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   31679篇
  免费   2593篇
  国内免费   177篇
耳鼻咽喉   321篇
儿科学   1096篇
妇产科学   724篇
基础医学   3684篇
口腔科学   650篇
临床医学   2976篇
内科学   6731篇
皮肤病学   553篇
神经病学   2443篇
特种医学   1013篇
外科学   4795篇
综合类   806篇
一般理论   14篇
预防医学   2170篇
眼科学   1308篇
药学   2363篇
  1篇
中国医学   132篇
肿瘤学   2669篇
  2023年   223篇
  2022年   353篇
  2021年   758篇
  2020年   482篇
  2019年   709篇
  2018年   821篇
  2017年   578篇
  2016年   670篇
  2015年   769篇
  2014年   1042篇
  2013年   1237篇
  2012年   2056篇
  2011年   2098篇
  2010年   1206篇
  2009年   1055篇
  2008年   1822篇
  2007年   1781篇
  2006年   1662篇
  2005年   1586篇
  2004年   1577篇
  2003年   1395篇
  2002年   1243篇
  2001年   1132篇
  2000年   1026篇
  1999年   878篇
  1998年   311篇
  1997年   240篇
  1996年   215篇
  1995年   218篇
  1994年   191篇
  1993年   172篇
  1992年   513篇
  1991年   480篇
  1990年   439篇
  1989年   403篇
  1988年   363篇
  1987年   337篇
  1986年   332篇
  1985年   327篇
  1984年   223篇
  1983年   206篇
  1982年   143篇
  1981年   106篇
  1980年   111篇
  1979年   162篇
  1978年   95篇
  1977年   105篇
  1976年   70篇
  1974年   85篇
  1973年   71篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
21.
PURPOSE: This study compared the near phoria measurement using the Bernell muscle balance card with and without prism neutralization, using both trial frame and phoropter correction, and compared with the conventional Maddox rod method. METHODS: Forty young normal Chinese adults had their near phoria measured with trial frame correction using the conventional muscle balance card method (method 1). Any deviation was compensated with a prism bar as an alternative approach (method 2). The conventional Maddox rod method (method 3) was also carried out for comparison. These three methods were repeated with phoropter correction and considered as methods 4, 5 and 6. RESULTS: The phorias obtained from these six methods were not significantly different from each other (repeated measures anova, p > 0.05). More than half of the subjects were exophoric. Although the difference in phoria was not significant, phoria measurement using phoropter correction yielded a greater coefficient of variation. CONCLUSIONS: Near phoria measurement using the muscle balance card conducted with trial frame correction was less variable, and was also more natural and similar to a real reading situation. The use of prism for compensation did not affect the phoria results. Exophoria seems to be more common than esophoria in young Chinese adults.  相似文献   
22.
23.
H S U  R Werner  D Wong 《Transplantation》1987,43(4):485-488
Brattleboro rats manifest chronic diabetes insipidus as a result of the genetic deficiency of hypothalamic vasopressin. When basal hypothalamic tissue derived from adult F344 rats was implanted as cell suspensions or tissue blocks in the supraoptic regions of these animals, concentration of urine together with reduced urine output and water intake was observed in some animals. Histologic examination of the grafted brains from the responding animals revealed neuronal cells at the implant sites and vasopressin-staining fibers in the median eminence. This study demonstrates the feasibility of the grafting of adult cerebral tissues to correct a genetic hormonal deficiency.  相似文献   
24.
To determine the prognosis of patients with lymph node metastases from an unknown primary melanoma, we retrospectively reviewed the clinicopathologic features of 188 such patients treated from 1971 through 1986 and compared their records with those of patients with clinical stage II melanoma with known primary lesions. Patients with lymph node metastases from an unknown primary melanoma represented 4.6% of all patients with melanoma treated during that period. The five- and ten-year survival rates were 42% and 40%, respectively (median, 37 months). When stratified by number of tumor-containing lymph nodes, there was no significant difference in survival between patients with an unknown primary melanoma and lymph node metastases and those with clinical stage II melanoma and known primary sites. The prognosis of the former patients is no worse than that of patients with lymph node metastases from a known primary site and should be treated in a comparable manner.  相似文献   
25.
26.
27.
