全文获取类型
收费全文 | 4673篇 |
免费 | 416篇 |
国内免费 | 214篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 28篇 |
妇产科学 | 13篇 |
基础医学 | 113篇 |
口腔科学 | 68篇 |
临床医学 | 243篇 |
内科学 | 597篇 |
皮肤病学 | 36篇 |
神经病学 | 21篇 |
特种医学 | 51篇 |
外国民族医学 | 1篇 |
外科学 | 146篇 |
综合类 | 840篇 |
预防医学 | 298篇 |
眼科学 | 1篇 |
药学 | 1375篇 |
7篇 | |
中国医学 | 1431篇 |
肿瘤学 | 25篇 |
出版年
2024年 | 26篇 |
2023年 | 59篇 |
2022年 | 303篇 |
2021年 | 345篇 |
2020年 | 196篇 |
2019年 | 144篇 |
2018年 | 156篇 |
2017年 | 195篇 |
2016年 | 206篇 |
2015年 | 193篇 |
2014年 | 442篇 |
2013年 | 413篇 |
2012年 | 360篇 |
2011年 | 381篇 |
2010年 | 236篇 |
2009年 | 202篇 |
2008年 | 183篇 |
2007年 | 177篇 |
2006年 | 155篇 |
2005年 | 128篇 |
2004年 | 108篇 |
2003年 | 98篇 |
2002年 | 99篇 |
2001年 | 88篇 |
2000年 | 66篇 |
1999年 | 43篇 |
1998年 | 47篇 |
1997年 | 35篇 |
1996年 | 37篇 |
1995年 | 29篇 |
1994年 | 34篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有5303条查询结果,搜索用时 9 毫秒
1.
Dry powder inhalers (DPIs) are gaining popularity for the delivery of drugs. A cost effective and efficient delivery device is necessary. Developing new DPIs by modifying an existing device may be the simplest way to improve the performance of the devices. The aim of this research was to produce a new DPIs using computational fluid dynamics (CFD). The new DPIs took advantages of the Cyclohaler® and the Rotahaler®. We chose a combination of the capsule chamber of the Cyclohaler® and the mouthpiece and grid of the Rotahaler®. Computer-aided design models of the devices were created and evaluated using CFD. Prototype models were created and tested with the DPI dispersion experiments. The proposed model 3 device had a high turbulence with a good degree of deagglomeration in the CFD and the experiment data. The %fine particle fraction (FPF) was around 50% at 60?L/min. The mass median aerodynamic diameter was around 2.8–4?μm. The FPF were strongly correlated to the CFD-predicted turbulence and the mechanical impaction parameters. The drug retention in the capsule was only 5–7%. In summary, a simple modification of the Cyclohaler® and Rotahaler® could produce a better performing inhaler using the CFD-assisted design. 相似文献
2.
Solid-state reactions between sodium hydride and sodium hydroxide are unusual among hydride-hydroxide systems since hydrogen can be stored reversibly. In order to understand the relationship between hydrogen uptake/release properties and phase/structure evolution, the dehydrogenation and hydrogenation behavior of the Na-O-H system has been investigated in detail both ex- and in-situ. Simultaneous thermogravimetric-differential thermal analysis coupled to mass spectrometry (TG-DTA-MS) experiments of NaH-NaOH composites reveal two principal features: Firstly, an H2 desorption event occurring between 240 and 380 °C and secondly an additional endothermic process at around 170 °C with no associated weight change. In-situ high-resolution synchrotron powder X-ray diffraction showed that NaOH appears to form a solid solution with NaH yielding a new cubic complex hydride phase below 200 °C. The Na-H-OH phase persists up to the maximum temperature of the in-situ diffraction experiment shortly before dehydrogenation occurs. The present work suggests that not only is the inter-phase synergic interaction of protic hydrogen (in NaOH) and hydridic hydrogen (in NaH) important in the dehydrogenation mechanism, but that also an intra-phase Hδ+… Hδ– interaction may be a crucial step in the desorption process. 相似文献
3.
