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   756篇
  免费   27篇
耳鼻咽喉   3篇
儿科学   7篇
妇产科学   9篇
基础医学   50篇
口腔科学   22篇
临床医学   68篇
内科学   283篇
皮肤病学   4篇
神经病学   33篇
特种医学   16篇
外科学   199篇
综合类   4篇
预防医学   6篇
眼科学   15篇
药学   21篇
中国医学   1篇
肿瘤学   42篇
  2022年   2篇
  2021年   6篇
  2020年   7篇
  2019年   3篇
  2018年   8篇
  2017年   6篇
  2016年   12篇
  2015年   15篇
  2014年   6篇
  2013年   15篇
  2012年   29篇
  2011年   43篇
  2010年   17篇
  2009年   24篇
  2008年   39篇
  2007年   44篇
  2006年   53篇
  2005年   44篇
  2004年   41篇
  2003年   55篇
  2002年   43篇
  2001年   27篇
  2000年   27篇
  1999年   25篇
  1998年   7篇
  1997年   5篇
  1996年   4篇
  1995年   3篇
  1994年   5篇
  1993年   8篇
  1992年   8篇
  1991年   12篇
  1990年   10篇
  1989年   14篇
  1988年   13篇
  1987年   13篇
  1986年   19篇
  1985年   10篇
  1984年   9篇
  1983年   14篇
  1982年   6篇
  1979年   6篇
  1978年   2篇
  1977年   4篇
  1975年   4篇
  1974年   2篇
  1973年   2篇
  1972年   2篇
  1970年   2篇
  1913年   1篇
排序方式: 共有783条查询结果,搜索用时 15 毫秒
1.
A new method of determining urinary polyamine concentration was compared with other techniques, namely, high pressure liquid chromatography (HPLC) and a polyamine test-enzyme kit. The values obtained by the new method, HPLC, and polyamine test-enzyme kit correlated well for all the fractions: diamine, spermidine and spermine. The correlation between the new method and the polyamine test-enzyme kit gave r = 0.9702, y = 1.1359x + 5.1266 (n = 48).  相似文献   
2.
3.
A 38-year-old female presented with a lower abdominal mass. During the operation the mass was found to be retroperitoneal and was excised. Gross examination revealed a mucin-containing cystic lesion with a mural nodule. On microscopic examination, the cystic areas were lined by an invasive mucinous adenocarcinoma and the nodule was composed of an anaplastic sarcomatoid tumor that was immunoreactive for cytokeratin. This present case is the 21st example of a retroperitoneal primary mucinous cystadenocarcinoma and the fourth with a mural nodule. Three of four cases with a mural nodule, including our case, had a rapidly fatal outcome.  相似文献   
4.
Cultured human arterial smooth muscle cells produced an immunologically specific renin-like enzyme. The renin-like enzyme in the culture medium was mostly an inactive form; the proportion of the active form in the cell was 30 to 75%. Phorbol 12-myristate 13-acetate, N'-O'-dibutylyladenosine 3', 5'-monophosphate and isoproterenol with theophylline increased the renin-like enzyme in the medium and in the cell, dose dependently. Endothelial cell growth supplement also increased the renin-like enzyme produced by cultured vascular smooth muscle cells, and heparin promoted the effects of endothelial cell growth supplement. The existence of the regulation of the renin-like enzyme produced by cultured vascular smooth muscle cells strongly suggests the existence of a local renin angiotensin system in human vascular walls.  相似文献   
5.
A 48-year-old man had histologically demonstrated cardiac involvement associated with progressive muscular dystrophy. On coronary arteriography, numerous vascular communications between the coronary arteries and the left ventricular chamber were found. These vascular communications are considered to be the arterioluminal vessels. This is the first report of a case of progressive muscular dystrophy with numerous arterioluminal vessels.  相似文献   
6.
Abstract: Two autopsied female sibling cases of sudanophilic leukodystrophy are reported. Case A and case B were the second and third of seven siblings, and a sister and a brother died from severe progressive neurological disease with similar symptoms. Consanguineous marriages were noted in the family of both cases through the past three generations. Case A gradually developed intellectual deterioration and tetraplegia at the age of 29, progressed to akinetic mutism within one year and thereafter survived for 14 years. Neuropathologically, a severe atrophy and degeneration were noted in the white matter of the whole cerebrum, sparing the subcortical U-fibers. Myelin and axons were severely damaged with peripheral astrocytic gliosis. Case B developed similar clinical symptoms at the age of 20 and survived for 7 years in the state of akinetic mutism. Similar postmortem findings as those of case A were found in the white matter of the cerebrum with formation of sudanophilic breakdown products and with thick fibrillary gliosis. The pyramidal tract was completely degenerated. There was no accumulation of abnormal lipid in the brains of both cases.  相似文献   
7.
8.
Summary.  Matrix (M) and nonstructural (NS) genes of thirteen equine H3N8 and H7N7 influenza viruses were sequenced and analyzed from an evolutionary point of view. The M and NS genes of H3N8 viruses isolated between 1989 and 1993 evolved into two minor branch clusters, including isolates from Europe and the American continent, respectively. It was noteworthy to reveal that the nucleotide sequences of the M and NS genes of an earlier American strain showed highest homology to those of recent European viruses. “Frozen evolution” was observed in the M and NS genes of A/eq/LaPlata/1/88. It was also evident that the NS gene of an H7N7 virus from 1977 was very similar to that of a 1979-H3N 8 virus, while the M gene was closest phylogenetically to that of the earliest H7N7 virus isolated in 1956. Furthermore, the M2 protein of A/eq/Newmarket/1/77 virus contained a carboxyl terminal deletion of three amino acids. The evolutionary rates of the M and NS genes of H3N8 equine influenza viruses were estimated to be 5.4 × 10−4 and 5.1 × 10−4 substitutions per site per year, respectively, which were slower than those of human viruses. Received November 21, 1997 Accepted March 9, 1998  相似文献   
9.
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   
10.
Morphogenesis of the frontal organ in Bufo bufo was examined under transmission electron microscope. Many remarkable similarities to the frontal organ of other Amphibia Anura are observed. It originates from a diverticulum in the dorsal region of the neural tube. It is egg-shaped, has an eccentric lumen, and is made up of three kinds of cells: 1) photoreceptors, which protrude into the lumen; 2) supportive cells; and 3) ganglion cells, which make synaptic contact with the photoreceptors. Peculiar to Bufo bufo is the melanin-like pigments around the light-sensitive part of the photoreceptors. These pigments may prevent light dispersion. The frontal organ in Bufo bufo starts degenerating during the early premetamorphic stages.  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