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   536729篇
  免费   27922篇
  国内免费   516篇
耳鼻咽喉   6750篇
儿科学   17184篇
妇产科学   12975篇
基础医学   93762篇
口腔科学   12492篇
临床医学   48997篇
内科学   96563篇
皮肤病学   12204篇
神经病学   34545篇
特种医学   20044篇
外国民族医学   53篇
外科学   78925篇
综合类   7671篇
现状与发展   2篇
一般理论   111篇
预防医学   38774篇
眼科学   12110篇
药学   41763篇
  1篇
中国医学   1126篇
肿瘤学   29115篇
  2021年   3986篇
  2018年   5817篇
  2017年   4197篇
  2016年   4958篇
  2015年   5455篇
  2014年   7253篇
  2013年   10692篇
  2012年   15837篇
  2011年   17686篇
  2010年   10154篇
  2009年   9002篇
  2008年   15997篇
  2007年   17720篇
  2006年   17253篇
  2005年   16584篇
  2004年   16212篇
  2003年   15559篇
  2002年   15072篇
  2001年   22571篇
  2000年   23113篇
  1999年   19059篇
  1998年   5314篇
  1997年   4414篇
  1996年   4441篇
  1995年   4171篇
  1992年   14473篇
  1991年   15879篇
  1990年   16003篇
  1989年   15675篇
  1988年   14375篇
  1987年   14265篇
  1986年   13222篇
  1985年   12756篇
  1984年   9446篇
  1983年   8034篇
  1982年   4199篇
  1979年   8989篇
  1978年   6409篇
  1977年   5176篇
  1976年   5531篇
  1975年   6651篇
  1974年   7450篇
  1973年   7186篇
  1972年   6617篇
  1971年   6341篇
  1970年   5917篇
  1969年   5499篇
  1968年   5183篇
  1967年   4644篇
  1966年   3986篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Conclusions Limitation of this analysis is participation of limited centers. Though all the regions of the country are represented total number of procedures reported are less. Isolated CABG is commonest procedure performed in 2004. Congenital surgical procedures are more than the valvular heart disease procedure. For appropriate categorization we need standard nomenclature for various congenital surgical procedures.  相似文献   
52.
53.
OBJECTIVES: to examine the management and outcome of patients with traumatic popliteal artery pseudoaneurysms with delayed presentation. MATERIALS: over a 2-year period 7 patients with traumatic popliteal pseudoaneurysms presenting to a tertiary referral unit after a delay of 1 month were reviewed. METHODS: a retrospective review of clinical records. RESULTS: the median interval between injury and presentation was 1.5 months (range 1-24 months). Penetrating trauma from gunshot wounds was the cause of the initial vascular injury in 6 patients and a stab wound in one. All patients had large pseudoaneurysms of more than 8 cm filling the popliteal fossa with variable degrees of fixed flexion deformity (FFD) of the knee. Severe FFD of more than 40 degrees was noted in 2 patients and 3 others had mild flexion deformities of 10 to 20 degrees. Six patients underwent repair of the pseudoaneurysm. One patient required an above knee amputation due to an infected false aneurysm. There were no deaths or graft related complications. Despite aggressive post-operative physiotherapy only 2 patients were able to completely straighten the leg at the time of discharge. CONCLUSIONS: in patients with neglected popliteal artery pseudoaneurysms, morbidity is associated with the pre-operative degree of fixed flexion deformity of the knee.  相似文献   
54.
V Frecer  S Miertus 《Neoplasma》1988,35(5):525-538
A mechanistic QSAR study on N-nitrosamines (NA) was performed with the aid of the semiempirical MINDO/3 method. Both the chemical reactivity and the transport in biological medium were taken into account. The parent NA molecules and their first reaction intermediates in the metabolic activation pathway were examined for possible determinants of the relative carcinogenic potency. The correlations found support the previous suggestions concerning the metabolic C alpha radical hydroxylation of NA. The role of transport properties in the early stage of NA biotransformation was also demonstrated.  相似文献   
55.
