全文获取类型
收费全文 | 7249篇 |
免费 | 435篇 |
国内免费 | 189篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 128篇 |
妇产科学 | 30篇 |
基础医学 | 599篇 |
口腔科学 | 138篇 |
临床医学 | 619篇 |
内科学 | 1707篇 |
皮肤病学 | 78篇 |
神经病学 | 263篇 |
特种医学 | 246篇 |
外科学 | 649篇 |
综合类 | 985篇 |
现状与发展 | 1篇 |
预防医学 | 597篇 |
眼科学 | 20篇 |
药学 | 1270篇 |
2篇 | |
中国医学 | 355篇 |
肿瘤学 | 159篇 |
出版年
2024年 | 9篇 |
2023年 | 85篇 |
2022年 | 427篇 |
2021年 | 504篇 |
2020年 | 187篇 |
2019年 | 170篇 |
2018年 | 159篇 |
2017年 | 210篇 |
2016年 | 234篇 |
2015年 | 275篇 |
2014年 | 384篇 |
2013年 | 529篇 |
2012年 | 342篇 |
2011年 | 439篇 |
2010年 | 351篇 |
2009年 | 321篇 |
2008年 | 371篇 |
2007年 | 324篇 |
2006年 | 260篇 |
2005年 | 285篇 |
2004年 | 218篇 |
2003年 | 200篇 |
2002年 | 223篇 |
2001年 | 119篇 |
2000年 | 95篇 |
1999年 | 114篇 |
1998年 | 86篇 |
1997年 | 78篇 |
1996年 | 92篇 |
1995年 | 80篇 |
1994年 | 88篇 |
1993年 | 40篇 |
1992年 | 68篇 |
1991年 | 65篇 |
1990年 | 41篇 |
1989年 | 53篇 |
1988年 | 37篇 |
1987年 | 33篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 34篇 |
1983年 | 27篇 |
1982年 | 22篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 6篇 |
排序方式: 共有7873条查询结果,搜索用时 15 毫秒
81.
目的探讨柿叶总黄酮(PLF)对四氯化碳(CCl 4)诱导的小鼠急性肝损伤的保护作用。方法采用CCl 4肝损伤模型,测定小鼠血清中谷丙转氨酶(ALT)和谷草转氨酶(AST)的含量及肝组织中超氧化物歧化酶(SOD)、脂质过氧化物丙二醛(MDA)、还原型谷胱甘肽(GSH)和肿瘤坏死因子-α(TNF-α)的含量,HE染色观察肝脏组织病理形态学的改变。结果PLF高、中、低剂量组均能降低肝损伤小鼠ALT和AST的含量,提高肝组织SOD和GSH含量,降低MDA和TNF-α含量,并能改善肝组织的病理损伤程度。结论PLF对CCl 4所致的小鼠肝损伤有较好的保护作用,其作用机制可能与提高小鼠的抗脂质氧化能力有关。 相似文献
82.
重组牛胰蛋白酶抑制剂对四氯化碳致大鼠慢性肝损伤的保护作用 总被引:1,自引:0,他引:1
目的观察重组牛胰蛋白酶抑制剂(rBPTI)对大鼠慢性肝损伤的保护作用。方法大鼠98只,随机分成7组,分别为正常对照组、模型组、rBPTI3个剂量组(20,40和80MU.kg-1)、抑肽酶组(80MU.kg-1)和促肝细胞生长素组(100mg.kg-1)。除正常对照组外,其余各组皮下注射四氯化碳制备慢性肝损伤模型。8周后每天ip给药,给药4周后测定血清谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性、白蛋白(Alb)含量、白蛋白/球蛋白(A/G)比值、唾液酸(SA)含量及肝组织羟脯氨酸(Hyp)含量,并进行组织病理学检测。结果与正常对照组比较,模型组大鼠血清GPT和GOT活性、SA含量及肝组织Hyp含量明显升高,血清Alb含量和A/G比值明显降低。与模型组比较,rBPTI各剂量组大鼠血清GPT和GOT活性、SA含量及肝组织Hyp含量降低,血清Alb含量和A/G比值明显增高。肝组织病理观察显示,rBPTI明显减轻由四氯化碳所致肝细胞脂肪变性及纤维组织增生等病理改变。结论rBPTI对四氯化碳诱导的大鼠慢性肝损伤具有保护作用和抗纤维化作用,在所观察的剂量范围内作用效果与抑肽酶相当。 相似文献
83.
