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   3513篇
  免费   311篇
  国内免费   248篇
耳鼻咽喉   16篇
儿科学   47篇
妇产科学   48篇
基础医学   439篇
口腔科学   74篇
临床医学   490篇
内科学   446篇
皮肤病学   19篇
神经病学   210篇
特种医学   131篇
外国民族医学   1篇
外科学   339篇
综合类   520篇
一般理论   1篇
预防医学   242篇
眼科学   96篇
药学   400篇
  5篇
中国医学   202篇
肿瘤学   346篇
  2024年   10篇
  2023年   38篇
  2022年   138篇
  2021年   179篇
  2020年   122篇
  2019年   123篇
  2018年   137篇
  2017年   119篇
  2016年   86篇
  2015年   148篇
  2014年   174篇
  2013年   186篇
  2012年   243篇
  2011年   273篇
  2010年   168篇
  2009年   166篇
  2008年   153篇
  2007年   179篇
  2006年   211篇
  2005年   210篇
  2004年   126篇
  2003年   156篇
  2002年   102篇
  2001年   103篇
  2000年   84篇
  1999年   87篇
  1998年   64篇
  1997年   53篇
  1996年   46篇
  1995年   43篇
  1994年   25篇
  1993年   13篇
  1992年   21篇
  1991年   7篇
  1990年   12篇
  1989年   12篇
  1988年   20篇
  1987年   10篇
  1986年   9篇
  1985年   2篇
  1984年   7篇
  1983年   3篇
  1982年   2篇
  1979年   1篇
  1963年   1篇
排序方式: 共有4072条查询结果,搜索用时 15 毫秒
71.
In the present work, the structures and magnetic properties of (Nd, Pr, Ce) 2Fe14B/α-Fe nanocomposite magnets were thoroughly investigated. The microwave annealing was applied to achieve a uniform heating effect and uniform grains. Microwave annealing is more favorable to obtain α-Fe phase than conventional annealing, which leads to the enhanced coercivity of hysteresis loops. The coercivity of nanocomposite magnets was 245 kA/m after annealing at 2000 W for 10 min.  相似文献   
72.
探讨对分课堂在《中医诊断学》教学中的应用。将对分课堂授课模式引入《中医诊断学》教学过程中,通过学生的课堂表现及课后对学生的问卷调查,评价对分课堂教学模式对《中医诊断学》教学效果的影响。学生普遍认可对分课堂教学模式,学生课堂活跃程度提高、主观能动性增加,自主学习能力增加,学习效率提高。通过对分课堂教学,有助于提高学生对《中医诊断学》的学习热情,提高学习成绩,提升教学质量。具有一定的推广意义。  相似文献   
73.
目的探讨不同CT扫描条件下人工智能(AI)系统对胸部模体内实性结节检出效率与辐射剂量的影响。方法于仿真胸部拟人模体内各肺叶和肺段均匀放置不同CT值和直径的60颗不同形态的仿真结节。应用GE Revolution evo CT对胸部模体进行扫描, 通过调节管电压80、100、120和140 kV, 噪声指数(NI 10~40, 间隔2), 其他参数固定, 采集64组不同参数图像。在AI软件上记录仿真结节检出情况并计算检出率与误检率, 不同形态结节分别计算;记录每次扫描平均容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP)。结果不同管电压对类球形结节和不规则结节的检出率、误检率差异均无统计学意义(P>0.05);不同噪声指数对类球形结节和不规则结节的检出率、误检率差异均存在统计学意义(F=10.57、17.77、9.33, P<0.001)。不同管电压对CTDIvol、DLP差异无统计学意义(P>0.05), 不同噪声指数对CTDIvol、DLP差异具有统计学意义(F=59.87、60.92, P<0.001)。结节的检出率与噪声指数、CTDIvol、DLP...  相似文献   
74.
75.
Effective prophylaxis and antiviral therapies are urgently needed in the event of reemergence of the highly contagious and often fatal severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) infection. We have identified eight recombinant human single-chain variable region fragments (scFvs) against the S1 domain of spike (S) protein of the SARS-CoV from two nonimmune human antibody libraries. One scFv 80R efficiently neutralized SARS-CoV and inhibited syncytia formation between cells expressing the S protein and those expressing the SARS-CoV receptor angiotensin-converting enzyme 2 (ACE2). Mapping of the 80R epitope showed it is located within the N-terminal 261-672 amino acids of S protein and is not glycosylation-dependent. 80R scFv competed with soluble ACE2 for association with the S1 domain and bound S1 with high affinity (equilibrium dissociation constant, Kd=32.3 nM). A human IgG1 form of 80R bound S1 with a 20-fold higher affinity of 1.59 nM comparable to that of ACE2 (Kd=1.70 nM), and neutralized virus 20-fold more efficiently than the 80R scFv. These data suggest that the 80R human monoclonal antibody may be a useful viral entry inhibitor for the emergency prophylaxis and treatment of SARS, and that the ACE2-binding site of S1 could be an attractive target for subunit vaccine and drug development.  相似文献   
76.

