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   5723篇
  免费   389篇
  国内免费   33篇
耳鼻咽喉   58篇
儿科学   184篇
妇产科学   123篇
基础医学   664篇
口腔科学   194篇
临床医学   488篇
内科学   1298篇
皮肤病学   151篇
神经病学   297篇
特种医学   144篇
外国民族医学   4篇
外科学   797篇
综合类   215篇
一般理论   2篇
预防医学   469篇
眼科学   111篇
药学   535篇
中国医学   69篇
肿瘤学   342篇
  2023年   76篇
  2022年   149篇
  2021年   333篇
  2020年   168篇
  2019年   217篇
  2018年   210篇
  2017年   170篇
  2016年   218篇
  2015年   226篇
  2014年   274篇
  2013年   332篇
  2012年   490篇
  2011年   524篇
  2010年   277篇
  2009年   218篇
  2008年   336篇
  2007年   277篇
  2006年   284篇
  2005年   258篇
  2004年   208篇
  2003年   176篇
  2002年   175篇
  2001年   31篇
  2000年   33篇
  1999年   39篇
  1998年   32篇
  1997年   22篇
  1996年   20篇
  1995年   24篇
  1994年   26篇
  1993年   23篇
  1992年   19篇
  1991年   12篇
  1990年   21篇
  1989年   23篇
  1988年   18篇
  1987年   24篇
  1986年   17篇
  1985年   9篇
  1984年   8篇
  1983年   15篇
  1982年   14篇
  1981年   14篇
  1980年   8篇
  1979年   7篇
  1977年   9篇
  1975年   8篇
  1974年   6篇
  1972年   6篇
  1971年   8篇
排序方式: 共有6145条查询结果,搜索用时 15 毫秒
41.
Strict environmental concern, depletion, and price hike of building construction materials are driving scientific studies for the search of alternative materials for building construction. To this end sustainable building materials could be a fruitful solution. This review aims to discern the environmental efficacy of solid waste management (SWM) and its relationship with four stimuli i.e., economic structure, regulatory structure, science, and time. The study also highlights the investigation of governance network to figure out the regulatory structure and governance of waste management. Extensive details on solid waste with their sources, recycling potential and their current utilization for substantial development are outlined. A throughout of the production process, properties, advantages, disadvantages, and the global economy of building material developed through recycling of solid waste are discussed. This article also deals with the sustainability, social, and environmental impact of green building materials. The study identifies the future direction for the effective utilization of solid waste for developing building materials. Further, the scope of the present also focusses on the concept of circular economy for developing construction materials through recycling of solid waste, which provides an easy reference for solid waste processing towards sustainability.  相似文献   
42.
We hypothesized that administration of clonidine would decrease the hypocapnic apnoeic threshold (HAT) and widen the CO2 reserve during non-REM sleep.  相似文献   
43.
44.
45.
46.
The non-stationary and multi-frequency nature of biomedical signal activities makes the use of time-frequency distributions (TFDs) for analysis inevitable. Time-frequency analysis provides simultaneous interpretations in both time and frequency domain enabling comprehensive explanation, presentation and interpretation of electrocardiogram (ECG) signals. The diversity of TFDs and specific properties for each type show the need to determine the best TFD for ECG analysis. In this study, a performance evaluation of five TFDs in term of ECG abnormality detection is presented. The detection criteria based on extracted features from most important ECG signal components (QRS) to detect normal and abnormal cases. This is achieved by estimating its energy concentration magnitude using the TFDs. The TFDs analyse ECG signals in one-minute interval instead of conventional time domain approach that analyses based on beat or frame containing several beats. The MIT-BIH normal sinus rhythm ECG database total records of 18 long-term ECG sampled at 128 Hz have been analysed. The tested TFDs include Dual-Tree Wavelet Transform, Spectrogram, Pseudo Wigner-Ville, Choi-Williams, and Born-Jordan. Each record is divided into one-minute slots, which is not considered previously, and analysed. The sample periods (slots) are randomly selected ten minutes interval for each record. This result with 99.44% detection accuracy for 15,735 ECG beats shows that Choi-Williams distribution is most reliable to be used for heart problem detection especially in automated systems that provide continuous monitoring for long time duration.  相似文献   
47.
48.
Context: Azadirachta indica A. Juss. (Meliaceaes) leaves have been used traditionally to treat swelling and rheumatism in Indian cultures.

