were analyzed under a variety of gravity intensities (e.g. 0.5g, 1.5g, or 2g) combined with rapid switching between hypergravity and microgravity, demonstrating that Arabidopsis seedlings possess a very rapid gravity-sensing mechanism linearly transducing a wide range of gravitational changes (0.5g–2g) into Ca2+ signals on a subsecond time scale.Calcium ion (Ca2+) functions as an intracellular second messenger in many signaling pathways in plants (White and Broadley, 2003; Hetherington and Brownlee, 2004; McAinsh and Pittman, 2009; Spalding and Harper, 2011). Endogenous and exogenous signals are spatiotemporally encoded by changing the free cytoplasmic concentration of Ca2+ ([Ca2+]c), which in turn triggers [Ca2+]c-dependent downstream signaling (Sanders et al., 2002; Dodd et al., 2010). A variety of [Ca2+]c increases induced by diverse environmental and developmental stimuli are reported, such as phytohormones (Allen et al., 2000), temperature (Plieth et al., 1999; Dodd et al., 2006), and touch (Knight et al., 1991; Monshausen et al., 2009). The [Ca2+]c increase couples each stimulus and appropriate physiological responses. In the Ca2+ signaling pathways, the stimulus-specific [Ca2+]c pattern (e.g. amplitude and oscillation) provide the critical information for cellular signaling (Scrase-Field and Knight, 2003; Dodd et al., 2010). Therefore, identification of the stimulus-specific [Ca2+]c signature is crucial for an understanding of the intracellular signaling pathways and physiological responses triggered by each stimulus, as shown in the case of cold acclimation (Knight et al., 1996; Knight and Knight, 2000).Plants often exhibit biphasic [Ca2+]c increases in response to environmental stimuli. Thus, slow cooling causes a fast [Ca2+]c transient followed by a second, extended [Ca2+]c increase in Arabidopsis (Arabidopsis thaliana; Plieth et al., 1999; Knight and Knight, 2000). The Ca2+ channel blocker lanthanum (La3+) attenuated the fast transient but not the following increase (Knight and Knight, 2000), suggesting that these two [Ca2+]c peaks have different origins. Similarly, hypoosmotic shock caused a biphasic [Ca2+]c increase in tobacco (Nicotiana tabacum) suspension-culture cells (Takahashi et al., 1997; Cessna et al., 1998). The first [Ca2+]c peak was inhibited by gadolinium (Gd3+), La3+, and the Ca2+ chelator EGTA (Takahashi et al., 1997; Cessna et al., 1998), whereas the second [Ca2+]c increase was inhibited by the intracellular Ca2+ store-depleting agent caffeine but not by EGTA (Cessna et al., 1998). The amplitude of the first [Ca2+]c peak affected the amplitude of the second increase and vice versa (Cessna et al., 1998). These results suggest that even though the two [Ca2+]c peaks originate from different Ca2+ fluxes (e.g. Ca2+ influx through the plasma membrane and Ca2+ release from subcellular stores, respectively), they are closely interrelated, showing the importance of the kinetic and pharmacological analyses of these [Ca2+]c increases.Changes in the gravity vector (gravistimulation) could work as crucial environmental stimuli in plants and are generally achieved by rotating the specimens (e.g. +180°) in ground experiments. Use of Arabidopsis seedlings expressing apoaequorin, a Ca2+-reporting photoprotein (Plieth and Trewavas, 2002; Toyota et al., 2008a), has revealed that gravistimulation induces a biphasic [Ca2+]c increase that may be involved in the sensory pathway for gravity perception/response (Pickard, 2007; Toyota and Gilroy, 2013) and the intracellular distribution of auxin transporters (Benjamins et al., 2003; Zhang et al., 2011). These two Ca2+ changes have different characteristics. The first transient [Ca2+]c increase depends on the rotational velocity but not angle, whereas the second sustained [Ca2+]c increase depends on the rotational angle but not velocity. The first [Ca2+]c transient was inhibited by Gd3+, La3+, and the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid but not by ruthenium red (RR), whereas the second sustained [Ca2+]c increase was inhibited by all these chemicals. These results suggest that the first transient and second sustained [Ca2+]c increases are related to the rotational stimulation and the gravistimulation, respectively, and are mediated by distinct molecular mechanisms (Toyota et al., 2008a). However, it has not been demonstrated directly that the second sustained [Ca2+]c increase is induced solely by gravistimulation; it could be influenced by other factors, such as an interaction with the first transient [Ca2+]c increase (Cessna et al., 1998), vibration, and/or deformation of plants during the rotation.To elucidate the genuine Ca2+ signature in response to gravistimulation in plants, we separated rotation and gravistimulation under microgravity (μg; less than 10−4g) conditions provided by parabolic flight (PF). Using this approach, we were able to apply rotation and gravistimulation to plants separately (Fig. 1). When Arabidopsis seedlings were rotated +180° under μg conditions, the [Ca2+]c response to the rotation was transient and almost totally attenuated in a few seconds. Gravistimulation (transition from μg to 1.5g) was then applied to these prerotated specimens at the terminating phase of the PF. This gravistimulation without simultaneous rotation induced a sustained [Ca2+]c increase. The kinetic properties of this sustained [Ca2+]c increase were examined under different gravity intensities (0.5g–2g) and sequences of gravity intensity changes (Fig. 2A). This analysis revealed that gravistimulation-specific Ca2+ response has an almost linear dependency on gravitational acceleration (0.5g–2g) and an extremely rapid responsiveness of less than 1 s.Open in a separate windowFigure 1.Diagram of the experimental procedures for applying separately rotation and gravistimulation to Arabidopsis seedlings. Rotatory stimulation (green arrow) was applied by rotating the seedlings 180° under μg conditions, and 1.5g 180° rotation gravistimulation (blue arrow) was applied to the prerotated seedlings after μg.Open in a separate windowFigure 2.Acceleration, temperature, humidity, and pressure in an aircraft during flight experiments. A, Accelerations along x, y, and z axes in the aircraft during PF. The direction of flight (FWD) and coordinates (x, y, and z) are indicated in the bottom graph. The inset shows an enlargement of the acceleration along the z axis (gravitational acceleration) during μg conditions lasting for approximately 20 s. B, Temperature, humidity, and pressure in the aircraft during PF. Shaded areas in graphs denote the μg condition. 相似文献
76.
