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   16300篇
  免费   999篇
  国内免费   467篇
耳鼻咽喉   227篇
儿科学   156篇
妇产科学   225篇
基础医学   1155篇
口腔科学   1140篇
临床医学   1677篇
内科学   1602篇
皮肤病学   526篇
神经病学   653篇
特种医学   907篇
外国民族医学   2篇
外科学   3535篇
综合类   2398篇
预防医学   796篇
眼科学   274篇
药学   1210篇
  10篇
中国医学   802篇
肿瘤学   471篇
  2024年   50篇
  2023年   261篇
  2022年   505篇
  2021年   624篇
  2020年   541篇
  2019年   480篇
  2018年   450篇
  2017年   450篇
  2016年   506篇
  2015年   483篇
  2014年   867篇
  2013年   901篇
  2012年   772篇
  2011年   997篇
  2010年   933篇
  2009年   748篇
  2008年   768篇
  2007年   801篇
  2006年   729篇
  2005年   649篇
  2004年   543篇
  2003年   504篇
  2002年   385篇
  2001年   311篇
  2000年   304篇
  1999年   285篇
  1998年   269篇
  1997年   237篇
  1996年   204篇
  1995年   223篇
  1994年   208篇
  1993年   182篇
  1992年   152篇
  1991年   174篇
  1990年   151篇
  1989年   122篇
  1988年   134篇
  1987年   103篇
  1986年   103篇
  1985年   104篇
  1984年   101篇
  1983年   63篇
  1982年   101篇
  1981年   52篇
  1980年   64篇
  1979年   35篇
  1978年   32篇
  1977年   29篇
  1976年   25篇
  1974年   17篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Study Objective: To test the hypothesis that slow administration of local anesthetic into the epidural space by gravity flow reduces the incidence of signs and symptoms of unintended injection.

Design: Prospective, randomized study.

Setting: Teaching hospital.

Patients: 600 ASA physical status I and II parturients scheduled for labor and delivery or elective cesarean section.

Interventions: After identification of the epidural space with pulsations of an air-fluid column, parturients for vaginal delivery (n = 380) were randomized to receive a test dose of 3 ml 3% 2-chloroprocaine with epinephrine 20 μg, two doses of 7 ml bupivacaine 0.03 % with sufentanil 1 μg/ml and epinephrine 2 μg/ml by either gravity flow (Group 1) given over 30 seconds or by bolus injection (Group 2) given over 5 seconds through the epidural needle; parturients for Cesarean delivery (n = 220) were randomized to receive a test dose and two doses of 6 ml lidocaine 2 % with sufentanil 1 μg/ml and epinephrine 2 μg/ml by either gravity flow or by bolus injection through the epidural needle. Changes in maternal heart rate (HR) and blood pressure, signs of intravascular injection, and adverse effects of epidural bupivacaine-sufentanil were recorded after each dose.

Measurements and Main Results: Gravity flow administration (Group 1) was associated with a smaller increase in mean maternal HR (p < 0.001), less hypotension (p < 0.01), sedation (p < 0.01), nausea (p = 0.01), and segmental spread (p < 0.0001) than were corresponding doses given by traditional bolus injection (Group 1) for vaginal or Cesarean deliveries. The incidence of systemic toxicity was zero of 300 (0%) with gravity flow and 4 of 300 (1.3%) by bolus injection, p = 0.12, Fisher's exact test. No patient in either group had an accidental intrathecal injection.

Conclusion: Gravity flow administration of local anesthetic-opioid solution during epidural block for obstetrics was associated with fewer signs of systemic drug absorption and cardiovascular perturbations than was the traditional bolus injection. This study supports the current opinion that slow administration of local anesthetic during epidural black contributes to fewer adverse events.  相似文献   

