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   3753篇
  免费   180篇
  国内免费   10篇
耳鼻咽喉   30篇
儿科学   260篇
妇产科学   120篇
基础医学   394篇
口腔科学   82篇
临床医学   243篇
内科学   713篇
皮肤病学   189篇
神经病学   273篇
特种医学   67篇
外科学   643篇
综合类   47篇
一般理论   2篇
预防医学   181篇
眼科学   102篇
药学   301篇
中国医学   9篇
肿瘤学   287篇
  2023年   21篇
  2022年   39篇
  2021年   152篇
  2020年   71篇
  2019年   112篇
  2018年   123篇
  2017年   108篇
  2016年   135篇
  2015年   118篇
  2014年   183篇
  2013年   220篇
  2012年   314篇
  2011年   319篇
  2010年   200篇
  2009年   134篇
  2008年   243篇
  2007年   263篇
  2006年   187篇
  2005年   175篇
  2004年   159篇
  2003年   115篇
  2002年   88篇
  2001年   46篇
  2000年   34篇
  1999年   42篇
  1998年   29篇
  1997年   18篇
  1996年   7篇
  1995年   7篇
  1993年   7篇
  1992年   18篇
  1991年   19篇
  1990年   18篇
  1989年   26篇
  1988年   32篇
  1987年   12篇
  1986年   12篇
  1985年   9篇
  1984年   9篇
  1983年   14篇
  1981年   8篇
  1979年   9篇
  1977年   6篇
  1976年   5篇
  1975年   7篇
  1973年   5篇
  1972年   6篇
  1971年   13篇
  1969年   6篇
  1968年   8篇
排序方式: 共有3943条查询结果,搜索用时 625 毫秒
21.
The authors report a 50-year-old man with progressive left hemispheric atrophy, cognitive decline, infrequent seizures, and spells suggestive of complicated migraine. They discuss the association between migraine and cerebral hemiatrophy and suggest that the spectrum of acquired cerebral hemiatrophy may be broader than what has been commonly recognized.  相似文献   
22.
Pulmonary functions were measured in 15 patients with severe chronic anaemia (haemoglobin level < 5 g/dl). The measurements were repeated after correction of anaemia (Hb > 10 g/dl). Twenty age and sex matched, asymptomatic, non-smoker subjects served as controls. There was 80-100% improvement in various lung functions after correction of anaemia. Effort dependent parameters, viz FVC, ERV, IC, MVV were low in anaemic patients which improved with the rise of haemoglobin. The TLCO, DM, VC, KCO were not significantly influenced during anaemic state. FEV1, PEFR, RV/TLC were essentially normal. We conclude that the observed changes produced in lung functions during anaemic state are fully reversible after its correction.  相似文献   
23.
Tympanosclerosis (TS) is a common sequelae of chronic otitis media found in all age groups. Over a period of 3 years, out of 520 surgical cases, 68 (13%) were found to have varying amounts of Tympanosclerotic plaques (TSP) warranting surgical removal. 60% had extension of TSP over the ossicular chain thus affecting its mobility. Deliberate surgical removal of TSP was undertaken for hearing improvement. Systematic and meticulous removal of TSP rather than en-bloc removal has been found to improve the hearing as close to as in, non-tympanosclerotic ear surgery.  相似文献   
24.
We report on 2 patients who were initially suspected to have classic Hodgkin lymphoma because of lymphadenopathy and the presence of Reed-Sternberg-like cells. Both patients had an associated leukemoid reaction (using a threshold leukocyte count of 50 000/microL) and were eventually diagnosed with metastatic carcinoma. Disseminated carcinoma can mimic Hodgkin lymphoma clinically, radiologically, and histologically. Reed-Sternberg-like cells may be found in carcinomas, and they represent a particularly challenging diagnostic pitfall for the unwary. When these cells lead to a suspicion of Hodgkin lymphoma, the presence of a leukemoid reaction should prompt the pathologist to question the diagnosis. Misdiagnosis can be avoided by the use of cytokeratin whenever a leukemoid reaction is present in a suspected case of Hodgkin lymphoma.  相似文献   
25.
