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   344篇
  免费   14篇
  国内免费   2篇
耳鼻咽喉   4篇
儿科学   8篇
妇产科学   11篇
基础医学   42篇
口腔科学   10篇
临床医学   22篇
内科学   115篇
皮肤病学   13篇
神经病学   23篇
特种医学   4篇
外科学   40篇
预防医学   21篇
眼科学   8篇
药学   30篇
中国医学   3篇
肿瘤学   6篇
  2023年   4篇
  2022年   9篇
  2021年   18篇
  2020年   10篇
  2019年   13篇
  2018年   11篇
  2017年   8篇
  2016年   6篇
  2015年   5篇
  2014年   12篇
  2013年   15篇
  2012年   23篇
  2011年   24篇
  2010年   15篇
  2009年   10篇
  2008年   13篇
  2007年   23篇
  2006年   27篇
  2005年   32篇
  2004年   22篇
  2003年   15篇
  2002年   16篇
  2001年   1篇
  2000年   4篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1993年   2篇
  1991年   1篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1982年   2篇
  1975年   1篇
  1974年   1篇
  1973年   3篇
  1971年   1篇
  1965年   3篇
排序方式: 共有360条查询结果,搜索用时 453 毫秒
1.
2.
We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences to generate a duplex PCR assay for the simultaneous detection of Trypanosoma cruzi and Trypanosoma rangeli in experimentally and naturally infected triatomine (Reduviid) bugs and in infected human subjects. The assay was species specific and was capable of detecting 1/20th of T. cruzi and 1/4th of T. rangeli cell equivalents without complementary hybridization. In addition, the PCR-based assay was robust enough for direct application to difficult biological samples such as Reduviid feces or guts and was capable of recognizing all T. cruzi and T. rangeli strains and lineages. Because the assay primers amplify entirely different target sequences, no reaction interference was observed, facilitating future adaptation of this assay to an automated format.  相似文献   
3.
The actinomycete Rhodococcus equi is an important pathogen of horses and an emerging opportunistic pathogen of humans. Identification of R. equi by classical bacteriological techniques is sometimes difficult, and misclassification of an isolate is not uncommon. We report here on a specific PCR assay for the rapid and reliable identification of R. equi. It is based on the amplification of a fragment of the choE gene encoding cholesterol oxidase. The choE-based PCR was assessed by using a panel of strains comprising 132 isolates from different sources and of different geographical origins, all initially identified biochemically as R. equi, and 30 isolates of representative non-R. equi actinomycete species, including cholesterol oxidase producers. The expected 959-bp amplicon was observed only with R. equi isolates, as confirmed by sequencing of a variable region of the 16S RNA gene from a random sample of 20 PCR-positive isolates. All R. equi isolates gave a positive choE-based PCR result, which correlated with a high degree of conservation of the choE gene. Three of the 132 strains originally identified as R. equi were negative for the choE gene, and subsequent analysis of their 16S RNA gene sequences confirmed that they belonged to other bacterial species (Dietzia maris, Mycobacterium peregrinum, and Staphylococcus epidermidis). All non-R. equi isolates were negative by the choE-based PCR. ATCC 21387, the only known isolate of Brevibacterium sterolicum, gave a 959-bp amplicon whose DNA sequence was virtually identical to that of R. equi choE. Comparison of the 16S RNA genes indicated that ATCC 21387 should be considered an R. equi isolate.  相似文献   
4.
AIMS: The present study was attempted to determine whether LV midwall mechanics yielded different conclusions about LV systolic function than the assessment of endocardial LV mechanics by echocardiography in spontaneously hypertensive rats (SHR). METHODS AND RESULTS: Thirty-six (18 Wistar normotensive (W), 18 [SHR]) anesthetized rats were studied with two-dimensional directed M-mode echocardiogram to analyze LV structure (LV diameter, left ventricular wall thickness and LV mass [LVM]) and LV function (endocardial shortening [ES] and midwall shortening [MS]). Measurements were made from three consecutive cardiac cycles on the M-mode tracings. There was no significant difference in LV dimension. LVM was higher in SHR (SHR: 595 +/- 111 mg, W: 413 +/- 83 mg--p < 0.01). ES was higher in SHR (SHR: 64.1 +/- 6%, w: 58.2 +/- 4%--p < 0.01), whereas no significant difference was found in MS (SHR: 24 +/- 4%, W: 27.6 +/- 4%--ns). Twelve of 18 (66%) SHR showed endocardial shortening higher than normally predicted, compared with 3/18 (16%) with observed enhanced MS (p < 0.01). CONCLUSION: These results suggest that the analysis of midwall mechanics by echo allows us to better understand the LV performance in SHR and that the exaggerated endocardial motion could not represent a really supernormal systolic performance.  相似文献   
5.
