全文获取类型
收费全文 | 2562篇 |
免费 | 83篇 |
国内免费 | 1篇 |
出版年
2023年 | 23篇 |
2021年 | 22篇 |
2018年 | 69篇 |
2017年 | 69篇 |
2016年 | 72篇 |
2015年 | 89篇 |
2014年 | 98篇 |
2013年 | 125篇 |
2012年 | 129篇 |
2011年 | 117篇 |
2010年 | 110篇 |
2009年 | 71篇 |
2008年 | 39篇 |
2007年 | 39篇 |
2006年 | 37篇 |
2005年 | 143篇 |
2004年 | 108篇 |
2003年 | 83篇 |
2002年 | 24篇 |
2001年 | 31篇 |
1999年 | 21篇 |
1998年 | 21篇 |
1996年 | 27篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 34篇 |
1990年 | 26篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 25篇 |
1985年 | 28篇 |
1984年 | 37篇 |
1983年 | 41篇 |
1982年 | 28篇 |
1981年 | 31篇 |
1980年 | 32篇 |
1979年 | 59篇 |
1978年 | 31篇 |
1977年 | 24篇 |
1976年 | 24篇 |
1975年 | 35篇 |
1974年 | 33篇 |
1973年 | 31篇 |
1972年 | 31篇 |
1971年 | 21篇 |
1970年 | 24篇 |
1969年 | 35篇 |
1966年 | 23篇 |
排序方式: 共有2646条查询结果,搜索用时 15 毫秒
31.
Antonín Vězda 《Folia Geobotanica》1987,22(1):71-83
Nine species ofByssoloma Trevisan (Pilocarpaceae) are reported from a collection of foliicolous lichens from Zaire, and includeB. murinum sp. n. In addition,B. usambarense sp. n. is described from adjacent Tanzania. A determination key is provided to all the known African species, and each species is briefly characterized. 相似文献
32.
Jan Kopecký Josef Houštěk Eva Szarska Zdeněk Drahota 《Journal of bioenergetics and biomembranes》1986,18(6):507-519
The proteolipid subunit of H+-ATPase was labeled by [14C]N,N-dicyclohexylcarbodiimide in bovine heart mitochondria. The radioactive labeling was followed using various systems of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). When using discontinuous SDS-PAGE (Laemmli, U.K., 1970,Nature (London)227, 680–685) a monomeric (Mr 7600±1500) and a dimeric form (Mr 17,800±1200) of the proteolipid were detected, while only the monomeric form was found on urea (8 M) containing gels (SDS-PAGE according to Laemmli; or Swank, R. T., and Munkers, K. D., 1971,Anal. Biochem.
39, 462–477). When using SDS-PAGE with Na-Pi buffer (Weber, K., and Osborn, M., 1969,J. Biol. Chem.
244, 4406–4442), only a dimeric form of the proteolipid (Mr 15,000±1000) was detected. Experimental data indicate that the different patterns of proteolipid separation are related to the presence of the two distinct proteolipid conformations in the SDS solution. 相似文献
33.
The relationship between the activity of ATC oxygenase, CTC production and growth rate was investigated in a low-producing
strain ofStreptomyces aureofaciens, closely related to the wildtype strain, and in a higher-producing variant. Different growth rates were achieved by using
glucose, fructose and sucrose as carbon sources. Activity of the enzyme and CTC yield in both strains were inversely proportional
to the rate of sugar utilization but in the higherproducing variant sugar utilization was slower than in the low-producing
strain. The expression of ATC oxygenase was less sensitive to “catabolite repression” in the higherproduc ing strain. BT,
a stimulator of CTC production, markedly inhibited growth of the higher-producing variant in a medium with slowly utilized
sugars (fructose and sucrose) but had little effect on growth of the lowproducing strain. It also increased the level of ATC
oxygenase in both strains under all experimental conditions. It could be established that there was no obligatory relationship
between the increase of antibiotic synthesis and the increase of enzyme activity. 相似文献
34.
