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   5580篇
  免费   515篇
  国内免费   19篇
耳鼻咽喉   52篇
儿科学   195篇
妇产科学   129篇
基础医学   684篇
口腔科学   36篇
临床医学   793篇
内科学   966篇
皮肤病学   136篇
神经病学   322篇
特种医学   615篇
外科学   696篇
综合类   173篇
一般理论   3篇
预防医学   559篇
眼科学   43篇
药学   383篇
肿瘤学   329篇
  2022年   33篇
  2021年   78篇
  2020年   58篇
  2019年   80篇
  2018年   101篇
  2017年   53篇
  2016年   81篇
  2015年   80篇
  2014年   146篇
  2013年   172篇
  2012年   240篇
  2011年   283篇
  2010年   134篇
  2009年   141篇
  2008年   251篇
  2007年   257篇
  2006年   219篇
  2005年   263篇
  2004年   197篇
  2003年   165篇
  2002年   177篇
  2001年   144篇
  2000年   173篇
  1999年   157篇
  1998年   80篇
  1997年   81篇
  1996年   99篇
  1995年   98篇
  1994年   91篇
  1993年   86篇
  1992年   136篇
  1991年   125篇
  1990年   125篇
  1989年   127篇
  1988年   126篇
  1987年   126篇
  1986年   125篇
  1985年   127篇
  1984年   98篇
  1983年   87篇
  1982年   62篇
  1981年   34篇
  1980年   42篇
  1979年   52篇
  1978年   50篇
  1977年   36篇
  1976年   52篇
  1975年   36篇
  1974年   36篇
  1971年   29篇
排序方式: 共有6114条查询结果,搜索用时 15 毫秒
71.
To determine how women in pregnancy would like to be addressed and to ascertain their preferred choice of title during pregnancy. A questionnaire was administered to 925 antenatal women. Midwifery and medical staff (183) were invited to respond to a similar questionnaire. The response rate was 71.2% from the survey of pregnant women. The vast majority (82.1%) preferred to be addressed by their first name. Women were in favour of being called 'patient' (32.8%) as their first choice. The staff survey yielded a response rate of 77%. The majority (81.8%) of health professionals preferred to address women by their first name. 'Mother' (28.7%) was the most popular first choice. We conclude that women in pregnancy do have a preference on how they would like to be addressed and this is predominantly by first name. Health professionals also prefer to call pregnant women by their first name. The term 'patient' was the most popular first choice of title of women in pregnancy but the term 'mother' was the preferred choice of the health professionals. Medical staff were more likely to choose 'patient' than midwives.  相似文献   
72.
We investigated the effects of silica (SiO2) and titanium dioxide (TiO2) on the pulmonary recruitment of inflammatory cells and the ability of alveolar macrophages (AMs) to release the pro-inflammatory cytokines, interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF). Rats were intratracheally instilled with 5 to 100 mg/kg of the materials, and bronchoalveolar lavage cell populations and AM cytokine release were characterized on days 1, 7, 14, and 28. Both dusts elicited dose-related increases in neutrophils, lymphocytes, and AMs; however, this response was more pronounced and persistent with SiO2. SiO2 at greater than or equal to 50 mg/kg increased AM release of IL-1 and TNF at all time points; lower SiO2 doses had either a transient or no effect on AM-derived cytokines. TiO2 did not result in AM IL-1 release and increased TNF release transiently at doses greater than or equal to 50 mg/kg. Both dusts primed AMs to release increased levels of IL-1 and TNF upon in vitro stimulation with lipopolysaccharide. Histopathology (day 28) demonstrated dose-related interstitial inflammation associated with SiO2 exposure, an effect that was less severe with TiO2. SiO2 doses of greater than or equal to 50 mg/kg elicited a granulomatous response. Development of granulomatous inflammation only at SiO2 doses for which persistent AM IL-1 release occurred suggests involvement of this cytokine in the formation of SiO2-induced granulomas. The ability of SiO2 to activate AM release of IL-1 and TNF in a more pronounced and persistent manner than TiO2 is likely responsible, at least in part, for the greater inflammation and pneumotoxicity associated with SiO2.  相似文献   
73.
74.
