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   3287087篇
  免费   232435篇
  国内免费   5794篇
耳鼻咽喉   47146篇
儿科学   104250篇
妇产科学   90938篇
基础医学   477749篇
口腔科学   93596篇
临床医学   292482篇
内科学   632028篇
皮肤病学   73549篇
神经病学   259696篇
特种医学   125213篇
外国民族医学   894篇
外科学   499324篇
综合类   71142篇
现状与发展   16篇
一般理论   1189篇
预防医学   248295篇
眼科学   78061篇
药学   246126篇
  15篇
中国医学   6806篇
肿瘤学   176801篇
  2018年   34490篇
  2017年   26354篇
  2016年   29480篇
  2015年   33130篇
  2014年   46746篇
  2013年   70809篇
  2012年   96090篇
  2011年   102250篇
  2010年   60922篇
  2009年   57933篇
  2008年   96738篇
  2007年   104017篇
  2006年   104863篇
  2005年   101902篇
  2004年   97900篇
  2003年   94639篇
  2002年   92077篇
  2001年   148902篇
  2000年   152791篇
  1999年   129000篇
  1998年   37133篇
  1997年   32789篇
  1996年   32450篇
  1995年   30775篇
  1994年   28470篇
  1993年   26828篇
  1992年   100507篇
  1991年   98088篇
  1990年   95955篇
  1989年   92904篇
  1988年   85921篇
  1987年   84504篇
  1986年   79858篇
  1985年   76596篇
  1984年   57040篇
  1983年   48635篇
  1982年   29102篇
  1981年   26252篇
  1979年   53442篇
  1978年   38300篇
  1977年   32491篇
  1976年   30466篇
  1975年   33620篇
  1974年   40138篇
  1973年   38531篇
  1972年   36487篇
  1971年   34434篇
  1970年   32152篇
  1969年   30728篇
  1968年   28418篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A consecutive series of patients (1978–1981) comprising all patients with acute leukaemia from a population of 475000 inhabitants was reviewed. Thus, 94 patients were diagnosed as having acute leukaemia. No patients were lost from follow-up. The incidence figures of ALL and AML differed significantly from those of Sweden as a whole. 9 patients were < 15 years old. The median age of adult patients was 64 years, 60.8% being ≥ 60 years old. Of adult patients with AML, 20% had a preleukaemic history (chronic myeloproliferative disorders, myelodysplastic syndromes and others). None of 6 patients with leukaemia as a metamorphosis of a chronic myeloproliferative disorder achieved a complete remission. The overall remission rate of the remaining adult patients was 25%. Treated patients, 15–39 years old, with AML without any preleukaemic history, had a complete remission rate of 80% compared to 12% for patients ≥ 60 years old with the same diagnosis. Of 60 patients with ‘primary’ AML, 14 were not treated, mainly because of advanced age and complicating diseases. Most of these patients died within a week of admission.  相似文献   
993.
994.
995.
Hypersensitivity reactions may occur during antituberculous chemotherapy. Severe reactions are rare, and in the three years 1983-86 during which we have both worked in Africa managing large numbers of patients with tuberculosis we only saw one or two cases with severe and generalised cutaneous hypersensitivity. In the last 12 months, however, there have been a number of cases with severe Stevens-Johnson syndrome which developed during antituberculous chemotherapy and has invariably been associated with seropositivity to HIV (human immunodeficiency virus).  相似文献   
996.
Hemorrhage following mandibular osteotomies: a report of 21 cases   总被引:1,自引:0,他引:1  
Hemorrhage associated with mandibular osteotomies, especially to the extent that it becomes life threatening, is a rare occurrence and its risk is less than that following maxillary orthognathic surgery. Twenty-one cases of significant bleeding following mandibular sagittal split ramus osteotomies, vertical and oblique ramus osteotomies, and genioplasties are presented. Life-threatening hemorrhage associated with mandibular osteotomies is primarily an intraoperative problem and the incidence of major postoperative and recurrent hemorrhage is not as great as following maxillary osteotomies. Suggestions for the avoidance and treatment of these bleeding complications are discussed.  相似文献   
997.
