全文获取类型
收费全文 | 36652篇 |
免费 | 2936篇 |
国内免费 | 2476篇 |
专业分类
耳鼻咽喉 | 299篇 |
儿科学 | 405篇 |
妇产科学 | 350篇 |
基础医学 | 3761篇 |
口腔科学 | 576篇 |
临床医学 | 5400篇 |
内科学 | 4663篇 |
皮肤病学 | 433篇 |
神经病学 | 1492篇 |
特种医学 | 1024篇 |
外国民族医学 | 19篇 |
外科学 | 2946篇 |
综合类 | 7661篇 |
现状与发展 | 6篇 |
一般理论 | 4篇 |
预防医学 | 3063篇 |
眼科学 | 850篇 |
药学 | 4132篇 |
45篇 | |
中国医学 | 2124篇 |
肿瘤学 | 2811篇 |
出版年
2024年 | 108篇 |
2023年 | 473篇 |
2022年 | 1318篇 |
2021年 | 1792篇 |
2020年 | 1446篇 |
2019年 | 1089篇 |
2018年 | 1079篇 |
2017年 | 1118篇 |
2016年 | 996篇 |
2015年 | 1675篇 |
2014年 | 2212篇 |
2013年 | 2150篇 |
2012年 | 3025篇 |
2011年 | 3253篇 |
2010年 | 2444篇 |
2009年 | 1994篇 |
2008年 | 2247篇 |
2007年 | 2249篇 |
2006年 | 2103篇 |
2005年 | 1777篇 |
2004年 | 1100篇 |
2003年 | 1001篇 |
2002年 | 857篇 |
2001年 | 676篇 |
2000年 | 672篇 |
1999年 | 636篇 |
1998年 | 375篇 |
1997年 | 428篇 |
1996年 | 281篇 |
1995年 | 264篇 |
1994年 | 231篇 |
1993年 | 126篇 |
1992年 | 150篇 |
1991年 | 134篇 |
1990年 | 125篇 |
1989年 | 73篇 |
1988年 | 93篇 |
1987年 | 86篇 |
1986年 | 58篇 |
1985年 | 49篇 |
1984年 | 34篇 |
1983年 | 21篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1964年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
淡黄香茶菜地下部位化学成分 总被引:1,自引:0,他引:1
目的: 研究淡黄香茶菜Isodon flavida地下部分的主要化学成分. 方法: 采用硅胶、葡聚糖凝胶Sephadex LH-20,MCI 树脂等多种柱色谱技术进行分离纯化,运用理化性质和现代波谱技术鉴定结构. 结果: 从淡黄香茶菜地下部分的70%丙酮提取物的乙酸乙酯部位分离鉴定11个化合物,分别为角鲨烯(1),豆甾-4-烯-3-酮(2),豆甾-4-烯-3,6-二酮(3),8(17),13-ent-labdadien-15→16-lactone-19-oic acid(4),1-油酸单甘油酯(5),2α-羟基-乌索酸(6),山楂酸(7),2α,3α,23-三羟基乌苏-12,20(30)-二烯-28-酸(8),豆甾醇(9),7α-羟基谷甾醇(10),β-谷甾醇(11). 结论: 除化合物7外均为首次从该植物中分离得到.本研究对于深入了解认识香茶菜属植物地下部分的化学品质具有一定的帮助. 相似文献
82.
望面色是望诊的主要内容之一,为了加强学生望面色这一诊断方法的学习效果,在征得学生同意,自愿参加的前提下,在学生中找典型面色进行真实案例教学,调动了学生学习积极性,取得了良好教学效果,实现了教学相长。 相似文献
83.
