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   4210篇
  免费   252篇
  国内免费   23篇
耳鼻咽喉   29篇
儿科学   44篇
妇产科学   28篇
基础医学   499篇
口腔科学   105篇
临床医学   231篇
内科学   1068篇
皮肤病学   34篇
神经病学   310篇
特种医学   99篇
外科学   1115篇
综合类   25篇
预防医学   176篇
眼科学   79篇
药学   199篇
中国医学   9篇
肿瘤学   435篇
  2023年   29篇
  2022年   43篇
  2021年   74篇
  2020年   47篇
  2019年   67篇
  2018年   87篇
  2017年   79篇
  2016年   89篇
  2015年   84篇
  2014年   111篇
  2013年   145篇
  2012年   204篇
  2011年   232篇
  2010年   139篇
  2009年   130篇
  2008年   213篇
  2007年   238篇
  2006年   206篇
  2005年   262篇
  2004年   235篇
  2003年   215篇
  2002年   242篇
  2001年   108篇
  2000年   91篇
  1999年   99篇
  1998年   52篇
  1997年   57篇
  1996年   47篇
  1995年   41篇
  1994年   35篇
  1993年   29篇
  1992年   69篇
  1991年   83篇
  1990年   92篇
  1989年   74篇
  1988年   72篇
  1987年   67篇
  1986年   65篇
  1985年   46篇
  1984年   42篇
  1983年   41篇
  1982年   11篇
  1981年   12篇
  1980年   4篇
  1979年   20篇
  1978年   12篇
  1977年   13篇
  1975年   4篇
  1967年   4篇
  1966年   9篇
排序方式: 共有4485条查询结果,搜索用时 15 毫秒
61.
Although important roles of dietary n-3 fatty acids in the prevention of coronary heart disease (CHD) have been suggested, long-term effects of dietary alpha-linolenic acid (ALA, 18:3n-3) have not yet been established under controlled conditions. We tested whether a moderate increase of dietary ALA affects fatty acids composition in serum and the risk factors of CHD. Oxidized LDL (OxLDL) was directly measured by ELISA using antibody specific to OxLDL. By merely replacing soybean cooking oil (SO) with perilla oil (PO) (i.e., increasing 3 g/d of ALA), the n-6/n-3 ratio in the diet was changed from 4:1 to 1:1. Twenty Japanese elderly subjects were initially given a SO diet for at least 6 mo (baseline period), a PO diet for 10 mo (intervention period), and then returned to the previous SO diet (washout period). ALA in the total serum lipid increased from 0.8 to 1.6% after 3 mo on the PO diet, but EPA and DHA increased in a later time, at 10 mo after the PO diet, from 2.5 to 3.6% and 5.3 to 6.4%, respectively (p<0.05), and then returned to baseline in the washout period. In spite of increases of serum n-3 fatty acids, the OxLDL concentration did not change significantly when given the PO diet. Body weight, total serum cholesterol, triacylglycerol, glucose, insulin and HbA1c concentrations, platelet count and aggregation function, prothrombin time, partial thromboplastin time, fibrinogen and PAI-1 concentration, and other routine blood analysis did not change significantly when given the PO diet. These data indicate that, even in elderly subjects, a 3 g/d increase of dietary ALA could increase serum EPA and DHA in 10 mo without any major adverse effects.  相似文献   
62.
Carcinogen-resistant inbred DRH rat strain was established from closed colony Donryu rats in the presence of 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB). Despite using 3'-Me-DAB during the stage of selection, the DRH rats developed normally and did not show any spontaneous tumor at over 1 year of age. In the present study, we examined the polymorphism in mannose 6-phosphate/insulin-like growth factor 2 receptor (M6p/Igf2r) gene and found that the DRH rat showed CCC (Proline)-type polymorphism in exon 48 and the Donryu rat had GCC (Alanine) sequence. Since the DRH rat was developed from the Donryu rat, we examined whether this polymorphism in exon 48 of M6p/Igf2r gene was due to mutation that occurred at the stage of selection in the presence of 3'-Me-DAB, using several other laboratory and wild rats. We detected the presence of polymorphism at the same site of the M6p/Igf2r gene among these rats. It is likely that the polymorphism in exon 48 of the M6p/Igf2r gene is present broadly in rats since ancient times and not due to the mutation during the course of selection unless this site is a hot spot for chemical carcinogens.  相似文献   
63.
