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   20327篇
  免费   1320篇
  国内免费   70篇
耳鼻咽喉   233篇
儿科学   733篇
妇产科学   580篇
基础医学   2338篇
口腔科学   249篇
临床医学   3511篇
内科学   3473篇
皮肤病学   203篇
神经病学   1949篇
特种医学   311篇
外科学   1654篇
综合类   199篇
一般理论   85篇
预防医学   3107篇
眼科学   709篇
药学   1023篇
中国医学   11篇
肿瘤学   1349篇
  2023年   81篇
  2022年   133篇
  2021年   293篇
  2020年   209篇
  2019年   354篇
  2018年   404篇
  2017年   313篇
  2016年   370篇
  2015年   448篇
  2014年   587篇
  2013年   1021篇
  2012年   1386篇
  2011年   1460篇
  2010年   807篇
  2009年   689篇
  2008年   1309篇
  2007年   1517篇
  2006年   1479篇
  2005年   1471篇
  2004年   1418篇
  2003年   1314篇
  2002年   1272篇
  2001年   176篇
  2000年   125篇
  1999年   196篇
  1998年   272篇
  1997年   220篇
  1996年   189篇
  1995年   163篇
  1994年   177篇
  1993年   146篇
  1992年   99篇
  1991年   112篇
  1990年   96篇
  1989年   83篇
  1988年   77篇
  1987年   81篇
  1986年   80篇
  1985年   79篇
  1984年   100篇
  1983年   101篇
  1982年   114篇
  1981年   124篇
  1980年   108篇
  1979年   67篇
  1978年   62篇
  1977年   57篇
  1976年   47篇
  1975年   46篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Granulysin: A Novel Host Defense Molecule   总被引:5,自引:0,他引:5  
Granulysin is a novel cationic molecule present in the granules of cytotoxic T lymphocytes and natural killer cells. Cytotoxic T lymphocytes have long been associated with graft destruction in transplant rejection. Recent studies implicate granulysin in cell-mediated cytotoxicity, chemoattraction, immune activation and as a potential diagnostic biomarker for transplant rejection.  相似文献   
52.
BACKGROUND: Research has sought to understand how environmental factors influence adolescent physical activity, yet little is known about where and with whom adolescents are physically active. PURPOSE: This study used electronic ecological momentary assessment (e.EMA) to map the social and physical contexts of exercise and walking across adolescence. Differences in physical activity contexts by gender, grade in school, day of the week, and season were examined. METHODS: Twice a year between 9th and 12th grade, 502 adolescents (51% female) of mixed ethnicity (55% White) participated in 4-day e.EMA intervals (Thursday-Sunday) where their primary activity (e.g., exercise, TV, homework), social company (e.g., friends, family, class), and physical location (e.g., home, school, outdoors) were assessed every 30 (+/-10) min during waking hours. RESULTS: Overall, greater proportions of exercise and walking were reported with friends, outdoors, and at school. However, boys were more likely to report exercising and walking in outdoor locations than girls. Exercising with classmates, family, and at school decreased across high school. Walking with family, friends, and outdoors also decreased. On weekdays compared to weekends, students reported a greater proportion of their exercise and walking at school. Students were more likely to report exercising and walking outdoors in the fall and the spring than in the winter. CONCLUSION: e.EMA showed that the social and physical contexts of adolescent exercise and walking vary as a function of gender, grade in school, day of the week, and season. Understanding the contexts of physical activity during the high school years can be helpful in designing interventions during adolescence.  相似文献   
53.
54.
55.
Background: The outcome of breast cancer is usuallydetermined by multiple factors. Serum tumor necrosis factoralpha concentration has been found to be increasedin the circulation of patients with malignancy. Thisstudy was designed with the aim to investigateany correlation between the serum tumor necrosis factoralpha and the clinicopathological fetures and furthermore evaluatethe prognostic significance of serum tumor necrosis factoralpha concentration in breast cancer. Methods: Forty consecutivepatients with invasive breast cancer undergoing modified radicalmastectomy were prospectively included and evaluated. Venous bloodsamples were collected before the surgery. Sera wereobtained by centrifugation, and stored at – 70°C until assayed. The control group consisted 30healthy, age-matched subjects. Serum concentrations of tumor necrosisfactor alpha were measured by the quantitative sandwichenzyme immunoassay technique. The data on tumor size,age, estrogen receptor status, lymph node status andTNM staging were reviewed and recorded.Results: The mean value of serum tumor necrosis factor alphain patients with invasive breast cancer was 1.47± 0.58 pg/ml and that of the controlgroup was 0.98 ± 0.37 pg/ml, and thedifference was significant (P < 0.01). With univariableanalysis, patients with maximum tumor size of 5cm or larger (P=0.03), more advancedTNM staging (P < 0.01); and more advancedlymph node status (P < 0.01) were shownto have significantly higher serum concentrations of tumornecrosis factor alpha. However, with multivariable analysis, TNMstaging appeared as the only independent factor (P< 0.01) predicting the significant, higher serum concentrationsof tumor necrosis factor alpha. Conclusion: Preoperative evaluationof serum tumor necrosis factor alpha concentrations maybe a valuable parameter for reflecting the severityof staging for invasive breast cancer.  相似文献   
56.
PURPOSE: To examine whether compliance with underage sales laws by licensed retail establishments is related to underage use of commercial and social alcohol sources, perceived ease of obtaining alcohol, and alcohol use. METHODS: In 2005, alcohol purchase surveys were conducted at 403 off-premise licensed retail establishments in 43 Oregon school districts. A survey also was administered to 3,332 11th graders in the districts. Multi-level logistic regression analyses were used to examine relationships between the school district-level alcohol sales rate and students' use of commercial and social alcohol sources, perceived ease of obtaining alcohol, past-30-day alcohol use, and heavy drinking. RESULTS: The school district-level alcohol sales rate was positively related to students' use of commercial alcohol sources and perceived alcohol availability, but was not directly associated with use of social alcohol sources and drinking behaviors. Additional analyses indicated stronger associations between drinking behaviors and use of social alcohol sources relative to other predictors. These analyses also provided support for an indirect association between the school district-level alcohol sales rate and alcohol use behaviors. CONCLUSIONS: Compliance with underage alcohol sales laws by licensed retail establishments may affect underage alcohol use indirectly, through its effect on underage use of commercial alcohol sources and perceived ease of obtaining alcohol. However, use of social alcohol sources is more strongly related to underage drinking than use of commercial alcohol sources and perceived ease of obtaining alcohol.  相似文献   
57.
Absence of predictable phenotypic expression in proximal 15q duplications   总被引:5,自引:0,他引:5  
We describe ten individuals with an insertional duplication 15q12----q13. Phenotypic analysis of these individuals and 15 previously reported cases of proximal 15q duplications fails to show any consistent clinical manifestations. It appears that a duplication of this region is phenotypically silent.  相似文献   
58.
59.
60.
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