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   13934篇
  免费   1243篇
  国内免费   506篇
耳鼻咽喉   58篇
儿科学   75篇
妇产科学   54篇
基础医学   866篇
口腔科学   951篇
临床医学   1098篇
内科学   854篇
皮肤病学   42篇
神经病学   446篇
特种医学   491篇
外科学   826篇
综合类   1981篇
一般理论   3篇
预防医学   2081篇
眼科学   93篇
药学   3717篇
  19篇
中国医学   1837篇
肿瘤学   191篇
  2024年   35篇
  2023年   271篇
  2022年   452篇
  2021年   635篇
  2020年   536篇
  2019年   530篇
  2018年   529篇
  2017年   535篇
  2016年   550篇
  2015年   564篇
  2014年   935篇
  2013年   1461篇
  2012年   957篇
  2011年   998篇
  2010年   719篇
  2009年   728篇
  2008年   815篇
  2007年   718篇
  2006年   613篇
  2005年   535篇
  2004年   376篇
  2003年   305篇
  2002年   282篇
  2001年   259篇
  2000年   213篇
  1999年   154篇
  1998年   113篇
  1997年   125篇
  1996年   93篇
  1995年   64篇
  1994年   77篇
  1993年   75篇
  1992年   64篇
  1991年   44篇
  1990年   37篇
  1989年   36篇
  1988年   40篇
  1987年   34篇
  1986年   26篇
  1985年   29篇
  1984年   21篇
  1983年   12篇
  1982年   12篇
  1981年   14篇
  1980年   19篇
  1979年   6篇
  1978年   5篇
  1977年   7篇
  1976年   6篇
  1975年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
目的:筛选制备阿昔洛韦-乙交酯-丙交酯共聚物毫微粒(ACV-PLGA-NP)的优化工艺。方法:单因素试验初选制备ACV-PLGA-NP的pH值范围、聚乙烯醇(Polyvinyl alcohol,PVA)浓度范围、PLGA分子量、药物及丙酮浓度范围。按均匀设计表设计实验,进行结果预测及验证。结果:优化工艺与PLGA分子量及丙酮浓度无关,pH值为1.5,PVA浓度为50mg/ml,ACV浓度为0.8m  相似文献   
113.
Several requirements of psychotherapeutic intervention (PI) research are presented. Some major problems are discussed. First, confidence in experimental results may be diminished by interference of possible confounders. A large number of these exist, both physical, perhaps more easily measurable, and psychological or psychosocial. Second, the value and limitations of randomization are presented, with special reference to small N. Validity and reliability are addressed, with emphasis on things that may dilute the strength of both of these measures. Natural remedies are proposed. Internal consistency and reliability are compared and cautions are given regarding their use and possible invalid substitution of consistency for reliability. Comparison of different PIs is commented on, with some relevant examples. Finally, a matter of special interest is discussed: the inconsistency between Spiegel's control survival curve and that produced from local population normative data.Presented at the Symposium Psychotherapeutic Interventions in Cancer Patients, Flims, Switzerland, 12–14 January 1995  相似文献   
114.
115.
Malaria vaccines     
Significant progress has been made in the development of the malaria vaccine during the last 20 years. Ninety percent of the 300–500 million clinical cases of malaria per year worldwide occur in Africa. Thus, research must be directed toward the 1 million African children under 5 years of age who die every year of malaria. An asexual blood-stage vaccine, capable of reducing severe and complicated malaria and malaria-related mortality, is therefore an important public health tool in these countries. Although knowledge of the parasite's biology is incomplete, research has allowed insight into some of the mechanisms that the parasite uses to evade host immunity. This is the basis for adopting an antigenic cocktail approach toward obtaining a synthetic or recombinant subunit vaccine such as the synthetic Colombian Malaria vaccine SPf 66. During the development of Spf66, field trials under both low and high malaria endemicity areas in Latin America and Africa have been carried out. The results from these studies showed a protective efficacy ranging between 38.8 and 60.2% againstPlasmodium falciparum malaria. Given the characteristics of the normal immune response to malaria (relatively short-lived and not completely effective), it is understandable that the main goal is to try to increase the host's natural immunity. The best candidates for designing a malaria vaccine are the proteins required for parasite survival, those with low mutation rates and conserved epitopes. Because these proteins play an important role in multiple or alternative steps during the invasion process, they should be the targets against which a protective immune response should be elicited. The interaction between the malaria parasite and its host is complex. It is therefore crucial to define new ways of improving the immune response—such as directly modifying the chemical structure of epitopes or using new adjuvants or DNA immunization techniques—to produce novel vaccines against this disease.  相似文献   
116.
提出了使用Excel 7.0 for Windows95简便和快速优化换热网络的方法。首先由Monte Carlo法确定全局最优点的近似位置,然后由“Solver”求得精确解。全部优化过程由VBA语言编写。此法可用于解决许多工程优化问题。  相似文献   
117.
Summary In a double-blind, placebo-controlled, incomplete cross-over study the bronchodilator, cardiovascular, respiratory and metabolic effects of 3 different oral doses of clenbuterol were studied in 12 patients suffering from partly reversible airways obstruction due to chronic bronchitis. The ventilatory response to oral clenbuterol or placebo was assessed by measurement of specific airway resistance (sRaw) to detect changes in central airways, and of flow at 85% of vital capacity ( 85% VC) to detect change in peripheral airways. Clenbuterol 20, 30 and 40 µg produced a significant decrease in sRaw between 15 and 480 min after administration. Its effect on the large airways was not related to the dose. Clenbuterol 30 and 40 µg caused a significant increase in 85% VC between 60 and 480 min after administration. After 20 µg a significant improvement in 85% VC was found between 120 and 240 min. The over-all effect of 30 µg on the small airways was significantly more pronounced than that of 20 µg and was more sustained than that of 40 µg 120 min after administration. No significant changes in heart rate, ECG or blood pressure were noted. Decreases in PaO2 and O2-saturation after clenbuterol were not related to dose. Slight falls in PaO2 and O2-saturation were also observed after placebo. These observations are briefly discussed. There was negligible lipid mobilization after either the placebo or bronchodilator. A slight but insignificant rise in blood glucose was observed after both 30 and 40 µg of clenbuterol.  相似文献   
118.
119.
用线性隶属函数、二元相对比较级等确定特征因素的隶属度,构造了不同机械传动类型的模糊子集,取其与待识别模糊子集向量空问的距离均数为贴近度。根据择近原则选择确定机械传动类型。  相似文献   
120.
虎杖中白藜芦醇苷提取分离工艺研究   总被引:8,自引:0,他引:8  
目的:考察虎杖中白藜芦醇苷的最佳提取分离工艺。方法:采用正交设计实验优选提取分离条件,双波长薄层扫描测定含量。结果:醇提工艺的最优条件为:95%乙醇l5倍量,回流提取3次,2h/次;水提工艺的最优条件为:水10倍量,回流提取3次、2h/次,两工艺的关键步骤为乙醇浓度和回流时间、结论:该实验确定的最佳提取工艺稳定性好又简便易行。  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