Objective: To fractionate A. indica leaf extracts using bioactivity guided manner for identification of the active anti-inflammatory principles.

Materials and methods: Polarity-gradient sequential extracts (petroleum ether, chloroform, methanol, and water) of A. indica leaves were screened for their anti-inflammatory potential using the carrageenan-induced rat paw edema model (1?g/kg). The chloroform extract was sequentially fractionated to obtain n-hexane (F-1), n-hexane-chloroform (F-2), and chloroform (F-3) fractions and their inhibitory effect on rat paw edema was evaluated (500?mg/kg). Inhibitory effect of F-2 on granuloma formation, plasma interleukin (IL-1), and tumor necrosis factor (TNF-α) was assessed at the doses of 100, 200, and 400?mg/kg using the cotton pellet assay in rats. Three sub-fractions (SF-1, SF-2, and SF-3) were obtained upon chromatography of F-2, and their inhibitory effect on cyclooxygenase was assessed at 200?µg/mL concentration. The sub-fractions were subjected to gas chromatography–mass spectrometry (GC-MS).

Results: All the extracts showed significant anti-inflammatory effect; however, chloroform extract was the most effective against paw edema (53.25% inhibition). The three fractions of chloroform extract showed significant effect, while F-2 being the most potent (51.02%). F-2 demonstrated dose-dependent inhibition of granuloma and cytokines. Interestingly, all the sub-fractions of F-2 inhibited COX-1 and COX-2 with almost equal potential. GC-MS revealed that chemically the sub-fractions were totally different from each other.

Discussion and conclusion: Anti-inflammatory effect of A. indica is a result of cumulative and synergistic effects of diversified constituents with varying polarities that collectively exert the effect via suppression of cyclo-oxygenases and cytokines (IL-1 and TNF-α).  相似文献   
49.
Psychosocial profiles among a convenience sample of 37 Malay Muslim participants of Inabah program were measured using the Psychological Measure of Islamic Religiousness (PMIR). Data were analysed using SPSS 23.0. Positive relations with others emerged as the best-scored subscale whereas anger trait and depressed mood were minimal. Single and divorced respondents demonstrated significantly higher score for purpose in life. More favorable social desirability was reported by participants with no previous treatment. Less anger and depression were expressed by those not detained before. Essentially, psychosocial status of persons with substance use disorder undergoing Inabah program was moderate with some influences of sociodemographic factors.  相似文献   
50.
Among microcytic hypochromic anemias, the most common disorders are iron deficiency anemia and co-pathological conditions such as α- or β-thalassemia (α- or β-thal) traits. The aim of the present study was to determine the frequency and prevalence of iron deficiency anemia and α- or β-thal traits based on clinical laboratory data across different ethnic groups in five districts of Sindh Province, Pakistan. The present retrospective study analyzed 3 years (2012–2015) of encoded and unlinked clinical laboratory data, and identified 3030 microcytic hypochromic anemia cases. The data contained complete blood counts (CBCs) with smear morphology examinations, serum ferritin levels, and hemoglobin (Hb) electrophoreses. After reviewing the data, 994 confirmed subjects (iron deficiency anemia and α- and β-thal traits) were then selected for the present study. The prevalence of α- and β-thal traits was highest in Badin district (35.27%), while the prevalence of iron deficiency anemia was highest in Larkana district (30.73%). According to the ethnic-wise distribution, higher numbers of α- and β-thal trait cases were seen in the Sindhi ethnic group [375 (64.21%) and 283 (69.02%), respectively] than in the other ethnic groups. In addition, a higher distribution of β-thal trait cases was observed in the Sindhi ethnic group [n?=?327 (56%)] in α- and β-thal cases overall. Findings from the present study strongly suggested that screening is important not only for β-thal trait but also other traits as well. However, careful monitoring of CBC parameters, including red blood cell (RBC) indices and morphology, along with clinical findings are essential to diagnose carrier cases, especially in high prevalence areas.  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