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   1095篇
  免费   27篇
  2022年   7篇
  2021年   14篇
  2019年   15篇
  2018年   18篇
  2017年   18篇
  2016年   27篇
  2015年   14篇
  2014年   26篇
  2013年   28篇
  2012年   40篇
  2011年   47篇
  2010年   38篇
  2009年   25篇
  2008年   45篇
  2007年   38篇
  2006年   37篇
  2005年   42篇
  2004年   46篇
  2003年   47篇
  2002年   57篇
  2001年   29篇
  2000年   36篇
  1999年   27篇
  1997年   7篇
  1992年   17篇
  1991年   28篇
  1990年   21篇
  1989年   24篇
  1988年   21篇
  1987年   12篇
  1986年   18篇
  1985年   15篇
  1984年   13篇
  1983年   18篇
  1980年   6篇
  1979年   12篇
  1978年   11篇
  1977年   7篇
  1976年   11篇
  1975年   14篇
  1974年   13篇
  1973年   15篇
  1972年   12篇
  1971年   12篇
  1970年   9篇
  1969年   8篇
  1968年   11篇
  1967年   8篇
  1966年   12篇
  1965年   14篇
排序方式: 共有1122条查询结果,搜索用时 31 毫秒
151.
152.
153.
In experiments on mice and in vitro the influence of neurotensin pentagastrin and thymopentin on the immune response, the phagocytosis of staphylococcus aureus by polymorphoneutrophil leucocytes and enzymatic activity of these cells by NBT-test were investigated. It was shown that neurotensin and thymopentin increase enzymatic and phagocytic function of polymorphoneutrophil leucocytes. Pentagastrin, as well as thymopentin stimulates the immune response, enzymatic but not phagocytic function of polymorphoneutrophil leucocytes. Immunostimulating effect of the studied peptides was realized by facility differentiation of mouse bone marrow cells into T-lymphocytes and by the interaction of the peptides with T-cells.  相似文献   
154.
155.
156.
In this study conservation of Castilleja levisecta Greenm., a globally endangered species was addressed through in vitro cryopreservation of shoot tips. In vitro cultures were successfully established using seedlings received from British Columbia, Canada. Shoot tips excised from in vitro propagated plants were cryopreserved using a droplet-vitrification method following optimization of individual protocol steps such as pre-culture, treatment with vitrification solutions, and unloading. The highest plant regrowth after cryopreservation (66%) was achieved when shoot tips were pre-cultured in 0.3 M sucrose for 17 h followed by 0.5 M sucrose for 4 h, incubated in an osmo-protectant solution (17.5% [v/v] glycerol and 17.5% [w/v] sucrose) for 20 min, exposed to vitrification solution A3 (37.5% [v/v] glycerol plus 15% [v/v] dimethylsulfoxide (DMSO) plus 15% [v/v] ethylene glycol (EG) plus 22.5% [w/v] sucrose) on ice for 40 min, and unloaded in 0.8 M sucrose solution for 30 min. Healthy plants were developed from cryopreserved shoot tips and propagated in vitro using nodal segments. Plants derived from in vitro culture and from cryopreserved tissues were successfully rooted and acclimated in a greenhouse with 100% survival rate. Acclimatized plants were reintroduced in a naturalized propagation area at the Conservation Nursery at Fort Rodd Hill, Canada. Twenty of 94 reintroduced plants (21%) survived the transit from lab to field and some had started to flower. This is the first report for cryopreservation of C. levisecta, an important step in conserving and re-introducing this critically imperiled species in nature.  相似文献   
157.
Human serum albumin is playing an increasing role as a drug carrier in clinical settings. Biotin molecules are often used as suitable tags in targeted anti-tumor drug delivery systems. We report on the synthesis and properties of a new multimodal theranostic conjugate based on an anti-cancer fluorinated nucleotide conjugated with a biotinylated dual-labeled albumin. Interestingly, in vitro and in vivo study revealed stronger anti-tumor activity of the non-tagged theranostic conjugate than that of the biotin-tagged conjugate, which can be explained by decreased binding of the biotin-tagged conjugate to cellular receptors. Our study sheds light on the importance of site-specific albumin modification for the design of albumin-based drugs with desirable pharmaceutical properties.  相似文献   
158.
