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   3125篇
  免费   232篇
  国内免费   22篇
耳鼻咽喉   10篇
儿科学   209篇
妇产科学   68篇
基础医学   401篇
口腔科学   55篇
临床医学   327篇
内科学   611篇
皮肤病学   24篇
神经病学   240篇
特种医学   499篇
外科学   292篇
综合类   58篇
预防医学   294篇
眼科学   28篇
药学   149篇
中国医学   4篇
肿瘤学   110篇
  2021年   21篇
  2020年   21篇
  2019年   21篇
  2018年   35篇
  2017年   27篇
  2016年   34篇
  2015年   44篇
  2014年   54篇
  2013年   105篇
  2012年   74篇
  2011年   87篇
  2010年   104篇
  2009年   91篇
  2008年   83篇
  2007年   82篇
  2006年   74篇
  2005年   79篇
  2004年   69篇
  2003年   70篇
  2002年   68篇
  2001年   64篇
  2000年   78篇
  1999年   79篇
  1998年   148篇
  1997年   133篇
  1996年   142篇
  1995年   106篇
  1994年   85篇
  1993年   90篇
  1992年   51篇
  1991年   69篇
  1990年   53篇
  1989年   99篇
  1988年   80篇
  1987年   78篇
  1986年   82篇
  1985年   80篇
  1984年   47篇
  1983年   54篇
  1982年   58篇
  1981年   32篇
  1980年   52篇
  1979年   38篇
  1978年   31篇
  1977年   29篇
  1976年   31篇
  1975年   30篇
  1974年   17篇
  1973年   24篇
  1972年   18篇
排序方式: 共有3379条查询结果,搜索用时 15 毫秒
131.
Approximately 8% of all non-Hodgkin lymphomas are extranodal marginal zone B cell lymphomas of mucosa-associated lymphoid tissue (MALT), also known as MALT lymphomas. These arise at a wide range of different extranodal sites, with most cases affecting the stomach, the lung, the ocular adnexa and the thyroid. The small intestine is involved in a lower percentage of cases. Lymphoma growth in the early stages is associated with long-lasting chronic inflammation provoked by bacterial infections (e.g., Helicobacter pylori or Chlamydia psittaci infections) or autoimmune conditions (e.g., Sjögren’s syndrome or Hashimoto thyroiditis). While these inflammatory processes trigger lymphoma cell proliferation and/or survival, they also shape the microenvironment. Thus, activated immune cells are actively recruited to the lymphoma, resulting in either direct lymphoma cell stimulation via surface receptor interactions and/or indirect lymphoma cell stimulation via secretion of soluble factors like cytokines. In addition, chronic inflammatory conditions cause the acquisition of genetic alterations resulting in autonomous lymphoma cell growth. Recently, novel agents targeting the microenvironment have been developed and clinically tested in MALT lymphomas as well as other lymphoid malignancies. In this review, we aim to describe the composition of the microenvironment of MALT lymphoma, the interaction of activated immune cells with lymphoma cells and novel therapeutic approaches in MALT lymphomas using immunomodulatory and/or microenvironment-targeting agents.  相似文献   
132.
133.
流式细胞分析技术(flow cytometry,FCM),又称流式细胞术,是一种在功能水平上对单细胞或其他生物粒子进行定量分析和分选的技术,具有广泛的科研应用价值.采用理论与实践并举,结合讨论的教学方式,在教师队伍开设针对性的培训课程,对深刻理解并在科研工作中有效利用该技术具有及其重要意义.同时以教学促科研,以科研促技...  相似文献   
134.
