全文获取类型
收费全文 | 3380篇 |
免费 | 344篇 |
出版年
2023年 | 11篇 |
2022年 | 28篇 |
2021年 | 58篇 |
2020年 | 27篇 |
2019年 | 48篇 |
2018年 | 67篇 |
2017年 | 56篇 |
2016年 | 102篇 |
2015年 | 166篇 |
2014年 | 185篇 |
2013年 | 200篇 |
2012年 | 273篇 |
2011年 | 267篇 |
2010年 | 156篇 |
2009年 | 139篇 |
2008年 | 207篇 |
2007年 | 207篇 |
2006年 | 208篇 |
2005年 | 181篇 |
2004年 | 191篇 |
2003年 | 145篇 |
2002年 | 157篇 |
2001年 | 40篇 |
2000年 | 26篇 |
1999年 | 37篇 |
1998年 | 52篇 |
1997年 | 36篇 |
1996年 | 30篇 |
1995年 | 32篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 21篇 |
1991年 | 27篇 |
1990年 | 24篇 |
1989年 | 13篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 28篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 26篇 |
1978年 | 14篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 13篇 |
排序方式: 共有3724条查询结果,搜索用时 31 毫秒
41.
42.
We surveyed a French male population for the incidence of missing or reduced upper lateral incisors (ULI). In 5,738 subjects, we observed an incidence of 1.59% with one or two reduced ULI (the other normal) and 1.90% with one or two missing ULI (the other normal or reduced), altogether, 3.49% affected subjects. Furthermore, 250 random controls were observed. Agenesis of other teeth is more frequent in propositi. Missing third molars were 12.4% in controls, 24.0% in propositi with reduced ULI and 39.6% in propositi with two missing ULI. Furthermore, agenesis of incisors, canines and premolars ranges from 0.4% in controls to 1.3% in propositi having reduced ULI and 5.0% in propositi with two missing ULI. So, propositi with reduced ULI are intermediate between the controls and the propositi with missing ULI with respect to the frequency of agenesis of other teeth. On the other hand, a different ranking is observed with respect to the teeth measurements: reduction of tooth size is more marked in propositi with reduced ULI than in propositi with missing ULI. The reduction mainly affects canines, incisors and to a lesser degree, premolars. Arch length and interpremolar diameters are smaller in propositi with missing ULI, compared with controls. 相似文献
43.
R M Siervogel R C Elston R H Lester J B Graham 《American journal of human genetics》1979,31(2):199-213
Blood clotting factor ten (X) levels measured in 149 people in six pedigrees were found to fit a mixture of normal distributions. No environmental effect could be identified to account for the wide separation in the means of these distributions. Pedigree analysis reveals that the data are compatible with an autosomal, one locus, two allele genetic model affecting factor X activity. Goodness of fit tests suggest that the allele for low levels of factor X is dominant, though on the basis of likelihood tests, mean heterozygote levels are different from mean homozygote levels. A similar bimodal distribution for factor X levels observed previously in a separate sample of 207 young men, indicated that the proposed dominant allele has an estimated population gene frequency of .53. The earlier estimate is remarkably similar to that obtained with the currently ascertained pedigrees. The postulated major gene accounts for more than half of the variation in factor X levels. 相似文献
44.
Christiane Guguen-Guillouzo Marie-France Szanjnert Denise Glaiser Claudine Gregori Fanny Schapira 《In vitro cellular & developmental biology. Plant》1981,17(5):369-377
Summary Aldolase and pyruvate kinase isozymes were investigated in cultured hepatocytes from fetal, regenerating, and 2-acetyl-aminofluorene-fed
rat liver as well as in some epithelial liver cell lines. Our results show that: (a) cell proliferation and prolonged expression
of specific isozymes were found only in cultured hepatocytes from 17-day old fetuses; (b) the fetal type of pyruvate kinase
expressed in regenerating and carcinogen-treated liver was temporarily lost only in cultured hepatocytes from regenerating
liver; (c) the adult type of aldolase and pyruvate kinase was absent in one epithelial cell line derived from a carcinogen-treated
liver and in the hepatoma tissue cell (HTC) line but was found in the Faza clone of the Reuber H35 cell line during the 50 first passages in vitro; and (d) the isozyme pattern of pyruvate kinase was always more strongly
shifted than that of aldolase.
The observations suggest that: (a) hepatocytes from carcinogen-treated liver exhibit the same lack of ability to proliferate
in primary culture as normal adult hepatocytes; (b) adult hepatocytes can produce fetal isozymes without prior cell division;
(c) pyruvate kinase is a stronger marker of dedifferentiation (retrodifferentiation) than aldolase; and (d) regulatory processes
of isozyme expression are different during ontogenesis, regeneration, and hepatocarcinogenesis.