This work is directed at continuous studies of cyclicity of long-term (1980–2010) population dynamics of odonates in the basin of Lake Chany (in the south of Western Siberia). Four sympatric species of the genus Sympetrum have been investigated by spectral analysis method. The cycle spectra of population dynamics have been constructed for each species; the basic parameters of these cycles (period, phase, and power) have been calculated. Special number cycles have been found for each species. Interspecies differences increased in the direction from high to low frequencies of the spectrum. In the cases of similar cycles, interspecies differences have been shown in the ratio of cycle powers and/or phases: identical phases can indicate the ability of species to increase their number synchronously with any of close species; different phases can indicate the possibility of a small-numbered species to reach its maximum number against the minimum number of numerous species. A comparison of sympatric species spectra of the genera Coenagrion and Sympetrum has led to the conclusion that, the more similarity there is in environmental standards among species inside a genus (as for Sympetrum), the more specific the species frequency spectra are. All species of the genus Sympetrum can synchronize their number fluctuations with 2- to 3 and 4- to 5-year fluctuations of the local climate. Also specific synchronization with important nature-climatic rhythms was found for each species: for S. danae, with an 18-year rhythm of the level of Lake Chany and with a 16-year rhythm of June temperatures; for S. flaveolum, with a 24-year Brickner cycle, with an 8-year cycle of rainfall, and with a 28-year cycle of April and May temperatures; for S. vulgatum, with a 40- to 42-year cycle of the level of Lake Chany, with 12-year cycle of rainfall, and with a 7-year cycle of April and June temperatures; and for S. sanguineum, with a 7-year cycle of April and June temperatures. Perhaps the adaptation mechanism of species to each other and to environments is enclosed in the cyclicity of long-term fluctuations of species number.  相似文献   
159.
The Institute of Biophysics SB RAS hosts and maintains a specialized collection of luminous bacteria (CCIBSO 836) containing over 700 strains isolated in various regions of the world's oceans. The culture collection is a source of lux genes and biologically active substances. The wide application of bioluminescence in medicine and ecology has given importance to analysing information on the structure and functioning of bioluminescence systems in natural and transgenic microorganisms, as well as on their features that are closely interrelated with bioluminescence. The aims of our BIOLUMBASE database are: gathering information on microorganisms with lux genes, their analysis and free access, and distribution of this data throughout the global network. The database includes two sections, natural and transgenic luminous microorganisms, and is updated by our own experimental results, the published literature and internet resources. For the future, a publicly available internet site for BIOLUMBASE is planned. This will list the strains and provide comprehensive information on the properties and functions of luminous bacteria, the mechanisms of regulation of bioluminescence systems, constructs with lux genes, and applications of bioluminescence in microbiology, ecology, medicine and biotechnology. It is noteworthy that this database will also be useful for evaluation of biological hazards of transgenic strains. Users will be able to carry out bibliographic and strain searches starting from any feature of interest.  相似文献   
160.
Acid-soluble (“free”) nucleotides, nucleosides and bases were analyzed in the mycelium and in the culture filtrate of the fungusPenicillium sizowi, using micro-thin-layer chromatography on alumina and densitometry of the zones of the individual components. It was found that the levels of the various components underwent complicated changes, the corresponding curves exhibiting from one to three maxima which occur at different periods of cultivation. It was observed that a substantial amount of nucleotides, nucleosides and bases occurs in the medium as early as at the beginning of the exponential phase of growth. An attempt was made to elucidate some peculiarities of the nucleotide pool ofPenicillium species, using enzymes responsible for the individual transformations of nucleotides, nucleosides and bases.  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