The development of left ventricular hypertrophy in patients with heart disease often has far-reaching clinical implications with respect to overall morbidity and mortality. Approaches used to assess left ventricular mass include electrocardiography, echocardiography, contrast ventriculography, single photon-emission tomography, and conventional computed tomography. However, all of these modalities suffer from some major draw back that precludes widespread application to all patients. In this study we assessed the accuracy of determinations of left ventricular mass in 22 dogs by rapid-acquisition (50 msec) computed axial tomography (RACAT), an ultrafast computed tomographic (CT) instrument. Electrocardiographically triggered, end-diastolic, short-axis cardiac scans were obtained from apex to base during administration of intravenous iodinated contrast. Myocardial edges were determined for each tomographic scan by two methods: the regional half-contour method (the CT density half way between that of the left ventricular myocardium and adjacent ventricular cavities or lung) and "interactive plateau thresholding" of the cardiac borders. Left ventricular mass by RACAT was calculated as the sum of the mass of each individual scan from apex to base (modified Simpson's rule). Postmortem left ventricular mass ranged from 58 to 160 g. The correlation between true left ventricular mass and tomographically determined mass was excellent (r = .99), with the slope and y intercept not statistically different from 1 and 0, respectively. The standard error of the estimate was 4.1 g. Interobserver and intraobserver variability for determining left ventricular mass demonstrated excellent agreement (r = .99 and r = .99, respectively). We conclude that quantitative assessment of left ventricular mass can be accurately and reproducibly performed in dogs by rapid acquisition CT scanning. It is likely that this technique will be readily transferable to the clinical settings and prove to be an important method for quantifying left ventricular mass in patients.  相似文献   
75.
Four patients with proved osteopetrosis (three with the infantile malignant form and one with the benign form) were examined with magnetic resonance imaging at 1.5 T. All patients were studied in the coronal and sagittal planes using both short and long repetition time/echo time sequences. The infantile malignant form was characterized by a complete lack of signal from the marrow alternating with a signal intensity equivalent to that of the intervertebral disks, resulting in a "stepladder" appearance. In the benign form or after successful marrow transplantation in the infantile malignant form, intermediate or high signal intensity in the vertebrae was noted, suggesting the presence of some marrow elements.  相似文献   
76.
In a prospective randomized trial, 361 male patients with histologically proven adenocarcinoma of the rectum, judged preoperatively to require abdominoperineal resection (APR), were treated by surgery alone or were given 3,150 rads of preoperative radiotherapy. Surgical resection was done on 320 patients, 262 having "curative" APR. Only moderate symptoms from radiotherapy were noted and postoperative complications and 30-day mortality were similar in both groups. Five-year survival for curative APR was the same in both groups (50% for both treated and control patients). The incidence of positive lymph nodes in the resected specimens was 35% in treated and 41% in controls. In the first preoperative radiotherapy trial conducted by the group, 5-year survival in patients undergoing "curative" APR was 47% in treated versus 34% in control groups. Additionally, the difference in positive lymph nodes in the resected specimens was substantially greater in the first trial (26% in treated versus 44% in controls).  相似文献   
77.
Treatment of Friend erythroleukemia (FL) cells in vitro with 10(-7) to 10(-5) all-trans-retinoic acid (RA) leads to a concentration-dependent accumulation of a subpopulation of quiescent cells. This subpopulation, termed "Q-cells," contained markedly reduced RNA and protein levels and had a cell cycle distribution with a predominance of cells in G1 phase, which was nearly identical to that found in fully differentiated dimethyl sulfoxide (CAS:67-68-5; methyl sulfoxide)-induced FL cultures. The G1 cells in this RA-induced subpopulation (G1Q cells), though viable, did not enter S-phase, whereas the small percentage of Q-cells with S and G2 DNA content progressed very slowly through the cycle. While the Q-cell population did not contain the differentiation-associated chromatin protein H1 degrees, the cells did manifest a more condensed nuclear chromatin, altered sensitivity to acid denaturation, and reduced accessibility of the DNA in chromatin to acridine orange. The extent of chromatin condensation and the number of free ribosomes versus polysomes in RA-treated FL cells were intermediate between those in untreated and fully differentiated cells, whereas viral budding and the number of nucleoli remained unchanged from those seen in the untreated cell state. The non-Q-cell population in RA-treated cultures, termed "T" (transitional) cells, had an intermediate RNA and protein content and a cell cycle distribution similar to those of control cultures nearing the plateau phase of growth. In the absence of any late markers of differentiation, the Q-cell population was tentatively identified as a unique, quiescent cell population not previously described in the FL cell system.  相似文献   
78.
