全文获取类型
收费全文 | 6948篇 |
免费 | 350篇 |
国内免费 | 5篇 |
出版年
2023年 | 11篇 |
2022年 | 50篇 |
2021年 | 70篇 |
2020年 | 57篇 |
2019年 | 53篇 |
2018年 | 81篇 |
2017年 | 69篇 |
2016年 | 158篇 |
2015年 | 229篇 |
2014年 | 238篇 |
2013年 | 506篇 |
2012年 | 453篇 |
2011年 | 488篇 |
2010年 | 295篇 |
2009年 | 273篇 |
2008年 | 467篇 |
2007年 | 500篇 |
2006年 | 454篇 |
2005年 | 443篇 |
2004年 | 505篇 |
2003年 | 386篇 |
2002年 | 399篇 |
2001年 | 69篇 |
2000年 | 59篇 |
1999年 | 66篇 |
1998年 | 99篇 |
1997年 | 72篇 |
1996年 | 69篇 |
1995年 | 72篇 |
1994年 | 60篇 |
1993年 | 51篇 |
1992年 | 44篇 |
1991年 | 49篇 |
1990年 | 39篇 |
1989年 | 36篇 |
1988年 | 40篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 20篇 |
1984年 | 23篇 |
1983年 | 17篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1973年 | 10篇 |
排序方式: 共有7303条查询结果,搜索用时 15 毫秒
141.
Toshiharu Nagatsu Kazuhiro Oka Takeshi Kato 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1979,163(3):247-252
A highly sensitive assay for tyrosine hydroxylase (TH) activity by high-performance liquid chromatography (HPLC) with amperometric detection was devised based on the rapid isolation of enzymatically formed DOPA by a double-column procedure, the columns fitted together sequentially (the top column of Amberlite CG-50 and the bottom column of aluminium oxide). DOPA was adsorbed on the second aluminium oxide column, then eluted with 0.5 M hydrochloric acid, and assayed by HPLC with amperometric detection. d-Tyrosine was used for the control. α-Methyldopa was added to the incubation mixture as an internal standard after incubation. This assay was more sensitive than radioassays and 5 pmol of DOPA formed enzymatically could be measured in the presence of saturating concentrations of tyrosine and 6-methyltetrahydropterin. The TH activity in 2 mg of human putamen could be easily measured, and this method was found to be particularly suitable for the assay of TH activity in a small number of nuclei from animal and human brain. 相似文献
142.
The per(trimethylsilyl) ethers of d-glucose, d-galactose, and d-mannose were analyzed by g.l.c.-c.i.m.s. with ammonia as the reagent gas. C.i.m.s. gave simple fragmentation and fragment ions of high intensity in the high-mass range where the QM+ ion is also detected. The β-d anomers gave ions at m/e 558 showing intensities 3–12 times those of the α-d anomers. The epimers could be distinguished by differences in the intensities of the ions and by the observation that d-glucose gave a base peak at m/e 198, d-galactose at m/e 468, and d-mannose at m/e 204. The pyranose and furanose structures could be distinguished by comparing the ion intensities at m/e 198, m/e 271, m/e 361, m/e 396, and m/e 451. A similar analysis was also performed with 2-methylpropane as the reagent gas. 相似文献
143.
Takeshi Hashizume Sadakatsu Sakai Tamizi Sugiyama Satoshi Matsubara 《Phytochemistry》1976,15(12):1813-1815
O6-Substituted guanine and hypoxanthine derivatives were prepared and tested for their cytokinin activity by the tobacco callus, radish cotyledons and lettuce seed bioassay systems. The results indicated that some derivatives of both types possess cytokinin activity. 相似文献
144.
Sumiko Hara Chisato Kaneko Hiroatsu Matsumoto Takeshi Nishino Tadao Takeuchi Takeo Mori 《Nucleosides, nucleotides & nucleic acids》2013,32(2-4):571-582
Abstract Novel β-D-ribofuranosides having a 5-substituted imidazo [4,5-d] [1,3]thiazine ring, including the S6-congener 3 of oxanosine 2, were synthesized for screening their anticancer and antiviral activities. 相似文献
145.
