全文获取类型
收费全文 | 17252篇 |
免费 | 1414篇 |
国内免费 | 44篇 |
专业分类
耳鼻咽喉 | 88篇 |
儿科学 | 470篇 |
妇产科学 | 224篇 |
基础医学 | 2235篇 |
口腔科学 | 317篇 |
临床医学 | 1893篇 |
内科学 | 3410篇 |
皮肤病学 | 317篇 |
神经病学 | 1614篇 |
特种医学 | 678篇 |
外科学 | 2357篇 |
综合类 | 233篇 |
一般理论 | 34篇 |
预防医学 | 2077篇 |
眼科学 | 272篇 |
药学 | 1316篇 |
中国医学 | 23篇 |
肿瘤学 | 1152篇 |
出版年
2023年 | 145篇 |
2022年 | 231篇 |
2021年 | 525篇 |
2020年 | 321篇 |
2019年 | 437篇 |
2018年 | 497篇 |
2017年 | 385篇 |
2016年 | 431篇 |
2015年 | 493篇 |
2014年 | 612篇 |
2013年 | 850篇 |
2012年 | 1308篇 |
2011年 | 1302篇 |
2010年 | 790篇 |
2009年 | 643篇 |
2008年 | 1157篇 |
2007年 | 1086篇 |
2006年 | 1052篇 |
2005年 | 1038篇 |
2004年 | 955篇 |
2003年 | 878篇 |
2002年 | 727篇 |
2001年 | 242篇 |
2000年 | 202篇 |
1999年 | 185篇 |
1998年 | 158篇 |
1997年 | 121篇 |
1996年 | 106篇 |
1995年 | 95篇 |
1994年 | 84篇 |
1993年 | 77篇 |
1992年 | 124篇 |
1991年 | 102篇 |
1990年 | 101篇 |
1989年 | 70篇 |
1988年 | 81篇 |
1987年 | 73篇 |
1986年 | 80篇 |
1985年 | 95篇 |
1984年 | 73篇 |
1983年 | 80篇 |
1982年 | 54篇 |
1981年 | 39篇 |
1979年 | 54篇 |
1978年 | 53篇 |
1977年 | 41篇 |
1976年 | 43篇 |
1975年 | 47篇 |
1974年 | 54篇 |
1973年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
OBJECTIVE--To compare the risk of death and the risk of nonfatal injury during firearm-associated family and intimate assaults (FIAs) with the risks during non-firearm-associated FIAs. DESIGN--Records review of police incident reports of FIAs that occurred in 1984. Victim outcomes (death, nonfatal injury, no injury) and weapon involvement were examined for incidents involving only one perpetrator. SETTING--City of Atlanta, Ga, within Fulton County. PARTICIPANTS--Stratified sample (n = 142) of victims of nonfatal FIAs, drawn from seven nonfatal crime categories, plus all fatal victims (n = 23) of FIAs. MAIN OUTCOME MEASURES--Risk of death (vs nonfatal injury or no injury) during FIAs involving firearms, relative to other types of weapons; risk of nonfatal injury (vs all other outcomes, including death) during FIAs involving firearms, relative to other types of weapons. RESULTS--Firearm-associated FIAs were 3.0 times (95% confidence interval, 0.9 to 10.0) more likely to result in death than FIAs involving knives or other cutting instruments and 23.4 times (95% confidence interval, 7.0 to 78.6) more likely to result in death than FIAs involving other weapons or bodily force. Overall, firearm-associated FIAs were 12.0 times (95% confidence interval, 4.6 to 31.5) more likely to result in death than non-firearm-associated FIAs. CONCLUSIONS--Strategies for limiting the number of deaths and injuries resulting from FIAs include reducing the access of potential FIA assailants to firearms, modifying firearm lethality through redesign, and establishing programs for primary prevention of violence among intimates. 相似文献
53.
