全文获取类型
收费全文 | 2622篇 |
免费 | 189篇 |
专业分类
2811篇 |
出版年
2022年 | 16篇 |
2021年 | 33篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 37篇 |
2017年 | 21篇 |
2016年 | 43篇 |
2015年 | 83篇 |
2014年 | 91篇 |
2013年 | 133篇 |
2012年 | 130篇 |
2011年 | 140篇 |
2010年 | 78篇 |
2009年 | 80篇 |
2008年 | 120篇 |
2007年 | 124篇 |
2006年 | 136篇 |
2005年 | 134篇 |
2004年 | 116篇 |
2003年 | 123篇 |
2002年 | 136篇 |
2001年 | 91篇 |
2000年 | 104篇 |
1999年 | 82篇 |
1998年 | 47篇 |
1997年 | 24篇 |
1996年 | 28篇 |
1995年 | 27篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 37篇 |
1991年 | 41篇 |
1990年 | 55篇 |
1989年 | 34篇 |
1988年 | 41篇 |
1987年 | 43篇 |
1986年 | 35篇 |
1985年 | 38篇 |
1984年 | 20篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 24篇 |
1976年 | 14篇 |
1974年 | 12篇 |
1973年 | 17篇 |
1971年 | 10篇 |
排序方式: 共有2811条查询结果,搜索用时 15 毫秒
971.
Ishiwata Sho Iizuka Haku Sonoda Hiroyuki Tsunoda Daisuke Tajika Yuki Chikuda Hirotaka Koibuchi Noriyuki Shimokawa Noriaki 《Molecular and cellular biochemistry》2020,465(1-2):53-64
Molecular and Cellular Biochemistry - IRE1 is the most conserved endoplasmic reticulum (ER)-resident stress sensor. Its activation not only splices XBP1 but also participates in a variety of cell... 相似文献
972.
Wolbachia, cytoplasmically inherited endosymbionts of arthropods, are known to hijack their host reproduction in various ways to increase their own vertical transmission. This may lead to the selective sweep of associated mitochondria, which can have a large impact on the evolution of mitochondrial lineages. In Japan, two different Wolbacahia strains (wCI and wFem) are found in two sister species of pierid butterflies, Eurema mandarina and Eurema hecabe. In both species, females infected with wCI (C females) produce offspring with a nearly 1:1 sex ratio, while females infected with both wCI and wFem (CF females) produce all‐female offspring. Previous studies have suggested the historical occurrence of hybrid introgression in C individuals between the two species. Furthermore, hybrid introgression in CF individuals is suggested by the distinct mitochondrial lineages between C females and CF females of E. mandarina. In this study, we performed phylogenetic analyses based on nuclear DNA and mitochondrial DNA markers of E. hecabe with previously published data on E. mandarina. We found that the nuclear DNA of this species significantly diverged from that of E. mandarina. By contrast, mitochondrial DNA haplotypes comprised two clades, mostly reflecting Wolbachia infection status rather than the individual species. Collectively, our results support the previously suggested occurrence of two independent historical events wherein the cytoplasms of CF females and C females moved between E. hecabe and E. mandarina through hybrid introgression. 相似文献
973.
Kaori?Yoneyama Xiaonan?Xie Takaya?Kisugi Takahito?Nomura Hitoshi?Sekimoto Takao?Yokota Koichi?YoneyamaEmail author 《Plant Growth Regulation》2011,65(3):495-504
Strigolactones (SLs), originally characterized as germination stimulants for root parasitic weeds, are now recognized as hyphal
branching factors for symbiotic arbuscular mycorrhizal fungi and as a novel class of plant hormones inhibiting shoot branching.
In the present study, SLs in root exudates of 13 Asteraceae plants including crops, a weed, and ornamental plants were characterized.
High performance liquid chromatography/tandem mass spectrometry (LC–MS/MS) analyses revealed that all the Asteraceae plants
examined exuded known SLs and, except for sunflower (Helianthus annuus), high germination stimulant activities at retention times corresponding to these SLs were confirmed. The two major SLs exuded
by these Asteraceae plants were orobanchyl acetate and orobanchol. 5-Deoxystrigol and 7-hydroxyorobanchyl acetate were detected
in root exudates from several Asteraceae species examined in this study. 相似文献
974.
