全文获取类型
收费全文 | 1208篇 |
免费 | 80篇 |
出版年
2022年 | 5篇 |
2021年 | 20篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 26篇 |
2015年 | 23篇 |
2014年 | 41篇 |
2013年 | 52篇 |
2012年 | 85篇 |
2011年 | 134篇 |
2010年 | 99篇 |
2009年 | 76篇 |
2008年 | 66篇 |
2007年 | 74篇 |
2006年 | 65篇 |
2005年 | 76篇 |
2004年 | 62篇 |
2003年 | 44篇 |
2002年 | 45篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 12篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1974年 | 11篇 |
1973年 | 5篇 |
1972年 | 4篇 |
1971年 | 8篇 |
1970年 | 3篇 |
1966年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有1288条查询结果,搜索用时 15 毫秒
1.
In experimental (white rats, rabbits) and clinical (erythrocytes, blood plasma) studies on 29 healthy subjects and patients it has been demonstrated that primary or secondary n-quinone deficiency is accompanied by increased tissue activity of glycolysis enzymes (aldolase, PGmutase) and aerobic pentose phosphate shunt (6 GPDH). Parallel rise in the amount of glycolysis metabolites (pyruvate and lactate) in the blood and the decline in blood plasma glucose level were observed. The changes in glucose-6-phosphate metabolism are, probably, secondary and reflect tissue structure alterations in the development of K and E avitaminosis. 相似文献
2.
Structural variants of mercury reductase containing the N-terminal domain, which is easily cleaved by trypsin, have been found in Gram-positive bacteria with a low genomic G + C content (Bacillus, Staphylococcus and, possibly, some other genera). Mercury reductases without the N-terminal domain and relatively resistant to limited proteolysis are typical for Gram-positive bacteria with a high genomic G + C content (Arthrobacter, Citreobacterium, Micrococcus, Mycobacterium, Rhodococcus). Both types of mercury reductase genes may be located on plasmids. 相似文献
3.
4.
Common antigens of mouse oval and biliary epithelial cells. Expression on newly formed hepatocytes 总被引:17,自引:0,他引:17
Natalya V. Engelhardt Valentina M. Factor Alla K. Yasova Valentina S. Poltoranina Vladimir N. Baranov Maria N. Lasareva 《Differentiation; research in biological diversity》1990,45(1):29-37
Two antigens - A6 and G7 - shared by mouse biliary epithelial and oval cells were revealed by monoclonal antibodies raised in rat immunized with oval-cell-enriched liver fraction. Oval cells were induced in CBA or F1 (CBA x C57BL6) mice by a combination of a single injection of the alkylating drug Dipin with partial hepatectomy. In normal liver A6 antigen was localized, using light and electron microscopy, in biliary epithelial cells of all ducts including Hering canals. Some bile ductal and Hering cells were A6-negative. Occasionally, A6 antigen was present in single hepatocytes forming the periportal ends of hepatic cords. In preneoplastic and tumorous liver A6 antigen was present in bile ductal and oval cells and in a fraction of newly formed hepatocytes and tumor cells. G7 antigen was revealed in normal, precancerous and tumorous liver in biliary epithelial and oval cells but not in hepatocytes. A6 and G7 antigens were not liver-specific: they were expressed in various normal organs and tissues, especially in epithelia. In studies of mouse liver lineages A6 antigen can be used as a common marker of biliary epithelial and oval cells and hepatocytes at certain stages of differentiation. G7 antigen is a marker of oval and biliary epithelial cells. There was a striking similarity in A6 antigen localization to that of human blood group antigens in normal liver and liver tumors. A6 antigen may thus provide a useful tool for the study of neoexpression of human blood group antigens in liver tumors. 相似文献
5.
Iu I Gubski? O V Zadorina A N Fedorov L A Bogdanova 《Ukrainski? biokhimicheski? zhurnal》1991,63(4):81-87
It is shown that in case of antioxidant insufficiency (AOI) activation of NADPH- and ascorbate-dependent lipid peroxidation (LPO) in sarcoplasmic reticulum (SR) of skeletal muscles proceeds 1.7 and 4.1 times faster, respectively. Activation of lipid peroxidation in AOI leads to damage of Ca2+ transport processes in SR of skeletal muscles. Under these conditions ATP-dependent accumulation of 45Ca (by 88%) and Ca(2+)-ATPase (by 14%) activity in SR of skeletal muscles falls. In case of AOI a significant disturbance of passive Ca2+ transport in SR of skeletal muscles takes place, being characterized by an increased passive 45Ca output from vesicles due to breakage of the biomembrane permeability as a result of lipid peroxidation of membranes. Treatment of animals with ionol, a synthetic antioxidant, causes a decrease of activated NADPH- and ascorbate-dependent LPO in SR of skeletal muscles and stabilization of Ca2+ transport processes. 相似文献
6.
7.
