全文获取类型
收费全文 | 2751篇 |
免费 | 171篇 |
专业分类
2922篇 |
出版年
2022年 | 18篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 27篇 |
2018年 | 36篇 |
2017年 | 32篇 |
2016年 | 56篇 |
2015年 | 79篇 |
2014年 | 106篇 |
2013年 | 185篇 |
2012年 | 171篇 |
2011年 | 156篇 |
2010年 | 88篇 |
2009年 | 71篇 |
2008年 | 154篇 |
2007年 | 115篇 |
2006年 | 136篇 |
2005年 | 126篇 |
2004年 | 132篇 |
2003年 | 107篇 |
2002年 | 92篇 |
2001年 | 94篇 |
2000年 | 98篇 |
1999年 | 87篇 |
1998年 | 29篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 48篇 |
1991年 | 46篇 |
1990年 | 43篇 |
1989年 | 54篇 |
1988年 | 49篇 |
1987年 | 44篇 |
1986年 | 43篇 |
1985年 | 40篇 |
1984年 | 28篇 |
1983年 | 10篇 |
1982年 | 28篇 |
1981年 | 13篇 |
1979年 | 17篇 |
1978年 | 18篇 |
1977年 | 12篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 8篇 |
1969年 | 16篇 |
1967年 | 7篇 |
排序方式: 共有2922条查询结果,搜索用时 0 毫秒
991.
Yukphan P Potacharoen W Nakagawa Y Tanticharoen M Yamada Y 《The Journal of General and Applied Microbiology》2004,50(1):9-15
Thirteen reference strains, including the type strains of the type species of the genus Gluconobacter, Gluconobacter oxydans (NBRC 14819T), Gluconobacter cerinus (NBRC 3267T), and Gluconobacter frateurii (IFO 3264T) were examined for their species identification based on the sequence and the restriction analyses of the 16S-23S rDNA internal transcribed spacer (ITS) regions. A phylogenetic tree constructed by the neighbor-joining method represented three clusters corresponding respectively to the three species, G. oxydans, G. cerinus, and G. frateurii. The type strain of Gluconobacter asaii (NBRC 3276T), which is a junior subjective synonym of G. cerinus, was included completely in the G. cerinus cluster. Several restriction endonucleases discriminating the three species from one another were selected by computer analyses: Bsp1286I, MboII, SapI, Bpu10I, EarI, BsiHKAI, and FatI. On digestion of the PCR products with restriction endonucleases Bsp1286I and MboII, all the restriction patterns coincided with those of the type strains of the three species except for strain NBRC 3251. This strain gave a different pattern from the type strain of G. frateurii, when digested with MboII. However, strain 3251 was included phylogenetically in the G. frateurii cluster. All the reference strains were thus identified at the species level by the sequence and the restriction analyses of the 16S-23S rDNA ITS regions. 相似文献
992.
Overexpression of NtHAL3 genes confers increased levels of proline biosynthesis and the enhancement of salt tolerance in cultured tobacco cells 总被引:1,自引:0,他引:1
Yonamine I Yoshida K Kido K Nakagawa A Nakayama H Shinmyo A 《Journal of experimental botany》2004,55(396):387-395
The Hal3 protein of Saccharomyces cerevisiae inhibits the activity of PPZ1 type-1 protein phosphatases and functions as a regulator of salt tolerance and cell cycle control. In plants, two HAL3 homologue genes in Arabidopsis thaliana, AtHAL3a and AtHAl3b, have been isolated and the function of AtHAL3a has been investigated through the use of transgenic plants. Expressions of both AtHAL3 genes are induced by salt stress. AtHAL3a overexpressing transgenic plants exhibit improved salt and sorbitol tolerance. In vitro studies have demonstrated that AtHAL3 protein possessed 4'-phosphopantothenoylcysteine decarboxylase activity. This result suggests that the molecular function of plant HAL3 genes is different from that of yeast HAL3. To understand the function of plant HAL3 genes in salt tolerance more clearly, three tobacco HAL3 genes, NtHAL3a, NtHAL3b, and NtHAL3c, from Nicotiana tabacum were identified. NtHAL3 genes were constitutively expressed in all organs and under all conditions of stress examined. Overexpression of NtHAL3a improved salt, osmotic, and lithium tolerance in cultured tobacco cells. NtHAL3 genes could complement the temperature-sensitive mutation in the E. coli dfp gene encoding 4'-phosphopantothenoyl-cysteine decarboxylase in the coenzyme A biosynthetic pathway. Cells overexpressing NtHAL3a had an increased intracellular ratio of proline. Taken together, these results suggest that NtHAL3 proteins are involved in the coenzyme A biosynthetic pathway in tobacco cells. 相似文献
993.
994.
