全文获取类型
收费全文 | 503篇 |
免费 | 36篇 |
专业分类
539篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2018年 | 4篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 4篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 14篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 18篇 |
2008年 | 21篇 |
2007年 | 28篇 |
2006年 | 18篇 |
2005年 | 23篇 |
2004年 | 36篇 |
2003年 | 22篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 19篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 22篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1969年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有539条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Tae Sato Satoshi Ito Yasushi Mitsuda Norihisa Soen 《Landscape and Ecological Engineering》2010,6(1):89-98
We examined the impacts of land-use history on the species composition and diversity of a warm-temperate riparian forest landscape
in Kyushu, southern Japan, focusing on the relationship between evergreen oaks and deciduous trees in natural and seminatural
forests. The species composition of 59 plots was classified into four types (A to D). Type A, which showed a significant bias
towards sites not subject to nonforest land use since 1947, had high species diversity consisting of (1) many lucidophyllous
components of the region, including the rare indigenous oak Quercus hondae, and (2) summergreen tree species of varying dominance and number representing unique or locally rare elements of the riparian
landscape in this warm-temperate region. Type B was dominated by a common species of oak, Q. glauca, and displayed less clear distribution bias with land-use history. In contrast to types A and B, types C and D, which were
characterized by high dominance of deciduous trees, had negative bias away from sites that had been under forest land use
in 1947. Presumably, intensive anthropogenic disturbances associated with nonforest land uses had expanded the habitats for
deciduous trees. This phenomenon was represented by the establishment of forests (type D) dominated by Ulmus davidiana var. japonica (UDJ) after it had been released from the suppression of evergreen forest trees during a period of nonforest land use that
prevents the successful recovery of evergreen trees. From these results we conclude that the impacts of land-use history on
the diversity of warm-temperate riparian forest landscape are multiphased: a period of nonforest land use has a strong negative
impact on lucidophyllous forest trees represented by the rare indigenous oak Q. hondae; release from the suppressive effects of the lucidophyllous species then encourages establishment of locally rare deciduous
tree flora represented by UDJ, which continue to persist for decades after abandonment of nonforest land use. 相似文献
45.
Aoki N Sakiyama A Kuroki K Maenaka K Kohda D Deshimaru M Terada S 《Biochimica et biophysica acta》2008,1784(4):621-628
Habu (Trimeresurus flavoviridis) serum contains 3 small serum proteins (SSP-1, SSP-2, and SSP-3) with molecular masses of 6.5 to 10 kDa. Gel filtration analysis showed that all the SSPs exist in high molecular mass forms of approximately 60 kDa in the serum. Ultrafiltration of Habu serum showed that SSPs dissociated from the complex below a pH of 4. An SSP-binding protein was purified from Habu serum by gel filtration, ion exchange, and reverse-phase HPLC. N-terminal sequencing yielded a 39-amino acid sequence, similar to the N-terminal region of triflin, which is a snake venom-derived Ca2+ channel blocker that suppresses smooth muscle contraction. The amino acid sequence of this protein, termed serotriflin, was established by peptide analysis and cDNA cloning. Serotriflin is a glycosylated protein and consists of 221 amino acids. Among the 3 SSPs, only SSP-2 formed a noncovalent complex with serotriflin. It was bound to triflin and serotriflin with high affinity, as evidenced by surface plasmon resonance. SSP-2 is considered to be a protein that prevents self injury by accidental leaking of venom into the blood. 相似文献
46.
A seed and flower color marker (P), nine seed protein, nine isozyme and 224 restriction fragment length polymorphism marker loci were used to construct a linkage map of the common bean, Phaseolus vulgaris L. (n = 11). The mapping population consisted of a backcross progeny between the Mesoamerican breeding line 'XR-235-1-1' and the Andean cultivar 'Calima'; the former was used as the recurrent parent. A bean PstI genomic library enriched for single copy sequences (95%) was the source of DNA probes. Sixty percent of the probes tested detected polymorphisms between the parental genotypes with at least one of the four restriction enzymes used here (DraI, EcoRI, EcoRV and HindIII). The computer software Mapmaker was used to determine the linkage relationships and linear order of segregating markers. These markers assorted into 11 linkage groups covering 960 cM of the bean genome. Partial linkage data were used to estimate the total length of the genome at 1200 cM. This estimate and that for the physical size of the genome yield an average ratio of 530 kb/cM. The relatively small size of the genome makes this crop species a good candidate for the isolation of genes via chromosome walking techniques. 相似文献
47.
