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   368353篇
  免费   58646篇
  国内免费   9087篇
耳鼻咽喉   4094篇
儿科学   8668篇
妇产科学   3251篇
基础医学   56481篇
口腔科学   11762篇
临床医学   35009篇
内科学   70431篇
皮肤病学   7014篇
神经病学   35399篇
特种医学   20192篇
外国民族医学   81篇
外科学   34161篇
综合类   35014篇
现状与发展   26篇
一般理论   14篇
预防医学   20781篇
眼科学   6603篇
药学   44327篇
  65篇
中国医学   10764篇
肿瘤学   31949篇
  2024年   740篇
  2023年   5291篇
  2022年   11374篇
  2021年   15152篇
  2020年   15648篇
  2019年   19476篇
  2018年   18619篇
  2017年   19456篇
  2016年   18563篇
  2015年   19847篇
  2014年   25714篇
  2013年   26804篇
  2012年   24064篇
  2011年   26115篇
  2010年   22023篇
  2009年   19206篇
  2008年   19515篇
  2007年   17140篇
  2006年   15416篇
  2005年   13654篇
  2004年   12014篇
  2003年   10602篇
  2002年   8835篇
  2001年   7248篇
  2000年   5621篇
  1999年   3923篇
  1998年   3454篇
  1997年   3337篇
  1996年   2963篇
  1995年   2630篇
  1994年   2429篇
  1993年   2027篇
  1992年   1738篇
  1991年   1637篇
  1990年   1385篇
  1989年   1222篇
  1988年   1138篇
  1987年   1005篇
  1986年   916篇
  1985年   1334篇
  1984年   1284篇
  1983年   896篇
  1982年   957篇
  1981年   765篇
  1980年   682篇
  1979年   537篇
  1978年   370篇
  1977年   322篇
  1976年   277篇
  1975年   180篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
991.
992.
Single photon emission computerized tomography (SPECT) is now widely used as one of the tools in evaluating cerebral blood flow (CBF). The authors report the CBF changes in childhood hydrocephalus. Five pediatric cases studied by 123I-IM SPECT in children are presented. The authors counted radioactivities both in early and delayed images in each patient, and calculated the reabsorption ratio (RR). Two negative-RR cases and three positive-RR cases were found. All of the negative-RR patients had a poor prognosis, while all of the positive-RR patients had a favorable outcome.  相似文献   
993.
PHARMACOKINETICSOFCUPRIC-BIS(SALICYLALDEHYDE-2-FURANTHIOCARBOXY-HYDRAZONATE)DICHLORIDE(CSFTCH)INRABBITS¥GaoYunsheng;ZhuYuyun(...  相似文献   
994.
Seven middle-aged men with manifest type II diabetes mellitus underwent an endurance training programme for 10–15 weeks. The maximal aerobic capacity, as well as the endurance capacity, was improved by 10% (p<0.05). The intramuscular glycogen store increased by more than 80% (p<0.05) from 350 μmol/g dw (dry weight), and the activities of citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase increased by more than 50% (p<0.05) and 30% (p<0.05). The activity of glycogen synthase was decreased by approximately 20% (p<0.05), whereas lactate dehydrogenase remained unchanged. Capillaries/fibre and fibre area increased by more than 50% (p<0.05) and 30% (p<0.05) leaving the area of supply constant. Training did not influence fasting blood lipids and glucose, glycosylated hemoglobin, oral glucose tolerance, and insulin response to an oral glucose load measured 72 hours post-exercise. It is concluded that patients with manifest type II diabetes, as normoglycaemic individuals, adapt to physical training. However, no persistent effect on glucohomeostasis and lipaemia is produced by short-term training in the diabetic patients.  相似文献   
995.
The technique of quantitative autoradiography was used to examine the effects of Huntington's disease (HD) and schizophrenia on the organization of striatal dopamine (DA) D1 and D2 receptors. Whereas the striatum of HD cases showed a reduction in the density of D1 ([3H]SCH 23390) and D2 ([3H]spiroperidol) receptors, the patterning of D2 receptor loss did not match that of the D1 receptor loss. The HD loss of D1 D1 receptors (65%) is far greater than the loss of D2 receptors (28%). Whereas there was a dorsal-ventral gradient of effect on both receptor subtypes, the effects of HD on D2 receptors in the ventral putamen (PUT) and nucleus accumben septi (NAS) were minimal. Similarly, muscarinic M1 and M2 receptors demonstrate different patterns of alteration in HD. The M2 subtype, labeled with [3H]N-methylscopolamine (in the presence of excess pirenzepine to occlude M1 sites), was depleted far more than the M1 receptor subtype, labeled with [3H]pirenzepine. Although the effects of HD on [3H]mazindol labeling of DA terminals were more heterogeneous, there appeared to be a relative preservation of this afferent input to the striatum of the HD cases. In the schizophrenic cases, our autoradiographic studies confirm previous reports of an elevation of D2 receptor density in the striata of many schizophrenics. This increase was evident even though two of the three cases were known to have not been treated with neuroleptics, and the third case may also have been drug naive. However, the increase was far greater in the NAS (164%) and ventral PUT (173%) than more dorsally in the striatum (68%). The density of D1 receptors and DA terminals labeled with [3H]mazindol in the striatum of schizophrenics was not significantly different from that of control cases. Thus in both HD and schizophrenia, the ratio of D2/D1 receptors is altered in favor of the D2 population, particularly in the NAS.  相似文献   
996.
