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   26759篇
  免费   2274篇
  国内免费   50篇
耳鼻咽喉   313篇
儿科学   800篇
妇产科学   799篇
基础医学   3576篇
口腔科学   551篇
临床医学   4015篇
内科学   4756篇
皮肤病学   356篇
神经病学   2278篇
特种医学   705篇
外国民族医学   1篇
外科学   3266篇
综合类   431篇
一般理论   36篇
预防医学   3177篇
眼科学   456篇
药学   1740篇
中国医学   26篇
肿瘤学   1801篇
  2022年   178篇
  2021年   384篇
  2020年   257篇
  2019年   466篇
  2018年   541篇
  2017年   385篇
  2016年   438篇
  2015年   501篇
  2014年   682篇
  2013年   1114篇
  2012年   1578篇
  2011年   1662篇
  2010年   936篇
  2009年   839篇
  2008年   1603篇
  2007年   1645篇
  2006年   1583篇
  2005年   1566篇
  2004年   1542篇
  2003年   1467篇
  2002年   1431篇
  2001年   477篇
  2000年   455篇
  1999年   479篇
  1998年   365篇
  1997年   294篇
  1996年   241篇
  1995年   221篇
  1994年   191篇
  1993年   208篇
  1992年   310篇
  1991年   299篇
  1990年   322篇
  1989年   280篇
  1988年   261篇
  1987年   217篇
  1986年   269篇
  1985年   222篇
  1984年   202篇
  1983年   211篇
  1982年   183篇
  1981年   161篇
  1980年   179篇
  1979年   184篇
  1978年   170篇
  1977年   157篇
  1976年   130篇
  1975年   151篇
  1974年   162篇
  1973年   157篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
BACKGROUND: The purpose of this paper is to use demographic and clinical data from a large diverse group of outpatients diagnosed with non-psychotic major depression to investigate the validity of the DSM-IV concept of melancholic depression. METHODS: Baseline clinical and demographic data were collected on 1500 outpatients (1456 of whom melancholia could be determined) with non-psychotic major depressive disorder (MDD) participating in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Depressive symptom severity was assessed by clinical telephone interview using the 17-item Hamilton Rating Scale for Depression (HRS-D17) and the 30-item Inventory of Depressive Symptomatology (IDS-C30). The types and degrees of concurrent psychiatric symptoms were measured using a self report, the Psychiatric Diagnostic Screening Questionnaire (PDSQ), by recording the number of items relevant to each diagnostic category endorsed by study participants. RESULTS: Adjusting for severity of depression (as measured by the total HRS-D17 scores), no differences were found in the rate of melancholic depression by race, marital status, education, employment status, family history of depression, primary care versus specialty care, monthly income, and degree of psychiatric and medical co-morbidity. Melancholic depression was significantly more likely in men than women. Melancholic depression after adjustment for severity was associated with a slightly younger age at study entry, as well as with greater illness severity, and slightly shorter duration of current episode. Hispanic ethnicity was associated with lower melancholic depression rates at the .06 level of significance. CONCLUSIONS: Among outpatients with MDD, melancholic features were less likely in Hispanic patients, but more likely in slightly younger patients and in men. Melancholic features were also related to a slightly shorter current episode. These findings are consistent with the notion that external socio-demographic factors do not play an important role in the pathophysiology of melancholic depression.  相似文献   
102.
103.
BACKGROUND: Multicolored Asian lady beetles (Harmonia axyridis) have been used as a biological control agent against crop-destroying aphids in the United States. Outside their natural habitat, H. axyridis seeks refuge in homes during fall and winter, leading to patient complaints and symptoms of rhinitis, wheezing, and urticaria on exposure to the beetles. OBJECTIVE: To gain a better understanding of the character and spectrum of allergic disease provoked by exposure to home-infesting lady beetles. METHODS: Eight patients with allergic symptoms suspected of being caused by H. axyridis and consistent with an IgE-mediated process were identified and interviewed. A whole-body extract from H. axyridis was prepared. Western blots using the patients' serum identified specific IgE antibodies in the extract. Through a novel technique, immunohistochemical analysis using beetle sections overlayed with patient serum was performed. A random survey of allergists from across the United States was also performed to evaluate experience with cases of lady beetle allergy. RESULTS: Western blots revealed IgE binding to 5 proteins with molecular weights of approximately 8.6, 21, 28, 31, and 75 kDa. Specific IgE bound to proteins localized in the beetle's mouth and leg areas. The allergist survey revealed positive responses in North Central, Mid-Atlantic and New England states. CONCLUSION: In 8 patients with allergic symptoms on exposure to high levels of lady beetles, specific IgE bound to proteins from H. axyridis. There was also an increased frequency of suspected cases of lady beetle allergy in endemic areas.  相似文献   
104.
105.
Background: Magnetic resonance neurography (MRN) is an imaging method by which nerves can be selectively highlighted. Using commercial software, the authors explored a variety of approaches to develop a three-dimensional volume-rendered MRN image of the entire brachial plexus and used it to evaluate the accuracy of infraclavicular block approaches.

Methods: With institutional review board approval, MRN of the brachial plexus was performed in 10 volunteer subjects. MRN imaging was performed on a GE 1.5-tesla magnetic resonance scanner (General Electric Healthcare Technologies, Waukesha, WI) using a phased array torso coil. Coronal STIR and T1 oblique sagittal sequences of the brachial plexus were obtained. Multiple software programs were explored for enhanced display and manipulation of the composite magnetic resonance images. The authors developed a frontal slab composite approach that allows single-frame reconstruction of a three-dimensional volume-rendered image of the entire brachial plexus. Automatic segmentation was supplemented by manual segmentation in nearly all cases. For each of three infraclavicular approaches (posteriorly directed needle below midclavicle, infracoracoid, or caudomedial to coracoid), the targeting error was measured as the distance from the MRN plexus midpoint to the approach-targeted site.

Results: Composite frontal slabs (coronal views), which are single-frame three-dimensional volume renderings from image-enhanced two-dimensional frontal view projections of the underlying coronal slices, were created. The targeting errors (mean +/- SD) for the approaches-midclavicle, infracoracoid, caudomedial to coracoid-were 0.43 +/- 0.67, 0.99 +/- 1.22, and 0.65 +/- 1.14 cm, respectively.  相似文献   

106.
107.
108.
109.
110.
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