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   438篇
  免费   13篇
  451篇
  2015年   7篇
  2014年   3篇
  2013年   208篇
  2012年   7篇
  2011年   3篇
  2010年   3篇
  2008年   4篇
  2007年   5篇
  2006年   3篇
  2004年   3篇
  2003年   7篇
  2002年   10篇
  2001年   3篇
  2000年   6篇
  1999年   4篇
  1995年   3篇
  1994年   6篇
  1993年   3篇
  1991年   6篇
  1990年   3篇
  1989年   4篇
  1988年   3篇
  1987年   4篇
  1985年   6篇
  1979年   8篇
  1978年   8篇
  1977年   3篇
  1976年   4篇
  1975年   5篇
  1972年   2篇
  1969年   4篇
  1968年   2篇
  1966年   5篇
  1962年   4篇
  1959年   3篇
  1958年   2篇
  1943年   7篇
  1941年   3篇
  1940年   4篇
  1939年   4篇
  1938年   4篇
  1937年   5篇
  1936年   5篇
  1935年   2篇
  1933年   6篇
  1932年   3篇
  1931年   2篇
  1930年   2篇
  1914年   2篇
  1913年   3篇
排序方式: 共有451条查询结果,搜索用时 0 毫秒
81.
82.
An examination has been made of embryos from infertile 1-29 translocation carrying heifers. Cytogenetic measurements of C-banded chromosomes from these cattle, together with those from fertile 1-29 cows, have been made and compared with those from normal karyotypes. There are relative differences between normal animals and translocation carriers in the ratios of total to C-banded material throughout the karyotypes: their possible effects on mitosis and meiosis are discussed. Of the embryos recovered from the infertile heifers, one did not survive transplantation and others had various indications of inviability.  相似文献   
83.
Endothelial lipase (EL) inhibitors have been shown to elevate HDL-C levels in pre-clinical murine models and have potential benefit in prevention and treatment of cardiovascular diseases. Modification of the 1-ethyl-3-hydroxy-1,5-dihydro-2H-pyrrol-2-one (DHP) lead, 1, led to the discovery of a series of potent tetrahydropyrimidinedione (THP) EL inhibitors. Synthesis and SAR studies including modification of the amide group, together with changes on the pyrimidinone core led to a series of arylcycloalkyl, indanyl, and tetralinyl substituted 5-amino or 5-hydroxypyrimidinedione-4-carboxamides. Several compounds were advanced to PK evaluation. Among them, compound 4a was one of the most potent with measurable ELHDL hSerum potency and compound 3g demonstrated the best overall pharmacokinetic parameters.  相似文献   
84.
85.
86.
A subline of the rat hepatoma (H-35) cells has been identified which responds to hepatocyte-stimulating factors (HSFs) of human squamous carcinoma cells by increased synthesis of all major rat acute phase plasma proteins. The regulation occurs at the level of mRNA. Two HSFs (HSF-I and HSF-II) have been purified from conditioned medium of the squamous carcinoma cells. HSF-I is a protein with an Mr = 18,000 and pI 5.5, and HSF-II is a glycoprotein with an Mr = 34,000 and a broad, neutral to basic charge. In H-35 cells, HSF-I predominantly stimulates the synthesis of complement C3 and haptoglobin and acts synergistically with dexamethasone to stimulate alpha 1-acid glycoprotein. HSF-II stimulates cysteine protease inhibitor, alpha 1-antichymotrypsin, alpha 1-antitrypsin, fibrinogen, and hemopexin, and acts synergistically with dexamethasone to stimulate alpha 2-macroglobulin. Each HSF is between 10 and 100 times less effective in regulating proteins of the other set. Human tumor necrosis factor and interleukin-1 increase complement C3, haptoglobin, and alpha 1-acid glycoprotein, as does HSF-I, but are unable to modulate any of the other acute phase proteins. The monokines differ from HSF-I is their low activity in HepG2 cells and rat hepatocytes.  相似文献   
87.
88.
Using recombinant DNA technology, the NH2 and COOH terminal domains of the human Factor VIII molecule were co-expressed in baby hamster kidney 21 (BHK21) cells using the vaccinia virus system. Procoagulant activity was detectable in cell supernatants, thus suggesting that the central portion present in the FVIII protein (domain B) is not required for FVIII function.  相似文献   
89.
The survival of selected hygienically relevant bacterial species in activated carbon (AC) filters on a bench scale was investigated. The results revealed that after inoculation of the test strains the previously sterilized AC absorbed all bacteria (10(6) to 10(7)). After a period of 6 to 13 days without countable bacteria in the effluent, the numbers of Escherichia coli, Pseudomonas aeruginosa, and Pseudomonas putida increased up to 10(4) to 10(5) CFU/ml of effluent and 10(6) to 10(7) CFU/g of AC. When Klebsiella pneumoniae and Streptococcus faecalis were used, no growth in filters could be observed. The numbers of E. coli, P. aeruginosa, and P. putida, however, decreased immediately and showed no regrowth in nonsterile AC from a filter which had been continuously connected to running tap water for 2 months. Under these conditions an autochthonous microflora developed on the carbon surface which could be demonstrated by scanning electron microscopy and culturing methods (heterotrophic plate count). These bacteria reduced E. coli, P. aeruginosa, and P. putida densities in the effluent by a factor of more than 10(5) within 1 to 5 days. The hypothesis that antagonistic substances of the autochthonous microflora were responsible for the elimination of the artificial contamination could not be confirmed because less than 1% of the isolates of the autochthonous microflora were able to produce such substances as indicated by in vitro tests. Competition for limiting nutrients was thought to be the reason for the observed effects.  相似文献   
90.
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