Unsaturated fatty acids at concentrations of 1–2 μmol mg-1 chlorophyll decrease the intensity of long-lived delayed fluorescence and inhibit the Hill reaction in Pisum sativum L. chloroplasts in a pH-dependent and reversible manner. A charged form of the fatty acids is two times more effective than an undissociated form. Fatty acids, anionic and cationic detergents and urea inhibit activity and decrease the temperature of heat inactivation of the water-spilitting system. Sucrose at a concentration of 2.5 M protects chloroplasts against the effects of these compounds. It is concluded that their action can be explained by the denaturation of the water-splitting protein. 相似文献
8.
N I Neshev Iu G Bogdanova E V Radchenko I K Sarycheva 《Izvestiia Akademii nauk SSSR. Seriia biologicheskaia》1989,(2):290-293
The effect of alpha-tocopherol and its synthetic analogue which does not contain an isoprenoid chain, 2,2,5,7,8-pentamethyl-6-hydroxychroman (chromanol), on rat erythrocyte and hemoglobin has been studied. Chromanol, unlike alpha-tocopherol, induces oxidation of hemoglobin into aquomethemoglobin and causes erythrocyte hemolysis. A mechanism of the reaction has been established. It consists of two-electron reduction of haem-associated oxygen molecule. The products formed can cause oxidative membrane damage and subsequent hemolysis. The absence of similar activity of alpha-tocopherol seems to be connected with the inaccessibility of ligand sphere of hemin iron because of the presence of the isoprenoid chain. The oxidative activity of chromanol can explain the absence of E-vitamin activity in this compound. 相似文献
9.
L. Zavalova S. Lukyanov I. Baskova E. Snezhkov S. Akopov S. Berezhnoy E. Bogdanova E. Barsova E. D. Sverdlov 《Molecular & general genetics : MGG》1996,253(1-2):20-25
We previously detected in salivary gland secretions of the medicinal leech (Hirudo medicinalis) a novel enzymatic activity, endo-ɛ(γ-Glu)-Lys isopeptidase, which cleaves isopeptide bonds formed by transglutaminase (Factor
XIIIa) between glutamine γ-carboxamide and the ɛ-amino group of lysine. Such isopeptide bonds, either within or between protein
polypeptide chains are formed in many biological processes. However, before we started our work no enzymes were known to be
capable of specifically splitting isopeptide bonds in proteins. The isopeptidase activity we detected was specific for isopeptide
bonds. The enzyme was termed destabilase. Here we report the first purification of destabilase, part of its amino acid sequence,
isolation and sequencing of two related cDNAs derived from the gene family that encodes destabilase proteins, and the detection
of isopeptidase activity encoded by one of these cDNAs cloned in a baculovirus expression vector. The deduced mature protein
products of these cDNAs contain 115 and 116 amino acid residues, including 14 highly conserved Cys residues, and are formed
from precursors containing specific leader peptides. No homologous sequences were found in public databases.
Received: 9 April 1996 / Accepted: 17 May 1996 相似文献
10.
Cold acclimation and photoinhibition of photosynthesis in Scots pine 总被引:13,自引:0,他引:13
Alla Krivosheeva Da-Li Tao Christina Ottander Gunnar Wingsle Sylvain L. Dube Gunnar Öquist 《Planta》1996,200(3):296-305
Cold acclimation of Scots pine did not affect the susceptibility of photosynthesis to photoinhibition. Cold acclimation did however cause a suppression of the rate of CO2 uptake, and at given light and temperature conditions a larger fraction of the photosystem II reaction centres were closed in cold-acclimated than in nonacclimated pine. Therefore, when assayed at the level of photosystem II reaction centres, i.e. in relation to the degree of photosystem closure, cold acclimation caused a significant increase in resistance to photoinhibition; at given levels of photosystem II closure the resistance to photoinhibition was higher after cold acclimation. This was particularly evident in measurements at 20° C. The amounts and activities of the majority of analyzed active oxygen scavengers were higher after cold acclimation. We suggest that this increase in protective enzymes and compounds, particularly Superoxide dismutase, ascorbate peroxidase, glutathione reductase and ascorbate of the chloroplasts, enables Scots pine to avoid excessive photoinhibition of photosynthesis despite partial suppression of photosynthesis upon cold acclimation. An increased capacity for light-induced de-epoxidation of violaxanthin to zeaxanthin upon cold acclimation may also be of significance.Abbreviations APX
ascorbate peroxidase
- DHA
dehydroascorbate
- DHAR
dehydroascorbate reductase
- Fm
maximal fluorescence when all reaction centres are closed
- Fv/Fm
maximum photochemical yield of PSII
- GR
glutathione reductase
- GSH
reduced glutathione
- Je
rate of photosynthetic electron transport
- MDAR
monodehydroascorbate reductase
- qN
nonphotochemical quenching of fluorescence
- qP
photochemical quenching of fluorescence
- SOD
superoxide dismutase
This work was supported by the Swedish Natural Science Research Council and the National Natural Science Foundation of China. 相似文献