77.
Chie Tomikawa Takayuki Ohira Yasushi Inoue Takuya Kawamura Akihiko Yamagishi Tsutomu Suzuki Hiroyuki Hori 《FEBS letters》2013
Thermoplasma acidophilum is a thermo-acidophilic archaeon. We purified tRNALeu (UAG) from T. acidophilum using a solid-phase DNA probe method and determined the RNA sequence after determining via nucleoside analysis and m7G-specific aniline cleavage because it has been reported that T. acidophilum tRNA contains m7G, which is generally not found in archaeal tRNAs. RNA sequencing and liquid chromatography–mass spectrometry revealed that the m7G modification exists at a novel position 49. Furthermore, we found several distinct modifications, which have not previously been found in archaeal tRNA, such as 4-thiouridine9, archaeosine13 and 5-carbamoylmethyuridine34. The related tRNA modification enzymes and their genes are discussed. 相似文献
78.
Takuya Nakajima Wakana Ara Shizuko Kagawa John E. Moore Keiko Matsubara Motoo Matsuda 《Folia microbiologica》2013,58(6):607-613
Although the absence of intervening sequences (IVSs) within the 23S rRNA genes in Campylobacter lari isolates has been described, there are apparently no reports regarding correlations between the nucleotide sequences of 23S rRNA genes and erythromycin (Ery) susceptibility in C. lari isolates. Here, we determined the minimum inhibitory concentrations of 35 C. lari isolates [n?=?19 for urease-positive thermophilic Campylobacter (UPTC); n?=?16 urease-negative (UN) C. lari] obtained from Asia, Europe, and North America. We found that the 18 isolates were resistant to the Ery (defined as ≧8 μg/mL), and three isolates, UPTC A1, UPTC 92251, and UPTC 504, showed increased resistance (16 μg/mL). No correlations between the IVSs in the helix 45 region within the 23S rRNA gene sequences and Ery resistance were identified in the C. lari isolates examined. In addition, no point mutations occurred at any expected or putative position within the V domain in the isolates. In conclusion, antibiotic resistance against the macrolide erythromycin is mediated through an alternative pathway to that described above. 相似文献
79.
Hitoshi Tamiaki Meiyun Xu Takuya Tanaka Tadashi Mizoguchi 《Bioorganic & medicinal chemistry letters》2013,23(8):2377-2379
When a pyridine solution of zinc methyl 8-vinyl-mesopyropheophorbide-a was irradiated with visible light in the presence of ethanol, ascorbic acid and diazabicylo[2.2.2]octane under nitrogen at room temperature, zinc (7R/S,8E)-8-ethylidene-bacteriochlorin was obtained via 1,4-hydrogenation. The 1,4-photoreduction is similar to the enzymatic reduction of 8-vinyl-chlorophyllides to (E)-8-ethylidene-bacteriochlorins in anoxygenic photosynthetic bacteria producing bacteriochlorophylls-b/g. The resulting zinc 8-ethylidene-bacteriochlorin was readily isomerized to the chemically more stable 8-ethyl-chlorin by further illumination. As a by-product, zinc 8-vinyl-7,8-cis-bacteriochlorin was slightly formed by photoinduced 1,2-hydrogenation of zinc 8-vinyl-chlorin. 相似文献
80.
A novel chemical tool compound that is an antagonist of brassinolide (BL, 1)-induced rice lamina joint inclination was developed. Although 2-O-, 3-O-, 22-O-, or 23-O-methylation of BL causes a critical decrease in biological activity,5 a crystal structure of the extracellular leucine-rich repeat (LRR) domain of BRASSINOSTEROID-INSENSITIVE I (BRI1) bound to BL3, 4 indicates that the loss of activity of the O-methylated BL may result from not only the low affinity to BRI1, but also from blocking the interaction with another BR signaling factor, a partner protein of BRI1 (e.g., BRI1-ASSOCIATED KINASE 1, BAK1). On the basis of this hypothesis we synthesized the BL 2,3-acetonide 2, the 22,23-acetonide 3, and the 2,3:22,23-diacetonide 4 to assess the possibility of 2-O- and 3-O- or/and 22-O- and 23-O-alkylated BL as an antagonist in BR signaling evoked by exogenously applied BL. The 2,3-acetonide 2 more strongly inhibited the lamina inclination caused by BL relative to the 22,23-acetonide 3, whereas the diacetonide 4 had no effect most likely due to its increased hydrophobicity. This suggested that the 2,3-hydroxyl groups of BL play a more significant role in the interaction with a BRI1 partner protein rather than BRI1 itself in rice lamina joint inclination. Taken together it was demonstrated that BL, the most potent agonist of BRI1, is transformed into an antagonist by functionalization of the 2,3-dihydroxyl groups as the acetonide. This finding opens the door to the potential development of a chemical tool that modulates protein–protein interactions in the BR signaling pathway to dissect the BR-dependent processes. 相似文献