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   5275篇
  免费   301篇
  国内免费   29篇
耳鼻咽喉   28篇
儿科学   192篇
妇产科学   126篇
基础医学   614篇
口腔科学   153篇
临床医学   391篇
内科学   1738篇
皮肤病学   66篇
神经病学   452篇
特种医学   97篇
外科学   604篇
综合类   16篇
一般理论   1篇
预防医学   220篇
眼科学   27篇
药学   388篇
中国医学   7篇
肿瘤学   485篇
  2023年   31篇
  2022年   58篇
  2021年   136篇
  2020年   58篇
  2019年   125篇
  2018年   130篇
  2017年   102篇
  2016年   111篇
  2015年   106篇
  2014年   168篇
  2013年   236篇
  2012年   295篇
  2011年   284篇
  2010年   163篇
  2009年   155篇
  2008年   235篇
  2007年   304篇
  2006年   290篇
  2005年   297篇
  2004年   234篇
  2003年   215篇
  2002年   218篇
  2001年   167篇
  2000年   169篇
  1999年   154篇
  1998年   46篇
  1997年   47篇
  1996年   41篇
  1995年   43篇
  1994年   37篇
  1993年   30篇
  1992年   99篇
  1991年   61篇
  1990年   77篇
  1989年   63篇
  1988年   58篇
  1987年   66篇
  1986年   50篇
  1985年   53篇
  1984年   44篇
  1983年   53篇
  1982年   20篇
  1979年   26篇
  1978年   20篇
  1976年   17篇
  1975年   25篇
  1974年   28篇
  1971年   16篇
  1970年   20篇
  1968年   16篇
排序方式: 共有5605条查询结果,搜索用时 0 毫秒
41.
The authors describe the pathological changes in the vascular structures of the ciliary body occuring in diabetes mellitus. The lesions consist of a quantitative reduction in the number of vessels and in modifications of diameter and arborisation. Changes include sectoral thinning, isolated and grouped aneuryms and marked tortuosity. These findings are thought to be constant in the diabetic patient and are probably involved in the various aspects of diabetic eye disease affecting other structures besides the ciliary body. The group of vascular changes in the ciliary body in diabetes may aptly be termed "diabetic ciliopathy".  相似文献   
42.
The possibility of a preferential distribution of projections from the preoptic-suprachiasmatic region (POA-Sch) to the median eminence in the male rat was studied using autoradiographic and computer procedures. A cocktail of [3H]leucine-[3H]proline was injected into the POA-Sch. Animals were killed after either 1, 4, or 24 h of incorporation time (IT). The number of silver grains per 25-micron square was counted throughout the median eminence. Squares with silver grain densities at or above the 75 percentile of the population for any given IT group were labeled as "concentrating areas." The distribution of these concentrating areas in median eminence tissue was analyzed utilizing univariate procedures. Visual inspection of the distribution of silver grain densities in a rostrocaudal fashion indicated the likelihood of uneven distribution; however, these differences were not statistically significant. In the dorsoventral plane, results indicated that the highest silver grain density was at 50 to 75 micron from the floor of the 3rd ventricle. Such distribution was apparent both ipsi- and contralateral to the injection site, but was greater on the ipsilateral side.  相似文献   
43.
Two females mother and daughter, were affected by a neuromuscular disorder, characterized by slow progression, humeroperoneal weakness and wasting, limited neck flexion, elbow and ankle joint contractures, cardiopathy and myopathic pattern on EMG. Muscle histology and histochemistry showed type I fiber atrophy and predominance in both. Cardiac abnormalities, in the first case, were suggestive of a hypertrophic cardiomyopathy while in the second hypotension and chronic bradycardia were present.Neurological signs, EMG and morphology seemed to point to a genetic variant of the form of dystrophy named Emergy-Dreifuss disease.The mode of transmission and cardiac abnormalities, however, raise the problem of variability even in this well-defined, usually X-linked, disorder.
Sommario Questa è la prima descrizione di madre e figlia affette da una infrequente malattia muscolare, caratterizzata da progressione lenta, ipostenia con atrofia a distribuzione omero-peroneale, presenza di contratture articolari, cardiopatia e pattern miopatico dell'EMG.Istologia e istochimica muscolare hanno mostrato in entrambi i soggetti atrofia e predominanza delle fibre del I tipo. Le anormalità cardiologiche rilevate nel 1° caso, erano a favore di una cardiomiopatia ipertrofica, mentre nel secondo caso erano presenti ipotensione e bradicardia.Segni neurologici, elettromiografici, reperti istologici ed istochimici sembrano configurare nelle nostre pazienti una variante genetica della forma di distrofia muscolare chiamata Emery-Dreifuss disease. Tuttavia, la modalità di trasmissione e il tipo delle anormalità cardiologiche, diverse nelle due pazienti, sollevano il problema di variabilità fenotipiche, anche in entità clinico-genetiche usualmente ben definite quali la malattia di Emery-Dreifuss.
  相似文献   
44.