The influence of the pore size of Nucleopore diffusion-chamber filters on the rate of proliferation and differentiation of periosteal cells in muscle was studied in 44 growing rabbits. Periosteal grafts were placed in chambers (16-19 in each experimental group) sealed with filters with a pore size of 0.4, 0.6, 0.8, 1.0, or 2.0 micron. Each chamber was implanted into the paraspinal muscle of the rabbit, where it remained for 16 weeks. The osteochondrogenic activity of the graft grew linearly when the pore size increased from 0.4 to 1.0 micron. In the chambers with a pore size of 2.0 micron, both bone and cartilage were found in only one chamber. Bone and cartilage were not found outside any of the chambers. The present results showed that the pore size of the filters significantly affected the ability of the periosteal graft to form bone and cartilage.  相似文献   
56.
The effects of bulk versus particulate polymethylmethacrylate on bone   总被引:3,自引:0,他引:3  
Twenty-one mature New Zealand white female rabbits were allocated into three groups of seven rabbits. Group I received a bolus of doughy Simplex polymethylmethacrylate (PMMA) cement injected into the proximal tibia through a drill hole. Group II received a preformed, cooled, bulk PMMA pellet. Group III had particulate PMMA powder implanted. The operated, but nonimplanted, left tibiae served as controls. Animals were killed after four months. Histologically, both Group I and Group II demonstrated a thin, fibrous tissue membrane at the implant interface. Particulate PMMA (Group III) stimulated a much thicker, florid, foreign body reaction composed of histiocytes and giant cells. The foreign body response to particulate acrylic cement was similar to that seen in failed cemented joint replacement arthroplasty in humans.  相似文献   
57.
58.
PURPOSETo use functional MR imaging to measure the effect of frequency (pitch), intensity (loudness), and complexity of auditory stimuli on activation in the primary and secondary auditory cortexes.METHODSMultiplanar echo-planar images were acquired in healthy subjects with normal hearing to whom auditory stimuli were presented intermittently. Functional images were processed from the echo-planar images with conventional postprocessing methods. The stimuli included pure tones with a single frequency and intensity, pure tones with the frequency stepped between 1,000, 2,000, 3,000, or 4,000 Hz, and spoken text. The pixels activated by each task in the transverse temporal gyrus (TTG) and the auditory association areas were tabulated.RESULTSThe pure tone task activated the TTG. The 1,000-Hz tone activated significantly more pixels in the TTG than did the 4,000-Hz tone. The 4,000-Hz tone activated pixels primarily in the medial TTG, whereas the 1,000-Hz tone activated more pixels in the lateral TTG. Higher intensity tones activated significantly more pixels than did lower intensity tones at the same frequency. The stepped tones activated more pixels than the pure tones, but the difference was not significant. The text task produced significantly more activation than did the pure tones in the TTG and in the auditory association areas. The more complex tasks (stepped tones and listening to text) tended to activate more pixels in the left hemisphere than in the right, whereas the simpler tasks activated similar numbers of pixels in each hemisphere.CONCLUSIONAuditory stimuli activate the TTG and the association areas. Activation in the primary auditory cortex depends on frequency, intensity, and complexity of the auditory stimulus. Activation of the auditory association areas requires more complex auditory stimuli, such as the stepped tone task or text reading.  相似文献   
59.
PURPOSETo study the relationship of lumbar facet joint tropism to degeneration of the cartilage and subcortical bone in the facet joints and the effect of tropism in intervertebral disk degeneration.METHODSThe orientation of 104 cadaveric lumbar facet joints with respect to sagittal plane was measured on CT scans, and the joints were classified as having no tropism, mild tropism, or severe tropism. On MR images, the severity of cartilage degeneration and bony sclerosis was measured. The correlation between tropism and degeneration was calculated, as was the relationship among age, spinal level, and degeneration.RESULTSWe identified four spinal levels with severe tropism, six with moderate tropism, and 94 without tropism. Cartilage degeneration was not significantly more severe in the joints with tropism than in the joints without. Sclerosis was slightly greater in the joints with tropism than in the joints without it. Sclerosis and cartilage degeneration were significantly related to age and spinal level.CONCLUSIONAge, spinal level, and overall facet joint angle are more important factors in facet joint degeneration than is tropism.  相似文献   
60.
Summary GM1- and GM2-gangliosides were isolated from brain and radio-labelled. The labelled moieties were localized by hydrolysis with lysosomal enzymes, followed by thin-layer chromatography of the products. High-resolution loading tests with labelled gangliosides were developed and found to differentiate infantile and juvenile forms of GM1- and GM2-gangliosidoses as well as the identification of B, O and AB types of GM2-gangliosidosis.  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