Uchida S Hara K Kobayashi A Otsuki K Yamagata H Hobara T Suzuki T Miyata N Watanabe Y 《Neuron》2011,69(2):359-372
Stressful events during adulthood are potent adverse environmental factors that can predispose individuals to psychiatric disorders, including depression; however, many individuals exposed to stressful events can adapt and function normally. While stress vulnerability may influence depression, the molecular mechanisms underlying the susceptibility and adaptation to chronic stress within the brain are poorly understood. In this study, two genetically distinct mouse strains that exhibit different behavioral responses to chronic stress were used to demonstrate how the differential epigenetic status of the glial cell-derived neurotrophic factor (Gdnf) gene in the ventral striatum modulates susceptibility and adaptation to chronic stress. Our results suggest that the histone modifications and DNA methylation of the Gdnf promoter have crucial roles in the control of behavioral responses to chronic stress. Our data provide insights into these mechanisms, suggesting that epigenetic modifications of Gdnf, along with genetic and environmental factors, contribute to behavioral responses to stress. 相似文献
975.
Tashiro Y Inagaki A Shimizu M Ichikawa S Takaya N Nakajima-Kambe T Uchiyama H Nomura N 《Bioscience, biotechnology, and biochemistry》2011,75(3):605-607
Many Gram-negative bacteria release membrane vesicles (MVs), but their phospholipid properties are poorly understood. Phosphatidylglycerol was present at high levels in MVs derived from Pseudomonas aeruginosa, but not in the cellular outer membrane. The ratio of stearic acid in MVs was high compared to that in the cellular outer membrane. These findings suggest that membrane rigidity is associated with MV biogenesis. 相似文献
976.
Invasive exotic ants often have a mutualistic relationship with other insects excreting honeydew, and this is considered to
play a key role in their invasion success. We investigated the multispecies association patterns between ants and hemipteran
insects in the Yanbaru forests, Okinawa, Japan, an Asian biodiversity hotspot. We especially focused on roadside environments,
which are the frontlines of invasion for exotic ants. We found that only a small number of herbaceous and pioneer plants were
predominant on the roadsides. Four honeydew producers, Melanaphis formosana, Dysmicoccus sp. A, Heteropsylla cubana, and Sogata hakonensis, living on these roadside plants accounted for 94.9% of the total honeydew-producer aggregations observed. Only a few exotic
ants, such as Technomyrmex brunneus and Anoplolepis gracilipes, were observed with these honeydew-producer aggregations, and densities of these ants and honeydew producers were often
positively correlated. An ant exclusion experiment showed that exotic ant occurrence improved the survival of some of the
hemipteran colonies. Interestingly, the abundance of native ants was not correlated with the abundance of honeydew producers,
and the local density of Pheidole noda was negatively correlated with that of M. formosana. These findings, i.e., only a few ants, all exotic, tended to hemipteran honeydew producers despite the existence of many
native ants, and the abundances of those exotic ants and those hemipteran insects had positive correlations, provide some
insights into the mechanism of biological invasion and provide information for the management of exotic ants. 相似文献
977.
Eggerthella sp. strain YY7918 was isolated from the intestinal flora of a healthy human. It metabolizes daidzein (a soybean isoflavonoid) and produces S-equol, which has stronger estrogenic activities than daidzein. Here, we report the finished and annotated genomic sequence of this organism. 相似文献
978.