Early Miocene sloths are represented by a diversity of forms ranging from 38 to 95 kg, being registered mainly from Santacrucian Age deposits in southern‐most shores of Patagonia, Argentina. Their postcranial skeleton differs markedly in shape from those of their closest living relatives (arboreal forms of less than 10 kg), Bradypus and Choloepus. In order to gain insight on functional properties of the Santacrucian sloths forelimb, musculature was reconstructed and a comparative, qualitative morphofunctional analysis was performed, allowing proposing hypotheses about biological role of the limb in substrate preferences, and locomotor strategies. The anatomy of the forelimb of Santacrucian sloths resembles more closely extant anteaters such as Tamandua and Myrmecophaga, due to the robustness of the elements, development of features related to attachment of ligaments and muscles, and conservative, pentadactylous, and strong‐clawed manus. The reconstructed forelimb musculature was very well developed and resembles that of extant Pilosa (especially anteaters), although retaining the basic muscular configuration of generalized mammals. This musculature allowed application of powerful forces, especially in adduction of the forelimb, flexion and extension of the antebrachium, and manual prehension. These functional properties are congruent with both climbing and digging activities, and provide support for proposed Santacrucian sloths as good climbing mammals, possibly arboreal or semiarboreal, being also capable diggers. Their climbing strategies were limited, thus these forms relied mainly on great muscular strength and curved claws of the manus to move cautiously on branches. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
6.
7.
This paper presents a uniquely designed device combining the hole-drilling technique with two optical systems based on the PhotoStress and digital image correlation (DIC) method, where the digital image correlation system moves with the cutting tool. The authors aimed to verify whether the accuracy of the drilled hole according to ASTM E837-13a standard and the positioning accuracy of the device were sufficient to achieve accurate results. The experimental testing was performed on a thin specimen made from strain sensitive coating PS-1D, which allowed comparison of the results obtained by both methods. Although application of the PhotoStress method allows analysis of the strains at the edge of the cut hole, it requires a lot of experimenter’s practical skills to assess the results correctly. On the other hand, the DIC method allows digital processing of the measured data. However, the problem is not only to determine the data at the edge of the hole, the results also significantly depend on the smoothing levels used. The quantitative comparison of the results obtained was performed using finite element analysis.  相似文献   
8.
Summary The possible influence of qualitative dietary changes on carbohydrate tolerance and plasma lipid levels of non insulin-dependent diabetics was studied in 5 maturity-onset diabetics of normal weight who remained stabilized with 5 to 10 mg glibenclamide. Each patient was submitted to 4 isocaloric qualitatively different diets: standard, high carbohydrate, high fat, and high protein. Each diet was administered for 30 consecutive days in random order. Apart from assessing metabolic control, an oral glucose tolerance test (40 g/m2 body surface area) was performed in the morning, at the end of each period. Blood was collected at 0, 60, 120, and 180 min after starting glucose ingestion, for blood glucose and plasma FFA determinations. Fasting total lipids, triglycerides, lipoalbumins, and α- and β-lipoproteins, and 24-h urinary urea were also investigated. The findings did not disclose any differences in carbohydrate tolerance after the various diets. The drop in FFA levels following an oral glucose load was greatest after the high protein diet. Fasting total lipids were lowest after the high fat and high protein diets. Triglycerides fell after the high fat diet. The remaining parameters showed less significant variations. Although no differences were observed in carbohydrate tolerance, the conclusion is that relative carbohydrate restriction together with sufficient protein supply might be most beneficial for non insulin-dependent diabetics.  相似文献   
9.
Introduction and objectivesAsian desert dust has recently been recognized as a trigger for acute myocardial infarction. The inflow of dust from the Sahara into Spain impairs air quality due to an increase in particulate matter concentrations in the ambient air. The aim of the present study was to elucidate whether Saharan dust events are associated with the incidence of acute coronary syndrome (ACS) in patients living near North Africa, the major global dust source.MethodsWe prospectively collected data on hospitalizations due to ACS in 2416 consecutive patients from a tertiary care hospital (Canary Islands, Spain) from December 2012 to December 2017. Concentrations of particulate matter with an aerodynamic diameter 10 microns or smaller (PM10) and reactive gases were measured in the European Air Quality Network implemented in the Canary Islands. We applied the time-stratified case crossover design using conditional Poisson regression models to estimate the impact of PM10 Saharan dust events on the incidence of ACS.ResultsThe occurrence of Saharan dust events observed 0 to 5 days before the onset of ACS was not significantly associated with the incidence of ACS. Incidence rate ratios (IRR) of PM10 levels 1, 2, 3, 4 and 5 days before ACS onset (for changes in 10 μg/m3) were 1.27 (95%CI, 0.87-1.85), 0.92 (95%CI, 0.84-1.01), 0.74 (95%CI, 0.45-1.22), 0.98 (95%CI, 0.87-1.11), and 0.95 (95%CI, 0.84-1.06), respectively.ConclusionsExposure to Saharan desert dust is unlikely to be associated with the incidence of ACS.  相似文献   
10.
Two samples of participants with typical development (TD) and high functioning autism performed an imitation task where the goal was of high or low salience, and where the modeled action complied with or was contrary to the end-state comfort (ESC) effect. Imitation was affected by the ESC effect in both groups, and participants with autism reproduced high salient goals as frequently as did participants with TD, but they reproduced less of the low salient goals. Participants with autism showed a reduced tendency to reproduce those actions which were relatively inefficient to reach the goals. The results are discussed in terms of either a relative imbalance between emulation and mimicry in autism, or a reduced tendency to overimitate.  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