全文获取类型
收费全文 | 3230篇 |
免费 | 323篇 |
国内免费 | 13篇 |
出版年
2023年 | 11篇 |
2022年 | 44篇 |
2021年 | 73篇 |
2020年 | 47篇 |
2019年 | 62篇 |
2018年 | 69篇 |
2017年 | 36篇 |
2016年 | 95篇 |
2015年 | 139篇 |
2014年 | 156篇 |
2013年 | 186篇 |
2012年 | 215篇 |
2011年 | 182篇 |
2010年 | 126篇 |
2009年 | 97篇 |
2008年 | 149篇 |
2007年 | 126篇 |
2006年 | 140篇 |
2005年 | 123篇 |
2004年 | 139篇 |
2003年 | 121篇 |
2002年 | 96篇 |
2001年 | 110篇 |
2000年 | 70篇 |
1999年 | 98篇 |
1998年 | 37篇 |
1997年 | 40篇 |
1996年 | 41篇 |
1995年 | 32篇 |
1994年 | 34篇 |
1993年 | 28篇 |
1992年 | 47篇 |
1991年 | 55篇 |
1990年 | 55篇 |
1989年 | 60篇 |
1988年 | 49篇 |
1987年 | 43篇 |
1986年 | 40篇 |
1985年 | 31篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1973年 | 9篇 |
1970年 | 13篇 |
1967年 | 9篇 |
排序方式: 共有3566条查询结果,搜索用时 265 毫秒
91.
The method proposed for measuring glutathione peroxydase (GSH-Px) activity is based on the determination of oxidized glutathione (GSSG) using o-phtalaldehyde (OPT) as a fluorescent reagent. This method makes it possible to study the kinetics of both substrates (peroxide and reduced glutathione, GSH), and allosteric kinetics were found for GSH, with human platelets as the source of GSH-Px. Different methods for platelet disruption were compared. The reference values obtained for GSH-Px activity in human blood platelets by this fluorimetric procedure and the conventional enzymatic method were very similar and significantly higher than those previously reported; the reasons for this difference are discussed. 相似文献
92.
M Donnadieu R M Schimpff P Garnier M J Martinez J L Chaussain J C Job 《Comptes rendus des séances de la Société de biologie et de ses filiales》1980,174(4):564-573
Plasma transferrin is significantly positively correlated to the growth velocity in normal children and children with various growth disorders. In hypopituitary dwarfs, both plasma transferrin and somatomedin are significantly lower than in controls. Acute variations of the plasma transferrin levels could be involved in the regulation of the GH secretion by a feedback mechanism. Yet, transferrin is neither a somatomedin or a somatomedin-binding protein, and the mechanisms relating growth to transferrin remain unknown. 相似文献
93.
1. The transfer of excitation energy between the fluorescent probes 1,6-diphenylhexa-1,3,5-triene and 12-(9-anthroyl)stearic acid and the cholesterol analogue cholesta-4,6-dien-3-one in phosphatidylcholine liposomes has been investigated. 2. The results indicate that probes and steroid are randomly distributed in the bilayer at steroid concentrations up to 35 mol%. 3. The degree of polarization of diphenylhexatriene fluorescence increases with increasing cholesterol content. Other sterols, differing in structure in the region of the polar group or in the side chain at position-17, produce similar but not identical effects. 4. the results are consistent with the proposal that diphenylhexatriene gives a general picture of the state of the bilayer and that there is no segregation of sterols in liquid-crystalline phosphatidylcholine bilayers. 相似文献
94.
Four new species of Penicillium Link ex Fries are described and illustrated. All of them but one have been isolated from the atmosphere in Madrid, Spain. They clearly differ from all species of the genus described so far and are, therefore, described and proposed as new taxa: Penicillium aurantio-flammiferum sp. nov., Penicillium gallaicum sp. nov., Penicillium granatense sp. nov., and Penicillium ilerdanum sp. nov. 相似文献
95.
The flavonoid aglycone analysis of 20 Thymus taxa (most Iberic or Balearic endemics) shows the presence of luteolin, apigenin, acacetin, genkwanin, 6-hydroxyluteolin, xanthomicrol, cirsimaritin; four partially identified flavones, of which three are 6-OR-substituted and one flavonol. The differences observed between T. capitatus (L.) Hoffmanns. et Link (subgenus Coridothymus (Reichenb. fil.) Borbás) and the other species belonging to the subgenus Thymus (L.) Jalas, seem enough to maintain the separation of the two groups, but within the same genus, as proposed in Flora Europaea. 相似文献
96.
