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   561篇
  免费   74篇
  国内免费   51篇
耳鼻咽喉   6篇
儿科学   11篇
妇产科学   4篇
基础医学   89篇
口腔科学   12篇
临床医学   169篇
内科学   83篇
皮肤病学   19篇
神经病学   11篇
特种医学   39篇
外科学   54篇
综合类   14篇
一般理论   1篇
预防医学   51篇
眼科学   25篇
药学   79篇
中国医学   1篇
肿瘤学   18篇
  2023年   3篇
  2022年   6篇
  2021年   9篇
  2020年   8篇
  2019年   11篇
  2018年   12篇
  2017年   7篇
  2016年   17篇
  2015年   19篇
  2014年   19篇
  2013年   25篇
  2012年   24篇
  2011年   44篇
  2010年   31篇
  2009年   23篇
  2008年   26篇
  2007年   61篇
  2006年   34篇
  2005年   14篇
  2004年   14篇
  2003年   12篇
  2002年   19篇
  2001年   19篇
  2000年   13篇
  1999年   16篇
  1998年   16篇
  1997年   17篇
  1996年   15篇
  1995年   7篇
  1994年   9篇
  1993年   15篇
  1992年   9篇
  1991年   15篇
  1990年   11篇
  1989年   8篇
  1988年   11篇
  1987年   8篇
  1986年   5篇
  1985年   7篇
  1984年   5篇
  1983年   6篇
  1982年   9篇
  1981年   3篇
  1980年   2篇
  1979年   4篇
  1977年   4篇
  1974年   4篇
  1969年   2篇
  1963年   1篇
  1882年   1篇
排序方式: 共有686条查询结果,搜索用时 15 毫秒
121.
目的:探讨马利兰导致继发再障的原因及安全使用马利兰的方法。方法:通过6例因慢粒而使用马利兰治疗后导致继发再障临床资料分析。结果:马利兰导致继发再障与药物剂量、用药时间及个体敏感性有关。结论:遵循小剂量、长疗程的原则使用马利兰治疗慢粒,可减少继发再障的发生。  相似文献   
122.
Alternating poly(Glu-Leu) was synthesized by the condensation of the corresponding dipeptide p-nitrophenyl ester at high concentration. It exhibits a random coil structure in pure water at neutral pH. Addition of monovalent cations, such as NH+4 to a final 0.1 M solution, induces a transition to a water soluble β-structure. The salt effect is quite selective since no transition was observed with Li+, Na+ or Cs+ ions. Addition of 0.5 equiv. of calcium, cobalt or manganese chlorides per glutamyl residue induces similar coil to β-sheet transitions. No polymer precipitation was observed at these very low salt concentrations. Addition of 0.5 equiv. of Cu2+ or 0.15 equiv. of Fe3+ induces a coil to α-helix transition. Molecular modeling has been used to understand tentatively the main factors controlling the different conformations observed with the various metal ions. © Munksgaard 1997.  相似文献   
123.
124.
1. Fifty-five intact and six baroreceptor denervated and vagotomized cats of either sex were anaesthetized intraperito-neally with urethane (400 mg/kg) and a-chloralose (40 mg/kg). Responses of the systemic arterial pressure (SAP), mean SAP (MSAP) and sympathetic vertebral nerve (VNA) and renal nerve activities (RNA) were recorded. 2. In intact animals, monosodium L-glutamate (Glu, 0.1 mol/L, 50 nL) was microinjected into pressor areas of the locus coeruleus (LC), gigantocellular tegmental field (GTF), rostral ventrolateral medulla (RVLM) and dorsomedial medulla (DM), and the depressor areas of caudal ventrolateral medulla (CVLM). The induced actions were compared before and after microinjection of either glutamate antagonists, glutamate diethylester (GDEE, 0.5 mol/L, 50–100nL), a competitive AMPA receptor blocker, or 2-amino-5-phosphonovaleric acid (D-AP5, 0.025 mol/L, 50–100 nL), a competitive N-methyl-D-aspartate (NMDA) receptor blocker. GDEE completely blocked the increases of SAP and VNA elicited from all pressor areas. D-AP5 only partially blocked the pressor but slightly blocked VNA and RNA responses from LC, GTF and DM, particularly those from RVLM. Neither GDEE nor D-AP5 blocked the depressor responses of SAP and two nerve activities elicited from CVLM. 3. In baroreceptor denervated animals, NMDA (2 mmol/L, 50–100 nL) and AMPA (0.2 mmol/L, 50–100 nL) were micro-injected into the same pressor areas of GTF, RVLM and DM and the depressor area of CVLM responsive to Glu activation (0.1 mol/L, 30 nL). In RVLM, DM and CVLM, the results of either NMDA or AMPA were similar to those induced by Glu. However, in GTF, microinjection of either NMDA or AMPA did not induce similar responses to Glu. This suggests that the nature of GTF may differ from RVLM and DM. 4. The above results suggest that the Glu-induced pressor responses from LC, GTF, DM and especially RVLM, are primarily mediated through AMPA receptors. The Glu-induced depressor responses from CVLM may not be predominantly mediated by either AMPA or NMDA receptors. 5. In both baroreceptor-intact and -denervated cats stimulation of the pressor areas often produced an increase of VNA and a decrease of RNA, while in the depressor CVLM decreased both VNA and RNA. The VNA, but not RNA were positively correlated with the pressor responses, while both VNA and RNA were positively correlated with the depressor responses. This may suggest that neurons of the sympathetic vertebral and renal nerves are topographically organized in the brain.  相似文献   
125.