Agrobacterium radiobacter, strain B6 (a strain isolated in this laboratory, which limited the occurrence of damping-off of sugar beet and influenced growth of plants in hot-house and field experiments) was found to produce an acidic exopolysaccharide in a mineral medium with various carbon sources. Hydrolyzates of the polysaccharide contained glucose, galactose, glycerol, succinic acid and pyruvic acid, whose quantitative content varied according to the carbon source used. The polysaccharide isolated from the medium containing glucose exhibited the highest physiological activity. Seeds germinated best and sugar beet roots were found to grow most rapidly in a medium containing 0.2 % (W/W) of the polysaccharide. The roots exposed for 3 d in this medium grew 2.7-fold as compared with non-treated plants. Higher sumbers of microorganisms were detected on the surface of roots treated with the polysaccharide. Growth of roots was also stimulated when immersing the seeds (30 min) in a 0.2 –0.4 % solution of this polysaccharide. After a two-fold treatment the roots were less damaged by the fungusPythium ultimum. Plants from seeds treated with the polysaccharide grew in the field soil more rapidly than the non-treated plants but worse than after bacterization of the seeds byA. radiobacter B6 and were only partially protected against the damping-off of sugar beet. 相似文献
35.
Oudin’s principle of single immunodiffusion in agar gel was modified for quantitative determination of IgA in bronchoalveolar lavage (BAL) of normal 20–25 g mice. The reaction took place at 25 °C in 0.3 % agarose with 16.7 % pig serum against mouse IgA, and was evaluated on the basis of a relationship between the progress of the precipitin zone and the square root of time. The linear dependence of the derived constantk on the logarithmic concentration of antibody in the sample permitted to express the results as titre, corresponding to a dilution wherek = 0. Examination of seven samples of pooled blood serum of normal mice shoved taht (1) the IgA level was practically constant, (2) serum IgA possessed under given conditions similar properties as IgA from the bronchoalveolar secretion; it is therefore possible to employ pooled sera as a reliable control of the immunodiffusion system in ease of lack of reference standards with defined IgA content. Examination of 82 individual BAL samples of normal mice revealed that the mean IgA concentration in 2.5 mL samples was almost 1000 times lower than in blood serum. 相似文献
36.
Foreign proteins penetrate across the wall of rabbit jejunum takes place within the first eight hours after birth. Sensitization by foreign protein (cow's milk protein) during early postnatal ontogeny is the cause of death of artificially fed germfree rabbits at the age of 21-23 d. 相似文献
37.
Vera Hadačová Květa Vacková Eva Klozová M. Kutáček Květa Pitterová 《Biologia Plantarum》1983,25(3):209-215
In partly purified protein complexes obtained from 22 species of theAllium genus and 6 cultivars ofAllium cepa the activity of cholinesterases was detected and measured using the method of Ellman et al. The degree of its inhibition with 10-4 M neostigmine was also tested. It was found that the activity of cholinesterase differed in individual species up to two hundred times, while the differences in the inhibitory activity of 10-4 M neostigmine occurred only in a few cases. Individual sections and cultivars could not be characterized on the basis of the differences in the activities of the cholinesterases. Of all the sections that ofPhyllodolon shows the highest average activity. In the case of the tested cultivars distinctly the lowest activity was observed in cv. Kastická. The values of the enzymatic activity measured by Ellman’s method in this plant material include the activity of specific and unspecific cholinesterases and the part uninhibitable by neostigmine. 相似文献
38.
Total and polysome-bound ribosomes and the uptake and incorporation of3H-uridine and14C-leucine were examined in dividing microspores and in pollen grains isolated from anthers of 6 different developmental stages. Direct evidence was obtained that the formation of cytoplasm of the vegetative cell following microspore division is related to a rapid activation of RNA and protein synthesis and of ribosomes in differentiating pollen. Total ribosomes associated with gametophytic programme rose about 10times and the process of differentiation was accompanied by a rapid increase in uptake capacity of pollen grains for both uridine and leucine. Pollen development after cytoplasm synthesis and starch deposition continued by pollen maturation, which was characterized by a decline in RNA synthesis, dissociation of polysomes and by a further rise of transport activity of pollen grain wall for exogenous substrates, indicating probable pollen adaptation for utilization of metabolites from the degenerating tapetal cytoplasm. 相似文献
39.
Eva Klozová Jiřina Švachulová J. Smartt E. Hadač Věra Turková Véra Hadačová 《Biologia Plantarum》1983,25(4):266-273
The seed protein patterns of 12Arachis species were compared by polyacrylamide gel electrophoresis (PAGE), similarities between patterns were measured by the Jaccard
index. Results obtained confirm the close relationships established between members of the genus on morphological grounds
and support the more recent classification schemes.A. villosa andA. correntina could well be regarded as distinct species on grounds of protein differences whileA. macedoi andA. villosulicarpa (although members of the same section, Extranervosae) show considerable differentiation of their protein patterns. Surprisingly,
the formA. ×batizogaea showed less similarity in protein pattern to those of its parental species than might have been expected. The principle value
of seed protein pattern data appears to be in distinguishing species within sections. 相似文献
40.