Lethality and physiological disorders induced by tritium beta particles were studied in rats. Newborn CD/Crj rats received i.p. HTO saline at 0, 8.14, 16.28, 24.42 and 32.56 MBq/g body weight (BW). At four weeks of age, HTO over 24.42 MBq/g BW was fatal, especially in male rats, but it was not obvious under 16.28 MBq/g BW. Surviving female rats were weaned at four weeks of age and rats were monitored for heart rate and blood pressure (systolic, mean and diastolic) at 13, 23 and 30 weeks of age and sacrificed. The blood pressure significantly increased with the administered doses of HTO. Sclerotic kidneys were frequently observed in hypertensive rats exposed to HTO over 24.42 MBq/g BW. Thickened intermediate layer of artery, infiltrating lymphocytes and atrophic mesangiums were observed in sclerotic kidneys. These results indicate that internal exposure to HTO as infants was induced consequent hypertension in association with sclerotic kidney at sublethal doses.  相似文献   
64.
Adenohypophyses of human newborns contain characteristic psammoma bodies. Their numbers are maximal within 2 weeks of the neonatal period and diminish thereafter. They are very rare in infant pituitaries, seeming to disappear by shrinkage in that there is a significant direct correlation between their number and size. The bodies were found to contain a high concentration of endogenous peroxidase, thus suggesting that the enzyme may be responsible for their disappearance. A statistical majority of psammoma bodies were located within follicular lumens. By immunohistochemistry, the follicular epithelium surrounding psammoma bodies showed immunoreactivity for various pituitary hormones. Light microscopy demonstrated that adenohypophysial cells surrounding psammoma bodies contain randomly, scattered granules or globules exhibiting peroxidase activity. Extrusion of such granules into follicular lumens may play a role in the genesis of the concretions. The conspicuous lamellar nature of the calcified psammoma bodies suggests that waves of calcium deposition occur during their morphogenesis. Despite histologic similarities, the histochemical characteristics of this type of psammoma body differ from those in other organs as well as from the calcification encountered in prolactin (PRL)-producing pituitary adenomas.  相似文献   
65.
Pregnant rats were given 0%-, 5%-, 10%- and 20% ethyl alcohol in drinking water during the gestation period.We evaluated the brain function of pups born of alcohol-administered dams. Learning ability (Sidman avoidance behavior), the amounts of monoamines (noradrenalin, dopamine, serotonin) and metabolites (3,4-dihydroxyphenyl acetic acid [DOPAC], homovanillic acid [HVA] and 5-hydroxyindole acetic acid [5-HIAA])in whole brain were examined for neurobehavioral and neurochemical effects.There was no effect on Sidman avoidance behavior in 56-day-old offspring, but alterations of the amounts of monoamines and their metabolites were observed even in 66-day-old offspring as a result of the dams' exposure to ethanol during pregnancy.  相似文献   
66.
