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   1688篇
  免费   79篇
  国内免费   4篇
耳鼻咽喉   46篇
儿科学   58篇
妇产科学   130篇
基础医学   133篇
口腔科学   98篇
临床医学   151篇
内科学   380篇
皮肤病学   57篇
神经病学   139篇
特种医学   63篇
外科学   226篇
综合类   2篇
一般理论   1篇
预防医学   53篇
眼科学   22篇
药学   87篇
中国医学   2篇
肿瘤学   123篇
  2022年   12篇
  2021年   36篇
  2020年   10篇
  2019年   31篇
  2018年   24篇
  2017年   22篇
  2016年   39篇
  2015年   40篇
  2014年   36篇
  2013年   76篇
  2012年   101篇
  2011年   107篇
  2010年   59篇
  2009年   55篇
  2008年   104篇
  2007年   125篇
  2006年   130篇
  2005年   110篇
  2004年   98篇
  2003年   108篇
  2002年   83篇
  2001年   12篇
  2000年   17篇
  1999年   19篇
  1998年   9篇
  1997年   16篇
  1996年   16篇
  1995年   15篇
  1994年   13篇
  1993年   12篇
  1992年   18篇
  1991年   11篇
  1990年   12篇
  1989年   17篇
  1988年   10篇
  1987年   9篇
  1986年   8篇
  1985年   8篇
  1984年   14篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1978年   9篇
  1977年   8篇
  1975年   6篇
  1974年   6篇
  1973年   6篇
  1971年   6篇
  1970年   6篇
  1968年   6篇
排序方式: 共有1771条查询结果,搜索用时 0 毫秒
81.
The objective of this study was to compare local injections of AMS with SOC treatments for stage III and IV pressure ulcers in elderly patients. It was designed as historically prospective 2-arms non-parallel open controlled trial, and conducted in a department of geriatric medicine and rehabilitation of a university affiliated tertiary hospital. We studied 100 consecutive elderly patients with a total of 216 stage III or IV pressure ulcers, 66 patients were assigned to the AMS group and had their wounds injected, while 38 patients were assigned to the SOC group. Primary outcome was rate of complete wound closure. Time to complete wound closure and 1-year mortality served as secondary outcomes. Statistical analyses were performed at both patient and wound levels. Percentage of completely closed wounds (wound level and patient level) were significantly better (p < 0.001/p < 0.001, respectively) in all patients in favor of AMS, as well as in the subset of diabetic patients (p < 0.001/p < 0.001). Similarly, AMS proved significantly better for the subset of those with leg ulcers and with baseline wounds ≤15 cm2, compared with SOC. There were no statistically significant differences with regard to time to complete closure or 1-year mortality rates in the two groups. It is concluded that there is a significant difference in favor of stage III and IV wound closure rates by AMS, as compared with SOC treatments.  相似文献   
82.
BACKGROUND: Evidence of increased asthma and allergic response among urban versus rural residents has been reported. OBJECTIVE: To evaluate the prevalence of allergic response among asthmatic children from urban and rural areas living within close proximity. METHODS: In all, 448 asthmatic children from urban (363) and rural (85) areas were studied. The study group consisted of 234 9-year-olds and 214 12-year-olds. A health questionnaire was completed on each child who subsequently underwent allergic skin prick tests (SPTs). RESULTS: There was significantly more positive SPT response to house-dust mite, mold, cat, and cypress among asthmatic children from urban areas compared with children living in rural areas: 58.3% versus 37.6%, 46.1% versus 31.8%, 17.45 versus 5.9%, and 26.2% versus 15.3%, respectively. Positive SPT for indoor allergens were significantly greater among asthmatic urban residents than asthmatic rural residents: 63.3% versus 45.5%, respectively (P < 0.02). Positive SPT response to all the allergens checked was higher among the 12-year-old age group when compared with the 9-year-olds, 34.6% versus 22.7%, respectively (P = 0.05). CONCLUSIONS: Allergic response measured by SPT is significantly more common among asthmatic children from urban areas as opposed to rural, even though both areas are within small distance of one another. Further, asthmatic children living in urban areas demonstrated more allergic response to both indoor and outdoor allergens. The allergic response tends to increase with increased age in both urban and rural asthmatic children.  相似文献   
83.
Objective: Pregnancies among morbidly obese women are associated with serious adverse maternal and neonatal outcomes. Our study objective is to evaluate the effect of bariatric surgery on obstetrical outcomes.

Methods: We carried out a retrospective cohort study using the healthcare cost and utilization project – Nationwide Inpatient Sample from 2003 to 2011 comparing outcome of births among women who had undergone bariatric surgery with births among women with morbid obesity. Logistic regression was used to estimate the adjusted effect of bariatric surgery on maternal and newborn outcomes.

