全文获取类型
收费全文 | 34204篇 |
免费 | 3738篇 |
国内免费 | 976篇 |
专业分类
耳鼻咽喉 | 321篇 |
儿科学 | 416篇 |
妇产科学 | 388篇 |
基础医学 | 2085篇 |
口腔科学 | 9673篇 |
临床医学 | 2135篇 |
内科学 | 2578篇 |
皮肤病学 | 610篇 |
神经病学 | 628篇 |
特种医学 | 531篇 |
外国民族医学 | 3篇 |
外科学 | 1394篇 |
综合类 | 4160篇 |
现状与发展 | 3篇 |
预防医学 | 1951篇 |
眼科学 | 177篇 |
药学 | 7601篇 |
30篇 | |
中国医学 | 2450篇 |
肿瘤学 | 1784篇 |
出版年
2024年 | 63篇 |
2023年 | 633篇 |
2022年 | 792篇 |
2021年 | 1379篇 |
2020年 | 1532篇 |
2019年 | 1493篇 |
2018年 | 1370篇 |
2017年 | 1348篇 |
2016年 | 1347篇 |
2015年 | 1375篇 |
2014年 | 2008篇 |
2013年 | 2539篇 |
2012年 | 2008篇 |
2011年 | 2163篇 |
2010年 | 1710篇 |
2009年 | 1430篇 |
2008年 | 1512篇 |
2007年 | 1536篇 |
2006年 | 1388篇 |
2005年 | 1302篇 |
2004年 | 1094篇 |
2003年 | 1009篇 |
2002年 | 860篇 |
2001年 | 738篇 |
2000年 | 661篇 |
1999年 | 520篇 |
1998年 | 469篇 |
1997年 | 521篇 |
1996年 | 384篇 |
1995年 | 338篇 |
1994年 | 340篇 |
1993年 | 252篇 |
1992年 | 294篇 |
1991年 | 280篇 |
1990年 | 238篇 |
1989年 | 230篇 |
1988年 | 204篇 |
1987年 | 184篇 |
1986年 | 159篇 |
1985年 | 200篇 |
1984年 | 201篇 |
1983年 | 159篇 |
1982年 | 134篇 |
1981年 | 110篇 |
1980年 | 80篇 |
1979年 | 63篇 |
1978年 | 51篇 |
1977年 | 68篇 |
1976年 | 46篇 |
1975年 | 35篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Hiroko Utsunomiya Wanninayake M. Tilakaratne Kazufumi Oshiro Satoshi Maruyama Makoto Suzuki Hiroko Ida-Yonemochi Jun Cheng Takashi Saku 《Journal of oral pathology & medicine》2005,34(8):498-507
BACKGROUND: Oral submucous fibrosis (OSF) is a chewing habit-related pre-cancerous condition of the oral mucosa affecting predominantly south Asians. It is histopathologically characterized by epithelial atrophy and fibrosis of the subepithelial connective tissue. Fibrosis extends all the way into the muscle layer, leading to difficulty in mouth opening. However, the dynamics of extracellular matrix (ECM) remodeling with OSF progression is largely unknown. METHODS: Forty biopsy specimens of OSF and 10 of normal buccal mucosa were examined for expression/deposition modes of eight ECM molecules by histochemistry, immunohistochemistry, and in situ hybridization. RESULTS: In the early stage of OSF, tenascin, perlecan, fibronectin, collagen type III were characteristically enhanced in the lamina propria and the submucosal layer. In the intermediate stage, the ECM molecules mentioned above and elastin were extensively and irregularly deposited around muscle fibers. In the advanced stage, such ECM depositions decreased and were entirely replaced with collagen type I only. Their gene expression levels varied with progression of fibrosis, but the mRNA signals were confirmed in fibroblasts in the submucosal fibrotic areas. CONCLUSIONS: The results indicate that the ECM remodeling steps in OSF are similar to each phase of usual granulation tissue formation. Restricted mouth opening may be a result of loss of variety of ECM molecules including elastin into the homogeneity of collagen type I replacing muscle fibers. 相似文献
82.
Objective: This pilot study was intended to test whether a training protocol improved validity of odor judges (OJs), with or without experience, and whether odorant types differed in error proneness.
Methods: The OJs (four experienced, two inexperienced) completed a 4-phase training protocol based on the American Society of Testing and Materials standards (ASTM): (i) introduction to sensory scales, n-butanol reference, sniffing techniques; (ii) pretraining measurements; 20 samples of varying intensities of four unpleasant and three pleasant odorants; (iii) exercises assessing quality, intensity, ranking, and matching; and (iv) post-training measurements.
