全文获取类型
收费全文 | 45092篇 |
免费 | 2866篇 |
国内免费 | 1549篇 |
专业分类
耳鼻咽喉 | 261篇 |
儿科学 | 993篇 |
妇产科学 | 548篇 |
基础医学 | 6981篇 |
口腔科学 | 828篇 |
临床医学 | 3332篇 |
内科学 | 6914篇 |
皮肤病学 | 768篇 |
神经病学 | 4168篇 |
特种医学 | 991篇 |
外国民族医学 | 6篇 |
外科学 | 3314篇 |
综合类 | 5419篇 |
现状与发展 | 4篇 |
预防医学 | 1994篇 |
眼科学 | 441篇 |
药学 | 7504篇 |
5篇 | |
中国医学 | 1879篇 |
肿瘤学 | 3157篇 |
出版年
2023年 | 450篇 |
2022年 | 942篇 |
2021年 | 1183篇 |
2020年 | 1087篇 |
2019年 | 1742篇 |
2018年 | 1588篇 |
2017年 | 1307篇 |
2016年 | 1150篇 |
2015年 | 1291篇 |
2014年 | 2120篇 |
2013年 | 2508篇 |
2012年 | 2078篇 |
2011年 | 2396篇 |
2010年 | 2131篇 |
2009年 | 2123篇 |
2008年 | 2121篇 |
2007年 | 2012篇 |
2006年 | 1864篇 |
2005年 | 1524篇 |
2004年 | 1575篇 |
2003年 | 1480篇 |
2002年 | 1161篇 |
2001年 | 1071篇 |
2000年 | 899篇 |
1999年 | 866篇 |
1998年 | 750篇 |
1997年 | 630篇 |
1996年 | 565篇 |
1995年 | 441篇 |
1994年 | 383篇 |
1993年 | 359篇 |
1992年 | 265篇 |
1991年 | 270篇 |
1990年 | 222篇 |
1989年 | 221篇 |
1988年 | 175篇 |
1986年 | 169篇 |
1985年 | 678篇 |
1984年 | 910篇 |
1983年 | 707篇 |
1982年 | 639篇 |
1981年 | 615篇 |
1980年 | 506篇 |
1979年 | 459篇 |
1978年 | 344篇 |
1977年 | 256篇 |
1976年 | 304篇 |
1975年 | 278篇 |
1974年 | 212篇 |
1973年 | 204篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Nd:YAG激光对牙本质钙/磷比值的影响 总被引:1,自引:0,他引:1
朱庆萍 《临床口腔医学杂志》1998,14(3):131-132
为探讨Nd:YAG激光对牙本质矿物含量的影响,应用扫描电镜和能谱仪定点测量50个上前牙标本的根管壁(激光照射工和正常对比区)的钙、磷含量,结果表明,照射区牙本质钙/磷(Ca/P)比值高于对比区,当激光能量达15W以上时变化更为显著,提示Nd:YAG激光能提高牙本质的钙化程度。 相似文献
32.
本文采用RP-HPLC方法对紫苏油及其习用品白苏油、野苏油甘油酯进行了定性定量分析。利用HPLC分析油脂也为中药材真伪鉴别提供了一条有效途径。 相似文献
33.
目的 :通过检测 P73蛋白、P2 1蛋白在乳腺癌中的表达及其与临床病理指标的关系 ,探讨乳腺癌的生物学特性 ,分析它们在乳腺癌的发生、转移中所起的作用。方法 :应用免疫组化 S-P法检测 68例乳腺癌石蜡包埋标本中 P73、P2 1的表达情况。结果 :a.在乳腺癌 - 级与 级之间 P73蛋白阳性率分别为 1 8.75 % ( 9/48)和 60 .0 0 % ( 1 2 /2 0 ) ,差异有显著性 ( P <0 .0 5 )。随着 P73阳性表达率增高 ,乳腺癌的恶性程度增高。b.淋巴结转移组 p2 1的阳性表达率 2 3 .3 3 % ( 7/3 0 )明显低于无淋巴结转移组的阳性率 5 2 .63 % ( 2 0 /3 8) ,差异有显著性( P <0 .0 5 )。c.P73、P2 1之间无相关。结论 :P73、P2 1与乳腺癌的发生、发展有关 相似文献
34.
