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   37976篇
  免费   2133篇
  国内免费   57篇
耳鼻咽喉   385篇
儿科学   1154篇
妇产科学   812篇
基础医学   5824篇
口腔科学   287篇
临床医学   3426篇
内科学   9106篇
皮肤病学   855篇
神经病学   3547篇
特种医学   1141篇
外国民族医学   31篇
外科学   4676篇
综合类   82篇
一般理论   6篇
预防医学   2697篇
眼科学   628篇
药学   2541篇
中国医学   68篇
肿瘤学   2900篇
  2023年   208篇
  2022年   144篇
  2021年   554篇
  2020年   326篇
  2019年   601篇
  2018年   1106篇
  2017年   775篇
  2016年   736篇
  2015年   913篇
  2014年   930篇
  2013年   1503篇
  2012年   2587篇
  2011年   2539篇
  2010年   1228篇
  2009年   962篇
  2008年   2325篇
  2007年   2374篇
  2006年   2242篇
  2005年   2321篇
  2004年   2255篇
  2003年   2061篇
  2002年   2016篇
  2001年   1061篇
  2000年   1129篇
  1999年   897篇
  1998年   182篇
  1997年   124篇
  1996年   131篇
  1995年   126篇
  1994年   107篇
  1992年   522篇
  1991年   463篇
  1990年   462篇
  1989年   434篇
  1988年   390篇
  1987年   379篇
  1986年   339篇
  1985年   318篇
  1984年   227篇
  1983年   180篇
  1982年   104篇
  1979年   158篇
  1974年   119篇
  1973年   105篇
  1972年   108篇
  1971年   114篇
  1970年   106篇
  1969年   129篇
  1968年   110篇
  1967年   102篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
91.
BACKGROUND: Conventional and atypical antipsychotics have different affinities for D2 receptors, and these receptors are principally located in the striatum. Given that this cerebral structure was previously found to play a major role in procedural learning, the antipsychotic treatment in schizophrenia may be determinant for the procedural learning profile of these patients. OBJECTIVE: The current study was aimed at verifying whether procedural learning differs in patients with schizophrenia treated with conventional antipsychotics and patients treated with atypical antipsychotics. METHOD: Forty-five patients with schizophrenia were divided into 3 different groups according to their pharmacologic treatment: (1) haloperidol, a classical neuroleptic with high D2 receptor affinity; (2) clozapine, an atypical neuroleptic with practically no D2 receptor affinity; and (3) risperidone, an atypical neuroleptic that nevertheless shows high D2 receptor affinity. Patients were compared to 35 control subjects on a visuomotor procedural learning task (mirror drawing). RESULTS: All patients were able to learn the task. However, those treated with haloperidol showed some degree of learning impairment, while those treated with clozapine or risperidone did not show this impairment. In addition, performance per se, regardless of the learning, was found to be affected in the haloperidol and risperidone, but not in the clozapine groups. CONCLUSION: Procedural learning in schizophrenia may be differentially affected, depending on the pharmacologic profiles of the antipsychotics used for the treatment of this illness.  相似文献   
92.
We have studied 20 pineal parenchymal tumors (PPT) and 4 normal or cystic pineal glands both by light and electron microscopy and immunohistochemistry with antibodies against glial markers [glial fibrillary acidic protein (GFAP) and protein S-100] or neural/neuroendocrine markers [neurofilaments (NF), synaptophysin and chromogranin A]. Light microscopy revealed the cellular organization of pinealocytes in the normal gland and in different morphological types of pineal tumors (typical pineocytomas, PPT with intermediate differentiation, mixed PPT exhibiting elements of both pineocytoma and pineoblastoma and pineoblastomas). Immunohistochemistry showed the presence of GFAP and protein S-100 in interstitial cells in nonneoplastic pineal gland. Cell processes were labeled with anti-synaptophysin and anti-NF antibodies. No immunoreactivity was found for chromogranin A in non-neoplastic pineal gland. In pineocytomas, GFAP and protein S-100 were observed in interstitial cells. Synaptophysin and NF were present in the large rosettes of pineocytomas. Synaptophysin, NF and chromogranin A were present in pineocytomas with a lobular arrangement of cells. Anti-chromogranin A immuno-reactivity was also seen in lobular areas of some PPT with intermediate differentiation. Analysis of normal human pineal gland by electron microscopy showed the presence of vesicle-crowned rodlets (VCR or synaptic ribbons), fibrous filaments (F), paired twisted filaments but few dense-core vesicles (DCV) in normal pinealocytes. Tumoral pineal cells appeared to differentiate either towards a neurosensory pathway characterized by the presence of sensory cells elements (VCR and F), or towards a neuroendocrine pathway, with the occurrence of many DCV. Immunogold labeling demonstrated the presence of chromogranin A in neurosecretory granules.Supported by grants from the Région Rhône Alpes and from INSERM (CJF 90-10)  相似文献   
93.
