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   10536篇
  免费   1083篇
  国内免费   1270篇
  12889篇
  2024年   59篇
  2023年   176篇
  2022年   419篇
  2021年   590篇
  2020年   431篇
  2019年   487篇
  2018年   485篇
  2017年   365篇
  2016年   445篇
  2015年   684篇
  2014年   837篇
  2013年   858篇
  2012年   988篇
  2011年   819篇
  2010年   539篇
  2009年   487篇
  2008年   560篇
  2007年   491篇
  2006年   439篇
  2005年   360篇
  2004年   345篇
  2003年   302篇
  2002年   312篇
  2001年   205篇
  2000年   174篇
  1999年   161篇
  1998年   137篇
  1997年   111篇
  1996年   94篇
  1995年   83篇
  1994年   74篇
  1993年   59篇
  1992年   64篇
  1991年   45篇
  1990年   37篇
  1989年   22篇
  1988年   30篇
  1987年   22篇
  1986年   12篇
  1985年   15篇
  1984年   31篇
  1983年   9篇
  1982年   12篇
  1981年   5篇
  1980年   3篇
  1972年   2篇
  1970年   3篇
  1967年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The transport properties and differential conductance of the heterostructures constructed by (5,5) single wall carbon nanotube (SWCNT) and (5,5) single wall boron nitride nanotube (SWBNNT) are investigated using density functional theory in combination with non-equilibrium Green’s functions. We find that the transmission conductance of (5,5) BN/C nanotube heterostructure is not only continually depressed as the BNNT region increases but also the drop of the conductance is uniform in the energy window (?1.43 eV, 1 eV), which leads to linear I–V dependence for the systems when the bias is within this energy range. Moreover, the differential conductance linearly decreases when n?≤?3 but exponentially decreases when n?≥?3 for (5,5)(BN) n /C heterostructure. Such tunable differential conductance of (5,5) BN/C nanotube heterostructure mainly derives from the blockage of the transport channels induced by the semiconductive BN segment.
Figure
The transmission conductance and differential conductance of (5,5) BN/C nanotube heterostructure is continually depressed as the BNNT region increases.  相似文献   
992.
A new symmetrical phenylpropanoid glycoside, tangshenoside VIII (1), together with six known tangshenosides (27) were isolated from the roots of Codonopsis lanceolata (Campanulaceae). Their structures were established on the basis of spectroscopic data, including two-dimensional NMR analyses. Tangshenosides have chemotaxonomic significance.  相似文献   
993.
It has been suggested that drugs combining activities of selective serotonin reuptake inhibitor and 5-HT1A receptor agonist may form a novel strategy for higher therapeutic efficacy of antidepressant. The present study aimed to examine the pharmacology of YL-0919, a novel synthetic compound with combined high affinity and selectivity for serotonin transporter and 5-HT1A receptors. We performed in vitro binding and function assays and in vivo behavioral tests to assess the pharmacological properties and antidepressant-like efficacy of YL-0919. YL-0919 displayed high affinity in vitro to both 5-HT1A receptor and 5-HT transporter prepared from rat cortical tissue. It exerted an inhibitory effect on forskolin-stimulated cAMP formation and potently inhibited 5-HT uptake in both rat cortical synaptosomes and recombinant cells. After acute p.o. administration, very low doses of YL-0919 reduced the immobility time in tail suspension test and forced swimming test in mice and rats, with no significant effect on locomotor activity in open field test. Furthermore, WAY-100635 (a selective 5-HT1A receptor antagonist, 0.3 mg/kg) significantly blocked the effect of YL-0919 in tail suspension test and forced swimming test. In addition, chronic YL-0919 treatment significantly reversed the depressive-like behaviors in chronically stressed rats. These findings suggest that YL-0919, a novel structure compound, exerts dual effect on the serotonergic system, as both 5-HT1A receptor agonist and 5-HT uptake blocker, showing remarkable antidepressant effects in animal models. Therefore, YL-0919 may be used as a new option for the treatment of major depressive disorder.  相似文献   
994.
Wang  Xuefei  Xie  Huiqin  Ku  Yongli  Yang  Xiangna  Chen  Yinglong  Yang  Nan  Mei  Xueli  Cao  Cuiling 《Plant and Soil》2020,448(1-2):413-424
Plant and Soil - Mycorrhizal type has been proposed as an effective trait integrator capturing varying biogeochemical syndromes in terrestrial ecosystems. However, for boreal peatlands, it is still...  相似文献   
995.
Yin  Yulin  Zhang  Peijun  Liu  Jia  Wang  Nan  Shang  Xinchi  Zhang  Yilin  Li  Yuehong 《Biological trace element research》2020,194(2):552-559
Biological Trace Element Research - Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments on a global scale. Vitamin C was a widely used vitamin in aquaculture....  相似文献   
996.
Plant Cell, Tissue and Organ Culture (PCTOC) - Tree peony (Paeonia sect. Moutan) is a world famous ornamental and economically important species, but it is recalcitrant to in vitro regeneration....  相似文献   
997.
Zhang  Nan  Gao  Xiaochen  Zhang  Weijia  Higazy  Doaa  Wang  Ke  Fu  Zhenfang  Cui  Min 《Molecular biology reports》2020,47(2):1393-1398
Molecular Biology Reports - Peroxynitrite is an ion acting as a powerful oxidant and nucleophile, which plays a key role in the inflammation and aging process by nitrating tyrosine or tryptophan...  相似文献   
998.
999.
1000.
[首页] « 上一页 [95] [96] [97] [98] [99] 100 下一页 » 末  页»
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