Iwamori M Sakai A Minamimoto N Iwamori Y Tanaka K Aoki D Adachi S Nomura T 《Journal of biochemistry》2011,150(5):515-523
Anti-Lactobacillus johnsonii (LJ) antisera generated by immunization of rabbits with LJ reacted with glyceroglycolipids in LJ, i.e. dihexaosyl diacylglycerol (DH-DG), trihexaosyl DG (TH-DG) and tetrahexaosyl DG (TetH-DG), whose reactivities with antisera increased proportionally with longer carbohydrate chains of glycolipids. Structural analyses of glycolipids from LJ revealed that DH-DG was Galα1-2Glcα1-3'DG, and TH-DG and TetH-DG were novel derivatives of it with α-Gal at the non-reducing terminal, i.e. Galα1-6Galα1-2Glcα1-3'DG and Galα1-6Galα1-6Galα1-2Glcα1-3'DG, respectively. DH-DG was commonly present in several lactobacilli examined, but TetH-DG was restricted to LJ, L. intestinalis and L. reuteri, while the TH-DGs from L. casei were Glc1-6Galα1-2Glcα1-3'DG and an esterified derivative of it, Glc1-6Galα1-2Glc(6-fatty acid)α1-3'DG, as reported in the literature. Anti-LJ antisera reacted with TH-DG and esterified TH-DG from L. casei to lesser extents, but not at all with gentibiosyl DG from Staphylococcus epidermidis or kojibiosyl DG from Streptococcus salivalis or sphingoglycolipids containing α-Gal residues. The major molecular species of glycolipids obtained from lactobacilli were 11-octadecenoic and 11,12-methylene-octadecanoic acids-containing ones. Also, human IgM antibodies against TH-DG and TetH-DG from LJ were detected in human sera, with various antibody titres, indicating that an immune reaction to symbiotic lactobacilli occurs against their glycolipid antigens, TH-DG and TetH-DG. 相似文献
979.
Tajima H Imada K Sakuma M Hattori F Nara T Kamo N Homma M Kawagishi I 《The Journal of biological chemistry》2011,286(49):42200-42210
Escherichia coli has closely related amino acid chemoreceptors with distinct ligand specificity, Tar for l-aspartate and Tsr for l-serine. Crystallography of the ligand-binding domain of Tar identified the residues interacting with aspartate, most of which are conserved in Tsr. However, swapping of the nonconserved residues between Tsr and Tar did not change ligand specificity. Analyses with chimeric receptors led us to hypothesize that distinct three-dimensional arrangements of the conserved ligand-binding residues are responsible for ligand specificity. To test this hypothesis, the structures of the apo- and serine-binding forms of the ligand-binding domain of Tsr were determined at 1.95 and 2.5 Å resolutions, respectively. Some of the Tsr residues are arranged differently from the corresponding aspartate-binding residues of Tar to form a high affinity serine-binding pocket. The ligand-binding pocket of Tsr was surrounded by negatively charged residues, which presumably exclude negatively charged aspartate molecules. We propose that all these Tsr- and Tar-specific features contribute to specific recognition of serine and aspartate with the arrangement of the side chain of residue 68 (Asn in Tsr and Ser in Tar) being the most critical. 相似文献
980.
Ozaki Y Matsui H Nagamachi A Asou H Aki D Inaba T 《The Journal of biological chemistry》2011,286(7):5589-5598
The dynactin complex is required for activation of the dynein motor complex, which plays a critical role in various cell functions including mitosis. During metaphase, the dynein-dynactin complex removes spindle checkpoint proteins from kinetochores to facilitate the transition to anaphase. Three components (p150(Glued), dynamitin, and p24) compose a key portion of the dynactin complex, termed the projecting arm. To investigate the roles of the dynactin complex in mitosis, we used RNA interference to down-regulate p24 and p150(Glued) in human cells. In response to p24 down-regulation, we observed cells with delayed metaphase in which chromosomes frequently align abnormally to resemble a "figure eight," resulting in cell death. We attribute the figure eight chromosome alignment to impaired metaphasic centrosomes that lack spindle tension. Like p24, RNA interference of p150(Glued) also induces prometaphase and metaphase delays; however, most of these cells eventually enter anaphase and complete mitosis. Our findings suggest that although both p24 and p150(Glued) components of the dynactin complex contribute to mitotic progression, p24 also appears to play a role in metaphase centrosome integrity, helping to ensure the transition to anaphase. 相似文献