At least two fundamental requirements must subsist for every stereotaxic radiotherapy treatment: 1) a capacity to administer extremely high doses of radiation to small areas which have been precisely defined in three dimensions; 2) the presence of a steep gradient between adjacent isodose curves so that damage to the tissues close to the target may be reduced to the minimum. The authors have built a special stereotaxic device for the fixing of the head of the patient (together with the chosen intracranial target), once the indispensable neuroradiological evaluations and bioptic controls have been effected, at the isocenter of a linear accelerator (Varian Clinac 4). Once the dimensions of the collimator have been chosen in accordance with the volume and the three dimensional conformation of the target and the dose to be administered has been decided upon in accordance with the histological nature of the lesion, both the linear accelerator and the patient are rotated about the isocenter of the therapy unit. It this way it is possible to reach extremely high dosages with very steep isodose gradients, centered exclusively upon the target ("gamma knife"). The procedure employed is described in full. The dosimetric evaluations which preceded the use of the set-up in clinical practice are illustrated as well. The advantages that this technique offers when compared with interstitial brachytherapy and/or Leksell's radiosurgical procedures are stressed. The described procedure, which is entirely bloodless and thus applicable also to high vascularized lesions, has so far been used in a limited series of cases.  相似文献   
45.
46.
Polyphenols are a group of phytochemicals with potential health-promoting effects. They are classified as flavonoid (flavonols, flavanols, flavones, flavanones, isoflavones, and anthocyanins) and non-flavonoid molecules (phenolic acids, hydroxycinnamic acids, lignans, stilbenes, and tannins). Although an increasing number of trials have shown a correlation among polyphenol consumption and a reduction in risk factors for chronic diseases, discrepancies in explaining their positive effects have been found in terms of the bioavailability. In fact, polyphenols show a low bioavailability due to several factors: interaction with the food matrix, the metabolic processes mediated by the liver (phase I and II metabolism), intestine and microbiota. On the other hand, the biological activities of phenol compounds may be mediated by their metabolites, which are produced in vivo, and recent studies have confirmed that these molecules may have antioxidant and anti-phlogistic properties. This review discusses the studies performed in vivo, which consider the polyphenol bioavailability and their different food sources. Factors influencing the biological effects of the main classes of polyphenols are also considered.  相似文献   
47.
Introduction and objectivesThe goals of transurethral resection of a bladder tumor (TUR) are to completely resect the lesions and to make a correct diagnosis in order to adequately stage the patient. It is well known that the presence of detrusor muscle in the specimen is a prerequisite to minimize the risk of under staging.Persistent disease after resection of bladder tumors is not uncommon and is the reason why the European Guidelines recommended a re-TUR for all T1 tumors. It was recently published that when there is muscle in the specimen, re-TUR does not influence progression or cancer specific survival.We present here the patient and tumor factors that may influence the presence of residual disease at re-TUR.Material and methodsIn our retrospective cohort of 2451 primary T1G3 patients initially treated with BCG, pathology results for 934 patients (38.1%) who underwent re-TUR are available. 74% had multifocal tumors, 20% of tumors were more than 3 cm in diameter and 26% had concomitant CIS.In this subgroup of patients who underwent re-TUR, there was no residual disease in 267 patients (29%) and residual disease in 667 patients (71%): Ta in 378 (40%) and T1 in 289 (31%) patients. Age, gender, tumor status (primary/recurrent), previous intravesical therapy, tumor size, tumor multi-focality, presence of concomitant CIS, and muscle in the specimen were analyzed in order to evaluate risk factors of residual disease at re-TUR, both in univariate analyses and multivariate logistic regressions.ResultsThe following were not risk factors for residual disease: age, gender, tumor status and previous intravesical chemotherapy. The following were univariate risk factors for presence of residual disease: no muscle in TUR, multiple tumors, tumors > 3 cm, and presence of concomitant CIS. Due to the correlation between tumor multi-focality and tumor size, the multivariate model retained either the number of tumors or the tumor diameter (but not both), p < 0.001. The presence of muscle in the specimen was no longer significant, while the presence of CIS only remained significant in the model with tumor size, p < 0.001.ConclusionsThe most significant factors for a higher risk of residual disease at re-TUR in T1G3 patients are multifocal tumors and tumors more than 3 cm. Patients with concomitant CIS and those without muscle in the specimen also have a higher risk of residual disease.  相似文献   
48.
Pretreatment of human peripheral blood lymphocytes (PBL) with cisplatin (CDDP) before in vitro culture with interleukin-2 (IL-2) inhibited the generation of lymphokine-activated killer (LAK) cells and strongly inhibited proliferation. This inhibition was dose dependent, was significant only at concentrations greater than 6 microM, and it required exposure to the drug for more than 1 hour. This period of IL-2 unresponsiveness was maximum at 6 hours, but was spontaneously recovered within 24-48 hours and was more rapidly restored by increasing dosages of IL-2. Because inhibition of the generation of LAK cells by CDDP was observed only at relatively high levels of exposure to the drug (greater than 6 microM for greater than 1 hr), it was important that we explore the in vivo significance of these findings. The peripheral blood lymphocytes from patients bearing ovarian adenocarcinoma collected 1 hour after an iv infusion of 50 mg of CDDP/m2 were not inhibited, compared with those collected immediately before therapy. Relatively high levels of exposure to CDDP are required for inhibition of the generation of new cytotoxic effectors, most likely because of its antiproliferative effect. These results may bear relevance to approaches involving the combined use of CDDP and IL-2-LAK.  相似文献   
49.
50.
Long, interlaminar, astroglial processes and its patterned organization in the striate cortex of adult primates was previously described. Loss of visual input following bilateral retinal detachment and degeneration in an adult Cebus apella monkey resulted three months later in reduction of interlaminar processes immunoreactive to Glial Fibrillary Acid Protein antibody, loss of the honeycomb-like pattern normally present in tangential sections, and loss of high density patches of terminal segments of those processes in the opercular striate. These results further indicate the highly interactive nature of neuron-glial cerebral cortex architecture, and the dynamic regulation of astroglial interlaminar processes.  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