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   532787篇
  免费   27825篇
  国内免费   500篇
耳鼻咽喉   6693篇
儿科学   17001篇
妇产科学   12611篇
基础医学   92963篇
口腔科学   12383篇
临床医学   48810篇
内科学   95990篇
皮肤病学   11960篇
神经病学   34422篇
特种医学   19803篇
外国民族医学   53篇
外科学   78260篇
综合类   7638篇
现状与发展   2篇
一般理论   107篇
预防医学   38662篇
眼科学   12330篇
药学   41531篇
  1篇
中国医学   1126篇
肿瘤学   28766篇
  2021年   3923篇
  2018年   5762篇
  2017年   4151篇
  2016年   4914篇
  2015年   5417篇
  2014年   7164篇
  2013年   10606篇
  2012年   15718篇
  2011年   17517篇
  2010年   10025篇
  2009年   8887篇
  2008年   15839篇
  2007年   17585篇
  2006年   17070篇
  2005年   16377篇
  2004年   16005篇
  2003年   15383篇
  2002年   14869篇
  2001年   22511篇
  2000年   23060篇
  1999年   18999篇
  1998年   5267篇
  1997年   4386篇
  1996年   4423篇
  1995年   4155篇
  1992年   14463篇
  1991年   15876篇
  1990年   16010篇
  1989年   15684篇
  1988年   14362篇
  1987年   14248篇
  1986年   13216篇
  1985年   12738篇
  1984年   9437篇
  1983年   8022篇
  1982年   4201篇
  1979年   8990篇
  1978年   6411篇
  1977年   5170篇
  1976年   5519篇
  1975年   6645篇
  1974年   7444篇
  1973年   7183篇
  1972年   6610篇
  1971年   6318篇
  1970年   5903篇
  1969年   5474篇
  1968年   5168篇
  1967年   4626篇
  1966年   3980篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
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   
22.
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   
23.
24.
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   
25.
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   
26.
The effect of localized hyperthermia on blood flow and cis-diamminedichloroplatinum(II) (CDDP) pharmacokinetics in 7,12-dimethylbenz[a]anthracene-induced mammary adenocarcinomas was studied. Blood flow was determined in rat tumors and normal tissue immediately and 1, 2, and 3 h after local hyperthermia treatment (43 degrees C, 1 h) as well as in unheated tumors of rats. The rate of blood flow in the tumor was increased 1.9 times at the end of treatment relative to control values and returned to the control values by 3 h after hyperthermia. Similarly, the rate of blood flow in the peripheral skin around the tumor immediately after hyperthermia was 2.2 times greater than that of unheated skin and returned to near normal values by 3 h after heating. Tumor-bearing rats received CDDP 1 h before, at the beginning of, at the end of, and 1 h after hyperthermia administration. The CDDP plasma concentration versus time profiles for rats did not vary statistically between treatment groups. Two h after CDDP administration, the mean tumor CDDP concentration of the rats which received drug at the beginning of hyperthermia was statistically greater (P less than 0.05) than tumor CDDP concentrations in rats which received drug at the end of heat treatment. The latter group was given CDDP when tumor blood flow was the greatest; however, mean tumor drug concentration was lowest of all the groups. The mean drug concentration in tumor tissues of rats which received drug 1 h after hyperthermia was comparable to rats which received drug at the beginning of hyperthermia. This suggests that drug delivery or uptake in tumors may be altered when local hyperthermia is administered concurrently or sequentially.  相似文献   
27.
This paper examines the effect of patient age, tumour grade and extent of surgery on the outcome of treatment of 278 patients with high grade malignant gliomas referred to the Queensland Radium Institute between 1980 and 1987. The aim was to determine whether the extent of surgical resection alters survival rates. The extent of surgery had no effect on survival except for those patients with grade 3 tumours in whom a total excision was possible. Those in whom only a biopsy was done did not have a worse prognosis. Grading was found to be of importance, as patients with grade 3 tumours had a better survival than those with grade 4 tumours. In grade 4 tumours, those under 30 years of age had a better survival than those over 30 years, whereas with grade 3 tumours there was a gradation of age effect (under 40 years best, then 40–49 years, and those 50 years and over doing worst).  相似文献   
28.
29.
30.
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