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   20681篇
  免费   1374篇
  国内免费   73篇
耳鼻咽喉   250篇
儿科学   774篇
妇产科学   584篇
基础医学   2379篇
口腔科学   252篇
临床医学   3526篇
内科学   3603篇
皮肤病学   211篇
神经病学   1964篇
特种医学   316篇
外科学   1660篇
综合类   213篇
一般理论   85篇
预防医学   3172篇
眼科学   713篇
药学   1042篇
中国医学   11篇
肿瘤学   1373篇
  2023年   76篇
  2022年   119篇
  2021年   298篇
  2020年   216篇
  2019年   360篇
  2018年   409篇
  2017年   322篇
  2016年   373篇
  2015年   449篇
  2014年   599篇
  2013年   1030篇
  2012年   1419篇
  2011年   1488篇
  2010年   820篇
  2009年   705篇
  2008年   1327篇
  2007年   1538篇
  2006年   1494篇
  2005年   1494篇
  2004年   1447篇
  2003年   1327篇
  2002年   1289篇
  2001年   197篇
  2000年   139篇
  1999年   200篇
  1998年   281篇
  1997年   225篇
  1996年   192篇
  1995年   167篇
  1994年   182篇
  1993年   150篇
  1992年   97篇
  1991年   121篇
  1990年   94篇
  1989年   83篇
  1988年   79篇
  1987年   79篇
  1986年   80篇
  1985年   81篇
  1984年   100篇
  1983年   101篇
  1982年   121篇
  1981年   125篇
  1980年   111篇
  1979年   67篇
  1978年   63篇
  1977年   62篇
  1976年   48篇
  1975年   51篇
  1973年   44篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
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   
83.
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   
84.
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   
85.
86.
87.
88.
89.
90.
Syringolides are water-soluble, low-molecular-weight elicitors that trigger defense responses in soybean cultivars carrying the Rpg4 disease-resistance gene but not in rpg4 cultivars. 125I-syringolide 1 previously was shown to bind to a soluble protein(s) in extracts from soybean leaves. A 34-kDa protein that accounted for 125I-syringolide 1 binding activity was isolated with a syringolide affinity-gel column. Partial sequences of internal peptides of the 34-kDa protein were identical to P34, a previously described soybean seed allergen. In soybean seeds, P34 is processed from a 46-kDa precursor protein and was shown to have homology with thiol proteases. P34 is a moderately abundant protein in soybean seeds and cotyledons but its level in leaves is low. cDNAs encoding 46-, 34-, and 32-kDa forms of the soybean protein were cloned into the baculovirus vector, pVL1392, and expressed in insect cells. The resulting 32- and 34-kDa proteins, but not the 46-kDa protein, exhibited ligand-specific 125I-syringolide binding activity. These results suggest that P34 may be the receptor that mediates syringolide signaling.  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