全文获取类型
收费全文 | 22961篇 |
免费 | 2145篇 |
国内免费 | 68篇 |
专业分类
耳鼻咽喉 | 373篇 |
儿科学 | 726篇 |
妇产科学 | 613篇 |
基础医学 | 3451篇 |
口腔科学 | 687篇 |
临床医学 | 2858篇 |
内科学 | 4640篇 |
皮肤病学 | 331篇 |
神经病学 | 1653篇 |
特种医学 | 608篇 |
外科学 | 2536篇 |
综合类 | 362篇 |
一般理论 | 15篇 |
预防医学 | 2777篇 |
眼科学 | 256篇 |
药学 | 1759篇 |
中国医学 | 36篇 |
肿瘤学 | 1493篇 |
出版年
2023年 | 152篇 |
2022年 | 277篇 |
2021年 | 459篇 |
2020年 | 374篇 |
2019年 | 478篇 |
2018年 | 571篇 |
2017年 | 468篇 |
2016年 | 439篇 |
2015年 | 536篇 |
2014年 | 650篇 |
2013年 | 950篇 |
2012年 | 1421篇 |
2011年 | 1464篇 |
2010年 | 747篇 |
2009年 | 686篇 |
2008年 | 1200篇 |
2007年 | 1274篇 |
2006年 | 1140篇 |
2005年 | 1134篇 |
2004年 | 1066篇 |
2003年 | 1040篇 |
2002年 | 922篇 |
2001年 | 520篇 |
2000年 | 553篇 |
1999年 | 502篇 |
1998年 | 231篇 |
1997年 | 228篇 |
1996年 | 178篇 |
1995年 | 201篇 |
1994年 | 178篇 |
1993年 | 164篇 |
1992年 | 374篇 |
1991年 | 358篇 |
1990年 | 346篇 |
1989年 | 337篇 |
1988年 | 291篇 |
1987年 | 290篇 |
1986年 | 269篇 |
1985年 | 285篇 |
1984年 | 193篇 |
1983年 | 166篇 |
1982年 | 130篇 |
1981年 | 108篇 |
1980年 | 110篇 |
1979年 | 217篇 |
1978年 | 147篇 |
1977年 | 109篇 |
1976年 | 106篇 |
1974年 | 119篇 |
1972年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
Suyen Karki Eila Laukkanen Helena Länsimies Tomi-Pekka Tuomainen Anna-Maija Pietilä 《Journal of substance use》2019,24(3):300-308
Background: Research has demonstrated that problem behavior has been associated with substance use, but knowledge is lacking on such associations in a low-income country like Nepal. Aims: This study aimed to find associations between emotional and behavioral problems and substance use among Nepalese adolescents. Method: A cross-sectional study was conducted at the end of 2011, with participants from three schools in the Province 4 of Nepal. We selected 408 adolescents aged 12 to 18 (mean 15.2 years, 54% boys) at one urban and two rural schools. The data were collected using the Youth Self-Report and Adolescents’ Substance Use Measurement. Results: Higher scores on withdrawn/depressed symptoms, thought problems, attention problems, delinquent or aggressive behavior or internalizing or externalizing problems were associated with the use of tobacco, alcohol or other substances. In the broadband scales, only internalizing problems predicted the use of intoxicants. Higher scores for attention problems predicted the use of tobacco, any intoxicants, and high-risk user. Conclusion: Our findings indicated that problem behavior among Nepalese adolescents was associated with substance use. Future studies should explore the association between problem behavior and substance use, including causal factors, so that risky behavior among Nepalese adolescents can be prevented. 相似文献
4.
5.
