全文获取类型
收费全文 | 1860篇 |
免费 | 86篇 |
国内免费 | 1篇 |
出版年
2022年 | 11篇 |
2021年 | 39篇 |
2020年 | 30篇 |
2019年 | 24篇 |
2018年 | 44篇 |
2017年 | 33篇 |
2016年 | 50篇 |
2015年 | 70篇 |
2014年 | 95篇 |
2013年 | 136篇 |
2012年 | 131篇 |
2011年 | 143篇 |
2010年 | 85篇 |
2009年 | 77篇 |
2008年 | 104篇 |
2007年 | 95篇 |
2006年 | 107篇 |
2005年 | 76篇 |
2004年 | 61篇 |
2003年 | 62篇 |
2002年 | 46篇 |
2001年 | 36篇 |
2000年 | 26篇 |
1999年 | 27篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 18篇 |
1991年 | 7篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 7篇 |
1972年 | 11篇 |
1971年 | 8篇 |
1967年 | 8篇 |
1961年 | 7篇 |
1957年 | 8篇 |
1956年 | 7篇 |
1927年 | 8篇 |
排序方式: 共有1947条查询结果,搜索用时 265 毫秒
1.
2.
3.
Jaroslav Dršata Martin Beránek VladimÍr Palička 《Journal of enzyme inhibition and medicinal chemistry》2013,28(1):31-36
Incubation of 50 mM d -glucose with aspartate aminotransferase (AST, EC 2.6.1.1) preparations (purified pig heart enzyme or a rat liver 20,000 × g supernatant) at 25°C had no effect on enzyme activity. 50 mM d -fructose or d -ribose gradually inhibited pig heart AST under the same conditions to zero activity after 14 days. 50 mM dl -glyceraldehyde decreased enzyme activity to zero after 6 days of incubation. The inhibition of pig heart AST by 50 mM d -fructose or d -ribose was marked even at a temperature of 4°C but it was less pronounced than at 25°C. There was no effect of 0.5 mM 2-oxoglutarate on AST activity during incubation, while the presence of 25 mM l -aspartate decreased it rapidly. 0.5 mM 2-oxoglutarate partly prevented inhibition of AST by d -ribose or d -fructose, while an analogous experiment with 25 mM aspartate resulted in a rapid decline similar to that in the absence of sugars. 相似文献
4.
J.-Y. Roh H.-W. Park Y.-H. Je D.-W. Lee B.-R. Jin H.-W. Oh S. S. Gill & S.-K. Kang 《Letters in applied microbiology》1997,24(6):451-454
Bacillus thuringiensis NTB-1 isolated from soil samples in Korea produces ovoidal parasporal inclusions with proteins of approximately 24–40 kDa in size. Although serological study indicated that the isolate has a flagella (H) antigen identical with subsp. israelensis , it seemed to be non-insecticidal against Lepidoptera and Coleoptera as well as Diptera. To investigate the activity of non-insecticidal B. thuringiensis transformed with insecticidal crystal protein genes, cryIVD and cytA genes of B. thuringiensis subsp. morrisoni PG-14, highly toxic to mosquito larvae, were introduced into the isolate NTB-1. The expression of mosquitocidal crystal protein genes in NTB-1 was characterized by SDS–PAGE analysis and electron microscopy. The results showed that crystalline inclusions of host, CryIVD and CytA were stably expressed in the transformant. However, the mosquitocidal activity of transformant was similar to that of B. thuringiensis subsp. kurstaki Cry− B harbouring cryIVD and cytA genes, demonstrating that a synergistic effect by an interaction of both introduced insecticidal and resident non-insecticidal crystal proteins was not observed. 相似文献
5.
Il-Young Paik Hwa-Eun Jin Ah-Ram Suh Hee-Tae Roh Sang-Hoon Suh 《Biochemical and biophysical research communications》2009,383(1):103-107
To investigate the effects of hydration status on oxidative DNA damage and exercise performance, 10 subjects ran on a treadmill until exhaustion at 80% VO2max during four different trials [control (C), 3% dehydration (D), 3% dehydration + water (W) or 3% dehydration + sports drink (S)]. Dehydration significantly decreased exercise time to exhaustion (D < C and S). Plasma MDA levels were significantly higher at pre-exercise in D than C. Plasma TAS was significantly lower at pre-exercise in C and S than in D, and was significantly lower in S than D at 60 min of recovery. Dehydration significantly increased oxidative DNA damage during exercise, but fluid replacement with water or sports drink alleviated it equally. These results suggest that (1) dehydration impairs exercise performance and increases DNA damage during exercise to exhaustion; and (2) fluid replacement prolongs exercise endurance and attenuates DNA damage. 相似文献
6.
