全文获取类型
收费全文 | 2145738篇 |
免费 | 154199篇 |
国内免费 | 5026篇 |
专业分类
耳鼻咽喉 | 30613篇 |
儿科学 | 68487篇 |
妇产科学 | 61929篇 |
基础医学 | 304621篇 |
口腔科学 | 63176篇 |
临床医学 | 187724篇 |
内科学 | 415815篇 |
皮肤病学 | 48977篇 |
神经病学 | 170129篇 |
特种医学 | 84379篇 |
外国民族医学 | 720篇 |
外科学 | 328000篇 |
综合类 | 50768篇 |
现状与发展 | 6篇 |
一般理论 | 792篇 |
预防医学 | 157995篇 |
眼科学 | 50464篇 |
药学 | 158865篇 |
6篇 | |
中国医学 | 4542篇 |
肿瘤学 | 116955篇 |
出版年
2018年 | 20355篇 |
2016年 | 18155篇 |
2015年 | 20479篇 |
2014年 | 28445篇 |
2013年 | 43461篇 |
2012年 | 56943篇 |
2011年 | 60536篇 |
2010年 | 36171篇 |
2009年 | 34670篇 |
2008年 | 57386篇 |
2007年 | 61843篇 |
2006年 | 62789篇 |
2005年 | 60581篇 |
2004年 | 59049篇 |
2003年 | 57158篇 |
2002年 | 55748篇 |
2001年 | 99614篇 |
2000年 | 102235篇 |
1999年 | 86379篇 |
1998年 | 23703篇 |
1997年 | 21504篇 |
1996年 | 21035篇 |
1995年 | 20042篇 |
1994年 | 18753篇 |
1993年 | 17431篇 |
1992年 | 68189篇 |
1991年 | 66242篇 |
1990年 | 65282篇 |
1989年 | 63553篇 |
1988年 | 58585篇 |
1987年 | 58229篇 |
1986年 | 55207篇 |
1985年 | 52797篇 |
1984年 | 39547篇 |
1983年 | 33502篇 |
1982年 | 20106篇 |
1981年 | 18294篇 |
1979年 | 37542篇 |
1978年 | 26943篇 |
1977年 | 23231篇 |
1976年 | 21325篇 |
1975年 | 23535篇 |
1974年 | 28215篇 |
1973年 | 27284篇 |
1972年 | 25799篇 |
1971年 | 24088篇 |
1970年 | 22727篇 |
1969年 | 21651篇 |
1968年 | 20145篇 |
1967年 | 18095篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
101.
Lindsey Haynes-Maslow Lauri Andress Stephanie Jilcott Pitts Isabel Osborne Barbara Baquero Lisa Bailey-Davis Carmen Byker-Shanks Bailey Houghtaling Jane Kolodinsky Brian K. Lo Emily H. Morgan Emily Piltch Elaine Prewitt Rebecca A. Seguin Alice S. Ammerman 《Journal of the Academy of Nutrition and Dietetics》2018,118(9):1664-1672
Background
In 2016, the US Department of Agriculture (USDA)’s Supplemental Nutrition Assistance Program (SNAP) Retailer Rule proposed several changes for SNAP-authorized retailers, including: requiring retailers to have at least 85% of their food sales come from items that are not cooked or heated on site before or after purchase; requiring stores to stock seven varieties of qualifying foods from four staple food groups; requiring stores to carry perishable foods in three of the four staple groups; requiring stores to carry six units of qualifying foods at all times (depth of stock); disqualifying multiple ingredient foods and accessory foods from counting toward depth of stock requirements.Objectives
To better understand arguments used to support or oppose the USDA’s proposed rule that all SNAP-authorized retailers carry more nutritious foods.Design
We conducted a qualitative content analysis of a random sample of public comments posted to the US Federal Register (a publicly available database) in response to the USDA’s proposed rule.Participants/setting
A random sample of 20% of all public comments submitted by individuals and organizations to the US Federal Register were analyzed (n=303) for this study.Results
Three main themes were discussed: 1) arguments used in opposition to the rule; 2) arguments used in support of the rule; and 3) facilitators to assist stores in implementing the rule. Some of the subthemes included focusing on definitions used in the rule, reduced food access caused by stores leaving the SNAP program, lack of space and equipment for healthy foods, and the potential for increasing healthy food access.Conclusions
Nutrition and dietetics practitioners may be tasked with working with stores to implement healthy changes. Nutrition and dietetics practitioners must understand the role that the USDA has in food policy. In addition, understanding how federal food policy influences the environments in which dietetics professionals’ clients are making food choices is important. 相似文献102.
