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   4577篇
  免费   346篇
  国内免费   139篇
耳鼻咽喉   8篇
儿科学   19篇
妇产科学   58篇
基础医学   359篇
口腔科学   345篇
临床医学   213篇
内科学   1054篇
皮肤病学   117篇
神经病学   112篇
特种医学   150篇
外科学   392篇
综合类   471篇
现状与发展   1篇
预防医学   655篇
眼科学   31篇
药学   762篇
  5篇
中国医学   216篇
肿瘤学   94篇
  2024年   2篇
  2023年   59篇
  2022年   164篇
  2021年   342篇
  2020年   197篇
  2019年   162篇
  2018年   174篇
  2017年   188篇
  2016年   170篇
  2015年   191篇
  2014年   308篇
  2013年   381篇
  2012年   244篇
  2011年   345篇
  2010年   270篇
  2009年   235篇
  2008年   232篇
  2007年   201篇
  2006年   141篇
  2005年   142篇
  2004年   115篇
  2003年   106篇
  2002年   73篇
  2001年   79篇
  2000年   48篇
  1999年   46篇
  1998年   53篇
  1997年   48篇
  1996年   32篇
  1995年   37篇
  1994年   32篇
  1993年   30篇
  1992年   18篇
  1991年   15篇
  1990年   19篇
  1989年   15篇
  1988年   17篇
  1987年   11篇
  1986年   12篇
  1985年   21篇
  1984年   11篇
  1983年   18篇
  1982年   15篇
  1981年   8篇
  1980年   10篇
  1979年   3篇
  1978年   9篇
  1977年   4篇
  1976年   5篇
  1974年   2篇
排序方式: 共有5062条查询结果,搜索用时 31 毫秒
71.
Study ObjectiveTo assess the proportion of iron deficiency that is not detected with a screening hemoglobin or complete blood count (CBC) alone in young women with heavy menstrual bleeding.DesignRetrospective review of electronic medical records.SettingNationwide Children's Hospital in Columbus, Ohio.Participants, Interventions, and Main Outcome MeasuresOne hundred fourteen young women aged 9-19 years consecutively referred to a young women's hematology clinic with a complaint of heavy menstrual bleeding.ResultsFifty-eight (50.9%) of all patients had ferritin <20 ng/mL indicating iron deficiency. Of the 58 patients with iron deficiency, only 24 (41.4%) were anemic and 25 (46.3%) were microcytic. The sensitivity of hemoglobin alone and CBC alone for identifying women with ferritin <20 ng/mL was 41.4% (95% confidence interval [CI], 28.7-54.1) and 46.3% (95% CI, 33.0-59.6), respectively. Both tests had reasonable specificity at 91.1% (95% CI, 83.6-98.5) for hemoglobin and 83.9% for CBC (95% CI, 74.3-93.6). Patients had significantly higher odds of having iron deficiency if they were overweight or obese (odds ratio, 2.81; 95% CI, 1.25-6.29) compared with patients with normal body mass index. Age at presentation for heavy menstrual bleeding, presence of an underlying bleeding disorder, and median household income were not significantly associated with iron deficiency.ConclusionIn adolescents with heavy menstrual bleeding, fewer than half of iron deficiency cases are detected when screening is performed with hemoglobin or blood count alone. Measuring ferritin levels in at-risk patients might allow for earlier implementation of iron therapy and improvement in symptoms.  相似文献   
72.
Takashi Ando 《Materials》2012,5(3):478-500
Current status and challenges of aggressive equivalent-oxide-thickness (EOT) scaling of high-κ gate dielectrics via higher-κ (>20) materials and interfacial layer (IL) scavenging techniques are reviewed. La-based higher-κ materials show aggressive EOT scaling (0.5–0.8 nm), but with effective workfunction (EWF) values suitable only for n-type field-effect-transistor (FET). Further exploration for p-type FET-compatible higher-κ materials is needed. Meanwhile, IL scavenging is a promising approach to extend Hf-based high-κ dielectrics to future nodes. Remote IL scavenging techniques enable EOT scaling below 0.5 nm. Mobility-EOT trends in the literature suggest that short-channel performance improvement is attainable with aggressive EOT scaling via IL scavenging or La-silicate formation. However, extreme IL scaling (e.g., zero-IL) is accompanied by loss of EWF control and with severe penalty in reliability. Therefore, highly precise IL thickness control in an ultra-thin IL regime (<0.5 nm) will be the key technology to satisfy both performance and reliability requirements for future CMOS devices.  相似文献   
73.
Here, we developed the lysozyme imprinted bacterial cellulose (Lyz-MIP/BC) nanofibers via the surface imprinting strategy that was designed to recognize lysozyme. This study includes the molecular imprinting method onto the surface of bacterial cellulose nanofibers in the presence of lysozyme by metal ion coordination, as well as further characterizations methods FTIR, SEM and contact angle measurements. The maximum lysozyme adsorption capacity of Lyz-MIP/BC nanofibers was found to be 71 mg/g. The Lyz-MIP/BC nanofibers showed high selectivity for lysozyme towards bovine serum albumin and cytochrome c. Overall, the Lyz-MIP/BC nanofibers hold great potential for lysozyme recognition due to the high binding capacity, significant selectivity and excellent reusability.  相似文献   
74.
