全文获取类型
收费全文 | 66952篇 |
免费 | 5635篇 |
国内免费 | 177篇 |
专业分类
耳鼻咽喉 | 961篇 |
儿科学 | 1757篇 |
妇产科学 | 913篇 |
基础医学 | 8784篇 |
口腔科学 | 1056篇 |
临床医学 | 6936篇 |
内科学 | 13062篇 |
皮肤病学 | 761篇 |
神经病学 | 6137篇 |
特种医学 | 2463篇 |
外科学 | 11976篇 |
综合类 | 872篇 |
现状与发展 | 1篇 |
一般理论 | 82篇 |
预防医学 | 6131篇 |
眼科学 | 1455篇 |
药学 | 4239篇 |
中国医学 | 50篇 |
肿瘤学 | 5128篇 |
出版年
2023年 | 564篇 |
2022年 | 971篇 |
2021年 | 2331篇 |
2020年 | 1228篇 |
2019年 | 1959篇 |
2018年 | 2386篇 |
2017年 | 1695篇 |
2016年 | 1752篇 |
2015年 | 1929篇 |
2014年 | 2775篇 |
2013年 | 3426篇 |
2012年 | 5329篇 |
2011年 | 5199篇 |
2010年 | 2760篇 |
2009年 | 2352篇 |
2008年 | 3822篇 |
2007年 | 4038篇 |
2006年 | 3512篇 |
2005年 | 3250篇 |
2004年 | 2872篇 |
2003年 | 2554篇 |
2002年 | 2259篇 |
2001年 | 922篇 |
2000年 | 894篇 |
1999年 | 837篇 |
1998年 | 513篇 |
1997年 | 443篇 |
1996年 | 378篇 |
1995年 | 331篇 |
1994年 | 322篇 |
1993年 | 275篇 |
1992年 | 640篇 |
1991年 | 558篇 |
1990年 | 520篇 |
1989年 | 542篇 |
1988年 | 473篇 |
1987年 | 466篇 |
1986年 | 432篇 |
1985年 | 423篇 |
1984年 | 356篇 |
1983年 | 291篇 |
1982年 | 237篇 |
1981年 | 236篇 |
1980年 | 187篇 |
1979年 | 307篇 |
1978年 | 277篇 |
1975年 | 199篇 |
1974年 | 272篇 |
1973年 | 212篇 |
1972年 | 217篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Keith P. Reber John D. Sivey Matthew Vollmuth Priyansh D. Gujarati 《Journal of labelled compounds & radiopharmaceuticals》2022,65(9):254-263
Parabens are antimicrobial additives found in a wide array of consumer products. However, the halogenated compounds formed from parabens during wastewater disinfection are a potential environmental concern. In order to identify these transformation products and investigate their mechanism of formation, a synthetic route to ethyl parabens labeled with the stable isotope carbon-13 at specific positions within the benzene ring was developed. This efficient two-step procedure starts from commercially available 13C-labeled phenols and involves (1) initial acylation of the phenol via a Houben–Hoesch reaction with trichloroacetonitrile followed by (2) a modified haloform reaction of the resulting trichloromethyl ketone to afford the corresponding 13C-labeled ethyl parabens in 65%–80% overall yield. The scope of the modified haloform reaction was also investigated, allowing for the synthesis of other parabens derived from primary or secondary alcohols, including 13C- and deuterium-labeled esters. In addition, 4-hydroxybenzoic acid can be formed directly from the common trichloromethyl ketone intermediate upon treatment with lithium hydroxide. This protocol complements existing methods for preparing 13C-labeled paraben derivatives and offers the specific advantages of exhibiting complete regioselectivity in the Houben–Hoesch reaction (to form the para-disubstituted product) and avoiding the need for protecting groups in the modified haloform reaction that forms the paraben esters. 相似文献
24.