Luis Alfonso Ortíz-Reyes Lilia Castillo-Martínez Arianne Itzel Lupián-Angulo Daniel Dante Yeh Héctor Isaac Rocha-González Aurora Elizabeth Serralde-Zúñiga 《Journal of the Academy of Nutrition and Dietetics》2018,118(1):52-61
Background
Unintentional underfeeding is common in patients receiving enteral nutrition (EN), and is associated with increased risk of malnutrition complications. Protocols for EN in critically ill patients have been shown to enhance adequacy, resulting in better clinical outcomes; however, outside of intensive care unit (ICU) settings, the influence of a protocol for EN is unknown.Objective
To evaluate the efficacy and safety of implementing an EN protocol in a noncritical setting.Design
Randomized controlled clinical trial.Participants and settings
This trial was conducted from 2014 to 2016 in 90 adult hospitalized patients (non-ICU) receiving exclusively EN. Patients with carcinomatosis, ICU admission, or <72 hours of EN were excluded.Intervention
The intervention group received EN according to a protocol, whereas the control group was fed according to standard practice.Main outcome measures
The proportion of patients receiving ≥80% of their caloric target at Day 4 after EN initiation.Statistical analyses performed
Student t test or Wilcoxon rank-sum test were used for continuous variables and the difference between the groups in the time to receipt of the optimal amount of nutrition was analyzed using Kaplan-Meier curves.Results
Forty-five patients were randomized to each group. At Day 4 after EN initiation, 61% of patients in the intervention arm had achieved the primary end point compared with 23% in the control group (P=0.001). In malnourished patients, 63% achieved the primary end point in the intervention group compared with 16% in the control group (P=0.003). The cumulative deficit on Day 4 was lower in the intervention arm compared with the control arm: 2,507 kcal (interquartile range [IQR]=1,262 to 2,908 kcal) vs 3,844 kcal (IQR=2,620 to 4,808 kcal) (P<0.001) and 116 g (IQR=69 to 151 g) vs 191 g (IQR=147 to 244 g) protein (P<0.001), respectively. The rates of gastrointestinal complications were not significantly different between groups.Conclusions
Implementation of an EN protocol outside the ICU significantly improved the delivery of calories and protein when compared with current standard practice without increasing gastrointestinal complications. 相似文献103.
Laura A. Smith Ciara H. O’Flanagan Laura W. Bowers Emma H. Allott Stephen D. Hursting 《Journal of the Academy of Nutrition and Dietetics》2018,118(4):652-667
Prevalence of obesity, an established risk factor for many cancers, has increased dramatically over the past 50 years in the United States and across the globe. Relative to normoweight cancer patients, obese cancer patients often have poorer prognoses, resistance to chemotherapies, and are more likely to develop distant metastases. Recent progress on elucidating the mechanisms underlying the obesity?cancer connection suggests that obesity exerts pleomorphic effects on pathways related to tumor development and progression and, thus, there are multiple opportunities for primary prevention and treatment of obesity-related cancers. Obesity-associated alterations, including systemic metabolism, adipose inflammation, growth factor signaling, and angiogenesis, are emerging as primary drivers of obesity-associated cancer development and progression. These obesity-associated host factors interact with the intrinsic molecular characteristics of cancer cells, facilitating several of the hallmarks of cancer. Each is considered in the context of potential preventive and therapeutic strategies to reduce the burden of obesity-related cancers. In addition, this review focuses on emerging mechanisms behind the obesity?cancer link, as well as relevant dietary interventions, including calorie restriction, intermittent fasting, low-fat diet, and ketogenic diet, that are being implemented in preclinical and clinical trials, with the ultimate goal of reducing incidence and progression of obesity-related cancers. 相似文献
104.
