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   1053134篇
  免费   70873篇
  国内免费   2750篇
耳鼻咽喉   14659篇
儿科学   33487篇
妇产科学   29508篇
基础医学   147079篇
口腔科学   31479篇
临床医学   86241篇
内科学   215970篇
皮肤病学   23117篇
神经病学   84460篇
特种医学   41442篇
外国民族医学   360篇
外科学   161400篇
综合类   20380篇
现状与发展   1篇
一般理论   323篇
预防医学   80618篇
眼科学   23189篇
药学   73008篇
中国医学   2384篇
肿瘤学   57652篇
  2021年   9202篇
  2019年   9461篇
  2018年   13421篇
  2017年   10324篇
  2016年   10741篇
  2015年   12285篇
  2014年   17411篇
  2013年   25412篇
  2012年   35293篇
  2011年   37373篇
  2010年   21781篇
  2009年   20464篇
  2008年   33941篇
  2007年   36146篇
  2006年   35604篇
  2005年   35441篇
  2004年   33813篇
  2003年   32390篇
  2002年   30272篇
  2001年   45348篇
  2000年   46486篇
  1999年   39760篇
  1998年   11357篇
  1997年   10297篇
  1996年   10207篇
  1995年   9415篇
  1994年   9029篇
  1993年   8472篇
  1992年   30381篇
  1991年   29134篇
  1990年   28372篇
  1989年   27337篇
  1988年   25342篇
  1987年   24801篇
  1986年   23857篇
  1985年   22653篇
  1984年   16901篇
  1983年   14369篇
  1982年   8590篇
  1979年   15428篇
  1978年   10760篇
  1977年   9081篇
  1976年   8548篇
  1975年   9485篇
  1974年   11224篇
  1973年   10709篇
  1972年   10107篇
  1971年   9335篇
  1970年   9051篇
  1969年   8429篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
91.
Noninvasive localized proton magnetic resonance spectroscopy (MRS) was used for differential diagnosis of a focal brain lesion in a 2.5-year-old girl. The clinical signs were a mild head tilt and neck pain. Magnetic resonance imaging (MRI) revealed a lesion in the right hemisphere of the cerebellum, but its nature remained obscure. In this lesion quantitative determinations of cerebral metabolites by fully relaxed, short-echo-time proton MRS revealed markedly lowered N-acetylaspartate (NAA) and pronounced elevations of choline-containing compounds (Cho) and myo-inositol (Ins), whereas metabolite concentrations in cortical gray matter and white matter were within normal ranges. The metabolite pattern of the lesion indicated loss of vital neuroaxonal tissue (low NAA) and enhanced glial proliferation (high Cho and Ins), which, together with the MRI morphology, suggested a brain tumor. The diagnosis was established by neurosurgical exploration and total extirpation of the tumor. Histology confirmed an astrocytoma (WHO II). After 2 weeks' recovery the child was discharged with no neurological signs.  相似文献   
92.
93.
94.
Background : Methimazole, an anti-thyroid drug, was recently found to be useful in the treatment of systemic lupus erythematosus and other autoimmune diseases. Moreover, decreased thyroid hormone production is associated with a variety of immunological manifestations, such as reduced activation of CD4+ cells, increased CD8+ cell activity and reduced soluble IL-2 receptors. In the present study we examined the effects of methimazole and propylthiouracil on a rat model of experimental colitis.
Methods : Colitis was induced by intracolonic administration of 30 mg trinitrobenzene sulphonic acid (TNB). Two weeks prior to induction of colitis, rats were treated by either methimaziole (0.04%) or propylthiouracil (0.01%) in drinking water after a week of free access to water. Rats were sacrificed 48 h or 7 days after induction of colitis. The colon was isolated, rinsed with ice-cold water and weighed. Damage was assessed both macroscopically and microscopically and myeloperoxidase (MPO) activity determined.
Results : All treated rats were hypothyroid as manifested by a significant elevation of thyroid stimulating hormone (TSH), by comparison with the control groups (mean -1.82±0.40 versus 0.11±0.02 mmol/L, respectively). The inflammatory response elicited by TNB resulted in severe mucosal damage 48 h after damage induction, which persisted for 7 days. Pre-treatment with either methimazole 0.04% or propylthiouracil 0.01% significantly decreased mucosal damage macroscopically (lesion area, lesion score and segmental weight) microscopically and also significantly decreased MPO level at both time points ( P <0.01).
Conclusions : Methimazole and propylthiouracil significantly reduce mucosal damage and colonic weight in a rat model of colitis. The mode by which they do so remains to be studied.  相似文献   
95.
96.
The results of the in vitro fertilisation programme at Tygerberg Hospital for the period April 1983 to January 1988 are presented. Of the 1117 laparoscopies performed, 825 patients reached the transfer stage. A live-birth rate of 9.3% was achieved. The pregnancy rate after transfer of 4 embryos was 25.9% compared with 15.4% after 2 embryos and 10.8% after 3 embryos (P = less than 0.0001). The multiple pregnancy rate was 2.8% in the group receiving 2 embryos and 11.7% and 10.4% in those receiving 3 and 4 embryos, respectively. Of the 77 successful pregnancies (90 babies), 1 baby died at 34 weeks' gestation as the result of abruptio placentae due to preeclampsia and 1 cot death occurred. The only congenital abnormality encountered was a cleft palate.  相似文献   
97.
Nine hundred and three patients undergoing diagnostic peritoneal lavage (DPL) over a 6-year period were retrospectively reviewed to evaluate the utility of the white blood cell (WBC) count in the lavage fluid. Eleven patients (1.2%) had dialysate WBC counts greater than 500/mm3, with erythrocyte counts less than 10(5)/mm3. Nine of these patients who were lavaged within 4 hours of injury had no intra-abdominal pathology. Two patients, lavaged after 4 hours, demonstrated intra-abdominal injury. Two hundred twenty-three patients (24.7%) had grossly clear dialysate which was not sent for laboratory analysis. None of these patients required laparotomy. We conclude that the WBC count in DPL fluid is of no diagnostic value in victims of blunt abdominal trauma who are lavaged within 4 hours of injury. In addition, laboratory analysis of clear dialysate is not required in these patients.  相似文献   
98.
Patients on long-term haemodialysis suffer from dialysis arthropathy due to the deposition of dialysis amyloid. We investigated the use of 99Tc-labelled methylene diphosphonate bone scans in 17 patients as a possible in vivo diagnostic technique. In most clinically affected joints, with the exception of shoulders and hands, there was increased radioisotope uptake consistent with uptake by periarticular bone. In addition, we describe intense soft-tissue uptake around some clinically affected large joints. In contrast, control groups of patients on haemodialysis without arthropathy and patients without renal failure did not have increased uptake. A semi-quantitative scale of uptake was devised, and the following correlations were significant: pain perception and isotope uptake score in the ankles and feet, and the number of radiological lesions and isotope uptake scores in the wrists and knees. The following sites where the radioisotope might bind in the affected joints are proposed: amyloid deposits, areas of soft-tissue calcification, or areas of increased bone turnover. It is concluded that whereas the scanning technique cannot make a definite diagnosis of amyloid and, therefore, cannot be expected to supersede histological diagnosis, it is a useful adjuvant investigation, of particular importance in those patients unable or unwilling to undergo biopsy.  相似文献   
99.
100.
Cyanoacrylate-based glues have been reported as producing dermatitis and bronchial asthma. The paper describes the case of a patient occupationally exposed to Loctite 406, who developed irritation of the skin and mucosae of the face and late bronchial asthma. Preventive measures for subjects exposed to cyanoacrylic instant glues are discussed.  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