全文获取类型
收费全文 | 906篇 |
免费 | 52篇 |
专业分类
958篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 20篇 |
2016年 | 11篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 44篇 |
2012年 | 36篇 |
2011年 | 50篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 51篇 |
2007年 | 54篇 |
2006年 | 47篇 |
2005年 | 68篇 |
2004年 | 56篇 |
2003年 | 43篇 |
2002年 | 38篇 |
2001年 | 23篇 |
2000年 | 28篇 |
1999年 | 16篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 5篇 |
1984年 | 13篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 6篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1965年 | 7篇 |
排序方式: 共有958条查询结果,搜索用时 0 毫秒
71.
The purpose of this study is to investigate the effect of Cr deficiency on the rat retina. Three-week-old Wistar Kyoto rats were divided into 2 groups. Cr-deficient rats were fed AIN-93G diet without Cr and deionized distilled water. Control rats were fed AIN-93G diet and deionized distilled water. The Cr and sugar concentrations in the whole blood and cholesterol concentration in the serum were measured. We observed the retina with an electron microscope, and counted phagocytized lamellar structures in the retinal pigment epithelium (RPE) before and after the start of light exposure on negative electron microscopic films. The whole blood Cr level of Cr-deficient rats was less than 0.2 microg/l. The blood sugar level of Cr-deficient rats was significantly higher than that of normal rats (p < 0.05). There were significantly more phagocytized lamellar structures in the RPE of Cr-deficient rats 1, 2, 7, 11 and 12 h after the start of light exposure than in that of normal rats (p < 0.05). However, no morphological abnormalities were found in the photoreceptor cells of Cr-deficient rats. Phagocytosis in the photoreceptor outer segment discs in the RPE was accelerated, but the pattern of the retinal circadian rhythm with maximum phagocytosis 2 h after exposure to light was unchanged. The Cr-deficient state may cause the membrane to degenerate, and phagocytosis of the photoreceptor outer segment discs in the RPE may be accelerated. This study provided an evidence of the nutritional importance of Cr in rat retina. 相似文献
72.
Hashimoto T Wakabayashi T Watanabe A Kowa H Hosoda R Nakamura A Kanazawa I Arai T Takio K Mann DM Iwatsubo T 《The EMBO journal》2002,21(7):1524-1534
We raised monoclonal antibodies against senile plaque (SP) amyloid and obtained a clone 9D2, which labeled amyloid fibrils in SPs and reacted with approximately 50/100 kDa polypeptides in Alzheimer's disease (AD) brains. We purified the 9D2 antigens and cloned a cDNA encoding its precursor, which was a novel type II transmembrane protein specifically expressed in neurons. This precursor harbored three collagen-like Gly-X-Y repeat motifs and was partially homologous to collagen type XIII. Thus, we named the 9D2 antigen as CLAC (collagen-like Alzheimer amyloid plaque component), and its precursor as CLAC-P/collagen type XXV. The extracellular domain of CLAC-P/collagen type XXV was secreted by furin convertase, and the N-terminus of CLAC deposited in AD brains was pyroglutamate modified. Both secreted and membrane-tethered forms of CLAC-P/collagen type XXV specifically bound to fibrillized Abeta, implicating these proteins in beta-amyloidogenesis and neuronal degeneration in AD. 相似文献
73.
Nakamura N Miyake Y Matsushita M Tanaka S Inoue H Kanazawa H 《Journal of biochemistry》2002,132(3):483-491
Kinesin family proteins are microtubule-dependent molecular motors involved in the intracellular motile process. Using a Ca2+ -binding protein, CHP (calcineurin B homologous protein), as a bait for yeast two hybrid screening, we identified a novel kinesin-related protein, KIF1Bbeta2. KIF1Bbeta2 is a member of the KIF1 subfamily of kinesin-related proteins, and consists of an amino terminal KIF1B-type motor domain followed by a tail region highly similar to that of KIF1A. CHP binds to regions adjacent to the motor domains of KIF1Bbeta2 and KIF1B, but not to those of the other KIF1 family members, KIF1A and KIF1C. Immunostaining of neuronal cells showed that a significant portion of KIF1Bbeta2 is co-localized with synaptophysin, a marker protein for synaptic vesicles, but not with a mitochondria-staining dye. Subcellular fractionation analysis indicated the co-localization of KIF1Bbeta2 with synaptophysin. These results suggest that KIF1Bbeta2, a novel CHP-interacting molecular motor, mediates the transport of synaptic vesicles in neuronal cells. 相似文献
74.
