全文获取类型
收费全文 | 2391篇 |
免费 | 184篇 |
国内免费 | 2篇 |
出版年
2023年 | 6篇 |
2022年 | 29篇 |
2021年 | 47篇 |
2020年 | 41篇 |
2019年 | 61篇 |
2018年 | 60篇 |
2017年 | 56篇 |
2016年 | 85篇 |
2015年 | 117篇 |
2014年 | 161篇 |
2013年 | 189篇 |
2012年 | 213篇 |
2011年 | 206篇 |
2010年 | 121篇 |
2009年 | 97篇 |
2008年 | 140篇 |
2007年 | 163篇 |
2006年 | 123篇 |
2005年 | 98篇 |
2004年 | 102篇 |
2003年 | 125篇 |
2002年 | 81篇 |
2001年 | 13篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 21篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 12篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1965年 | 3篇 |
1962年 | 2篇 |
排序方式: 共有2577条查询结果,搜索用时 31 毫秒
21.
Molecular characterization of the proteinase-encoding gene, prb1, related to mycoparasitism by Trichoderma harzianum 总被引:11,自引:0,他引:11
Roberto A. Geremia Gustavo H. Goldman Dirk Jacobs W. Ardrtes Silvia B. Vila Marc Van Montagu Alfredo Herrera-Estrella 《Molecular microbiology》1993,8(3):603-613
The soil fungus Trichoderma harzianum is a mycoparasitic fungus known for its use as a biocontrol agent of phytopathogenic fungi. Among other factors, Trichoderma produces a series of antibiotics and fungal cell wall-degrading enzymes. These enzymes are believed to play an important role in mycoparasitism. Among the hydrolytic enzymes, we have identified a basic proteinase (Prb1) which is induced by either autoclaved mycelia, fungal cell wall preparation or chitin; however, the induction does not occur in the presence of glucose. The proteinase was purified and biochemically characterized as a serine proteinase of 31 kDa and pl 9.2. Based on the sequence of three internal peptides, synthetic oligonudeotide probes were designed. These probes allowed subsequent isolation of a cDNA and its corresponding genomic clone. The deduced amino acid sequence indicates that the proteinase is synthesized as a pre-proenzyme and allows its classification as a serine proteinase. Northen analysis shows that the induction of this enzyme is due to an increase in the corresponding mRNA level. 相似文献
22.
23.
Jens M. Olesen Yoko L. Dupont Bodil K. Ehlers Alfredo Valido Dennis M. Hansen 《Nordic Journal of Botany》2003,23(5):537-539
Jasminum odoratissimum is a Madeira and Canary Islands endemic showing classic heterostyly, i.e. with long-styled flowers with anthers at a low level in the corolla tube and short-styled flowers with anthers at a high level in the corolla tube. Short-styled flowers have large pollen, whereas long-styled flowers have small pollen. The two types are present in equal frequencies in the population. 相似文献
24.
De Andrade Antônio V. M. Da Costa Nivan B. Longo Ricardo L. Malta Oscar L. Simas Alfredo M. De Sá Gilberto F. 《Molecular Engineering》1997,7(3-4):293-308
Theoretical techniques have been developed and/or improved to predict the molecular structure of lanthanide complexes which
were used to calculate their electronic properties, in particular, their electronic spectra and energy levels necessary to
calculate the rates of energy transfer from the ligands to the metal ion. The molecular structure has been obtained by the
SMLC/AM1 (Sparkle Model for the Calculation of Lanthanide Complexes – Austin Model 1) model where the lanthanide ion is simulated
by a sparkle implemented into the AM1 Hamiltonian used to perform a HF-SCF (Hartree-Fock Self-Consistent Field) calculation.
The previous implementation of the SMLC/AM1 model (sparkle/1) involving only two parameters has been generalized to be consistent
with the AM1 Hamiltonian and the new model (sparkle/2) significantly improved the prediction of molecular structures of Eu(III)
complexes. For the electronic spectra and energy level calculations of the lanthanide complexes the model replaces the metal
ion by a point charge with the ligands held in their positions as determined by the SMLC/AM1 model, and uses a INDO/S-CI (intermediate
neglect of differential overlap/spectroscopic-configuration interaction) model. A preliminary study of the solvent effects
on the absorption spectra of the free ligand is also presented. For the ligand-lanthanide ion energy transfer Fermi's golden
rule is used with the multipolar and exchange mechanisms being implemented and tested for several complexes. These theoretical
techniques have been applied to several complexes yielding very good results when compared to experimental data as well as
predictions for the molecular and electronic structures and the relative contributions of the mechanisms for the energy transfer
rates.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
25.
The present study involved an electrophoretic survey of 22 protein loci in 269 individuals belonging to three species of the genusAkodon, A. aff.cursor (2n=16),A. cursor (2n=14/15), andA. montensis (2n=24/25/26), collected in Eastern Brazil. The joint results of gene diversity, genetic distances, phenetic analyses, and phylogenetic trees suggested thatA. aff.cursor has recently separated fromA. cursor and that the three species have experienced a recent chromosomal divergence followed by low allozyme differentiation. These data are in agreement with their classification as sibling species. 相似文献
26.
A polymerase chain reaction-based method of site-directed mutagenesis was used to introduce anNco I restriction site on the translation start site of a tomato peroxidase gene. This quick and efficient method utilized two
overlapping synthetic oligonucleotide primers containing the requisite base pair changes on the ATG translation start site
and two flanking primers in PCR. The resulting DNA amplified fragments were fused together byNco I digestion at the mutated ends followed by a T4 ligation reaction. A rapid alternative method utilizing the overlapping
fragments and the flanking primers in PCR can also be used for ligating the two fragments. Cloning and sequencing of the PCR-amplified
fragments provided additional evidence for the presence of the site-specific mutations. Unique restriction sites upstream
and downstream of the site-specific mutation allows for the easy transfer of this mutated region into the wild type peroxidase
gene. 相似文献
27.
The structure of the grasses megagametophyte is considered to be characteristic enough as to deserve a particular place in the megagametophyte typology. Furthermore, it is compared with those of other Monocotyledonous families to point out embryological affinities.Both are members of the Carrera del Investigador (Conicet, Argentina). 相似文献
28.
29.
30.