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   12687篇
  免费   1086篇
  国内免费   62篇
耳鼻咽喉   155篇
儿科学   320篇
妇产科学   314篇
基础医学   1585篇
口腔科学   282篇
临床医学   1522篇
内科学   2465篇
皮肤病学   150篇
神经病学   960篇
特种医学   930篇
外国民族医学   2篇
外科学   1568篇
综合类   381篇
一般理论   8篇
预防医学   1382篇
眼科学   170篇
药学   817篇
中国医学   8篇
肿瘤学   816篇
  2021年   165篇
  2020年   120篇
  2019年   192篇
  2018年   212篇
  2017年   159篇
  2016年   151篇
  2015年   181篇
  2014年   309篇
  2013年   423篇
  2012年   562篇
  2011年   603篇
  2010年   318篇
  2009年   289篇
  2008年   467篇
  2007年   581篇
  2006年   530篇
  2005年   536篇
  2004年   467篇
  2003年   457篇
  2002年   452篇
  2001年   424篇
  2000年   400篇
  1999年   336篇
  1998年   169篇
  1997年   135篇
  1996年   143篇
  1995年   165篇
  1994年   145篇
  1993年   127篇
  1992年   319篇
  1991年   273篇
  1990年   273篇
  1989年   308篇
  1988年   241篇
  1987年   231篇
  1986年   225篇
  1985年   232篇
  1984年   178篇
  1983年   139篇
  1982年   116篇
  1981年   101篇
  1979年   198篇
  1978年   151篇
  1977年   110篇
  1975年   97篇
  1974年   133篇
  1973年   108篇
  1972年   94篇
  1971年   95篇
  1970年   99篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.

Background  

While much research has been conducted on medication safety, few of these studies have addressed primary care, despite the high volume of prescribing and dispensing of medicines that occurs in this setting. Those studies that have examined primary care dispensing emphasised the need to understand the role of sociotechnical factors (that is, the interactions between people, tasks, equipment and organisational structures) in promoting or preventing medication incidents. The aim of this study was to identify sociotechnical factors that community pharmacy staff encounter in practice, and suggest how these factors might impact on medication safety.  相似文献   
992.
The presenting characteristics of 1423 consecutive admissions with proximal femoral fractures were prospectively studied, to determine any differences that may exist between patients, dependent on the radiological site of the fracture. Patients with intracapsular fractures were of a lower average age, more mobile, less likely to use walking aids or live in residential accommodation, they also had a considerably shorter length of hospital stay than for those patients with extracapsular fractures. Comparison against previous series shows that the average age of hip fracture patients and the proportion of trochanteric fractures is increasing.  相似文献   
993.
Baby bottle tooth decay (BBTD) is a term applied to a specific form of rampant decay associated with inappropriate bottle or breast feeding of infants and young children. Although the prevalence of BBTD has been studied in individual ethnic groups, comparison studies are rare. Head Start children have frequently served as study subjects for assessing the prevalence of BBTD. The purpose of this study was to compare BBTD and caries prevalence among Head Start children who are members of four ethnic groups in five southwestern States. Age, residence, and fluoridation status were also compared for the total sample and ethnic categories. The sampling process was a stratified random site selection; it was used to obtain data on 1,230 children. This number constituted 3 percent of the children enrolled in Head Start in Public Health Service Region VI (Arkansas, Louisiana, New Mexico, Oklahoma, and Texas) where the study was conducted. The criterion for determining the presence of BBTD was based on the number of carious deciduous maxillary incisors observed. The severity of the condition was reported as two of four and three of four of the target teeth affected. Thus, two levels of severity are reported. BBTD was prevalent in approximately 24 percent and 15 percent of the total sample, depending on the severity criterion used. Native American children had a significantly higher (P less than 0.05) prevalence than Hispanic, white, and black subjects. Rural children had significantly higher (P less than 0.05) prevalence of BBTD than nonrural children for all ethnic groups except whites.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
994.
The etiology of retroperitoneal fibrosis is unknown in 70% of the cases. The aim of our study was to examine the possible association between occupational asbestos exposure and retroperitoneal fibrosis; only two cases have been reported in the literature. We gathered all the cases of retroperitoneal fibrosis diagnosed in the Tampere University Hospital between 1987 and 1995. We examined their hospital records to evaluate the possible etiology of the disease. We also sent a structured questionnaire to all living patients (10/13) to obtain information on their asbestos exposure. The chest radiographs of the patients were re-read to evaluate possible changes resulting from asbestos exposure. We found 13 cases of idiopathic retroperitoneal fibrosis. Seven patients (all male) had been exposed to asbestos in the past. The chest radiographs of the four most-exposed patients showed characteristic asbestos-related abnormalities, including bilateral pleural plaques, round atelectasis and small irregular lung opacities. In our study, we found that asbestos exposure and asbestos-induced changes in the lung and pleura were common among male retroperitoneal fibrosis patients. We suggest that occupational exposure to asbestos may be an important etiological factor for retroperitoneal fibrosis. Am. J. Ind. Med. 33:418–421, 1998. © 1998 Wiley-Liss, Inc.  相似文献   
995.
