全文获取类型
收费全文 | 26018篇 |
免费 | 3192篇 |
国内免费 | 647篇 |
专业分类
耳鼻咽喉 | 106篇 |
儿科学 | 468篇 |
妇产科学 | 1251篇 |
基础医学 | 1436篇 |
口腔科学 | 206篇 |
临床医学 | 7957篇 |
内科学 | 3910篇 |
皮肤病学 | 302篇 |
神经病学 | 963篇 |
特种医学 | 1549篇 |
外国民族医学 | 6篇 |
外科学 | 2961篇 |
综合类 | 4136篇 |
现状与发展 | 3篇 |
预防医学 | 1485篇 |
眼科学 | 458篇 |
药学 | 1121篇 |
53篇 | |
中国医学 | 268篇 |
肿瘤学 | 1218篇 |
出版年
2024年 | 115篇 |
2023年 | 599篇 |
2022年 | 1060篇 |
2021年 | 1317篇 |
2020年 | 1577篇 |
2019年 | 1335篇 |
2018年 | 1276篇 |
2017年 | 1312篇 |
2016年 | 1282篇 |
2015年 | 1281篇 |
2014年 | 2155篇 |
2013年 | 1984篇 |
2012年 | 1465篇 |
2011年 | 1575篇 |
2010年 | 1228篇 |
2009年 | 1129篇 |
2008年 | 1181篇 |
2007年 | 1196篇 |
2006年 | 973篇 |
2005年 | 794篇 |
2004年 | 677篇 |
2003年 | 630篇 |
2002年 | 498篇 |
2001年 | 424篇 |
2000年 | 340篇 |
1999年 | 332篇 |
1998年 | 269篇 |
1997年 | 265篇 |
1996年 | 230篇 |
1995年 | 187篇 |
1994年 | 171篇 |
1993年 | 142篇 |
1992年 | 115篇 |
1991年 | 106篇 |
1990年 | 85篇 |
1989年 | 69篇 |
1988年 | 62篇 |
1987年 | 50篇 |
1986年 | 59篇 |
1985年 | 88篇 |
1984年 | 62篇 |
1983年 | 20篇 |
1982年 | 45篇 |
1981年 | 31篇 |
1980年 | 23篇 |
1979年 | 21篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Localization of an nonpalpable colonic lesion at the time of colectomy usually requires intraoperative colonoscopy. The use
of ultrasound to locate the lesion has not been described. A soft bowel clamp is placed above the expected location of the
lesion and a catheter placed in the anus. Saline is then instilled into the colon and rectum. The lesion is located by ultrasound
scan of the fluid filled colon with the probe placed on the serosal surface. Refinement of the technique was performed on
resected colonic specimens. An in vivo trial was then performed with rapid and accurate localization of the lesion for resection.
Intraoperative ultrasound of the colon can accurately localize nonpalpable colonic lesions and is an alternative to currently
available techniques of localization.
Received: 10 December 1997/Accepted: 11 March 1998 相似文献
52.
Troisi E Silvestrini M Matteis M Monaldo BC Vernieri F Caltagirone C 《Journal of neurology》1999,246(12):1172-1176
This study assessed the use of transcranial Doppler ultrasound in detecting selective changes in cerebral blood flow velocity
during emotional processes. The role of the respective hemispheres in emotional processing is controversial. Cerebral control
of emotional processing has previously been investigated by analysis of patients with unilateral brain damage, experiments
with selective stimulation of only one hemisphere, and more recently by imaging techniques measuring local cerebral blood
flow. We investigated mean flow velocity continuously and simultaneously in both the right and left middle cerebral arteries
(MCAs) in 16 healthy right-handed young subjects at rest and during the performance of three tasks: task 1: 15 slides with
nonemotional content; task 2: 15 slides with negative emotional content; task 3: 15 slides with nonemotional content with
different content from that in task 1. The three tasks produced significantly different effects on the right and left hemispheres.
