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   385篇
  免费   23篇
  2022年   1篇
  2021年   4篇
  2020年   6篇
  2019年   2篇
  2018年   5篇
  2017年   4篇
  2016年   6篇
  2015年   24篇
  2014年   25篇
  2013年   31篇
  2012年   26篇
  2011年   41篇
  2010年   14篇
  2009年   15篇
  2008年   19篇
  2007年   18篇
  2006年   17篇
  2005年   15篇
  2004年   25篇
  2003年   23篇
  2002年   25篇
  2001年   9篇
  2000年   4篇
  1999年   9篇
  1998年   6篇
  1997年   3篇
  1996年   1篇
  1995年   3篇
  1994年   7篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   4篇
  1985年   2篇
  1984年   4篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1970年   1篇
  1968年   1篇
排序方式: 共有408条查询结果,搜索用时 31 毫秒
1.
In a sensitive ACTH bioassay system using isolated rat adrenal cells, we tested the effect of gamma-MSH related peptides on ACTH-induced steroidogenesis. Peptides, including synthetic gamma1-, gamma2-, gamma3- and Lys-gamma3-MSH, exerted no effect in augmenting ACTH-induced steroidogenesis. None of the 16 kilodalton fragment of ACTH/beta-lipotropin precursor and its cleaved fragment had such an activity. The results are in contrast with previous reports concerning ACTH-potentiating activity of gamma-MSH related peptides and, therefore, indicate the necessity of further investigation of the principle involved in this unique biological activity.  相似文献   
2.
To clarify the role of excreted extracellular enzymes during long-term incubation in a pulp biobleaching system with white rot fungi, we developed a cultivation system in which a membrane filter is used; this membrane filter can prevent direct contact between hyphae and kraft pulp, but allows extracellular enzymes to attack the kraft pulp. Phanerochaete sordida YK-624 brightened the pulp 21.4 points to 54.0% brightness after a 5-day in vitro treatment; this value was significantly higher than the values obtained with Phanerochaete chrysosporium and Coriolus versicolor after a 7-day treatment. Our results indicate that cell-free, membrane-filtered components from the in vitro bleaching system are capable of delignifying unbleached kraft pulp. Obvious candidates for filterable reagents capable of delignifying and bleaching kraft pulp are peroxidase and phenoloxidase proteins. The level of secreted manganese peroxidase activity in the filterable components was substantial during strain YK-624 in vitro bleaching. A positive correlation between the level of manganese peroxidase and brightening of the pulp was observed.  相似文献   
3.
Summary The usefulness of LMS in postoperative immunochemotherapy of gastric cancer was investigated. In compliance with the protocol, MMC was given at a dose of 20 mg on the day of gastrectomy, and an additional 10 mg on the next day IV. The patients receiving 600 mg Tegafur daily were then divided into two groups according to whether LMS was also given or not. LMS was administered for 3 days before the operation in a daily dose of 150 mg and for 1 year or more after operation according to a schedule of 3 days' administration followed by an 11-day interval. The 2-year follow-up demonstrated that in stage III patients, the LMS (+) regimen was superior to the LMS (–) regimen, since the former prolonged the relapse-free interval significantly. The survival rate for stage III disease was also significantly higher in the LMS (+) than in the LMS (–) group. There was no significant difference in the incidence of subjective or objective side-effects between two groups. The incidence of agranulocytosis was comparable in the two groups.Gastrointestinal Cancer Research Group, Japan Levamisole Research AssociationChairmen of the Gastrointestinal Cancer Research Group, Japan LMS Research AssociationController of the Gastrointestinal Cancer Research Group, Japan LMS Research AssociationMembers of the Data Collection and Analysis SubcommitteeThis study was carried out by the Gastrointestinal Cancer Research Group, Japan LMS Research Association (directed by Prof. Kiyoshi Inokuchi, Dept. of Surgery, Kyushu University and Prof. Eiro Tsubura, Dept. of Internal Medicine, Tokushima University). The results were presented in part at the 19th General Meeting of the Japanese Society for Gastroenterological Surgery in February, 1982  相似文献   
4.
Summary A prenatal diagnosis of GM1-gangliosidosis was made in a pregnancy at risk, on the basis of a deficiency of -galactosidase activity demonstrated in cultured aminiotic fluid cells. Biochemical analyses were performed in the aborted fetus. GM1-ganglioside -galactosidase activity was reduced to 1% of the control value in both the brain and liver of the affected fetus. Lamellar bodies suggestive of membranous cytoplasmic bodies were found in cells of basal ganglions, while the accumulation of GM1-ganglioside in the brain was not remarkable.  相似文献   
5.
