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   4199篇
  免费   207篇
  国内免费   16篇
耳鼻咽喉   39篇
儿科学   38篇
妇产科学   87篇
基础医学   578篇
口腔科学   72篇
临床医学   303篇
内科学   1190篇
皮肤病学   138篇
神经病学   209篇
特种医学   142篇
外科学   759篇
综合类   9篇
预防医学   137篇
眼科学   40篇
药学   283篇
中国医学   11篇
肿瘤学   387篇
  2023年   21篇
  2022年   40篇
  2021年   76篇
  2020年   38篇
  2019年   56篇
  2018年   92篇
  2017年   58篇
  2016年   74篇
  2015年   84篇
  2014年   122篇
  2013年   104篇
  2012年   207篇
  2011年   248篇
  2010年   120篇
  2009年   108篇
  2008年   193篇
  2007年   199篇
  2006年   205篇
  2005年   194篇
  2004年   184篇
  2003年   162篇
  2002年   176篇
  2001年   140篇
  2000年   120篇
  1999年   154篇
  1998年   55篇
  1997年   35篇
  1996年   26篇
  1995年   31篇
  1994年   36篇
  1993年   23篇
  1992年   106篇
  1991年   88篇
  1990年   97篇
  1989年   87篇
  1988年   78篇
  1987年   77篇
  1986年   73篇
  1985年   51篇
  1984年   45篇
  1983年   27篇
  1981年   20篇
  1979年   34篇
  1977年   17篇
  1974年   26篇
  1973年   23篇
  1972年   25篇
  1970年   23篇
  1969年   23篇
  1968年   18篇
排序方式: 共有4422条查询结果,搜索用时 0 毫秒
1.
We report a case of a diaphragmatic hernia after a heart transplant operation. A 43-year-old woman, who underwent orthotropic heart transplantation for hypertrophic cadiomyopathy two year earlier, presented with vomiting and epigastric pain. A computed tomography scan showed that the stomach and transverse colon were dislocated in the left thoracic cavity. We diagnosed left diaphragmatic hernia incarceration and performed laparoscopic repair of the diaphragmatic hernia. A 12 × 8 cm diaphragmatic defect was found intraoperatively on the ventrolateral aspect of the left diaphragm, and the stomach with volvulus had herniated into the thorax through the defect. The hernia was considered to be iatrogenic. The diaphragmatic defect was large, and the diaphragm was thinning. We closed the defect by mesh repair. Laparoscopic mesh repair of the diaphragmatic hernia could be performed safely and with minimal invasiveness.  相似文献   
2.
3.
Anthocyanins, which are responsible for a variety of bright colors (including red, blue, and purple) in fruits, vegetables, and flowers, are consumed as dietary polyphenols. Anthocyanin-containing fruits are thought to decrease coronary heart disease and are used in anti-diabetic preparations. Diabetes is associated with a variety of cardiovascular complications that may be mediated by endothelial dysfunction, and so this study was designed mainly to characterize the influence of a synthesized anthocyanidin derivative (HK-008) over acetylcholine (ACh)-induced relaxation in mesenteric arterial beds isolated from rats. In a glucose-tolerance test in intact rats, HK-008 (30 mg/kg) reduced the glucose level as effectively as the same dose of glibenclamide. The aortic relaxation induced by pinacidil (an ATP-sensitive potassium channel opener) was greatly inhibited by glibenclamide (10 microM), and also significantly inhibited by HK-008 (10 microM). Interestingly, the ACh-induced relaxation in the perfused, preconstricted mesenteric arterial bed was significantly enhanced by HK-008 (10 microM), and this enhancement was significantly attenuated by indomethacin (10 microM). The ACh-induced mesenteric relaxation was impaired by an increase in oxidative stress, viz. superoxide-generating treatment [xanthine oxidase (XO; 0.1 U/ml) plus hypoxanthine (HX; 10 microM)]. However, this impairment was strongly suppressed by HK-008 (10 microM). These results suggest that HK-008 increases endothelium-induced relaxation by suppressing oxidative stress or modulating prostanoids signaling. This compound may therefore be useful against certain cardiovascular disorders.  相似文献   
4.
Abstract: The adsorptive characteristics of 5 dialysis membranes for recombinant human erythropoietin (EPO) were studied in vitro in a closed circuit system. For 120 min, EPO added with bovine serum was significantly adsorbed by polymethylmetacrylate (PMMA) and polyacry–lonitrile (PAN) membranes but not by Cuprophan, ethylene vinyl alcohol (EVAL), or polysulfone (PS) membranes. In addition the EPO adsorptive rate, as well as that of β2–microglobulin (β2–MG), was greater with a PMMA membrane than with a PAN membrane. EPO was not detected in the ultrafiltrate at 15 min with 5 membranes. These results indicate that EPO was eliminated by membrane adsorption only with some dialysis membranes.  相似文献   
5.