Results: There were 8 475 831 births during the study period (221 580 (2.6%) in morbidly obese women and 9587 (0.1%) in women with bariatric surgery). Women with bariatric surgery were more likely to be Caucasian and ≥35 years old as compared with morbidly obese women. As compared with women with morbid obesity, women with bariatric surgery had lower rates of hypertensive disorders, premature rupture of membrane, chorioamnionitis, cesarean delivery, instrumental delivery, postpartum hemorrhage, and postpartum infection. Induction of labor, postpartum blood transfusions, venous thromboembolisms, and intrauterine fetal growth restriction were more common in the bariatric surgery group. There were no differences observed in preterm births, fetal deaths, or reported congenital anomalies.

Conclusion: In general, women who undergo bariatric surgery have improved pregnancy outcomes as compared with morbidly obese women. However, the bariatric surgery group was more likely to have venous thromboembolisms, to require a blood transfusion, to have their labor induced and to experience fetal growth restriction.  相似文献   
84.
The time for reproduction in mammals largely depends on the availability of water and food in their habitat. Therefore, in regions where rains are limited to definite seasons of the year, mammals presumably will restrict their breeding correspondingly. But while mammals living in predictable ecosystems would benefit by timing their season to an ultimate predictable cue, such as photoperiod, in unpredictable ecosystems (e.g., deserts) they will need to use a more proximate signal. We suggest a mechanism by which water shortage (low water content in plants) could act as a proximate cue for ending the reproductive season. The golden spiny mouse (Acomys russatus), a diurnal rodent living in extreme deserts, may face an increased dietary salt content as the summer progresses and the vegetation becomes dry. Under laboratory conditions, increased diet salinity lead to reproductive hiatus in females, notable in imperforated vagina, and a significant decrease in the ovaries, uteri, and body masses. In females treated with vasopressin (VP), a hormone expressed during water stress, the uteri and body masses have decreased significantly, and the ovaries exhibited an increased number of atretic follicles. VP has also led to a significant decrease in relative medullary thickness (RMT) of the kidney. It is thus suggested that VP could act as a modulator linking the reproductive system with water economy in desert rodents, possibly through its act on the energetic pathways.  相似文献   
85.
A couple with unexplained infertility was referred for routine IVF and ICSI treatment. Ovulation was induced by the GnRH analogue protocol combined with HMG and HCG. Preparation of denuded oocytes revealed a major disorder of the zona pellucida and abnormal oocytes. During preparation of ova for ICSI, 15 retrieved oocytes were denuded, 14 of which underwent ICSI treatment. Four of the oocytes collapsed and the remaining 10 appeared to have irregular, fragile zona pellucida. Nevertheless, following ICSI, seven low-quality embryos developed, three of which were transferred into the uterus. Two implantations were achieved, but only one embryo resulted in an uneventful pregnancy and delivery by Caesarean section of a normal female neonate with an Apgar score of 10. It is hypothesized that infertility was due to the abnormal oocyte structure and abnormal zona pellucida, which prevented natural conception. This condition was successfully resolved by the ICSI procedure.  相似文献   
86.
The virulence of Bacillus anthracis, the causative agent of anthrax, stems from its antiphagocytic capsule, encoded by pXO2, and the tripartite toxins encoded by pXO1. The accepted paradigm states that anthrax is both an invasive and toxinogenic disease and that the toxins play major roles in pathogenicity. We tested this assumption by a systematic study of mutants with combined deletions of the pag, lef, and cya genes, encoding protective antigen (PA), lethal factor (LF), and edema factor (EF), respectively. The resulting seven mutants (single, double, and triple) were evaluated following subcutaneous (s.c.) and intranasal (i.n.) inoculation in rabbits and guinea pigs. In the rabbit model, virulence is completely dependent on the presence of PA. Any mutant bearing a pag deletion behaved like a pXO1-cured mutant, exhibiting complete loss of virulence with attenuation indices of over 2,500,000 or 1,250 in the s.c. or i.n. route of infection, respectively. In marked contrast, in guinea pigs, deletion of pag or even of all three toxin components resulted in relatively moderate attenuation, whereas the pXO1-cured bacteria showed complete attenuation. The results indicate that a pXO1-encoded factor(s), other than the toxins, has a major contribution to the virulence mechanism of B. anthracis in the guinea pig model. These unexpected toxin-dependent and toxin-independent manifestations of pathogenicity in different animal models emphasize the importance and need for a comprehensive evaluation of B. anthracis virulence in general and in particular for the design of relevant next-generation anthrax vaccines.  相似文献   
87.