曾艺东 《白求恩军医学院学报》2005,3(3):137-138
目的观察喜炎平与维生素K3联合治疗小儿秋季腹泻的疗效.方法将89例秋季腹泻患儿随机分为2组.治疗组采用喜炎平与维生素K3联合治疗,对照组则采用利巴韦林治疗,疗程5d.结果治疗组的总有效率为93.3%,显著优于对照组的65.9%(X2=10.37,P<0.01).结论喜炎平与维生素K3联合治疗小儿秋季腹泻值得进一步推广. 相似文献
35.
《Nutrition reviews》1987,45(10):246-248
Increasing dietary 18:2 n-6/18:3 n-3 causes similar relative changes in fatty acid profiles of phosphatidylethanolamine and phosphatidylcholine from rat neural and erythrocyte membranes. 相似文献
36.
Pseudomonas cepacia has recently emerged as an important nosocomial pathogen. We analyzed a national nosocomial infections database, the National Nosocomial Infections Surveillance (NNIS) system, to describe the epidemiology of endemic nosocomial P. cepacia infections. Between 1980 and 1985, the P. cepacia nosocomial infection rate was 2.4 per 100,000 patient discharges. During this period, there was a significant increase in the P. cepacia infection rate. The highest infection rate was reported from large medical school-affiliated hospitals. Over 90% of the infections were reported from medicine and surgery services. The most frequently reported site of infection was the lower respiratory tract (31%), followed by blood (20%) and the urinary tract (20%). Nosocomial P. cepacia infections are often associated with mortality, particularly when they involve the lung. These data confirm the hypothesis that P. cepacia is an emerging nosocomial pathogen and suggest that the epidemiology of endemic infections differs from that reported for epidemic inflections. 相似文献
37.
P Mismetti S Laporte P Zufferey M Epinat H Decousus M Cucherat 《Journal of thrombosis and haemostasis》2004,2(7):1058-1070
BACKGROUND: The benefit-to-risk ratio of vitamin K antagonists (VKA), relative to active comparators, especially low-molecular-weight heparins (LMWH), for preventing venous thromboembolism in patients undergoing major orthopedic surgery is debated. OBJECTIVES: We performed a meta-analysis of all randomized trials in orthopedic surgery comparing adjusted doses of VKA to control treatments. PATIENTS AND METHODS: An exhaustive literature search, both manual and computer-assisted, was performed. Studies were selected on the basis of randomization procedure (VKA vs. a control group). At least one of the following outcome measures was to be evaluated: deep vein thrombosis (DVT), pulmonary embolism (PE), death, major hemorrhage or wound hematoma. Four reviewers assessed each article to determine eligibility for inclusion and outcome measures. RESULTS: VKAs were more effective than placebo or no treatment in reducing DVT [567 patients, relative risk (RR) = 0.56, 95% confidence interval (CI) 0.37, 0.84, P < 0.01] and clinical PE (651 patients, RR = 0.23, 95% CI 0.09, 0.59, P < 0.01). These results were obtained at the cost of a higher rate of wound hematoma (162 patients, RR = 2.91, 95% CI 1.09, 7.75, P = 0.03). VKAs were also more effective than intermittent pneumatic compression (534 patients, RR = 0.46, 95% CI 0.25, 0.82, P = 0.009) in preventing proximal DVT. In contrast, VKAs were less effective than LMWH in preventing total DVT and proximal DVT (9822 patients, RR = 1.51, 95% CI 1.27, 1.79, P < 0.001; and 6131 patients, RR = 1.51, 95% CI 1.04, 2.17, P = 0.028, respectively). The differences between VKA and LMWH in major hemorrhage and wound hematoma were not significant. CONCLUSIONS: In patients undergoing major orthopedic surgery, VKAs are less effective than LMWH, without any significant difference in the bleeding risk. 相似文献
38.
