收费全文 | 212582篇 |
免费 | 16005篇 |
国内免费 | 738篇 |
耳鼻咽喉 | 2438篇 |
儿科学 | 5701篇 |
妇产科学 | 4425篇 |
基础医学 | 27424篇 |
口腔科学 | 4634篇 |
临床医学 | 20360篇 |
内科学 | 44883篇 |
皮肤病学 | 2792篇 |
神经病学 | 20566篇 |
特种医学 | 7106篇 |
外国民族医学 | 13篇 |
外科学 | 33430篇 |
综合类 | 3568篇 |
现状与发展 | 2篇 |
一般理论 | 291篇 |
预防医学 | 19275篇 |
眼科学 | 4496篇 |
药学 | 14647篇 |
1篇 | |
中国医学 | 376篇 |
肿瘤学 | 12897篇 |
2023年 | 773篇 |
2021年 | 3490篇 |
2020年 | 2148篇 |
2019年 | 3474篇 |
2018年 | 4058篇 |
2017年 | 3281篇 |
2016年 | 3473篇 |
2015年 | 4145篇 |
2014年 | 6193篇 |
2013年 | 8964篇 |
2012年 | 13314篇 |
2011年 | 14525篇 |
2010年 | 8209篇 |
2009年 | 7430篇 |
2008年 | 13780篇 |
2007年 | 14599篇 |
2006年 | 14117篇 |
2005年 | 14564篇 |
2004年 | 13967篇 |
2003年 | 13044篇 |
2002年 | 12571篇 |
2001年 | 2020篇 |
2000年 | 1615篇 |
1999年 | 2190篇 |
1998年 | 2883篇 |
1997年 | 2489篇 |
1996年 | 2267篇 |
1995年 | 1990篇 |
1994年 | 1799篇 |
1993年 | 1639篇 |
1992年 | 1271篇 |
1991年 | 1231篇 |
1990年 | 1121篇 |
1989年 | 1023篇 |
1988年 | 1063篇 |
1987年 | 1071篇 |
1986年 | 1062篇 |
1985年 | 1146篇 |
1984年 | 1499篇 |
1983年 | 1469篇 |
1982年 | 1817篇 |
1981年 | 1634篇 |
1980年 | 1546篇 |
1979年 | 821篇 |
1978年 | 966篇 |
1977年 | 936篇 |
1976年 | 841篇 |
1975年 | 703篇 |
1974年 | 694篇 |
1973年 | 609篇 |
The metabolism of the pyrethroids deltamethrin (DLM), cis-permethrin (CPM) and trans-permethrin (TPM) was studied in human expressed cytochrome P450 (CYP) and carboxylesterase (CES) enzymes.
DLM, CPM and TPM were metabolised by human CYP2B6 and CYP2C19, with the highest apparent intrinsic clearance (CLint) values for pyrethroid metabolism being observed with CYP2C19. Other CYP enzymes contributing to the metabolism of one or more of the three pyrethroids were CYP1A2, CYP2C8, CYP2C9*1, CYP2D6*1, CYP3A4 and CYP3A5. None of the pyrethroids were metabolised by CYP2A6, CYP2E1, CYP3A7 or CYP4A11.
DLM, CPM and TPM were metabolised by both human CES1 and CES2 enzymes.
Apparent CLint values for pyrethroid metabolism by CYP and CES enzymes were scaled to per gram of adult human liver using abundance values for microsomal CYP enzymes and for CES enzymes in liver microsomes and cytosol. TPM had the highest and CPM the lowest apparent CLint values for total metabolism (CYP and CES enzymes) per gram of adult human liver.
Due to their higher abundance, all three pyrethroids were extensively metabolised by CES enzymes in adult human liver, with CYP enzymes only accounting for 2%, 10% and 1% of total metabolism for DLM, CPM and TPM, respectively.
Ressults show that opportunities for improving O&M include; operation of public toilets is a source of livelihood; operators are knowledgeable on occupational risks, and the community is involvedin sanitation activities. Barriers to effective O&M include; high operation costs, failure to break even and a lack of investments in occupational health Therefore, there is need to recognise the significance of public toilets as a viable alternative to open defecation in areas where ownership of private sanitation facilities is difficult. Failure to observe the health and safety of toilet operators may further compromise O&M. 相似文献
Purpose
The objective of the study was to define factors associated with adolescent and young adult (AYA) experiences with private time and having discussed confidentiality and the impact of these experiences on improving delivery of clinical preventive services.Methods
In 2016, a nationally representative sample of 1,918 US AYAs (13- to 26-year-olds) was surveyed. Survey questionnaire domains were based on prior research and Fishers' information-motivation-behavior skills conceptual model. Data were weighted to represent US households with AYA and analyzed to identify factors independently associated with ever experiencing private time and discussions of confidentiality with a regular health-care provider (HCP). We examined the association of these experiences on AYA attitudes about health care.Results
Fifty-five percent of female and 49% of male AYA reported ever having had private time with an HCP and 55% of female and 44% of male AYA had spoken to an HCP about confidentiality. Independent predictors of having experienced private time and confidentiality included older age, race, higher household income, gender of the provider, amount of years with the provider, and involvement in risk behaviors. AYA who had experienced private time and confidentiality discussions had more positive attitudes about their providers, were more willing and comfortable discussing sensitive topics, and thought that these discussions should happen at younger ages.Conclusions
Although confidentiality and private time are important to AYA, many are not experiencing these components of care. Providing private time and discussions of confidentiality can improve the delivery of health care for young people by enhancing positive youth attitudes about preventive care. 相似文献Methods: [11C]WAY100635, [18F]altanserin and positron emission tomography were used to compare 5-HT1A and 5-HT2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.
Results: The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.
Conclusion: Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents. 相似文献