Statin, a HMG-CoA reductase inhibitor, was shown to increase BMP-2 gene expression for bone formation, by blocking the mevalonate pathway in cholesterol production. We investigated the effect of naringin, a flavonoid available commonly in citrus fruits, which was also a HMG-CoA reductase inhibitor, in UMR 106 osteoblastic cell line in vitro. The control group consisted of cells cultured without any intervention for different time intervals (24 h, 48 h, and 72 h), whereas the experimental (naringin) group consisted of cells cultured with naringin of different concentrations (0.001 micromol/L, 0.01 micromol/L, and 0.1 micromol/L) for the same time intervals of the control. Colorimetric Tetrazolium (MTT) assay, total protein content assay, and alkaline phosphatase activity were used to measure the cellular activities. Results for the naringin group showed an increase in MTT assay compared with the control and the effect was dose dependent. At high concentration (0.1 micromol), the increases ranged from 60% to 80%. In the total protein content assay, naringin also showed an increase compared with control and the effect was also dose dependent. At high concentration (0.1 micromol), the increases ranged from 9% to 20%. In the alkaline phosphatase activity assay, naringin at high concentration (0.1 micromol) significantly increased the activity up to 20%. In conclusion, naringin significantly increased bone cell activities in vitro. This is the first study specifically attempted to investigate the effect of naringin on bone cell activities. Besides statin, this provided another example of mevalonate pathway blockage in the cholesterol production pathway by HMG-CoA reductase inhibition will increase the bone cell activities.  相似文献   
28.
Apolipoprotein E (apoE, protein; APOE, gene) is the major lipid-transport protein in the brain and plays an important role in modulating the outcome and regenerative processes after acute brain injury. The aim of the present study was to determine if gene transfer of the epsilon3 form of APOE improves outcome in a murine model of transient focal cerebral ischaemia. Mice received an intrastriatal injection of vehicle, a second-generation adenoviral vector containing the green fluorescent protein gene (Ad-GFP) or a vector containing the APOE epsilon3 gene (Ad-APOE) 3 days before 60 mins focal ischaemia. Green fluorescent protein expression was observed in cells throughout the striatum and subcortical white matter indicating successful gene transfer and expression. ApoE levels in the brain were significantly increased after Ad-APOE compared with Ad-GFP or vehicle treatment. Ad-APOE treatment reduced the volume of ischaemic damage by 50% compared with Ad-GFP or vehicle treatment (13+/-3 versus 29+/-4 versus 27+/-5 mm(3)). The extent of postischaemic apoE immunoreactivity was enhanced in Ad-APOE compared with Ad-GFP or vehicle treated mice. These results show the ability of APOE gene transfer to markedly improve outcome after cerebral ischaemia and suggest that modulating apoE levels may be a potential strategy in human stroke therapy.  相似文献   
29.
Q X Chen  R K Wong 《Brain research》1992,582(2):232-236
Tetraethylammonium (TEA) effects on K currents were examined on either side of the membrane of hippocampal CA1 neurons by means of whole-cell voltage-clamp recording and intracellular perfusion. Recording media contained ion channel blockers to allow the selective activation of voltage-dependent K currents which consisted of a rapidly decaying component (A-current) and a delayed component. Voltage protocols were applied to separate the A-current from the delayed component. Results show that 10 mM extracellular TEA suppressed 50 +/- 11% (S.D., n = 4) of the delayed current at different levels of depolarization but had little effect on the A-current. In contrast 10 mM TEA applied by intracellular perfusion suppressed the A-current by 42 +/- 10% (S.D., n = 4) in addition to inhibiting the delayed currently 55 +/- 15% (S.D., n = 4). Both the intracellular and extracellular actions of TEA on K currents showed no voltage- nor time-dependency. The results suggest that voltage-dependent transient current (A-current) is mediated through a separate group of ionic channels distinct from those that sustained the delayed current. Furthermore, the asymmetrical effects of intracellular and extracellular TEA on the transient current are similar to those described for the A-current in molluscan neurons. This observation supports the notion that the structure of the ion channel mediating the A-current is closely conserved across different species.  相似文献   
30.
Tumor necrosis factor (TNF) was produced in mice bearing Ehrlich ascites tumor (EAT) by priming with zymosan and subsequently challenging with lipopolysaccharide. The optimal conditions for the in vivo production of TNF in treating EAT bearing mice were established. The endotoxin shock induced in mice during TNF production could be minimized by the combined administration of sulindac and mannoheptulose. The endogenous TNF produced could suppress proliferation of EAT cells as well as prolong the survival time of mice bearing small tumors.  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