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   7251篇
  免费   432篇
  国内免费   215篇
耳鼻咽喉   73篇
儿科学   67篇
妇产科学   44篇
基础医学   1545篇
口腔科学   390篇
临床医学   531篇
内科学   811篇
皮肤病学   74篇
神经病学   1010篇
特种医学   413篇
外国民族医学   1篇
外科学   608篇
综合类   920篇
预防医学   469篇
眼科学   54篇
药学   395篇
中国医学   148篇
肿瘤学   345篇
  2024年   6篇
  2023年   92篇
  2022年   149篇
  2021年   224篇
  2020年   200篇
  2019年   207篇
  2018年   225篇
  2017年   195篇
  2016年   208篇
  2015年   205篇
  2014年   434篇
  2013年   445篇
  2012年   374篇
  2011年   470篇
  2010年   380篇
  2009年   370篇
  2008年   353篇
  2007年   376篇
  2006年   326篇
  2005年   295篇
  2004年   272篇
  2003年   227篇
  2002年   194篇
  2001年   178篇
  2000年   147篇
  1999年   133篇
  1998年   142篇
  1997年   139篇
  1996年   116篇
  1995年   117篇
  1994年   88篇
  1993年   76篇
  1992年   74篇
  1991年   51篇
  1990年   48篇
  1989年   47篇
  1988年   39篇
  1987年   29篇
  1986年   34篇
  1985年   53篇
  1984年   28篇
  1983年   37篇
  1982年   17篇
  1981年   27篇
  1980年   16篇
  1979年   10篇
  1978年   5篇
  1977年   6篇
  1976年   8篇
  1972年   2篇
排序方式: 共有7898条查询结果,搜索用时 15 毫秒
71.
72.
Colorectal neoplasms obtained at colonoscopy were examined by argyrophilic nucleolar organizer region (AgNOR) staining to evaluate the usefulness of AgNOR as a discriminant for malignancy. AgNOR dots were divided into two kinds: 'structures' (larger and less-densely stained) corresponding to the nucleolus, and 'units' (smaller and densely stained) presumed to be true AgNOR within the structure. The number of structures per nucleus did not differ between the adenoma and carcinoma groups, whereas the number of units per nucleus showed a significant difference. However there were several cases showing an overlap between the adenoma and carcinoma groups, leading to a difficulty in deciding whether any given case was benign or malignant. Three types of AgNOR patterns were categorized based on the ratio of units to structure. Type I was defined as the unit being indistinguishable from the structure, Type II as each structure having one to five units, and Type III as at least one structure having six or more units, irrespective of total number of units per nucleus. The colorectal lesions in which more than half of the neoplastic cells showed Type III coincided well with carcinomas histologically diagnosed, with the exception of adenomas with severe atypia. Labeling index of proliferating cell nuclear antigen (PCNA LI) differed between the adenoma and carcinoma groups with a considerable extent of overlap, and correlated to some extent with the AgNOR values. These results showed that the AgNOR staining was useful for determining malignancy and its usefulness appeared superior to PCNA LI.  相似文献   
73.
A 22-year-old woman with Cushing's syndrome, caused by an extremely rare suprasellar ectopic pituitary adenoma, is presented. Magnetic resonance imaging and computed tomography revealed a well-circumscribed mass in the right suprasellar region. Endocrinological tests showed elevated s-adrenocorticotropic hormone level and hypercortisolemia. The tumor was totally removed by right subfrontal approach. At the time of the operation, the tumor was in continuity with the distal pituitary stalk but not with the pituitary gland. The diaphragma sellae was intact. Histologic diagnosis of the tumor specimen was confirmed as a pituitary adenoma. After surgical removal of the tumor, continued improvement in the patient's laboratory results and disappearance of her endocrine symptoms strongly indicated the absence of adenoma cells in the pituitary gland or stalk. Six years post-surgery, there was no evidence of recurrence in the patient's clinical and laboratory examination. This tumor probably originated from aberrant anterior pituitary cells of the pituitary stalk.  相似文献   
74.
面神经颞支的应用解剖学研究   总被引:2,自引:1,他引:2  
目的:为预防额颞区手术和翼点入路的颅内手术损伤面神经颞支提供解剖学资料。方法:60侧成人头部标本,解剖观测面神经颞支的分支、行程及层次。结果:(1)面神经颞支多为2~4支,占95.00%(57侧)。(2)面神经颞支离开腮腺上缘后向前上走行,从颧弓浅面跨过进入额颞区,后走行于浅筋膜和颞筋膜浅层之间;在腮腺上缘及颧弓上缘处面神经颞支的最后1支距耳屏尖的距离分别为(23.79±0.27)mm和(30.67±0.37)mm。结论:面神经颞支入肌前在颧弓以下一段位置较深、以上表浅。从耳屏尖向前23mm范围内无该神经通过,为手术安全区。  相似文献   
75.
Thom K  Morrison C  Lewis JC  Simmonds P 《Virology》2003,306(2):324-333
TT virus (TTV) and TTV-like minivirus (TLMV) are small DNA viruses with single-stranded, closed circular, antisense genomes infecting man. Despite their extreme sequence heterogeneity (>50%), a highly conserved region in the untranslated region (UTR) allows both viruses to be amplified by polymerase chain reaction (PCR). TTV/TLMV infection was detected in 88 of 100 human plasma samples; amplified sequences were differentiated into TTV and TLMV by analysis of melting profiles, showing that both viruses were similarly prevalent. PCR with UTR primers also detected frequent infection with TTV/TLMV-related viruses in a wide range of apes (chimpanzees, gorillas, orangutans, gibbons) and African monkey species (mangabeys, drills, mandrills). These findings support the hypothesis for the co-evolution of TTV-like viruses with their hosts over the period of primate speciation, potentially analogous to the evolution of primate herpesviruses.  相似文献   
76.