Bactericidal activity of tuftsin 总被引:2,自引:0,他引:2
Summary The biological activities of the phagocytosis stimulating tetrapeptide, Thr-Lys-Pro-Arg are discussed. A brief account on the stimulation by tuftsin of phagocytosis of various particles, including bacteria was reported. Stimulation of bactericidal activity by this tetrapeptide was investigated in vitro as well as in vivo. The potency of tuftsin to enhance blood clearing of Staphylococcus aureus, Listeria monocytogenes, Escherichia coli and Serratia marcescens by mouse peritoneal macrophages was demonstrated.Bactericidal activity and effects of tuftsin on this phenomenon were studied in liver and spleen of mice. Tuftsin stimulates these activities. Same experiments were performed in infected leukemic mice by Serratia marcescens or Escherichia coli. Results on blood clearing and bactericidal activities in liver and spleen were reported and compared to those of healthy and leukemic untreated animals. Tuftsin was found to present interesting stimulatory effects on the bactericidal activity of phagocytes. 相似文献
97.
A. Martinez F. Argüelles J. Cervera F. Gomar 《Virchows Archiv. B, Cell pathology including molecular pathology》1977,23(1):53-64
35S sulfate uptake by the articular cartilage chondrocytes, from biopsies of rabbit, have been studied by high resolution autoradiography. The Golgi apparatus, rough endoplasmic reticulum, cytosol, cytoplasmic membrane and extracellular space were considered as cell compartments in the quantitative analysis of the autoradiograms. The results obtained show: 1) a high activity of radiosotope incorporation in the Golgi apparatus; 2) a fast rhythm of transfer of the substances labelled in the Golgi apparatus to the cell membrane; 3) significant labelling of the rough endoplasmic reticulum, throughout the experiment. It is concluded: 1) The grains observed in the rough endoplasmic reticulum show a significant radioisotope uptake on this level, and this evidence some sulfotransferase activity. 2) The high 35S sulfate uptake level which is observed in the Golgi apparatus demonstrates that the highest sulfotransferase enzyme activity is located in this cell area, thus showing that the "early" sulfation that began in the rough endoplasmic reticulum was completed by a "late" sulfation in the Golgi apparatus. It is here that complete chondromucoprotein building takes place before being excreted. 3) The high transfer level of the labelled substances from the Golgi apparatus shows that the sulfated product secretion for building the cartilage matrix takes place rapidly since a great label increase can be already observed at the beginning of the chase period in the outer surrounding area of the chondrocyte membrane. 相似文献
98.
99.
Howard T. Dulmage Harry M. Graham Eduardo Martinez 《Journal of invertebrate pathology》1978,32(1):40-50
Larvae of the tobacco budworm, Heliothis virescens, which were fed ad libitum for 24, 48, and 72 hr on a diet treated with various levels of the δ-endotoxin produced by the HD-1 isolate of Bacillus thuringiensis var. kurstaki and then transferred to an untreated diet, showed an unexpected capacity to recover from the effects of the toxin, although, as the length of exposure increased, the capacity decreased. Observations on larvae held to emergence indicated that recovery from the toxin was complete. X-ray studies using Ba2+ incorporated into the diet showed that, although the toxin paralyzed the midgut of the treated animals, many animals recovered after the toxin was removed, with food once again passing through the gut. 相似文献
100.
The morphology of conidia in 211 species and 12 varieties belonging to the genus Penicillium Link ex Gray have been studied and compared.According to surface ornamentation, conidia have been classified into six groups: A, smooth-walled (7% of the species); B, delicately roughened (13%); C, warty (28%); D, echinate (10%); E, striate with low irregular ridges (36%); and F, striate with scarce high ridges or bars (6%). Whereas the first two groups are closely related in both shape and average size, a gradual reduction was observed in size and in the length/width (l/w) ratio in the remaining groups. Echinate conidia were globose, having the largest average size. Only four species produced conidia not surpassing 2 m in diameter. Maximum length observed was 8 m, and most elongated conidia had a l/w ratio of 3.5. Forty per cent of the species studied had globose conidia.Conidia of the monoverticillate species were generally smaller, more globose and frequently with ridges. In the Asymmetrica, the conidia were generally larger, and showed ridges in comparatively few species. Conidia of the Symmetrica, which were frequently striate with ridges, presented the most elongated forms. The largest average size was found in the conidia of the Polyverticillata which were generally warty. Finally, we have considered the variations in surface ornamentation of conidia during the evolution of the genus Penicillium and drawn attention to their possible relationship with certain habitats and ways of conidial dispersion. 相似文献