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   1460篇
  免费   67篇
  国内免费   14篇
耳鼻咽喉   28篇
儿科学   109篇
妇产科学   41篇
基础医学   231篇
口腔科学   24篇
临床医学   71篇
内科学   371篇
皮肤病学   17篇
神经病学   123篇
特种医学   15篇
外科学   127篇
综合类   8篇
预防医学   133篇
眼科学   24篇
药学   125篇
中国医学   1篇
肿瘤学   93篇
  2023年   9篇
  2022年   81篇
  2021年   104篇
  2020年   24篇
  2019年   30篇
  2018年   32篇
  2017年   31篇
  2016年   30篇
  2015年   28篇
  2014年   42篇
  2013年   54篇
  2012年   100篇
  2011年   112篇
  2010年   60篇
  2009年   44篇
  2008年   74篇
  2007年   83篇
  2006年   86篇
  2005年   73篇
  2004年   68篇
  2003年   61篇
  2002年   50篇
  2001年   19篇
  2000年   22篇
  1999年   20篇
  1998年   7篇
  1997年   8篇
  1993年   7篇
  1992年   14篇
  1991年   10篇
  1990年   12篇
  1989年   5篇
  1988年   14篇
  1987年   8篇
  1986年   7篇
  1985年   6篇
  1981年   4篇
  1980年   5篇
  1979年   11篇
  1977年   5篇
  1976年   5篇
  1975年   5篇
  1974年   7篇
  1973年   8篇
  1972年   6篇
  1970年   5篇
  1969年   5篇
  1968年   4篇
  1967年   4篇
  1966年   4篇
排序方式: 共有1541条查询结果,搜索用时 0 毫秒
11.
The growing popularity of health education on social media indicates the need for its appropriate evaluation. This paper aims to present the potential of the Kirkpatrick Model (KM) with New World Kirkpatrick Model (NWKM) additions to evaluate the nutritional education provided by dieticians via Instagram. Instagram profiles of ten dieticians providing nutritional education for their followers were analyzed in March and April 2021. The study sample included profiles of both macro- and micro-influencers. The analyzed quantitative data included Instagram Engagement Rate and the number of likes and comments per post. The qualitative analysis of the comments was performed following the theoretical framework provided by the KM and NWKM. Collected data showed followers’ satisfaction, commitment, and relevance of the presented content, fulfilling the Level 1 of NWKM. Level 2 of NWKM was represented by 4 out of 5 dimensions (knowledge, attitude, confidence, commitment). No comments were found only for skills. Both Levels 3 (Behavior) and 4 (Results) of the KM were met. However, the use of the NWKM for them seems limited. The KM can be used to evaluate nutritional education on social media. The NWKM additions seem applicable mostly for Levels 1 and 2.  相似文献   
12.
A newly elaborated method, "Wombling," for detecting regions of abrupt change in biological variables was applied to 63 human allele frequencies in Europe. Of the 33 gene-frequency boundaries discovered in this way, 31 are coincident with linguistic boundaries marking contiguous regions of different language families, languages, or dialects. The remaining two boundaries (through Iceland and Greece) separate descendants of different ethnic or geographical provenance but lack modern linguistic correlates. These findings support a model of genetic differentiation in Europe in which the genetic structure of the population is determined mainly by gene flow and admixture, rather than by adaptation to varying environmental conditions. Of the 33 boundaries, 27 reflect diverse population origins at often distant locations. Language affiliation of European populations plays a major role in maintaining and probably causing genetic differences.  相似文献   
13.
Effect of nociceptin on alcohol intake in alcohol-preferring rats   总被引:7,自引:0,他引:7  
The present study investigated the effect of nociceptin (NC), the endogenous ligand of the opioid-like orphan receptor ORL1, on ethanol intake in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. Acute intracerebroventricular (ICV) injection of 250 or 500 ng/rat of NC, just before access to 10% ethanol (offered 2 h/day), significantly increased ethanol intake. Subchronic (7 days) ICV injection of 500 ng/rat of NC, given just before access to 10% ethanol (for 30 min/day), resulted in a progressive decrease in ethanol consumption. After the end of NC treatment, rats progressively recovered their usual ethanol intake. When NC, 500 or 1000 ng/rat, was tested versus the effect of ethanol in the place conditioning paradigm, NC significantly reduced the increase in time spent in the ethanol-paired compartment after conditioning. This finding suggests that NC reduces the rewarding properties of ethanol in msP rats; thus, they may respond to the acute NC administration by increasing their ethanol intake in an attempt to achieve the usual reinforcing effect of ethanol, whereas subchronic NC treatment may result in extinction of ethanol drinking. The results of the present study suggest that the brain NC mechanisms may represent an interesting target of pharmacological interventions for the treatment of alcoholism. Received: 11 August 1998/Final version: 15 October 1998  相似文献   
14.
