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   340950篇
  免费   30946篇
  国内免费   8453篇
耳鼻咽喉   4284篇
儿科学   5402篇
妇产科学   4685篇
基础医学   30283篇
口腔科学   11146篇
临床医学   32692篇
内科学   32320篇
皮肤病学   4064篇
神经病学   18040篇
特种医学   9950篇
外国民族医学   29篇
外科学   28283篇
综合类   56211篇
现状与发展   22篇
一般理论   26篇
预防医学   47563篇
眼科学   3801篇
药学   40454篇
  855篇
中国医学   35075篇
肿瘤学   15164篇
  2024年   1227篇
  2023年   6125篇
  2022年   11682篇
  2021年   16462篇
  2020年   15975篇
  2019年   15971篇
  2018年   14395篇
  2017年   13747篇
  2016年   13422篇
  2015年   12664篇
  2014年   24221篇
  2013年   24677篇
  2012年   21623篇
  2011年   22690篇
  2010年   17806篇
  2009年   15751篇
  2008年   14776篇
  2007年   14970篇
  2006年   12823篇
  2005年   10958篇
  2004年   9006篇
  2003年   8109篇
  2002年   6330篇
  2001年   5585篇
  2000年   4678篇
  1999年   3965篇
  1998年   3396篇
  1997年   3039篇
  1996年   2552篇
  1995年   2401篇
  1994年   2223篇
  1993年   1844篇
  1992年   1748篇
  1991年   1544篇
  1990年   1350篇
  1989年   1342篇
  1988年   1206篇
  1987年   1054篇
  1986年   932篇
  1985年   2295篇
  1984年   2460篇
  1983年   1540篇
  1982年   1994篇
  1981年   1397篇
  1980年   1214篇
  1979年   1077篇
  1978年   860篇
  1977年   661篇
  1976年   801篇
  1975年   532篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
961.
率先在国内应用PCR技术扩增Wilson病(WD)基因内部D13S301位点的微卫星多态,通过变性聚丙烯酰胺凝胶电泳检测扩增产物,对80名正常中国人进行了检测,结果具有12种不同长度的等位片段,多态信息含量(PIC值)为0.883,表明该位点在中国人群中具有长度多态性及较高的应用价值。应用该位点对10个WD家系进行连锁分析,在24名无症状个体中检出12名基因携带者,7名正常纯合子及2名症状前患者,进一步证实该位点可用于WD的症状前诊断及杂合子筛选。  相似文献   
962.
A method has been derived for calculating the mean absorption time of an oral drug and its interconversion metabolite which is generated from the drug systemically and presystemically. The method evolves from the convolution integral and requires plasma AUC and AUMC values after separate intravenous administration of the drug and its interconversion metabolite and oral administration of the drug. It can also be used to calculate the mean input time of a drug undergoing reversible metabolism and administered by any other extravascular route. Results of a simulation study using both errorless and errant data indicate that, when the absorption rate constant of a drug or its interconversion metabolite is not much larger than the apparent elimination rate constant, the proposed method performs satisfactorily. However, when the absorption rate constant of a drug or its interconversion metabolite is much larger than the apparent elimination rate constant, the proposed method appears to be inaccurate.  相似文献   
963.
In the attempt to gain a broader understanding of the causal relationships behind work-related symptoms of pain in the human shoulder, monitoring of arm position is crucial. Different methods have been used with varying accuracy. A video-based stereometry system, using infra-red light and reflecting markers for motion analysis, has been introduced for measurements in the fields of ergonomics, biomechanics and sports medicine. The purpose of this study is to investigate the sources of error in using this system for posture registration of the upper limb. Measurements are performed on a calibration fixture, on a mechanical model of the upper limb and on a subject with an exoskeleton. Particular, attention is given to inconsistencies and relative errors due to the finite geometrical precision with which the markers are positioned in the calibration fixture and on the studied objects, the limited capability to align the objects relative to the coordinate system of the calibration fixture and the errors connected to angular measurements using protractors etc. It is concluded that the system makes a valuable addition to existing instruments for non-contact posture measurement, and produces position data with an adequate accuracy in normal handling.  相似文献   
964.
将肺心病、慢性肾炎等338例次的血气分析结果输入计算机,应用我们设计的多结果血气判断微机程序判断酸碱紊乱状态,其结果与人工综合判断结果完全相符。而单结果计算机判断和单纯人工判断的结果与人工综合判断结果的符合率分别为88.2%和87.3%。表明多结果计算机判断程序能有效地避免误判、漏判。  相似文献   
965.
