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   1349022篇
  免费   100577篇
  国内免费   2007篇
耳鼻咽喉   17489篇
儿科学   42992篇
妇产科学   36166篇
基础医学   200031篇
口腔科学   36828篇
临床医学   126183篇
内科学   266364篇
皮肤病学   28697篇
神经病学   110053篇
特种医学   50285篇
外国民族医学   266篇
外科学   192651篇
综合类   26471篇
现状与发展   3篇
一般理论   756篇
预防医学   110504篇
眼科学   29687篇
药学   97751篇
  47篇
中国医学   2146篇
肿瘤学   76236篇
  2021年   12471篇
  2019年   12863篇
  2018年   16413篇
  2017年   12363篇
  2016年   13500篇
  2015年   15454篇
  2014年   21375篇
  2013年   31817篇
  2012年   44043篇
  2011年   46573篇
  2010年   26728篇
  2009年   25488篇
  2008年   43220篇
  2007年   45614篇
  2006年   45077篇
  2005年   44139篇
  2004年   42073篇
  2003年   40119篇
  2002年   38620篇
  2001年   56556篇
  2000年   57442篇
  1999年   48673篇
  1998年   14162篇
  1997年   12821篇
  1996年   13138篇
  1995年   12416篇
  1994年   11500篇
  1992年   38488篇
  1991年   37932篇
  1990年   36693篇
  1989年   35486篇
  1988年   32945篇
  1987年   32251篇
  1986年   30767篇
  1985年   29035篇
  1984年   22247篇
  1983年   19446篇
  1982年   11656篇
  1979年   21071篇
  1978年   15563篇
  1977年   12936篇
  1976年   11951篇
  1975年   12915篇
  1974年   15688篇
  1973年   15451篇
  1972年   14582篇
  1971年   13624篇
  1970年   12838篇
  1969年   12113篇
  1968年   11270篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
61.
Introduction: Intra-articular (IA) corticosteroid (CS) injections are commonly used in the treatment of osteoarthritis. However, they are rarely utilized in haemophilic arthropathy. In fact, the efficacy of this method in haemophilic arthropathy is frequently discussed and debated in clinical practice.

Aim: To investigate the effectiveness of IA CS injections in patients with painful haemophilic arthropathy.

Methods: A review of the literature on the topic was performed.

Results: In osteoarthritis, reports with a high level of evidence state that the efficacy of IA injections of CS is controversial. In haemophilic arthropathy, some low-level evidence reports seem to indicate that short-term pain alleviation can be achieved.

Conclusions: Considering that pain relief after IA injections of CS is controversial and that the cost of the haematologic treatment required to perform the procedure is high in haemophilic arthropathy, we do not recommend the routine use of CS IS injections in haemophilia. Moreover, point of care (POC) ultrasound (US)-guided injections are not advised, because the injection procedure is so simple that the use of POC-US will unnecessarily prolong the duration of the procedure.  相似文献   

62.

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   
63.
64.
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   
65.
The macrocycle para-sulfonatocalix[8]arene, sCX[8], was examined with 2 antibiotic drugs, ciprofloxacin (CIP) and isoniazid. The drugs were shown to form complexes with sCX[8] using proton nuclear magnetic resonance, thermogravimetric analysis, fluorescence spectroscopy, and molecular modeling. Both drugs form 1:1 hydrated (H2O: 13%-14% w/w) host-guest complexes, with sCX[8] binding around the pyridine ring of isoniazid, and around the piperazine and cyclopropane rings of CIP. From proton nuclear magnetic resonance, the binding constant of isoniazid to sCX[8] was 6.8 (±0.3) × 103 M?1. Addition of 2 equivalents of sCX[8] to CIP resulted in a 58% decrease in fluorescence, and time-resolved fluorescence anisotropy of CIP doubles with sCX[8]. Each drug binds into the cavity of the macrocycle, with binding stabilized via combinations of hydrogen bonding, electrostatic interactions, π-π stacking, and hydrophobic effects. The safety of sCX[8] was examined in vitro with human embryonic kidney 293 cells. The IC50 of sCX[8] was 559 μM, which is a minimum of 5-fold higher than the concentration that would be used in the clinic. The in vitro effect of sCX[8] on the action of CIP was examined on a panel of bacterial lines. The results showed that sCX[8] has no inherent antibiotic activity and had no negative effect on the action of CIP.  相似文献   
66.
Administration of local anesthetics is one of the most effective pain control techniques for postoperative analgesia. However, anesthetic agents easily diffuse into the injection site, limiting the time of anesthesia. One approach to prolong analgesia is to entrap local anesthetic agents in nanostructured carriers (e.g., liposomes). Here, we report that using an ammonium sulphate gradient was the best strategy to improve the encapsulation (62.6%) of dibucaine (DBC) into liposomes. Light scattering and nanotracking analyses were used to characterize vesicle properties, such as, size, polydispersity, zeta potentials, and number. In vitro kinetic experiments revealed the sustained release of DBC (50% in 7 h) from the liposomes. In addition, in vitro (3T3 cells in culture) and in vivo (zebrafish) toxicity assays revealed that ionic-gradient liposomes were able to reduce DBC cyto/cardiotoxicity and morphological changes in zebrafish larvae. Moreover, the anesthesia time attained after infiltrative administration in mice was longer with encapsulated DBC (27 h) than that with free DBC (11 h), at 320 μM (0.012%), confirming it as a promising long-acting liposome formulation for parenteral drug administration of DBC.  相似文献   
67.

