全文获取类型
收费全文 | 22746篇 |
免费 | 2277篇 |
国内免费 | 535篇 |
专业分类
耳鼻咽喉 | 129篇 |
儿科学 | 1179篇 |
妇产科学 | 1000篇 |
基础医学 | 2392篇 |
口腔科学 | 576篇 |
临床医学 | 1877篇 |
内科学 | 2669篇 |
皮肤病学 | 285篇 |
神经病学 | 1715篇 |
特种医学 | 701篇 |
外国民族医学 | 2篇 |
外科学 | 1422篇 |
综合类 | 2730篇 |
一般理论 | 3篇 |
预防医学 | 3539篇 |
眼科学 | 715篇 |
药学 | 2705篇 |
15篇 | |
中国医学 | 893篇 |
肿瘤学 | 1011篇 |
出版年
2024年 | 37篇 |
2023年 | 317篇 |
2022年 | 501篇 |
2021年 | 1019篇 |
2020年 | 920篇 |
2019年 | 846篇 |
2018年 | 783篇 |
2017年 | 909篇 |
2016年 | 950篇 |
2015年 | 861篇 |
2014年 | 1465篇 |
2013年 | 1759篇 |
2012年 | 1258篇 |
2011年 | 1414篇 |
2010年 | 1136篇 |
2009年 | 1042篇 |
2008年 | 985篇 |
2007年 | 940篇 |
2006年 | 901篇 |
2005年 | 804篇 |
2004年 | 634篇 |
2003年 | 586篇 |
2002年 | 520篇 |
2001年 | 437篇 |
2000年 | 354篇 |
1999年 | 350篇 |
1998年 | 305篇 |
1997年 | 305篇 |
1996年 | 268篇 |
1995年 | 234篇 |
1994年 | 255篇 |
1993年 | 214篇 |
1992年 | 224篇 |
1991年 | 198篇 |
1990年 | 181篇 |
1989年 | 184篇 |
1988年 | 164篇 |
1987年 | 133篇 |
1986年 | 130篇 |
1985年 | 166篇 |
1984年 | 124篇 |
1983年 | 90篇 |
1982年 | 99篇 |
1981年 | 80篇 |
1980年 | 96篇 |
1979年 | 81篇 |
1978年 | 62篇 |
1977年 | 65篇 |
1976年 | 50篇 |
1975年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
C. I. V. FRANKLIN 《Journal of Medical Imaging and Radiation Oncology》1991,35(1):68-71
The records of 108 adult patients with supratentorial low grade astrocytoma presenting between 1/1/80 and 31/12/87 were examined for the following factors which might affect survival: patient age, extent of surgical resection, site of tumour, tumour grade, radiation field size and radiation dose. Univariate analysis showed that patient age, field size and radiation dose were significant prognostic factors, but with multivariate analysis only patient age and radiation field size were significant independent variables. It is possible that field size is a proxy variable for tumour size. 相似文献
32.
在这篇文章中,应用圆形分布法计算了泰安市1984—1985两年流行出血热的发病平均日期,分别为1984年11月5号和1985年11月11号,两年合计的平均发病日期为11月9号。另外,还分析了发病的年龄和职业。这将为预防工作提供准确的科学数据。 相似文献
33.
Tissue distribution and pharmacodynamics of verapamil were evaluated during steady state intravenous (i.v.) infusion and after single dose intraperitoneal (i.p.) drug administration to female Sprague-Dawley rats. In one group of rats, verapamil was infused to a steady state concentration at which time animals were killed. Verapamil-induced decreases in mean arterial pressure (MAP) were monitored during infusion and correlated with concomitantly obtained plasma verapamil concentrations. Tissue (lung, liver, renal medulla, renal cortex, cardiac muscle, skeletal muscle, perirenal fat, brain stem, cerebral cortex, and cerebellum) and plasma samples were obtained immediately after animals were killed and verapamil and norverapamil concentrations determined. Another group of rats, after receiving i.p. verapamil, were killed at 1, 3, 5, 19, and 24 h. Elimination from each tissue evaluated was described by a first order process. Elimination half-life of verapamil was similar among plasma and tissues evaluated (1.5 to 2.2 h). The per cent verapamil not bound to plasma proteins was concentration-independent and similar between rats receiving i.p. (mean +/- S.D.) (2.28 +/- 0.72 per cent) and i.v. (2.08 +/- 0.03 per cent) verapamil. MAP and verapamil concentration in plasma (r = 0.75; p less than 0.01) and cardiac muscle (r = -0.82; p less than 0.01) were inversely correlated in a highly significant fashion during both i.v. and i.p. drug administrations. The tissue-to-plasma distribution ratio for verapamil and norverapamil was similar among animals receiving i.p. verapamil at all points of sampling, suggesting distribution equilibrium had been achieved. After steady state i.v. infusion, both verapamil and norverapamil tissue: plasma concentration ratios were greater than after i.p. administration. Higher tissue: plasma verapamil concentration ratios after i.v. administration than after i.p. administration suggest either only a pseudoequilibrium is attained after i.p. administration or that determinants of tissue distribution of racemic verapamil differ with different routes of drug administration. In these studies, MAP provided a reasonable pharmacodynamic marker for verapamil tissue and plasma concentrations. 相似文献
34.
