全文获取类型
收费全文 | 441篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
471篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 19篇 |
2012年 | 29篇 |
2011年 | 21篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 13篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1967年 | 3篇 |
1963年 | 2篇 |
排序方式: 共有471条查询结果,搜索用时 15 毫秒
411.
CH. Fuchs 《Biotechnic & histochemistry》1963,38(3):141-144
Three methods that are adapted to the various consistencies of plants are as follows: 1. Samples are placed for 10-14 hr at 60° C in a 1% aqueous solution of basic fuchsin, to which 10 gm of solid NaOH per 100 ml are added. 2. Samples when taken out of 95% alcohol are placed in a 1% solution of basic fuchsin in 95% alcohol for 24 hr; after washing in water, they are placed in a 15% solution of NaOH at 60° C until cleared. 3. Samples are placed in a 15% aqueous solution of NaOH at 60° C until cleared, then for 24 hr at 60° C in 15% NaOH containing basic fuchsin. After being stained and cleared by one of these three methods, the samples are rinsed in water, dehydrated and then passed into a mixture of absolute alcohol and concentrated HC1 (3:1) for 1-15 min, rinsed in absolute alcohol, cleared in xylene and mounted in Canada balsam. The lignified tissues appear red; the others, transparent. 相似文献
412.
E. Xirouchaki P. Vassiliadis D. Trichopoulos CH. Mavrommati 《Journal of applied microbiology》1982,52(1):125-127
Salmonellas were isolated from meat products using a slightly modified Rappaport's enrichment medium (R25), Rappaport-Vassiliadis procedure (Rappaport's broth containing 10 ml instead of 30 ml of Malachite Green solution and incubated at 43o C instead of 37o C), and Muller-Kauffmann's tetrathionate broth. From 255 samples, 89 were found positive with the Rappaport-Vassiliadis procedure, 83 with the R25 broth, whereas only 43 were positive with Muller-Kauffmann broth. It is concluded that the R25 medium may be used as an alternative to the more effective Rappaport-Vassiliadis broth when the only available incubation temperature is 37o C. 相似文献
413.
An energy budget was constructed for A. fabae reared on synthetic diets and compared with that published for aphids living on broad bean. Larval aphids living on broad bean utilized 54% of their energy intake for growth, 4% was lost during respiration and 42% was excreted as honeydew. Aphids living on a synthetic diet utilized 26% of their energy intake for growth and 4% was lost during excretion. 76% was excreted as honeydew. The growth efficiency on a synthetic diet was 20% compared with a value of 50% on plants. The value of synthetic diet experiments in furthering our understanding of aphid nutrition is discussed in the light of these results.
Résumé Les budgets énergétiques d'Aphis fabae élevé sur des aliments artificiels ont été établis. Du 14C radioactif a été ajouté aux aliments pour faciliter l'évaluation de la quantité ingérée. Au cours des quatre premiers jours de la vie larvaire le puceron utilise pour sa croissance 0.82 Joules de l'énergie absorbée; les exuvies représentent 0.26 Joules, la respiration 0.16 Joules et l'équivalent de 2.97 Joules sont excrétés sous forme de miellat. Le rendement de croissance est de 20% et la croissance larvaire est de 0,037 mg en poids sec/jour. Ces données sont comparées avec celles obtenous pour des aphides vivant sur fève.Ces pucerons élevés sur fève ont un rendement de croissance de 50% et la croissance larvaire est de 0,056 mg en poids sec/jour. Les pucerons élevés sur milieux artificiels montrent donc une diminution appréciable de leur rendement de croissance et de leur vitesse de croissance, ce qui conduit à discuter les implications de ces observations pour les études nutritionnelles des aphides.相似文献
414.
1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO2 . We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula ) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius ) of elevated CO2 treatment ( c. 700 μl litre–1 ) under mean QFD of less than 11 μmol m–2 s–1 , all species produced more biomass (25–76%) under elevated CO2 .
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m–2 s–1 ) but the relative stimulation by elevated CO2 was higher at low QFD except in Pharus .
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO2 . An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO2 continues to rise. 相似文献
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO
415.
Overexpression of calreticulin fails to abolish its induction by perturbation of normal ER function.
