全文获取类型
收费全文 | 3174篇 |
免费 | 294篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 38篇 |
儿科学 | 113篇 |
妇产科学 | 80篇 |
基础医学 | 315篇 |
口腔科学 | 43篇 |
临床医学 | 386篇 |
内科学 | 675篇 |
皮肤病学 | 35篇 |
神经病学 | 329篇 |
特种医学 | 169篇 |
外科学 | 462篇 |
综合类 | 57篇 |
预防医学 | 392篇 |
眼科学 | 34篇 |
药学 | 193篇 |
中国医学 | 7篇 |
肿瘤学 | 167篇 |
出版年
2022年 | 22篇 |
2021年 | 39篇 |
2020年 | 25篇 |
2019年 | 41篇 |
2018年 | 54篇 |
2017年 | 24篇 |
2016年 | 38篇 |
2015年 | 44篇 |
2014年 | 67篇 |
2013年 | 108篇 |
2012年 | 147篇 |
2011年 | 162篇 |
2010年 | 84篇 |
2009年 | 85篇 |
2008年 | 141篇 |
2007年 | 144篇 |
2006年 | 133篇 |
2005年 | 104篇 |
2004年 | 122篇 |
2003年 | 118篇 |
2002年 | 139篇 |
2001年 | 112篇 |
2000年 | 91篇 |
1999年 | 96篇 |
1998年 | 63篇 |
1997年 | 65篇 |
1996年 | 37篇 |
1995年 | 40篇 |
1994年 | 45篇 |
1993年 | 41篇 |
1992年 | 75篇 |
1991年 | 79篇 |
1990年 | 62篇 |
1989年 | 69篇 |
1988年 | 79篇 |
1987年 | 75篇 |
1986年 | 76篇 |
1985年 | 63篇 |
1984年 | 36篇 |
1983年 | 27篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 38篇 |
1978年 | 24篇 |
1977年 | 26篇 |
1976年 | 22篇 |
1975年 | 18篇 |
1974年 | 39篇 |
1973年 | 19篇 |
1971年 | 17篇 |
排序方式: 共有3495条查询结果,搜索用时 15 毫秒
31.
OBJECTIVES: To evaluate the feasibility of implementing 3 specific prompting methods among students in the first and fourth grades (mean age = 7.2 and 10.1 years, respectively), to validate recall accuracy of first- and fourth-grade students against observation, to develop a single measure of inaccuracy that cumulated errors in reporting food items and amounts without allowing underreporting and overreporting to cancel each other, and to establish information regarding the measure of inaccuracy for use in future studies. DESIGN: Children were interviewed the morning after they were observed eating lunch provided by the school. Interviews included free recall, nonsuggestive prompted recall, and specific prompted recall (either preference, food category, or visual). SUBJECTS/SETTING: Ninety-six children (48 students per grade) were studied--32 per the specific prompting method--stratified by grade, sex, and ethnicity (African-American or white). Specific prompting method was randomly assigned to children within strata. STATISTICAL ANALYSIS: Food items were categorized and weighted as: combination entree = 2, condiments = 1/3, and other = 1. To calculate inaccuracy of recall, absolute differences between amounts reported and observed eaten were calculated for each item and then multiplied by each item's weight; these values were then summed across all items for each child. Inaccuracy of recall was determined before specific prompting and after specific prompting and for the difference (inaccuracy after specific prompting minus inaccuracy before specific prompting). RESULTS: Before specific prompting, median inaccuracy was 2.7 servings for the 48 first-grade students and 1.7 servings for the 48 fourth-grade students. The median difference in inaccuracy from before to after specific prompting was 0 for both grades. Specific prompting increased recall accuracy for 9 first-graders and 12 fourth-graders, but decreased recall accuracy for 21 first-graders and 7 fourth-graders, and did not change recall accuracy for 18 first-graders and 29 fourth-graders. Among children whose recall accuracy increased after specific prompting, 5 first-graders and 8 fourth-graders received prompting for food category. APPLICATIONS/CONCLUSIONS: Among first-grade students, specific prompting (either preference, food category, or visual) may hurt more than help recall accuracy. Among fourth-grade students, prompting for food category yields small gains in recall accuracy with minimal losses. Validation studies are needed with larger sample sizes to determine prompting methods that produce more accurate dietary recalls from children of various socioeconomic status groups, other racial/ethnic groups, and at other meals. 相似文献
32.