巴曲酶的扩血管作用及其机制探讨 总被引:61,自引:1,他引:61
目的研究巴曲酶对血管张力的影响及其可能机制。方法离体大鼠主动脉环测定张力,主动脉薄片孵育测定NO生成、血管一氧化氮合酶(NOS)活性与L-精氨酸(L-Arg)转运。结果巴曲酶(0.1~20Bu·L-1)浓度依赖性扩张大鼠离体主动脉环,去内皮血管对巴曲酶的舒张反应明显低于内皮完整血管(P<0.01),最大舒张反应分别为40.1%±21.9%和88.1%±4.2%(P<0.01)。巴曲酶(10Bu·L-1)刺激孵育主动脉产生NO-2增加128%(P<0.01),固有型NOS(cNOS)和总NOS(tNOS)活性分别增加2.0倍和40.0%(P值均小于0.01),诱导型NOS(iNOS)活性无显著变化(P>0.05)。血管壁对L-Arg的转运呈高和低亲和两种方式,巴曲酶(10Bu·L-1)可使其最大转运速率Vmax分别增加83.8%和47.4%(P<0.01)。结论巴曲酶的内皮依赖的扩血管作用通过L-Arg/NO途径,巴曲酶增加血管壁L-Arg的转运和激活NOS,使NO生成增加 相似文献
84.
85.
大分子壳聚糖对单壁碳纳米管水分散性的影响 总被引:1,自引:0,他引:1
目的 利用大分子壳聚糖改善单壁碳纳米管的水分散性。方法 采用混酸氧化法(浓硫酸∶浓硝酸=3∶1)对单壁碳纳米管进行羧基化处理。冰浴超声分散法制备壳聚糖修饰的单壁碳纳米管并采用紫外分光光度法、红外分光光度法、差示扫描量热法等进行验证。恒温振荡法考察壳聚糖修饰单壁碳纳米管的水分散性。结果 壳聚糖修饰单壁碳纳米管在水、PBS(pH 7.4)及醋酸缓冲液(pH 4.0)中的分散度均有明显增加,分散浓度分别为1.99,2.04,1.76 mg·mL-1。结论 壳聚糖能明显改善单壁碳纳米管的水分散性。 相似文献
86.
Arul Prakash Francis Thiyagarajan Devasena Selvam Ganapathy Venkata Rajsekhar Palla Prakhya Balakrishna Murthy Sundara Ramaprabhu 《Nanomedicine : nanotechnology, biology, and medicine》2018,14(6):1809-1822
Human beings and ecosystems are being possibly exposed to CNTs, as there is a rise in global production rate of carbon nanotubes (CNTs). This may affect the health of humans and increases the environmental risk. We have already reported the pulmonary toxicity due to the inhalation of MWCNTs. We claim that a compound with anti-inflammatory and antioxidant activity may ameliorate the CNT-induced toxic effect. With this view, we have investigated the ameliorative effect of intravenously-administered nano bis-demethoxy curcumin analog (NBDMCA) against MWCNTs-induced inhalation toxicity by examining the lung histopathology for inflammatory cell dynamics, pulmonary remodeling and estimating the inflammatory biomarkers in the broncho-alveolar lavage fluid. We observed that NBDMCA could ameliorate the injury as evidenced by the decline in the levels of markers of inflammation, cell damage, and the histopathological changes induced by MWCNTs. We conclude that NBDMCA may be used to reduce the risk of MWCNTs-induced inhalation toxicity. 相似文献
87.