Nucleolar organizer regions (NORs) were counted on normal tissue, condylomata, CIN 1, 2 and 3, to verify the possibility of a differentiation between the various grades of CIN and between them and condylomata. Counts were performed on the full thickness of the tissue, layer by layer (stratified counts). A significant difference (p < 0.05) was found between the mean of normal tissue in relation to condylomata and CIN 2 and 3 and between CIN 1, and CIN 2 and 3. There was no significance (p > 0.05) between normal tissue and CIN 1, between CIN 2 and 3 and between condylomata and CIN 2 and 3. The range of variations in the counts was associated with overlapping between the various cases. Our data showed also a progressive rise in mean NOR values from normal tissue to CIN 3. The stratified counts showed in all the groups a rise from basal to parabasal cells. Counts on parabasal and intermediate layers distinguished two groups of cases. In one there was either the same number of dots or a further rise while in the other a definite decrease was seen. The former pattern may be related to a potential for malignant evolution of the lesion. NORs should be counted in all cases of CIN and condylomata to treat more aggressively those lesions which present the patterns of a progressive rise of NORs from basal to intermediate cells.  相似文献   
94.
Two sisters with hereditary prolidase deficiency are presented. Recurrent and painful leg ulcers are the predominant feature.  相似文献   
95.
Regional cerebral blood flow (rCBF) was studied by SPECT using 133Xe in 42 children, aged 2 days to 19 years, considered as neurologically normal. rCBF was measured on cortical regions and on the cerebellum and thalamus. Curves for reference values and standard deviation were defined for each region. At birth, cortical rCBFs were lower than those for adults; after birth they increased until 5 or 6 yr of age to values 50%-85% higher than those for adults and thereafter decreased, reaching adult levels between 15 and 19 yr. Neonatal values of rCBF on cerebellum and thalamus were slightly higher than adult level, but not significantly; after age 1, they followed the common pattern for cortical curves. When rCBFs were expressed in percent global CBF, they were lower at birth than adult levels in the cortex, then increased and reached a plateau corresponding to the adult value before the second year of age. The time needed to reach normal adult values differed for each cortical region. The shortest time was found on the primary cortex and the longest on the associative cortex. Cognitive development of the child seems to be related to changes in blood flow of the corresponding brain regions.  相似文献   
96.
The effect of 5-HT1A agonists was studied in the isolation-induced social behavioural deficit test. The drugs 8-OH-DPAT (0.125 mg/kg), buspirone (16 mg/kg) and ipsapirone (8 mg/kg) further increased the deficit. Unlike 8-OH-DPAT, the other two drugs may act non-specifically since they reduced spontaneous motor activity at 16 mg/kg, as measured in an activity meter. In addition, 8-OH-DPAT (0.25 mg/kg), buspirone (8 mg/kg) and ipsapirone (8 mg/kg) decreased exploratory activity in the open-field test. Since the smallest active doses were very close in the behavioural deficit and in the open-field tests, it is suggested that a common phenomenon, increased emotionality or reactivity, sustained both these reductions in activity. The increase in the behavioural deficit induced by 8-OH-DPAT, was likely to have resulted from stimulation of 5-HT1A receptors, since it was impaired by pretreatment with penbutolol, a beta-adrenergic-blocking drug, also known to bind to 5-HT1 receptors. Since it was previously shown that the behavioural deficit was reduced by agonists at 5-HT1B receptors, it is proposed that the behavioural inhibition, resulting from an isolation-induced increase in reactivity is bi-directionally modulated by serotonergic drugs, where 5-HT1A agonists increase and 5-HT1B agonists decrease this inhibition.  相似文献   
97.