146.
147.
Takeshi Kikuchi 《Journal of Protein Chemistry》1992,11(5):579-581
The prediction of the short-range compact regions of human atrial natriuretic peptide (a-hANP), one of the biologically active peptides, has been made by means of the Average Distance Map(ADM). We found out that the location of the predicted short-range compact regions is consistent with the structural units determined by the NMR analysis (Kobayashiet al., 1988). Furthermore, the short-range compact regions correspond well to the biologically active areas of atriopeptin (103–125)-amide (which is homologous peptide toa-hANP), detected by the glycine substitution technique (Konishiet al., 1987). The results suggest that a predicted short-range compact region can be regarded as a possible active site in a biologically active peptide. 相似文献
148.
H. Ueda Takeshi Baba Nobuo Terada Yasuko Kato Shigeo Tsukahara Shinichi Ohno 《Histochemistry and cell biology》1997,108(3):243-248
It is known that the retina contains the protein dystrophin in the ribbon synapse, but the ultrastructural analysis is not
yet fully elucidated. Our previous study reported that dystrophin is localized under the rod cell membranes in rat retinas.
In the present study, we have investigated the relationship between dystrophin-rich regions of rod cell membranes and other
neuronal processes in mouse retinas with a monoclonal antibody raised against the human dystrophin C-terminus. Immunoblotting,
immunofluorescence stainings, and immunoelectron microscopy were employed. Immunoblotting analysis indicated that mouse retinas
possessed some of the dystrophin isoforms of approximately 260 kDa, 140 kDa, and 70 kDa molecular weight. Confocal images
showed a punctate appearance in the outer plexiform layer, as previously described. Immunoelectron microscopy showed that
dystrophin immunoreactive products were always observed at submembranous dense regions of the rod spherule abutting bipolar
processes. These results suggest that retinal dystrophin may be closely involved in signal transmission from rods to bipolar
cells.
Accepted: 7 May 1997 相似文献
149.
Takuo Kosuge Hiroshi Zenda Kunio Tsuji Takeshi Yamamoto Hiroko Narita 《Bioscience, biotechnology, and biochemistry》2013,77(5):693-696
Distribution of tetramethylpyrazine (T.M.P.) in Japanese fermented foodstuffs was investigated by more accurate analytical method.Namely, the method was successful when trapping T.M.P. with picric acid after flash evaporation of the foodstuffs, followed by analysis with gas chromatography.T.M.P. was detected in many Japanese fermented foodstuffs, especially in Miso, Soy sause and Natto, which suggests that alkylpyrazines may play an important role as flavor of those foodstuffs. 相似文献
150.
Nobuyuki Terakado Hayami Azechi Kiyoji Ninomiya Tsuguaki Fukuyasu Takeshi Shimizu 《Microbiology and immunology》1974,18(1):45-48
Bordetella bronchiseptica strains isolated from the nasal cavities of young pigs in Japan from 1969 to 1972 were surveyed for drug resistance and distribution of R factors. Of 304 strains examined, 71 (23%) were resistant to either one or more of following three drugs, streptomycin (SM), sulfadimethoxine (SA), and aminobenzyl penicillin (APC). Triple (SM.SA.APC)-resistance was most frequent among these resistant strains. Strains of double (SM. SA)- or single (SM)- and (SA)-resistance were also isolated, but were very few in numbers. Of the 71 drug-resistant strains, 61 (86%) were found to carry R factors which were capable of conjugal transfer. All of these R factors had the triple (SM.SA.APC)-resistant markers and were identified as fi– (no fertility inhibition) type. The (SM.SA.APC)-resistant strains carrying R factors had been isolated from pigs reared on various farms in different districts, and consequently the prevalence of B. bronchiseptica strains carrying R factors was considered to be relatively wide-spread in young pigs. 相似文献