全文获取类型
收费全文 | 1206篇 |
免费 | 122篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 49篇 |
2014年 | 44篇 |
2013年 | 58篇 |
2012年 | 77篇 |
2011年 | 74篇 |
2010年 | 41篇 |
2009年 | 42篇 |
2008年 | 56篇 |
2007年 | 44篇 |
2006年 | 56篇 |
2005年 | 38篇 |
2004年 | 47篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 45篇 |
2000年 | 49篇 |
1999年 | 29篇 |
1998年 | 23篇 |
1997年 | 20篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 10篇 |
1988年 | 23篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 17篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 6篇 |
1980年 | 12篇 |
1979年 | 16篇 |
1977年 | 7篇 |
1975年 | 8篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1971年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有1329条查询结果,搜索用时 562 毫秒
161.
Six species of bacteria (family Enterobacteriaceae) not commonly reported as associated with disease in American alligators (Alligator mississippiensis) were documented, suggesting that Aeromonas is not the only bacterium responsible for septicemia in crocodilians. These included Citrobacter freundii, Enterobacter agglomerans, Proteus sp., Morganella morganii, Serratia marcescens, and Klebsiella oxytoca. Clinical signs of disease included intensive basking, anorexia, lethargy, flaccid limb paralysis, stomatitis, and dermatitis. Our data indicated that early treatment with broad-spectrum antibiotics was preferable to waiting for sensitivity results. 相似文献
162.
Intestinal iron absorption during suckling in mammals 总被引:1,自引:0,他引:1
The maintenance of appropriate iron levels is important for mammalian health, particularly during the rapid growth period
following birth. Too little iron can lead to irreversible damage to the developing central nervous system and too much iron
at this point can have adverse long term consequences, possibly due to excessive free radical production. In order to maintain
iron levels, intestinal iron absorption is very efficient in young mammals, such that almost all of the iron in breast milk
is utilized. However this high level of absorption is unable to be down regulated in response to excess iron as it can be
in adults, implying that different regulatory processes are involved during suckling. Various mechanisms have been proposed
to explain this high absorption, including enhanced expression of the proteins involved in iron absorption in adults (particularly
DMT1 and ferroportin), non-specific uptake via pinocytosis, and the uptake of lactoferrin bound iron by the lactoferrin receptor.
However, at present the precise mechanism is unclear. It is possible that all of these components contribute to the high intestinal
iron absorption seen during suckling, or a novel, as yet undescribed, mechanism could be involved. This review summarises
the evidence for and against each of the mechanisms described above and highlights how little is known about iron homeostasis
in this vital stage of development. 相似文献
163.
164.
Determination of regional ventilation and perfusion in the lung using xenon and computed tomography. 总被引:4,自引:0,他引:4
T C Kreck M A Krueger W A Altemeier S E Sinclair H T Robertson E D Shade J Hildebrandt W J Lamm D A Frazer N L Polissar M P Hlastala 《Journal of applied physiology》2001,91(4):1741-1749
We propose a model to measure both regional ventilation (V) and perfusion (Q) in which the regional radiodensity (RD) in the lung during xenon (Xe) washin is a function of regional V (increasing RD) and Q (decreasing RD). We studied five anesthetized, paralyzed, mechanically ventilated, supine sheep. Four 2.5-mm-thick computed tomography (CT) images were simultaneously acquired immediately cephalad to the diaphragm at end inspiration for each breath during 3 min of Xe breathing. Observed changes in RD during Xe washin were used to determine regional V and Q. For 16 mm(3), Q displayed more variance than V: the coefficient of variance of Q (CV(Q)) = 1.58 +/- 0.23, the CV of V (CV(V)) = 0.46 +/- 0.07, and the ratio of CV(Q) to CV(V) = 3.5 +/- 1.1. CV(Q) (1.21 +/- 0.37) and the ratio of CV(Q) to CV(V) (2.4 +/- 1.2) were smaller at 1,000-mm(3) scale, but CV(V) (0.53 +/- 0.09) was not. V/Q distributions also displayed scale dependence: log SD of V and log SD of Q were 0.79 +/- 0.05 and 0.85 +/- 0.10 for 16-mm(3) and 0.69 +/- 0.20 and 0.67 +/- 0.10 for 1,000-mm(3) regions of lung, respectively. V and Q measurements made with CT and Xe also demonstrate vertically oriented and isogravitational heterogeneity, which are described using other methodologies. Sequential images acquired by CT during Xe breathing can be used to determine both regional V and Q noninvasively with high spatial resolution. 相似文献
165.
166.
Metabolism and Energetics of Lactococcus lactis during Growth in Complex or Synthetic Media
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
When Lactococcus lactis was grown in various complex or synthetic media, the fermentation of glucose remained homolactic whatever the medium used, with a global carbon balance of about 87%. Moreover, the nitrogen balance was not equilibrated, indicating that some amino acids led to the production of unknown nitrogen-containing carbon compounds while part of the glucose might contribute to anabolic pathways. In minimal medium containing six amino acids, a high concentration of serine was deaminated to pyruvate. This did not occur in more complete media, suggesting the presence of a regulation of this phenomenon by an amino acid. Ammonia produced during serine consumption was partly reconsumed after serine exhaustion. The values for biomass yield and biomass yield relative to ATP (Y(infATP)), the maximal growth rate, the specific rate of glucose consumption, and the corresponding rate of ATP synthesis all increased with the complexity of the medium, amino acid composition having the most pronounced effect. The Y(infATP) values were shown to range from 6.6 to 17.6 g of biomass(middot)mol of ATP(sup-1) on minimal and complex media. 相似文献
167.
R L Novak K Banerjee J Dohnal N Abayang Z Dajani 《Biochemical and biophysical research communications》1974,60(2):833-837
The modification of core RNA polymerase with 2-hydroxy-5-nitrobenzyl bromide (Koshland's Reagent) resulted in the benzylation of 6 out of 13 cysteines, and 10 out of 20 tryptophans in the polymerase, and occurred with an 8% decrease in its [θ]220. The modification resulted in a maximal inhibition of 60% of the RNA chains on both calf thymus and micrococcal DNA templates. γ-32P-ATP studies showed the inhibition occurred at RNA chain initiation. This study raises the possibility that the modified core polymerase may synthesize specific RNA(s). 相似文献
168.
Torkel Wadström Siiri Hirmo Hajdi Novak Antonio Guzman Martina Ringnér-Pantzar Meeme Utt Pär Aleljung 《Current microbiology》1997,34(5):267-272
Helicobacter pylori adhere to Kato III and Hela S3
cells in monolayer cultures. To explore whether cell surface glycoconjugates
on these two cell lines mediate binding of H. pylori, various
carbohydrates, glycoproteins, and glycolipids were tested to inhibit H.
pylori cell adhesion. The adhesion was measured (i) with a urease-based
assay and (ii) by cells stained with fluorescein. Sodium periodate and
sialidase treatment (but not α- or β-galactosidase, heparitinase,
lysozyme, or trypsin) inhibited H. pylori binding to both cell lines.
Sulfatides and sulfated glycoconjugates (50 μg/ml) but not heparin or a
number of simple carbohydrates inhibited binding (1 mg/ml). The two H.
pylori strains studied (CCUG 17874 and strain 25) showed high binding of
soluble 125I-labeled heparin and other sulfated carbohydrate
compounds.
Received: 5 July 1996 / Accepted: 17 October 1996 相似文献
169.
170.