Zinc sulfate addition to glass-ionomer-based cements: influence on physical and antibacterial properties, zinc and fluoride release. 总被引:5,自引:0,他引:5
Prudencio W R Osinaga Rosa Helena M Grande Rafael Y Ballester Maria Regina L Simionato Célia Regina M Delgado Rodrigues Antonio Muench 《Dental materials》2003,19(3):212-217
OBJECTIVES: The aim of this study is to evaluate the effect of ZnSO(4) addition to a conventional glass ionomer and a resin-modified glass ionomer on solubility, flexural strength, zinc and fluoride (F) release, and Streptococcus mutans growth inhibition. METHODS: 5 or 10% ZnSO(4) was added to Vitremer and Ketac-Fil powders. Solubility test was performed based on ISO 7489. Flexural strength was determined by 3-point bending test based on ISO 4049. Zn release/uptake was determined by atomic emission spectrometry; F release/uptake was measured using a F-specific electrode. Both release measurements were performed for 15 d before and 15 d after recharging. Antibacterial test was conducted according to agar plate methods against S. mutans, by measuring the inhibition halos in 1-h and 15-d specimens. Data were analyzed by ANOVA. RESULTS: Solubility increased with higher ZnSO(4) content, but remained below the ISO 7489 limit. Flexural strength was not affected by ZnSO(4) addition, and Vitremer performed better than Ketac-Fil. The control materials released no zinc. Vitremer with 10% ZnSO(4) released the highest amount of zinc. Fluoride release was similar for Ketac-Fil and Vitremer. In both cases, the highest amounts were released in the first 24 h. The growth inhibition halo of S. mutans was similar for both materials with highest content of ZnSO(4) and occurred only with 1-h specimens. SIGNIFICANCE: Zinc addition decreased microorganisms growth and improved fluoride release, without significantly affecting the materials' flexural strength and solubility. 相似文献
6.
Frank A Middleton Marco G Trauzzi Antony E Shrimpton Karen L Gentile Christopher P Morley Helena Medeiros Michele T Pato Carlos N Pato 《American journal of medical genetics. Part B, Neuropsychiatric genetics》2006,(1):28-32
Uniparental isodisomy (iUPD) is a rare genetic condition caused by non-disjunction during meiosis that ultimately leads to a duplication of either the maternal or paternal chromosome in the affected individual. Two types of disorders can result, those due to imprinted genes and those due to homozygosity of recessive disease-causing mutations. Here, we describe the third known case of complete chromosome 4 iUPD of maternal origin. This condition became apparent during whole genome linkage studies of psychiatric disorders in the Portuguese population. The proband is an adult female with normal fertility and no major medical complaints, but a history of major depressive disorder and multiple suicide attempts. The proband's siblings and parents had normal chromosome 4 genotypes and no history of mood disturbance. A brief review of other studies lends support for the possibility that genes on chromosome 4 might confer risk for mood disorders. We conclude that chromosome 4 maternal uniparental disomy (UPD) is a rare disorder that may present with a major depressive phenotype. The lack of a common disease phenotype between this and two other cases of chromosome 4 iUPD [Lindenbaum et al. [1991] Am J Med Genet 49(Suppl 285):1582; Spena et al. [2004] Eur J Hum Genet 12:891-898) would suggest that there is no vital maternal gene imprinting on chromosome 4. However, since there is no reported case of paternal chromosome 4 UPD, paternal gene imprinting on chromosome 4 cannot be excluded. 相似文献
7.
Riitta Suhonen Maritta V?lim?ki Jouko Katajisto Helena Leino-Kilpi 《Journal of Professional Nursing》2006,22(4):253-261
The purposes of this study were to examine how hospital patients' backgrounds and clinical illness are related to their perceptions of the individualized care they receive and to test the sensitivity of the Individualized Care Scale (ICS). Cross-sectional explorative survey data were obtained using questionnaires completed by 861 (response rate = 88%) predischarge hospital patients from six hospitals in Southern Finland in 2004. Self-administered questionnaires included the ICS as well as the 15D, a measure of health-related quality of life, and gathered information about the patients' backgrounds. Based on association tests, younger age, poorer state of health, and higher level of education were associated with more critical perceptions of individualized care. Using simultaneous regression analysis and presenting the results from stronger to weaker, we found age to be the strongest predictor of patients' positive perceptions of the individualized care they received. This was followed by health-related quality of life (HRQoL) as measured by the 15D, vocational education, and type of admission. The ICS was found to be a valid tool for the measurement of individualized care in hospitals. The self-reported patient data from this survey suggest that some patient characteristics are associated with the patients' perceptions about the individualized care they receive. There is now a need to consider how these characteristics can be taken into account in nursing care delivery to increase individualized care for hospital patients. The results also support use of the ICS in the measurement of individualized care in hospitals. 相似文献
8.
