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   4715篇
  免费   301篇
  国内免费   65篇
耳鼻咽喉   64篇
儿科学   81篇
妇产科学   28篇
基础医学   303篇
口腔科学   134篇
临床医学   563篇
内科学   505篇
皮肤病学   45篇
神经病学   57篇
特种医学   214篇
外科学   291篇
综合类   464篇
一般理论   1篇
预防医学   1825篇
眼科学   69篇
药学   283篇
  1篇
中国医学   67篇
肿瘤学   86篇
  2024年   3篇
  2023年   51篇
  2022年   69篇
  2021年   189篇
  2020年   156篇
  2019年   137篇
  2018年   134篇
  2017年   153篇
  2016年   127篇
  2015年   162篇
  2014年   228篇
  2013年   412篇
  2012年   266篇
  2011年   340篇
  2010年   227篇
  2009年   198篇
  2008年   243篇
  2007年   257篇
  2006年   240篇
  2005年   164篇
  2004年   161篇
  2003年   151篇
  2002年   116篇
  2001年   99篇
  2000年   94篇
  1999年   75篇
  1998年   69篇
  1997年   64篇
  1996年   66篇
  1995年   50篇
  1994年   65篇
  1993年   38篇
  1992年   51篇
  1991年   40篇
  1990年   44篇
  1989年   21篇
  1988年   24篇
  1987年   11篇
  1986年   15篇
  1985年   15篇
  1984年   12篇
  1983年   2篇
  1982年   12篇
  1981年   5篇
  1980年   3篇
  1979年   8篇
  1978年   7篇
  1977年   2篇
  1975年   3篇
  1972年   1篇
排序方式: 共有5081条查询结果,搜索用时 250 毫秒
41.
The purpose of this study was to establish the range of total serum IgE in a healthy population lacking personal and family history of allergy, as well as the influence of genetic factors (family history of allergy), environmental factors (degree of air pollution), age, and sex on the serum IgE levels. Using a commercial enzyme immunoassay (Phadezym IgE Prist) the mean serum level of IgE was determined in 363 non-atopic children from 0 to 12 years of age. The geometric mean of serum IgE increased according to age, indicating a positive correlation between both. Higher mean values of serum IgE were found for children with a family history of allergy, than for children without (27.82 and 14.49 U/ml respectively). The percentage of variation due to age was about 94.5% in children with no family history of allergy. The mean value of serum IgE increased with the degree of air pollution in the living area (15.49 U/ml in non-polluted areas, 20.78 U/ml in very polluted areas). However, the influence of air pollution was smaller than the influence of family history on the mean values of serum IgE. The mean value of serum IgE was not modified by sex.  相似文献   
42.
目的 分析大气污染物与浦东新区居民每日肺癌死亡人数的相关性,为制定针对肺癌病人的保护措施提供依据。方法 采集浦东新区2005年1月1日至2019年12月31日之间的每日大气污染物浓度、气象因素以及居民肺癌死亡资料,利用时间分层-病例交叉设计并结合分布滞后非线性模型,探讨大气污染物短期暴露对浦东新区居民肺癌死亡的影响。结果 大气污染物(PM10, SO2, NO2)浓度与浦东新区居民肺癌死亡风险呈正相关。PM10, SO2, NO2浓度对居民肺癌死亡风险的影响均在累积8 d(Lag 0~7)最强。PM10, SO2, NO2浓度上升10 μg/m3累积8 d(Lag 0~7)居民肺癌死亡风险分别上升1.09%(95%CI:0.35%~1.83%), 3.78%(95%CI:1.98%~5.61%)与2.76%(95%CI:1.10%~4.44%)。女性人群肺癌死亡对PM10与NO2的影响不敏感(P>0.05)。大气污染物对高龄人群与低文化水平人群肺癌死亡效应较强,人群间效应差异不显著。结论 大气污染物短期暴露可以升高浦东新区居民肺癌死亡风险,以累积8 d(Lag 0~7)效应最强。  相似文献   
43.
