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   1096篇
  免费   103篇
  2023年   6篇
  2022年   20篇
  2021年   33篇
  2020年   23篇
  2019年   20篇
  2018年   17篇
  2017年   10篇
  2016年   32篇
  2015年   60篇
  2014年   54篇
  2013年   61篇
  2012年   56篇
  2011年   80篇
  2010年   45篇
  2009年   48篇
  2008年   58篇
  2007年   63篇
  2006年   48篇
  2005年   46篇
  2004年   39篇
  2003年   36篇
  2002年   27篇
  2001年   19篇
  2000年   9篇
  1999年   14篇
  1998年   7篇
  1997年   6篇
  1996年   7篇
  1993年   10篇
  1991年   12篇
  1990年   11篇
  1989年   9篇
  1988年   9篇
  1987年   6篇
  1986年   9篇
  1985年   11篇
  1983年   11篇
  1982年   6篇
  1980年   6篇
  1979年   10篇
  1978年   7篇
  1977年   5篇
  1976年   5篇
  1975年   8篇
  1974年   5篇
  1973年   7篇
  1972年   9篇
  1970年   5篇
  1969年   7篇
  1961年   5篇
排序方式: 共有1199条查询结果,搜索用时 93 毫秒
11.
Adult T cell leukaemia/lymphoma was first recognised as a clinical entity in southwest Japan. Subsequently the Caribbean has been found to be another area where the disease is endemic, and sporadic cases have been identified in different parts of the world. The human T cell leukaemia/lymphoma virus (HTLV-I) is causally related to adult T cell leukaemia/lymphoma. A subgroup of HTLV, designated HTLV-III, has recently been isolated from many patients with the acquired immunodeficiency syndrome (AIDS) and preAIDS, and there is now evidence that this variant is the primary cause of AIDS. This is the first report from Trinidad to describe 12 cases of adult T cell leukaemia/lymphoma and 14 of AIDS. All were in patients of African descent. No cases were seen in subjects of East Indian descent, who, like those of African descent, comprise as much as 40% of the population. West Indians of African descent may have increased susceptibility to infection with both HTLV-I and HTLV-III.  相似文献   
12.
13.
The hepatic uptake of chenodeoxycholic acid, taurochenodeoxycholic acid, chenodeoxycholic acid 3-sulphate and taurochenodeoxycholate acid 3-sulphate by isolated rat hepatocytes was examined. Taurochenodeoxycholic acid, taurochenodeoxycholic acid 3-sulphate and chenodeoxycholic acid 3-sulphate uptake occurred by a saturable, energy-dependent process while chenodeoxycholic acid uptake was predominantly non-saturable, possibly simple diffusion. Apparent Km (mumol/l) and Vmax (nmol/mg protein per min) values (mean +/- S.D.), respectively, were: chenodeoxycholic acid (saturable component), 33 +/- 6.4 and 4.8 +/- 0.6; taurochenodeoxycholic acid, 11.1 +/- 2.0 and 3.1 +/- 0.5; chenodeoxycholic acid 3-sulphate, 6.1 +/- 0.9 and 2.3 +/- 0.4; and taurochenodeoxycholic acid 3-sulphate, 5.0 +/- 0.7 and 0.9 +/- 0.15. Both conjugation with taurine and sulphation at the 3 position resulted in a reduction in the values of Km and Vmax. Uptake of each of the bile acids taurochenodeoxycholic acid, taurochenodeoxycholic acid 3-sulphate and chenodeoxycholic acid 3-sulphate was competitively inhibited by the other two, with taurochenodeoxycholic acid a potent inhibitor of both taurochenodeoxycholic acid 3-sulphate and chenodeoxycholic acid 3-sulphate uptake. Other bile acids also inhibited. Uptake was inhibited by albumin in the order chenodeoxycholic acid 3-sulphate greater than taurochenodeoxycholic acid 3-sulphate greater than taurochenodeoxycholic acid and was dependent on the extent of bile acid binding to albumin.  相似文献   
14.
15.
16.
