首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   630篇
  免费   54篇
  2023年   2篇
  2022年   5篇
  2021年   8篇
  2020年   3篇
  2019年   3篇
  2018年   7篇
  2017年   10篇
  2016年   18篇
  2015年   19篇
  2014年   29篇
  2013年   47篇
  2012年   31篇
  2011年   41篇
  2010年   21篇
  2009年   20篇
  2008年   45篇
  2007年   45篇
  2006年   23篇
  2005年   35篇
  2004年   37篇
  2003年   28篇
  2002年   35篇
  2001年   14篇
  2000年   16篇
  1999年   17篇
  1998年   8篇
  1997年   8篇
  1996年   5篇
  1995年   7篇
  1994年   6篇
  1993年   6篇
  1992年   8篇
  1991年   10篇
  1990年   7篇
  1989年   12篇
  1988年   3篇
  1987年   6篇
  1986年   2篇
  1985年   4篇
  1984年   3篇
  1982年   3篇
  1981年   4篇
  1980年   4篇
  1979年   2篇
  1976年   2篇
  1975年   7篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1968年   1篇
排序方式: 共有684条查询结果,搜索用时 15 毫秒
141.
Hattan  Jun-ichiro  Shindo  Kazutoshi  Ito  Tomoko  Shibuya  Yurica  Watanabe  Arisa  Tagaki  Chie  Ohno  Fumina  Sasaki  Tetsuya  Ishii  Jun  Kondo  Akihiko  Misawa  Norihiko 《Planta》2016,243(4):959-972
Planta - A novel terpene synthase ( Tps ) gene isolated from Camellia brevistyla was identified as hedycaryol synthase, which was shown to be expressed specifically in flowers. Camellia plants are...  相似文献   
142.
143.
144.
Mammals have co‐evolved with retroviruses, including lentiviruses, over a long period. Evidence supporting this contention is that viral infectivity factor (Vif) encoded by lentiviruses antagonizes the anti‐viral action of cellular apolipoprotein B mRNA editing enzyme catalytic polypeptide‐like 3 (APOBEC3) of the host. To orchestrate E3 ubiquitin ligase complex for APOBEC3 degradation, Vifs utilize mammalian proteins such as core‐binding factor beta (CBFB; for primate lentiviruses) or cyclophilin A (CYPA; for Maedi–Visna virus [MVV]). However, the co‐evolutionary relationship between lentiviral Vif and the mammalian proteins associated with Vif‐mediated APOBEC3 degradation is poorly understood. Moreover, it is unclear whether Vif proteins of small ruminant lentiviruses (SRLVs), including MVV and caprine arthritis encephalitis virus (CAEV), commonly utilize CYPA to degrade the APOBEC3 of their hosts. In this study, molecular phylogenetic and protein homology modeling revealed that Vif co‐factors are evolutionarily and structurally conserved. It was also found that not only MVV but also CAEV Vifs degrade APOBEC3 of both sheep and goats and that CAEV Vifs interact with CYPA. These findings suggest that lentiviral Vifs chose evolutionarily and structurally stable proteins as their partners (e.g., CBFB or CYPA) for APOBEC3 degradation and, particularly, that SRLV Vifs evolved to utilize CYPA as their co‐factor in degradation of ovine and caprine APOBEC3.  相似文献   
145.
146.
147.
Forty autopsy livers from Japanese individuals were studied concerning alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) isozymes using electrophoretic and enzyme assay methods. A remarkably high frequency (85%) was found for the atypical ADH phenotype. The gene frequencies of ADH22 and ADH32 were .625 and .05, respectively. The usual ALDH phenotype showed two major isozyme bands, a faster migrating (low Km for acetaldehyde) and a slower migrating isozyme (high Km for acetaldehyde). Fifty-two percent of the specimens had an unusual phenotype of ALDH, which showed only the slower migrating isozyme. The usual phenotype was inhibited about 20%--30% by disulfiram and the unusual type up to 90%. Such a high incidence in the Japanese of the unusual phenotype, which lacks in the low Km isozyme, suggests that the initial intoxicating symptoms after alcohol drinking in these subjects might be due to delayed oxidation of acetaldehyde rather than its higher-than-normal production by typical or atypical ADH.  相似文献   
148.
T Suzuki  M Narita  M Misawa  H Nagase 《Life sciences》1991,48(19):1827-1835
Pentazocine (PZ) is well known to act as an opioid mixed agonist-antagonist analgesic. In the present study, we selected the mouse warm plate test condition of 51 +/- 0.5 degrees C instead of 55 +/- 0.5 degrees C to determine the analgesic action of PZ. As a result, i.c.v. PZ produced a biphasic antinociceptive response, while U-50,488H (U-50) and morphine (MRP) showed a monophasic response. Pretreatment with i.c.v. beta-FNA (mu antagonist) antagonized the initial response, whereas the delayed one was antagonized by pretreatment with nor-BNI (kappa antagonist). In addition, pretreatment with NTI (delta antagonist) significantly attenuated the initial response but not the delayed one. These results suggest that the initial and delayed responses may be mediated mainly by mu/delta and kappa receptors, respectively. With regards to the interaction between MRP and PZ, a low dose of PZ antagonized the analgesic action of MRP, while a high dose PZ plus MRP showed the additive effect. Furthermore, tolerance developed almost equally to both initial and delayed responses, indicating that tolerance to the kappa component of PZ may be developed as well as the mu component of action of PZ.  相似文献   
149.
Summary Phenylalanine Ammonia-Lyase (PAL) containing microorganisms were isolated from a wide variety of natural habitats. The best 21 strains to emerge from the primary screen were screened for PAL activities in both directions using l-phenylalanine and t-cinnamate substrates. Twelve of the latter strains were compared for total cell production and PAL activity and 7 isolates were chosen for examination of the extent of PAL induction in various media. On the basis of these screens, isolate SPA 10 (identified as Rhodotorula rubra) was selected for further optimization. Growth was optimal at 28° C and pH 5.0, although cellular PAL activity was shown to be higher at sub-optimal temperatures (36° C) and pH (8.0) for growth. Synthesis of PAL was repressed when grown in the presence of various sugars and NH 4 + ions. Manipulation of fermentation conditions enabled PAL synthesis to occur at maximum biomass levels, upon glucose exhaustion. PAL was rapidly inactivated within cells shortly after maximum synthesis was attained: feeding of d,l-isoleucine and low concentrations of d,l-phenylalanine, and shifting of fermentation temperature conferred catalyst stability for fermentations over 100 h. These results demonstrate the suitability and superiority of isolate SPA 10 for the commercial production of l-phenylalanine from trans-cinnamic acid.  相似文献   
150.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号