Natori Y Imahori T Murakami K Yoshimura Y Nakagawa S Kato A Adachi I Takahata H 《Bioorganic & medicinal chemistry letters》2011,21(2):738-741
The asymmetric synthesis of 1-C-alkyl-l-arabinoiminofuranoses 1 was achieved by asymmetric allylic alkylation (AAA), ring closing metathesis (RCM), and Negishi cross coupling as key reactions. Some of the prepared compounds showed potent inhibitory activities towards intestinal maltase, with IC50 values comparable to those of commercial drugs such as acarbose, voglibose, and miglitol, which are used in the treatment of type 2 diabetes. Among them, the inhibitory activity (IC50 = 0.032 μM) towards intestinal sucrase of 1c was quite strong compared to the above commercial drugs. 相似文献
995.
Suzuki T Matsuura A Kouketsu A Hisakawa S Nakagawa H Miyata N 《Bioorganic & medicinal chemistry》2005,13(13):4332-4342
A series of suberoylanilide hydroxamic acid (SAHA)-based non-hydroxamates was designed, synthesized, and evaluated for their histone deacetylase (HDAC) inhibitory activity. Among these, methyl sulfoxide 15 inhibited HDACs in enzyme assays and caused hyperacetylation of histone H4 while not inducing the accumulation of acetylated alpha-tubulin in HCT116 cells. 相似文献
996.
997.
998.
Shin JO Nakagawa E Kim EJ Cho KW Lee JM Cho SW Jung HS 《Histochemistry and cell biology》2012,137(4):459-470
Palate development requires coordinating proper cellular and molecular events in palatogenesis, including the epithelial–mesenchymal
transition (EMT), apoptosis, cell proliferation, and cell migration. Zeb1 and Zeb2 regulate epithelial cadherin (E-cadherin) and EMT during organogenesis. While microRNA 200b (miR-200b) is known to be a negative regulator of Zeb1 and Zeb2 in cancer progression, its regulatory effects on Zeb1 and Zeb2 in palatogenesis have not yet been clarified. The aim of this study is to investigate the relationship between the regulators
of palatal development, specifically, miR-200b and the Zeb family. Expression of both Zeb1 and Zeb2 was detected in the mesenchyme of the mouse palate, while miR-200b was expressed in the medial edge epithelium. After contact
with the palatal shelves, miR-200b was expressed in the palatal epithelial lining and epithelial island around the fusion
region but not in the palatal mesenchyme. The function of miR-200b was examined by overexpression via a lentiviral vector
in the palatal shelves. Ectopic expression of miR-200b resulted in suppression of the Zeb family, upregulation of E-cadherin, and changes in cell migration and palatal fusion. These results suggest that miR-200b plays crucial roles in cell migration
and palatal fusion by regulating Zeb1 and Zeb2 as a noncoding RNA during palate development. 相似文献
999.
As part of the Kushiro Wetland Restoration Project, we evaluated the effect of the tree-cutting (February 2003) on soil water
chemistry for 3 years in an alder (Alnus japonica) shrubland on the peat soil in the Kushiro Wetland, the largest wetland in Japan. The alder stand was divided into two types;
low stature and high stature stands, mean heights being 1.5 and 2.6 m, respectively. The treatment plot with tree cutting
and the reference plot measuring 25 m × 25 m each were established in both stands, and a soil incubation experiment was also
conducted by trenching the root zone of wetland vegetation in the treatment plots in both stands in the summer of 2004. The
tree cutting did not substantially increase the concentrations of ammonium ion (NH4
+) and nitrate ion (NO3
−) in the soil water, although a gradual and slight increase of NO3
− concentration was found after the tree-cutting only in the high stature stand (<10 μmol/l). This increase in the NO3
− concentration in the high stature stand was probably due to the rhizosphere oxidation of wetland herbaceous vegetation, and
was accompanied by the increase of Ca2+ concentration. The soil incubation experiment showed no significant change of the nitrogen concentration, suggesting that
inorganic nitrogen was immobilized and NO3
− was denitrified intensively in this wetland peat soil. The results of this study suggested that this wetland ecosystem had
a high potential to stabilize the soil water chemistry. 相似文献
1000.
In certain planarian species that are able to switch between asexual and sexual reproduction, determining whether a sexual has the ability to switch to the asexual state is problematic, which renders the definition of sexuals controversial. We experimentally show the existence of two sexual races, acquired and innate, in the planarian Dugesia ryukyuensis. Acquired sexuals used in this study were experimentally switched from asexuals. Inbreeding of acquired sexuals produced both innate sexuals and asexuals, but inbreeding of innate sexuals produced innate sexuals only and no asexuals. Acquired sexuals, but not innate sexuals, were forced to become asexuals by ablation and regeneration (asexual induction). This suggests that acquired sexuals somehow retain asexual potential, while innate sexuals do not. We also found that acquired sexuals have the potential to develop hyperplastic and supernumerary ovaries, while innate sexuals do not. In this regard, acquired sexuals were more prolific than innate sexuals. The differences between acquired and innate sexuals will provide a structure for examining the mechanism underlying asexual and sexual reproduction in planarians. 相似文献