AgNORs in endometrial lesions   总被引:1,自引:0,他引:1  
Silver nucleolar organizer region (AgNOR) staining was employed in one hundred specimens of endometrium. These included fifteen normal controls (Proliferative + Secretory endometrium) and eighty five lesions. Endometrial lesions comprised of endometritis (15), endometrial hyperplasia (25) and endometrial carcinoma (45). Three micron thick sections of paraffin embedded tissue were subjected to AgNOR staining as described by Crocker and Smith with a little modification of 0.01% safranin counterstain--The mean AgNOR scores were found to increase steadily from normal to endometritis to endometrial hyperplasia and carcinoma--The observations revealed statistically significant differences in values between atypical hyperplasia and carcinoma also. AgNOR staining and scoring is simple, inexpensive and a useful adjunct to routine histopathology to evaluate endometrial lesions especially to differentiate borderline lesions. Though scores cannot be standardized and fixed for a particular lesion as there are intralaboratory variations.  相似文献   
26.
27.
Fasciolopsiasis is endemic in the far east. In India, there have been a few reports of the infection, prior to the 1990's. We report two cases from Azamgarh district of Uttar Pradesh. Both the cases were from nearby villages where water chestnuts are cultivated. These may be a source of infection. Pigs are commonly observed in these areas and and may be the source of ova. The only missing link is the finding of infected snails. Presence of at least three cases (one reported earlier) in the area indicates the potential for the infection to re-emerge. Further epidemiological studies are needed to analyse the various ecological factors of transmission. Fasciolopsiasis is endemic in China, Taiwan, Vietnam and Thailand. In India, (Fascilopsis buski) infections in man have been reported earlier from Assam, Maharashtra, Tamil Nadu and parts of Uttar Pradesh. However, to the best of our knowledge, no such reports have been made since 1990's. We herewith report two recent cases from district Azamgarh, Uttar Pradesh (U.P.), India. Factors, such as cultivation of water chestnuts, presence of snails as intermediate hosts and pigs as definitive host in this geographical area seem to be suggestive of an endemic focus and thus needs further epidemiological survey for preventive and control measures, at the earliest.  相似文献   
28.
The activity of neurons located in the deep intermediate and adjacent deep layers (hereafter called just deep intermediate layer neurons) of the superior colliculus (SC) in monkeys was recorded during saccades interrupted by electrical stimulation of the brainstem omnipause neuron (OPN) region. The goal of the experiment was to determine if these neurons maintained their discharge during the saccadic interruption, and thus, could potentially provide a memory trace for the intended movement which ends accurately on target in spite of the perturbation. The collicular neurons recorded in the present study were located in the rostral three-fifths of the colliculus. Most of these cells tended to show considerable presaccadic activity during a delayed saccade paradigm, and, therefore, probably overlap with the population of SC cells called buildup neurons or prelude bursters in previous studies. The effect of electrical stimulation in the OPN region (which interrupted ongoing saccades) on the discharge of these neurons was measured by computing the percentage reduction in a cell's activity compared to that present during non-interrupted saccades. During saccade interruption about 70% of deep intermediate layer neurons experienced a major reduction (30% or greater) in their activity, but discharge recovered quickly after the termination of the stimulation as the eyes resumed their movement to finish the saccade on the target. Therefore, the pattern of activity recorded in most of the deep intermediate layer neurons during interrupted saccades qualitatively resembled that previously reported for the saccade-related burst neurons which tend to be located more dorsally in the intermediate layer. In contrast, some of our cells (30%) showed little or no perturbation in their activity caused by the saccade interrupting stimulation. Because all the more dorsally located burst neurons and the majority of our deep intermediate layer neurons show a total or major suppression in their discharge during interrupted saccades, it seems unlikely that the colliculus by itself could maintain an accurate memory of the desired saccadic goal or the remaining dynamic motor error required to account for the accuracy of the resumed movement which occurs following the interruption. However, it remains possible that the smaller proportion of our neurons whose activity was not perturbed during interrupted movements could play a role in the mechanisms underlying saccade accuracy in the interrupted saccade paradigm. Interrupted saccades have longer durations than normal saccades to the same target. Therefore, we investigated whether the discharge of our deeper collicular cells was also necessarily prolonged during interrupted saccades, and, if so, how the prolongation compared to the prolongation of the saccade. Sixty percent of our sample neurons showed a prolongation in discharge that was approximately the same as the prolongation in saccade duration (difference < 15 ms in magnitude). The, observation that temporal discharge in our neurons was perturbed to roughly match saccadic temporal perturbation suggests that dynamic feedback about ongoing saccadic motion is provided to the colliculus, but does not necessarily imply that this structure is the site responsible for the computation of dynamic motor error.  相似文献   
29.