目的观察补脾泻肝法治疗腹泻型肠易激综合征的临床疗效。方法100例腹泻型肠易激综合征患者随机分为2组,治疗组60例给予白术芍药散加味,对照组40例给予丙咪嗪合替加色罗治疗。2组均4周为1个疗程,观察疗效,并于3-6个月后观察2组病例复发情况。结果治疗组治愈率为65%,总有效率为85%,6个月内复发率为20%,对照组则分别为32.5%、72.5%、55.56%,2组比较差异均有统计学意义(均P<0.05)。结论补脾泻肝法治疗腹泻型肠易激综合征优于丙咪嗪合替加色罗,疗效确切。 相似文献
4.
Simultaneous Quantification of an Enantiomer and the Racemic Compound of Ibuprofen by X-ray Powder Diffractometry 总被引:1,自引:0,他引:1
Purpose. An X-ray powder diffractometric method was developed for the simultaneous quantification of the relative amounts of the racemic compound (±) of ibuprofen (I) and S(+)-ibuprofen (II), when they occur as a mixture.
Methods. The X-ray powder diffraction patterns of I and II show pronounced differences. This formed the basis for the determination of the relative amounts of I and II when they occur as a mixture. X-ray lines with d-spacings of 14.41 and 4.37 Å were unique to I and II, respectively. Mixtures containing different proportions of I and II were prepared which also contained lithium fluoride (III) as an internal standard.
Results. A linear relationship was obtained when the intensity ratio (intensity of the 4.37 Å line of II/intensity of the 2.01 Å line of III) was plotted as a function of the weight fraction of II in the mixture. Similar results were obtained in the case of I. Using these standard curves, the weight fractions of I and II in 'unknown' mixtures were determined. The experimentally determined analyte concentration ranged between 98 and 104% of the true value. The relative error in the analyses of individual samples was < 10%. The minimum detectable weight fraction of I in II and II in I were 0.032 (3.2% w/w) and 0.034 (3.4% w/w), respectively. The minimum quantifiable weight fractions were 0.136 for I and 0.112 for II. Since the X-ray diffraction patterns of S(+)-ibuprofen and R(–)-ibuprofen are identical, the conclusions drawn regarding mixtures of I and II will also hold true in the quantitative analyses of mixtures of I and R(–)-ibuprofen. 相似文献
5.
6.
强化婴幼儿奶粉中叶酸的测定 总被引:1,自引:0,他引:1
强化叶酸的奶粉在0.05M K_2HPO_4缓冲液中,经均质,调pH4.5,15000g离心20分钟,其清液调pH4.0,进行CGS树脂离子交换层析,用10ml KClK_2HPO_4洗脱,调pH7.0,进行HPLC测定,采用300x3.9mm ODS反相柱,移动相0.05M K_2HPO+MeOH(91+9),流速1ml/分,紫外检测器波长285nm,灵敏度0.0050D。方法相对标准偏差为±3.3%,回收率为87%,最小检测量为0.02μg/ml。 相似文献
7.
热力学计算表明,H2,N2的过量有助于提高TiN的产率,但能耗也相应增加。为此考察了温度,流量,TiCl4携带量,混合方式对产物性能的影响。结果表明,流量增加,温度升高,TiCl4携带量增加,混合愈好,则产物粒径愈小。在此基础上采用微波等离子体化学气相沉积法,合成了粒径为123-284nm的TiN超细颗粒 相似文献
8.
9.
本文运用模糊数学原理,对东台市1993年7月份市面上的全脂乳粉抽查监测结果进行卫生质量综合评价,结果令人满意,从而为乳粉卫生质量评比建立了客观有效的评价模型。 相似文献
10.
于淮 《中华临床医学研究杂志》2006,12(17):2279-2280
愈银汤3号存临床银屑病的治疗中作用确定,银屑病在临床中可分为寻常型、脓疱型、关节病型、红皮病型银屑病,其发病原因有很大的不同.在治疗中应辩证治疗。 相似文献