22.
D. Koh    C. L. Goh    H. T. W. Tan    S. K. Nge  W. K. Wong 《Contact dermatitis》1997,37(1):32-34
This study attempts to demonstrate the existence of allergic contact dermatitis from grass, and to develop a patch test series to screen patients with grass intolerance. 6 common grass species from lawns and military training areas were collected. Solvent extracts of polar. non-polar and volatile fractions were prepared and used for patch testing in 20 control subjects and 46 patients with a history of grass intolerance. The 20 control had negative responses to patch testing. 5 out of 46 patients had positive patch tests to Axonopus compressus (carpet grass). Ischaenmum muticum (sea-shore centipede grass). Imperata evlindrica (lalang). Panicum maximum (Guinea grass) and Pennisetum purpureum (elephant grass). Reactions to the non-polar fraction for all 5 species were noted. This study demonstrates the existence of allergic contact dermatitis from various common species of grass. In our series, this is seen in 11% of those with a history of grass intolerance.  相似文献   
23.
大鼠下丘脑弓状核的形态计量研究   总被引:1,自引:1,他引:0  
为了探讨急性癫痫弓状核形态改变与可复性,我们采用光、电镜技术和形态计量方法对下丘脑弓状核进行了形态定量研究。结果显示:弓状核切面面积为317500±6460um2,神经元胞体和胞核的等效直径分别为12.94±0.34um和8.54±0.43um,暗细胞内线粒体、粗面内质网、高尔基复合体、溶酶体、游离核相体和分泌颗粒的面积分数分别是5.87±1.98%、3.53±0.25%、0.81±0.49%、2.13±0.42%、10.53±0.46%和0.86±0.35%,其面数密度(单位面积为30um2)分别为15.68±1.14um-2、21.29±3.52um-2、10.20±0.42um-2、5.62±067um-2、101.35±7.55um-2和5.22±0.77um-2.本文还对弓状核的形态结构、神经元类型及其功能进行了讨论。  相似文献   
24.
Summary. To investigate the ability of various lung-function tests to demonstrate dilatation of peripheral airways, ten asthmatics inhaled increasing doses of a f2-agonist by two different and controlled techniques. Low inspiratory flow with a long post-inspi-ratory pause favoured peripheral deposition, and a high inspiratory flow with a short post-inspiratory pause favoured central deposition of drug in the airways. Ordinary spirometry, maximum expiratory flow rates after breathing air as well as a helium-oxygen mixture, a single breath N2-test and resistance of the respiratory system were obtained before and after each of five terbutaline doses with both inhalation techniques. By using a double-dummy technique, the study could be performed double blinded. Effects were compared at doses giving equal effects on PEF, assumed to represent equal deposition of bronchodilator and effects on central airways. At such ‘iso A PEF doses’, particularly FVC and the slope of phase III of the N2-test improved more following the slow inhalation technique. It is concluded that changes in those tests reflect dilatation in peripheral airways in asthmatics.,  相似文献   
25.
This is a report on a comparative study of the reactivity of TRUE Test and Finn Chamber patch test techniques. 413 patients attending a contact dermatitis clinic in Singapore were simultaneously patch tested with panels 1 and 2 of the TRUE Test standard series and with corresponding allergens (Hermal, Hamburg) using Finn Chambers. The left/right application of the TRUE Test and Finn Chambers was randomized. The concordance of positive patch test reactions to the 2 test techniques was studied. The number of patient with positive reactions was 38% and 42% for TRUE Test and Finn Chamber techniques, respectively (n.s.). The overall concordance of positive patch test reactions was 64% (209/328). 13% (42/328) of positive reactions appeared on TRUE Test only and 24% (77/328) on Finn Chamber only. When only relevant positive reactions were considered, the concordance rate was 67%; 11.6% of positive reactions appeared on TRUE Test only and 21% on Finn Chamber only. Positive reactions to p-phenylenediamine (PPD) and neomycin were more frequent with the Finn Chamber technique than with TRUE Test, i.e., false negative reactions to PPD and neomycin were more likely to occur with TRUE Test. It appeared that the TRUE Test and Finn Chamber techniques were comparable when used for patch testing. However false negative and false positive patch test reactions can occur when using either technique.  相似文献   
26.
This article reviews the author's experience with a form of interposed abdominal compression cardiopulmonary resuscitation (IAC-CPR) in the United Kingdom. The development of the technique based upon animal resuscitation, including the use of phasic compression (abdominal pumping) for the resuscitation of rats from 30 minutes of cardiac arrest due to hypothermia, is reviewed. A simple technique for clinical use is described. The technique uses a hard-covered book or bean-shaped board applied to the abdomen below the umbilicus and compressed alternately with cardiac massage while respiration is assisted. Anecdotal clinical results suggest that further controlled clinical investigation is warranted.  相似文献   
27.
Body composition measured with isotopic dilution was compared with anthropometric measurements. The study was carried out in 47 subjects from both sexes, 65 to 92 years old. Total body water (TBW), anthropometric measurements, and dynamometry were assessed. TBW was significatively higher in men than women and decreased with age. Dynamometry and fatfree mass were well correlated (r=0.73 in males and r=0.58 in females) and significantly different between sexes. A negative correlation was found for dynamometry with age, being significant for women. Linear regression equations to predict TBW from anthropometric measurements in males and females were obtained: Males: TBW(I)=19.349+0.617 weight(kg) — 0.931 mid-arm circumference(cm)+0.122 dynamometry (kg) Females: TBW(l)=−5.531+0.343 weight(kg)-0.213 triceps skinfold (mm)+ 0.148 dynamometry(kg) + 3.424 wrist diameter (cm). This simple model is proposed for use in epidemiological and field studies where other more sophisticated methods can not be applied.  相似文献   