Main outcome measures: Subjects' intensity scores were analyzed as the absolute difference from the 'true' intensity (ASTM n-butanol standard) using repeated measures ANOVA.
Results: Training significantly ( P = 0.02) reduced OJ errors. Experienced and novice judges did not differ in average errors ( P = 0.99), or in improvement in error from pre- to post-training ( P = 0.94). Improvement was consistent from pre- to post-training for all odorants except dimethylsulfide for which errors worsened ( P = 0.01). Unpleasant and pleasant odorants differed ( P = 0.006) in error. After removing water the effects of water control scores from the pleasant odorants, the difference was not significant ( P = 0.26).
Conclusions: The OJs improved in their ability to assess odor intensity irrespective of previous experience. Training is recommended for all OJs prior to research trials. 相似文献
Methods: The OJs (four experienced, two inexperienced) completed a 4-phase training protocol based on the American Society of Testing and Materials standards (ASTM): (i) introduction to sensory scales, n-butanol reference, sniffing techniques; (ii) pretraining measurements; 20 samples of varying intensities of four unpleasant and three pleasant odorants; (iii) exercises assessing quality, intensity, ranking, and matching; and (iv) post-training measurements.
Main outcome measures: Subjects' intensity scores were analyzed as the absolute difference from the 'true' intensity (ASTM n-butanol standard) using repeated measures ANOVA.
Results: Training significantly ( P = 0.02) reduced OJ errors. Experienced and novice judges did not differ in average errors ( P = 0.99), or in improvement in error from pre- to post-training ( P = 0.94). Improvement was consistent from pre- to post-training for all odorants except dimethylsulfide for which errors worsened ( P = 0.01). Unpleasant and pleasant odorants differed ( P = 0.006) in error. After removing water the effects of water control scores from the pleasant odorants, the difference was not significant ( P = 0.26).
Conclusions: The OJs improved in their ability to assess odor intensity irrespective of previous experience. Training is recommended for all OJs prior to research trials. 相似文献
83.
Jessica Swoboda DDS H. Asuman Kiyak MA PhD Rigmor E. Persson DDS MSD G. Rutger Persson DDS PhD David K. Yamaguchi PhD Michael I. MacEntee LDS FRCD© PhD Christopher C.L. Wyatt BSc DMD MSc 《Special care in dentistry》2006,26(4):137-144
There is limited information regarding oral health status and other predictors of oral health‐related quality of life. An association between oral health status and perceived oral health‐related quality of life (OHQOL) might help clinicians motivate patients to prevent oral diseases and improve the outcome of some dental public health programs. This study evaluated the relationship between older persons' OHQOL and their functional dentition, caries, periodontal status, chronic diseases, and some demographic characteristics. A group of 733 low‐income elders (mean age 72.7 ISD=4.71, 55.6% women, 55.1% members of ethnic minority groups in the U.S. and Canada) enrolled in the TEETH clinical trial were interviewed and examined as part of their fifth annual visit for the trial. OHQOL was measured by the Geriatric Oral Health Assessment Index (GOHAI); oral health and occlusal status by clinical exams and the Eichner Index; and demographics via interviews. Elders who completed the four‐year assessment had an average of 21.5 teeth (SD=6.9). with 8.5 occluding pairs (SD=4.6), and 32% with occlusal contacts in all four occluding zones. Stepwise multiple regressions were conducted to predict total GOHAI and its subscores (Physical, Social, and Worry). Functional dentition was a less significant predictor than ethnicity and being foreign‐bom. These variables, together with gender, years since immigrating, number of carious roots, and periodontal status, could predict 32% of the variance in total GOHAI, 24% in Physical, 27% in Social, and 21 % in the Worry subscales. These findings suggest that functional dentition and caries influence older adults' OHQOL, but that ethnicity and immigrant status play a larger role. 相似文献
84.
85.
86.
Chretien Marie Francoise; Lebouvier Brigitte; Denis Alain; Chappard Daniel 《Human reproduction (Oxford, England)》1998,13(10):2767-2771
A cytomorphometric analysis of superficial vaginal cells inwomen in three groups of different types of hormonal concentrationwas made. There were 15 women in each group. Group I was studiedduring a natural cycle, group II under oral contraceptive therapyand group III during an in-vitro fertilization (IVF) stimulationprotocol. Morphometric parameters were measured on an imageanalyser. The area, perimeter and several form factors weremeasured separately for nuclei and cytoplasm. The nucleus:cytoplasmicratio was also determined. The cytoplasmic area was significantlyreduced in group II and was associated with a statisticallysignificant reduction of the nuclear area. The nucleus:cytoplasmicratio appeared significantly increased in group II and reducedin group III. Low oestradiol impregnation obtained with an oralminidosed contraceptive interfered with vaginal cell maturation.High oestradiol concentrations obtained during IVF protocolsinduced marked nuclear pycnosis but did not induce supra-physiologicalcell enlargement. Maximal cell size is genetically regulatedaccording to Driesch's law of volume invariance and hormonalover-stimulation has no effect on cell size. The nucleus:cytoplasmicratio appears to be a powerful parameter reflecting the oppositeeffects of hormones on cell compartments. 相似文献
87.
