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   1438031篇
  免费   96390篇
  国内免费   1605篇
耳鼻咽喉   17564篇
儿科学   47598篇
妇产科学   38040篇
基础医学   206161篇
口腔科学   36457篇
临床医学   130202篇
内科学   278490篇
皮肤病学   28036篇
神经病学   118082篇
特种医学   55376篇
外国民族医学   265篇
外科学   206864篇
综合类   28275篇
现状与发展   3篇
一般理论   579篇
预防医学   122279篇
眼科学   30908篇
药学   102318篇
  31篇
中国医学   2678篇
肿瘤学   85820篇
  2018年   34186篇
  2017年   26738篇
  2016年   29809篇
  2015年   14054篇
  2014年   18931篇
  2013年   28543篇
  2012年   44625篇
  2011年   60205篇
  2010年   40847篇
  2009年   33367篇
  2008年   56474篇
  2007年   61109篇
  2006年   40895篇
  2005年   41510篇
  2004年   41120篇
  2003年   40461篇
  2002年   37631篇
  2001年   56472篇
  2000年   57572篇
  1999年   48398篇
  1998年   13663篇
  1997年   12516篇
  1996年   12811篇
  1995年   12081篇
  1994年   11250篇
  1993年   10506篇
  1992年   38349篇
  1991年   37857篇
  1990年   36648篇
  1989年   35415篇
  1988年   32838篇
  1987年   32155篇
  1986年   30638篇
  1985年   28901篇
  1984年   22039篇
  1983年   19285篇
  1982年   11452篇
  1981年   10394篇
  1979年   21015篇
  1978年   15457篇
  1977年   12844篇
  1976年   11898篇
  1975年   12854篇
  1974年   15654篇
  1973年   15408篇
  1972年   14564篇
  1971年   13589篇
  1970年   12836篇
  1969年   12101篇
  1968年   11264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
Little is known about the development of psychosis during hydroxychloroquine (HCQ) treatment, especially in elderly patients affected by rheumatic diseases, with multiple comorbidities and treatments. To summarize the available evidence on HCQ-induced psychosis in elders, we performed a literature review. Additionally, individual case safety reports sent to the European Pharmacovigilance database (EudraVigilance) with HCQ as suspected drug and related to adverse events belonging to the System Organ Class ‘Psychiatric disorders’ were shown. Over the years, evidence was published about the risk of neuropsychiatric clinical manifestations during HCQ treatment for rheumatic diseases, but few of them were related to elderly patients. These adverse events can include less severe clinical manifestations such as affect lability and nervousness or more severe conditions such as actual psychosis and suicidal tendencies, which frequency are actually unknown. The presence of risk factors in these patients may precipitate HCQ-induced psychosis and their precocious detection could be associated with a risk minimization. Among predisposing risk factors, there are the co-exposure to interacting drugs, alcohol intake, familial history of psychiatric diseases, female gender, and the concomitant use of low-dose glucocorticoids. In some cases it was possible to reverse psychotic behaviour with the antipsychotic treatment or with HCQ suspension.  相似文献   
95.
Oxidative stress and inflammation are intricately interlinked as aetiological factors in the context of ageing and chronic disease-related accelerated ageing. Previous research by our group has highlighted the anti-oxidant and anti-inflammatory potential of grape-derived polyphenols in the context of acute inflammation and oxidative stress. The aim here was to add to this by assessing efficacy of the treatment (acutely) to address ageing-associated cumulative pro-oxidant and pro-inflammatory changes in an in vitro model. Blood from young and aged humans was analysed for baseline oxidative stress and inflammatory status. Isolated neutrophils were acutely exposed to the polyphenol treatment in vitro. The chemokinetic capacity of treated and control neutrophils in response to fMLP was subsequently determined in a Dunn chamber, using live cell imaging. Neutrophils were also analysed for the expression of selected molecular markers associated with functional capacity and oxidative stress. Results indicate that the aged population had significantly worse oxidative stress and inflammatory profiles (higher plasma conjugated dienes and MPO) than young controls. Neutrophils isolated from both young and aged individuals had improved chemokinetic accuracy and capacity after in vitro polyphenol treatment. Additionally, increased shedding of CD16 and expression of CD66b suggested sites via which the polyphenol achieved improved neutrophil motility. We conclude that grape seed-derived polyphenols facilitated improved neutrophil functionality by acting on the molecular targets elucidated here.  相似文献   
96.