Incidence of urinary incontinence and constipation during pregnancy and postpartum: survey of current findings at the Rotunda Lying-in Hospital 总被引:5,自引:0,他引:5
Kathleen Marshall Superintendent Physiotherapist Kate A. Thompson Research Officer † Deirdre M. Walsh Lecturer † George D. Baxter Professor † 《BJOG : an international journal of obstetrics and gynaecology》1998,105(4):400-402
Objective To assess the impact of pregnancy upon continence and constipation.
Design A questionnaire survey.
Setting Maternity wards in the Rotunda Lying In Hospital, Dublin, Republic of Ireland.
Population 7771 women who were delivered of liveborn infants.
Methods Questionnaires were delivered and collected by physiotherapy staff as part of routine postnatal care.
Results Analysis of data using χ2 tests showed significant differences between three parity groups [primigravidae, multigravidae (2–4) and multigravidae (5+)] for symptoms of both urinary incontinence ( χ2 = 119.54 , df = 2, P = 0.000) and constipation ( χ2 = 12.53 , df = 3, P = 0.002); the incidence of both constipation and urinary incontinence increased with parity.
Conclusion The results of this survey have emphasised the relation between parity and postpartum incontinence which stresses the importance of early diagnosis and intervention. 相似文献
Design A questionnaire survey.
Setting Maternity wards in the Rotunda Lying In Hospital, Dublin, Republic of Ireland.
Population 7771 women who were delivered of liveborn infants.
Methods Questionnaires were delivered and collected by physiotherapy staff as part of routine postnatal care.
Results Analysis of data using χ
Conclusion The results of this survey have emphasised the relation between parity and postpartum incontinence which stresses the importance of early diagnosis and intervention. 相似文献
33.
Serotonin (5-HT) 5-HT(2A) and 5-HT(2C) receptors are thought to play important roles in the mammalian striatum. As basal ganglia functions in general are thought highly conserved among amniotes, we decided to use in situ autoradiographic methods to determine the occurrence and distribution of pharmacologically mammal-like 5-HT(2A) and 5-HT(2C) receptors in the lizard, Anolis carolinensis, with particular attention to the striatum. We also determined the distributions of 5-HT(1A), 5-HT(1B/D), 5 HT(3), and 5-HT(uptake) receptors for comparison. All 5-HT receptors examined showed pharmacological binding specificity, and forebrain binding density distributions that resembled those reported for mammals. Anolis 5 HT(2A/C) and 5-HT(1A) site distributions were similar in both in vivo and ex vivo binding experiments. 5-HT(2A & C) receptors occur in both high and low affinity states, the former having preferential affinity for (125)I-(+/-)-2,5-dimethoxy-4-iodo-amphetamine hydrochloride ((125)I-DOI). In mammals (125)I-DOI binding shows a patchy density distribution in the striatum, being more dense in striosomes than in surrounding matrix. There was no evidence of any such patchy density of (125)I-DOI binding in the anole striatum, however. As a further indication that anoles do not possess a striosome and matrix striatal organization, neither (3)H-naloxone binding nor histochemical staining for acetylcholinesterase activity (AChE) were patchy. AChE did show a band-like striatal distribution, however, similar to that seen in birds. 相似文献
34.
35.
36.
Zhigang Liu Xiumei Zhao Hua Mao Patricia A. Baxter Yulun Huang Litian Yu Lalita Wadhwa Jack M. Su Adekunle Adesina Lazlo Perlaky Mary Hurwitz Neeraja Idamakanti Seshidhar Reddy Police Paul L. Hallenbeck Richard L. Hurwitz Ching C. Lau Murali Chintagumpala Susan M. Blaney Xiao-Nan Li 《Neuro-oncology》2013,15(9):1173-1185
Background
Seneca Valley virus (SVV-001) is a nonpathogenic oncolytic virus that can be systemically administered and can pass through the blood–brain barrier. We examined its therapeutic efficacy and the mechanism of tumor cell infection in pediatric malignant gliomas.Methods
In vitro antitumor activities were examined in primary cultures, preformed neurospheres, and self-renewing glioma cells derived from 6 patient tumor orthotopic xenograft mouse models (1 anaplastic astrocytoma and 5 GBM). In vivo therapeutic efficacy was examined by systemic treatment of preformed xenografts in 3 permissive and 2 resistant models. The functional role of sialic acid in mediating SVV-001 infection was investigated using neuraminidase and lectins that cleave or competitively bind to linkage-specific sialic acids.Results
SVV-001 at a multiplicity of infection of 0.5 to 25 replicated in and effectively killed primary cultures, preformed neurospheres, and self-renewing stemlike single glioma cells derived from 4 of the 6 glioma models in vitro. A single i.v. injection of SVV-001 (5 × 1012 viral particles/kg) led to the infection of orthotopic xenografts without harming normal mouse brain cells, resulting in significantly prolonged survival in all 3 permissive and 1 resistant mouse models (P < .05). Treatment with neuraminidase and competitive binding using lectins specific for α2,3-linked and/or α2,6-linked sialic acid significantly suppressed SVV-001 infectivity (P < .01).Conclusion
SVV-001 possesses strong antitumor activity against pediatric malignant gliomas and utilizes α2,3-linked and α2,6-linked sialic acids as mediators of tumor cell infection. Our findings support the consideration of SVV-001 for clinical trials in children with malignant glioma. 相似文献37.