Carbon Dioxide Production by Dry Grain of Zea mays   总被引:1,自引:1,他引:0       下载免费PDF全文
Use of the gas chromatograph and a mercury-to-glass sealed respirometer adapted for gas syringe sampling, allowed the rapid, accurate characterization of CO2 evolution rates from live and from dead-sterile Zea mays L. grain dried to moisture levels of 12.6 to 1.4%. The live grain at the lowest moisture level showed an elevated rate inconsistent with the exponential increase in rate of CO2 evolution with increasing moisture found for maize with moisture contents from 4 to 12.6%. At the lowest moisture level, rates of CO2 evolution from dead-sterile grain were greater than for live grain. Moisture had no effect on CO2 evolution from dead-sterile grain. Increasing temperature and increasing levels of O2 in the storage atmosphere resulted in increased rates of CO2 evolution from both live and dead-sterile maize. CO2 production rates from live and from dead-sterile grain decreased with increasing storage time, even though respirometer CO2 concentrations were less than 1% at the end of the experiment. Our results indicate that CO2 production is not a dependable measure of respiration in dry seeds. Other experiments indicate that oxygen absorption also is not reliable in maize grain.  相似文献   
17.
18.
Bartholomew, J. W. (University of Southern California, Los Angeles), and George Paik. Isolation and identification of obligate thermophilic sporeforming bacilli from ocean basin cores. J. Bacteriol. 92:635-638. 1966.-Obligate thermophilic sporeforming aerobic bacilli were isolated from 11 ocean basin cores taken from locations in a 150 mile long area off of the coast from Ensenada, Mexico, to Santa Catalina Island, and ranging as far out from shore as 160 miles. Isolated strains of bacilli were all identified as being identical, or closely related, to Bacillus stearothermophilus.  相似文献   
19.
Summary The supernatants of effluents from an artificial rumen reactor degrading barley straw have been shown to contain lignin-derived compounds by UV spectral characteristics and pyrolysis mass spectrometry (PYMS). Most of these compounds were shown to be released by the action of rumen microorganisms. The compounds were quantified by measuring absorbance at 280 nm using bamboo-milled wood lignin as a standard. The concentration of the compounds rose from 0.5 mg·ml–1 at solid and liquid retention times (SRT and HRT) of 60 and 12 h, respectively, and a loading rate (LR) of 25 g total solids (TS)·l–1 per day to 3.5 mg·ml–1 at a SRT of 144 h, an HRT of 20 days and an LR of 15 g TS·1–1 per day. The highest concentration was below the level known to be toxic to rumen microorganisms in vitro. No indications were found for anaerobic lignin degradation in the rumen reactor. Offprint requests to: H. J. M. Op den Camp  相似文献   
20.
Pseudomonas strain AT3, isolated by elective culture with atropine, hydrolyzed atropine and grew diauxically, first on the tropic acid and then on the tropine. Tropine was also used as a sole carbon and energy source. The methyl group of tropine was eliminated as formaldehyde, and the nortropine thus formed was a precursor of 6-hydroxycyclohepta-1,4-dione. Ammonia was detected as a product of nitrogen elimination. 6-Hydroxycyclohepta-1,4-dione was oxidized to cyclohepta-1,3,5-trione by an induced NAD(sup+)-specific dehydrogenase. Although cyclohepta-1,3,5-trione is a (beta)-diketone with two potential hydrolytic cleavage sites, an induced hydrolase was specific for one of these sites, with 4,6-dioxoheptanoate as the only hydrolysis product. Unlike the alternative cleavage product (3,6-dioxoheptanoate), this compound is also a (beta)-diketone, and a second hydrolytic cleavage formed succinate and acetone. Although Pseudomonas strain AT3 was not capable of growth with acetone, the compound was not detected in the culture medium and may have been lost to the atmosphere. Exhaustive experimentation with a wide range of conditions did not result in detection of the enzymes required for cleavage of the carbon-nitrogen bonds leading to the formation of nortropine and 6-hydroxycyclohepta-1,4-dione.  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