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   220392篇
  免费   20262篇
  国内免费   15479篇
耳鼻咽喉   1904篇
儿科学   2212篇
妇产科学   2989篇
基础医学   26592篇
口腔科学   3690篇
临床医学   30851篇
内科学   33010篇
皮肤病学   2234篇
神经病学   12408篇
特种医学   8305篇
外国民族医学   138篇
外科学   21802篇
综合类   35442篇
现状与发展   55篇
一般理论   19篇
预防医学   13168篇
眼科学   6708篇
药学   22741篇
  194篇
中国医学   12386篇
肿瘤学   19285篇
  2024年   698篇
  2023年   3558篇
  2022年   9198篇
  2021年   11570篇
  2020年   8607篇
  2019年   7596篇
  2018年   8044篇
  2017年   7090篇
  2016年   6658篇
  2015年   10257篇
  2014年   12557篇
  2013年   10711篇
  2012年   16009篇
  2011年   17958篇
  2010年   10539篇
  2009年   8206篇
  2008年   11120篇
  2007年   11099篇
  2006年   11255篇
  2005年   11335篇
  2004年   7036篇
  2003年   6627篇
  2002年   5508篇
  2001年   4939篇
  2000年   5348篇
  1999年   5689篇
  1998年   3549篇
  1997年   3519篇
  1996年   2834篇
  1995年   2633篇
  1994年   2158篇
  1993年   1383篇
  1992年   1895篇
  1991年   1598篇
  1990年   1294篇
  1989年   1104篇
  1988年   1024篇
  1987年   897篇
  1986年   735篇
  1985年   527篇
  1984年   341篇
  1983年   249篇
  1982年   152篇
  1981年   150篇
  1980年   117篇
  1979年   142篇
  1978年   53篇
  1977年   57篇
  1975年   57篇
  1974年   56篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
用分子轨道计算方法研究儿茶素对自由基的清除作用   总被引:11,自引:0,他引:11  
  相似文献   
992.
复方丹参胶囊质量控制标准研究   总被引:7,自引:0,他引:7  
采用 TLC法鉴别复方丹参胶囊中高原丹参、三七及冰片 ;利用薄层扫描法测定高原丹参中丹参酮 A的含量 :甲醇提取液点样 ,石油醚 -醋酸乙酯 -冰醋酸 ( 8∶ 2∶ 0 .5)展开两次 ,4 80 nm扫描法测定。 5批样品每粒胶囊均含丹参酮 A0 .4 59~ 0 .557mg。  相似文献   
993.
目的研究mi R-186靶向PIG11基因抑制胃癌细胞的侵袭。方法首先通过生物信息学方法分析,寻找与PIG11(TP53I11)结合的靶mi RNAs。分别构建mi R-186 mimics、点突变序列(Point mutation,PM)、空白载体(Scramble),转染胃癌MKN-28细胞。q RT-PCR检测mi R-186表达,Western blot检测PIG11表达,分析mi R-186表达和PIG11表达之间的相关性。Transwell检测转染前后各组胃癌MKN-28细胞侵袭能力变化。结果生物信息学发现12个mi RNAs可能是PIG11的潜在靶mi RNAs,其中mi R-186与PIG11结合特异性最好、稳定性最强;MKN-28-mi R-186 mimics细胞株中mi R-186表达增高,而PIG11表达下调,而MKN-28、MKN-28-mi R-Scramble、MKN-28-mi R-186-PM 3个细胞株中mi R-186表达水平较低,而PIG11表达水平较高。MKN-28-mi R-186 mimics侵袭细胞计数明显低于其他3组(P<0.05)。结论 mi R-186有可能靶向结合PIG11,下调其表达并抑制胃癌细胞的侵袭。  相似文献   
994.
指末节断离再植探讨   总被引:3,自引:0,他引:3  
刘锦成 《现代医药卫生》2002,18(12):1060-1060
目的:探讨基层医院无显微吻合技术指末节断离再植的成活率。方法:通过38例45指末节断离再植,采用静脉留置针头鞘多侧孔减压引流,进行临床资料分析探讨。结果:45指末节断离再植,成活37指占82.22%,失败8指占17.77%.结论:指末节断离再植,采用静脉留置针头鞘多侧孔减压引流,起血液循环架桥式的作用,人为建立血液循环,提高指末节断离再植成活率。  相似文献   
995.
996.