Summary Two siblings with a short-limb dwarfing condition which we call acromesomelic dysplasia, Hunter-Thompson type are reported. Abnormalities are limited to the limbs and limb joints in this severe form of dwarfism. The middle and distal
segments of the limbs are most affected. The lower limbs are more affected than the upper. We are aware of one previously
published case of this entity reported by A. G. W. Hunter and M. W. Thompson in 1976. Dislocations of the elbows and ankles
were present in all three patients and dislocations of the hips and knees in two. One of the siblings who did not have hip
and knee dislocations clinically resembled Grebe chondrodysplasia, another severe acromesomelic dwarfing condition. However,
radiological analysis suggests that while acromesomelic dysplasia, Hunter-Thompson type and Grebe chondrodysplasia are related,
they are not identical. Grebe chondrodysplasia has been established as an autosomal recessive trait. It appears probable that
the entity we describe has the same mode of genetic transmission. 相似文献
7.
Hana Votavová Vladimír Gut Karel Bláha Jaroslav Šponar 《International journal of biological macromolecules》1982,4(6):341-346
DNA complexes with polypeptides (Lys-Ala-Ala)1)] and (Lys-Ala-Ala)34 have been studied using the methods of thermal melting and circular dichroism. Derivative melting curves of (Lys-Ala-Ala)10 DNA differed substantially from those of (Lys-Ala-Ala)34 prepared either by salt gradient dialysis or by direct mixing. Melting curves of the former complex were unimodal or bimodal with Tm increasing continuously withn input lysin-to-DNA phosphate ratio (r); those of the latter complex consisted of three separate transitions with Tm values almost independent of r. Complete reversibility of binding in the (Lys-Ala-Ala)10-DNA system but a slow redistribution of (Lys-Ala-Ala)34 on DNA at low temperature were found in the redistribution experiments Much faster redistribution from denatured to native DNA occurs at the temperature of melting, contributing to the unusual trimodal melting pattern. Circular dichroism curves are very similar for both complexes and indicate little change of DNA conformation upon polypeptide binding. 相似文献
8.
88 rice and 75 soybean samples were collected from 8 provinces of Korea from March through September in 1988. The Fusarium mycotoxins, zearalenone was analyzed by direct competitive enzyme linked immunosorbent assay. 10.2% of rice and 9.3 % of soybean samples contained detectable zearalenone. The average levels of zearalenone of rice and soybean samples were 11.78μg/kg and 7.70μ/kg, respectively. 相似文献
9.
10.
Jaroslav Votruba Jarmila Pazlarová Milada Dvořáková Kalju Vanatalu Libuše Váchová Marie Strnadová Helena Kučerová Jiří Chaloupka 《Applied microbiology and biotechnology》1987,26(4):373-377
Summary A mathematical model was formulated to describe the kinetics and stoichiometry of growth and proteinase production in Bacillus megaterium. Synthesis of the extracellular proteinase in a batch culture is repressed by amino acids. The specific rate of formation of the enzyme (r
E) can be described by the formula {ie373-1}, where k
2 and k
3 stand for the non-repressible and repressible part of enzyme synthesis respectively, k
S
2 is a repression coefficient and S
2 indicates the concentration of amono acids; the values of k
2 and k
S
2 depend on the composition of the mixture of amino acids. Even in a high concentration, a single amino acid is less effective than a mixture of amino acids. The dependence of the proteinase repression on the concentration of an external amino acid (leucine) follows the same course as its rate of incorporation into proteins, approaching saturation at concentrations higher than 50 M (half saturation approximately 10 M). However, the total uptake of leucine did not exhibit any saturation even at 500 M external concentration.Symbols
X
biomass concentration, g/l
-
E
proteinase concentration, unit/l
-
t
time, h
-
S
1
concentration of glucose, g/l
-
S
2
concentration of amino acids, g/l
-
specific growth rate, l/h
-
rE
specific rate of enzyme production, unit/g/h
-
k
1
growth kinetic constant, l/h
-
k
2
product formation kinetic constant (for non-repressible part of enzyme synthesis), unit/g
-
k
3
product formation kinetic constant (for repressible portion of enzyme synthesis), unit/g
-
k
S
1
saturation constant, g/l
-
k
S
2
repression coefficient for a certain amino acid or amino acids mixture, g/l 相似文献