A new method for producing temporary complete cerebral ischemia in rats   总被引:2,自引:0,他引:2  
A new model of temporary complete cerebral ischemia was developed and tested in 64 rats. With use of microsurgical techniques, both pterygopalatine and external carotid arteries were occluded and the basilar artery was coagulated to reduce potential collateral CBF during ischemia. After this preliminary five-vessel occlusion, temporary global ischemia was induced by occluding the common carotid arteries (CCAs) with microclips. To validate the method, CBF was measured autoradiographically in 24 anatomical regions at death after 5 min of ischemia or after 15 min of ischemia followed by 5 min of reperfusion. Mean arterial blood pressure and arterial blood gases remained stable under controlled endotracheal ventilation and anesthesia (halothane, 70% N2O, and 30% O2) throughout the CBF experiments, except for a 10-15% increase in mean arterial blood pressure for 1-5 min after bilateral CCA occlusion. After the initial five-vessel occlusion, the EEG did not change, and local CBF levels were comparable to those in anesthetized non-surgical controls. When the CCAs were occluded, the EEG flattened rapidly; after 5 min of ischemia, autoradiography showed no detectable blood flow in the forebrain and cerebellum. The local CBF levels measured after 15 min of temporary global ischemia and 5 min of reperfusion demonstrated relatively homogeneous postischemic hyperperfusion; only two of eight rats had several 1- to 3-mm areas of no-reflow. Survival studies showed increasing motor impairment after 10, 15, 30, and 60 min of temporary CCA occlusion. Ischemic neuronal damage was observed histologically in the hippocampus and basal ganglia 24 h after 10 min of temporary ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
998.
We introduce the concept of the metabolic centroid spectrum as the feature space to characterize the distribution of metabolic activity in three-dimensional brains. The method computes the metabolic centroid of a brain subvolume for each increment of metabolic activity occurring in the whole brain. The result is the metabolic spectral signature, a continuous three-dimensional curve whose shape reflects the distribution of metabolic rates in the brain. The method's sensitivity to metabolic distribution asymmetries is greatly increased over that of the metabolic centroid method, while retaining its advantages; it is almost invariant to head size, head positioning, photon scatter, and the positron emission tomography (PET) camera's full width at half-maximum. It does not require magnetic resonance, computed tomography, or x-ray images. To test the method we analyzed the metabolic PET images of 40 normal subjects and 20 schizophrenics. The results show a unification of several metabolic characteristics of schizophrenic brains, such as laterality, hypofrontality, cortical/subcortical abnormalities, and overall brain hypometabolism, which were identified by different laboratories in separate studies using differing methodologies. Here they are presented by a single automatic objective method.  相似文献   
999.
Three patients with hypereosinophilia showed different forms of peripheral neuropathy: severe polyneuropathy of prevalently sensory type (case 1), mild sensory neuropathy (case 2), acute mononeuropathy of the median nerve with subclinical polyneuropathy (case 3). Hypereosinophilia was probably idiopathic, however the presence of atypical findings suggested transition to vasculitides or collagen disease. Sural nerve biopsy in cases 1 and 2 showed features of axonopathy in both, although of different severity, reflecting the variability of clinical involvement and, probably, heterogeneous pathogenic mechanisms. Peripheral nerve involvement associated with hypereosinophilia may be related to neurotoxicity of eosinophils, or to vascular damage.  相似文献   
1000.
3α-Hydroxy-5α-pregnan-20-one (HPO) is a progesterone metabolite which exhibits narcotic properties at high concentrations by interactions with the receptor for gamma-aminobutyric acid (GABA). The present investigation characterized low-dose effects of HPO on GABAA receptor binding, by determining the allosteric properties of HPO on the in vitro binding of 3H-muscimol to membrane fractions from the cerebella of ovariectomized rats. A newly developed method for tissue preparation was used to wash out endogenous ligands interfering with the assay. HPO reduced the affinity of 3H-muscimol to GABAA receptor sites by 52% and enhanced the number of accessible binding sites from 5.5±0.5 to 7.5±1.3 pmol/mg protein at subnanomolar (0.1 nM) HPO concentrations. The modulatory effects of HPO on GABAA receptor binding provide evidence that this pregnane steroid might be a physiologically relevant modulator of GABAergic neurotransmission.  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