The 11C-labelled benzodiazepine antagonist Ro 15–1788 (flumazenil) and positron emission tomography (PET) were used to determine quantitative characteristics of benzodiazepine receptor binding in the neocortex of healthy young men. Saturating doses of unlabelled flumazenil administered i.v., before or together with the ligand-reduced 11C-flumazenil accumulation in the neocortex by about 90 per cent. Saturating doses of unlabelled flumazenil had little effect on the accumulation of radioactivity in the benzodiazepine receptor-poor regions such as pons or white matter. By giving graded doses of unlabelled flumazenil together with the tracer, saturation isotherms were obtained allowing the calculation of receptor density (Bmax) and equilibrium dissociation constant (Kd) values on the basis of certain assumptions Bmax values were in the order of 90 pmol/g and Kd values in the order of 10 nM in the neocortex. Scatchard and Hill plots of the radioactivity data indicated that 11C-flumazenil binds to saturable sites of a homogeneous population. The data indicate that intravenous doses of 1 or 2 mg flumazenil result in a benzodiazepine receptor occupancy of about 50 per cent. The method described should be useful for studying regional differences in benzodiazepine receptor characteristics in the living human brain in healthy subjects and neuropsychiatric disorders, and also in relation to treatment with drugs interacting with benzodiazepine receptors.  相似文献   
997.
Results are reported on the regioselective C‐deuteriation of 2‐methyl‐tetralone using a series of D‐sources and tertiary amines as potential mediators. The results presented further aid the understanding of kinetic deuteriation of both ‘base‐containing’ and ‘base‐free’ enolates. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
998.
目的分析子痫颅脑CT表现及与临床相关性。方法18例子痫患者均行颅脑CT平扫,其中3例行增强扫描,8例进行CT复查。结果14例患者显示脑白质内广泛低密度水肿区,枕叶脑白质累及为主,并多伴有额叶、顶叶受侵。4例表现为脑内局限性低密度区,2例合并脑出血,呈散在小斑片状分布。结论CT是子痫脑内病灶较好的影像检查手段,既可发现早期病灶,又可评价预后。  相似文献   
999.
31例活动性肺结核治疗前及治愈后的CT征象分析   总被引:1,自引:0,他引:1  
目的 探讨抗结核疗前及治愈后活动性肺结核CT征象的变化特点.方法 选取临床治愈的活动性肺结核31例,对比观察活动性肺结核的CT征象转归表现.结果 肺结核活动性CT征象治愈前检出率为100.0%,治疗后检出率为35.5%.活动性CT征象中毛玻璃阴影、节段分布小叶中心结节影、小叶样实变影、树芽征、支气管壁增厚、厚壁空洞和肺实变治疗前检出率分别为87.1%、80.6%、80.1%、61.3%、58.1%、48.4%和32.3%、,治愈后检出率分别为0、19.4%、0、0、12.9%、0和3.2%.治疗前活动性肺结核CT检查可检出多种活动性影像,而疗程结束后上述征象减少并多以单发为主,两者有显著差异(P<0.01).结论 CT检查有助于活动性肺结核治疗疗效的判定,并具有较高的敏感度,但特异度较低.  相似文献   
1000.
AIMS: Increased levels of inflammatory biomarkers, especially C-reactive protein (CRP), are associated with increased risk for cardiovascular disease (CVD) events, such as myocardial infarction, stroke, peripheral vascular disease, and sudden cardiac death. Medical interventions that increase CRP levels, such as hormone replacement therapy (HRT) in post-menopausal women, are under increasing scrutiny. The effect of HRT on CRP levels in women with Type 2 diabetes (T2DM) is not well documented, and conflicting conclusions have been reported. The aim of this study was to determine the influence of HRT on women with diabetes in a large cross-sectional study. METHODS: Three hundred and twenty-seven post-menopausal women with T2DM from the Diabetes Heart Study participated. Current use of HRT was determined and serum CRP levels were measured using a high-sensitivity ELISA kit. Generalized estimating equation methods were used to assess the relationship of multiple clinical and lifestyle (e.g. smoking) measures on CRP levels including differences between women taking HRT (HRT+) and not taking HRT (HRT-). RESULTS: Overall serum CRP levels were strongly associated with body mass index (P < 0.0001) and age (P < 0.0001). Of the women, 243 were not using HRT and 84 were using HRT. HRT+ and HRT- women did not differ significantly in measures of clinical traits, with the exception of higher mean low-density lipoprotein cholesterol in HRT- women (P = 0.004). In all models tested, HRT+ women had significantly higher circulating CRP levels, with P-values ranging from 0.0045 to 0.010. CONCLUSIONS: In this study of serum CRP concentration as a function of HRT in women with Type 2 diabetes, there was consistent evidence for increased circulating CRP levels in women receiving oestrogen-containing HRT. Whether HRT-induced increases in CRP can account for the adverse cardiovascular effects of HRT remains to be established; however, based on these data, there is little reason to believe that diabetic women would be spared from such an effect.  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