35.
Seunghan Ha Minhee Lee Onseok Lee Gunwoo Lee Jeayoung Kim Jongsub Moon Mingi Kim Chilhwan Oh 《Skin research and technology》2009,15(2):200-213
Background/aims: The objective and quantitative assessment of the skin is important in medical and cosmeceutical research. Assessment of color is an important element for analyzing the surface of the skin, which is usually determined subjectively by a doctor or using color analysis devices. These devices, however, cannot provide correct color information because color is construed from the mean value of the observation region, and analysis of color distribution is impossible. The purpose of this paper is to develop an objective analysis method to permit skin color measurement of each pixel unit of an image and analyze the distribution of skin surface color. Methods: The Skin Color Distribution Analyzer (SCDA) is an analysis method newly developed at the Research Institute for Skin Image at Korea University. The SCDA system presented in this paper performed a novel form of quantitative and objective analysis of skin color distribution using each pixel color model parameter found in image wavelength information. In this paper, distribution analysis was conducted on normal skin and skin lesions and skin affected by artificially induced irritant contact dermatitis and pigmented nevous. The method selected a grade using a color model parameter. Twenty healthy Korean males participated in this study. A comparative study of the eight anatomical areas was performed, including the exposure and non‐exposure parts and the medial aspect and the lateral aspect of the forearm. A reliability test for the SCDA system was also conducted with a spectrometer (SPEC) using the color analysis method. Results: Each skin lesion was precisely segmented by grade and each parameter hada different statistical significance for results of analysis of distribution in pigmented nevous and the artificially induced irritant contact dermatitis. Parameters L*, b*, a*, and EI showed salient traits. Showed resemble measured result in the SCDA system and the SPEC of normal skin. The exposed site, in comparison with the non‐exposed site, showed a notable difference in the L* parameter and a significant statistical difference in the x and z parameters, except b*. The comparison of the medial and lateral aspects of the forearm showed a notable difference in the L* parameter and a significant statistical difference in the parameters except y and b*. In the reliability test result using the SCDA system and the SPEC, the SCDA system was highly reliabile in terms of the CV value in all color model parameters. Conclusions: The color distribution analysis method using the SCDA system has revealed an aspect that the existent method of medical research has not shown, and is considered to be more reliable than other methods. This method can provide better study findings because it can be applied to other fields in addition to the medical science field and the ripple effect is thought to be bigger in other science field too. 相似文献
36.
Age determines memory for face identity and expression 总被引:1,自引:1,他引:0
Egemen SAVASKAN Sandra Elisabeth MÜLLER reas BÖHRINGER Christine PHILIPPSEN Franz MÜLLER-SPAHN Hartmut SCHÄCHINGER 《Psychogeriatrics》2007,7(2):49-57
Background: The recognition of facial expressions is an important component of emotion processing which contributes to interactional behavior. One of the factors highly associated with potential decline of ability in behavioral tasks is age. Methods: We have investigated age‐related changes in facial identity and expression memory of healthy subjects in three age groups: young adults (20–40 years), elderly adults (60–80 years) and, for the first time in the literature, very old adults (over 80 years of age). Using a picture test, photographs of faces with happy or angry expressions were presented to study participants during the encoding task, and the memory for identity and emotional facial expression was investigated in a subsequent recognition task showing emotionally neutral faces. Half of the faces presented in the recognition task were initially shown in the encoding task. Results: Age interacted with the memory process: the ability to recognize both facial identity and emotional expression declined with advanced age. Happy facial expressions were better recognized in all age groups. Although there was a continuous overall decrease in recognition of both happy and angry expressions with advanced age, the effect favoring happy facial expressions was stable also in very old adults. Other factors such as gender or educational level did not affect the memory process for facial expressions. Conclusions: Our findings suggest that age is a significant determinant of memory for facial identity and emotional expression, and that, similar to younger adults, the recognition process of the elderly favors happy emotional facial expressions. 相似文献
37.
