全文获取类型
收费全文 | 533篇 |
免费 | 35篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 24篇 |
妇产科学 | 21篇 |
基础医学 | 72篇 |
口腔科学 | 23篇 |
临床医学 | 55篇 |
内科学 | 80篇 |
皮肤病学 | 19篇 |
神经病学 | 49篇 |
特种医学 | 74篇 |
外科学 | 28篇 |
综合类 | 15篇 |
预防医学 | 30篇 |
眼科学 | 15篇 |
药学 | 28篇 |
中国医学 | 1篇 |
肿瘤学 | 48篇 |
出版年
2022年 | 5篇 |
2021年 | 5篇 |
2019年 | 7篇 |
2018年 | 10篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 18篇 |
2013年 | 24篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 36篇 |
2009年 | 29篇 |
2008年 | 11篇 |
2007年 | 25篇 |
2006年 | 17篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 8篇 |
1999年 | 11篇 |
1998年 | 35篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 14篇 |
1979年 | 6篇 |
1978年 | 12篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1958年 | 2篇 |
1954年 | 2篇 |
1949年 | 2篇 |
排序方式: 共有584条查询结果,搜索用时 15 毫秒
11.
Jun SB Hynd MR Dowell-Mesfin NM Al-Kofahi Y Roysam B Shain W Kim SJ 《Journal of neural engineering》2008,5(2):203-213
Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affect bioactivity, alkaline phosphatase was incorporated into hydrogels and a released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver a brain-derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEAs). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. An increased spontaneous activity as a response to the released BDNF was recorded from the neurons cultured on the top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules. 相似文献
12.
Peripheral blood CD4+CD8+ lymphocytes in cynomolgus monkeys are of resting memory T lineage 总被引:2,自引:0,他引:2
In this study, we analyzed peripheral blood CD4+CD8+ double-positive (DP)
lymphocytes in adult cynomolgus monkeys (Macaca fascicularis). Forty of 55
monkeys had > 5% of the peripheral blood DP subpopulation (9.3 +/- 5.9%;
mean +/- SD) in peripheral blood lymphocytes (PBL) in contrast to a low
percentage of peripheral blood DP cells in humans and mice. In a
cross-sectional study, the peripheral blood DP cells were found to increase
in proportion with age. To clarify whether peripheral blood DP lymphocytes
were immature precursors released from thymus without prior
differentiation, the expressions of CD8 chains and CD1b on peripheral blood
DP lymphocytes were compared with those on thymocytes. The peripheral blood
DP lymphocytes were CD8 alpha + beta- and CD1b-, while thymic DP
lymphocytes were CD8 alpha + beta + and CD1b +, suggesting that the
peripheral blood DP cells are extrathymic T lymphocytes. Furthermore, the
peripheral blood DP lymphocytes exhibited a resting memory T cell phenotype
with CD2hiCD3+CD28-CD29hiCD49dhiCD69- CD80lo. Taken together, adult
cynomolgus monkeys possess a unique peripheral blood DP T cell
subpopulation which expresses a resting memory T cell phenotype. In
addition, similar phenotypic properties of DP lymphocytes were distributed
in the spleen and lymph nodes, although the proportion was less in the
spleen and much less in lymph nodes than in PBL.
相似文献
13.
MC Chau SF Leung KM Kam KY Cheung WH Kwan KH Yu KW Chiu TC Chan 《Journal of Medical Imaging and Radiation Oncology》2007,51(5):480-484
To assess the dosimetric effect of using interpolated contours in planning intensity‐modulated radiation therapy (IMRT) for advanced T‐stage nasopharyngeal carcinoma. The present study focused on T3–T4 tumours where the proximity of targets to neurological organs poses a stringent test on the feasibility of such an approach. Contours of targets and organs were delineated on CT images of 2.5‐mm interval and a reference IMRT plan was generated. An investigative (INV) IMRT plan was then generated with the same planning protocol, but based on interpolated contours that replaced deleted contours on alternate slices. The reference and INV plans were compared. Regarding target coverage, all targets in the INV plans met the acceptance criteria except for the PTV in one case. Regarding organs, the mean dose to 1% volume of the brainstem and spinal cord in the INV plans were kept below their dose limits. No significant differences in the mean doses to others organs were found. Satisfactory target coverage and protection of critical organs to a degree similar to full‐scale contouring could be achieved with use of interpolated contours. The saving in manpower time for contouring is expected to significantly improve the throughput of the IMRT planning process. 相似文献
14.
