全文获取类型
收费全文 | 8389篇 |
免费 | 401篇 |
国内免费 | 813篇 |
出版年
2024年 | 10篇 |
2023年 | 82篇 |
2022年 | 110篇 |
2021年 | 136篇 |
2020年 | 131篇 |
2019年 | 140篇 |
2018年 | 154篇 |
2017年 | 119篇 |
2016年 | 174篇 |
2015年 | 173篇 |
2014年 | 401篇 |
2013年 | 474篇 |
2012年 | 331篇 |
2011年 | 332篇 |
2010年 | 281篇 |
2009年 | 375篇 |
2008年 | 417篇 |
2007年 | 414篇 |
2006年 | 420篇 |
2005年 | 418篇 |
2004年 | 369篇 |
2003年 | 389篇 |
2002年 | 368篇 |
2001年 | 293篇 |
2000年 | 246篇 |
1999年 | 251篇 |
1998年 | 231篇 |
1997年 | 219篇 |
1996年 | 190篇 |
1995年 | 210篇 |
1994年 | 192篇 |
1993年 | 180篇 |
1992年 | 208篇 |
1991年 | 152篇 |
1990年 | 138篇 |
1989年 | 122篇 |
1988年 | 133篇 |
1987年 | 102篇 |
1986年 | 96篇 |
1985年 | 91篇 |
1984年 | 106篇 |
1983年 | 55篇 |
1982年 | 67篇 |
1981年 | 32篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1973年 | 4篇 |
排序方式: 共有9603条查询结果,搜索用时 15 毫秒
171.
Marcelo V. Sousa Michael Richardson Wagner Fontes Lauro Morhy 《Journal of Protein Chemistry》1994,13(8):659-667
Enterolobin, a 55-kDa cytolytic, inflammatory, and insecticidal protein isolated from seeds of the Brazilian treeEnterolobium contortisiliquum (Leguminosae-Mimosoideae) has been further purified and partially sequenced by using both manual and automated methods. A computational search of enterolobin partial amino acid sequence against the PIR database revealed possible sequence similarities with aerolysins, cytolytic proteins fromAeromonas species. An alignment of enterolobin partial sequence to the amino acid sequences ofA. hydrophila andA. sobria aerolysins showed several similar regions with many residue identites. The seed protein enterolobin and the bacterial aerolysins may be homologous proteins despite the distant phylogenetic relationship. 相似文献
172.
In a previous report [Yanget al., (1987a),J. Biol Chem.
262, 7034–7040], a cyclic-AMP- and calcium-independent brain kinase which requires autophosphorylation for activity was identified as a very potent myelin basic protein (MBP) kinase. In this report, the phosphorylation sites of MBP by this autophosphorylation-dependent protein kinase (autokinase) are further determined by two-dimensional electrophoresis/thin-layer chromatography, phosphoamino acid analysis, high-performance liquid chromatography, tryptic peptide mapping, sequential manual Edman degradation, and direct peptide sequencing. Autokinase phosphorylates MBP on both threonine and serine residues. Three major tryptic phosphopeptide peaks were resolved by C18-reversed phase highper-formance liquid chromatography. Sequential manual Edman degradation together with direct sequence analysis revealed that FS(p)WGAEGQKPGFGYGGR is the phosphorylation site sequence (molar ratio 1.0) for the first major phosphopeptide peak. When mapping with bovine brain MBP sequence, we finally demonstrate Ser115, one of thein vivo phosphorylation sites in MBP, as the major site phosphorylated by autokinase, implicating a physiologically relevant role of autokinase in the regulation of brain myelin function. By using the same approach, we also identified HRDT(p)GILDSLGR (molar ratio 0.9) and TT(p)HYGSLPQK (molar ratio 0.8) as the major phosphorylation site sequences in32P-MBP phosphorylated by autokinase, further indicating that -Arg-XSer/Thr-(neutral amino acid)3-(amino acid-containing hydroxyl group such as Ser/Glu/Asp)-(neutral amino acid)2-may represent a unique consensus sequence motif specifically recognized by this autophosphorylation-dependent multisubstrate/ multifunctional protein kinase in the brain. 相似文献
173.