During the two nonemotional tasks the increase in mean flow velocity over basal values was similar in the two MCAs (task 1:
left MCA = 3.27 ± 1.9%; right MCA = 3.63 ± 2.1%; task 3: left MCA = 2.42 ± 0.7%; right MCA = 2.56 ± 1.3%); the negative emotional
task was accompanied by a significantly higher increase in the right (11.31 ± 1.6%) than in the left MCA (4.72 ± 3.7%; analysis
of variance two-way interaction: side of recording x task, F = 43.6, P < 0.001). These results show the possibility of obtaining specific functional information from bilateral transcranial Doppler
ultrasound and suggest the involvement of the right hemisphere in emotional processing.
Received: 4 March 1999 Received in revised form: 29 June 1999 Accepted: 5 August 1999 相似文献
53.
David T. Wong George A. Volgyesi Bruno Bissonnette 《Journal canadien d'anesthésie》1992,39(6):596-599
The Doppler ultrasound (DUS) technique is a widely accepted non-invasive technique to estimate systolic blood pressure (SBP) accurately in paediatric patients. The DUS has a number of limitations. A new pulse monitor, Mr Pulse (MP), operating on the principle of a finger plethysmograph, was developed to offer an alternative technique to estimate SBP. From 104 paired SBP measurements taken in 16 paediatric patients undergoing general anaesthesia, SBP determined by the MP technique correlated closely with that by the standard DUS technique (r2 = 0.98). Analysis of degree of agreement performed indicated that there was good agreement between SBP obtained by the MP and the DUS techniques. The mean +/- standard deviation of differences in paired SBP values between the two measurement techniques was 0.55 +/- 3.59 mmHg. Mr Pulse is as accurate as the DUS technique in estimating SBP and has the advantage of less critical sensor positioning as it is not subject to electrical interference. It has no electrical hazard. 相似文献
54.
目的 探讨不同强度下低频超声波介导透皮给药对人体皮肤组织的影响。方法 以 2 4例健康青年志愿者的双上臂作为试验区域 ,每个试验者两上臂同时涂抹 1geutecticmixtureoflocalanesthetics,10min后分别采用 0 .5、1W·cm-2 的能量进行低频超声 (2 0kHz )介导 ,介导时间 10min。每 5min测量两组镇痛起始时间 ,试验结束后观察皮肤组织的变化。结果 能量为 1W·cm-2 的低频超声组平均镇痛起始时间为 32 .75± 3.73min ,0 .5W·cm-2 组为 37.6 5± 3.2 4min。低频超声可使角质层间质增宽和疏松 ,0 .5W·cm-2 组未见组织学病理损害 ,1W·cm-2 组可见点状红疹 ,类似二度烫伤。结论 能量高可更快促进药物透过皮肤 ,但高能量可引起皮肤组织病理性损害 ,0 .5W·cm-2 组能量是比较安全的低频给药方式。 相似文献
55.
Anne Summers 《Paediatrics & child health》2003,8(1):25-29
In Ontario, approximately 140,000 women deliver newborn infants each year. Of these women, 60,000 to 70,000 have multiple marker screening, 10,000 undergo amniocentesis or chorion villus sampling and virtually all have at least one prenatal ultrasound. Multiple marker screening is not used in every province and territory; however, amniocentesis and prenatal ultrasound are used throughout Canada. Most paediatric patients will have been exposed to some form of prenatal diagnosis. If an abnormality is found prenatally, parents may have concerns to discuss with the paediatrician after the child is born. Likewise, if a child with a problem is born following a normal pregnancy, the parents will want to know why the problem was missed prenatally. Paediatricians should be aware of prenatal tests that have been performed to understand better their patients and their families. 相似文献
56.