1. Astragaloside IV is a component from the widely used traditional Chinese herb Astragalus membranaceus and its effect on rat aortic ring contraction and relaxation were investigated. 2. The aorta from male Sprague-Dawley rats was isolated in an organ bath and ring tension was recorded with or without endothelium. Cumulative effects of astragaloside IV on vessel contraction and relaxation were observed in the presence of various antagonists related to vessel activity. 3. Astragaloside IV showed concentration-dependent inhibition of vessel contraction induced by phenylephrine and potassium chloride. The amount of calcium released from intracellular stores sensitive to phenylephrine was also markedly reduced by astragaloside IV. There was dose-dependent vasorelaxation in endothelium-intact rings, which was partly inhibited by pre-incubation with nitric oxide (NO) synthase (NOS) Nomega-nitro-L-arginine methyl ester and guanylate cyclase inhibitor, 1H-[1,2,4] oxadiazolo [4,3-alpha] quinoxalin-1-one. Astragaloside IV also induced a significant increase in aortic tissue content of guanosine 3",5"-cyclic monophosphate (cGMP) both in vivo and in vitro. Endothelial NOS inhibitor Nomega-nitro-L-arginine prevented vasodilatation, whereas neuronal NOS inhibitor 7-nitroindazole did not show significant influence on the vessel relaxation of astragaloside IV. 4. In conclusion, astragaloside IV inhibited vessel contraction through blocking calcium influx and intracellular calcium release. The endothelium-dependent vessel dilation of astragaloside IV was attributed mainly to the endothelium-dependent NO-cGMP pathway.  相似文献   
997.
A new drug-targeting system for CD13+ tumors has been developed, based on ultrasound-sensitive nanobubbles (NBs) and cell-permeable peptides (CPPs). Here, the CPP-doxorubicin conjugate (CPP-DOX) was entrapped in the asparagine–glycine–arginine (NGR) peptide modified NB (CPP-DOX/NGR-NB) and the penetration of CPP-DOX was temporally masked; local ultrasound stimulation could trigger the CPP-DOX release from NB and activate its penetration. The CPP-DOX/NGR-NBs had particle sizes of about 200?nm and drug entrapment efficiency larger than 90%. In vitro release results showed that over 85% of the encapsulated DOX or CPP-DOX would release from NBs in the presence of ultrasound, while less than 1.5% of that (30?min) without ultrasound. Cell experiments showed the higher cellular CPP-DOX uptake of CPP-DOX/NGR-NB among the various NB formulations in Human fibrosarcoma cells (HT-1080, CD13+). The CPP-DOX/NGR-NB with ultrasound treatment exhibited an increased cytotoxic activity than the one without ultrasound. In nude mice xenograft of HT-1080 cells, CPP-DOX/NGR-NB with ultrasound showed a higher tumor inhibition effect (3.1% of T/C%, day 24), longer median survival time (50 days) and excellent body safety compared with the normal DOX injection group. These results indicate that the constructed vesicle would be a promising drug delivery system for specific cancer treatment.  相似文献   
998.
丹参和透明质酸钠注射液对骨性关节炎治疗作用的实验研究   总被引:22,自引:0,他引:22  
采取家兔膝关节制动方法建立骨性关节炎动物模型,用丹参注射液和透明质酸钠注射液关节腔内注射进行治疗,分别在制动后3、6、9周测量关节活动度,取关节软骨制成标本经光镜和透射电镜观察。结果显示,与单纯制动组比较,丹参治疗组和透明质酸钠治疗组的关节活动度明显改善,关节病变出现晚,程度轻,以早期最明显。表明丹参和透明质酸钠具有延缓和减轻关节退变的作用,对骨性关节炎早期有一定的治疗作用。  相似文献   
999.
A new type of modified lignin, lignin-p-Boc, was obtained through reaction with di-tert-butyl dicarbonate (Boc2O) in aqueous media catalyzed by 4-dimethylaminopyridine (DMAP). Boc modification occurred regardless of type of lignin, was tunable, and proceeded well in recovering lignin at high purity from sodium lignosulfonate (a common byproduct from pulping industry; lignin content: 60%). Lignin-p-BOC was demonstrated as a potential reactive filler in green plastic and as a potential crosslinker in design of bioresorbable composite polymeric implants. Furthermore, the effect of the modification on breakdown rate of alkali lignin by microbes was investigated, and results showed that the modification substantially decreases the breakdown rate. The tunable Boc modification process was designed via a system thinking, including availability of raw lignin, economical/green modification, potentiality of drop-in-change to current thermoplastic processing, modification impact on microbial degradability/disposed environment at the end of use life; hence the holistic consideration makes this alternative method for upgrade of technical lignins very practical for future industrial application. Via “in-situ” forming “easily breakable covalent bonds” with existing thermopolymers inside, Lignin-p-BOCs are also promising to play an important role as both excellent binders via “random match” and reductants in transforming linear plastic waste into circular plastics.  相似文献   
1000.
目的:探讨甲硝唑、维生素B2、珍珠粉等配伍治疗口腔溃疡的疗效.方法:选取200例于2014年6月1日~2016年6月1日我院接收的复发性口腔溃疡患者,随机分为对照组(给予西瓜霜喷剂治疗,n=100)与观察组(采用甲硝唑、维生素B2、珍珠粉等配伍治疗,n=100),观察两组疗效.结果:治疗7d后,观察组临床总有效率较对照组显著要高(P<0.05),复发率显著低于对照组(P<0.05);观察组疼痛感消除时间、溃疡治愈时间均较对照组显著要短(P<0.05);治疗后,两组外周血CD4+、CD4+/CD8+水平明显升高,观察组升高幅度较对照组显著(P<0.05).结论:复发性口腔溃疡采取甲硝唑、维生素B2、珍珠粉、山茶油配伍治疗,疗效显著,具有推广价值.  相似文献   
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