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   481篇
  免费   7篇
  2022年   7篇
  2020年   4篇
  2019年   4篇
  2018年   6篇
  2017年   13篇
  2016年   14篇
  2015年   10篇
  2014年   8篇
  2013年   16篇
  2012年   13篇
  2011年   13篇
  2010年   14篇
  2009年   13篇
  2008年   15篇
  2007年   24篇
  2006年   15篇
  2005年   11篇
  2004年   16篇
  2003年   22篇
  2002年   18篇
  2001年   18篇
  2000年   12篇
  1999年   15篇
  1998年   5篇
  1997年   2篇
  1995年   2篇
  1993年   4篇
  1992年   19篇
  1991年   22篇
  1990年   19篇
  1989年   7篇
  1988年   9篇
  1987年   9篇
  1986年   4篇
  1985年   11篇
  1984年   5篇
  1983年   8篇
  1982年   3篇
  1981年   2篇
  1979年   7篇
  1976年   3篇
  1975年   7篇
  1974年   5篇
  1973年   2篇
  1972年   6篇
  1971年   3篇
  1970年   5篇
  1969年   5篇
  1968年   4篇
  1965年   2篇
排序方式: 共有488条查询结果,搜索用时 281 毫秒
101.
102.
103.
104.
The prevalence of hereditary autosomal dominant gastrointestinal adenomatosis in the Moscow population was estimated on the basis of elaboration of an indirect method. This estimate was found to be 1:48000. The prevalence observed is discussed in terms of ascertainment problems and peculiarities of the method of calculation proposed.  相似文献   
105.
Intraperitoneal injection of 25 micrograms/100 g body weight of 17 alpha-ethinyl estradiol to rats was shown to decrease serum cholesterol and to increase hepatic cholesterol. The rise in the level of non-labeled and C14-labeled free and esterified cholesterol in hepatic homogenate, as well as in lysosomal and cytosol fractions was accompanied by reduced activity of acyl-CoA-cholesterol acyltransferase and increased activity of lysosomal cholesterol esterase, as compared with the controls. The activity of cytoplasmic cholesterol esterase remained practically unchanged. Fistula bile of treated rats collected during 30 min was analyzed for the concentration of free cholesterol and bile acids. It has been shown that treatment of rats with 17 alpha-ethinyl estradiol caused an increase in hepatic cholesterol elimination via bile pathways.  相似文献   
106.
The oligotrophic bacterium Ancylobacter vacuolatus contains two large plasmids pREV1 and pREV2 (about 150 and 250 kb, respectively). Plasmid pREV1 carries the genes responsible for resistance to chloramphenicol, trimethoprim and y-irradiation. Plasmid pREV2 carries the genes responsible for resistance to beta-lactam antibiotics and formation of gas vacuoles. The ability to grow under oligotrophic conditions did not depend directly on either plasmid and was probably chromosome-encoded. Nevertheless, strains lacking the pREV2 plasmid had an improved capacity for growth in enriched media, as is evident from the following findings: 1) the growth rate of the strains lacking pREV2 was about 60% higher with an induction time of about two times less than those for strains carrying the plasmid; 2) the overall cell yield in rich media and colony size on non-oligotrophic agarized media increased with removal of pREV2; 3) the characteristic change in cell morphology occurring in the wild type ofA. vacuolatus when switched from oligotrophic to eutrophic growth conditions was not observed in the strains lacking pREV2; 4) bacterial strains lacking pREV2 exhibited significantly higher rRNA content than the parent strain. As a possible explanation for these phenomena, we suggest that the pREV2 plasmid carries gene(s) for protein(s) acting as repressor(s) of expression of some enzymes involved in eutrophic metabolism. Such protein(s) probably participate in switching between the oligotrophic and eutrophic types of metabolism in response to changing nutrient supply in the environment.  相似文献   
107.
Variation of serum protein allotypes serving as genetic markers of the blood has been analyzed in 29 populations of the domestic pig and subspecies of the wild boar. The population biodiversity and genetic structure have been estimated by two methods: by the frequencies of allotype combinations and with the use of a map constructed in the space of two principal components. The results obtained are the basis for determining the characteristics of the microevolution of wild boars and formation of the breeds of domestic pigs.  相似文献   
108.
In article organizational aspects of carrying out preventive and antiepidemic actions at a regional level are considered at the bird's flu epizootia. Epizootic researches have shown, that infection of poultry has taken place as a result of contact to a wild bird. Serological inspection 521 persons on presence of antibodies to a influenza A (H5N1) has not revealed seropositive persons. The conclusion, that the forecast of development of a situation for spring of 2006 is made in view of a direction of migration of a wild waterfowl is unfavourable.  相似文献   
109.
Bogacheva  I. N.  Nikitin  O. A.  Musienko  P. E.  Savokhin  A. A.  Gerasimenko  Yu. P. 《Biophysics》2009,54(3):370-374
A study was made of the stepping pattern formation in decerebrated and in chronic spinal cats during epidural stimulation (ES). The hindlimb stepping performance depended on the parameters of ES and afferent input. At non-optimal ES parameters, no stepping was induced, only muscle reflexes followed the stimulation rhythm. Optimized ES (3–5 Hz, 50–100 μA for decerebrated and 20–30 Hz, 150–250 μA for spinal cats) evoked coordinated stepping movements at a natural rate (0.8–1 Hz) accompanied by electromyographic burst activity of the corresponding muscles. In decerebrated cats, the bursts are formed owing to modulation of early responses and the late polysynaptic activity. In chronic spinal cats, this process is mainly due to amplitude modulation of the early responses. Formation of the stepping pattern in decerebrated cats involves spinal interneurons responsible for the polysynaptic activity, which allows its correction based on processing the afferent signals. Activation of this system in chronic spinal cats can be realized by afferent stimulation alone, without ES.  相似文献   
110.
We have previously found two stages of amnesia evoked by disruption of memory reconsolidation with MK-801 (NMDA glutamate receptors antagonists) application in food aversion conditioned snails. Repeated conditioning restored the food aversion at early stage of amnesia development (<10 days), whereas repeated conditioning 10 days after MK-801 application did not restore the food aversion. In present work, amnesia was induced with MK-801/reminding 24 hours after food aversion conditioning, and antiamnestic effects of NMDA receptor glycine site agonist d-cycloserine were studied at early (3rd day) or late (12th day) stages of amnesia development. D-cycloserine injection and reminding restored memory only 3 days after amnesia induction whereas d-cycloserine injection without reminding was ineffective. D-cycloserine injection and reminding as well as repeated learning 12 days after amnesia induction were also ineffective in memory restoration. Thus, for the first time, it is revealed that NMDA receptor agonist d-cycloserine influences the memory restoration processes only at early but not the later stages of amnesia development.  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