Leigh D Mosel Evelyn Kat Frank Voyvodic 《Journal of Medical Imaging and Radiation Oncology》2004,48(2):267-271
Accessory ossicles of the foot are commonly mistaken for fractures. The accessory navicular is one of the most common accessory ossicles of the foot. There is a higher incidence in women and the finding might be bilateral in 50?90%. This entity is usually asymptomatic, although populations with medial foot pain have a higher prevalence. Three types of accessory navicular bone have been described. The type II accessory navicular is the most commonly symptomatic variant with localized chronic or acute on chronic medial foot pain and tenderness with associated inflammation of overlying soft tissues. Plain radiographic identification of the accessory navicular is insufficient to attribute symptomatology. Ultrasound allows for comparison with the asymptomatic side and localization of pain. Bone scintigraphy has a high sensitivity but positive findings lack specificity. Magnetic resonance imaging is of high diagnostic value for demonstrating both bone marrow and soft tissue oedema. 相似文献
57.
Andreas Lee M.D. Michael Sator M.D. Alfred Kratochwil Professor Josef Deutinger Professor Elisabeth Vytiska-Binsdorfer PhD Gerhard Bernaschek Professor 《Fertility and sterility》1997,68(5):831-835
Objective: At present, only limited data are available on endometrial volume during the menstrual cycle. Most of these studies deal with animal models and use magnetic resonance imaging for volume measuring. The application of three-dimensional ultrasound in endometrial volume estimation is the subject of this study.Setting: Patients visiting the outpatient unit of the division of endocrinology and reproductive medicine of a university hospital.Patient(s): Twenty patients with a history of a normal menstrual cycle were selected.Intervention(s): Ultrasound examinations were performed during a single menstrual cycle in addition to routine laboratory tests.Main Outcome Measure(s): Uterus-endometrial volume ratio.Result(s): Data from 18 patients could be evaluated. In 81 examinations the endometrium volume could be determined. Mean endometrial volume measured by three-dimensional ultrasound was 1.23 cm'. Mean uterus volume was 48.93 cm3. The change of the uterus-endometrial volume ratio showed a good correlation with the day of menstrual cycle. Quadratic regression analysis of volume and cycle length was R2 = 0.432.Conclusion(s): Three-dimensional ultrasound allows assessment of volume data of the female internal genitalia. In this study changes of the endometrial volume in menstrual cycles were measured. Additional studies are required to give information on the clinical impact of this new technique of endometrial volume estimation. 相似文献
58.
F Buzi A Pilotta D Dordoni A Lombardi S Zaglio P Adlard 《Acta paediatrica (Oslo, Norway : 1992)》1998,87(11):1138-1145
This prospective study sought to evaluate the role of pelvic ultrasonography in differentiating between various types of pubertal precocity. A control group of 117 normal girls (aged 1.1-15.6) was studied and compared with 87 girls with premature sexual maturation (aged 1.1-9.2y). Of these patients 19 had central precocious puberty (CPP), 48 had isolated premature thelarche (IPT) and 20 had premature adrenarche (IPA) Pelvic ultrasound variables evaluated were: (i) uterus: longitudinal diameter (uterine length), cross-sectional area (CSA) and fundo-cervical ratio; and (ii) ovaries: volume and morphology. Ovarian morphology was subdivided in 6 different appearances: solid, microcystic, paucicystic, multicystic, macrocystic, and major isolated cyst. In normal control girls, uterine length and CSA increased with age, although no cut-off values could be defined between different age ranges, and they were correlated with breast stage; fundo-cervical ratio was stable through childhood and increased after age 9. Ovarian volume was significantly greater in pubertal girls with breast stage 2 than in those with only pubic and/or axillary hair. There was a clear predominance of solid ovarian appearances in the age range 2-7, with the multicystic appearance being seen only after age 7, a minority being macrocystic. After age 10 all the different patterns were observed, and after age 13 the frequency of a macrocystic pattern increased. Significantly more mature ovarian appearances were observed in subjects with