This study presents the relationships between ambient air pollutants and morbidity and emergency department visits among children and adults performed in Great Casablanca, the most populated and economic region in Morocco. This research was analyzed using conditional Poisson model for the period 2011–2013. In the period of study, the daily average concentrations of SO2, NO2, O3 and PM10 in Casablanca were 209.4 µg/m3, 61 µg/m3, 113.2 µg/m3 and 75.1 µg/m3, respectively. In children less than 5 years old, risk of asthma could be increased until 12% per 10 µg/m3 increase in NO2, PM10, SO2 and O3. In children over 5 years and adults, an increase of 10 µg/m3 air pollutant can cause an increase until 3% and 4% in respiratory consultations and acute respiratory infection, respectively. Similarly, impact on emergency department visits due to respiratory and cardiac illness was established. Our results suggest a not negligible impact on morbidity of outdoor air pollution by NO2, SO2, O3, and PM10.  相似文献   
44.
目的建立甲醇-二硫化碳解吸-气相色谱法测定工作场所空气中1,2-二氯乙烯的方法。方法空气中1,2-二氯乙烯用活性炭管采集,经甲醇-二硫化碳溶剂解吸,DB-FFAP毛细管色谱柱(30 m×0.25 mm,0.25μm)分离,火焰离子化检测器检测,保留时间定性,峰高或峰面积定量。结果顺-1,2-二氯乙烯、反-1,2-二氯乙烯的检出限分别为0.35μg/ml、0.81μg/ml;定量下限分别为1.16μg/ml、2.67μg/ml(相应的最低检出浓度分别为0.23 mg/m3、0.54 mg/m3)。批内相对标准偏差分别为0.32%~0.60%、0.50%~0.79%,批间相对标准偏差分别为0.60%~0.95%、0.78%~0.90%;平均解吸效率分别为97.6%~101%、96.0%~98.0%;在2.5μg/ml~500μg/ml内线性关系良好,相关系数分别为0.999 8、0.999 6。结论本方法灵敏度高、准确度和精密度好,解吸效率高,可用于工作场所空气中1,2-二氯乙烯的检测。  相似文献   
45.
BACKGROUND: The sensitizing potency of formaldehyde and phenol during anatomy dissecting was investigated. The objective was to determine whether exposure induces specific IgE or IgG against formaldehyde-albumin or phenol-albumin. METHODS: In 27 medical students, specific IgE against formaldehyde-albumin by RAST plus ELISA and specific IgE against phenol-albumin by ELISA were assessed. In addition, specific IgG against formaldehyde-albumin was assessed in 23 students. Symptoms before and during dissecting were assessed, and indoor formaldehyde and phenol were measured. RESULTS: Mean indoor formaldehyde was 0.265 +/- 0.07 mg/m3, and mean indoor phenol was 4.65 +/- 2.96 mg/m3. Specific IgE/IgG against formaldehyde-albumin was not found at the beginning. Four students developed specific IgE against formaldehyde-albumin (RAST classes of > or =2.0), and all four also had specific IgE in the ELISA, but IgG against formaldehyde-albumin was not found. Specific IgE against phenol-albumin was not seen. Itch and paresthesia of the hands (P<0.00001), dizziness (P<0.008), burning eyes (P<0.01), headache, sneezing, epistaxis, gingival bleeding, oral or pharyngeal itch, and shortness of breath were experienced. CONCLUSIONS: Formaldehyde exposure during dissecting may induce specific IgE, but not IgG, against formaldehyde-albumin. Sensitization did not correlate with symptoms.  相似文献   
46.