Background: Low energy availability results in physiological adaptations which contribute to unfavourable health outcomes. Little information exists on perceptions of nutritional advice to eat more food to maintain health and enhance performance. The aim of this study was to explore athletes’ and coaches’ perceptions towards advice to athletes to eat larger than their current quantities of food and to explore how nutritionists could deliver this advice. Methods: Semi-structured interviews (~20 min in length) were conducted using online communication technology, audio-recorded, and transcribed verbatim. The interview explored perceptions of the nutritional advice provided, its role in health and performance, and the challenges to eating larger amounts of food. Data were analysed using NVIVO 1.2 using an inductive thematic approach. Results: Nine elite athletes (female = 6; males = 3) and nine high-performance coaches (female = 3; male = 6) completed the semi-structured interviews. Athletes reported improved training consistency, fewer injuries and illnesses, and improved resilience when consuming adequate energy and nutrients to meet their needs. Lack of time and meal preparation difficulties were the main challenges faced to fuelling. Conclusions: Although education about under-fuelling is important, motivating, enabling, and supporting athletes to change behaviour is pivotal to increasing athlete self-awareness and to make long-term nutritional changes.  相似文献   
79.
BackgroundReal-time polymerase chain reaction using nasopharyngeal swabs is currently the most widely used diagnostic test for SARS-CoV-2 detection. However, false negatives and the sensitivity of this mode of testing have posed challenges in the accurate estimation of the prevalence of SARS-CoV-2 infection rates.ObjectiveThe purpose of this study was to evaluate whether technical and, therefore, correctable errors were being made with regard to nasopharyngeal swab procedures.MethodsWe searched a web-based video database (YouTube) for videos demonstrating SARS-CoV-2 nasopharyngeal swab tests, posted from January 1 to May 15, 2020. Videos were rated by 3 blinded rhinologists for accuracy of swab angle and depth. The overall score for swab angle and swab depth for each nasopharyngeal swab demonstration video was determined based on the majority score with agreement between at least 2 of the 3 reviewers. We then comparatively evaluated video data collected from YouTube videos demonstrating the correct nasopharyngeal swab technique with data from videos demonstrating an incorrect nasopharyngeal swab technique. Multiple linear regression analysis with statistical significance set at P=.05 was performed to determine video data variables associated with the correct nasopharyngeal swab technique.ResultsIn all, 126 videos met the study inclusion and exclusion criteria. Of these, 52.3% (66/126) of all videos demonstrated the correct swab angle, and 46% (58/126) of the videos demonstrated an appropriate swab depth. Moreover, 45.2% (57/126) of the videos demonstrated both correct nasopharyngeal swab angle and appropriate depth, whereas 46.8% (59/126) of the videos demonstrated both incorrect nasopharyngeal swab angle and inappropriate depth. Videos with correct nasopharyngeal swab technique were associated with the swab operators identifying themselves as a medical professional or as an Ear, Nose, Throat–related medical professional. We also found an association between correct nasopharyngeal swab techniques and recency of video publication date (relative to May 15, 2020).ConclusionsOur findings show that over half of the videos documenting the nasopharyngeal swab test showed an incorrect technique, which could elevate false-negative test rates. Therefore, greater attention needs to be provided toward educating frontline health care workers who routinely perform nasopharyngeal swab procedures.  相似文献   
80.
PurposeWe aimed to assess the prognostic value of Neutrophil to Lymphocyte Ratio (NLR) on long-term outcomes and graft dysfunction after lung transplantation.MethodsWe retrospectively reviewed all patients receiving a lung transplant at our institution from 2011 to 2014. The primary exposure was elevated NLR at the time of transplant, defined by NLR>4. The primary outcomes were graft failure and three-year all-cause mortality. Multivariate logistic regression and Kaplan-Meier survival analysis were used to analyze outcomes.Results95 patients were included. 40 patients (42%) had an elevated NLR. Elevated NLR was associated with graft failure (OR: 4.7 [1.2–18.8], p = 0.02), and three-year mortality (OR: 5.4 [1.3–23.2], p = 0.03) on multivariate logistic regression. Patients with elevated NLR demonstrated significantly lower survival on Kaplan-Meier analysis (50% versus 74%, p = 0.02). The c-statistic for our multivariate model was 0.91.ConclusionElevated neutrophil to lymphocyte ratio is associated with poor long-term survival and graft failure after lung transplantation.  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