Hashimoto T Nonaka Y Minato K Kawakami S Mizuno M Fukuda I Kanazawa K Ashida H 《Bioscience, biotechnology, and biochemistry》2002,66(7):1610-1614
To investigate the effects of lentinan from Lentinas edodes and polysaccharides from Agaricus blazei (ABPS) on the expression of cytochrome P450s (CYPs), lentinan (10 mg/kg/day) or ABPS (200 mg/kg/day) was administered to female BALB/c mice four times every other day by intraperitoneal injection. Lentinan and ABPS suppressed both the constitutive and 3-methylcholanthrene-induced CYP1A expression and ethoxyresorufin-O-deethylation activity in the liver. 相似文献
75.
The photosynthetic electron transfer chain generates proton motive force (pmf), composed of both electric field (Deltapsi) and concentration (DeltapH) gradients. Both components can drive ATP synthesis, whereas the DeltapH component alone can trigger feedback regulation of the antenna. It has often been suggested that a relatively large pmf is needed to sustain the energetic contributions of the ATP synthase reaction (DeltaG(ATP)), and that the Deltapsi component is dissipated during illumination, leading to an acidic lumen in the light. We suggest that this is incompatible with the stabilities of lumenal components and the observed activation of downregulation. Recent work on the chloroplast ATP synthase suggests that a more moderate pmf can sustain DeltaG(ATP). In addition, in vivo probes suggest that a substantial fraction of pmf can be stored as Deltapsi. Together, these factors should allow sufficient DeltaG(ATP) to maintain lumen pH in a range where lumenal enzyme activities are nearly optimal, and where the level of NPQ is regulated. 相似文献
76.
Soybean germplasm pools in Asia revealed by nuclear SSRs 总被引:20,自引:0,他引:20
Abe J Xu DH Suzuki Y Kanazawa A Shimamoto Y 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2003,106(3):445-453
Soybean was domesticated in East Asia, where various kinds of landraces have been established as a result of adaptation to different environments and the diversification of food cultures. Asia is thus an important germplasm pool of soybean. In order to evaluate the genetic structure of the Asian soybean population, we analyzed allelic profiles at 20 simple-sequence repeat (SSR) loci of 131 accessions introduced from 14 Asian countries. The SSR loci produced an average of 11.9 alleles and a mean gene diversity of 0.782 in the accessions tested. Quantification theory III analysis and cluster analysis with the UPGMA method clearly separated the Japanese from the Chinese accessions, suggesting that the Japanese and Chinese populations formed different germplasm pools. The Korean accessions were involved in both germplasm pools, whereas most of the accessions from southeast and south/central Asia were derived from the Chinese pool. Relatively high genetic diversity and the absence of region-specific clusters in the southeast and south/central Asian populations suggest that soybean in these areas has been introduced repeatedly and independently from the diverse Chinese germplasm pool. The present study indicates that the two germplasm pools can be used as exotic genetic resources to enlarge the genetic bases of the respective Asian soybean populations. 相似文献
77.
Nakano K Ohsawa I Yamagata K Nakayama T Sasaki K Tarashima M Saito K Osawa M Ohta S 《Mitochondrion》2003,3(1):21-27
We isolated stable cell lines, designated as mitochondrial cells, from cybrids obtained by fusing mitochondria-less HeLa cells with platelets from patients with Leigh syndrome, a subtype of mitochondrial encephalomyopathy. The cells contain a pathogenic point mutation, T9176C, in the mitochondrial DNA. Hematoxylin-eosin staining, confocal fluorescent microscopy and flow cytometry in fixed or living cells showed that the majority of these mitochondrial cells lack nuclear DNA and nuclei, but contain active mitochondria. Despite the absence of nuclear DNA, these cells can be continuously generated in culture. Therefore, it is likely that they arise from the minority of cells which possess a nucleus. 相似文献
78.