The aim of this study was to analyze the impact of hydrodynamic forces on the multiplication of E. coli, and biofilm formation and dispersion. The experiments were provided in a flow chamber simulating a cleaning-in-place system. Biofilm biomass was measured using a crystal violet dye method. The results show that hydrodynamic forces affect not only biofilm formation and dispersion but the multiplication of E. coli in the first place. We found more biofilm biomass on the rough surface than on the smooth one. The results of the biofilm formation test show that laminar flow promotes the biofilm growth over 72 h, meanwhile turbulent flow after 48 h causes decrease in biomass. The results of the biofilm dispersion test, in contrast, show that laminar flow removed less biofilm from both materials that turbulent flow did. Therefore, taking into account these findings in cleaning-in-place technology can substantially reduce E. coli multiplication and biofilm formation.  相似文献   
75.
ObjectivesThe aim of this study was to explore the heterogeneous association of consumption of food away from home (FAFH) with individual body mass outcomes including body mass index and waist circumference over the entire conditional distribution of each outcome.MethodsInformation on 16 403 adults obtained from nationally representative data on nutrition and behavior in Korea was used. A quantile regression model captured the variability of the association of FAFH with body mass outcomes across the entire conditional distribution of each outcome measure. Heavy FAFH consumption was defined as obtaining ≥1400 kcal from FAFH on a single day.ResultsHeavy FAFH consumption, specifically at full-service restaurants, was significantly associated with higher body mass index (+0.46 kg/m2 at the 50th quantile, 0.55 at the 75th, 0.66 at the 90th, and 0.44 at the 95th) and waist circumference (+0.96 cm at the 25th quantile, 1.06 cm at the 50th, 1.35 cm at the 75th, and 0.96 cm at the 90th quantiles) with overall larger associations at higher quantiles. Findings of the study indicate that conventional regression methods may mask important heterogeneity in the association between heavy FAFH consumption and body mass outcomes.ConclusionFurther public health efforts are needed to improve the nutritional quality of affordable FAFH choices and nutrition education and to establish a healthy food consumption environment.  相似文献   
76.
Welders are inhalatively exposed to fumes which contain genotoxic carcinogens and it was found in epidemiological studies that they have increased cancer rates which may be causally related to DNA damage. In order to assess their health risks and to find out which chemicals cause the adverse effects, bioassays can be performed which enable the detection of genetic damage. The aim of the present study was a comparative investigation with exfoliated buccal and nasal cells in regard to induction of chromosomal alterations and acute cytotoxicity in welders and unexposed controls (n = 22 per group). To elucidate the factors which account for genotoxic and cytotoxic effects, additional biochemical parameters were monitored reflecting the redox status as well as concentrations of different metals and 1-hydroxypyrene (1-OHP) in body fluids. We found in the nasal cells significant induction of alterations which are indicative for DNA damage, i.e. of micronuclei (MNi) and nuclear buds, while elevated rates of nuclear anomalies reflecting cytotoxic effects (condensed chromatin, karyorrhexis, karyolylsis) were detected in cells from both organs. The levels of certain metals (Cr, Cu, Mn, Mo, Ni), but not markers of oxidative damage were significantly higher in the body fluids of the welders. Multivariate Poisson regression analyses indicate that exposure to Mo (15% MNi increase by one standard deviation increase of Mo in serum), Ni (9% increase) and Mn (14% increase) are positively associated with the induction of MNi in nasal cells while Ni was associated with cytotoxic effects in both types of cells (12 and 16% increase). Taken together, our findings indicate that epithelial cells from the respiratory tract are suitable for the detection of DNA-damaging and cytotoxic effects in welders and can be used to assess health risks associated with genomic instability.  相似文献   
77.
78.
79.
We investigated the efficacy of non‐metal clasp dentures (NMCDs) with regard to the oral health‐related quality of life (OHRQoL) and compare the findings with those for conventional metal clasp‐retained dentures (MCDs). This single‐centre, randomised controlled, two‐phase, open label, cross‐over trial included 28 partially dentate individuals. The patients were randomised to receive MCDs followed by NMCDs, or the opposite sequence (n = 14 in each group); each denture was worn for 3 months. OHRQoL was evaluated using the Oral Health Impact Profile‐Japanese version (OHIP‐J) at entry (T‐entry; before treatment with the first denture) and at 3 months after treatment with each denture (T3). An examiner evaluated denture stability, oral appearance and surface roughness before denture delivery (T0) and at T3 and denture hygiene at T3. A total of 24 patients completed the trial. There were no complications related to the dentures, abutment teeth or denture‐bearing mucosa during the follow‐up periods for both dentures. The mean OHIP summary score was lower for NMCDs than for MCDs, and the difference (9 points) was greater than the minimal important difference (6 points), indicating the difference was clinically relevant. The effect size was medium (0·70). Statistical analyses with linear mixed models found a significant effect of the denture type on the OHIP summary score and scores for the Oro‐facial appearance, Oro‐facial pain and Psychological impact domains (NMCD < MCD; P < 0·05). The results of our study suggest that NMCDs allow for better OHRQoL compared with MCDs.  相似文献   
80.
《Indian heart journal》2021,73(6):740-742
Long term outcome data after BMS implant is not available from the Indian subcontinent. This is a prospective observational study which aims to study long term outcomes after BMS implant at a tertiary care centre. 100 consecutive patients underwent BMS implant and were followed up for 20 years. LAD was the most common vessel involved and different types of BMS were implanted. All-cause mortality was noted in 21% (n = 21) whereas cardiac mortality was seen in 16% (n = 16). Cumulative revascularisation free survival at 20 years was 71%. The study showed that long term outcomes after BMS implant were fare and acceptable.  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