ObjectivesThe effectiveness of remdesivir, a Food and Drug Administration-approved drug for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has been repeatedly questioned during the current coronavirus disease 2019 (COVID-19) pandemic. Most of the recently reported studies were randomized controlled multicentre clinical trials. Our goal was to test the efficiency of remdesivir in reducing nasopharyngeal viral load and hospitalization length in a real-life setting in patients admitted to a large tertiary centre in Israel.MethodsA total of 142 COVID-19 patients found to have at least three reported SARS-CoV-2 quantitative RT-PCR tests during hospitalization were selected for this study. Of these, 29 patients received remdesivir, while the remaining non-treated 113 patients served as controls.ResultsAmong the tested parameters, the control and remdesivir groups differed significantly only in the intubation rates. Remdesivir treatment did not significantly affect nasopharyngeal viral load, as determined by comparing the differences between the first and last cycle threshold values of the SARS-CoV-2 quantitative RT-PCR tests performed during hospitalization (cycle threshold 7.07 ± 6.85 vs. 7.08 ± 7.27, p 0.977 in the control and treated groups, respectively). Remdesivir treatment shortened hospitalization length by less than a day compared with non-treated controls and by 3.1 days when non-intubated patients from both groups were compared. These differences, however, were not statistically significant, possibly because of the small size of the remdesivir group.DiscussionRemdesivir was not associated with nasopharyngeal viral load changes, but our study had a significant disease severity baseline imbalance and was not powered to detect viral load or clinical differences.  相似文献   
88.
Plate osteosynthesis of the mandibular condyle   总被引:3,自引:0,他引:3  
The aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four different monocortical plating techniques (40 per group) were investigated. Condyles were fractured at a defined location from the incisure to the posterior border. After correct anatomical reduction the fractures were plated, using four different techniques. Osteosynthesis materials used were the delta plate, the trapezoid plate, the dynamic compression plate and double mini-plates. Each group was subjected to linear loading in lateral to medial, medial to lateral, anterior to posterior and posterior to anterior directions by a universal mechanical testing machine TIRAtest 2720. Yield load, yield displacement were measured for the different plates. Statistically significant differences were noted between the fixation groups in all four directions. Rigid internal fixation with double mini plates showed the best stability in all directions except posterior to anterior. In this direction, the delta-plate resisted the highest loads. In the three other directions, the delta plate was second best with data similar to double miniplates but lower in magnitude.  相似文献   
89.
CT beam hardening artifacts near metal hip implants may erroneously enhance or diminish radiotracer uptake following CT attenuation correction (AC) of PET images. An artifact reduction algorithm (ARA) was developed to reduce metal artifacts in CT-based AC-PET. The algorithm employed a Bayes classifier to identify beam-hardening artifacts, followed by a partial correction of the attenuation map. ARA was implemented on phantom and patient 18F-FDG studies using a clinical PET/CT scanner. In phantom studies ARA successfully removed two artifacts of erroneously elevated uptake near a stainless steel hip prosthesis which were depicted in the standard CT-AC PET. ARA has also identified two targets absent on the scanner PET images. Target-to-background ratios were 1.5-3 times higher for ARA-PET than scanner images. In a patient study, metal artifacts were of lower intensity in ARA-PET as compared to standard images. Potentially, ARA may improve detectability of small lesions located near metal hip implants.  相似文献   
90.
Oxygen is one of the most commonly used therapeutic agents. Injudicious use of oxygen at high partial pressures (hyperoxia) for unproven indications, its known toxic potential, and the acknowledged roles of reactive oxygen species in tissue injury led to skepticism regarding its use. A large body of data indicates that hyperoxia exerts an extensive profile of physiologic and pharmacologic effects that improve tissue oxygenation, exert anti-inflammatory and antibacterial effects, and augment tissue repair mechanisms. These data set the rationale for the use of hyperoxia in a list of clinical conditions characterized by tissue hypoxia, infection, and consequential impaired tissue repair. Data on regional hemodynamic effects of hyperoxia and recent compelling evidence on its anti-inflammatory actions incited a surge of interest in the potential therapeutic effects of hyperoxia in myocardial revascularization and protection, in traumatic and nontraumatic ischemicanoxic brain insults, and in prevention of surgical site infections and in alleviation of septic and nonseptic local and systemic inflammatory responses. Although the margin of safety between effective and potentially toxic doses of oxygen is relatively narrow, the ability to carefully control its dose, meticulous adherence to currently accepted therapeutic protocols, and individually tailored treatment regimens make it a cost-effective safe drug.  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