Mixed aeciospore isolates ofCronartium flaccidum andPeridermium pini were obtained from single-tree infections in Britain, Italy and Greece. The 5.8s ribosomal RNA gene and flanking intergenic transcribed spacer regions ITS 1 and ITS2 were found to be highly similar betweenC. flaccidum andP. pini. Within samples heterogeneity was detected at three nucleotide loci in the ITS1 and at four loci in the ITS2 suggesting that several fungal genotypes may occur at a single infection court. The heterogeneity was confirmed by heteroduplex polymorphism analysis of mixed aeciospore products. RFLP of the ribosomal intergenic spacer region 1 (IGSI) amplified from the same templates indicated limited sequence polymorphism in some copies of this repeated locus. Both the sexual and asexual forms ofC. flaccidum show evidence of sequence polymorphism in two independent, non-coding regions of the ribosomal gene array. Variation appears to be greater in the sexual formC. flaccidum, than in the monoaecious formP. pini.  相似文献   
77.
Summary Total genomic DNA was isolated from three cereal stem rusts, Puccinia graminis f. sp. tritici, f. sp. secalis, f. sp. avenae, and two cereal leaf rusts, P. recondita f. sp. tritici and P. coronata f. sp. avenae, and analyzed for the presence of heterogeneity in the intergenic region of the ribosomal DNA repeat unit. A 1 kb region of the repeat unit between the 26s and the 5s rRNA genes (IGR-1) was amplified by PCR and was found to be heterogeneous within each isolate and variable in size between races and species. The PCR results were confirmed by Southern blot analysis of native DNA. In an isolate of race C36(48), heterogeneity appeared to be due to variable numbers of 0.1 kb subrepeats in IGR-1. Nine wheat stem rust strains representing nine different races produced a unique pattern of heterogeneity while two different isolates of one race were identical, as were five of another. This may provide a rapid method for race identification in wheat stem rust. Heterogeneity and polymorphism in rye stem rust, oat stem rust, wheat leaf rust, and oat crown rust, was less pronounced than in wheat stem rust. In the course of this work, the 5s rRNA gene was located and its position and orientation within the ribosomal repeat unit was established.  相似文献   
78.
79.
经翼点入路鞍区手术间隙解剖学研究   总被引:6,自引:1,他引:6  
目的 为鞍区显微外科手术提供解剖学参数。方法 对 10具成人尸体头颅的鞍区手术间隙及邻近血管、神经进行解剖学观察、测量。结果 大脑中动脉M1段在距颈内动脉分叉部 18.4± 3.2mm处形成初级分叉 ,向后上方发出约 14支穿支 ,分布至基底节区。鞍结节后缘至视交叉前缘相距 5 .6± 1.1mm ,两侧视神经内侧缘间最大距离 10 .5± 1.4mm。颈内动脉从内侧壁发出 3.2支垂体上动脉 ,终止于视神经、视交叉、视束和垂体柄 ;视神经 -颈内动脉三角三边长度分别为 6 .6± 0 .6mm ,6 .9± 0 .7mm ,4 .0± 0 .4mm。颈内动脉 -小脑幕三角三边长度为 8.8± 0 .7mm ,6 .7± 0 .7mm ,4 .4± 1.0mm ,后交通动脉起自颈内动脉后外壁距分叉部 7.7± 0 .5mm ,止于大脑后动脉 ,全长 18.7± 2 .3mm ,途中发出 7.4条穿通支。脉络膜前动脉从距分叉部 4 .4± 0 .6mm处发出 ,向后方走行 ,发出细小分支 ,分布于钩回、脉络丛。前交通动脉全长 1.9± 0 .3mm ,在前交通动脉上方 0 .9± 0 .2mm ,大脑前动脉A2段前外壁发出Heubner回返动脉 ,分布于胼胝体、基底节、下丘脑及额叶脑组织。结论 应用这些间隙的解剖学测量可指导与鞍区相关的手术 ,安全显露鞍区解剖结构 ,不损伤重要的血管和神经。  相似文献   
80.
At its extrapelvic course the inferior gluteal a. is found to be strictly related to the sciatic n. This relationship has been described in a general way, emphasizing its medial localization in respect to the nerve. Clinicosurgical reports describe cases of aneurysms of the inferior gluteal a. on its extrapelvic course and subsequent compression at the nerve. In order to get further details on the relationship between these two structures, 80 gluteal regions from 40 cadavers of adult Brazilian individuals, 29 males and 11 females, were dissected. The inferior gluteal a. was found medial to the sciatic n. in 62 cases (77.5%); in the 18 remaining (22.5%) the trunk of the artery or one of its branches perforated the nerve. Of these, 14 (77.8%) were males and 4 (22.2%) females. This disposition was found 8 times (44.4%) on the right and 10 (55.6%) on the left side; was unilateral in 4 individuals (1 on the right and 3 on the left side) and bilateral in 7. The course of the inferior gluteal a. through the sciatic n. and/or the presence of aneurysms of this artery should be considered as a possible cause of nerve compression.  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