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   1530659篇
  免费   94468篇
  国内免费   1826篇
耳鼻咽喉   20972篇
儿科学   48908篇
妇产科学   39582篇
基础医学   232736篇
口腔科学   40337篇
临床医学   137214篇
内科学   284995篇
皮肤病学   34350篇
神经病学   110515篇
特种医学   60004篇
外国民族医学   254篇
外科学   230542篇
综合类   28069篇
现状与发展   3篇
一般理论   360篇
预防医学   108378篇
眼科学   35093篇
药学   121387篇
  8篇
中国医学   3686篇
肿瘤学   89560篇
  2018年   16116篇
  2017年   12371篇
  2016年   14155篇
  2015年   15733篇
  2014年   21308篇
  2013年   31199篇
  2012年   43913篇
  2011年   47114篇
  2010年   27534篇
  2009年   25454篇
  2008年   43451篇
  2007年   47109篇
  2006年   47269篇
  2005年   45040篇
  2004年   43398篇
  2003年   41743篇
  2002年   40262篇
  2001年   78268篇
  2000年   80218篇
  1999年   66523篇
  1998年   16893篇
  1997年   14687篇
  1996年   14694篇
  1995年   13764篇
  1994年   12425篇
  1993年   11932篇
  1992年   49851篇
  1991年   49495篇
  1990年   49121篇
  1989年   47501篇
  1988年   43047篇
  1987年   42082篇
  1986年   39402篇
  1985年   37299篇
  1984年   27200篇
  1983年   23059篇
  1982年   12406篇
  1979年   24830篇
  1978年   16965篇
  1977年   14724篇
  1976年   13617篇
  1975年   15897篇
  1974年   18230篇
  1973年   17630篇
  1972年   16638篇
  1971年   15768篇
  1970年   14580篇
  1969年   13902篇
  1968年   12585篇
  1967年   11286篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
66.
ABSTRACT

Objectives: The present study investigated the relationships of enculturation and depressive symptoms with health risk behavior engagement in Mexican-American college students and examined how these relationships differed by gender. Previous research has noted consistent gender differences in health risk behavior (e.g. alcohol use, substance use, and risky sexual behavior) among Latina/os, and emphasized the role of U.S. acculturation in this difference. Research examining the role of heritage cultural retention (i.e. enculturation), and including the added influence of mental health variables, such as depressive symptoms, is currently lacking. This study sought to address this gap.

Design: A large sample (N?=?677) of Mexican-American college students from four universities (located in New York, California, Florida, and Texas) completed an online questionnaire assessing health risk behaviors and corresponding variables.

Results: We found that males who endorsed more behavioral enculturation and depressive symptoms were more likely to engage in health risk behavior than all others in the sample. Contrary to previous literature, no relationship was found between behavioral enculturation and health risk behavior in females.

Conclusion: The current study found behavioral enculturation to be associated with depressive symptoms, and in turn with health risk behaviors among the males in our sample. Additional research will be needed to identify the mechanism underlying the relationship between enculturation and depressive symptoms as well as between depressive symptoms and risky behavior.  相似文献   
67.
Platelet α-granules release growth factors (GFs) that promote healing and tissue regeneration. Platelet-rich plasma (PRP) is shown to be beneficial in treating alopecia, and however, clinical response can be inconsistent. Due to several fold enrichment of platelets secreting large quantities of GFs following PRP injections, heterogeneity in amounts of GFs secreted by platelets may contribute to inconsistent clinical responses. Herein, we evaluated factors that could potentially contribute to heterogeneous secretion of GFs by platelets. We measured platelet secretion of transforming growth factor beta1 (TGFβ1), platelet-derived growth factor (PDGF-BB), epidermal growth factor (EGF), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF2) in aliquots of de-identified PRP samples from female patients undergoing therapy in the hair disease clinic. Although secretion of GFs by platelets was comparable in PRP samples of patients with non-cicatricial and cicatricial alopecia, a Shapiro-Wilk test for normal distribution indicated significant variability across all patient samples. The amount of GF secreted by platelets was comparable when PRP prepared from two FDA-cleared devices with distinct techniques were compared. We provide evidence of platelets secreting heterogeneous amounts of GFs within each sample as high and low secretion of random factors could be simultaneously detected. These results suggest inherent heterogeneity in secretion of GFs by platelets in patient samples that are not influenced by the device used to prepare PRP. Since some GFs could have antagonistic effects on hair growth, a balance between amounts of growth promoting and inhibiting factors may be crucial in determining clinical response to PRP therapy.  相似文献   
68.
69.
70.
Inbred mouse strains are the most widely used mammalian model organism in biomedical research owing to ease of genetic manipulation and short lifespan; however, each inbred strain possesses a unique repertoire of deleterious homozygous alleles that can make a specific strain more susceptible to a particular disease. In the current study, we report dystrophic cardiac calcinosis (DCC) in C.B‐17 SCID male mice at 10 weeks of age with no significant change in cardiac function. Acquisition of DCC was characterized by myocardial injury, fibrosis, calcification, and necrosis of the tissue. At 10 weeks of age, 38% of the C.B‐17 SCID mice from two different commercial colonies exhibited significant calcinosis on the ventricular epicardium, predominantly on the right ventricle. The frequency of calcinosis was more than 50% for mice obtained from Taconic's Cambridge City colony and 25% for mice obtained from Taconic's German Town colony. Interestingly, the DCC phenotype did not affect cardiac function at 10 weeks of age. No differences in echocardiography or electrocardiography were observed between the calcinotic and non‐calcinotic mice from either colony. Our findings suggest that C.B‐17 SCID mice exhibit DCC as early as 10 weeks of age with no significant impact on cardiac function. This strain of mice should be cautiously considered for the study of cardiac physiology.  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