目的探讨目前老年护理医院院内感染病原菌及其耐药特征。方法对2000年4月-2004年3月徐汇区两家老年护理院出院病人的病史进行统计分析。结果两家老年护理院共计发生医院感染939例次,医院感染率12.86%,检出病原菌284株,阳性率30.28%;病原菌以革兰阴性菌为主,占44.65%,其次为真菌、革兰阳性菌,分别为29.12%、25.92%,位于前3位的病原菌分别为其他真菌(14.36%)、白色念珠菌(12.23%)、铜绿假单胞菌(8.69%);除嗜麦芽寡养单胞菌外,革兰阴性菌以亚胺培南最敏感,敏感率87%,对氨苄西林、阿莫西林的耐药率〉51%,对头孢哌酮、哌拉西林的耐药率〉33%;MRSA和MRSE的检出率高达86.76%和76.32%;混合感染率34.51%。结论老年护理院医院感染率高.真菌所占的比例高;细菌对抗菌药物的耐药性相当严重。 相似文献
38.
The objective of this study is to determine whether a normal fetal morphology ultrasound scan in women older than 35 years reduces the risk of aneuploidy. We reviewed the results of amniocentesis and second trimester sonogram in all women older than 35 years from 1991 to 1995. None had prior screening. We excluded fetuses with structural anomalies. We determined the sensitivity and specificity of minor markers in detecting Down syndrome and also determined the reduction in risk of a normal sonogram. Among the 2060 women older than 35 years giving birth during the study period, 16 (0.78%) delivered an infant with Down syndrome. Of the 16 fetuses, two had no prenatal testing or ultrasound, two had invasive testing but no second trimester sonogram, five had a normal sonogram and seven had one or more sonographic markers of Down syndrome. At least 17% of women older than 35 years did not participate in prenatal testing or ultrasound. Ultrasound detected Down syndrome with a sensitivity of 59% (95% confidence interval: 45–72%), a false‐positive rate of 10.6% (9.4–11.8%) and a positive predictor value of 1 in 9. The likelihood of having normal karyotype if the sonogram was normal was 0.46 (0.31–0.61). In women older than 35 years, a normal second trimester sonogram reduces the risk of Down syndrome by more than 50%. At least 17% of women older than 35 years do not participate in prenatal testing or ultrasound. 相似文献
39.
目的 定性了解矿山巷道内气溶胶的浓度和粒径分布特性。方法 在巷道内的不同区间,分别用凝结核颗粒计数器和个人气溶胶测量仪巡测气溶胶的粒子数和质量浓度,并通过质量浓度的分级测量定性评价微米级气溶胶的粒径分布;在调度室内外,用金属丝网筛扩散法测量亚微米级气溶胶的粒径分布。结果 巷道内可吸入颗粒物(PM10)的平均质量浓度为0.42 mg/m3,其量值大小因工作断面而异,且受人工活动影响变化较大;巷道内粒径大于1.0 μm的颗粒物广泛存在,而粒子直径小于5 nm的气溶胶基本上未被检出。结论 矿山巷道内气溶胶特性因工作断面、人工活动和通风条件的不同而变化明显,在开展内照射剂量评价时应考虑粒径大于1.0 μm放射性气溶胶粒子的剂量贡献。 相似文献
40.
In a genetic epidemiology study of a trait, prior to collecting genotype data the foremost task is to test for familial aggregation and examine heritability. Recently, functional traits have drawn attentions from investigators. Here, to test for familial aggregation of a functional trait in the family studies, a test constructed based on the leading functional principal component of heritability, which is a summary measure of temporal genetic variation in a functional trait, is proposed. The p‐value of the test can be approximated by a permutation procedure given the family structure. The asymptotic distribution of the test statistic is derived. Simulations are carried out to examine the size and the power of the test. The proposed methods are applied to the total cholesterol data in the Framingham Heart Study. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献