28.
Objective The objective of this study was to evaluate whether the rigid application of a sterile protocol for shunt placement was applicable on a routine basis and allowed the reduction of shunt infections (SI) in children. Materials and methods Since 2001, a rigid sterile protocol for shunt placement in children using neither antibiotic-impregnated catheters nor laminar airflow was prospectively applied at Erasme Hospital, Brussels, Belgium. For assessing the protocol efficacy before continuation, we preliminarily analyzed the results of the first 100 operated children (43 females, 57 males, 49 aged <12 months; 115 consecutive shunt placement/revision procedures). All procedures were performed by the same senior surgeon, one assistant, one circulating nurse, one anesthesiologist. The sterile protocol was rigidly imposed to these four staff members: uniformed surgical technique; limited implant and skin edge manipulation; minimized human circulation in the room; scheduling surgery as first morning operation; avoiding postoperative cerebrospinal fluid (CSF) leak; double gloving; procedures of less than 30-min duration; systemic antibiotics prophylaxis. We analyzed separately: (1) children carrying an increased risk of SI (n = 38) due to preoperative external ventricular drainage, CSF leak, meningitis, glucocorticoids, chemotherapy; (2) children aged <12 months; (3) procedures for shunt revision. Results Errors in protocol application were recorded in 71/115 procedures. They were mainly done by non-surgical staff, decreased with time and were medically justified in some young children. Surprisingly, no SI occurred (follow-up, 4 to 70 months). One child developed an appendicitis with peritonitis (Streptococcus faecalis) after 6 months. No SI was found. After peritonitis was cured, shunt reinsertion was uneventful. Conclusion These preliminary results suggest that a uniform and drastic sterile surgical technique for shunt placement: (1) can be rigidly applied on a routine basis; (2) can lower the early SI rate below 1%; (3) might have a stronger impact to reduce SI than using antibiotic-impregnated catheters and optimizing the operative environment such as using laminar airflow and reducing the non-surgical staff. This last issue will be evaluated further in the present ongoing protocol.  相似文献   
29.
李凤仙  魏文 《癌症》1994,13(3):206-210
用逐步递增药物浓度和软琼脂细胞克隆技术,药物连续作用14个月后获得氮芥(HN2)抗药性人早幼粒白血病HL60细胞亚系,抗件达5~7倍(HL60/NH26),在无HN2培养液中5倍以上抗性维持10个月以上,抗性细胞亚系的生物学特性除倍增时间稍长和克隆形成率略低外其生长曲线,细胞周期细胞DNA指数,形态学,组织化学和染色体分析均与亲代细胞相似。  相似文献   
30.
Summary Cerebellar nuclear afferents from some caudal brain stem nuclei in the cat were studied by means of retrograde transport after implantation of the wheat germ agglutinin-horseradish peroxidase complex in crystalline form in the cerebellar nuclei. The findings give evidence that projections to the cerebellar nuclei from certain nuclei of the reticular formation proper (e.g., from the gigantocellular reticular nucleus) are very modest, while there appears to be no or extremely few cerebellar nuclear afferents from the paramedian reticular, spinal trigeminal, gracile, cuneate and external cuneate nuclei. Previous tracer studies have given evidence that also the pontine and red nuclei send very few, if any, fibres to the cerebellar nuclei. All these brain stem regions are known to project to the cerebellar cortex. This relative lack of mossy fibre collaterals to the cerebellar nuclei is discussed with references to previous literature on the distribution of cerebellar nuclear afferents, and the problem of how the cerebellar nuclei are facilitated is considered.Abbreviations Br.c. superior cerebellar peduncle (brachium conjunctivum) - Br.p. middle cerebellar peduncle (brachium pontis) - C.r. interior cerebellar peduncle (restiform body) - HRP horseradish peroxidase - L left - N.c. cuneate nucleus - N.c.e. external cuneate nucleus - N.c.t. nucleus of corpus trapezoideum - NIA anterior interposed nucleus - NIP posterior interposed nucleus - NL lateral (dentate) nucleus - N.l.l. nuclei of lateral lemniscus - NM medial (fastigial) nucleus - N.m.X. dorsal motor vagal nucleus - N.mes. mesencephalic trigeminal nucleus - N.r.l. lateral reticular nucleus (nucleus of the lateral funiculus) - N.r.p. paramedian reticular nucleus - N.r.t. reticular tegmental pontine nucleus - N V, VI, VII, XII root fibres of cranial nerves - Ol.s. superior olive - P.h. nucleus praepositus hypoglossi - Py pyramid - R right - R.gc. gigantocellular reticular nucleus - R.l. lateral reticular nucleus of Meessen and Olszewski - R.p.c. caudal pontine reticular nucleus - R.pc. parvicellular reticular nucleus - R.v. ventral reticular nucleus - Tr.sp.V. spinal tract of the trigeminal nerve - T.s. solitary tract surrounded by nucleus of solitary tract - V.m. medial vestibular nucleus - WGA wheat germ agglutinin - WGA-HRP wheat germ agglutinin-horseradish peroxidase conjugate - V, VI, VII, X, XII motor nuclei of cranial nerves  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