The objective of this study was to examine the correlates of excessive maternal weight gain among adolescent mothers in the United States. Data from the Centers for Disease Control & Prevention 2000 natality file were analyzed to examine weight gain among adolescents (≤19 years) compared with their older counterparts (≥20 years). Using the Institute of Medicine guidelines, we defined excessive weight gain as more than 40 pounds. Our study population was restricted to singleton births, delivered after 36 weeks of gestation, who did not live in California. Maternal weight gain distributions were tabulated by maternal age and other maternal characteristics. Demographic characteristics potentially associated with maternal weight gain were compared for adolescents and older mothers. We further evaluated the role of parity and maternal race on the relationship between excessive weight gain and maternal age. Odds ratios and 95% confidence intervals were estimated using logistic regression. Over 27% of adolescent mothers gained excessive weight during pregnancy, although approximately 18% of their older counterparts gained more than 40 pounds. The association between young maternal age and weight gain was stronger for primiparous women than multiparous women and stronger among non-Hispanic white and non-Hispanic black mothers than Hispanic mothers. Adolescents were more likely to gain excessive weight than their older counterparts in nearly all demographic categories, regardless of parity or race. Adolescents are at high risk of gaining an excessive amount of weight during pregnancy and should be monitored during pregnancy by dietetics professionals.  相似文献   
996.
This investigation examined the potential of inoculation to protect young adults' attitudes from pressures to engage in risky behaviors (unprotected sex and binge drinking) as well as inoculation's efficacy in conferring umbrella protection (cross-protection) over related, but experimentally untreated, attitudes. A three-phase experiment was conducted involving 120 participants. The results revealed that inoculation can protect the attitudes of young adults from counterattitudinal pressures to engage in unprotected sex (treated issue) and binge drinking (untreated issue). Practical applications of these findings are explored, including the use of inoculation when designing health messages and more thorough assessments of health campaigns designed to discourage risky behaviors.  相似文献   
997.
998.
First responders to illicit drug labs may not always have SCBA protection available. Air-purifying respirators using organic vapor cartridges with P-100 filters may not be sufficient. It would be better to use a NIOSH-approved CBRN respirator with its required multi-purpose cartridge system, which includes a P-100 filter. This would remove all the primary drug lab contaminants—organic vapors, acid gases, ammonia, phosphine, iodine, and airborne meth particulates. To assure the proper selection and use of a respirator, it is recommended that the contaminants present be identified and quantified and the OSHA 29 CFR 1910.134 respirator protection program requirements followed.  相似文献   
999.
A survey of the contribution to external dose from gamma rays originating from intertidal sediments in the vicinity of the British Nuclear Group Sellafield site showed that the major anthropogenic contributions were due to (137)Cs and (60)Co. At some sites, traces of other anthropogenic radionuclides were detected, namely (106)Ru, (125)Sb, and (154)Eu. The proportions of fine grained material (<63 microm) were used to improve model predictions of dose contribution due to external exposure to gamma rays, using the CUMBRIA77/DOSE77 model. Model dose predictions were compared to those directly measured in the field. Using the new proportions of fine grained material (1-17.5%) in conjunction with field gamma-ray spectra, model predictions were improved considerably for most sites. Exceptions were at Drigg Barn Scar and Whitehaven Coal Sands sites, which had their own unique characteristics. The highest (60)Co activity concentrations in this study were detected at Drigg Barn Scar. These relatively high activity concentrations of (60)Co were due to the presence of (60)Co in mussels and barnacles, hence upsetting the fine sediment relationships used in previous dose calculations. Whitehaven Coal Sands was unusual in that it contained higher levels of radionuclides than would be expected in sandy sediment. The mineralogy of these sediments was the controlling factor on (137)Cs binding, rather than the proportion of fine grained material. By adjusting the effective fine grained sediment proportions for calculations involving (60)Co and (137)Cs at Drigg Barn Scar and Whitehaven Coal Sands respectively, the CUMBRIA77/DOSE77 model predictions could be improved upon significantly for these sites. This work highlights the influence of particle size and sediment composition on external dose rate calculations, as well as the potential for external dose contributions from biota.  相似文献   
1000.
The extent to which maternal folate and vitamin B12 modulate infant birth weight is unclear. The present study investigated mothers in early gestation (mean 11.5 (sd 5.8) weeks) and neonates, at delivery. Erythrocyte (RBC) folate (mothers: n 683; neonates: n 614) and vitamin B12 (mothers: n 534; neonates: n 614) were measured. Data on smoking habits were available for 44 % of pregnancies (n 443). The relationship between vitamin levels and birth weight standardized for gender and gestational age was investigated, using linear regression and adjusting for possible confounding variables (maternal age, parity). Results are presented as standardized regression coefficients (b). Increasing maternal age was associated with elevated RBC folate (b 0.11 (95 % CI 0.08, 0.15), P<0.001; n 674) and smoking was associated with a decrease in maternal RBC folate (b -1.38 (95 % CI -1.92, -0.86), P=0.001; n 319). Neonatal RBC folate was predicted by maternal RBC folate (b 0.08 (95 % CI 0.04, 0.11), P=0.001; n 315) and maternal vitamin B12 (b 0.08 (95 % CI 0.01, 0.16), P=0.02; n 252). Smoking influenced maternal vitamin B12 status (b -0.88 (95 % CI -1.49, -0.27), P=0.005; n 231). Using univariate regression, smoking significantly influenced infant birth weight (b -2.15 (95 % CI -3.24, -1.04), P<0.001; n 437). However, the effect of smoking on birth weight was statistically non-significant when considered in a multivariate regression model, leaving maternal RBC folate as the only significant predictor of birth weight (b 0.25 (95 % CI 0.08, 0.42), P=0.005; n 145). These findings suggest that maternal folate status is an important determinant of infant birth weight. The combined effects of smoking and reduced RBC status on birth weight require further investigation.  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