Sam CK Cheng BScOptom Maurice KH Yap PhD MCOptom FAAO Ernest Goldschmidt MD DrSci Peter G Swann BSc MAppSc FCOptom FAAO honFIES Larry HY Ng PDOptom OD FAAO FBCLA Carly SY Lam PhD MSc MCOptom FAAO 《Clinical & experimental optometry》2008,91(4):373-378
Background: Optomap uses the ultra‐wide field scanning laser ophthalmoscopy to provide retinal examination. It permits fundus examination without the use of a mydriatic, which is more comfortable for the patients. This paper determines the sensitivity and specificity of the Optomap for detecting retinal signs under non‐mydriatic conditions. Methods: Fifty‐four eyes identified with retinal/choroidal signs and eight normal eyes were recruited from 31 Hong Kong Chinese subjects. Photo‐documentation of fundal changes was obtained with the Optomap under non‐mydriatic conditions before a dilated fundus examination by a clinician using standard procedures. The eyelid was retracted using a cotton bud when necessary. Dilated fundus examinations were performed by another clinician using binocular indirect ophthalmoscopy and slitlamp biomicroscopy with a fundus lens. The Optomap images were evaluated by four other investigators under masked condition. The International Classification of Disease, Ninth Revision (ICD‐9‐CM) was adopted for recording retinal features. Screening results were compared with those obtained using the dilated fundus examination as the gold standard. Results: The cotton bud method for eyelid retraction showed an improvement in the area of retina that could be visualised. The sensitivity and specificity of the Optomap averaged 76.4 and 71.9 per cent, respectively. Some fundal signs were missed by all observers in the Optomap but not with the biomicroscope. These included white‐without‐pressure, lattice degeneration, paramacular drusen and pigmentary changes at central fundus. Conclusion: Optomap serves as a reliable screening tool for fundus examination especially because it covers a much wider area of the peripheral retina than other digital instruments for fundus photography. 相似文献
15.
Shaham J Levi Z Gurvich R Shain R Ribak J 《Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine》2000,42(8):843-850
We conducted a cross-sectional study to determine whether occupational exposure to low levels of ethylene oxide can cause hematological abnormalities. Blood samples were collected from a group of 47 hospital workers who were exposed to ethylene oxide during a mean period of 6.6 years (standard error, 1.1). Ethylene oxide range levels measured were < 0.01 to 0.06 ppm. The control group, individually matched by age, sex, and smoking habits, consisted of 88 workers from the administrative sector. We found significant differences between the exposed and the control group in the frequency of workers with white blood cells lower than the normal range. Although there was no significant difference in the absolute mean number of the total white blood cells, we found an elevation in the absolute mean number of monocytes and eosinophils (P < 0.01) and a decrease (P < 0.01) in the absolute mean number of lymphocytes in the exposed group compared with the control group. We also found an elevation (P < 0.01) in the percentage of hematocrit and the mean absolute number of the red blood cells, and a decrease (P < 0.01) in the mean absolute number of platelets, in the exposed group compared with the control group. The mean absolute number of eosinophils, red blood cells, and percentage of hematocrit was significantly higher, and the mean absolute number of lymphocytes and platelets was significantly lower, in the subgroups with a higher cumulative dose of exposure. A positive dose-response was found between cumulative dose exposure and the absolute mean number of eosinophils. In view of our findings, we suggest that the use of complete blood cells with differential in routine medical surveillance and for early detection of hygiene problems should be reexamined with special attention to the eosinophils count. 相似文献
16.
CF Lanata RE Black H Creed-Kanashiro F Lazo ML Gallardo H Verastegui KH Brown 《Acta paediatrica (Oslo, Norway : 1992)》1992,81(S383):98-103
Dietary intake during diarrhea in children less than three years of age was estimated from information recorded on illustrated dietary forms used by children's caretakers during the first week of illness in a prospective community-based study of diarrheal diseases in Lima, Peru. The frequency of consumption and the amount consumed of food groups and selected commonly consumed foods were analyzed by the final duration of the diarrheal episode. Cereals were less frequently consumed during the acute phase of diarrheal episodes that ultimately became persistent (>14 days'duration), apparently shortening the duration of the episode by one day (median duration of four days in children not consuming vs three days in children consuming cereals during diarrhea, p <0.02 Kaplan-Meier logrank test). Only roots and tubers (mainly potatoes) were consumed in greater quantity during episodes that became persistent. There was no evidence that consumption of breast milk or non-maternal milk was associated with an alteration in diarrheal duration. This study provides further evidence of the beneficial effects of continuing feeding during diarrhea using foods available at the home level, especially cereals, which are commonly used in the diet of young children. 相似文献
17.
