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   1418443篇
  免费   105157篇
  国内免费   4651篇
耳鼻咽喉   17719篇
儿科学   45621篇
妇产科学   37819篇
基础医学   207955篇
口腔科学   37489篇
临床医学   138552篇
内科学   274466篇
皮肤病学   27527篇
神经病学   120275篇
特种医学   51387篇
外国民族医学   369篇
外科学   197641篇
综合类   29707篇
现状与发展   1篇
一般理论   586篇
预防医学   121298篇
眼科学   30811篇
药学   104245篇
  6篇
中国医学   3256篇
肿瘤学   81521篇
  2021年   12577篇
  2019年   13373篇
  2018年   18395篇
  2017年   13787篇
  2016年   14892篇
  2015年   17021篇
  2014年   23610篇
  2013年   35925篇
  2012年   50415篇
  2011年   53422篇
  2010年   30895篇
  2009年   28365篇
  2008年   48601篇
  2007年   51267篇
  2006年   51164篇
  2005年   49320篇
  2004年   47169篇
  2003年   44508篇
  2002年   43050篇
  2001年   61529篇
  2000年   62972篇
  1999年   53036篇
  1998年   15602篇
  1997年   14053篇
  1996年   13726篇
  1995年   13020篇
  1994年   12122篇
  1993年   11394篇
  1992年   41922篇
  1991年   41087篇
  1990年   39715篇
  1989年   37574篇
  1988年   34807篇
  1987年   33919篇
  1986年   32346篇
  1985年   30866篇
  1984年   23292篇
  1983年   19796篇
  1982年   12037篇
  1981年   10511篇
  1979年   20887篇
  1978年   14924篇
  1977年   12147篇
  1976年   11942篇
  1975年   12164篇
  1974年   14848篇
  1973年   14531篇
  1972年   13389篇
  1971年   12443篇
  1970年   11505篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Carnitine, valproate, and toxicity   总被引:1,自引:0,他引:1  
Carnitine is an important nutrient that is present in the diet (particularly in meat and dairy products) and is synthesized from dietary amino acids. It functions to assist long-chain fatty acid metabolism and to regulate the ratio of free coenzyme A to acylcoenzyme A in the mitochondrion. Carnitine deficiency occurs in primary inborn errors of metabolism, in nutritional deficiency, and in various other disorders including antiepileptic drug therapy. Valproate therapy is often associated with decreased carnitine levels and occasionally with true carnitine deficiency. Some experimental and clinical evidence links valproate-induced carnitine deficiency with hepatotoxicity, but this evidence is limited and inconclusive. Carnitine supplementation has been useful in some studies, but these data are also limited. Young children with neurologic disabilities taking multiple antiepileptic drugs may have the greatest risk for carnitine deficiency. Measurement of carnitine levels appears warranted in these patients and in patients with symptoms and signs of possible carnitine deficiency.  相似文献   
992.
993.
The neuroimaging findings in diverse types of juxtasellar pathologic processes are reviewed, with particular emphasis on the role of CT in their diagnosis.  相似文献   
994.
Health status of the underschool children from the second health group, which with having some morphofunctional changes, (503 persons) was studied. The key changes were postural, cardiovascular, neuropsychic changes. The lysozyme level in saliva is the informative index related to the health status of underschool children.  相似文献   
995.
The article deals with reserpine influence on mental and physical working capacity, psychic state and professionally relevant functions of memory and concentration in 36 male patients of 50 +/- 2.0 years of age suffering from arterial hypertension and engaged in professions characterized with extreme neuro-emotional stress conditions ( enterprise managers). It was shown that reserpine induced a stable and significant hypotensive effect, improved the physiological indices and physical working capacity, but hampered the mental and cognitive function activity, concentration and short-term memory. Reserpine cannot be recommended for drug therapy in out-patient departments in the treatment of the patient professionally engaged in stable emotional stress conditions.  相似文献   
996.
997.