The murine Lewis lung carcinoma 3LL cells give rise to spontaneous and experimental lung metastasis in C57BL/6 mice. Tumor cells maintained by serial subcutaneous transplantation in mice retain their ability to form lung metastasis, while cells carried in vitro loose metastatic potential with time. In order to obtain the non-metastatic subline, 3LL cells selected for its high lung colonization potential was grown continuously in vitro for 24 weeks. The present study was undertaken to characterize the expression of both urokinase-type plasminogen activator (uPA) and urinary trypsin inhibitor (UTI) in the non-metastatic (3LL(-)) and the metastatic (3LL(+)) cells. Both cells were tested on the Matrigel for invasive ability using a modified Boyden chamber and assayed for expression of uPA and UTI. The 3LL(+) cells secreted 5 times more uPA (6.25 mu g per 10(6) cells per 24 h) than the 3LL(-) cells (1.25 mu g per 10(6) cells per 24 h). The 3LL(+) cells, which expressed 2 times more cell-surface receptor-bound enzymatically active uPA (0.32 +/- 0.06 OD405) than the 3LL(-) cells (0.15 +/- 0.03 OD405), had larger amounts of cell-surface receptor-bound uPA. On the other hands, UTI levels in the conditioned media was decreased 25-fold in the 3LL(+) cells (0.05 mu g/10(6) cells/24 h) compared to the 3LL(-) cells (1.25 mu g/10(6) cells/24 h). The 3LL(-) cells expressed significantly higher levels of cell-associated UTI as indicated by a cell ELISA (3LL(+), 0.30 +/- 0.04 OD450; 3LL(-), 1.30 +/- 0.21 OD450) and by Western blot analysis. Metastatic competence in the 3LL(+) tumor model is associated with increased expression and release of uPA, as well as decreased UTI production, consistent with a more invasive phenotype. These data support our hypothesis that UTI may contribute to the inhibition of uPA expression in tumor cells.  相似文献   
67.
A case of Schonlein-Henoch-purpura is presented. The immunofluorescent study of skin lesions of the patient showed granular deposits of IgA and C3 in the blood vessel walls perivascular deposits of plasminogen and diffuse localization of fibrin and fibrinogen in the upper dermis. Complement activation via the alternative pathway through IgA, C3 and plasminogen deposits was suggested.  相似文献   
68.
We held a computer software contest at 38th Congress of the JSA, held in March, 1991. The aim is to encourage the members of the Society to write softwares and to help distribute them, especially as Freewares. We received 25 entries for the contest; two-thirds of these are for computers of NEC PC9801 series and a third are for Macintosh. We received donations 3 million yen worth of instruments and goods for prizes plus some cash, which as prizes were distributed to those who made entries for the contest.Most of these programs have been registered as freewares at various computer networks, including our Ether-Net, one of the common computer network SIGBBSs among Japanese anesthesiologists.(Suwa K, Miyasaka K, Tanaka Y, et al.: Report on the computer software contest at 38th congress of the Japan society of anesthesiology. J Anesth 5: 441–444, 1991)Executive Committee of the Computer Software Contest at 38th Congress of the Japan Society of Anesthesiology  相似文献   
69.
70.
PURPOSE: To evaluate the efficacy and toxicity of a novel combination chemotherapeutic regimen including cisplatin with an oral anticancer agent, S-1 that consisted of tegafur, 5-chloro-2, 4-dihydroxypyridine, and potassium oxonate, for non-small-cell lung cancer (NSCLC) patients. EXPERIMENTAL DESIGN: In this phase II trial, patients with locally advanced and metastatic NSCLC were treated with the oral administration of S-1 at 40 mg/m(2) twice a day for 21 consecutive days while cisplatin (60 mg/m(2)) was administered intravenously on day 8. This schedule was repeated every 5 weeks. RESULTS: Of 56 patients enrolled in the study, 55 patients were eligible and analyzed. The median number of cycles administered was 3 (range, 1-12 cycles). Among these 55 patients, one complete response and 25 partial responses were observed with an overall response rate of 47% (95% confidence interval, 34-61%). The median survival time was 11 months and the 1-year survival rate was 45%. Hematologic toxicities of grades 3 and 4 included neutropenia (29%) and anemia (22%). No grade 4 nonhematologic toxicity was observed. Grade 3 toxicity included anorexia (13%), vomiting (7%), or diarrhea (7%). CONCLUSIONS: S-1 plus cisplatin combination chemotherapy showed a promising effectiveness with acceptable toxicity rates in patients with advanced NSCLC. These results warrant further investigations of this regimen including a randomized controlled trial for its use as a first line treatment for NSCLC.  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