KH Mak ES Ang ASW Goh KX Na FX Sundram ATH Tan 《Journal of Medical Imaging and Radiation Oncology》1995,39(2):112-117
Technetium-99m hexakis-2-methoxy-isobutyl-isonitrile(99mTc sestamibi) has been used for myocardial perfusion imaging in the evaluation of coronary artery disease (CAD) since 1990. The experience of its use in an Asian population with and without previous myocardial infarction (Ml), diabetes mellitus (DM), hypertension (HPT) and collateral circulation (COL) is reported. One hundred and thirty-nine patients who underwent treadmill exercise testing with 99mTc sestamibi single photon emission computed tomography (SPECT) and coronary angiogram were studied. The overall sensitivity for the detection of CAD was 91.0% and specificity was 64.7%. For patients without previous myocardial infarction, the sensitivity was 83.8% and specificity was 83.3%. Patients with COL had a higher sensitivity while those with HPT had a lower specificity. Sensitivity was higher in patients with multi-vessel disease (MVD) than single vessel disease (SVD). The overall detection for individual artery stenosis was 74.1% with a specificity of 73.1 %. Amongst the three major coronary arteries, sensitivity was highest for the right coronary artery and specificity was highest for the left circumflex artery. Specificity was higher in patients without MI or COL. We found that the agreement between 99mTc sestamibi SPECT and coronary angiogram for the extent of CAD was only 52.5%. The concordance rate was higher for patients with MVD than SVD. It is concluded that 99mTc sestamibi SPECT is a sensitive and specific test for the detection of CAD and localization of disease to individual coronary arteries in our patients with some differences in the subgroups. Agreement between coronary angiogram and 99mTc sestamibi for the extent of coronary artery disease was also satisfactory. 相似文献
18.
Multivariate analyses of data from 248 married women scheduled for tubal sterilization and 165 wives of men scheduled for vasectomy indicated that male and female sterilization methods were selected for different reasons and under different circumstances. More specifically, the woman who underwent tubal sterilization was more likely to have perceived that she had greater influence than her husband over the sterilization decision, to have had cesarean section or vaginal delivery in association with sterilization, to have chosen tubal ligation because her spouse refused to undergo the alternative procedure or because it was convenient to combine it with delivery or other surgery, and to have had a spouse who was unwilling to be sterilized because of possible side effects associated with vasectomy. The woman whose husband underwent vasectomy was more likely to have been very fearful of surgery in general or especially fearful of reproductive surgery, to have known many men who already had had a vasectomy, to have perceived that her husband was more strongly motivated than herself to terminate childbearing, to have had a spouse who participated in birth control, and to have chosen vasectomy because it was easier or less expensive or because her physician advised against tubal sterilization. 相似文献
19.
20.
Benzo[a]pyrene at an environmentally relevant dose is slowly absorbed by, and extensively metabolized in, tracheal epithelium 总被引:2,自引:0,他引:2
Gerde P; Muggenburg BA; Thornton-Manning JR; Lewis JL; Pyon KH; Dahl AR 《Carcinogenesis》1997,18(9):1825-1832
While tobacco smoke has been conclusively identified as a lung carcinogen,
there is much debate over which smoke constituent(s) are primarily
responsible for its carcinogenicity. Previous studies in our laboratory
suggested that highly lipophilic carcinogens are slowly absorbed in the
thicker epithelium of the conducting airways, potentially allowing for
substantial local metabolism. The bioactivation of polycyclic aromatic
hydrocarbons in airway epithelium may, hence, be important in tobacco
smoke-induced carcinogenesis. In the present study, the hypothesis of slow
absorption and substantial local metabolic activation of highly lipophilic
carcinogen in airway epithelium was tested in dogs. A single dose of
tritiated benzo[a]pyrene (BaP) dissolved in a saline/phospholipid
suspension was instilled in the trachea, just anterior to the carina. At
intervals of a few minutes up to 30 min over a 3-h period, blood samples
were drawn from the azygous vein, which drains the area around the point of
instillation, and from the systemic circulation. Tissue samples were taken
at the end of the experiment. The concentration of BaP with depth into the
tracheal mucosa was determined with autoradiography. BaP was slowly
absorbed into the trachea with a half-time of approximately 73 min, which
is consistent with diffusion-limited passage through the epithelium and
lead to local doses in the tracheal epithelium that were more than a
1000-fold those of other tissues. The long retention of BaP in the
epithelium provided the local metabolizing enzymes with high substrate
levels over a long period, resulting in extensive metabolism. At 3 h after
the exposure, 23% of the BaP-equivalent activity remained in the tracheal
mucosa. Of this fraction, 13% was parent compound, 28% was organic
extractable, 31% was water-soluble, and 28-7% of the instilled dose was
bound to tracheal tissues. These results explain the tendency of highly
lipophilic carcinogens, such as BaP, to induce tumors at the site of entry
and, furthermore, indicate that the highly lipophilic components of tobacco
smoke and polluted air may be the most important contributors to lung
tumors of the conducting airways.
相似文献