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   25605篇
  免费   1333篇
  国内免费   117篇
耳鼻咽喉   131篇
儿科学   431篇
妇产科学   317篇
基础医学   3396篇
口腔科学   739篇
临床医学   1720篇
内科学   5980篇
皮肤病学   479篇
神经病学   2478篇
特种医学   1143篇
外科学   4423篇
综合类   104篇
现状与发展   1篇
预防医学   846篇
眼科学   609篇
药学   1973篇
中国医学   62篇
肿瘤学   2223篇
  2023年   136篇
  2022年   290篇
  2021年   535篇
  2020年   257篇
  2019年   379篇
  2018年   504篇
  2017年   397篇
  2016年   465篇
  2015年   474篇
  2014年   626篇
  2013年   794篇
  2012年   1268篇
  2011年   1459篇
  2010年   770篇
  2009年   638篇
  2008年   1177篇
  2007年   1345篇
  2006年   1352篇
  2005年   1315篇
  2004年   1250篇
  2003年   1198篇
  2002年   1195篇
  2001年   810篇
  2000年   822篇
  1999年   772篇
  1998年   303篇
  1997年   243篇
  1996年   217篇
  1995年   177篇
  1994年   163篇
  1993年   172篇
  1992年   546篇
  1991年   491篇
  1990年   458篇
  1989年   446篇
  1988年   433篇
  1987年   372篇
  1986年   364篇
  1985年   368篇
  1984年   212篇
  1983年   170篇
  1982年   99篇
  1981年   91篇
  1980年   88篇
  1979年   172篇
  1978年   128篇
  1977年   96篇
  1974年   129篇
  1973年   115篇
  1969年   102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
This report concerns a notable case of progressive supranuclear palsy exhibiting asymmetric dentate nucleus and thalamic degeneration with numerous torpedoes. The neuronal loss in the ventral lateral nucleus of the thalamus was predominant on the right side, while in the cerebellum, a quantitative study revealed the contralateral predominance of the neuronal loss in the dentate nuclei and torpedo formation, with preserved Purkinje cells. The abnormal tau-protein-related profiles in the two nuclei did not show any laterality in their distribution, indicating that the dentatothalamic tract may have been affected in a non-specific way in this case. In addition, the fact that the prominent sites of torpedo formation and loss of dentate nucleus neurons are identical supports the hypothesis that the torpedoes may be formed in association with neuronal loss in the dentate nucleus because of a plausible metabolic change in Purkinje cells through synaptic detachment of their axon terminals. Received: 4 January 1996 / Revised: 27 March 1996 / Accepted: 5 April 1996  相似文献   
62.
K Matsumoto 《Nephron》1990,55(3):300-305
We have investigated the effect of recombinant tumor necrosis factor (r-TNF) on the release of interleukin-1 (IL-1) in glomerular cultures from rats with an accelerated autologous form of nephrotoxic serum nephritis (NTSN). Freshly isolated glomeruli from the NTSN rats were incubated for 24 h in the presence of r-TNF. When the glomeruli were activated by r-TNF substantial amounts of IL-1 could be detected in the supernatants as measured by the mouse thymocyte assay. The r-TNF-induced IL-1 activity was significantly higher in rats with NTSN than those in normal controls and the other control group, consisting of preimmunized rats (rabbit IgG), then given normal rabbit globulin instead of NTS. To avoid the effect of prostaglandins on the IL-1 assay, we cultured the glomeruli with addition of indomethacin and assayed IL-1 activity in the culture supernatants. This cyclooxygenase inhibitor augmented r-TNF-induced IL-1 production. Our data suggest that r-TNF can serve as a potent stimulator of IL-1 synthesis in glomerular cultures from rats with NTSN.  相似文献   
63.
The seven metabolites of (+)-dehydroabietic acid (DHA) were newly isolated from rabbit urine by liquid chromatography. On the basis of chemical and spectral data their structures were established to be (15S)-8,11.13-abietatrien-16,18-dioic acid, 2 alpha-hydroxy-8,11,13,15-abietatetraen-18-oic acid, (15R)-15,16-dihydroxy-8,11,13-abietatrien-18-oic acid, 2 beta,15-dihydroxy-8,11,13-abietatrien-18-oic acid, (15S)-2 beta,16-dihydroxy-8,11,13-abietatrien-18-oic acid, 2 alpha,15-dihydroxy-8,11,13-abietatrien-18-oic acid, and (15S)-2 alpha,16-dihydroxy-8,11,13-abietatrien-18-oic acid. The possible hydroxylation routes of DHA in rabbits and the difference between the metabolism of DHA in microorganisms and that in rabbits are discussed.  相似文献   
64.