Biocompatibility of materials strongly depends on their surface properties. Therefore, surface derivatization in a controllable manner provides means for achieving interfaces essential for a broad range of chemical, biological, and medical applications. Bioactive interfaces, while manifesting the activity for which they are designed, should suppress all nonspecific interaction between the supporting substrates and the surrounding media. This article describes a procedure for chemical derivatization of glass and silicon surfaces with polyethylene glycol (PEG) layers covalently functionalized with proteins. While the proteins introduce the functionality to the surfaces, the PEGs provide resistance against nonspecific interactions. For formation of aldehyde-functionalized surfaces, we coated the substrates with acetals (i.e., protected aldehydes). To avoid deterioration of the surfaces, we did not use strong mineral acids for the deprotection of the aldehydes. Instead, we used a relatively weak Lewis acid for conversion of the acetals into aldehydes. Introduction of α,ω-bifunctional polymers into the PEG layers, bound to the aldehydes, allowed us to covalently attach green fluorescent protein and bovine carbonic anhydrase to the surfaces. Spectroscopic studies indicated that the surface-bound proteins preserve their functionalities. The surface concentrations of the proteins, however, did not manifest linear proportionality to the molar fractions of the bifunctional PEGs used for the coatings. This finding suggests that surface-loading ratios cannot be directly predicted from the compositions of the solutions of competing reagents used for chemical derivatization.  相似文献   
135.
136.
137.
PURPOSE/METHOD: We present a case of a patient who developed recurrent epithelial herpes simplex keratitis after starting treatment with latanoprost. Her ophthalmic history was only remarkable for a past episode of herpetic keratitis 21 years previously. RESULTS/CONCLUSIONS: Episodes of herpetic keratitis were under remission only when latanoprost was discontinued. No recurrences of herpes simplex keratitis have been observed since then. Latanoprost usage might be associated with recurrent episodes of herpes simplex keratitis in patients with previous history of ocular herpes simplex virus infection.  相似文献   
138.
139.
OBJECTIVE: This study was designed to determine whether a community sample of obese mothers with young children used different feeding styles compared with a matched sample of normal-weight mothers. Four aspects of feeding style were assessed: emotional feeding, instrumental feeding (using food as a reward), prompting/encouragement to eat, and control over eating. RESEARCH METHODS AND PROCEDURES: Participants were from 214 families with same-sex twins; 100 families in which both parents were overweight or obese and 114 in which both parents were normal weight or lean. RESULTS: We found that obese mothers were no more likely than normal-weight mothers to offer food to deal with emotional distress, use food as a form of reward, or encourage the child to eat more than was wanted. The obese and normal-weight mothers did differ on "control"; obese mothers reported significantly less control over their children's intake, and this was seen for both first-born and second-born twins. Twin analyses showed that these differences were not in response to children's genetic propensities, because monozygotic correlations were no greater than dizygotic correlations for maternal feeding style. DISCUSSION: These results suggest that the stereotype of the obese mother, who uses food in nonnutritive ways so that her child also becomes obese, is more likely to be myth than fact. However, the results raise the possibility that lack of control of food intake might contribute to the emergence of differences in weight.  相似文献   
140.
With the elderly becoming an ever-larger proportion of the American population, their dietary well-being is of increasing concern. In particular, lower-income elderly may face special challenges in maintaining a healthful diet. This group makes up a sizeable proportion of the elderly population; we estimate that almost 1 in 5 (19%) of the elderly have household incomes at or below 130% of the federal poverty level, the income level that generally qualifies a household to participate in the federal Food Stamp Program. Here we examine the dietary intakes and related behaviors, as well as the food security status, of lower- and higher-income elderly and review major US government food and nutrition assistance programs that can be of benefit to the elderly, particularly those of low income. Our subjects are individuals 60 years of age and over, living in community (noninstitutionalized) settings. Data on dietary intakes and behaviors were obtained from the US Department of Agriculture's Continuing Survey of Food Intakes by Individuals (CSFII), 1994-96. Food security data were obtained from the 1999 Current Population Survey (CPS), conducted by the US Census Bureau. For both the CSFII and the CPS, sampling weights were used to generate nationally representative estimates. We found that lower-income elderly consume significantly fewer calories than higher-income elderly, fewer servings of major Food Guide Pyramid food groups, and most nutrients. Approximately 6% of elderly households report some degree of food insecurity. Although food and nutrition assistance programs can benefit elderly individuals, many do not participate. Many lower-income elderly also face physiological and social obstacles to obtaining a healthful diet. How best to meet these varied needs is a challenge for nutrition educators, researchers, and policy makers.  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