首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   956篇
  免费   50篇
  2022年   3篇
  2021年   8篇
  2020年   5篇
  2019年   4篇
  2018年   6篇
  2017年   8篇
  2016年   15篇
  2015年   20篇
  2014年   34篇
  2013年   52篇
  2012年   67篇
  2011年   55篇
  2010年   32篇
  2009年   34篇
  2008年   52篇
  2007年   62篇
  2006年   52篇
  2005年   75篇
  2004年   70篇
  2003年   71篇
  2002年   54篇
  2001年   16篇
  2000年   21篇
  1999年   19篇
  1998年   8篇
  1997年   12篇
  1996年   6篇
  1995年   8篇
  1994年   11篇
  1993年   4篇
  1992年   13篇
  1991年   11篇
  1990年   7篇
  1989年   9篇
  1988年   15篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   7篇
  1983年   3篇
  1982年   4篇
  1981年   8篇
  1980年   5篇
  1979年   2篇
  1978年   4篇
  1975年   2篇
  1973年   2篇
  1972年   4篇
  1971年   3篇
  1962年   1篇
排序方式: 共有1006条查询结果,搜索用时 234 毫秒
971.
Body condition in mammals fluctuates depending on energy intake and expenditure. For brown bears (Ursus arctos), high‐protein foods facilitate efficient mass gain, while lipids and carbohydrates play important roles in adjusting dietary protein content to optimal levels to maximize energy intake. On the Shiretoko Peninsula, Hokkaido, Japan, brown bears have seasonal access to high‐lipid pine nuts and high‐protein salmon. To assess seasonal and annual fluctuation in the body condition of adult female brown bears in relation to diet and reproductive status, we conducted a longitudinal study in a special wildlife protection area on the Shiretoko Peninsula during 2012–2018. First, analyses of 2,079 bear scats revealed that pine nuts accounted for 39.8% of energy intake in August and salmon accounted for 46.1% in September and that their consumption by bears varied annually. Second, we calculated the ratio of torso height to torso length as an index of body condition from 1,226 photographs of 12 adult females. Results indicated that body condition continued to decline until late August and started to increase in September when salmon consumption increased. In addition, body condition began to recover earlier in years when consumption of both pine nuts and salmon was high. Furthermore, females with offspring had poorer body condition than solitary females, in particular in late August in years with low salmon consumption. Our findings suggest that coastal and subalpine foods, which are unique to the Shiretoko Peninsula, determine the summer body condition of female brown bears, as well as their survival and reproductive success.  相似文献   
972.
Summary Cultured cells of Lavandula vera were entrapped with photosensitive synthetic resin prepolymers (PVA-SbQ). PVA-SbQ-entrapped cells grew well inside gel matrices and synthesized de novo blue pigments in the presence of l-cysteine as an inducer. The entrapped cells were superior to calcium alginate-entrapped cells judging from cell growth and total pigment productivity. Release of the pigments, which were almost insoluble in water, from the gels was markedly enhanced by the increase in hydrophilicity of the cell-entrapping gels. The entrapped cells could be used repeatedly for the pigment production.Dedicated to Professor Dr. Georg Manecke on occasion of his 70th birthday  相似文献   
973.
Recombinant plasminogen-activator-inhibitor type 1 (PAI-1) purified in an active form from Escherichia coli and eucaryotic cells was found to contain a mixture of three functionally distinct forms: an active form that forms complexes with plasminogen activators (PAs), an inactive (latent) form that remains intact after incubation with PAs, and a substrate-like form which is easily cleaved by PAs. Since active PAI-1 purified from bacteria (rpPAI-1) contains only trace amounts of the inactive latent and the substrate-like forms, this material was used to study the effect of sodium dodecyl sulphate (SDS) on the structure and function of active PAI-1. After treatment with 0.01% SDS, active rpPAI-1 was converted to an inactive form that did not form complexes with PAs, but exhibited characteristics similar to those of latent PAI-1. After treatment with 0.1% SDS, PAI-1 lost its inhibitory activity and was cleaved as a substrate in the reactive center. Circular dichroism spectral analysis reveals that SDS changed the conformation of PAI-1 dramatically, mainly by increasing its alpha-helical content.  相似文献   
974.
