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   1070篇
  免费   52篇
  国内免费   1篇
耳鼻咽喉   26篇
儿科学   60篇
妇产科学   41篇
基础医学   110篇
口腔科学   13篇
临床医学   101篇
内科学   211篇
皮肤病学   4篇
神经病学   201篇
特种医学   77篇
外科学   100篇
综合类   2篇
预防医学   34篇
眼科学   6篇
药学   51篇
中国医学   3篇
肿瘤学   83篇
  2023年   12篇
  2022年   12篇
  2021年   28篇
  2020年   18篇
  2019年   30篇
  2018年   37篇
  2017年   24篇
  2016年   26篇
  2015年   31篇
  2014年   34篇
  2013年   57篇
  2012年   76篇
  2011年   64篇
  2010年   45篇
  2009年   38篇
  2008年   68篇
  2007年   68篇
  2006年   66篇
  2005年   61篇
  2004年   57篇
  2003年   55篇
  2002年   34篇
  2001年   18篇
  2000年   16篇
  1999年   13篇
  1998年   7篇
  1997年   6篇
  1996年   5篇
  1994年   10篇
  1993年   3篇
  1992年   8篇
  1991年   3篇
  1990年   6篇
  1989年   7篇
  1988年   6篇
  1987年   7篇
  1986年   4篇
  1985年   5篇
  1984年   6篇
  1983年   3篇
  1979年   4篇
  1976年   2篇
  1975年   4篇
  1974年   4篇
  1973年   5篇
  1972年   2篇
  1970年   5篇
  1969年   4篇
  1968年   3篇
  1967年   4篇
排序方式: 共有1123条查询结果,搜索用时 15 毫秒
1.
A case of multiple hydatid cysts of the brain is reported. Computed tomographic and magnetic resonance imaging scanning revealed a thick and calcified pericystium. These findings allowed appropriate surgical planning, with a marked recovery of the neurological deficits and absence of relapse in the follow-up period.  相似文献   
2.
PURPOSETo define MR accuracy in the evaluation of the T stages of tumors of the tongue and floor of the mouth.METHODSFifty-two patients affected by squamous cell carcinoma were studied with a superconductive system at 1.5 T. The study was performed with spin-echo T1- and T2-weighted images before contrast and short spin-echo T1-weighted and gradient-echo sequences after gadopentetate dimeglumine administration. The results obtained with MR were compared with pathologic data.RESULTSGood correlation of T stages (TNM system) was obtained in 45 of 52 cases. MR did not show four superficial lesions. In one case, infiltration of the cortical bone of the mandible was not demonstrated (MR, T2; pathologic, T4), and in another the lesion was classified as T2 instead of T3, as it was pathologically. One lesion was classified as T4 on MR because of infiltration of the alveolar ridge but was classified as T2 at surgery. In 46 patients who underwent surgery, the accuracy of MR was excellent for predicting the relationship of tumor to midline and oral floor musculature. The results obtained with gadopentetate dimeglumine were better than those obtained in noncontrast studies in 32 (62%) of 53 cases.CONCLUSIONMR showed high accuracy in the study of tumors of the tongue and floor of the mouth.  相似文献   
3.
Intima formation in vessels, spontaneous or experimentally induced, is generally characterized by the presence of longitudinally orientated smooth muscle cells (LSMC). During an experiment of neo-intima induction in carotid arteries in rabbits, by application of a nonconstrictive silastic cuff, a study was performed to investigate the presence of LSMC in the systemic and pulmonary circulations, in both elastic and muscular arteries. Three patterns could be distinguished: intimai cushions in muscular arteries, single or small groups of LSMC in the intima in elastic and larger muscular arteries, and intra-medially located layers or columns of LSMC in the aorta, the pulmonary artery, at the bifurcation of the aorta and around orifices of branches. In order to understand this peculiar orientation a biomechanical approach was used: this showed that near the lumen the circumferential stress is 4.5 times higher than the longitudinal. Because the cell surface of the smooth muscle cells exposed to this stress per unit vessel length is much less in the longitudinal than in the circular direction we conclude that the LSMC align in the direction which allows them to cope most effectively with the mechanical stresses.  相似文献   
4.