Data from a 1988 national drinking survey was cluster analysedto identify different types of male drinkers, to assist in thetargeting of health promotion strategies. Of the five segmentsgenerated by the clustering, one labelled Young Heavy DrinkingMales was identified as the most appropriate target segment,because although they were the segment reporting the highestlevel of alcohol-related problems they were also the segmentmost likely to feel they were drinking too much They were thereforethe segment most likely to be responsive to advertising thatsought to support people who wanted to change their drinkinghabits. They were also the most appropriate target for the longer-termgoal of changing the climate of opinion regarding the acceptabilityof more moderate drinking. Comparisons with two previous clusteranalyses showed a high degree of similarity, suggesting thatclustering is a reliable vehicle for identifying drinker types.  相似文献   
966.
报告120例羊膜腔穿刺羊水细胞培养结果:在成功的99例中,发现二例染色体异常,核型为47,xy,+18和46,xx/47,xx,+F,在21例失败中出现一例眼球畸形。培养成功率为82.5%;染色体异常检出率为2.02%。无一例因羊膜腔穿刺而导致流产,但出现一例轻度羊水栓塞合并症。并对羊水细胞培养在产前宫内诊断中应用价值及术后并发症进行了讨论。  相似文献   
967.
Summary To evaluate the influence of the stomach and the cholinergic system on gallbladder contraction induced by physiological stimuli, the reduction in gallbladder volume in 7 healthy volunteers has been studied by real-time ultrasonography after the oral and intraduodenal administration of olive oil, preceded by pretreatment with cimetropium bromide or placebo. After an overnight fast, each subject swallowed 50 ml olive oil or it was administered through a naso-duodenal tube in the proximal duodenum. Cimetropium bromide 5 mg or placebo was given intravenously under double-blind control.After the placebo pretreatment, gallbladder contraction was greater and faster after intraduodenal oil than after oral oil. Cimetropium bromide decreased the extent, velocity and duration of gallbladder contraction induced by intraduodenal olive oil but it only reduced the velocity of the contraction induced by oil given orally.It is concluded that in normal human subjects the stomach modulates the extent and velocity of postprandial gallbladder contraction and that anticholinergic agents antagonize the gastric and duodenal phases of the response of the gallbladder to a meal.  相似文献   
968.
 Dermal exposures of methanol were administered in a clinical study designed to compare several biological indicators. Four subjects were exposed in five exposure sessions of varying length. In each session, a sequence of measurements of methanol concentrations in blood, breath, and headspace samples of air at exposed and unexposed skin were collected before and after dermal exposures. Skin headspace samples, collected in gas sampling bags, were designed to reflect equilibrium skin: air partitioning. At exposed skin, headspace samples were highly elevated for at least 8 h following exposure, indicating the presence of a methanol reservoir in skin. After exposure, methanol concentrations at exposed skin showed a rapid initial decline, then a slower first-order decrease. Methanol concentrations were clearly detectable in headspace samples at unexposed skin. Substantial transfer from exposed skin occurred due to mechanical contact and washing. When transfer was restricted, surface concentrations at unexposed skin were similar to levels in breath and were strongly correlated to methanol concentrations in blood. While results are preliminary due to the small sample sizes and several unresolved experimental issues, the simple, rapid, and noninvasive skin headspace measurements appear useful as a biological exposure indicator that clearly shows the presence and site of a dermal exposure, and measurements at unexposed skin reflect concentrations in blood. Received: 14 March 1995/Accepted: 3 November 1995  相似文献   
969.
Molecular genetic analysis was performed in a patient with cytochrome b positive X-linked chronic granulomatous disease. A previous Southern blot study, using a cytochrome b heavy chain cDNA as probe, revealed a Pst I restriction fragment pattern for the cytochrome b heavy chain gene (CYBB) different to that of normal individuals. Since restriction length polymorphism with Pst I has never been observed in control individuals and no abnormal restriction fragment patterns in the patient's CYBB was detected with seven other enzymes used, we focussed on the single Pst I site in the CYBB cDNA as being the only mutation site responsible for his disease. A fragment of the patient's cDNA which included the Pst I site was amplified by reverse polymerase chain reaction, and loss of the Pst I site in the fragment was confirmed by incubation with Pst I. Subsequent sequence analysis of the fragment revealed a point mutation in the Pst I site (cytosine to adenine), substituting glutamic acid for alanine at position 57.  相似文献   
970.
取代四氢异喹啉衍生物的合成及其生物活性   总被引:7,自引:0,他引:7  
粉防己碱有钙拮抗作用,临床试用于治疗高血压,其裂解产物钙拮抗作用降低,但有α-肾上腺素能受体拮抗作用,本文以裂解物为先导化合物设计合成了两类取代的四氢异喹啉衍生物Ⅲ及Ⅳ。初步药理试验表明:大部分化合物有α-肾上腺素能受体拮抗作用,少数化合物钙拮抗活性有所增强,其中Ⅲ15,19对正常麻醉大鼠有一定的降压作用、Ⅳ17,19对实验性动物心律失常有明显的保护作用。部分化合物量化计算表明:化合物与α1-受体作用方式可能是形成电荷转移复合物。  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