Ana C Mendes M Madalena Caldeira Claudia Silva Shawn C Burgess Matthew E Merritt Filipe Gomes Cristina Barosa Teresa C Delgado Fatima Franco Pedro Monteiro Luis Providencia John G Jones 《Magnetic resonance in medicine》2006,56(5):1121-1125
Menthol glucuronide was isolated from the urine of a healthy 70-kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U-(13)C]glucose. Glucuronide (13)C-excess enrichment levels were 4-6% and thus provided high signal-to-noise ratios (SNRs) for confident assignment of (13)C-(13)C spin-coupled multiplet components within each (13)C resonance by (13)C NMR. The [U-(13)C]glucuronide isotopomer derived via direct pathway conversion of [U-(13)C]glucose to [U-(13)C]UDP-glucose was resolved from [1,2,3-(13)C(3)]- and [1,2-(13)C(2)]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U-(13)C]glucose. In a second study, a group of four overnight-fasted patients (63 +/- 10 kg) with severe heart failure were given peppermint oil and infused with [U-(13)C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady-state plasma [U-(13)C]glucose enrichment of 4.6% +/- 0.6%. Menthol glucuronide was harvested and glucuronide (13)C-isotopomers were analyzed by (13)C NMR. [U-(13)C]glucuronide enrichment was 0.6% +/- 0.1%, and the sum of [1,2,3-(13)C(3)] and [1,2-(13)C(2)]glucuronide enrichments was 0.9% +/- 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% +/- 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% +/- 10% of GP. 相似文献
39.
探讨keratin 13基因在喉癌发生中的作用。方法在keratin 13基因内部及附近选择5个微卫星引物进行LOH分析,于DNA水平间接检测100例喉癌患者中该基因的缺失情况。结果5个STR位点均存在LOH,其中D17S1964E、D17S2092、D17S791、D17S1665及D17S808位点的LOH频率分别为30.48%、26.02%、21.62%、37.66%和21.51%,以D17S1665位点的LOH频率最高,杂合性丢失与临床分期无显著相关。结论Keratin13基因在喉癌的发生中具有重要作用,具体机制有待进一步研究。 相似文献
40.
Alcohol is an important risk factor for human oesophageal cancer. There is evidence from epidemiological studies that some
specific alcoholic drinks, e.g. Calvados apple brandy, are associated with a greater risk than others. Alcohol induces cytochrome
P450 2E1 (CYP2E1) and the hypothesis was tested that different alcoholic beverages, containing a variety of alcoholic compounds,
could differentially induce expression of cytochrome P450 enzymes. Twelve groups of five rats each were treated for 3 days
with different alcoholic beverages (ethanol alone, whisky, farm-produced or commercial Calvados brandy, beer, cider, wine)
adjusted to 4, 10 or 20% of ethanol in drinking water. Immunoblotting using a monoclonal antibody specific for rat CYP2E1
revealed a single protein band in liver microsomes. Densitometric quantitation of microsomal proteins demonstrated a significant
two-, three- and sixfold increase in band intensity after treatment with ethanol concentrations of 4, 10 and 20% respectively,
compared to control rats drinking water alone. There was a dose-dependent increase in liver microsomal metabolism of CYP2E1
substrates (para-nitrophenol and dimethylnitrosamine) in ethanol-treated rats. However, there were no significant differences
in the level of CYP2E1 protein or enzymatic activity between the different alcoholic beverages at the same ethanol concentration.
There was a slight increase in hepatic CYP1A-related enzymatic activities in the alcohol-treated rats compared to the controls,
but no difference between the treated groups either with dose of ethanol or type of beverage. These data show that induction
of CYP2E1 with acute alcohol treatment is predominantly determined by the ethanol content of the beverage.
Received: 10 February 1997 / Accepted: 26 May 1997 相似文献