Antigen-specific T cell suppression by human CD4+CD25+ regulatory T cells   总被引:19,自引:0,他引:19  
Anergic/suppressive CD4+CD25+ T cells have been proposed to play an important role in the maintenance of peripheral tolerance. Here we demonstrate that in humans these cells suppress proliferation to self antigens, but also to dietary and foreign antigens. The suppressive CD4+CD25+ T cells display a broad usage of the T cell receptor Vbeta repertoire,suggesting that they recognize a wide variety of antigens. They reside in the primed/memory CD4+CD45RO+CD45RB(low) subset and have short telomeres, indicating that these cells have the phenotype of highly differentiated CD4+ T cells that have experienced repeated episodes of antigen-specific stimulation in vivo. This suggests that anergic/suppressive CD4+CD25+ T cells may be generated in the periphery as a consequence of repeated antigenic encounter. This is supported by the observation that highly differentiated CD4+T cells can be induced to become anergic/suppressive when stimulated by antigen presented by non-professional antigen-presenting cells. We suggest that besides being generated in the thymus, CD4+CD25+ regulatory T cells may also be generated in the periphery. This would provide a mechanism for the generation of regulatory cells that induce tolerance to a wide array of antigens that may not be encountered in the thymus.  相似文献   
5.
The predictive value of a comprehensive model with personality characteristics, stressor related cognitions, coping and social support was tested in a sample of 187 nonpregnant women. The emotional response to the unsuccessful treatment was predicted out of vulnerability factors assessed before the start of the treatment. The results indicated the importance of neuroticism as a vulnerability factor in emotional response to a severe stressor. They also underlined the importance of helplessness and marital dissatisfaction as additional risk factors, and acceptance and perceived social support as additional protective factors, in the development of anxiety and depression after a failed fertility treatment. From clinical point of view, these results suggest fertility-related cognitions and social support should receive attention when counselling women undergoing IVF or ICSI treatment.  相似文献   
6.
Various drugs were tested as inhibitors of diamine oxidase on the basis of chemical relationships to the enzyme substrates.It was found that serotonine tryptamine and phenformin are good competitive inhibitors while cimetidine and pheniprazine are non-competitive inhibitors. Other antihistaminic drugs like promethazine are less powerful inhibitors.  相似文献   
7.
Somatotyping is an effective technique for the study of anthropometric variations and body composition in elderly subjects, even though it has not often been used in this field. The present study was conducted on a sample of 280 healthy Sardinians (134 men and 146 women) of age 60-89 years, subdivided into three age classes (60-69 years; 70-79 years; and 80-89 years). Somatotypes were computed according to Carter and Heath (Somatotyping-Development and Applications. Cambridge, England: Cambridge University Press; 1990). The results show a dominance of the endo- and mesomorphic components in the elderly subjects, with less development of ectomorphy than in younger individuals. In a comparison with other populations, our sample shows strong development of endomorphy and especially of mesomorphy, while ectomorphy values are generally low. Age-related variations are significant in both sexes and consist in a progressive reduction of the endomorphic component, particularly in the 80-89-year class (endomorphy in the three age classes: 6.4, 6.1, and 5.3 in men; 8.1, 7.8, and 6.8 in women). The mesomorphic component is characterized by stability (age variations: 6.4, 6.4, and 5.9 in men; 6.3, 6.4, and 6.3 in women) and the ectomorphic component by a slight increase (age variations: 0.5, 0.6, and 0.8 in men; 0.4, 0.3, and 0.5 in women). Sex differences are significant and especially large for the endomorphic component, with generally higher values in women. The sexual dimorphism tends to decrease with age. The results are discussed with regard to the biology of aging, with emphasis on the potential application of somatotype to studies of the elderly population.  相似文献   
8.