breast development compared with those without, independently of the presence of pubic hair. Patients with IPT had no significant differences in pelvic ultrasound measurements when compared with age-matched controls. All the different morphological ovarian appearances were observed in IPT, in contrast to age-matched controls, where only the less mature patterns (solid, micro- and paucicystic) were seen. Patients with CPP had significantly more mature patterns of ovarian morphology compared with age-matched controls, but did not differ from pubertal pre-menarcheal controls. Those patients with IPA differed from age-matched controls only in having significantly greater uterine length and CSA. Comparison of the pelvic ultrasound parameters between patient groups (IPT, CPP, IPA) and age-matched controls revealed significantly higher values in CPP for uterine length, uterine CSA and ovarian volume. Ovarian volume was also greater in IPT than in IPA. Ovarian morphology was significantly different in patients (IPT, CPP, IPA) compared with age-matched controls, but none of the ovarian morphological appearances was exclusive to a single condition. In conclusion: (i) pelvic ultrasound parameters increase progressively from birth to maturity, but no clear cut-off values can be established between age ranges; (ii) pelvic ultrasound variables reach adult values during puberty, with differences in the timing that may reflect geographical variations; (iii) the multicystic ovarian appearance occurs just before the onset of puberty; (iv) pelvic ultrasonography cannot always differentiate clearly between different disturbances of puberty and therefore cannot supersede other observations and investigations in the evaluation of pubertal disorders; and (v) in this study we propose a more detailed pelvic ultrasound terminology that can avoid apparent confusion in defining ovarian ultrasound appearance. 相似文献
59.
Randomized trial examining cerebral haemodynamics following artificial or animal surfactant 总被引:2,自引:0,他引:2
To determine the effects of animal and artificial surfactants on cerebral haemodynamics, 20 premature babies receiving mechanical ventilation were randomized to receive Curosurf or Exosurf surfactant. Anterior cerebral artery blood flow velocity (CABFV) was measured using Doppler ultrasound before and up to 2 h after treatment. Following animal surfactant there was a rapid reduction in CABFV (median -36%, range -43% to +8%, p < 0:01), whereas artificial surfactant resulted in a slower rise which was less marked (median +20%, range -7% to +62%, p < 0:05). There were no significant changes in blood pressure. Two hours after administration, the oxygenation index (OI) improved significantly only in babies receiving animal surfactant. In this group there was a significant association between the change in CABFV at 1 min and the change in OI at 2 h ( r = 0:66, p < 0:05). Animal surfactant produces rapid improvements in ventilation which are associated with marked alterations in cerebral haemodynamics. 相似文献
60.
H. Iro B. A. Völklein F. Waldfahrer T. Schneider R. E. Riedlinger J. Zenk 《European archives of oto-rhino-laryngology》1998,255(8):420-426
The cytotoxic and anti-proliferative effects of high-energy pulsed ultrasound (HEPUS) on human squamous cell carcinoma cells
cloned from the hypopharynx (FaDu) and benign connective tissue cells (fibroblasts) were investigated in vitro. Sonication
was carried out using an experimental piezoelectric, self-focusing burst-signal transducer. To increase the induction of cavitation,
the transducer used was specifically designed to produce multiple oscillations with a high negative pressure amplitude. In
both cell lines tested, the application of 100, 800 and 2000 pulses resulted in a high reduction of vital cells. After 2000
pulses, 4.0 ± 1.1% of the fibroblasts but only 2.0 ± 0.4% of the FaDu cells survived HEPUS exposure. A postexposure inhibiting
effect of HEPUS for 10 days on the proliferation of surviving cells was noted for the FaDu cells exposed to 2000 pulses, but
not as much for the fibroblasts. These findings support the hypothesis that human squamous cell carcinoma cells of the hypopharynx
might be more sensitive to HEPUS than fibroblasts and that total tumor cell ablation might be possible in vitro given a sufficient
number of HEPUS pulses.
Received: 18 November 1997 / Accepted: 21 April 1998 相似文献