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   166206篇
  免费   10626篇
  国内免费   1261篇
耳鼻咽喉   2383篇
儿科学   3070篇
妇产科学   3783篇
基础医学   24883篇
口腔科学   3435篇
临床医学   15553篇
内科学   31565篇
皮肤病学   4560篇
神经病学   12403篇
特种医学   8482篇
外科学   22627篇
综合类   2187篇
现状与发展   5篇
一般理论   81篇
预防医学   9853篇
眼科学   4563篇
药学   14016篇
中国医学   1651篇
肿瘤学   12993篇
  2023年   1022篇
  2022年   2867篇
  2021年   4997篇
  2020年   2578篇
  2019年   3734篇
  2018年   4552篇
  2017年   3374篇
  2016年   4370篇
  2015年   5895篇
  2014年   7213篇
  2013年   8707篇
  2012年   13124篇
  2011年   12733篇
  2010年   7555篇
  2009年   6341篇
  2008年   9549篇
  2007年   9392篇
  2006年   8587篇
  2005年   8188篇
  2004年   7267篇
  2003年   6338篇
  2002年   5497篇
  2001年   4418篇
  2000年   4060篇
  1999年   3293篇
  1998年   1330篇
  1997年   1016篇
  1996年   963篇
  1995年   874篇
  1994年   759篇
  1993年   653篇
  1992年   1582篇
  1991年   1578篇
  1990年   1364篇
  1989年   1245篇
  1988年   1161篇
  1987年   1036篇
  1986年   1011篇
  1985年   884篇
  1984年   650篇
  1983年   569篇
  1982年   400篇
  1981年   378篇
  1980年   338篇
  1979年   521篇
  1978年   406篇
  1977年   389篇
  1976年   343篇
  1974年   359篇
  1973年   327篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
We investigate the controlled release of lidocaine hydrochloride from the doped silica-based xerogels. In the xerogel preparation, tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), and propyltriethoxysilane (PTES) are used as precursors, and a nonionic surfactant Igepal CO 720 is used as a dopant. The experimental results suggest that the release of lidocaine hydrochloride can be easily controlled by partially substituting TEOS with the organosilanes, and/or by adding the dopant. Adding the organosilane precursors lowers the release of both the drug and the surfactant in the order of TEOS, MTES/TEOS, and PTES/TEOS xerogels. The release from the PTES/TEOS xerogels is much lower than that from the other xerogels. The release of lidocaine hydrochloride is obviously suppressed by the addition of Igepal CO 720, while the release of Igepal CO 720 is slightly promoted by the addition of the drug. The overall release process is found to be diffusion-controlled, and the release behaviors can be well explained by considering the effects of the textual properties of the xerogels and the interactions among the drug, the surfactant, and the xerogel matrices.  相似文献   
52.
Behavioral state-specific changes in human hippocampal theta activity   总被引:1,自引:0,他引:1  
Although there has been extensive examination of the behavioral and physiologic correlates of hippocampal theta activity in animals, the human literature consists of a single case study. We investigated the differential effects of four behavioral states on human hippocampal theta activity in 16 epilepsy surgery patients. Behavioral conditions included resting eyes closed (RC), resting eyes open (RO), eyes open with auditory word activation (AW), and eyes open with visuospatial activation (VS). Hippocampal theta activity decreased during both RO and VS compared to both RC and AW. There were reciprocal changes in delta activity. Comparisons of RO to VS and of RC to AW were nonsignificant. The results demonstrate state-specific changes in human hippocampal theta and are consistent with the animal literature that relates hippocampal theta to sensorimotor integration and forebrain volitional mechanisms.  相似文献   
53.
Originally described by Rosen in 1983, syringomatous nipple adenoma (SAN) is a tumor of disputed histogenesis, which can be problematic both diagnostically and therapeutically. 1 It is a benign primary tumor of breast epithelium with histology similar to that of the syringoma. In the current case, we describe a 40-year-old female with this lesion occurring within a supernumerary breast. This case represents, to our knowledge, the first such reported case, and represents a significant finding as its presence could lend some confusion as to whether or not this represents a benign primary process of breast or a potentially infiltrative tumor of the skin.  相似文献   
54.
55.
56.
Background/aims: The objective and quantitative assessment of the skin is important in medical and cosmeceutical research. Assessment of color is an important element for analyzing the surface of the skin, which is usually determined subjectively by a doctor or using color analysis devices. These devices, however, cannot provide correct color information because color is construed from the mean value of the observation region, and analysis of color distribution is impossible. The purpose of this paper is to develop an objective analysis method to permit skin color measurement of each pixel unit of an image and analyze the distribution of skin surface color. Methods: The Skin Color Distribution Analyzer (SCDA) is an analysis method newly developed at the Research Institute for Skin Image at Korea University. The SCDA system presented in this paper performed a novel form of quantitative and objective analysis of skin color distribution using each pixel color model parameter found in image wavelength information. In this paper, distribution analysis was conducted on normal skin and skin lesions and skin affected by artificially induced irritant contact dermatitis and pigmented nevous. The method selected a grade using a color model parameter. Twenty healthy Korean males participated in this study. A comparative study of the eight anatomical areas was performed, including the exposure and non‐exposure parts and the medial aspect and the lateral aspect of the forearm. A reliability test for the SCDA system was also conducted with a spectrometer (SPEC) using the color analysis method. Results: Each skin lesion was precisely segmented by grade and each parameter hada different statistical significance for results of analysis of distribution in pigmented nevous and the artificially induced irritant contact dermatitis. Parameters L*, b*, a*, and EI showed salient traits. Showed resemble measured result in the SCDA system and the SPEC of normal skin. The exposed site, in comparison with the non‐exposed site, showed a notable difference in the L* parameter and a significant statistical difference in the x and z parameters, except b*. The comparison of the medial and lateral aspects of the forearm showed a notable difference in the L* parameter and a significant statistical difference in the parameters except y and b*. In the reliability test result using the SCDA system and the SPEC, the SCDA system was highly reliabile in terms of the CV value in all color model parameters. Conclusions: The color distribution analysis method using the SCDA system has revealed an aspect that the existent method of medical research has not shown, and is considered to be more reliable than other methods. This method can provide better study findings because it can be applied to other fields in addition to the medical science field and the ripple effect is thought to be bigger in other science field too.  相似文献   
57.
58.
59.
60.
The purpose of this study was to examine the levels of anxiety of mothers with children in pediatric intensive care units with different types of visitation policies, both structured and individualized Forty subjects were obtained from two children's hospitals A comparative research design was used Data showed that mothers who experienced individualized visitation had significantly lower anxiety scores (p < 005) than mothers who experienced structured visitation Findings also revealed that mothers viewed their child's illness as less severe when individualized visitation was permitted as opposed to structured visitation.  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