目的建立去卵巢大鼠模型,观察性激素水平改变对泪腺中IL-17A以及IL-1β、IL-6、TNF-α等炎症因子表达的影响。方法实验研究。健康雌性SD大鼠20只随机分为2组,实验组(10只)摘除大鼠双侧卵巢,对照组(10只)为未摘除卵巢的模拟手术组。术前及术后第1个月、第2个月、第3个月时2组均行泪液分泌试验(SIT)、角膜荧光染色检查进行眼表评估。于第3个月时放射免疫分析法分别检测2组大鼠血清雌二醇、睾酮含量,HE染色观察泪腺上皮细胞形态,免疫组化染色法、Western Blot法检测2组泪腺中IL-17A、IL-1β、IL-6、TNF-α的表达。2组性激素质量浓度比较、炎症因子A值表达比较均应用独立样本t检验。2组各时间点的SIT结果比较采用重复测量资料两因素方差分析。结果实验组大鼠去卵巢后第3个月时,体内雌二醇浓度低于对照组(t=-35.37,P<0.01),睾酮浓度低于对照组(t=-12.13,P<0.01)。2组各时期SIT检查未见泪液分泌减少、均未见角膜荧光染色。HE染色见实验组泪腺腺泡萎缩,排列紊乱,胞质内酶原颗粒明显减少。泪腺IL-17A表达量2组比较实验组高于对照组(免疫组化法:t=7.56,P<0.01;Western Blot法:t=20.90,P<0.01)。余各因子表达量实验组也均高于对照组(免疫组化法:IL-1β:t=13.71,P<0.01;IL-6:t=13.92,P<0.01;TNF-α:t=6.11,P<0.01。Western Blot法:IL-1β:t=16.93,P<0.01;IL-6:t=12.46,P<0.01;TNF-α:t=14.47,P<0.01)。结论大鼠去卵巢3个月时性激素水平降低,未见明显眼表损害。但泪腺中炎症因子IL-17A、IL-1β、IL-6、TNF-α的表达增加。 相似文献
84.
Objective: To calculate ocular residual astigmatism (ORA) by vector analysis and to evaluate the impact of ocular residual astigmatism on refractive and visual outcomes after correction of myopic astigmatism by small incision lenticule extraction (SMILE). Methods: In this prospective case-series study, 115 eyes with myopic astigmatism were treated with SMILE from Jauary 2019 to August 2019 atRefractive Center of Ophthalmology Department, Shengjing Hospital, China Medical University. ORA was calculated by vector analysis and patients were divided into two groups according to the magnitude of ORA: high ORA group (ORA≥1.00 D) with 42 eyes and low ORA group (ORA<1.00 D) with 73 eyes. The follow-up period was 3 months after the operation. Uncorrected visual acuity (UCVA) and pythagorean length were measured and compared after the operation. The following measurements were compared: refractive outcomes, total higher order aberrations (tHOAs), vertical trefoil, vertical coma, horizontal coma, oblique trefoil, oblique quadrafoil, oblique secondary astigmatism, spherical aberration, vertical secondary astigmatism, and vertical quadrafoil. Contrast sensitivity was compared between the high and low ORA groups under either 85 cd/m2 or 3 cd/m2 illumination from 1.5 c/d to 18 c/d. The data were analyzed by an independent-samples t test and Mann-Whitney U test to compare the differences between the two groups. Results: Three months postoperatively, refractive outcomes showed that postoperative residual astigmatism in the high ORA group was significantly higher than in the low ORA group (t=3.293, P=0.001). Vector analysis showed that the error vector (EV), absolute error of angle (absolute EA) and index of success (SI) were higher in the high ORA group (t=-3.235, P=0.001; t=-2.326, P=0.020; t=-2.587, P=0.010). After SMILE,all cases had achieved a desirable visual acuity: high ORA group: -0.15±0.05, low ORA group: -0.15±0.05. There were no statistically significant differences in visual acuity, pythagorean length, tHOAs, vertical trefoil, vertical coma, horizontal coma, oblique trefoil, oblique quadrafoil, oblique secondary astigmatism, spherical aberration, vertical secondary astigmatism, or vertical quadrafoil between the two groups. An obvious difference was found in contrast sensitivity, which showed a higher contrast sensitivity at a spatial frequency of 18 c/d with 85 cd/m2 in the low ORA group than in the high ORA group (t=-2.877, P=0.005), but this tendency was not present at 3 cd/m2 . Conclusions: Ocular residual astigmatism impacts the precision of SMILE in correcting myopic astigmatism. This leads to a tendency of more residual astigmatism in refractive outcomes, and reduces contrast sensitivity at high spatial frequencies. However, it does not affect the outcome of obtaining good visual quality in both visual acuity and higher order aberrations. 相似文献
85.