OBJECTIVE

To examine cardiovascular disease (CVD) mortality risk in men with diabetes only, metabolic syndrome only, and concurrent metabolic syndrome and diabetes.

RESEARCH DESIGN AND METHODS

We examined CVD mortality risk by metabolic syndrome and diabetes status in men from the Aerobics Center Longitudinal Study (ACLS) (mean ± SD age 45.1 ± 10.2 years). Participants were categorized as having neither diabetes nor metabolic syndrome (n = 23,770), metabolic syndrome only (n = 8,780), diabetes only (n = 532), or both (n = 1,097). The duration of follow-up was 14.6 ± 7.0 years with a total of 483,079 person-years of exposure and 1,085 CVD deaths.

RESULTS

Age-, examination year–, and smoking-adjusted CVD death rates (per 1,000 man-years) in men with neither metabolic syndrome nor diabetes, metabolic syndrome only, diabetes only, and both were 1.9, 3.3, 5.5, and 6.5, respectively. CVD mortality was higher in men with metabolic syndrome only (hazard ratio 1.8 [95% CI 1.5–2.0]), diabetes only (2.9 [2.1–4.0]), and both (3.4 [2.8–4.2]) compared with men with neither. The presence of metabolic syndrome was not associated (1.2 [0.8–1.7]) with higher CVD mortality risk in individuals with diabetes. In contrast, the presence of diabetes substantially increased (2.1 [1.7–2.6]) CVD mortality risk in individuals with metabolic syndrome.