Summary Blood styrene was measured by a gas chromatography-mass spectrometry method in 81 normal people and in 76 workers exposed to styrene. In the normal subjects, styrene was also tested in alveolar and environmental air. Styrene was found in nearly all (95%) blood samples. Average styrene levels in the normal subjects were 221 ng/1 in blood (Cb), 3 ng/1 in alveolar air (Ca) and 6 ng/1 in environmental air (Ci). Styrene levels did not differ significantly between smokers and non-smokers, 95% of values being below 512 ng/1 in Cb, 7 ng/1 in Ca and 15 ng/l in Ci. In workers with an average exposure to styrene of 204 g/l, at the end of the workshift, mean blood styrene concentration was 1211 g/l. In blood samples collected at the end of the Thursday shift, styrene levels were significantly higher (1590 g/1) than those found at the end of the Monday shift (1068 g/l. A similar difference was found in samples taken the morning after exposure (60 and 119 g/l, respectively). Significant correlations between blood and environmental styrene were found both at the end of the shift and the morning after exposure (r=0.61 and 0.41, respectively). In workers occupationally exposed to styrene, 16 h after the end of the workshift, blood styrene (94 g/l) was significantly higher than that found in the normal subjects (0.22 g/l). The half-life of blood styrene was 3.9 h.  相似文献   
47.
目的 研究降低无轨运输方式施工隧道中空气污染的措施。方法 采用燃油添加剂 ,定期对施工机械进行维修和保养 ,减少发动机空档排气 ,将压入式通风口设置于距掌子面 8~ 10m处 ,保持通风管道密闭通畅致使有效送风。结果 隧道中有害气体CO、NOx及黑烟浓度至少降低 4 6 % ,55%和 4 2 %。结论 采取以上措施能明显改善施工环境的污染状况并减轻对施工人员身体健康的危害  相似文献   
48.
我们调查了北京一些高档的空调建筑,包括商业和政府机构办公大楼,测试了主要的室内污染和室内气象参数,如温度、湿度、风速等。测试结果指出,在这些建筑中存在着严重的室内空气质量问题。而且,引起不良室内空气质量的原因不是单一的而是多方面的。因此如何提高室内空气质量,为人们提供健康而舒适的室内环境,是空调设计者的迫切任务。  相似文献   
49.
目的 研究改善空气质量的对策。方法二氧化硫的测定用甲醛一副玫瑰苯胺分光光度法;氮氧.化物的测定用Saltzman法;总悬浮颗粒的测定用重量法;所获数据经数理统计检验。结果SO2、NOx、TSP无显性差异,各功能区与上年均无显性差异。结论1999年环境空气质量与1998年相比无显性差异,改善环境质量,应从调整能源结构入手,同时大力推广汽车空气净化技术,控制汽车、摩托车增长速度,加强植树  相似文献   
50.
The need for continous, noninvasive, and reliable respiratory rate monitoring during recovery from general anesthesia has long been recognized. Alternative principles can be grouped into those detecting the respiratory effort, and those detecting the actual result, i.e. the respiratory gas flow. The second category is of greatest interest for patient monitoring. In this paper, we report the development and initial clinical experience with a new acoustic air-flow sensor. By differential, multipoint detection of the air-flow in the mouth and nose region, the sensor can easily discriminate against different kinds of interference, including motion arterfacts. The sensor is nonexpensive, rugged, simple to apply, and inherently safe. An instrument with continous display of respiratory rate, and an audiovisual apnea alarm has been designed and built.The complete system has been tested on patients during recovery after general anesthesia. In 16 patients, the respiratory rate displayed by the instrument has been correlated against that visually observed. A good correlation was obtained. Minor discrepancies can be explained from the fact that visual observation corresponds to the respiratory effort, whereas the sensor detects the actual air flow. In 12 patients, 24 hour simultaneous recordings were made of respiratory rate with the new sensor, with simultaneous recording of the oxygen saturation and the heart rate with a pulse oximeter. It was found that the new sensor reliabley recorded respiratory depression and apnea. Such events may in some patients be as frequent as one incident per hour. One case of Ondine's curse provided clear evidence that pulse oximetry has a low sensitivity to respiratory disorders.  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