The interactive role of mucosal T lymphocytes in intestinal growth, development and enteropathy 总被引:2,自引:0,他引:2
Abstract Over the past 15–20 years, research has progressively focused on the mucosal T cell as the central factor in the initiation of physiological or pathological changes, first in the growth and maturation of the early (postnatal) intestine, and second in adult-type enteropathies resulting from sensitivity to either food or pathogen-derived antigens. T cell-mediated events may be measured, for example, in terms of specific immunopathologic patterns of change and injury, such as type 1 (lymphocyte infiltration), type 2 (crypt hyperplasia) and type 3 (flat-destructive), which can be recognized and quantitated microscopically; by determination of lymphocyte reactivity through secretion of interleukin-2 receptors (IL-2R) into plasma or expression by mucosal lymphocytes; by quantitation of lymphocyte subsets emigrating into inflamed tissues by immunoperoxidase-labelled monoclonal antibodies; or by the determination of T cell receptor polymorphisms. Alterations in intestinal growth, structure and function at weaning are likely to be T cell-mediated as they are analogous to the same type 1/2 lesions that reflect modulation of adult mucosal architecture in food and parasite-induced hypersensitivity reactions. Enteropathies associated with HIV infection and T cell deficiency display a milder degree of villous flattening and impaired crypt hyperplasia than that typical of gluten-sensitivity, suggesting a reversion to lesser degrees of mucosal pathology (type 1/2). Clearly more information will accrue; meanwhile the remarks in this brief survey should provide a firm basis whereby clinician and scientist can meet, and together recognize and further dissect the modulatory effect of T lymphocytes on mucosal structure and function. 相似文献
88.
枢复宁在肺癌患者体内的药物动力学和生物利用度 总被引:3,自引:1,他引:2
9名接受顺铂化疗的原发性肺癌患者单次口服和静脉注射枢复宁8mg后,用反相高效液相色谱法测定血浆药物浓度。经用PKBP-N1程序在计算机上拟合计算表明,枢复宁在人体内表现为二房室模型。口服后主要药动学参数:T1/2Ka=0.41±0.30h,T1/2α=0.9±0.43h,T1/2β=3.3±1.2h,Cmax=28.6±9.5ng/ml,Tmax=1.7±0.9h,AUC=158±73ng·h/ml,绝对生物利用度为55%。 相似文献
89.
Fix Joseph A. Alexander Jose Cortese Margot Engle Karen Leppert Paula Repta A. J. 《Pharmaceutical research》1990,7(4):384-387
Short-chain alkyl esters of L-dopa were administered to rats and mice via oral and rectal routes. Plasma L-dopa esters and L-dopa were determined in the systemic and portal circulation by HPLC. A comparison of isopropyl, butyl, and 4-hydroxybutyl esters of L-dopa demonstrated significantly higher levels of the esters in both systemic and portal blood samples following rectal administration than following oral administration. In most cases, oral administration resulted in nondetectable (<0.01 µg/ml) levels of the esters in plasma. Correspondingly, the plasma levels of L-dopa itself were consistently higher following rectal administration. At very high oral doses (500 mg L-dopa equivalents/kg body weight), systemic plasma levels of the butyl ester could be detected (1.25 µg/ml at 10 min), which might indicate saturation of the esterase activity of the small intestine. These studies indicate that the systemic availability of L-dopa from short-chain alkyl esters of L-dopa may be best optimized by rectal administration, which avoids the relatively high esterase activity characteristic of the small intestine. 相似文献
90.
Norethisterone enanthate (NET-En), an established intramuscular long-acting contraceptive agent, has previously been shown to be effective in inhibiting fertility in two rodent species even 4 days after oral ingestion. Pharmacokinetics of NET and NET-En were studied after oral and intramuscular doses in two animal species and a few women. The results suggest that the NET-En was absorbed within a day in all the species after oral dose. The estimates of relative bioavailability ranged from 13 to 51% in rabbits, monkeys, and women. The elimination half-life was 5–10 days. The presence of the active component, NET, in the circulation over the experimental period of 15 days suggests that NET-En could be useful as a long-acting oral pill. The suppression of progesterone levels during the luteal phase of menstrual cycle in women also supports this finding. 相似文献