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   2063篇
  免费   162篇
  国内免费   7篇
耳鼻咽喉   20篇
儿科学   75篇
妇产科学   59篇
基础医学   259篇
口腔科学   75篇
临床医学   160篇
内科学   505篇
皮肤病学   37篇
神经病学   130篇
特种医学   51篇
外科学   356篇
综合类   43篇
一般理论   1篇
预防医学   116篇
眼科学   35篇
药学   188篇
中国医学   6篇
肿瘤学   116篇
  2023年   20篇
  2022年   42篇
  2021年   84篇
  2020年   55篇
  2019年   98篇
  2018年   105篇
  2017年   68篇
  2016年   66篇
  2015年   65篇
  2014年   102篇
  2013年   109篇
  2012年   110篇
  2011年   150篇
  2010年   117篇
  2009年   82篇
  2008年   101篇
  2007年   103篇
  2006年   102篇
  2005年   65篇
  2004年   67篇
  2003年   80篇
  2002年   71篇
  2001年   39篇
  2000年   36篇
  1999年   28篇
  1998年   17篇
  1997年   10篇
  1996年   10篇
  1995年   14篇
  1994年   6篇
  1993年   8篇
  1992年   21篇
  1991年   14篇
  1990年   16篇
  1989年   13篇
  1988年   15篇
  1987年   5篇
  1986年   7篇
  1985年   7篇
  1984年   11篇
  1983年   7篇
  1982年   6篇
  1981年   5篇
  1979年   10篇
  1978年   11篇
  1974年   5篇
  1973年   5篇
  1972年   5篇
  1969年   8篇
  1967年   4篇
排序方式: 共有2232条查询结果,搜索用时 15 毫秒
1.
2.
3.
BackgroundHuman studies on exercise, cognition, and apolipoprotein E (APOE) genotype show that ε4 carriers may benefit from regular physical activity.MethodsWe examined voluntary wheel-running, memory, and hippocampal plasticity in APOE ε3 and APOE ε4 transgenic mice at 10–12 months of age.ResultsSedentary ε4 mice exhibited deficits in cognition on the radial-arm water maze (RAWM), a task dependent on the hippocampus. Six weeks of wheel-running in ε4 mice resulted in improvements on the RAWM to the level of ε3 mice. Hippocampal brain-derived neurotrophic factor (BDNF) levels were similar in ε3 and ε4 mice, and after exercise BDNF was similarly increased in both ε3 and ε4 mice. In sedentary ε4 mice, tyrosine kinase B (Trk B) receptors were reduced by 50%. Exercise restored Trk B in ε4 mice to the level of ε3 mice, and in ε4 mice, exercise dramatically increased synaptophysin, a marker of synaptic function.ConclusionsOur results support the hypothesis that exercise can improve cognitive function, particularly in ε4 carriers.  相似文献   
4.
5.
This study evaluates the sensitivity and specificity of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against Mycobacterium tuberculosis antigen. Twenty seven of the 35 patients with pulmonary tuberculosis had positive serology with an antibody titre of 10 nineteen of them had positive serology with an antibody titre of 100. All the 27 patients with positive serology were either smear or culture positive or both. Twenty six of the 35 control group had negative serology and 9 had positive serology with an antibody titre of 10. The test has a sensitivity of 77.14% and a specificity of 74.29%.  相似文献   
6.
Serum samples were collected from 40 patients with enlarged lymph nodes. Lymph node and bone marrow biopsies were performed and processed as usual. Tumor necrosis factor-alpha (TNF alpha) was determined in the sera by factor test human TNF alpha ELISA kit. Histopathological studies of lymph node and bone marrow biopsies were evaluated. The data obtained from this study showed that bone marrow was involved in only 5 patients and their TNF showed the lowest level in this study with a mean level 50 pg/ml. The highest level of TNF occurred in cases with granulomatous lymphadenitis (124 pg/ml) followed by reactive lymphadenitis (105 pg/ml). It can be considered that TNF reflects the immune status of the patient and its study in the serum can be of help in evaluating the progress of the disease. An extended study is need to evaluate the role of TNF-alpha as a prognostic marker in malignancy.  相似文献   
7.
Neuroprotective effect of memantine demonstrated in vivo and in vitro   总被引:3,自引:0,他引:3  
The purpose of the present study was to test whether the anticonvulsant, memantine (1-amino-3,5-dimethyladamantane), can protect neurons against hypoxic or ischemic damage. To this end, we used a rat model of transient forebrain ischemia and cultured neurons from chick embryo cerebral hemispheres. Ischemia was induced for 10 min by clamping both carotid arteries and lowering the mean arterial blood pressure to 40 mm Hg; the rats were allowed to recover for 7 days. Cultured neurons were made hypoxic with 1 mmol/l NaCN added to the incubation medium for 30 min followed by a recovery period of 3 days. The possible effects of memantine were compared with those produced by a typical non-competitive NMDA antagonist, dizocilpine. Similar effects were obtained with both drugs. The drugs reduced the damage caused by transient ischemia to neurons of the hippocampal CA1 subfield. Memantine (10 and 20 mg/kg) had a dose-dependent effect when administered intraperitoneally to the rats 1 h before ischemia. Dizocilpine was active in this model at a dosage of 1 mg/kg. When administered after ischemia, 10 mg/kg memantine significantly protected CA1 neurons against ischemic damage. Furthermore, the drugs protected cultured neurons against hypoxic damage. The lowest effective concentration was 0.1 mumol/l for dizocilpine and 1 mumol/l for memantine. Thus, memantine possesses neuroprotective activity but is less potent than dizocilpine.  相似文献   
8.
9.
10.
The study investigates the correlation between oocyte maturity and fertilization and a variety of hormonal parameters in follicular fluid and ovarian granulosa cells. A methodology for purification of granulosa cells from contaminating blood cells is also established. A total of 63 follicular aspirates were collected at oocyte retrieval from 30 women superovulated using the long luteinizing hormone- releasing hormone (LHRH analogue)/human menopausal gonadotrophin regimen. Oestradiol, progesterone, testosterone and human chorionic gonadotrophin (HCG) were quantified in follicular fluid and granulosa cells were immunostained for human chorionic gonadotrophin. Immunopurification of granulosa cells from contaminating blood cells was performed. HCG in follicular fluid was significantly high in follicles yielding immature (grade 3) oocytes (P=0.002); there was no correlation with fertilization. Aspirates from follicles containing mature (grade 1) oocytes and oocytes that subsequently fertilized had significantly more granulosa cells immunobound to HCG (P < 0.001, P=0.02). Moreover, the immunomagnetic purification technique provided >98% pure population of granulosa cells. The data demonstrate that HCG in follicular fluid and on granulosa cells may help to predict oocyte maturity and fertilization. Furthermore, immunomagnetic beads provide a reliable procedure for the purification of ovarian granulosa cells.   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