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   174754篇
  免费   34152篇
  国内免费   2493篇
耳鼻咽喉   5425篇
儿科学   6084篇
妇产科学   2944篇
基础医学   7069篇
口腔科学   3961篇
临床医学   28617篇
内科学   52159篇
皮肤病学   7926篇
神经病学   16670篇
特种医学   6864篇
外国民族医学   1篇
外科学   43652篇
综合类   578篇
现状与发展   72篇
一般理论   7篇
预防医学   10048篇
眼科学   3654篇
药学   2844篇
中国医学   287篇
肿瘤学   12537篇
  2024年   522篇
  2023年   5006篇
  2022年   1680篇
  2021年   4086篇
  2020年   6686篇
  2019年   3026篇
  2018年   8356篇
  2017年   8054篇
  2016年   9141篇
  2015年   9246篇
  2014年   16592篇
  2013年   16931篇
  2012年   7505篇
  2011年   7735篇
  2010年   11502篇
  2009年   15078篇
  2008年   7239篇
  2007年   5371篇
  2006年   7714篇
  2005年   4755篇
  2004年   3895篇
  2003年   2774篇
  2002年   2767篇
  2001年   4313篇
  2000年   3582篇
  1999年   3661篇
  1998年   3796篇
  1997年   3561篇
  1996年   3462篇
  1995年   3305篇
  1994年   2022篇
  1993年   1628篇
  1992年   1581篇
  1991年   1602篇
  1990年   1244篇
  1989年   1356篇
  1988年   1184篇
  1987年   977篇
  1986年   1000篇
  1985年   831篇
  1984年   644篇
  1983年   597篇
  1982年   551篇
  1981年   441篇
  1980年   391篇
  1979年   389篇
  1978年   402篇
  1977年   441篇
  1975年   331篇
  1972年   335篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
991.
992.
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   
993.
Palmar advancement flap with V-Y closure for thumb tip injuries   总被引:1,自引:0,他引:1  
The palmar advancement flap with V-Y closure was used in two patients with thumb tip injuries. This technique allows more distal advancement of the flap than does a conventional palmar advancement flap and does not require skin graft coverage.  相似文献   
994.
We examined records of sedations provided by the paediatric anaesthesiology staff for 455 children (ages 1 mo-17 yr) undergoing MRI or CT scans at our institution over a twelve-month period with regard to the monitoring of adverse events: excessive sedation, agitation, vomiting, hypoxaemia, and major airway compromise. One hundred-and-thirty-one patients (29%) received chloral hydrate; 324 patients (71%) received propofol. All patients were monitored with continuous noninvasive pulse oximetry and received supplemental oxygen via nasal cannulae. Of the patients who received chloral hydrate, 64 (49%) were over one year of age; of the patients who received propofol, 318 (98%) were one year of age or older. In the chloral hydrate group, 23 patients (19%) were deemed excessively sedated and four patients (3%) were agitated; no patients in the propofol group experienced any of the adverse outcomes reviewed. Furthermore, no patients in either group had significant airway compromise and none was admitted to the hospital as a result of the sedation.  相似文献   
995.
Urban and Rural Differences in Health Insurance and Access to Care   总被引:3,自引:0,他引:3  
This study considers differences in access to health care and insurance characteristics between residents of urban and rural areas. Data were collected from a telephone survey of 10,310 randomly selected households in Minnesota. Sub-samples of 400 group-insured, individually insured, intermittently insured, and uninsured people, were asked about access to health care. Those with group or individual insurance were also asked about the costs and characteristics of their insurance policies.
Rural areas had a higher proportion of uninsured and individually insured respondents than urban areas. Among those who purchased insurance through an employer, rural residents had fewer covered benefits than urban residents (5.1 vs 5.7, P < 0.01) and were more likely to have a deductible (80% versus 40%, P < 0.01). In spite of this, rural uninsured residents were more likely to have a regular source of care than urban residents (69% versus 51%, P < 0.01), and were less likely to have delayed care when they thought it was necessary (21% versus 32%, P<0.01). These differences were confirmed by multivariate analysis.
Rural residents with group insurance have higher out-of-pocket costs and fewer benefits. Uninsured rural residents may have better access to health care than their urban counterparts. Attempts to expand access to health care need to consider how the current structure of employment-based insurance creates inequities for individuals in rural areas as well as the burdens this structure may place on rural providers.  相似文献   
996.
Reversal of diastolic cerebral blood flow in infants without brain death   总被引:1,自引:0,他引:1  
The reversal of diastolic cerebral blood flow has been regarded as a characteristic waveform of brain death and a useful confirming sign. We report 2 patients who had diastolic flow reversal but survived. One, a 1-month-old boy with status epilepticus, had reversal of diastolic cerebral blood flow detected by Doppler ultrasound soon after admission. Reversal disappeared after medical management for increased intracranial pressure and seizure control. He recovered without sequelae. The other, a 6-month-old girl with choroid plexus papilloma, had reversal of diastolic flow during abrupt clinical deterioration. Emergent surgical removal of the tumor was performed and she survived with hemiparesis and psychomotor retardation. Our patients demonstrated that even in the presence of diastolic reversal of cerebral blood flow, prompt and effective treatment can avoid a fatal outcome.  相似文献   
997.
998.
999.
Background: Atelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver.

Methods: A consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2 O. FI sub O2 was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (V with dot A/Q with dot) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique.

Results: In group 1 (FIO2 = 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (V with dot A/Q with dot < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < V with dot A/Q with dot < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2 = 1.0). Comparing the values before and 40 min after recruitment, all parameters of V with dot A/Q with dot were unchanged. In both groups, Crs increased from 57.1/55.0 ml *symbol* cmH2 O sup -1 (group 1/group 2) before to 70.1/67.4 ml *symbol* cmH2 O sup -1 after the recruitment maneuver. Crs showed as low decrease thereafter (40 min after recruitment: 61.4/60.0 ml *symbol* cmH2 O sup -1), with no difference between the two groups.  相似文献   

1000.
Objective. The objective of this study was to develop an interface to allow special physiologic signals (e.g., in a research setting) to be displayed on the invasive pressure channel of conventional clinical monitors. The interface accepts single-ended high-level signals for display using the pressure channel of patient monitors, which use strain-gauge transducers employing direct current (DC) excitation.Methods. By studying the electronic circuitry common to most clinical invasive pressure measurement systems (Wheatstone bridge, differential input instrumentation amplifier) it was possible to develop an interface to convert high-level single-ended signals into the low-level differential signal needed for input to an invasive pressure channel.Results and Conclusions. The device is useful when it is desired to display signals from special transducers on regular patient monitors. Schematic diagrams and sample results are provided.  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