目的 研究不同子宫内膜癌Ⅲa期患者的预后 ,为临床治疗提供依据。方法 对 1988~ 2 0 0 1年在我院收治的子宫内膜癌Ⅰ期、Ⅲ期患者共 191例进行回顾性分析。患者共分为四组 :第一组为Ⅰ期患者 ,共134例 ;第二组为单纯腹腔细胞学阳性的子宫内膜癌Ⅲa期患者 ,共 2 3例 ;第三组为伴有浆膜浸润或附件转移的子宫内膜癌Ⅲa期患者 ,共 16例 ;第四组为子宫内膜癌Ⅲb期 Ⅲc期患者 ,共 18例。采用Kaplan -Meier法对四组的平均生存时间进行计算 ,并进行比较。结果 ①第一组与第二组的平均生存时间差异无显著性 ,P >0 0 5 ;②第二组与第三组的平均生存时间差异有明显统计学意义 ,P <0 0 1;③第三组与第四组的平均生存时间差异无显著性 ,P >0 0 5。结论 尽管腹腔细胞学阳性、浆膜浸润及附件转移均被定为子宫内膜癌Ⅲa期 ,但单纯腹腔细胞学阳性的患者其预后明显好于伴有浆膜层浸润或附件转移者。对她们应采取不同的后续治疗 相似文献
86.
Hua Qiao Xiaoyun Zhang Ting Wang Li Liang Wei Chang Huxiong Xia 《Pharmaceutical biology》2014,52(2):228-236
Context: Isoliquiritigenin (ISL) has been shown to exhibit a variety of biological activities. However, there is little research on the pharmacokinetic behavior and tissues distribution of ISL.Objective: Pharmacokinetics, biodistribution and bioavailability of ISL after intravenous and oral administration were determined by systematic investigation in Sprague–Dawley rats.Materials and methods: ISL was dissolved in medicinal ethanol-Tween 80–0.9% sodium chloride saline in a volume ratio of 10:15:75. The ISL solution was injected in rats via a tail vein at a single dose of 10, 20 and 50?mg/kg and administered orally in rats at a single dose of 20, 50 and 100?mg/kg, respectively. Blood samples were collected at time intervals of 0.08, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 6, 8 and 12?h after intravenous injection. Tissues of interests in mice were collected immediately at each determined time point (0.5, 1, 2, 3 and 6?h) after cervical dislocation.Results: The dose-normalized AUC values were 7.3, 7.6 and 8.7?μg?×?h/ml (calculated based on the dose of 10?mg/kg) for intravenous doses of 10, 20 and 50?mg/kg, respectively. The elimination half-lifes (t1/2λ) were 4.9, 4.6 and 4.8?h at 10, 20 and 50?mg/kg intravenous doses, respectively. The F values were 29.86, 22.70, 33.62% for oral doses of 20, 50 and 100?mg/kg, respectively. Liver, heart and kidney were major distribution tissues of ISL in mice. The plasma protein binding of ISL in rats was 43.72%.Conclusion: The work may useful for further study of the bioactive mechanism of ISL. 相似文献
87.
目的观察抑酸药(法莫替丁、鼠李铋镁)对马来酸多潘立酮(健胃药)在健康人体药代动力学的影响。方法10名健康受试者未服和服用抑酸药后,单剂量口服马来酸多潘立酮10mg,用LC/MS/MS测定血药浓度,用Win-NonLin5.0软件计算药代动力学参数,并用Spss12.0软件比较主要药代动力学参数。结果未服和服用抑酸药后,单剂量口服马来酸多潘立酮,其药代动力学参数如下:tmax分别为(0.85±0.24)、(2.20±1.78)h,Cmax分别为(9.68±5.37)、(7.18±4.12)μg.L-1,AUC0~tn分别为(38.18±19.76)、(49.96±10.35)μg.h.L-1。显示服用抑酸药后,马来酸多潘立酮的tmax延长,有显著性差异(P=0.04);AUC0-tn增加,峰浓度降低,但无显著性差异(分别为P=0.1、0.06)。结论在健康人体内,法莫替丁、鼠李铋镁不影响马来酸多潘立酮的吸收程度;但使其吸收速度减慢。 相似文献
88.