Between 1984 and 1996, the authors performed 499 liver transplants in 416 children less than 15 years old. The overall patient survival at 10 years was 76.5%. It was 71.3% for the 209 children grafted in 1984–1990; 78.5% for biliary atresia (n =?286), 87.3% for metabolic diseases (n?=?59), and 72.7% for acute liver failure (n?=?22). The 5-year survival was 73.6% for the 209 children grafted in 1984–1990 and 85% for the 206 grafted in 1991–1996. Scarcity of size-matched donors led to the development of innovative techniques: 174 children who electively received a reduced liver as a first graft in our center had a 5-year survival of 76% while 168 who received a full-size graft had a survival of 85% (NS). Results of the European Split Liver Registry showed 6-month graft survival similar to results obtained with full-size grafts collected by the European Liver Transplant Registry. Extensive use of these techniques allowed the mortality while waiting to be reduced from 16.5% in 1984–1990 to 10% in 1991–1992. It rose again to 17% in 1993, leading the authors to develop a program of living related liver transplantation (LRLT). The legal and ethical aspects are analyzed. Between July 1993 and October 1997, the authors performed 53 LRLTs with 90% survival. In elective cases, a detailed analysis was made of the 45 children listed for LRLT between July 1993 and March 1997 and the 79 registered on the cadaveric waiting list during the same period. Mortality while waiting was 2% and 14.5% for the LRLT and cadaveric lists, respectively. The retransplantation rate was 4.6% and 16.1% for LRLT and cadaveric transplants, respectively. Overall post-transplant survival was 88% and 82% for children who received a LRLT or a cadaveric graft, respectively. Overall survival from the date of registration was 86% and 70% (P?<?0.05) for LRLT or cadaveric LT respectively. The 2-year post-transplant survival in children less than 1?year of age at transplantation was 88.8% and 80.3% with a LRLT or cadaveric graft, respectively; patient survival after 3 months post-transplant was 95.8% and 91.9% for stable children waiting at home, 93.7% and 93.7% in children hospitalized for complications of their disease, and 89.5% and 77.7% for children hospitalized in an intensive care unit at the time of transplantation for children who received a LRLT or cadaveric graft, respectively. It is concluded that LRLT seems to be justified for multidisciplinary teams having a large experience with reduced and split liver grafting.  相似文献   
15.
This paper presents an assessment of the possibility of using digital image classifiers for tomographic images concerning ductile iron castings. The results of this work can help the development of an efficient system suggestion allowing for decision making regarding the qualitative assessment of the casting process parameters. Special attention should be focused on the fact that automatic classification in the case of ductile iron castings is difficult to perform. The biggest problem in this aspect is the high similarity of the void image, which may be a sign of a defect, and the nodular graphite image. Depending on the parameters, the tests on different photos may look similar. Presented in this article are test scenarios of the module analyzing two-dimensional tomographic images focused on the comprehensive assessment by convolutional neural network models, which are designed to classify the provided image. For the purposes of the tests, three such models were created, different from each other in terms of architecture and the number of hyperparameters and trainable parameters. The described study is a part of the decision-making system, supporting the process of qualitative analysis of the obtained cast iron castings.  相似文献   
16.
Cement paste powder (CPP) is a by-product of the recycling process of concrete with an elevated carbonation capability and potential to be recycled as a binding material in new concrete batches. The application of a carbonation treatment to CPP improves this potential even more, besides the evident gains in terms of CO2 net balance. However, the long duration usually adopted in this treatment, from 3 to 28 days, hampers the industrial viability of the process. We studied the feasibility of a short-duration carbonation process, with a duration of two hours, carrying out a comprehensive characterization of the material throughout the process. The test was performed on CPP with an average initial water content of 16.9%, exposed to a CO2 concentration of 80%. The results demonstrate two main carbonation rates: a rapid growth rate in the first 18 minutes of the process, involving all the calcium-bearing compounds in CPP, and a slow growth rate afterwards, where only C-S-H contributes to the carbonation reaction. During the 2 h carbonation process, the main CPP compounds, calcium silicate hydrate (C-S-H) and calcium hydroxide (CH), reached different carbonation degrees, 31% and 94%, with, however, close CO2 uptake values, 8% and 11%, respectively. Nevertheless, the total CO2 uptake for this process (≈19%) attained values not distant from the values usually obtained in a carbonation of 12 days or more (19–25%). Hence, these findings highlight the blocking role of C-S-H in the carbonation process, indicating that longer carbonation periods are only going to be useful if an effective carbonation of this compound is accomplished. In the present scenario, where CH is the main contributor to the reaction, the reduction in the process duration is feasible.  相似文献   
17.
