首页 | 官方网站   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   5281篇
  免费   263篇
  国内免费   25篇
医药卫生   5569篇
  2023年   24篇
  2022年   71篇
  2021年   119篇
  2020年   76篇
  2019年   124篇
  2018年   159篇
  2017年   115篇
  2016年   139篇
  2015年   156篇
  2014年   202篇
  2013年   282篇
  2012年   394篇
  2011年   409篇
  2010年   254篇
  2009年   217篇
  2008年   348篇
  2007年   348篇
  2006年   366篇
  2005年   287篇
  2004年   243篇
  2003年   254篇
  2002年   232篇
  2001年   66篇
  2000年   38篇
  1999年   42篇
  1998年   52篇
  1997年   55篇
  1996年   35篇
  1995年   34篇
  1994年   23篇
  1993年   24篇
  1992年   44篇
  1991年   35篇
  1990年   29篇
  1989年   29篇
  1988年   22篇
  1987年   11篇
  1986年   12篇
  1985年   14篇
  1984年   18篇
  1983年   14篇
  1982年   14篇
  1981年   15篇
  1980年   14篇
  1979年   8篇
  1978年   13篇
  1977年   11篇
  1976年   11篇
  1975年   7篇
  1974年   12篇
排序方式: 共有5569条查询结果,搜索用时 15 毫秒
1.
The relation between sexual function and serum free testosterone (fT) levels, which represent the active fraction of circulating testosterone, was evaluated. Two groups of impotent male subjects with mild hypogonadism were treated with oral testosterone undecanoate (TU); these men presented with tT/luteinizing hormone (LH) ratio and tT levels at the lower limits of normal. The first group had serum fT below 6.6 ng/ml, considered the lower normal value, according to our laboratory method, whereas the second group had normal fT limits. Administration of TU improved sexual function only in impotent men with low fT levels, but not in subjects with normal fT levels, even though the tT levels and the tT/LH ratio of the two groups were not significantly different. The results of our study suggest the presence of a minimun serum fT threshold, lying near the lower normal range, which determines the male sexual function. Moreover, serum fT levels were a more sensitive index than tT for identifying impotent men who can be successfully treated with androgens.  相似文献   
2.
A case of cystic lymphangioma of the liver   总被引:1,自引:0,他引:1  
Here is a case report about a cystic lymphangioma of the liver, a rare benign tumor, extremely difficult to diagnose with certainty in spite of the wide range of examinations today available. Surgical intervention is still the most important means to achieve the final diagnosis. The authors also provide a discussion about the pathogenesis and the clinical manifestation of the disease.  相似文献   
3.
Tropical pyomyositis is an infection of muscles mainly presenting in black people, occurring in the trunk and limbs. At Hoima Hospital, Uganda, 58 patients (30 men and 28 women) with a mean age of 21 years have been investigated by ultrasound; a total of 81 lesions were present. Two different characteristic images were found; abscess was present in 65 cases while 16 patients showed a diffuse infiltration among the muscular fibers. These two different images correspond to the two stages of histologic and clinical progression described by other authors. Ultrasound is useful to demonstrate the progression of pyomyositis and to determine when and where to drain any abscess.  相似文献   
4.
The quality of health care systems and processes is becoming a prominent problem and more and more efforts are devoted to define methodologies and tools to measure and assure quality of care. New methods are required to optimize health care processes to guarantee high quality standards within (limited) available resources. Resource optimizations able to preserve the quality of treatments require good models of medical processes. This paper presents LEMMA, a new notation to model medical processes. LEMMA provides physicians with intuitive graphical elements to design their models. At the same time a high level timed Petri net corresponding to the designed model is built automatically. In this way, LEMMA models are ascribed formal semantics and can be executed and analyzed automatically. The dual language approach followed in this paper allows physicians to gain all the benefits of formal methods without being proficient in them. Medical users manage simple graphical elements, while Petri nets ensure formality and validation capabilities. In this way LEMMA mixes formal and informal notations, overcoming the problems of both the approaches. The definition of the notation has been supported by the development of an environment to design LEMMA models. The environment, besides letting us experiment with the notation, has been employed to define and analyze real case studies.  相似文献   
5.
6.
Purpose: To verify the efficacy of ultrasound (US)-guided injection of large amounts of ethanol into large or multiple liver lesions, in a single session under general anesthesia (one-shot PEI) for percutaneous ablation of hepatic tumors. Methods: Twenty-nine patients (27 with 51 hepatocellular carcinoma (HCC) nodules on cirrhosis, diameter range 1.0<+>–<+>9.0 cm; two patients with a single metastasis from the gastroenteric tract, 5.0 and 9.0 cm, respectively, in diameter) were treated with one-shot PEI. Results: The total volume of alcohol delivered per patient ranged from 16 to 210 ml. Mean ethanol volume in all patients was 49 ml. Dynamic computed tomography (CT) examination showed complete necrosis in 41 of 50 lesions. Two patients died of hypovolemic shock due to massive upper gastrointestinal bleeding, 3 and 7 days, respectively, after the interventional procedure. All the remaining patients are alive (follow-up 5<+>–<+>14 months) except one who died of liver failure 5 months after. New HCC nodules occurred in six patients within 6 months and one intralesional relapse was recorded. Conclusion: In this preliminary experience, one-shot PEI is as effective in inducing liver tumor necrosis as traditional PEI; its advantages are shorter treatment time and the capability of treating larger and multiple liver lesions.  相似文献   
7.