Kazuo Yamamoto Chizu Ishida Mitsue Saito Yukiko Konami Toshiaki Osawa Tatsuro Irimura 《Glycoconjugate journal》1994,11(6):572-575
Maackia amurensis haemagglutinin (MAH) is a leguminous lectin which preferentially binds to a cluster of sialylatedO-linked carbohydrate chains (Konami Y, Yamamoto K, Osawa T, Irimura T (1994)FEBS Lett
342:334–38). In the present study a 950 bp cDNA clone encoding MAH was isolated from a cDNA library constructed from germinatedMaackia amurensis seeds. From the nucleotide sequence, MAH was predicted to consist of 285 amino acid residues containing a signal peptide of 29 amino acids. The results also confirmed our previous findings from the amino acid sequence analysis, which indicated that two highly conserved amino acid residues in all other well-known leguminous lectins were replaced in MAH. These residues were lysine-105 and aspartic acid-135. The corresponding amino acid residues in other leguminous lectins were glycine and asparagine, respectively. These differences were due to the presence of nucleotides AAA and GAT in place of AAT/C and GGA/T.Abbreviations MAH
Maackia amurensis haemagglutinin. 相似文献
174.
Mühlebach S. M. Gross M. Wirz T. Wallimann T. Perriard J. -C. Wyss M. 《Molecular and cellular biochemistry》1994,133(1):245-262
Comparisons of the protein sequences and gene structures of the known creatine kinase isoenzymes and other guanidino kinases revealed high homology and were used to determine the evolutionary relationships of the various guamidino kinases. A CK framework is defined, consisting of the most conserved sequence blocks, and diagnostic boxes are identified which are characteristic for anyone creatine kinase isoenzyme (e.g. for vertebrate B-CK) and which may serve to distinguish this isoenzyme from all others (e.g. from M-CKs and Mi-CKs). Comparison of the guanidino kinases by near-UV and far-UV circular dichroism further indicates pronounced conservation of secondary structure as well as of aromatic amino acids that are involved in catalysis.Abbreviations GuaK
guanidino kinase
- CK
creatine kinase
- B-and M-CK
brain and muscle cytosolic CK isoenzyme
- Mi-CK
mitochondrial CK isoenzyme
- ArgK
arginine kinase
- Cr
creatine
- PCr
phosphorylcreatine
- PArg
phosphorylarginine 相似文献
175.
I analyzed geographic partitioning of mitochondrial DNA (mtDNA) restriction-site variants in the spotted salamander, Ambystoma maculatum. Two highly divergent and geographically separate genetic lineages were identified that differed by a minimum of 19 restriction sites (6% sequence divergence). One of the lineages has a disjunct distribution with very closely related haplotypes occurring in Missouri, Arkansas, North Carolina, and Virginia. The other lineage is found in Michigan, Illinois, and Alabama. The geographic separation of highly divergent mtDNA haplotypes, a pattern that was predicted based on the sedentary nature of these salamanders, is evidence for long-term barriers to gene flow. In contrast, the large-scale disjunction of very similar haplotypes suggests recent, long-distance gene flow and does not match the phylogeographic expectation for a small terrestrial vertebrate. I explain this potential contradiction in the level of importance assigned to gene flow by a scenario in which historical barriers to gene flow account for the two divergent mtDNA assemblages, but stochastic sorting of ancestral polymorphism is responsible for the large-scale geographic disjunction. Ten of 16 populations collected in the Ozark Highlands were fixed for the same haplotype. I attribute this lack of detectable variation to recent colonization of this area, a hypothesis that is supported by paleoecological data and demonstrates the potential benefits of combining data from paleobotany, geology, and other disciplines to reconstruct the historical biogeography of a species. 相似文献
176.