OBJECTIVE: Determine the minimum concentration of plasma fibrinogen needed to stimulate the aggregation of platelets, collected from normal subjects, using ADP. DESIGN: Platelet rich plasmas (300 x 10(9) platelets/L) were made and adjusted to final fibrinogen concentrations of 75, 19, 5, and 0 mg/dL using fibrinogen free serum. Each fibrinogen concentration in all twelve subjects was aggregated with ADP SETTING: Research laboratory in the Department of Clinical Laboratory Science at Saint Louis University. PARTICIPANTS: Twelve healthy volunteers of both genders, between the ages of 18 and 60 years who were not pregnant and weighed at least 110 pounds were included in the study. Subjects were excluded from the study if they had ingested aspirin within one week prior to blood collection. In addition, subjects with a history of bleeding disorders such as afibrinogenemia, hypofibrinogenemia, von Willebrand disease, and Bernand-Soulier disease were rejected from the study. MAIN OUTCOME MEASURES: Platelet aggregation tracings were analyzed for amplitude and compared across plasma fibrinogen concentrations. In addition, the type of curve (monophasic vs. biphasic), smoothness and aggregation stability were also noted. RESULTS: The results show that aggregation occurred with every dilution of fibrinogen tested and that the amplitude of the aggregation curves appears not to be dependent on plasma fibrinogen. CONCLUSIONS: The results indicate that platelets from healthy individuals previously exposed to normal fibrinogen levels will aggregate equally well in decreasing plasma fibrinogen concentrations and even in the absence of plasma fibrinogen using ADP as the aggregator. 相似文献
54.
Ana T Timóteo Miguel Mendes Carlos T Aguiar Ana Barba?a Ricardo Seabra-Gomes 《Revista portuguesa de cardiologia》2004,23(12):1519-1530
BACKGROUND: The exercise test has a recognized lower risk of complications when used in the general population and in coronary artery diseased patients, but from a theoretical point of view should have a higher rate of complications when performed in patients with chronic heart failure (CHF). AIMS: To characterize and assess the type and incidence of complications during cardiopulmonary stress test (CPX) in patients with depressed left ventricular systolic function in comparison with a group of patients and individuals with normal function. METHODS: Retrospective analysis of the 334 consecutive CPX performed for risk stratification in 198 patients with a left ventricular ejection fraction below 40% (Group A) and 180 consecutive CPX performed in 78 subjects with normal function (Group B). The two groups were compared with respect to demographic data, CPX parameters and specific complications. Results: Major complications during the tests occurred only in 14 tests of Group A (4.2%, p = 0.012). Non-sustained ventricular tachycardia, <6 beats, occurred in 7 group A and 2 group B tests. The absence of coronary artery disease was the only independent predictor for complications. CONCLUSIONS: Major CPX complications occurred only in patients with impaired left ventricular systolic function. Heart failure patients showed a low probability (around 4%) for complications during CPX, significantly higher and more severe than the risk in the group of patients with normal ventricular function, allowing us to recommend that CPX in patients with heart failure should be performed in a hospital setting under the supervision of a physician with specific training. 相似文献
55.
利用乙型肝炎病毒DNA开放框架上的BamHI和HpaI位点,酶切消化质粒载体PEcob6(含双拷贝HBVDNA),得到约900bp的HBV-S基因片断。将其插入到噬菌粒载体PBluescriptsk+的SmaI位点上。然后通过体外寡核苷酸介导的人工定点突变获得一系列(共12种)S基因“免疫逃避”突变型。再通过EB病毒真核表达载体pMEP4上的BamHI和Kpnl位点将噬菌粒pBluescripsk+上的S基因突变型片断定向克隆到PMEP4上,从而构建了含乙肝S基因突变型的重组质粒pMEP4HBSM。用其转染人肝癌传代细胞系HepG2,经潮霉素选择,三周后获得抗性细胞克隆。经用抗HBs单克隆抗体(含针对HBsAg“a”抗原决定簇)检测除含变异体145(即145位上甘氨酸为精氨酸替代)外其余抗变异体HBsAg均为阳性。经Westernblot证实变异体145,在分子量约为23KD处有一特异HBsAg蛋白带。 相似文献
56.
The processing of antigens delivered as DNA vaccines 总被引:2,自引:0,他引:2
Summary: The ability of DNA vaccines to provide effective immunological protection against infection and tumors depends on their ability to generate good CD4+ and CD8+ T‐cell responses. Priming of these responses is a property of dendritic cells (DCs), and so the efficacy of DNA‐encoded vaccines is likely to depend on the way in which the antigens they encode are processed by DCs. This processing could either be via the synthesis of the vaccine‐encoded antigen by the DCs themselves or via its uptake by DCs following its synthesis in bystander cells that are unable to prime T cells. These different sources of antigen are likely to engage different antigen‐processing pathways, which are the subject of this review. Understanding how to access different processing pathways in DCs may ultimately aid the rational development of plasmid‐based vaccines to pathogens and to cancer. 相似文献
57.
58.
59.
60.