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   26779篇
  免费   1790篇
  国内免费   116篇
耳鼻咽喉   333篇
儿科学   561篇
妇产科学   501篇
基础医学   3911篇
口腔科学   396篇
临床医学   2472篇
内科学   6219篇
皮肤病学   472篇
神经病学   2910篇
特种医学   999篇
外国民族医学   3篇
外科学   4471篇
综合类   147篇
一般理论   6篇
预防医学   1394篇
眼科学   422篇
药学   1909篇
中国医学   95篇
肿瘤学   1464篇
  2023年   100篇
  2022年   194篇
  2021年   428篇
  2020年   260篇
  2019年   479篇
  2018年   564篇
  2017年   435篇
  2016年   486篇
  2015年   625篇
  2014年   809篇
  2013年   1095篇
  2012年   1670篇
  2011年   1763篇
  2010年   1118篇
  2009年   980篇
  2008年   1651篇
  2007年   1739篇
  2006年   1631篇
  2005年   1716篇
  2004年   1633篇
  2003年   1631篇
  2002年   1553篇
  2001年   439篇
  2000年   371篇
  1999年   430篇
  1998年   397篇
  1997年   343篇
  1996年   280篇
  1995年   294篇
  1994年   234篇
  1993年   242篇
  1992年   273篇
  1991年   238篇
  1990年   198篇
  1989年   214篇
  1988年   174篇
  1987年   189篇
  1986年   190篇
  1985年   144篇
  1984年   149篇
  1983年   143篇
  1982年   130篇
  1981年   105篇
  1980年   104篇
  1979年   104篇
  1978年   63篇
  1977年   81篇
  1975年   65篇
  1974年   52篇
  1973年   74篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
In order to demonstrate a possible complement activation during early bronchospastic reaction in asthma, we have measured plasmatic C3d (a split product of C3) and the C3d/C3 index, both of which are sensitive indices of complement activation. Twenty-nine allergenic bronchial challenge tests were accomplished, with an absence of response in six cases, an early reaction in sixteen cases and a dual reaction in seven cases. Changes in plasmatic C3d or C3d/C3 five min after an early reaction, or five min after the last dose of allergen (in the six cases without bronchial response) were insignificant. However, complement activation in the lungs during asthmatic reaction cannot be completely excluded without studies using the bronchoalveolar technique.  相似文献   
25.
Resting energy expenditures (REEs) were measured in 40 alcoholic cirrhotic (AC) patients by indirect calorimetry and corrected for 24-h urinary creatinine and excretion. These REEs were compared according to the stage of severity of the cirrhosis, the nutritional status, and the presence or absence of alcoholic hepatitis (AH). Mean REE was not significantly different between the Child class A, B, and C patients, even when corrected for 24-h urinary creatinine. Mean REE was significantly less in malnourished AC than in well-nourished patients (1308 +/- 285 vs. 1531 +/- 255 kcal, p less than 0.02). However, when measured energy expenditure was corrected for 24-h urinary creatinine, the difference between the two groups of patients disappeared (1800 +/- 540 kcal/g creatinine in malnourished patients vs. 1890 +/- 780 kcal/g creatinine in well-nourished patients). Finally, there was no significant difference between the REE, corrected or not, for the 24-h urinary creatinine in AC with or without AH. Thus, when REE is normalized to lean body mass, represented by 24-h urinary creatinine, the metabolic activity in AC is not dependent on the severity of the cirrhosis, nutritional status, or existence of AH.  相似文献   
26.
The stability of tolerance ofStaphylococcus aureus during subculturing at 37°C and development of this property after repeated exposure to cloxacillin or vancomycin were investigated in vitro. Four of five tolerant strains lost this property during repeated subculturing at 37°C for 50 days. Conversely, tolerance emerged in two of four nontolerant strains after repeated cycles of exposure to 25 µg of cloxacillin/ml or 10 µg of vancomycin/ml alternating with growth in antibiotic-free medium. Previous in vivo exposure to cloxacillin did not enhance the development of tolerance in vitro. MICs of both cloxacillin and vancomycin did not change significantly during this procedure. Whether the conversion of nontolerant strains to the tolerant state can also occur during antibiotic exposure in treatment of patients remains to be determined.  相似文献   
27.
28.
29.
30.
Detailed analyses of the neuropathologic changes in the cerebralcortex of elderly individuals and Alzheimer's disease patientshave demonstrated that certain components of the neocorticaland hippocampal circuits are likely to be selectively vulnerable.Based on the distribution of neurofibrillary tangles (NFTs)and senile plaques, it has been proposed that a global cortico-corticaldisconnection leads to the loss of integrated functions observedin Alzheimer's disease. In order to investigate the distributionof lesions associated with aging as well as with the earliestsymptoms of senile dementia, we performed a quantitative neuropathologicavaluation of a large series of elderly patients representingthe entire autopsy population for the year 1989 from a geriatrichospital. Among the 145 cases quantitatively assessed, therewere 102 nondemented patients, 33 patients presenting clinicallywith globally intact intellectual function but early signs ofimpairment of specific cognitive functions, and 10 cases withsenile dementia of the Alzheimer type. All of the cases hadNFTs in layer II of the entorhinal cortex, regardless of theirclinical diagnosis, and most cases had some NFTs in the CA1field of the hippocampus. Severe pathologic changes within theinferior temporal neocortex were observed only in the dementedcases. The extent of amyloid deposition was not correlated withthe clinical diagnosis and seemed to be present in the neocorticalareas earlier than in the hippocampal formation. Also, severalcases contained NFTs without amyloid deposition, but amyloidnever occurred without NFTs. These results suggests that involvementof certain structures within the hippocampal formation is aconsistent feature of aging. Thus, involvement of the hippocampalformation may be a necessary, but not sufficient, conditionfor the clinical expression of dementia, which is likely tobe more closely related to the progressive degeneration of selectneuronal populations in the neocortex.  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