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   1486篇
  免费   43篇
  2023年   26篇
  2022年   25篇
  2021年   49篇
  2020年   33篇
  2019年   48篇
  2018年   40篇
  2017年   42篇
  2016年   49篇
  2015年   52篇
  2014年   97篇
  2013年   107篇
  2012年   112篇
  2011年   150篇
  2010年   89篇
  2009年   68篇
  2008年   85篇
  2007年   85篇
  2006年   82篇
  2005年   70篇
  2004年   70篇
  2003年   55篇
  2002年   45篇
  2001年   9篇
  2000年   8篇
  1999年   3篇
  1998年   6篇
  1997年   1篇
  1996年   1篇
  1995年   2篇
  1994年   3篇
  1993年   1篇
  1991年   1篇
  1990年   4篇
  1989年   2篇
  1987年   1篇
  1986年   3篇
  1983年   1篇
  1982年   1篇
  1979年   1篇
  1964年   1篇
  1963年   1篇
排序方式: 共有1529条查询结果,搜索用时 15 毫秒
991.
Transgenic Research - Most of the commercialized insect resistant transgenic crops express cry gene(s) isolated from Bacillus thuringiensis; however, intensive cultivation of Bt crops over almost...  相似文献   
992.
993.
Drowning is a major public health problem in Turkey as it is for other countries. According to the latest statistics, the annual average number of people who drowned in the rivers, lakes, or seas of Turkey is 642. An examination of the language and the presentation style that the media use while covering the news about drowning cases may help us to determine the risk factors of the drowning cases and reduce the number. This study aims to show the awareness level of the Turkish print media on preventing drowning incidents and to discuss the steps to be taken in the Turkish media in order to prevent drowning. To this end, attitudes and presentations of three best-selling newspapers in Turkey—Zaman, Posta, and Hürriyet—and a less-selling one, Cumhuriyet, were studied in accordance with the content analysis method. The results show that the awareness of the Turkish media to prevent drowning incidents is inadequate. The number of drowning cases covered by these newspapers are very few, and they emphasis the forensic aspect of the incidents by using dramatic language without background information.  相似文献   
994.
995.
The aim of this study was to determine the presence and prevalence of larval stages of Dicrocoelium dendriticum and Brachylaima sp. in the first intermediate host, a species of land snail, Helix aspersa, in Turkey. A total of 211 snails were collected in April-May 2014 from pastures in Mersin District. Larval stages of D. dendriticum were identified under a light microscope. Hepatopancreas from naturally infected H. aspersa snails were examined histologically. The prevalence of larval stages of D. dendriticum and Brachylaima sp. in H. aspersa snails was found to be 2.4% and 1.9%, respectively, in Mersin, Turkey. Cercariae were not matured in sporocysts at the beginning of April; however, it was observed that cercariae matured and started to leave sporocysts by early-May. Thus, it was concluded that H. aspersa acts as an intermediate host to D. dendriticumin and Brachylaima sp. in Mersin, Turkey. A digenean trematode Brachylaima sp. was seen for the first time in Turkey.  相似文献   
996.
Reactivation of androgen receptor (AR) may drive recurrent prostate cancer in castrate patients. Ack1 tyrosine kinase is overexpressed in prostate cancer and promotes castrate resistant xenograft tumor growth and enhances androgen target gene expression and AR recruitment to enhancers. Ack1 phosphorylates AR at Tyr-267 and possibly Tyr-363, both in the N-terminal transactivation domain. In this study, the role of these phosphorylation sites was investigated by characterizing the phosphorylation site mutants in the context of full length and truncated AR lacking the ligand-binding domain. Y267F and Y363F mutants showed decreased transactivation of reporters. Expression of wild type full length and truncated AR in LNCaP cells increased cell proliferation in androgen-depleted conditions and increased colony formation. However, the Y267F mutant of full length and truncated AR was defective in stimulating cell proliferation. The Y363F mutant was less severely affected than the Y267F mutant. The full length AR Y267F mutant was defective in nuclear translocation induced by androgen or Ack1 kinase. The truncated AR was constitutively localized to the nucleus. Chromatin immunoprecipitation analysis showed that it was recruited to the target enhancers without androgen. The truncated Y267F AR mutant did not exhibit constitutive nuclear localization and androgen enhancer binding activity. These results support the concept that phosphorylation of Tyr-267, and to a lesser extent Tyr-363, is required for AR nuclear translocation and recruitment and DNA binding and provide a rationale for development of novel approaches to inhibit AR activity.  相似文献   
997.
998.
Ammonia is considered to be the main agent responsible for hepatic encephalopathy which progressively leads to altered mental status. N‐methyl‐D‐aspartate (NMDA) is an ionotropic glutamate receptor, which is involved in synaptogenesis, memory and neurotoxicity. The aim of this study was to investigate the effects of ammonia intoxication and allopurinol, a xanthine oxidase (XO) inhibitor, on NMDA receptor subunits, NR2A and NR2B, in the hippocampus of rats. Thirty‐six male rats were divided into three groups (n = 12/group) as follows: (1)control group (phosphate buffered saline (PBS) solution); (2)ammonia group (ammonium acetate, 2.5 mmol/kg), (3)ammonia + allopurinol group (ammonium acetate, 2.5 mmol/kg, allopurinol, 50 mg/kg). Each rat received intraperitoneal injection for 28 days. Western Blotting technique was used for detecting NR2A and NR2B expressions. Both NR2A and NR2B subunit expressions decreased 27 and 11%, respectively, in ammonia group with respect to the control group. Ammonium acetate decreased significantly in NR2A subunit expressions in the hippocampus (p < 0.01). Administration of ammonia + allopurinol caused statistically significant increases in NR2A subunit expressions compared to the ammonia group (p < 0.001). The down‐regulation of NMDA receptors caused by ammonium acetate suggest that these receptors may play role in the process of hepatic encephalopathy and using allopurinol may have some protective effects in ammonia toxicity. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   
999.
Morphologies of pollen and seed surfaces were investigated with SEM technology for eight natural Ophrys taxa collected from southeastern Mediterranean countries and Turkey. The morphometric characteristics ofO. transhyrcana, O. sphegodes, O. epirotica, O. mammosa, O. pseudomammosa, O. oestrifera subsp.oestrifera, O. cornuta, andO. apifera were recorded and compared statistically. In general, the current species could be separated, in detail, according to those characteristics. These findings were also compared with those from recent studies, and were examined in terms of the present neighbouring taxa.  相似文献   
1000.
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