Quanchen Xu Yuanxin Miao Jizheng Ren Yu Sun Cong Li Xia Cai Zhiguo Wang 《International wound journal》2022,19(5):978
Mechanical force plays a pivotal role in the pathogenesis of hypertrophic scar (HTS). Dermal fibroblasts and myofibroblasts are the key cells involved in HTS. Myofibroblasts in HTS possess different biochemical and biophysical characteristics by which myofibroblasts are often distinguished from fibroblasts. The role of mechanotransducers outside the nucleus in the pathogenesis of HTS has been reported in many studies. However, the role of Nesprin‐2 in HTS is not clear. Hence, we aim to construct a cell model of HTS and explore the role of Nesprin‐2 in this process. Myofibroblasts and fibroblasts were isolated from HTS and healthy skin tissues of the same patient. Fibroblasts were exposed to cyclic stretch with 10% magnitude and a frequency of 0.1 Hz for 3 days, 5 days, and 7 days, respectively. After the cell model was confirmed, fibroblasts transfected with siRNA targeting human Nesprin‐2 were exposed to cyclic stretch. The mechanical behaviour and biochemical reaction of the dermal fibroblasts were analysed. The stretched fibroblasts at day 5 showed the same mechanotransductive and biochemical features as unstretched myofibroblasts. Mechanical strain could induce the myofibroblasts differentiation and a cell model of HTS was established successfully at day 5. The expressions of lamin A/C, alpha‐smooth muscle actin, transforming growth factor beta 1, and collagen type I in fibroblasts were reduced by the silencing of Nesprin‐2. Mechanical strain could induce the myofibroblasts differentiation and silencing of Nesprin‐2 could block the mechanical stimulation of terminal myofibroblasts differentiation. Nesprin‐2 might be a potential target to treat the HTS. 相似文献
89.
Fatigue Cracking Evolution and Model of Cold Recycled Asphalt Mixtures during Different Curing Times
This paper aims to investigate the fatigue cracking evolution of cold recycled asphalt mixtures with asphalt emulsion (CRME) under different curing times. The fatigue cracking model of CRME based on damage mechanics and fracture mechanics was analyzed according to the fatigue loading curve. Firstly, the fatigue cracking evolution of CRME was studied through an SCB strength test and SCB fatigue test. Then, the fatigue damage mechanics were used to establish a nonlinear fatigue cracking model, and the damage degree of CRME at the initial cracking point was determined. The Paris formula was used to characterize the law of fatigue crack propagation. Finally, the microstructure of CRME was observed by scanning electron microscopy (SEM) with the backscattering method. The results indicate that the initial cracking point appears at around 60% of the fatigue life according to the SCB fatigue test by means of image analysis. The damage variable was obtained through the cracking model, and the value of the damage variable was determined as 0.06–0.17 at the initial cracking point. In addition, the Paris formula showed that the crack growth of CRME can be reflected by the stress intensity factor and correlative parameters. Moreover, cement hydration products were mixed with the asphalt membrane to form a denser spatial structure during the curing process, which may provide higher fatigue performance of CRME. This research may provide a theoretical reference for studying the fatigue cracking behavior of CRME. 相似文献
90.
Energy harvesting devices made of piezoelectric material are highly anticipated energy sources for power wireless sensors. Tremendous efforts have been made to improve the performance of piezoelectric energy harvesters (PEHs). Noticeably, topology optimization has shown an attractive potential to design PEHs with enhanced energy conversion efficiency. In this work, an alternative yet more practical design objective was considered, where the open-circuit voltage of PEHs is enhanced by topologically optimizing the through-thickness piezoelectric material distribution of plate-type PEHs subjected to harmonic excitations. Compared to the conventional efficiency-enhanced designs, the open-circuit voltage of PEHs can be evidently enhanced by the proposed method while with negligible sacrifice on the energy conversion efficiency. Numerical investigations show that the voltage cancellation effect due to inconsistent voltage phases can be effectively ameliorated by optimally distributed piezoelectric materials. 相似文献