The conversion of kinetic energy from wind and solar radiation into electricity during the operation of wind and photovoltaic power plants causes practically no emissions of chemical compounds that are harmful to the environment. However, the production of their materials and components, as well as their post-use management after the end of their operation, is highly consumptive of energy and materials. For this reason, this article aims to assess the life cycle of a wind and photovoltaic power plant in the context of the sustainable development of energy systems. The objects of the research were two actual technical facilities—a 2 MW wind power plant and a 2 MW photovoltaic power plant, both located in Poland. The analysis of their life cycle was carried out on the basis of the LCA (life-cycle assessment) method, using the ReCiPe 2016 calculation procedure. The impact of the examined renewable energy systems was assessed under 22 impact categories and 3 areas of influence (i.e., human health, ecosystems, and resources), and an analysis was conducted for the results obtained as part of three compartments (i.e., air, water, and soil). The life cycle of the wind power plant was distinguished by a higher total potential negative environmental impact compared to the life cycle of the photovoltaic power plant. The highest levels of potential harmful impacts on the environment in both life cycles were recorded for areas of influence associated with negative impacts on human health. Emissions to the atmosphere accounted for over 90% of all emissions in the lifetimes of both the wind and the photovoltaic power plants. On the basis of the obtained results, guidelines were proposed for pro-ecological changes in the life cycle of materials and elements of the considered technical facilities for renewable energy sources, aimed at better implementation of the main assumptions of contemporary sustainable development (especially in the field of environmental protection).  相似文献   
18.
A rise in the incidence of infections with severe acute respiratory syndrome coronavirus 2 has sparked the search for protective strategies against the new pathogen. It is known that individual food components can interact with different immune cells, modulating the immune response of the body. The aim of this study was to develop an index assessing the immunomodulatory potential of diet (POLA index) and to test its utility for the prediction of coronavirus disease 2019 (COVID-19) in a group of healthy young people following a traditional or vegetarian diet. Data on body composition, anthropometric measurements, physical activity, dietary intake, and gut microbiota were obtained from 95 adults (mean age, 34.66 ± 5.76 years). There was a strong correlation between the dietary inflammatory index and the POLA index (r = 0.90; p < 0.0001). Based on Cohen’s kappa statistic, there was a good agreement in qualitative interpretation between the two indices (kappa = 0.61; p < 0.0001). People on a diet with beneficial immunomodulatory effects had a lower risk of COVID-19 of approximately 80%, as compared with those on a diet with highly unbeneficial immunomodulatory effects. In daily practice, the POLA index might serve as a useful tool for dietitians to identify individuals whose diet is deficient in ingredients for optimal immune system function and change their dietary behavior to ensure optimal immune function that reduces the risk of infection.  相似文献   
19.
Relationships between diet, sex hormone concentrations, and the estrous cycle are important from the perspective of infertility and estrogen-dependent disease prevention and treatment. Four dietary interventions reflecting modern eating behaviors were explored. The study involved 50 female rats divided into five feeding groups. The impact of the amount of sucrose consumed (9% and 18% of the dietary energy content), alternating high-sucrose and sucrose-free diets, and a high-sucrose diet combined with intermittent one-day fasting on the estrous cycle and sex hormone concentrations in female rats was assessed. Even low amounts of dietary sucrose (9% of the dietary energy content) were found to lead to increased estradiol (E2) concentrations and decreased progesterone (Pg) concentrations. A high-sucrose diet, even when periodically applied, additionally led to a reduced concentration of luteinizing hormone (LH). The largest changes in the hormones tested were observed with one-day fasting coupled with the high-sucrose diet; in addition, the estrous phase was shortened and the estrous cycle was disrupted. The results of this study show that both the amount of dietary sucrose and also its uptake pattern affect the estrous cycle and sex hormone concentrations in female rats.  相似文献   
20.
Very preterm infants are usually supported by parenteral nutrition delivered through central lines (CLs) while progressing with enteral intake, although the optimal time point for their removal is unclear. This study evaluated the impact of the CL discontinuation time on the short-term growth outcomes of preterm infants. A non-inferiority, parallel-group, randomized controlled trial was conducted in four neonatal intensive care units in Poland. Preterm infants with very low birth weight (VLBW) without congenital abnormalities were eligible. Patients were allocated to discontinue central access at an enteral feeding volume of 100 mL/kg/day (intervention group) or 140 mL/kg/day (control group). The study’s primary outcome was weight at 36 weeks’ postmenstrual age, with a non-inferiority margin of −210 g. Overall, 211 patients were allocated to the intervention or control groups between January 2019 and February 2021, of which 101 and 100 were eligible for intention-to-treat analysis, respectively. The mean weight was 2232 g and 2200 g at 36 weeks’ postmenstrual age in the intervention and control groups, respectively. The mean between-group difference was 32 g (95% confidence interval, −68 to 132; p = 0.531), which did not cross the specified margin of non-inferiority. No intervention-related adverse events were observed. Early CL removal was non-inferior to the standard type for short-term growth outcomes in VLBW infants.  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