Understanding why persons with human immunodeficiency virus (HIV) have accelerated atherosclerosis and its sequelae, including coronary artery disease (CAD) and myocardial infarction, is necessary to provide appropriate care to a large and aging population with HIV. In this review, we delineate the diverse pathophysiologies underlying HIV-associated CAD and discuss how these are implicated in the clinical manifestations of CAD among persons with HIV. Several factors contribute to HIV-associated CAD, with chronic inflammation and immune activation likely representing the primary drivers. Increased monocyte activation, inflammation, and hyperlipidemia present in chronic HIV infection also mirror the pathophysiology of plaque rupture. Furthermore, mechanisms central to plaque erosion, such as activation of toll-like receptor 2 and formation of neutrophil extracellular traps, are also abundant in HIV. In addition to inflammation and immune activation in general, persons with HIV have a higher prevalence than uninfected persons of traditional cardiovascular risk factors, including dyslipidemia, hypertension, insulin resistance, and tobacco use. Antiretroviral therapies, although clearly necessary for HIV treatment and survival, have had varied effects on CAD, but newer generation regimens have reduced cardiovascular toxicities. From a clinical standpoint, this mix of risk factors is implicated in earlier CAD among persons with HIV than uninfected persons; whether the distribution and underlying plaque content of CAD for persons with HIV differs considerably from uninfected persons has not been definitively studied. Furthermore, the role of cardiovascular risk estimators in HIV remains unclear, as does the role of traditional and emerging therapies; no trials of CAD therapies powered to detect clinical events have been completed among persons with HIV. 相似文献
25.
26.
27.
Rene S. Hendriksen Pimlapas Leekitcharoenphon Matthew Mikoleit Jacob Dyring Jensen Rolf Sommer Kaas Louise Roer Heena B. Joshi Srirat Pornruangmong Chaiwat Pulsrikarn Gladys D. Gonzalez-Aviles E. Ascelijn Reuland Nashwan Al Naiemi Astrid Louise Wester Frank M. Aarestrup Henrik Hasman 《Journal of clinical microbiology》2015,53(2):677-680
One unreported case of extended-spectrum-beta-lactamase (ESBL)-producing Salmonella enterica serovar Typhi was identified, whole-genome sequence typed, among other analyses, and compared to other available genomes of S. Typhi. The reported strain was similar to a previously published strain harboring blaSHV-12 from the Philippines and likely part of an undetected outbreak, the first of ESBL-producing S. Typhi. 相似文献
28.
29.
30.
Elizabeth A. Mosley PhD MPH Amy J. Schulz PhD MPH MSW Lisa H. Harris MD PhD Barbara A. Anderson PhD 《Women & health》2020,60(7):806-820
ABSTRACT Abortion is legal in South Africa, but negative abortion attitudes remain common and are poorly understood. We used nationally representative South African Social Attitudes Survey data to analyze abortion attitudes in the case of fetal anomaly and in the case of poverty from 2007 to 2016 (n = 20,711; ages = 16+). We measured correlations between abortion attitudes and these important predictors: religiosity, attitudes about premarital sex, attitudes about preferential hiring and promotion of women, and attitudes toward family gender roles. Abortion acceptability for poverty increased over time (b = 0.05, p < .001), but not for fetal anomaly (b = ?0.008, p = .284). Highly religious South Africans reported lower abortion acceptability in both cases (Odds Ratio (OR)anomaly = 0.85, p = .015; ORpoverty = 0.84, p = .02). Premarital sex acceptability strongly and positively predicted abortion acceptability (ORanomaly = 2.63, p < .001; ORpoverty = 2.46, p < .001). Attitudes about preferential hiring and promotion of women were not associated with abortion attitudes, but favorable attitudes about working mothers were positively associated with abortion acceptability for fetal anomaly ((ORanomaly = 1.09, p = .01; ORpoverty = 1.02, p = .641)). Results suggest negative abortion attitudes remain common in South Africa and are closely tied to religiosity, traditional ideologies about sexuality, and gender role expectations about motherhood. 相似文献