The above discussion on the interaction of aspirin and ACE inhibitors seems to suggest that aspirin in high doses may have adverse interaction with ACE inhibitors in patients with heart failure but the data obtained is not sufficient or conclusive to recommended omission of aspirin in patients with heart failure. This raises a query in the mind of the physician whether to use a combination or not? The role of aspirin in the early period after myocardial infarction is well established so is the role of ACE inhibitors. Hence in patients with myocardial infarction and preserved left ventricular function it would not be wrong to administer combination of ACE inhibitors and aspirin. Albeit at a lower dose. In patients with large myocardial infarction or heart failure, warfarin may be an option but still needs to be documented in large trials. As suggested long term use of aspirin after infarction is still ambiguous and may be harmful in patients with heart failure with its anticedent side effects. But long term benefits of ACE inhibitors in heart failure are well documented. Hence if a choice has to be made whether to discontinue either of the two drugs it would be preferable to stop the aspirin. To answer the issue of use of aspirin in patients with heart failure it would be essential to conduct a double blind randomized trial comparing known anti-thrombotic treatment, aspirin and anti-coagulants on mortality in patients with heart failure, especially caused by coronary artery disease. Such a trial is underway at the present and till the results are available it should be left to clinical judgement of the physician whether to administer aspirin in patients with heart failure after weighing the benefits versus risk.  相似文献   
30.
The natural product quercetin is a flavonoid found in many fruits and vegetables. Previous research has shown that quercetin has antitumor, anti-inflammatory, antiallergic, and antiviral activities. In the present investigation we studied the effect of quercetin on the ability of prostate cancer cell lines with various degrees of aggressive potential to form colonies in vitro. Specifically, we examined the molecular mechanisms underlying this effect, including the expression of cell cycle and tumor suppressor genes as well as oncogenes. We observed that quercetin at concentrations of 25 and 50 μM significantly inhibited the growth of the highly aggressive PC-3 prostate cancer cell line and the moderately aggressive DU-145 prostate cancer cell line, whereas it did not affect colony formation by the poorly aggressive LNCaP prostate cancer cell line or the normal fibroblast cell line BG-9. Using the gene array methodology, we found that quercetin significantly inhibited the expression of specific oncogenes and genes controlling G1, S, G2, and M phases of the cell cycle. Moreover, quercetin reciprocally up-regulated the expression of several tumor suppressor genes. In conclusion, our results demonstrate that the antitumor effects of quercetin directly correlate with the aggressive potential of prostate cancer cells and that the mechanism(s) of quercetin-mediated antitumor effects may involve up-regulation of tumor suppressor genes and reciprocal down-regulation of oncogenes and cell cycle genes. The results of these studies provide a scientific basis for the potential use of flavonoids as nutraceuticals in the chemoprevention of cancer.  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