Jan Kwiatowski Douglas Skarecky Kevin Bailey Francisco J. Ayala 《Journal of molecular evolution》1994,38(5):443-454
The phylogeny and taxonomy of the drosophilids have been the subject of extensive investigations. Recently, Grimaldi (1990)
has challenged some common conceptions, and several sets of molecular data have provided information not always compatible
with other taxonomic knowledge or consistent with each other. We present the coding nucleotide sequence of the Cu,Zn superoxide
dismutase gene (Sod) for 15 species, which include the medfly Ceratitis capitata (family Tephritidae), the genera Chymomyza and Zaprionus, and representatives of the subgenera Dorsilopha, Drosophila, Hirtodrosophila, Scaptodrosophila, and Sophophora. Phylogenetic analysis of the Sod sequences indicates that Scaptodrosophila and Chymomyza branched off the main lineage before the major Drosophila radiations. The presence of a second intron in Chymomyza and Scaptodrosophila (as well as in the medfly) confirms the early divergence of these two taxa. This second intron became deleted from the main
lineage before the major Drosophila radiations. According to the Sod sequences, Sophophora (including the melanogaster, obscura, saltans, and willistoni species groups) is older than the subgenus Drosophila; a deep branch splits the willistoni and saltans groups from the melanogaster and obscura groups. The genus Zaprionus and the subgenera Dorsilopha and Hirtodrosophila appear as branches of a prolific “bush” that also embraces the numerous species of the subgenus Drosophila. The Sod results corroborate in many, but not all, respects Throckmorton's (King, R.C. (ed) Handbook of Genetics. Plenum Press, New York, pp. 421–469, 1975) phylogeny; are inconsistent in some important ways with Grimaldi's (Bull. Am. Museum Nat. Hist.
197:1–139, 1990) cladistic analysis; and also are inconsistent with some inferences based on mitochondrial DNA data. The Sod results manifest how, in addition to the information derived from nucleotide sequences, structural features (i.e., the deletion
of an intron) can help resolve phylogenetic issues.
Correspondence requests to: F. J. Ayala 相似文献
177.
178.
The complete sequence of the carp mitochondrial genome of 16,575 base pairs has been determined. The carp mitochondrial genome encodes the same set of genes (13 proteins, 2 rRNAs, and 22 tRNAs) as do other vertebrate mitochondrial DNAs. Comparison of this teleostean mitochondrial genome with those of other vertebrates reveals a similar gene order and compact genomic organization. The codon usage of proteins of carp mitochondrial genome is similar to that of other vertebrates. The phylogenetic relationship for mitochondrial protein genes is more apparent than that for the mitochondrial tRNA and rRNA genes.Correspondence to: F. Huang 相似文献
179.
S. Chao C. Baysdorfer O. Heredia-Diaz T. Musket G. Xu E. H. Coe Jr 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,88(6-7):717-721
We report here the results of mapping a set of 92 leaf cDNA clones in maize. The ends of each of these cDNA clones have previously been partially sequenced, and the sequence comparison has revealed the putative function for 28 clones. It is expected that the RFLP map developed using these expressed sequence tags will be of great importance for future maize genome analysis, such as for PCR-based gene mapping or gene function identification.Contribution from the Missouri Agricultural Experiment Station. Journal Series N. 12,019. 相似文献
180.
Klaus K. Nielsen Kirsten Bojsen Peter Roepstorff Jørn D. Mikkelsen 《Plant molecular biology》1994,25(2):241-257
Two acidic chitinase isoforms, SP1 and SP2, have been purified to homogeneity from leaves of sugar beet (Beta vulgaris) infected with Cercospora beticola. SP1 and SP2 are extracellular proteins with an apparent molecular mass of 35 kDa and an approximate pI of 4.2. Since the only major difference was slightly diverging M
r's, only the SP2 chitinase was further characterized. Partial amino acid sequence data for SP2 was used to generate a polymerase chain reaction (PCR) clone employed for the isolation of a cDNA clone encoding SP2. SP2 exhibits significant structural identity with the class IV chitinases from sugar beet, rapeseed, bean and maize, but differs from the other members of this class in having a longer hinge region, comprising 22 amino acid residues, with a repeated TTP motif. Western blotting analyses, using antibody raised against SP2, demonstrated an induction of SP protein during infection with C. beticola. The induction was very local, with high protein accumulation found close to the infection site only. Amino acid compositional analysis of SP2 revealed that five out of fourteen prolines are hydroxylated. No glucosamine or galactosamine residues are present. Evidence was obtained that SP2 is glycosylated with a limited number (7) of xylose residues: (1) SP2 was stained with the periodic acid-Schiff (PAS) reagent, (2) electrospray mass spectrometry on SP2 gave a series of M
r's with a consistent increase between two molecular masses of 132 Da, (3) SP2 was recognized by an antibody specific for -1,4-D-xylopyranose. The vacuolar class I chitinases A and B in tobacco have recently been shown to comprise a new class of hydroxyproline-containing proteins (Sticher et al., Science 257 (1992) 655–657). The SP2 chitinase differs from these in being glycosylated and, thus, represents a novel type of hydroxyproline-containing glycoproteins in plants. 相似文献