Background: Excessive drinking is commonplace at UK Universities. Individuals may misperceive how much they drink compared to others and are less likely to think that they will suffer adverse consequences. Young people often distance themselves and their friends from ‘problem drinkers’. Objectives: The aim of the study was to explore how student drinkers compared their own drinking behaviors to the drinking behaviors of others. Methods: An online survey was completed by 416 students aged 18–30 (68.5% female). They were asked ‘how do you think your drinking compares with other people like you?' and ‘how do you think your behavior when you drink compares with other people like you?’ Answers were subjected to thematic analysis. Results: The first main theme was about ‘identification as a ‘good’ drinker’. Participants suggested their own behavior when drinking was similar to their sober behavior. Further, they viewed themselves as more able to maintain a balance between staying in control and having fun while drinking. The second main theme was about ‘distancing from being a ‘bad’ drinker. Participants distanced themselves from negative prototypical drinkers, such compulsive or anti-social drinkers. They also attributed their own drinking behaviors to situational factors, but described other people as intentionally violent or aggressive. Conclusions/Importance: These findings may explain the failure of some health messages to change drinking behaviors. If drinkers perceive that their behavior when they drink is better than other people's then they may discount intervention messages. Targeting these biases could be incorporated into future interventions.  相似文献   
97.
Pharmaceuticals are ubiquitous in the natural environment with concentrations expected to rise as human population increases. Environmental risk assessments are available for a small portion of pharmaceuticals in use, raising concerns over the potential risks posed by other drugs that have little or no data. With >1900 active pharmaceutical ingredients in use, it would be a major task to test all of the compounds with little or no data. Desk-based prioritization studies provide a potential solution by identifying those substances that are likely to pose the greatest risk to the environment and which, therefore, need to be considered a priority for further study. The aim of this review was to (1) provide an overview of different prioritization exercises performed for pharmaceuticals in the environment and the results obtained; and (2) propose a new holistic risk-based prioritization framework for drugs in the environment. The suggested models to underpin this framework are discussed in terms of validity and applicability. The availability of data required to run the models was assessed and data gaps identified. The implementation of this framework may harmonize pharmaceutical prioritization efforts and ensure that, in the future, experimental resources are focused on molecules, endpoints, and environmental compartments that are biologically relevant.  相似文献   
98.
Two new flavonol glycosides, bootanenside I and II (1 and 2), along with ten known compounds (312), were isolated from whole plant of Liparis bootanensis Griff. Their structures were elucidated on the basis of extensive spectroscopic analyses, including high-resolution electrospray-ionization mass spectrometry (HR–ESIMS) and one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR). The cytotoxicity of the compounds was investigated against HCT116 human cancer cell line, revealing that none of them possessed considerable cytotoxic activity. Bioassays of the new metabolites showed that compounds 1 and 2 displayed moderate in vitro antiinflammatory activity by inhibiting expression of inducible nitric oxide synthase (iNOS) protein in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells.  相似文献   
99.
Miroestrol and deoxymiroestrol are the most potent phytoestrogens of Pueraria candollei var. mirifica, having been proved as an effective herb for menopausal symptoms in folk medicines and clinical trials. To ensure efficacy and safety of P. candollei var. mirifica involved in nutraceutical products being available worldwide, the content of potent phytoestrogens as active ingredients should be specified. Therefore, in this study, we produced a monoclonal antibody for total analysis of potent estrogenic miroestrol and deoxymiroestrol, for which an analytical method was developed using a procedure for an indirect competitive enzyme-linked immunosorbent assay. The antibody exhibited equal reactivity against miroestrol and deoxymiroestrol. The sensitivity of determination was in the range of 31.3–500 ng/ml with high precision. The analytical parameters, such as accuracy (99.6–106% recovery) and high correlation with a HPLC–UV method, indicated the reliability of analysis. This method is of high performance, and it is cheap to control optimal miroestrol and deoxymiroestrol doses of P. candollei var. mirifica nutraceutical products.  相似文献   
100.
Lignans are widely distributed in plants and exhibit significant pharmacological effects, including anti-tumor and antioxidative activities. Here, we describe the total synthesis of schizandriside (1), a compound we previously isolated from Saraca asoca by monitoring antioxidative activity using the 1,1-diphenyl-2-picrylhydrazyl radical scavenging assay. Starting from a tandem Michael-aldol reaction, the lignan skeleton was synthesized in 6 steps, including a cyclization step. To determine the stereochemistry of 1, we synthesized the natural product (±)-isolariciresinol (18) from alcohol 17. Comparison of the spectral data showed good agreement. Glycosylation was investigated using four different glycosyl donors. Only the Koenigs–Knorr condition using silver trifluoromethanesulfonate with 1,1,3,3-tetramethylurea provided the glycosylated product. Deprotection and purification using reverse-phase high-performance liquid chromatography gave schizandriside (1) and its diastereomer saracoside (2). Synthesized 1, 2 and 18 showed antioxidant activity with IC50?=?34.4, 28.8, 53.0 μM, respectively.  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