本文报道了14个6-取代苯基-4,5-二氢-3(2H)哒嗪酮和15个6-取代苯基-3(2H)哒嚎酮的合成及其抗电惊活性。其ED50值表明,以2′,4′-二氯苯基-3(2H)哒嗪酮的抗惊作用为最强。构效分析表明,苯环上的取代基对化合物的抗惊活性有明显影响,吸电子取代基和疏水性参数值较大的取代基有利于提高化合物的抗惊活性。  相似文献   
126.
6-取代苯基哒嗪的3位γ-氨基丁酸衍生物的合成及抗惊活性   总被引:1,自引:0,他引:1  
徐萍  王书玉  刘维勤 《药学学报》1991,26(9):650-655
GABA的合成类似物是开发新型抗惊剂和抗癫痫药物的新领域。由芳香醛与吗啉、氰化钾反应形成的α-芳基-α-(4-吗啉)乙腈,可对α,β-不饱和腈或酯进行1,4-加成,生成1,4-酮酸型化合物。此物与肼缩合,再经芳构化即得6-芳基-3(2H)哒嗪酮。后者再经氯化后。与GABA缩合,制备3-(N-GABA)-6-芳基哒嗪类及其分子内脱水产物3-(N-丁内酰胺)-6-芳基哒嗪类化合物。本文应用此法合成了17个上述苯代哒嗪的GABA衍生物,并初步测验了它们的抗惊(MES)活性。活性最强的是3-(N-GABA)-6-(2′,4′-二氯苯基)哒嗪(ED50=21.05mg/kg)。  相似文献   
127.
本文报道了一系列N-[-1(2-苯乙基-4-甲氧羰基-4-哌啶基]-N-丙酰苯胺(4-甲氧羰基芬太尼)哌啶环1位取代衍生物的合成及其镇痛活性;讨论了结构与镇痛活性之间的关系。药理试验结果表明,大部分化合物具有典型的吗啡样镇痛活性,是一类作用极强的麻醉性镇痛剂。特别是哌啶环1位β-苯环被取代乙烯基替代的化合物具有相当或接近子母体化合物的镇痛活性。其代表物1321的镇痛活性(ED_(50)=0.005mg/kg ip,小鼠,热板法)略强于4-甲氧羰基芬太尼(ED_(50)=0.0063 mg/kg)。  相似文献   
128.
本文介绍以光学活性苏-1-(对硝基苯基)-1,3-二羟基丙胺-2为拆分剂,与消旋棉酚缩合,用常压柱色谱或溶剂结晶法分离得到两个光学纯的非对映体,然后分别水解得(+)和(-)-棉酚。  相似文献   
129.
The purpose of this study was to investigate the impact of post-mortem computed-tomography angiography (PMCTA) on the histology of the liver, kidneys and heart. Multiple tissue cores were collected from the liver, left and right kidneys and left ventricle utilizing CT-guided biopsy. Subsequent whole body PMCTA was performed using a solution of polyethylene glycol and iodinated radiographic contrast, and an embalming pump. Corresponding biopsy cores were collected at autopsy, and blinded histology analysis assessing for PMCTA-induced histology artefact was performed. The blinded analysis of pre-PMCTA and post-PMCTA biopsy samples demonstrated that whole body PMCTA had no effect on the histological analyses of the liver (0%, CI = 0–13.7%), left ventricle of the heart (0%, CI = 0–36.9%) and right kidney (0%, CI = 13.2%), however likely caused increased Bowman’s capsule spaces in the left kidney of one case (4%, CI = 0.01–20.4%). Other artefactual histological changes identified included eosinophilic material in the liver, whiter interstitium and dilated tubules in kidney samples, and autolysis-related changes, however these could not be categorically attributed to the PMCTA procedure. PMCTA causes zero or minimal effect to the histological examination of the liver, left kidney, right kidney and left ventricle, and as such performing PMCTA prior to autopsy is unlikely to impact autopsy histological results in these organs.  相似文献   
130.
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