Summary The contamination of autologous marrow with clonogenic tumor cells has been the main argument against ABMT in acute leukemia.In a preclinical study we evaluated an active cyclophosphamide derivative named ASTA Z 7557. We observed that the toxic effect of this drug on CFU-GM growth was dependent on nucleated cell concentration as well as on red blood cell contamination. The potency of the drug was in close relationship with the incubation temperature.The growth of leukemic CFU was inhibited with an ASTA Z dose higher than 30 g/ml. In our system, beyond 40 g/ml more than 95% of committed stem cells are destroyed.Fifteen patients had autotransplant because of AML for 10 patients and because of ALL for 5 patients (4 patients were grafted in relapse and 11 patients in remission).We demonstrated that the marrow take was possible although the inoculum is CFU-GM depleted.Five of the 10 AML patients are alive and remain disease-free at 45 +, 65 +, 190 +, 345+ and 570 + days from ABMT without any maintenance treatment. Four of the 5 ALL patients are alive, three of them in complete remission (404+, 110+, 250+ days).The number of patients reported in this clinical study was relatively small and more cases should be evaluated to be conclusive. Nevertheless the feasibility of chemopurified ABMT was demonstrated.  相似文献   
9.
10.
The thienobenzodiazepine derivative etizolam (CAS 40054-69-1, 6-(o-chlorophenyl)-8-ethyl-1-methyl-4H-s-triazolo-(3,4-c)thienol(1 ,4) diazepine) is a potent anxiolytic with a pharmacological profile similar to that of classical benzodiazepines. In order to rationalize the therapeutic use of etizolam, its pharmacodynamics properties on GABAA receptors were investigated by a comparative study with other ligands on human recombinant GABAA as well as rat brain native receptors. Etizolam inhibited in a concentration-dependent manner [3H]flunitrazepam (CAS 1622-62-4) binding to rat cortical membranes, with an affinity of 4.5 nmol/l greater than that of alprazolam (CAS 28981-97-7) (7.9 nmol/l). Ethizolam enhanced GABA-induced Cl- currents in oocytes expressing human cloned GABAA receptors. With alpha 1 beta 2 gamma 2S subunit combination, etizolam produced a 73% increase in GABA-induced currents with an EC50 of 92 nmol/l. At the same receptor type, alprazolam showed a higher degree of potentiation and potency (98%, EC50 56 nmol/l). At alpha 2 beta 2 gamma 2S or alpha 3 beta 2 gamma 2S subunit constructs, the effects of etizolam were similar to those of alprazolam. Flumazenil (CAS 78755-81-4) completely blocked both etizolam and alprazolam effects on GABA-induced currents. Etizolam, administered i.p., was uneffective in changing ex vivo t-[35S]butylbicyclophosphorothionate ([35S]-TBPS) binding to rat cerebral cortex, whereas alprazolam and abecarnil (CAS 111841-85-1) significantly reduced this parameter. However, etizolam similarly to abecarnil and alprazolam, antagonized isoniazid-induced increase (61%) in [35S]-TBPS binding to rat cortical membranes. Further, etizolam inhibited in a dose-dependent manner basal acetylcholine release from both hippocampus and prefrontal cortex, and reversed foot-shock-induced increase of basal acetylcholine release to a control level. Altogether, these results suggest that etizolam may have a reduced intrinsic activity, at least at specific subpopulations of GABAA receptors. This property, together with the pharmacokinetic indication of a short-acting drug, may characterize etizolam as a ligand endowed with less side-effects typical of full agonits such as diazepam (CAS 439-14-5) and alprazolam. Finally, given its marked efficacy under conditions of GABAergic deficit, etizolam may represent a possible drug of choice with reduced liability to produce tolerance and dependence after long-term treatment of anxiety and stress syndromes.  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