This study examined the temporal concordance between the onset of childhood anxiety disorders and the points of onset and ending of child sexual abuse (CSA). Sexually abused children (N = 158) were assessed with structured diagnostic interviews. Onset ages for lifetime prevalence anxiety disorders were combined and sequenced with the onset and ending of sexual abuse. Hazard rates were calculated. Departures from the overall linear hazard trajectory for onsets were modeled using piecewise growth curve analyses. Increases from the overall trajectory were found around the point of sexual abuse onset for most childhood anxiety disorders. Decreases were found around the ending of sexual abuse. The risk for developing new anxiety disorders after the onset of sexual abuse showed a positive dose-effect relation with abuse severity. The findings add support to the idea that CSA can have a direct link to childhood anxiety disorders, apart from confounded vulnerability factors, postabuse events, or stable family background factors. The findings are contrasted with those from cross-sectional partial correlation studies that have suggested that there is little direct connection between sexual abuse and mental health outcomes.  相似文献   
998.
BJ-48, a serine protease from the venom of Bothrops jararacussu, was purified to homogeneity using affinity chromatography on p-aminobenzamidine-agarose followed by HPLC gel filtration. BJ-48 presented 52kDa by SDS-PAGE analysis and 48,036Da by electron spray mass spectrometry. The enzyme was shown to be highly glycosylated with 42% of N-linked carbohydrates composed of Fuc(1):GalN(4):GlcN(5):Gal(1):Man(2) and a high content of sialic acid residues (8-12%). BJ-48 had optimal esterase activity at pH 7.5 and displayed maximum catalytic rate at 50 degrees C. Its hydrolytic activity was strongly inhibited by aprotinin and dithiothreitol while N-tosyl-l-phenylalanine chloromethyl ketone, 6-aminocaproic acid, E-64 and soybean trypsin inhibitor (SBTI) were ineffective. The kinetics of BJ-48 with chromogenic substrates revealed an unprecedented selectivity (10(4)-fold) for Arg over Lys in P1. BJ-48 proved to be a thrombin-like enzyme (TLE) with a specific fibrinogen-clotting activity of 73.4NIH units/mg. The TLE rapidly digested human fibrinogen Bbeta chain, but the Aalpha chain was cleaved specifically to release fibrinopeptide A with k(cat)/K(m)=2.1muM(-1)s(-1). The TLE showed no activity toward other thrombin substrates like protein C, protease-activated receptor-1 or inhibitors such as hirudin and antithrombin. A non-denaturing procedure using PNGase F and neuraminidase followed by hydrophobic interaction chromatography was employed to obtain active BJ-48 forms with variable carbohydrate content. Compared to the native enzyme, total or partially deglycosylated BJ-48 forms presented up to 2-fold reduction in their specific activities upon heating at 55/65 degrees C or treatment with SBTI. These results point out a role for BJ-48 glycosylation in thermostability and controlling the access of some canonical protein inhibitors to the active site.  相似文献   
999.
1000.
Background Oxidative stress and increased inflammation have been reported to be increased in subjects with diabetes and to be involved in the pathogenesis of cardiovascular complications after myocardial infarction (MI). It is well recognized that red wine has antioxidant and anti‐inflammatory activities. We examined the effects of moderate red wine intake on echocardiographic parameters of functional cardiac outcome in addition to inflammatory cytokines and nitrotyrosine (oxidative stress marker), in subjects with diabetes after a first uncomplicated MI. Methods One hundred and fifteen subjects with diabetes who had sustained a first non‐fatal MI were randomized to receive a moderate daily amount of red wine (intervention group) or not (control group). Echocardiographic parameters of ventricular dys‐synchrony, circulating levels of nitrotyrosine, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), interleukin‐18 (IL‐18) and C‐reactive protein (CRP) were investigated at baseline and 12 months after randomization. Results After 1 year of diet intervention, concentrations of nitrotyrosine (P < 0.01), CRP (P < 0.01), TNF‐α (P < 0.01), IL‐6 (P < 0.01) and IL‐18 (P < 0.01) were increased in the control group compared with the intervention group. In addition, myocardial performance index (P < 0.02) was higher, and transmitral Doppler flow (P < 0.05), pulmonary venous flow analysis (P < 0.02) and ejection fraction (P < 0.05) were lower in the control group, indicating ventricular dys‐synchrony. The concentrations of nitrotyrosine, CRP, TNF‐α and IL‐6 were related to echocardiographic parameters of ventricular dys‐synchrony. Conclusions In subjects with diabetes, red wine consumption, taken with meals, significantly reduces oxidative stress and pro‐inflammatory cytokines as well as improving cardiac function after MI. Moderate red wine intake with meals may have a beneficial effect in the prevention of cardiovascular complications after MI in subjects with diabetes.  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