In our institution, total body irradiation (TBI) is performed by means of a sweeping beam technique. Toxicity of the procedure was evaluated according to the only grading system designed for high dose chemoradiotherapy. One hundred patients undergoing TBI and conditioned with a standard cyclophosphamide regimen before BMT were evaluated. Regimen-related toxicity was graded according to the Seattle transplantation toxicity system, from 0 to IV (fatal toxicity), in eight organs on days 0, 7, 14, 28 and 100 for lungs. Eighteen patients did not develop any toxicity. Grades III, IV toxicities were uncommon (9%) and were not influenced by dose of TBI, GVHD prophylaxis, disease status and allogenicity although no grade IV toxicity was observed among autologous marrow recipients. However, grade II toxicity was more common in patients receiving allogeneic vs autologous grafts (p < 0.01) because of increased mucosal (p = 0.002) and liver (p = 0.12) toxicities. Renal toxicity was unevaluable. When cumulative toxicity was equal or higher than 4, day 100 survival was worse (p = 0.05). These data confirm the safety of our TBI procedure and the validity of the grading system except for renal toxicity. We suggest that a more aggressive conditioning regimen may be tolerated by patients receiving autologous grafts.  相似文献   
98.
Brain macrophages synthesize interleukin-1 and interleukin-1 mRNAs in vitro   总被引:10,自引:0,他引:10  
Amoeboid microglial cells (brain macrophages) were purified from early post-natal mouse brain cultures. The percentage of cells stained with an anti-Mac-1 antibody was greater than 95%. Stimulation of these brain macrophages by lipopolysaccharides induced the synthesis of interleukin-1 (IL-1), which, in part, remained associated with the cell surface and, in part, was released into the culture medium. In contrast, pure primary astrocyte cultures and cell lines of transformed or immortalised astrocytes did not synthesise significant amounts of IL-1, demonstrating that amoeboid microglia and not astrocytes synthesise IL-1 in vitro. These physiological data were confirmed by RNA hybridisation studies showing that, on LPS treatment, brain macrophages synthesise significant amounts of IL-1 alpha and IL-1 beta mRNAs.  相似文献   
99.
In this prospective study, we have investigated incidence of injuries of different severity, types of injury, and mechanisms of injury during ice hockey practice and games. One Swedish elite hockey team was closely observed during three seasons (1982 to 1985). There was a total number of 95 injuries and 29 facial lacerations. The majority of injuries were minor (73%) and only 8% were classified as major. Seventy-six percent of the injuries occurred during games and 24% during practice. The incidence of injury during practice was 1.4 per 1,000 player-practice hours and 78.4 per 1,000 player-game hours. In comparison with other sports, the incidence of injury during hockey practice is very low, while that during games is high. Eighty percent of the injuries were caused by trauma and 20% by overuse. The most common types of injury were contusions, strains, and sprains. Complete tear of the medial collateral ligament of the knee was the most common severe injury. Most injuries resulted from body contact, predominantly tackling (checking), and from puck or stick contact. A reduction of the number of minor and moderate injuries should be possible by stricter enforcement of the hockey rules, especially against stick violations, and more widespread use of visors.  相似文献   
100.
Described in Switzerland in the early '60, the major features of hereditary non-polyposis colon cancer syndrome (HNPCCS) were established 20 years ago by H. T. Lynch. HNPCCS accounts for at least 60% of the colon cancer etiology. Cancer family syndrome is defined by the presence of extracolonic primary tumors in addition to colon cancer. Both syndromes are transmitted by an autosomic dominant pattern. None of the known biomarkers are specific and/or sensitive enough to rely on their predictive values of patient's risks. A typical Swiss family was investigated on the basis of the cancer-prone family history. 21% of the family members observed over 5 generations presented one or more (30% of the cases) colo-rectal neoplasms at the age of 50. 55% of the tumors were right sided. Histologically, half of the tumors were mucinous. 30% of metachronous cancer appeared within 10 years. Polyps (1-3) and flat adenomas were associated to the lesion in 57%. Extra-colonic tumors appeared in 18% of family members and in half of the colon cancer patients. The sites of these tumors were the urinary tract, ovary, small bowel, breast and stomach. Two fibroblast strains of affected individuals were established. No increased tetraploidy was noted. Preliminary results suggest that this two strains are rather sensitive to ionising radiation. Often neglected, family history of colon cancer remains the major diagnostic and decision-making tool of a such syndrome. It will necessitate special treatment of affected subjects and early screening of the relatives.(ABSTRACT TRUNCATED AT 250 WORDS)  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