A transjugular snare technique was used to retrieve a stretched, residual mechanical detachable coil which extended from the cavernous sinus to the femoral vein, obliterating the transpetrosal route for further embolisation. The coil was snared by a microguidewire. Our new technique is described in this paper. Received: 19 April 1995 Accepted: 31 July 1995  相似文献   
65.
Molecular genetic analysis was performed in a patient with cytochrome b positive X-linked chronic granulomatous disease. A previous Southern blot study, using a cytochrome b heavy chain cDNA as probe, revealed a Pst I restriction fragment pattern for the cytochrome b heavy chain gene (CYBB) different to that of normal individuals. Since restriction length polymorphism with Pst I has never been observed in control individuals and no abnormal restriction fragment patterns in the patient's CYBB was detected with seven other enzymes used, we focussed on the single Pst I site in the CYBB cDNA as being the only mutation site responsible for his disease. A fragment of the patient's cDNA which included the Pst I site was amplified by reverse polymerase chain reaction, and loss of the Pst I site in the fragment was confirmed by incubation with Pst I. Subsequent sequence analysis of the fragment revealed a point mutation in the Pst I site (cytosine to adenine), substituting glutamic acid for alanine at position 57.  相似文献   
66.
67.
Lewis Y (Ley) antigen, a difucosylated tetrasaccharide found on type 2 blood group oligosaccharides of glycolipids and glycoproteins, is thought to be a phenotypic marker predictive of cell differentiation. The distribution of this antigen in human anagen hair follicles was examined by immunohistochemical staining using a monoclonal antibody (AH-6) to Ley. In the bulbar and suprabulbar portion of anagen hair follicles, Ley antigen was detected in the three layers of the inner root sheath. Subsequently, the positive staining became translocated to the innermost layer of the outer root sheath in the middle part of the hair follicles. In the upper portion of the hair follicles, Ley antigen was found in the outer cells of the outer root sheath. These findings suggested that the expression of Ley antigen in the anagen hair follicles was correlated with the processes of keratinization or terminal differentiation.  相似文献   
68.
Because gastric cancers located in the upper third of the stomach are difficult to detect at an early stage, the surgical results remain poor. We performed R4 gastrectomy as a radical procedure for 25 patients, involving complete resection of the latero-aortic and interaorticovenous lymph modes above and below the left renal vein, in combination with the ordinary R2 or R3 gastrectomy (the R4 group). These patients were compared with 156 others who underwent R2 gastrectomy alone (the R2 group). There were no significant differences in operation time, blood loss, or the incidence of complications between the two groups; however, when the survival rates of the patients with tumors invading beyond the subserosa were compared, the 5-year survival rate was found to be significantly higher in the R4 group than in the R2 group. Furthermore, in patients with para-aortic nodal involvement, a significant survival advantage was observed in the R4 group, as compared with the R2 group. These results suggest that the R4 gastrectomy is a rational approach for patients with advanced gastric cancer located in the upper third of the stomach.  相似文献   
69.
We reviewed 12 cases of infarcts in the territory of the anterior choroidal artery (AChA) on CT and/or MRI. In each case vascular occlusion in the region was verified angiographically. Although the extent of the lesion on CT/MR images was variable, all were located on the axial images within an arcuate zone between the striatium anterolaterally and the thalamus posteromedially. The distribution of the lesions on mutiplanar MRI conformed well to the territory of the AChA demonstrated microangiographically. The variability of the extent of the infarcts may be explained by variations in the degree of occlusive changes in the AChA or the development of collateral circulation through anastomoses between the AChA and the posterior communicating and posterior cerebral arteries. The extent of the lesion appeared to be closely related to the degree of neurological deficit.  相似文献   
70.
MRI of the brain in chronic carbon monoxide poisoning   总被引:3,自引:0,他引:3  
We examined 13 patients with chronic carbon monoxide (CO) poisoning by magnetic resonance imaging (MRI); all of them had been in an explosion in a coal mine 25 years previously. Symmetrical globus pallidus lesions were observed in 12, as was degeneration of the white matter, with focal cortical atrophy. The temporal parietal and occipital lobes were usually affected, the parietooccipital region being the most frequently and extensively damaged. Of the 12 patients with white matter degeneration 7 had definitely asymmetrical cortical and subcortical lesions. There were 6 patients with dilated temporal horns, probably due to atrophy of the hippocampal gyri. A history of CO inhalation and an awareness of the typical distributions of lesions are important for recognition of the effects of CO poisoning, especially when patients are in the chronic stage.  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