全文获取类型
收费全文 | 19242篇 |
免费 | 1752篇 |
国内免费 | 143篇 |
专业分类
21137篇 |
出版年
2023年 | 98篇 |
2022年 | 169篇 |
2021年 | 287篇 |
2020年 | 196篇 |
2019年 | 271篇 |
2018年 | 367篇 |
2017年 | 310篇 |
2016年 | 489篇 |
2015年 | 761篇 |
2014年 | 827篇 |
2013年 | 1001篇 |
2012年 | 1237篇 |
2011年 | 1133篇 |
2010年 | 724篇 |
2009年 | 642篇 |
2008年 | 857篇 |
2007年 | 886篇 |
2006年 | 848篇 |
2005年 | 766篇 |
2004年 | 717篇 |
2003年 | 699篇 |
2002年 | 681篇 |
2001年 | 574篇 |
2000年 | 520篇 |
1999年 | 448篇 |
1998年 | 249篇 |
1997年 | 253篇 |
1996年 | 212篇 |
1995年 | 207篇 |
1994年 | 189篇 |
1993年 | 195篇 |
1992年 | 320篇 |
1991年 | 302篇 |
1990年 | 300篇 |
1989年 | 262篇 |
1988年 | 215篇 |
1987年 | 201篇 |
1986年 | 235篇 |
1985年 | 211篇 |
1984年 | 164篇 |
1983年 | 172篇 |
1982年 | 138篇 |
1981年 | 112篇 |
1980年 | 102篇 |
1979年 | 128篇 |
1978年 | 131篇 |
1977年 | 96篇 |
1975年 | 92篇 |
1974年 | 105篇 |
1972年 | 93篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
2.
3.
4.
5.
6.
On the mechanism of the light-induced activation of the NADP-dependent glyceraldehyde phosphate dehydrogenase 总被引:4,自引:0,他引:4
B Müller 《Biochimica et biophysica acta》1970,205(1):102-109
7.
Optimized linker sequences for the expression of monomeric and dimeric bispecific single-chain diabodies. 总被引:5,自引:0,他引:5
Bispecific single-chain diabodies (scDb) consist of the variable heavy and light chain domains of two antibodies connected by three linkers. The structure of an scDb in the V(H)-V(L) orientation is V(H)A-linkerA-V(L)B-linkerM-V(H)B-linkerB-V(L)A, with linkers A and B routinely chosen to be 5-6 residues and linker M 15-20 residues. Here, we applied display of scDb on filamentous phage to analyse the composition of optimal linker sequences. The three linkers were randomized in length and sequence using degenerated triplets coding for only six hydrophilic or aliphatic amino acids (Thr, Ser, Asp, Asn, Gly, Ala). Antigen-binding clones were then isolated by one to two rounds of selection on the two different antigens recognized by the bispecific scDb. Using an scDb directed against carcinoembryonic antigen (CEA) and beta-galactosidase (Gal), we found that monomeric scDb had a preferred length of 15 or more amino acid residues for the middle linker M and of 3-6 residues for the linkers A and B. No obvious bias towards a preferred linker sequence was observed. Reduction of the middle linker below 13 residues led to the formation of dimeric scDb, which most likely results from interchain pairing between all the V(H) and V(L) domains. Dimeric scDb were also formed by fragments possessing a long linker M and linkers A and B of 0 or 1 residue. We assume that these dimeric scDb are formed by intrachain pairing of the central variable domains and interchain pairing of the flanking variable domains. Thus, the latter molecules represent a novel format of bispecific and tetravalent molecules. The described strategy allows for the isolation of both optimized and minimal linker sequences for the assembly of monomeric or dimeric single-chain diabodies. 相似文献
8.
Carmen de Sena-Tomás Mónica Navarro-González Ursula Kües José Pérez-Martín 《Genetics》2013,195(1):47-57
The fungal fruiting body or mushroom is a multicellular structure essential for sexual reproduction. It is composed of dikaryotic cells that contain one haploid nucleus from each mating partner sharing the same cytoplasm without undergoing nuclear fusion. In the mushroom, the pileus bears the hymenium, a layer of cells that includes the specialized basidia in which nuclear fusion, meiosis, and sporulation occur. Coprinopsis cinerea is a well-known model fungus used to study developmental processes associated with the formation of the fruiting body. Here we describe that knocking down the expression of Atr1 and Chk1, two kinases shown to be involved in the response to DNA damage in a number of eukaryotic organisms, dramatically impairs the ability to develop fruiting bodies in C. cinerea, as well as other developmental decisions such as sclerotia formation. These developmental defects correlated with the impairment in silenced strains to sustain an appropriated dikaryotic cell cycle. Dikaryotic cells in which chk1 or atr1 genes were silenced displayed a higher level of asynchronous mitosis and as a consequence aberrant cells carrying an unbalanced dose of nuclei. Since fruiting body initiation is dependent on the balanced mating-type regulator doses present in the dikaryon, we believe that the observed developmental defects were a consequence of the impaired cell cycle in the dikaryon. Our results suggest a connection between the DNA damage response cascade, cell cycle regulation, and developmental processes in this fungus. 相似文献
9.
Self-splicing of group II introns in vitro: lariat formation and 3' splice site selection in mutant RNAs 总被引:10,自引:0,他引:10
Deletion or substitution of the branch A residue in group II intron bl1 significantly reduces splicing activity; yet, residual exon ligation is correct, and lariats have their branch points at the normal distance from the 3' end of the intron. Mutations in the sequence facing the branch point also allow residual lariat formation; however, free 3' exons are generated with false 5' termini, all of which are within a UCACA consensus sequence located upstream or downstream of the normal 3' splice site. These results indicate that both the conserved 3' splice site APy and the spatial arrangements in stem 6 are crucial for correct 3' splice site selection. 相似文献
10.
Marc Mercken Ursula Lübke Marc Vandermeeren Jan Gheuens A. Beate Oestreicher 《Developmental neurobiology》1992,23(3):309-321
The growth-associated protein B-50 also termed GAP-43, F1, pp46, P-57 and neuromodulin is a nervous tissuespecific protein kinase C (PKC) substrate that is considered to play a major role in neurite formation, regeneration, and neuroplasticity. We describe the isolation of seven mouse monoclonal antibodies (Mabs) directed against B-50. The Mabs are produced against the bovine B-50, selected by ELISA for cross-reactivity with its human counterpart, and evaluated on Western blots in comparison with the well-characterized affinity-purified rabbit polyclonal antibodies to rat-B-50. The Western blots show that the Mabs NM1, NM4, and NM6 recognize specifically the B-50 of bovine, human, and rat brain extract and the purified PKC phosphorylated and unphosphorylated rat B-50 isoforms. The Mabs NM2 and NM3 cross-react with bovine B-50 immunoreactive c-kinase substrate (BICKS), a protein sharing a 17 amino acid sequence homology with B-50. Two Mabs are useful for the detection of B-50 immunoreactivity in formalin-fixed human and rat brain tissues. In human specimen of the hippocampus, a characteristic neuropil distribution of B-50 is detected by the Mabs. In human muscle, Mabs reveal B-50 in nerve bundles and in axons at motor end plates. Thus, these Mabs are useful in investigating the function and localization of the B-50 protein. 相似文献