Effects of heme oxygenase system on the cyclooxygenase in the primary cultured hypothalamic cells 总被引:3,自引:0,他引:3
Hae-Uk Lee Hee-Joo Lee Ha-Young Park Sang-Ho Lee Choon-Gon Jang Seok-Yong Lee 《Archives of pharmacal research》2001,24(6):607-612
Endogenous carbon monoxide (CO) shares with nitric oxide (NO) a role as a putative neural messenger in the brain. Both gases are believed to modulate CNS function via an increase in cytoplasmic cGMP concentrations secondary to the activation of soluble guanylate cyclase (sGC). Recently CO and NO were proposed as a possible mediator of febrile response in hypothalamus. NO has been reported to activate both the constitutive and inducible isoform of the cyclooxygenase (COX). Thus, we investigated whether CO arising from heme catabolism by heme oxygenase (HO) is involved in the febrile response via the activation of COX in the hypothalamus. PGE2 which is a final mediator of febrile response released from primary cultured hypothalamic cells was taken as a marker of COX activity. PGE2 concentration was measured with EIA kits. Exogenous CO (CO-saturated medium) and hemin (a substrate and potent inducer of HO) evoked an increase in PGE2 release from hypothalamic cells, and these effects were blocked by methylene blue (an inhibitor of sGC). And membrane permeable cGMP analogue, dibutyryl-cGMP elicited significant increases in PGE2 release. These results suggest that there may be a functional link between HO and COX enzymatic activities. The gaseous product of hemin through the HO pathway, CO, might play a role through the modulation of the COX activity in the hypothalamus. 相似文献
88.
Distribution of single wall carbon nanotubes in the Xenopus laevis embryo after microinjection 下载免费PDF全文
Kris Noel Dahl Lance A. Davidson Mohammad F. Islam 《Journal of applied toxicology : JAT》2016,36(4):568-578
Single wall carbon nanotubes (SWCNTs) are advanced materials with the potential for a myriad of diverse applications, including biological technologies and large‐scale usage with the potential for environmental impacts. SWCNTs have been exposed to developing organisms to determine their effects on embryogenesis, and results have been inconsistent arising, in part, from differing material quality, dispersion status, material size, impurity from catalysts and stability. For this study, we utilized highly purified SWCNT samples with short, uniform lengths (145 ± 17 nm) well dispersed in solution. To test high exposure doses, we microinjected > 500 µg ml–1 SWCNT concentrations into the well‐established embryogenesis model, Xenopus laevis, and determined embryo compatibility and subcellular localization during development. SWCNTs localized within cellular progeny of the microinjected cells, but were heterogeneously distributed throughout the target‐injected tissue. Co‐registering unique Raman spectral intensity of SWCNTs with images of fluorescently labeled subcellular compartments demonstrated that even at regions of highest SWCNT concentration, there were no gross alterations to subcellular microstructures, including filamentous actin, endoplasmic reticulum and vesicles. Furthermore, SWCNTs did not aggregate and localized to the perinuclear subcellular region. Combined, these results suggest that purified and dispersed SWCNTs are not toxic to X. laevis animal cap ectoderm and may be suitable candidate materials for biological applications. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
89.
目的:建立以微分脉冲伏安(DPV)法测定奥美拉唑片中奥美拉唑含量的方法。方法:分析了奥美拉唑不同电化学分析方法下的不同伏安行为,确定最佳分析方法及条件。结果:最佳分析方法为DPV法,在0.1mol/L醋酸-醋酸钠(HAc-NaAc)缓冲液中奥美拉唑检测浓度在1.0~40.0mg/L范围内与该峰电流值呈良好的线性关系(r=0.9904),其最低检测限为0.19mg/L,回收率为99.3%~102.0%。结论:DPV法测定奥美拉唑含量灵敏度较高,检测限较低,可望成为标准测试方法。 相似文献
90.
David Ramos Jos Cidrs Borja Plaza Carolina Moravec Antonia de la Torre Malte Richard Karl Frvel David Poyatos 《Materials》2022,15(15)
The tendency over the last decades in the aerospace industry is to substitute classic metallic materials with new composite materials such as carbon fiber composites (CFC), fiber glass, etc., as well as adding electronic devices to ensure the safety and proper platform operation. Due to this, to protect the aircraft against the Electromagnetic Environmental Effects (E3), it is mandatory to develop accurate electromagnetic (EM) characterization measurement systems to analyze the behavior of new materials and electronic components. In this article, several measurement methods are described to assess the EM behavior of the samples under test: microstrip transmission line for a surface current analysis, free space to obtain intrinsic features of the materials and shielding effectiveness (SE) approaches to figure out how well they isolate from EM fields. The results presented in this work show how the different facilities from the National Institute of Aerospace Technology (INTA) are suitable for such purposes, being capable of measuring a wide variety of materials, depending on the type of test to be carried out. 相似文献