Camila L.P. Oliveira Stephanie Mattingly Ralf Schirrmacher Michael B. Sawyer Eugene J. Fine Carla M. Prado 《Journal of the Academy of Nutrition and Dietetics》2018,118(4):668-688
The predominant use of glucose anaerobically by cancer cells (Warburg effect) may be the most important characteristic the majority of these cells have in common and, therefore, a potential metabolic pathway to be targeted during cancer treatment. Because this effect relates to fuel oxidation, dietary manipulation has been hypothesized as an important strategy during cancer treatment. As such, the concept of a ketogenic diet (KD) in cancer emerged as a metabolic therapy (ie, targeting cancer cell metabolism) rather than a dietary approach. The therapeutic mechanisms of action of this high-fat, moderate-to-low protein, and very-low-carbohydrate diet may potentially influence cancer treatment and prognosis. Considering the lack of a dietetics-focused narrative review on this topic, we compiled the evidence related to the use of this diet in humans with diverse cancer types and stages, also focusing on the nutrition and health perspective. The use of KD in cancer shows potentially promising, but inconsistent, results. The limited number of studies and differences in study design and characteristics contribute to overall poor quality evidence, limiting the ability to draw evidence-based conclusions. However, the potential positive influences a KD may have on cancer treatment justify the need for well-designed clinical trials to better elucidate the mechanisms by which this dietary approach affects nutritional status, cancer prognosis, and overall health. The role of registered dietitian nutritionists is demonstrated to be crucial in planning and implementing KD protocols in oncology research settings, while also ensuring patients’ adherence and optimal nutritional status. 相似文献
105.
Partition coefficients between human stratum corneum lipids and water (Ksclip/w) are collected or deduced from a variety of sources in a manner that approximately doubles the available data compared to the current state-of-the-art model (Hansen et al., Adv Drug Deliv Rev. 2013;65(2):251-264). An additional datum for water itself in porcine SC that considerably extends the molecular size and lipophilicity range of the data set is considered. The data are analyzed in terms of an extended linear free energy relationship involving octanol/water partition coefficients, Abraham solvation parameters, and a secondary, power law molecular weight dependence. The optimum fit to log Ksclip/w for the full data set reduces the standard error of prediction from 0.50 for a Hansen-like model to 0.39; corresponding multiplicative errors in Ksclip/w are reduced from a factor of 3.1 to one of 2.5. The difference in performance is driven by the water datum, which requires a more complex dependence on molecular size than that afforded by Abraham parameters. In the absence of the water value, the Hansen-like model, which does not include a dependence on molecular size, is essentially optimum. A comparison is presented to fluid-phase phospholipid–water systems, which have a demonstrably different structure–property relationship. 相似文献
106.
107.
Ronald T. Toth Samantha E. Pace Brittney J. Mills Sangeeta B. Joshi Reza Esfandiary C. Russell Middaugh David D. Weis David B. Volkin 《Journal of pharmaceutical sciences》2018,107(4):1009-1019
Antibodies are molecules that exhibit diverse conformational changes on different timescales, and there is ongoing interest to better understand the relationship between antibody conformational dynamics and storage stability. Physical stability data for an IgG4 monoclonal antibody (mAb-D) were gathered through traditional forced degradation (temperature and stirring stresses) and accelerated stability studies, in the presence of different additives and solution conditions, as measured by differential scanning calorimetry, size exclusion chromatography, and microflow imaging. The results were correlated with hydrogen exchange mass spectrometry (HX-MS) data gathered for mAb-D in the same formulations. Certain parameters of the HX-MS data, including hydrogen exchange in specific peptide segments in the CH2 domain, were found to correlate with stabilization and destabilization of additives on mAb-D during thermal stress. No such correlations between mAb physical stability and HX-MS readouts were observed under agitation stress. These results demonstrate that HX-MS can be set up as a streamlined methodology (using minimal material and focusing on key peptide segments at key time points) to screen excipients for their ability to physically stabilize mAbs. However, useful correlations between HX-MS and either accelerated or real-time stability studies will be dependent on a particular mAb's degradation pathway(s) and the type of stresses used. 相似文献
108.