BACKGROUND: Cyanide is a toxic agent, and its detoxification product, thiocyanate, may be a major pathogenetic substance in uraemia. Recent studies examining the myeloperoxidase(MPO)/thiocyanate system have suggested a link between thiocyanate and atherosclerosis. However, inaccuracies in conventional assays for cyanide and thiocyanate have limited the understanding of their metabolism in haemodialysis (HD) patients. METHODS: We used high-performance liquid chromatography to measure cyanide in erythrocytes and thiocyanate in plasma in 43 HD patients and in a group of 46 healthy controls that included 15 current smokers. To clarify the metabolic conversion of cyanide to thiocyanate in uraemic patients, we also measured cysteine and sulfate. We then used stepwise regression analysis to analyse factors that determine erythrocyte cyanide and plasma thiocyanate. RESULTS: Mean cyanide and thiocyanate were significantly greater in HD patients than in non-smoking controls. However, cyanide was far below lethal concentrations in dialysis patients. Thiocyanate was six to seven times greater in HD patients than in non-smoking controls, and decreases in thiocyanate following dialysis were only 19.3+/-3.5%. Multiple regression analysis showed a positive correlation between cyanide and thiocyanate in controls, but a negative correlation in HD patients. In patients, an inverse relationship between thiocyanate and BUN was also observed. CONCLUSIONS: The elevation of thiocyanate in patients undergoing dialysis probably is secondary to both limited efficiency of HD and deranged metabolism of cyanide and thiocyanate. Because thiocyanate is a preferred substrate for MPO, it may play a role in uraemic complications including cardiovascular events.  相似文献   
6.
7.
To evaluate the acute effects of anti-asthmatic drugs in vitro, we examined the modulation of various anti-asthmatic drugs in therapeutic concentrations on PAF-induced human eosinophil chemotaxis. Aminophylline (20 micrograms/ml) and Isoproterenol (10 nM) inhibited PAF (3 X 10(-8) M)-induced eosinophil chemotaxis nearly 30%, whereas no inhibitory effects were observed by Dexamethasone (0.1 microM), Tranilast, Ketotifen or Azelastine. Aminophylline (20 micrograms/ml) also inhibited LTB4 (3 X 10(-8) M)-induced eosinophil chemotaxis nearly 30%, whereas it did not inhibit chemotaxis induced by zymosan (5 mg/ml)-activated serum. These results indicate that anti-asthmatic drugs except for aminophylline and isoproterenol, when used acutely in therapeutic concentrations, have no striking inhibitory effects on PAF-induced eosinophil chemotaxis. These results further suggest the possibility that there are different mechanisms in eosinophil chemotaxis induced by PAF, LTB4 or by C5a.  相似文献   
8.
Proteins from 21 cerebrospinal fluid (CSF) samples (14 derived from neurological cases and 7 from normal individuals) and 15 serum samples (11 from neurological cases and 4 from normal individuals) were analyzed by two-dimensional electrophoresis. Protein mapping revealed a very acidic protein (Ac-P) at about pH 3.5 in the 71% of CSF samples from neurological cases. However, no serum sample contained Ac-P. Ac-P was isolated and purified, and determined to be a glycoprotein containing a large amount of carbohydrate, with molecular weight 42,000 and isoelectric point 2.7-3.3. The amino acid composition of Ac-P was consistent with alpha 1-acid glycoprotein (AGP), and Ac-P was responsive to a commercial anti-AGP antiserum in the radial immunodiffusion test. The known polymorphism of AGP suggests some differences in physicochemical properties such as molecular weight and isoelectric point between AGP in serum and in CSF. Quantitative analysis of Ac-P (AGP) and total protein levels in CSF showed a partial interdependence. Ac-P may be a useful marker for detecting a pathological conditions of the central nervous system.  相似文献   
9.
To investigate the mechanism underlying increased endothelin-1 (ET-1) release in diabetic rats, we administered L-arginine chronically to streptozotocin (STZ)-induced diabetic rats. The plasma concentrations of glucose, ET-1 and NOx (NO2- + NO3-) were all significantly raised at 10 weeks after the STZ injection. Chronic administration of L-arginine resulted in a significantly higher plasma NOx concentration and a significantly lower plasma ET-1 level at 10 weeks compared with the untreated diabetic group. ET-1 induced a biphasic vasodilator/vasoconstrictor response in the perfused isolated mesenteric arterial beds from all groups. The vasodilatation was significantly greater in diabetic rats than in age-matched controls. Chronic oral L-arginine administration had no significant effect on the enhanced ET-1-induced vasodilatation seen in the untreated diabetic rats. The vasoconstrictions induced by ET-1 and methoxamine were significantly attenuated in STZ-diabetic rats. The attenuated vasoconstrictor response to ET-1, but not that to methoxamine, was further attenuated by chronic treatment with L-arginine. We conclude that since chronic L-arginine administration not only reduced the increase in plasma ET-1 levels but also further attenuated the ET-1-induced vasoconstriction without affecting the change in vasodilatation, chronic L-arginine administration could be valuable for the treatment of the symptoms of diabetic mellitus related to ET-1.  相似文献   
10.
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