Along with other endoplasmic reticulum (ER) Ca2+-binding proteins, notably the glucose-response proteins grp78 and grp94, expression of calreticulin is induced in response to perturbation of normal ER function. It has yet to be clearly defined how this stress is signaled from the ER to the nucleus in mammalian cells, particularly with regard to its initiation. Using a GFP-calreticulin fusion protein, we have generated and selected stably transfected HeLa cells that overexpress calreticulin to investigate whether the protein might be involved in signaling its own induction. Basal levels of endogenous calreticulin mRNA and protein were unaffected in these cells, indicating that overexpression alone does not induce a stress response. ER stress induced calreticulin expression in response to either thapsigargin or tunicamycin was equivalent in these cells to that seen in control, nontransfected cells, leading us to conclude that calreticulin is unlikely be involved in its own induction. Levels of the mRNA encoding the fusion protein were also increased by tunicamycin, but not thapsigargin, suggesting that, in agreement with our previous observations, inhibition of N-linked glycosylation may increase the stability of calreticulin mRNA. This indicates that in mammalian cells, there is more than one signaling pathway for the ER stress response. 相似文献
416.
人肾上腺内肽能神经的超微结构 总被引:1,自引:0,他引:1
殷树仪 《中国组织化学与细胞化学杂志》1994,(1)
应用抗生蛋白链菌素一生物素一过氧化物酶复合物的免疫电镜技术,在相邻切片中,分别观察人肾上腺内NPY、VIP、SP和CGRP免疫反应神经纤维的超微结构和免疫反应物的定位。NPY和VIP免疫反应物位于小颗粒羹泡和线粒体外膜,部分嗜铬细胞呈NPY免疫反应阳性。SP和CGRP免疫反应物主要定位于大颗粒囊泡内。SP和CGRP免疫反应轴突与嗜铬细胞形成对称性或非对称性的轴体突轴。测量了这4种肽能神经末梢的直径,从而推测其来源,并讨论了该4种神经肽对人肾上腺的作用。 相似文献
417.
418.
Linkage disequilibrium between DNA polymorphisms within the porphobilinogen deaminase gene 总被引:1,自引:1,他引:0
G. A. Scobie A. J. Urquhart G. H. Elder N. A. Kalsheker D. H. Llewellyn J. Smyth P. R. Harrison 《Human genetics》1990,85(2):157-159
Summary Three restriction fragment length polymorphisms (RFLPs) (MspI, PstI, ScrFI/BstNI) within the human porphobilinogen deaminase (PBG-D) gene have been studied in 47 unrelated patients with the autosomal dominant disorder, acute intermittent porphyria (AIP), and in 92 control subjects. Each enzyme identified a two-allele polymorphism with allele frequencies close to 0.50; however, marked linkage disequilibrium limited the number of observed haplotypes to four, of which one is uncommon. No association was detected between any haplotype and AIP. 相似文献
419.
Restriction-map variation at the zeste-tko region in natural populations of Drosophila melanogaster 总被引:4,自引:0,他引:4
Restriction-map variation in 64 X chromosome lines extracted from three
different natural populations of Drosophila melanogaster was investigated
with seven six-nucleotide-recognizing enzymes for a 20-kb region including
the zeste and tko genes. Ten restriction-site and four length polymorphisms
(two insertions and two deletions) were detected. Contrary to the predicted
lower level of variation for genes on the X chromosome, the level of
variation attributable to nucleotide substitution (estimated
heterozygosity/nucleotide = 0.004) was similar to that previously reported
for autosomal loci. The amount of insertion/deletion variation in the
studied region was within the range observed in autosomal regions and thus
not explainable by a simple selection model against the effects of
insertional mutations. A general lack of linkage disequilibrium between
polymorphic sites was observed.
相似文献
420.
McVay JD Rodriguez D Rainwater TR Dever JA Platt SG McMurry ST Forstner MR Densmore LD 《Journal of experimental zoology. Part A, Ecological genetics and physiology》2008,309(10):643-648
Microsatellite data were generated from hatchlings collected from ten nests of Morelet's Crocodile (Crocodylus moreletii) from New River Lagoon and Gold Button Lagoon in Belize to test for evidence of multiple paternity. Nine microsatellite loci were genotyped for 188 individuals from the 10 nests, alongside 42 nonhatchlings from Gold Button Lagoon. Then mitochondrial control region sequences were generated for the nonhatchlings and for one individual from each nest to test for presence of C. acutus-like haplotypes. Analyses of five of the nine microsatellite loci revealed evidence that progeny from five of the ten nests were sired by at least two males. These data suggest the presence of multiple paternity as a mating strategy in the true crocodiles. This information may be useful in the application of conservation and management techniques to the 12 species in this genus, most of which are threatened or endangered. 相似文献