Eija Heikkinen MNSc RN Merja Nikkonen PhD RN & Helena Aavarinne PhD RN 《Journal of advanced nursing》1998,27(5):1069-1075
The definition of envy is commonly based on psychoanalytical views of organizational culture. The purpose of this paper is to describe envy in a nursing community. The population study consisted of random sample of 120 subjects drawn from among the employees of one central hospital in Finland. The study material consisted of data collected by questionnaires (response rate 65%). The data were processed by various statistical methods. Open-ended questions were analysed by inductive content analysis. The results of this study indicated that the employee's view of his/her official position in the nursing community, his/her relationships with his/her fellow workers and the management as well as relationships with other nursing communities are all related to envy. The employee's view of his/her official position intensified his/her feelings of envy, if he/she had other negative feelings, anxiety, dissatisfaction with him/herself, and negative feelings towards fellow workers. The major object of envy was fellow workers' salaries. Envy towards other nursing communities was generated by alleged differences in the amount of labour, or by the charge nurse's greater interest in other sections. Employees coped with envy by hiding these feelings and being modest. Women coped with envy by being silent, while men denied the value of the object of envy. 相似文献
9.
P J Hayden C J Welsh Y Yang W H Schaefer A J Ward J L Stevens 《Chemical research in toxicology》1992,5(2):232-237
Nephrotoxic cysteine conjugates derived from a variety of halogenated alkenes are enzymatically activated via the beta-lyase pathway to yield reactive sulfur-containing metabolites which bind covalently to cellular macromolecules. Mitochondria contain beta-lyase enzymes and are primary targets for binding and toxicity. Previously, mitochondrial protein and/or DNA have been considered as molecular targets for cysteine conjugate metabolite binding. We now report that metabolites of nephrotoxic cysteine conjugates form covalent adducts with rat kidney mitochondrial phospholipids. Rat kidney mitochondria were incubated with the 35S-labeled conjugates S-(1,1,2,2-tetrafluoroethyl)-L-cysteine (TFEC), S-(2-chloro-1,1,2-trifluoroethyl)-L-cysteine (CTFC), S-(1,2-dichlorovinyl)-L-cysteine, and S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine. Quantitation of metabolite binding to whole mitochondria and to mitochondrial protein and lipid fractions revealed that as much as 42% of the 35S-label associated with the mitochondria was found in the lipid fraction. Total lipids were also extracted from 35S-treated mitochondria and separated by thin-layer chromatography. 35S-Containing metabolites were found in the lipid fractions from mitochondria treated with each of the conjugates. Lipids from both [35S]CTFC- and [35S]-TFEC-treated mitochondria contained major 35S-labeled lipid adducts which had similar mobility by thin-layer chromatography. Fatty acid analysis, 19F and 31P NMR spectroscopy, and mass spectrometric analyses confirmed that the major TFEC and CTFC adducts are thioamides of phosphatidylethanolamine. 相似文献
10.
Male Sprague-Dawley rats dosed with N-nitrosodiethylamine (NDEA)24 h after two-thirds partial hepatectomy were treated withthe pyrethroid insecticides fenvalerate, flucythrinate or cypermethrinin the diet: for 20 weeks. Altered hepatic foci were analyzedby quantitative stereology from paraffin-embedded sections stainedfor 相似文献