Ying Wan John M. Hickey Christopher Bird Katey Witham Paul Fahey Angus Forster Sangeeta B. Joshi David B. Volkin 《Journal of pharmaceutical sciences》2018,107(6):1540-1551
The worldwide switch to inactivated polio vaccines (IPVs) is a key component of the overall strategy to achieve and maintain global polio eradication. To this end, new IPV vaccine delivery systems may enhance patient convenience and compliance. In this work, we examine Nanopatch? (a solid, polymer microprojection array) which offers potential advantages over standard needle/syringe administration including intradermal delivery and reduced antigen doses. Using trivalent IPV (tIPV) and a purpose-built evaporative dry-down system, candidate tIPV formulations were developed to stabilize tIPV during the drying process and on storage. Identifying conditions to minimize tIPV potency losses during rehydration and potency testing was a critical first step. Various classes and types of pharmaceutical excipients (~50 total) were then evaluated to mitigate potency losses (measured through D-antigen ELISAs for IPV1, IPV2, and IPV3) during drying and storage. Various concentrations and combinations of stabilizing additives were optimized in terms of tIPV potency retention, and 2 candidate tIPV formulations containing cyclodextrin and a reducing agent (e.g., glutathione), maintained ≥80% D-antigen potency during drying and subsequent storage for 4 weeks at 4°C, and ≥60% potency for 3 weeks at room temperature with the majority of losses occurring within the first day of storage. 相似文献
109.
Ashaben Patel Vineet Gupta John Hickey Nancy S. Nightlinger Richard S. Rogers Christine Siska Sangeeta B. Joshi Michael S. Seaman David B. Volkin Bruce A. Kerwin 《Journal of pharmaceutical sciences》2018,107(12):3032-3046
In this study, we investigated analytical challenges associated with the formulation of 2 anti-HIV broadly neutralizing antibodies (bnAbs), 3BNC117 and PGT121, both separately at 100 mg/mL and together at 50 mg/mL each. The bnAb formulations were characterized for relative solubility and conformational stability followed by accelerated and real-time stability studies. Although the bnAbs were stable during 4°C storage, incubation at 40°C differentiated their stability profiles. Specific concentration-dependent aggregation rates at 30°C and 40°C were measured by size exclusion chromatography for the individual bnAbs with the mixture showing intermediate behavior. Interestingly, although the relative ratio of the 2 bnAbs remained constant at 4°C, the ratio of 3BNC117 to PGT121 increased in the dimer that formed during storage at 40°C. A mass spectrometry-based multiattribute method, identified and quantified differences in modifications of the Fab regions for each bnAb within the mixture including clipping, oxidation, deamidation, and isomerization sites. Each bnAb showed slight differences in the levels and sites of lysine residue glycations. Together, these data demonstrate the ability to differentiate degradation products from individual antibodies within the bnAb mixture, and that degradation rates are influenced not only by the individual bnAb concentrations but also by the mixture concentration. 相似文献
110.
Iman M.N. Hamdan Ismaiel A. Tekko Kyle B. Matchett Luis G. Arnaut Claudia S. Silva Helen O. McCarthy Ryan F. Donnelly 《Journal of pharmaceutical sciences》2018,107(9):2439-2450
Nodular basal cell carcinoma is a deep skin lesion and one of the most common cancers. Conventional photodynamic therapy is limited to treatment of superficial skin lesions. The parenteral administration of near-IR preformed photosensitizers suffers from poor selectivity and may result in prolonged skin photosensitivity. Microneedles (MNs) can provide localized drug delivery to skin lesions. Intradermal delivery of the preformed near-IR photosensitizer; 5,10,15,20-tetrakis(2,6-difluoro-3-N-methylsulfamoylphenyl bacteriochlorin (Redaporfin?) using dissolving MN was successful in vitro and in vivo. MN demonstrated complete dissolution 30 min after skin application and showed sufficient mechanical strength to penetrate the skin to a depth of 450 μm. In vitro deposition studies illustrated that the drug was delivered and detected down to 5 mm in skin. In vivo biodistribution studies in athymic nude mice Crl:NU(NCr)-Foxn1nu showed both fast initial release and localized drug delivery. The MN-treated mice showed a progressive decrease in the fluorescence intensity at the application site over the 7-day experiment period, with the highest and lowest fluorescence intensities measured being 9.2 × 1010 ± 2.5 × 1010 and 3.8 × 109 ± 1.6 × 109 p/s, respectively. By day 7, there was some migration of fluorescence away from the site of initial MN application. However, the majority of the body surfaces showed fluorescence levels that were comparable to those seen in the negative control group. This work suggests utility for polymeric MN arrays in minimally invasive intradermal delivery to enhance photodynamic therapy of deep skin lesions. 相似文献