Background

Postmenstrual and/or gestational age-corrected age (CA) is required to apply child growth standards to children born preterm (< 37 weeks gestational age). Yet, CA is rarely used in epidemiologic studies in low- and middle-income countries (LMICs), which may bias population estimates of childhood undernutrition. To evaluate the effect of accounting for GA in the application of growth standards, we used GA-specific standards at birth (INTERGROWTH-21st newborn size standards) in conjunction with CA for preterm-born children in the application of World Health Organization Child Growth Standards postnatally (referred to as ‘CA’ strategy) versus postnatal age for all children, to estimate mean length-for-age (LAZ) and weight-for-age (WAZ) z scores at 0, 3, 12, 24, and 48-months of age in the 2004 Pelotas (Brazil) Birth Cohort.

Results

At birth (n = 4066), mean LAZ was higher and the prevalence of stunting (LAZ < ?2) was lower using CA versus postnatal age (mean ± SD): ? 0.36 ± 1.19 versus ? 0.67 ± 1.32; and 8.3 versus 11.6%, respectively. Odds ratio (OR) and population attributable risk (PAR) of stunting due to preterm birth were attenuated and changed inferences using CA versus postnatal age at birth [OR, 95% confidence interval (CI): 1.32 (95% CI 0.95, 1.82) vs 14.7 (95% CI 11.7, 18.4); PAR 3.1 vs 42.9%]; differences in inferences persisted at 3-months. At 12, 24, and 48-months, preterm birth was associated with stunting, but ORs/PARs remained attenuated using CA compared to postnatal age. Findings were similar for weight-for-age z scores.

Conclusions

Population-based epidemiologic studies in LMICs in which GA is unused or unavailable may overestimate the prevalence of early childhood undernutrition and inflate the fraction of undernutrition attributable to preterm birth.
  相似文献   
68.
1.?Human cytosolic sulfotransferase 1B1 (SULT1B1) sulfates small phenolic compounds and bioactivates polycyclic aromatic hydrocarbons. To date, no SULT1B1 allelic variants have been well-characterized.

2.?While cloning SULT1B1 from human endometrial specimens, an allelic variant resulting in valine instead of leucine at the 145th amino acid position (L145V) was detected. NCBI reported this alteration as the highest frequency SULT1B1 allelic variant.

3.?L145V frequency comprised 9% of 37 mixed-population human patients and was specific to African Americans with an allelic frequency of 25%. Structurally, replacement of leucine with valine potentially destabilizes a conserved helix (α8) that forms the “floor” of both the substrate and PAPS binding domains. This destabilization results in altered kinetic properties including a four-fold decrease in affinity for PAP (3′, 5′-diphosphoadenosine). Kms for 3′-phosphoadenosine- 5′-phosphosulfate (PAPS) are similar; however, maximal turnover rate of the variant isoform (0.86?pmol/(min*μg)) is slower than wild-type (WT) SULT1B1 (1.26?pmol/(min*μg)). The L145V variant also displays altered kinetics toward small phenolic substrates, including a diminished p-nitrophenol Km and increased susceptibility to 1-naphthol substrate inhibition.

4.?No significant correlation between genotype and prostate or colorectal cancer was observed in patients; however, the variant isoform could underlie specific pathologies in sub-Saharan African carriers.  相似文献   
69.
70.
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