This work was supported by the “Institut National de la Santé et de la Recherche Médicale” and the “Fondation pour la Recherche
Medicale Fran?aise” 相似文献
45.
C-glycosylflavone accumulation in Sandoz 6706-treated barley seedlings is a photocontrolled response
Sandoz 6706 pretreatment of white light grown barley seedlings causes a 60% increase in saponarin (6-C-glucosyl-7-O-glucosylapigenin) but a 300% increase in lutonarin (3′-hydroxysaponarin). Norflurazon has little effect on saponarin levels but is almost as effective as Sandoz 6706 in enhancing lutonarin net synthesis. Barley roots contain saponarin and lutonarin only after herbicide treatment. Mung bean seedlings respond to Sandoz 6706 by accumulating higher levels of rutin and delphinidin 3-glucoside. The results are discussed in relation to the site of action of the herbicides, the High Energy photoresponse, and control of flavonoid 3′-hydroxylation. 相似文献
46.
47.
48.
Osvaldo A. Sant'Anna Olga M. Ibanez Vera C. A. Ferreira Marisa Gennari Denise Mouton 《Immunogenetics》1983,18(4):359-364
High (H/s) and low (L/s) antibody responder lines of mice selected according to their response to the somatic (s) antigen of Salmonella (Selection IV) have unexpected inverse capacity for antibody production to rabbit gamma globulin (RGG): H/s mice are low or even nonresponders to this antigen, whereas L/s mice are high responders. It was shown that the phenotypic variability within each line is due to environmental factors. RGG was a selection antigen in Selection V; the high (H/p) and low (L/p) responder mice are therefore considered as homozygous for the RGG genes. Responsiveness to RGG was investigated in F1 and F2 hybrids obtained by crossing the phenotypically similar RGG responder or nonresponder mice of Selections IV and V. The results support the hypothesis that the same genes control the response to RGG in L/s and H/p lines as well as in H/s and L/p lines. This means that the genes specific for RGG responsiveness were independent from those regulating responses to the s antigen. Unaffected by the selective breeding in Selection IV, they have been fixed by chance in an inverse way in H/s and L/s lines. 相似文献
49.
Denise K. H. Chou Nemani Prasadarao Omanand Koul Firoze B. Jungalwala 《Journal of neurochemistry》1991,57(3):852-859
Monoclonal antibody HNK-1 reacts with a carbohydrate epitope present in proteins, proteoglycans, and sulfoglucuronylglycolipids (SGGLs). On high-performance TLC plates, SGGLs of the CNS from several species migrated consistently slower than those from the PNS, a result indicating possible differences in the structures. The structural characteristics of the major SGGL, sulfoglucuronylneolactotetraosylceramide (SGGL-1), from CNS was compared with those of SGGL-1 from PNS. Although the composition, sequence, and linkages of the carbohydrate moiety of the SGGL-1 species were identical, SGGL-1 from CNS contained mainly short-chain fatty acids, 16:0, 18:0, and 18:1, amounting to 85% of the total fatty acids, whereas SGGL-1 from PNS contained large proportions (59%) of long-chain fatty acids (greater than 18:0). These differences in the fatty acid composition accounted for the different migration pattern observed. The developmental expression of SGGLs and HNK-1-reactive proteins was studied in rat cerebral cortex between embryonic day (ED) 15 to adulthood. SGGLs in the rat cortex were maximally expressed around ED 19 and almost completely disappeared by postnatal day (PD) 20. This expression was contrary to their increasing expression in the cerebellum and sciatic nerve with postnatal development. Six to eight protein bands with a molecular mass of greater than 160 kDa were HNK-1 reactive in the rat cerebral cortex at different ages. The major HNK-1 reactivity to the 160-kDa protein band seen in ED 19 to PD 10 cortex decreased and completely disappeared from the adult cortex, whereas several other proteins remained HNK-1 reactive even in the adult. Western blot analyses of the neural cell adhesion molecules (N-CAMs) during development of the rat cortex with a polyclonal anti-N-CAM antibody showed that the major HNK-1-reactive protein bands were not N-CAMs. Between PD 1 and 10, 190-200-kDa N-CAM was the major N-CAM, and between PD 15 to adulthood, 180-kDa N-CAM was the only N-CAM present in the rat cortex. 相似文献
50.
J S Elston 《Journal de physiologie》1990,84(4):285-289
The results of the treatment with botulinum toxin A injection of 234 patients with blepharospasm and 73 with hemifacial spasm were reviewed. Visual function improved in the majority of patients with blepharospasm, and the improvement was sustained for up to 40 sets of injections. Mid and lower facial movements were also reduced in a minority of patients. However, a sub-group with pre-tarsal blepharospasm or persistent levator inhibition after treatment had a poor response. An average 75% reduction in abnormal movements was seen in cases of hemifacial spasm. Side effects of the treatment were usually mild and short lived. 相似文献