In the present study we have investigated the effect of six antibiotics (penicillin G, ceftazidime, cephotaxime, cephoperazon, ampicillin and piperacillin) on the neutrophil cytolytic activity by using a system constituted of phorbol-12-myristate-13-acetate-triggered neutrophils and 51Cr-labelled lymphoblastoid Daudi target cells. The results demonstrate that five of these drugs (ceftazidime, cephotaxime, cephoperazon, ampicillin and piperacillin) are capable of inhibiting the neutrophil cytolytic activity by inactivating the hypochlorous acid (HOCl) generated extracellularly by the myeloperoxidase pathway and crucial to the target cell lysis. Penicillin G had no effect on neutrophil-mediated cytolysis. Thus, these data demonstrate that ceftazidime, cephotaxime, cephoperazon, ampicillin and piperacillin lower the neutrophil-mediated target cell damage by a HOCl-scavenging mechanism, suggesting a possible cytoprotective role for these drugs during infections.  相似文献   
8.
 Styrene is stereoselectively oxidized by cytochrome P450 to its reactive metabolite, styrene oxide. The (R)- and (S)-enantiomers of styrene oxide can be conjugated with glutathione (GSH) to both (R)- and (S)-diastereoisomers of the specific mercapturic acids, N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine (M1) and N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine (M2). Several investigations have indicated different toxic potential of the (R)- and (S)-configurations of styrene oxide and its GSH- and N-acetyl-conjugates. In this study the mercapturic acid diastereoisomers were measured in the urine of rats exposed to styrene in combination with ethanol, a good inducer of styrene metabolism. Male Sprague-Dawley rats were given an isocaloric liquid diet containing ethanol (5% w/v) for 3 weeks. Starting from the 2nd week, the animals were also exposed to styrene vapours (300 ppm, 6 h/day, 5 days/week) in a dynamic exposure chamber. Both the (R)- and (S)-diastereoisomers of the M1 and M2 as well as the conventional biomarkers, mandelic acid (MA) and phenylglyoxylic acid (PGA) were measured in urinary samples. Approximately 30 and 25% reduction of the levels of brain non-protein sulfhydryls (NPS) was observed in the animals given styrene and ethanol, respectively, while the combined ethanol and styrene treatment resulted in a 60% decrease. Ethanol consumption also resulted in higher urinary levels of the M1-R, M1-S and M2 metabolites associated with increased M1-R/S ratio and higher urinary MA excretion compared to animals treated with styrene. These results suggest that the urinary mercapturic acid diastereoisomers may be used as a noninvasive tool to examine stereoselective patterns of styrene metabolism in vivo, as well as their alterations caused by ethanol. These compound-specific mercapturic acids may also be valuable indicators of styrene-induced disorders of GSH homeostasis in nonaccessible organs. Received: 19 December 1995/Accepted: 10 May 1996  相似文献   
9.
A study has been carried out in the apolipoprotein (apo) E-deficient mouse to investigate the activity of lacidipine (a calcium antagonist with antioxidant properties) in inhibiting the development of atherosclerotic lesions; of particular interest were changes in the susceptibility of low-density lipoproteins (LDL) to oxidation. Mice receiving a Western-type diet to accelerate the development of atherosclerosis were treated orally with vehicle or lacidipine at 3 or 10 mg/kg/day for 8 weeks. Lacidipine treatment (at 3 or 10 mg/kg) had no effect on the plasma lipid profile. However, a significant (P < 0.01) dose-related reduction of 43 and 50% of the aortic lesion area in respect to vehicle-treated mice was observed. Moreover, the resistance of mouse plasma LDL to undergo lipid peroxidation was significantly (P < 0.01) increased in apo E-deficient mice treated with lacidipine. The native LDL-like particle, derived from apo E-deficient mice treated with lacidipine, contained significantly lower concentrations of malonyldialdehyde than the vehicle-treated control group (P < 0.01). After exposure to human umbilical vein endothelial cells, LDL-like particle vitamin E levels (expressed as area under the curve; AUC), were significantly higher (P < 0.01) in both the 3 and 10 mg/kg lacidipine-treated groups, in comparison with the vehicle-treated control animals. We conclude that lacidipine reduced the extent of the atherosclerotic area in hypercholesterolaemic apo E-deficient mice, and that this reduction may be associated with the capacity of the drug to decrease the susceptibility of LDL to oxidation.  相似文献   
10.
Caffeine, a non-selective adenosine receptor antagonist, has been suggested as a potential drug to counteract age-related cognitive decline since critical changes in adenosinergic neurotransmission occur with aging. In the present study, olfactory discrimination and short-term social memory of 3, 6, 12 and 18 month-old rats were assessed with the olfactory discrimination and social recognition tasks, respectively. The actions of caffeine (3.0, 10.0 and 30.0 mg/kg, i.p.), the A1 receptor antagonist DPCPX (1.0 and 3.0 mg/kg, i.p.) and the A2A receptor antagonist ZM241385 (0.5 and 1.0 mg/kg, i.p.) in relation to age-related effects on olfactory functions were also studied. The 12 and 18 month-old rats exhibited significantly impaired performance in both models, demonstrating deficits in their odor discrimination and in their ability to recognize a juvenile rat after a short period of time. Acute treatment with caffeine or ZM241385, but not with DPCPX, reversed these age-related olfactory deficits. The present results suggest the participation of adenosine receptors in the control of olfactory functions and confirm the potential of caffeine for the treatment of aged-related cognitive decline.  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-23

京公网安备 11010802026262号