Dietary antioxidants fail in protection against oxidative genetic damage in in vitro evaluation 总被引:1,自引:0,他引:1
Sun M Sakakibara H Ashida H Danno G Kanazawa K 《Bioscience, biotechnology, and biochemistry》2000,64(11):2395-2401
Carcinogenesis is believed to be induced through the oxidative damage of DNA, and antioxidants are expected to suppress it. So, the polyphenolic antioxidants in daily foods were investigated to see whether they protect against genetic damage by active oxygen. In the evaluation, we used a bioassay and a chemical determination, a Salmonella mutagenicity test for mutation by a N-hydroxyl radical from one of the dietary carcinogens 3-amino-1-methyl-5H-pyrido[4,3-b]indole and the formation of 8-hydroxyl (8-OHdG) from 2'-deoxyguanosine (2'-dG) in a Fenton OH-radical generating system. Thirty-one antioxidants including flavonoids were compared in terms of radical-trapping activity with bacterial DNA and 2'-dG. Antioxidants inhibited the mutation but the IC50 values were in the mM order. Against 8-OHdG formation, only alpha-tocopherol had a suppressive effect with an IC50 of 1.5 microM. Thus, except alpha-tocopherol, the dietary antioxidants did not scavenge the biological radicals faster than bacterial DNA and intact 2'-dG, indicating that they failed to prevent oxidative gene damage and probably carcinogenesis. 相似文献
79.
Composite and clinal distribution of Glycine soja in Japan revealed by RFLP analysis of mitochondrial DNA 总被引:4,自引:0,他引:4
A. Tozuka H. Fukushi T. Hirata M. Ohara A. Kanazawa T. Mikami J. Abe Y. Shimamoto 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(2):170-176
Wild soybean (Glycine soja Sieb. et Zucc.), regarded as the progenitor of cultivated soybean [G. max (L.) Merr.], is widely distributed in East Asia. We have collected 1097 G. soja plants from all over Japan and analyzed restriction fragment length polymorphisms (RFLPs) of mitochondrial DNA (mtDNA) in
them. Based on the RFLPs detected by gel-blot analysis, using coxII and atp6 as probes, the collected plants were divided into 18 groups. Five mtDNA types accounted for 94% of the plants examined. The
geographic distribution of mtDNA types revealed that, in many regions, wild soybeans grown in Japan consisted of a mixture
of plants with different types of mtDNA, occasionally even within sites. Some of the mtDNA types showed marked geographic
clines among the regions. Additionally, some wild soybeans possessed mtDNA types that were identical to those widely detected
in cultivated soybeans. Our results suggest that the analysis of mtDNA could resolve the maternal lineage among plants of
the genus Glycine subgenus Soja.
Received: 16 June 1997/Accepted: 5 August 1997 相似文献
80.
Nameki N Someya T Okano S Suemasa R Kimoto M Hanawa-Suetsugu K Terada T Shirouzu M Hirao I Takaku H Himeno H Muto A Kuramitsu S Yokoyama S Kawai G 《Journal of biochemistry》2005,138(6):729-739
Small protein B, SmpB, is a tmRNA-specific binding protein essential for trans-translation. We examined the interaction between SmpB and tmRNA from Thermus thermophilus, using biochemical and NMR methods. Chemical footprinting analyses using full-length tmRNA demonstrated that the sites protected upon SmpB binding are located exclusively in the tRNA-like domain (TLD) of tmRNA. To clarify the SmpB binding sites, we constructed several segments derived from TLD. Optical biosensor interaction analyses and melting profile analyses with mutational studies showed that SmpB efficiently binds to only a 30-nt segment that forms a stem and loop, with the 5' and 3' extensions composed of the D-loop and variable-loop analogues. The conserved sequences, 16UCGA and 319GAC, in the extensions are responsible for the SmpB binding. These results agree with the those visualized by the cocrystal structure of TLD and SmpB from Aquifex aeolicus. In addition, NMR chemical shift mapping analyses, using the 30-nt segment and (15)N-labeled SmpB, revealed the characteristic RNA binding mode. The hydrogen bond pattern around beta2 changes, with the Gly in beta2, which acts as a hinge, showing the largest chemical shift change. It appears that SmpB undergoes structural changes indicating an induced fit upon binding to the specific region of TLD. 相似文献