全文获取类型
收费全文 | 5823篇 |
免费 | 389篇 |
国内免费 | 3篇 |
出版年
2023年 | 30篇 |
2022年 | 61篇 |
2021年 | 131篇 |
2020年 | 91篇 |
2019年 | 104篇 |
2018年 | 179篇 |
2017年 | 161篇 |
2016年 | 225篇 |
2015年 | 299篇 |
2014年 | 290篇 |
2013年 | 448篇 |
2012年 | 476篇 |
2011年 | 528篇 |
2010年 | 343篇 |
2009年 | 260篇 |
2008年 | 300篇 |
2007年 | 288篇 |
2006年 | 271篇 |
2005年 | 222篇 |
2004年 | 191篇 |
2003年 | 191篇 |
2002年 | 166篇 |
2001年 | 55篇 |
2000年 | 54篇 |
1999年 | 35篇 |
1998年 | 47篇 |
1997年 | 47篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 38篇 |
1993年 | 47篇 |
1992年 | 37篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 28篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 17篇 |
1978年 | 17篇 |
1977年 | 15篇 |
1976年 | 15篇 |
1975年 | 13篇 |
1974年 | 21篇 |
排序方式: 共有6215条查询结果,搜索用时 15 毫秒
101.
102.
Dagmar Jičínská Eduard Brabec Marcel Rejmánek Jan Jeník Joří Haager Josef Holub Věroslav Samek Hana Rambousková Josef Holub Marie Naděžda Končalová Robert Neuhäusl Josev Kyncl František Krahuleo Jaroslav Dobrý Blanka Úlehlová Jiří Úlehla Eliška Rybníčková Kamil Rybníček 《Folia Geobotanica》1982,17(4):431-448
103.
104.
105.
106.
A series of recessive mutations which arrest embryonic development are located within the T/t region of chromosome 17 in the mouse. To assess whether these mutations cause death in specific differentiating cells or in all cells of the embryo, we removed the embryonic cells from normal developmental constraints and attempted to grow them ectopically in vivo and in vitro. We have succeeded in producing teratomas and teratocarcinomas by transplantation of inner cell masses from blastocysts of and genotypes. The ability of embryonic cells to grow as tumors was not affected by their genotype; 7 of the 17 tumors were homozygous for tw12, 7 were heterozygous, and 3 could not be analyzed. Virtually all the tumors of both genotypes contained derivatives of all three germ layers. Neuroepithelial and mature nervous tissue was present in all homozygous tumors and all except one heterozygous tumor. However, no cartilage or bone was found in 5 of 5 tw12 homozygous tumors, while both tissues were present in 3 of 4 tw12 heterozygous tumors. This observation is compatible with the abnormalities characteristic of embryos, which show very localized effects in nervous tissue and more general effects on bone and cartilage formation. Cells derived from homozygous tumors were capable of at least limited growth in culture and a cell line has been derived from one of them. The p63/6.9a marker protein was used to determine the presence of the tw12 haplotype in the tumor and cultured cells. We conclude that the lethality associated with the tw12 haplotype is due to lethality of specific cells, and not all cell types. 相似文献
107.
Simultaneous induction of two enzymes sensitive to catabolite repression does not lead to an additive decrease of the specific activity of the two. Exogenously added cAMP increases the specific activity of catabolically repressed enzymes, irrespective of whether the enzyme is induced separately or simultaneously with another enzyme. In the presence of 12 different substrates metabolized by inducible enzymes glucose does not bring about catabolite repression. Synthesis of cAMP is identical with that occurring under conditions when glucose brings about catabolite repression. 相似文献
108.
Mutants ofOudemansiella mucida, blocked in the biosynthesis of the antibiotic mucidin, were obtained at a 0.28 % frequency after the application of N-methyl-N’-nitro-N-nitrosoguanidine (MNG) to basidiospores under conditions leading to 0.5–5.0 % survival rates. Loss of antibiotic activity was in most isolates accompanied by a decrease in mycelium growth rate and a suppression of dikaryotizing and fructification ability. Recombination analysis of two stable mutants revealed that the block in mucidin synthesis is the result of mutation in the same chromosomal gene(muc). In contrast to the action of MNG, UV-irradiation leads neither to the loss of biosynthetic activity nor to any morphological change. 相似文献
109.
Summary The cycling of cadmium and mercury between substrate and fruiting bodies in a model system with wood colonizing basidiomycete Agrocybe aegerita was studied. When radiolabeled 109CdCl2 and 203HgCl2 were applied to the fruiting bodies of the first flush, they were translocated via substrate into successive harvests. Cadmium and mercury displayed different patterns of distribution in the system. On a percent basis, more cadmium went from the fruiting bodies into the substrate and was retained there. Only minor portions of the metal were translocated into consecutive crops. In contrast, more mercury was retained in the treated fruiting bodies. The fraction which had penetrated into the substrate, however, was more easily translocated into fruiting bodies of successive crops. When calculated on a dry weight basis, the amount of both metals decreased in consecutive harvests.At the end of the experiment, in following distribution patterns for cadmium and mercury were observed: Cd2+: first crop (treated), 9.5%; substrate, 77%; combined successive crops (untreated), 9.5%; Hg2+: first crop (treated), 36.5%; substrate 21.5%; combined successive crops (untreated), 37%. The patterns reveal that mercury is more mobile in the substrate and therefore more easily translocated to successive fruiting body generations. Hence, from a nutritional point of view, mercury would seem to be more hazardous than cadmium. 相似文献
110.
Hormonal control of uteroglobin secretion in rabbit uterus. Inhibition of uteroglobin synthesis and messenger ribonucleic acid accumulation by oestrogen and anti-oestrogen administration
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Helena T. Kopu Seija M. Hemminki Tuula K. Torkkeli Olli A. J?nne 《The Biochemical journal》1979,180(3):491-500
Investigations were conducted to quantify activity of uteroglobin mRNA and secretion of uteroglobin in rabbit uterus after administration of progesterone and 5alpha-dihydrotestosterone, either alone or concomitantly with oestradiol-17beta and tamoxifen, a non-steroidal anti-oestrogen. Poly(A)-containing mRNA was isolated from the uterine tissue by extraction with phenol/chloroform, precipitation with ethanol and chromatography on oligo(dT)-cellulose. Cell-free translation in vitro of the poly(A)-containing mRNA was carried out in a wheat-germ lysate, and the product isolated by specific immuno-precipitation with anti-uteroglobin antiserum purified by affinity chromatography. Radioimmunoassay was utilized to determine uteroglobin content in the uterine flushings and tissue preparations. When given for 5 days, both progesterone (1mg/kg per day) and 5alpha-dihydrotestosterone (25mg/kg per day) elicited a marked induction of uteroglobin secretion, which was accompanied with accumulation of uteroglobin mRNA in the tissue. Concomitant administration of oestradiol-17beta (50mug/kg per day) or tamoxifen (12.5mg/kg per day) significantly decreased both progesterone- and 5alpha-dihydrotestosterone-induced uteroglobin secretion, with a parallel decrease in the uteroglobin-mRNA activity. The decline in the uteroglobin content of the uterine flushes brought about by oestradiol-17beta or tamoxifen administration was not due to inhibition of secretion of this protein by the endometrial cells, since a simultaneous decrease occurred in the tissue uteroglobin content. After a 5-day pretreatment with progesterone (1mg/kg per day), administration of oestradiol-17beta (50mug/kg per day) during the ensuing 4 days greatly accelerated the decay of the uteroglobin content in the uterine fluid. 相似文献