CONCLUSIONS

The presence of diabetes was associated with a threefold higher CVD mortality risk, and metabolic syndrome status did not modify this risk. Our findings support the fact that physicians should be aggressive in using CVD risk–reducing therapies in all diabetic patients regardless of metabolic syndrome status.Approximately 7.8% of the U.S. population has diabetes, and it is estimated that the number of adults with diabetes will increase to 48.3 million by 2050 in the U.S. and to 300 million worldwide in the year 2025, representing a 122% rise compared with 1995 (13). The public health importance is great, considering that individuals with diabetes have more than twice the risk for premature death, heart disease, and stroke compared with individuals without diabetes (1). Although clinical definitions differ slightly, metabolic syndrome is generally characterized as a clustering of abnormal levels of blood lipids (low HDL and high triglycerides), impaired fasting glucose, elevated blood pressure, and excess abdominal obesity (47). Approximately 25% of Americans and >50% of those aged >50 years meet the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III definition of metabolic syndrome (8). Similar to individuals with diabetes, individuals with metabolic syndrome have an increased risk for premature death, heart disease, and stroke (912).Metabolic syndrome and diabetes share many common characteristics, so it is not surprising that 65–85% of individuals with diabetes also have metabolic syndrome (1315). However, relativity few studies have examined the effect of the combination of metabolic syndrome and diabetes on cardiovascular disease (CVD) risk (11,13,14). A cross-sectional study using National Health and Nutrition Examination Survey data reported that the prevalence of coronary heart disease (CHD) among individuals with diabetes and without metabolic syndrome was similar to that in those without diabetes or metabolic syndrome (7.5 vs. 8.7%, respectively) (14). However, individuals with concurrent diabetes and metabolic syndrome had a substantially greater prevalence (19.2%) compared with these groups. This finding suggests that in individuals with diabetes there is an increased risk for CHD only when metabolic syndrome also is present. Similarly, in a prospective study Hunt et al. (16) reported that within individuals with diabetes, those with metabolic syndrome have an increased risk for CVD mortality, whereas individuals with diabetes but not metabolic syndrome do not. However, this study was relatively small (n = 2,815) with only 117 CVD deaths. Finally, the UK Prospective Diabetes Study (UKPDS) reported that in individuals with type 2 diabetes, the presence of metabolic syndrome (NCEP) increased the risk of CVD events (17). However, it was noted from a clinical perspective that the presence of metabolic syndrome in individuals with diabetes provided little information for detecting who has an increased risk of CVD.Given the high prevalence of both metabolic syndrome and diabetes, it is of great clinical and public health importance that we develop a better understanding of the interactions of diabetes and metabolic syndrome on the risk of CVD. The primary aim of the current investigation is to examine the risk of CVD mortality in individuals with metabolic syndrome only, diabetes only, and concurrent metabolic syndrome and diabetes in a large prospective study population.  相似文献   
77.
胆心综合征215例临床分析   总被引:4,自引:0,他引:4  
目的探讨胆心综合征的临床表现、发病机理及治疗。方法对588例胆道疾患住院病人进行回顾性分析。结果该组胆道患者中有215例(36.55%)患者出现胆心综合征,其表现为一过性心绞痛5例(2.8%),窦性心动过速55例(25.6%),窦性心动过缓79例(36.8%),窦性心律不齐38例(17.7%),早搏21例(9.7%),S-T段或T波改变者53例(24.6%)。结论胆心综合征不是胆道疾患手术禁忌症而是手术适应证,但手术不宜在胆心综合征急性发作期间进行。  相似文献   
78.
目的:应用功能磁共振成像观察脑卒中后及康复过程中,在相应脑内运动功能区激活的变化情况,探讨不同运动模式下皮质功能再塑的表现。方法:选取2003-02/10大庆油田总医院康复科住院的皮质下脑梗死患者8例,在发病后1周始进行连续两个月的康复。在康复前、康复1,2个月时运用Brunnstrom分级、Caroll上肢功能量表(0 ̄100分,评分越高功能越好)对其手功能进行评价,并采用GEMR/iHiSpeed1.5超导磁共振扫描机进行磁共振成像功能激发检查。患者用病手执行简单运动(快速连续的拇指与其他各指的对指动作)、随意运动(用病手摸不同形状的木块),获得脑功能激发图像,观察脑内相关功能区的激活情况。结果:8例受试者均进入结果分析。①康复后所有患者Brunnstrom分级和Caroll上肢功能评分均较康复前有明显改善。②病手简单运动时脑内相关功能区的激活情况:8例受试者7例在损伤后早期手指不能对指,所以没有激活;M1,SMA,PMA脑区和小脑呈现单侧激活-双侧激活-单侧激活的变化过程;随着运动功能恢复,脑内激活数目随时间呈下降趋势,几乎接近正常人脑功能表现。③病手随意运动时脑内相关功能区的激活情况:实验中发现引起的运动相关功能区的激发情况变化多样,规律性较差,但其中5例受试者表现出损伤后激发数目明显减少,许多对运动起决定性支配作用的功能区亦不激活;随着运动功能恢复,激发区数目呈上升趋势,同损伤后简单运动的激活表现。结论:①脑卒中后病手经过康复治疗简单运动恢复较好,康复治疗2个月后脑内运动功能相关区域激活的规律已同正常人。②脑卒中后病手随意运动恢复较困难,康复治疗后不如简单运动恢复好,脑内相关运动功能区激活无明显的规律性。随着运动功能的恢复,脑内相应的运动功能区激活增多。  相似文献   
79.
目的 :观察氧雾化吸入备劳特和爱喘乐治疗儿童哮喘急性发作的疗效。方法 :选择 15 8例哮喘急性发作患儿作为研究对象 ,分为观察组和对照组。观察组采用氧驱动雾化吸入备劳特和爱喘乐 ;对照组静脉滴注氨茶碱和地塞米松。结果 :观察组显效率 87.3% (96 /110 ) ,总有效率 99.1% (10 9/110 ) ,临床治愈率 94 .5 % (10 4 /110 ) ;对照组显效率 2 2 .9% (11/48) ,总有效率 6 0 .4 % (2 9/48) ,临床治愈率 5 4 .2 % (2 6 /48)。观察组显效率、总有效率及临床治愈率皆显著高于对照组 ,差异有高度统计意义 (P <0 .0 1)。观察组治疗后心率较治疗前明显下降 ,差异有统计意义(P <0 .0 5 )。结论 :采用氧驱动雾化吸入备劳特和爱喘乐能快速、有效地控制哮喘发作。  相似文献   
80.
In this work, waterborne epoxy resin and graphene/ZnO (Gr/ZnO) were employed as the matrix and nanofiller to construct composite coatings with enhanced anticorrosive performance. The corrosion protection properties of the coatings were significantly improved by the dispersed Gr sheets, as well as the parallelly assembled ZnO nanoparticles. The most remarkable improvement was achieved by adding 0.04 wt% of Gr and 0.4 wt% of ZnO in the Waterborne Epoxy (WEP) coatings, where the highest impedance was 200 530 Ω cm2 on Gr0.04–ZnO0.4, far more than pure epoxy with 6186 Ω cm2 after 7 days of immersion in electrolytes. Furthermore, the Gr0.04–ZnO0.4 coatings and corresponding corrosion products immersed in a 3.5% NaCl solution for 30 days were also characterized, which could further reveal anticorrosion mechanisms of the graphene modified WEP coatings and the passivated effect of ZnO. Through the mechanism analysis, we also found that ZnO could be employed as the barrier reinforcement to improve the dispersibility of graphene in WEP coatings, and the parallel assembly of graphene occurs spontaneously, leading to remarkable improvement of anticorrosion properties.

This is the first example of synergistically assembled Gr/ZnO sheets to improve the corrosion protection properties of WEP coatings, and Gr0.04–ZnO0.4 exhibited the highest impedance of 200 530 Ω cm2 compared to pure WEP of 6186 Ω cm2.  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