Haruhiko Sakiyama Noriko Fujiwara Yuka Yoneoka Daisaku Yoshihara Hironobu Eguchi Keiichiro Suzuki 《Free radical research》2016,50(6):666-677
Nonalcoholic fatty liver disease (NAFLD) is one of the most prevalent chronic diseases, and results in the development of fibrosis. Oxidative stress is thought to be one of the underlying causes of NAFLD. Copper/zinc superoxide dismutase (SOD1) is a primary antioxidative enzyme that scavenges superoxide anion radicals. Although SOD1 knockout (KO) mice have been reported to develop fatty livers, it is not known whether this lack of SOD1 leads to the development of fibrosis. Since the accumulation of collagen typically precedes liver fibrosis, we assessed the balance between the synthesis and degradation of collagen in liver tissue from SOD1 KO mice. We found a higher accumulation of collagen in the livers of SOD1 KO mice compared to wild type mice. The level of expression of HSP47, a chaperone of collagen, and a tissue inhibitor (TIMP1) of matrix metalloproteinases (a collagen degradating enzyme) was also increased in SOD1 KO mice livers. These results indicate that collagen synthesis is increased but that its degradation is inhibited in SOD1 KO mice livers. Moreover, SOD1 KO mice liver sections were extensively modified by advanced glycation end products (AGEs), which suggest that collagen in SOD1 KO mice liver might be also modified with AGEs and then would be more resistant to the action of collagen degrading enzymes. These findings clearly show that oxidative stress plays an important role in the progression of liver fibrosis. 相似文献
48.
The synthesis of 8-methyladenosine-substituted 2-5A tetramers with hydroxyalkyl groups at the 5'-phosphates and the corresponding 2-5A-antisense chimeras is described. These oligonucleotides were synthesized by the phosphoramidite method with a DNA/RNA synthesizer. These 2-5A tetramers with hydroxyethyl and hydroxybutyl groups at their 5'-phosphates were more resistant to hydrolysis by alkaline phosphatase than those without the hydroxyalkyl groups. Incorporation of the hydroxyethyl group into the 2-5A tetramer and 2-5A-antisense chimera slightly reduced the abilities of their analogues to activate recombinant human RNase L, but the abilities of the 2-5A tetramer and the 2-5A-antisense chimera both with the hydroxyethyl group and 8-methyladenosine returned to 80 and 50% relative to those of the oligonucleotides without the hydroxyethyl group and 8-methyladenosine, respectively. Furthermore, the enzyme activated by 8-methyladenosine-substituted 2-5A-antisense chimera with the hydroxyethyl group cleaved the complementary RNA as efficiently as that activated by 2-5A-antisense chimera without the hydroxyethyl group and 8-methyladenosine. Thus, the 2-5A-antisense chimera carrying the hydroxyethyl group and 8-methyladenosine will be a candidate for a novel antisense molecule. 相似文献
49.
Wheat SOC1 functions independently of WAP1/VRN1, an integrator of vernalization and photoperiod flowering promotion pathways 总被引:1,自引:0,他引:1
Naoki Shitsukawa Chihiro Ikari Tadayuki Mitsuya Takeshi Sakiyama Atsushi Ishikawa Shigeo Takumi Koji Murai 《Physiologia plantarum》2007,130(4):627-636
Heading time in bread wheat ( Triticum aestivum L.) is determined by three characters – vernalization requirement, photoperiodic sensitivity and narrow-sense earliness (earliness per se) – which are involved in the phase transition from vegetative to reproductive growth. The wheat APETALA1 ( AP1 )-like MADS-box gene, wheat AP1 ( WAP1 , identical with VRN1 ), has been identified as an integrator of vernalization and photoperiod flowering promotion pathways. A MADS-box gene, SUPPRESSOR OF OVEREXPRESSION OF CO 1 ( SOC1 ) is an integrator of flowering pathways in Arabidopsis . In this study, we isolated a wheat ortholog of SOC1 , wheat SOC1 ( WSOC1 ), and investigated its relationship to WAP1 in the flowering pathway. WSOC1 is expressed in young spikes but preferentially expressed in leaves. Expression starts before the phase transition and is maintained during the reproductive growth phase. Overexpression of WSOC1 in transgenic Arabidopsis plants caused early flowering under short-day conditions, suggesting that WSOC1 functions as a flowering activator in Arabidopsis . WSOC1 expression is affected neither by vernalization nor photoperiod, whereas it is induced by gibberellin at the seedling stage. Furthermore, WSOC1 is expressed in transgenic wheat plants in which WAP1 expression is cosuppressed. These findings indicate that WSOC1 acts in a pathway different from the WAP1 -related vernalization and photoperiod pathways. 相似文献
50.
C. Eduardo Vallejos Ney S. Sakiyama Valerie Jones Savita Shanker 《Plant Molecular Biology Reporter》2007,25(1-2):11-16
We describe a modification of a protocol for the isolation of BAC DNA using a silica membrane-based kit designed for the isolation
of plasmid DNA. The major advantages of this protocol are the expediency of the procedure, the high yield and purity, and
the high quality of the BAC DNA that is suitable for direct sequencing. 相似文献