全文获取类型
收费全文 | 6236篇 |
免费 | 447篇 |
国内免费 | 1篇 |
出版年
2024年 | 5篇 |
2023年 | 49篇 |
2022年 | 52篇 |
2021年 | 232篇 |
2020年 | 140篇 |
2019年 | 186篇 |
2018年 | 190篇 |
2017年 | 195篇 |
2016年 | 278篇 |
2015年 | 397篇 |
2014年 | 405篇 |
2013年 | 473篇 |
2012年 | 553篇 |
2011年 | 532篇 |
2010年 | 326篇 |
2009年 | 285篇 |
2008年 | 360篇 |
2007年 | 357篇 |
2006年 | 312篇 |
2005年 | 267篇 |
2004年 | 232篇 |
2003年 | 201篇 |
2002年 | 176篇 |
2001年 | 51篇 |
2000年 | 43篇 |
1999年 | 54篇 |
1998年 | 48篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 19篇 |
1991年 | 22篇 |
1990年 | 8篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1979年 | 7篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 4篇 |
1971年 | 7篇 |
1970年 | 4篇 |
排序方式: 共有6684条查询结果,搜索用时 24 毫秒
21.
In negatively photoblastic seeds of Cucumis anguria L. the scarification of micropyle overcame the inhibitory effect of “white
light ”, although far-red radiation inhibited the germination in both intact and scarified seeds. The moistened testa powder
transmitted more far-red than red radiation. Thus the testa could act as a filter of radiation and maintain a high far-red/red
ratio at the photosensitive site of the embryo, which must be localized near the micropyle. 相似文献
22.
Daniel Chappard Christian Alexandre Sabine Palle George Riffat 《Biotechnic & histochemistry》1986,61(2):93-96
Polyester fibers are not dissolved by either glycol methacrylate or methyl methacrylate. Commercial polyester wadding is consequently an advantageous material to use in getting precise orientation of tissue specimens during embedding in methacrylate. 相似文献
23.
Daniel Chappard Christian Alexandre Sabine Palle Georges Riffat 《Biotechnic & histochemistry》1986,61(3):145-149
A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method. 相似文献
24.
25.
A one-step clearing and embedding procedure for alizarin red S stained skeletons is described. Embryos are fixed in formalin, skinned and eviscerated. After staining in a 10 mg/liter solution of alizarin red S in 5% aqueous KOH, specimens are dehydrated in a graded series of acetone-polyester monomer solutions. Finally, the specimens are embedded at room temperature in the polyester resin. A special reusable metallic mold is described for embedment of large fetuses. Specimens previously cleared in glycerol can be processed with this method. 相似文献
26.
27.
Location,structure and behaviour of C-heterochromatin during meiosis in Dichroplus silveiraguidoi (Acrididae-Orthoptera) 总被引:1,自引:0,他引:1
The constitutive heterochromatin of Dichroplus silveiraguidoi, a species which shows an exceptionally low chromosome number (2n=8), was studied at meiosis with a staining technique on normal and hypotonically treated specimens. The results showed: 1) an unusual behaviour of the heterochromatic blocks located in the so-called synaptic region of the sex bivalent (Neo Y-Neo X), which remains paired from early prophase through metaphase I; 2) in normal or in hypotonically treated cells a heterogeneous configuration of the C-heterochromatic blocks was observed. This configuration is characterized by the existence of small positive granules interconnected by euchromatic filaments and is enhanced by treatment with a low ionic strength solution; 3) A weakly positive stained (intermediate) material was demonstrated in the Neo X chromosome; 4) A large amount of heterochromatin is distributed in the form of granular material along the length of the autosomes and as telomeric and centromeric blocks in all chromosomes. The possible evolutionary mechanisms involved and the significance of the C-band heterochromatin demonstrated in this species are discussed. 相似文献
28.
29.
Effect of human T-cell leukemia virus type I tax protein on activation of the human vimentin gene. 总被引:28,自引:9,他引:19 下载免费PDF全文
We report that the expression of the vimentin gene, a cytoskeletal growth-regulated gene, is activated in trans by the Tax (p40x) transactivator protein encoded by the human T-cell leukemia virus type I. Expression of the Tax protein activates a number of cellular genes, such as those coding for the alpha chain of the high-affinity interleukin-2 receptor and interleukin-2. These findings indicate that the Tax protein is involved in the unregulated T-cell growth associated with human T-cell leukemia virus type I infection. Higher levels of vimentin mRNA were expressed in two human T-cell leukemia virus type I-transformed T cell lines, C91/PL and C81-66/45, when compared with that in Jurkat T cells. We demonstrate that this activation is conferred by the vimentin upstream flanking sequences. Indeed, enhanced activity was detected when constructs with the vimentin promoter linked to the chloramphenicol acetyltransferase gene were transfected in HeLa cells and in two cell lines of hematopoietic origin (Jurkat T lymphoblastoid cells and U937 promonocytic cells) together with a Tax expression plasmid. By introducing a series of deletions in the vimentin promoter, we further restrict these sequences to 30 base pairs, located between 241 and 210 base pairs upstream of the mRNA cap site. A 40-base-pair oligonucleotide containing this regulatory region proved sufficient to confer Tax inducibility upon a heterologous promoter linked to chloramphenicol acetyltransferase. Importantly, this segment includes an 11-base-pair promoter segment that has homology with the binding site for the NF-kappa B transactivating factor. Our findings indicate that constitutive expression of the vimentin gene under the control of the Tax protein may be relevant in understanding the progression of the lymphoproliferative process associated with human T-cell leukemia virus type I infection. 相似文献
30.