Production of interferon (IFN)-gamma was investigated in human peripheral lymphocytes stimulated with Mycoplasma pneumoniae. Lymphocytes obtained from non-immune individuals produced no IFN. IFN-gamma was produced by T cells obtained from immune individuals, and the helper/inducer T cells produced two- to sixfold higher titer of IFN-gamma than the suppressor/cytotoxic T cells. The addition of macrophages in T cell cultures suppressed the production of IFN-gamma; this differs from the previous result wherein the addition of macrophages enhanced the production of IFN-gamma, when stimulated with mumps virus or measles virus.  相似文献   
975.
Parkin promotes cell survival by removing damaged mitochondria via mitophagy. However, although some studies have suggested that Parkin induces cell death, the regulatory mechanism underlying the dual role of Parkin remains unknown. Herein, we report that mitochondrial ubiquitin ligase (MITOL/MARCH5) regulates Parkin‐mediated cell death through the FKBP38‐dependent dynamic translocation from the mitochondria to the ER during mitophagy. Mechanistically, MITOL mediates ubiquitination of Parkin at lysine 220 residue, which promotes its proteasomal degradation, and thereby fine‐tunes mitophagy by controlling the quantity of Parkin. Deletion of MITOL leads to accumulation of the phosphorylated active form of Parkin in the ER, resulting in FKBP38 degradation and enhanced cell death. Thus, we have shown that MITOL blocks Parkin‐induced cell death, at least partially, by protecting FKBP38 from Parkin. Our findings unveil the regulation of the dual function of Parkin and provide a novel perspective on the pathogenesis of PD.  相似文献   
976.
977.
A trivalent measles-mumps-rubella live virus vaccine, containing measles AIK-C strain, mumps Hoshino strain, and rubella Takahashi strain, was evaluated in 229 children, aged 1 to 5 years. The vaccine induced a high seroconversion rate: 221 (98.7%) out of 224 subjects initially seronegative for measles virus, 167 (93.3%) out of 179 initially seronegative for mumps virus, and 212 (99.1%) out of 214 initially seronegative for rubella virus. It also induced a sufficient cellular immunity against each of the three viruses in over 90% of the subjects, as judged by virus-specific interferon-gamma (IFN-gamma) production. Virus-specific IFN-gamma production was observed 10 days after vaccination by stimulation with measles virus and rubella virus and 14 days after vaccination by stimulation with mumps virus. Mumps-virus-specific IFN-gamma production was observed in 7 out of 12 recipients without seroconversion for mumps virus. And measles-virus-specific IFN-gamma production was demonstrated in one out of three recipients without seroconversion for measles virus. A significant correlation was observed between the serum antibody and IFN-gamma production six weeks after vaccination for measles virus (r = 0.201, P less than 0.01) and for mumps virus (r = 0.174, P less than 0.05) but not for rubella virus (r = -0.045, P less than 0.05). The incidence of febrile reactions of greater than or equal to 37.5 C was quite low, 14.4%, and that of greater than or equal to 39 C occurred in only 1.3% of the recipients. These results suggested that the trivalent vaccine induced sufficient humoral and cellular immunity and yet resulted in no more untoward reaction than observed from the measles vaccine alone.  相似文献   
978.
979.
Acquired radioresistance of cancer cells interferes with radiotherapy and increases the probability of cancer recurrence. HepG2‐8960‐R, which is one of several clinically relevant radioresistant (CRR) cell lines, has a high tolerance to the repeated clinically relevant doses of X‐ray radiation. In this study, HepG2‐8960‐R had slightly lower cell proliferation ability than HepG2 in the presence of FBS. In particular, epidermal growth factor (EGF) hardly enhanced cell proliferation and DNA synthesis in HepG2‐8960‐R. Additionally, EGF could not induce the activation of Erk1/2, because the expression of EGF receptor (EGFR) protein decreased in HepG2‐8960‐R in accordance with the methylation of the EGFR promoter region. Therefore, cetuximab did not inhibit HepG2‐8960‐R cell proliferation. Our study showed that HepG2‐8960‐R had radioresistant and cetuximab‐resistant abilities. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
980.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号