6.
Journal of Microbiology - The widespread use of the organochlorine insecticide lindane in the world has caused serious environmental problems. The main purpose of this paper is to investigate the...  相似文献   
7.
Fragment islands, viewed from the paradigm of island biogeographic theory, depend on continual immigration from continental sources to maintain levels of species diversity, or otherwise undergo a period of relaxation where species diversity declines to a lower equilibrium. Japan is a recently derived fragment island with a rich endemic flora and fauna. These endemic species have been described as paleoendemics, and conversely as recently derived Pleistocene colonists. Geological events in the Miocene period, notably the fragmentation and collision of islands, and the subsequent uplift of mountains in central Japan, provided opportunities for genetic isolation. More recently, cyclical climatic change during the Pliocene and Pleistocene periods led to intermittent land bridge connections to continental Asia. Here we investigate the pattern and timing of diversification in a diverse endemic lineage in order to test whether ongoing migration has sustained species diversity, whether there is evidence of relaxation, and how geological and climatic events are associated with lineage diversification. Using multi-locus genetic data, we test these hypotheses in a poorly dispersing, cold-adapted terrestrial insect lineage (Grylloblattodea: Grylloblattidae) sampled from Japan, Korea, and Russia. In phylogenetic analyses of concatenated data and a species tree approach, we find evidence of three deeply divergent lineages of rock-crawlers in Japan consistent with the pattern of island fragmentation from continental Asia. Tests of lineage diversification rates suggest that relaxation has not occurred and instead endemism has increased in the Japanese Grylloblattidae following mountain-building events in the Miocene. Although the importance of climate change in generating species diversity is a commonly held paradigm in Japanese biogeography, our analyses, including analyses of demographic change and phylogeographic range shifts in putative species, suggests that Pleistocene climatic change has had a limited effect on the diversification of rock-crawlers.  相似文献   
8.
Incubation experiments using filtered waters from Lake Kasumigaura were conducted to examine bacterial contribution to a dissolved organic carbon (DOC) pool. Bacterial abundance, bacterial production, concentrations of DOC, total dissolved amino acids (TDAA), and total dissolved neutral sugars (TDNS) were monitored during the experiments. Bacterial production during the first few days was very high (20 to 35 μg C liter−1 day−1), accounting for 40 to 70% of primary production. The total bacterial production accounted for 34 to 55% of the DOC loss during the experiment, indicating high bacterial activities in Lake Kasumigaura. The DOC degradation was only 12 to 15%, whereas the degradation of TDAA and TDNS ranged from 30 to 50%, suggesting the preferential usage of TDAA and TDNS. The contribution of bacterially derived carbon to a DOC pool in Lake Kasumigaura was estimated using d-amino acids as bacterial biomarkers and accounted for 30 to 50% of the lake DOC. These values were much higher than those estimated for the open ocean (20 to 30%). The ratio of bacterially derived carbon to bulk carbon increased slightly with time, suggesting that the bacterially derived carbon is more resistant to microbial degradation than bulk carbon. This is the first study to estimate the bacterial contribution to a DOC pool in freshwater environments. These results indicate that bacteria play even more important roles in carbon cycles in freshwater environments than in open oceans and also suggests that recent increases in recalcitrant DOC in various lakes could be attributed to bacterially derived carbon. The potential differences in bacterial contributions to dissolved organic matter (DOM) between freshwater and marine environments are discussed.  相似文献   
9.
Thiol-disulfide interchange enzyme which catalyzes the thiol-disulfide interchange was purified from cell-free extracts of Candida claussenii by acid treatment, ammonium sulfate fractionation, aqueous polymer two phase method (Dextran-PEG system), CM-Sephadex column chromatography, Sephadex G–100 and Sephadex G–200 gel filtrations. More than four active fractions were obtained on CM-Sephadex column. Further purification steps from one of these fractions resulted in two purified enzyme preparations D–l–1 and D–2 of which the increase in specific activities was 8150- and 8450-folds respectively, over the crude extract. Both purified enzymes were homogeneous in ultracentrifugal analysis.  相似文献   
10.
Sleep and Biological Rhythms - This paper reviews epidemiological findings on sleep problems among school-age children and discusses the current status and future directions of public health...  相似文献   
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