Mateus J Pereira L Baxter J Berghella V Tolosa J 《American journal of perinatology》2007,24(6):381-385
The purpose of this study is to determine the effectiveness of fetal fibronectin (FFN) compared to assessment of cervical dilation (CD) in clinical management of women with symptomatic preterm labor (PTL). Pregnant women presenting to Thomas Jefferson University Hospital between May 1, 2001 and November 30, 2002 with symptomatic PTL underwent FFN sampling and had a complete clinical evaluation including a pelvic bimanual examination. Inclusion criteria were singleton pregnancy, gestational age (GA) between 24 (0) and 33 (6) weeks, CD < 3 cm, and intact amniotic membranes. FFN samples were sent out and results were available within 4-12 hours. Clinical management including tocolysis, antenatal steroids, and hospitalization was determined based on digital CD assessment and FFN status. A dilated cervix was defined as CD > 1 cm. Ninety-three patients were included. Spontaneous preterm delivery (SPTD) at < 37 weeks occurred in 20 of 93 (21.5%) patients. Medical therapy use was significantly higher in patients with dilated cervix than in those with a closed cervix (all P values < 0.05). Tocolysis and steroid use in FFN-negative patients and FFN-positive patients were not significantly different. Furthermore, tocolytic use was higher in FFN-negative patients than in women with positive FFN (50% versus 42.1%; P = 0.53). Use of antenatal steroids was similar in patients with CD >/= 1 cm and a positive FFN (54.5% versus 47.4%; P = 0.92). Compared with FFN-negative patients, women with closed cervix were less likely to undergo interventions. In symptomatic PTL patients, CD determined clinical management more than FFN status. Overall, the use of FFN was not effective in decreasing "unnecessary" clinical interventions. 相似文献
38.
We were unable, passively, to transfer reactivity against dextran to the skin or peritoneal mast cells of non-dextran-reactive rats, by using serum or material eluted at pH 3 from mast cells of spontaneously dextran-reactive rats. When the dextran-reactive donor rats had also been immunized against egg albumin (EA) with pertussis vaccine (inducing IgE anti-EA antibody), passive sensitivity against EA (but not against dextran) could easily be transferred. The results indicated that the anti-dextran reactivity is not due to IgE antibody. Systemic reactions against dextran and EA differed in pattern, supporting the concept that the two substances acted through different mechanisms. 相似文献
39.
Trends in dietary fiber intake in Japan over the last century 总被引:5,自引:0,他引:5
Nakaji S Sugawara K Saito D Yoshioka Y MacAuley D Bradley T Kernohan G Baxter D 《European journal of nutrition》2002,41(5):222-227
Summary. Background: Insufficient intake of dietary fiber (DF) is currently a major problem in the overall promotion of health in the general
population in Japan. Aim of the study: To analyze the time trends in DF intake, including DF density (total DF intake/1,000 kcal), and the ratio of water-insoluble
fiber to water-soluble fiber (IS ratio) in Japan. Methods: The time trend in DF intake in Japan was calculated from data compiled in the Japanese National Nutrition Survey. Results: The mean daily DF intake (total DF intake) in 1952 was 20.5 g/day, which rapidly declined to about 70 % of the 1952 level
in 1970, after which there was little change to 1998. DF density in 1952 was 9.7 g/1000 kcal, which declined by about 30 %
in 1970, and remained at about the same level to 1998. The IS ratio has remained stable over this period. Whereas total DF
intake and DF density in Japan are similar to those in Western countries, the IS ratios are higher in Japan. Therefore, the
higher incidence of, and mortality from, colon diverticulosis, coronary heart disease, hyperlipidemia, etc., which are all
thought to be related to fiber deficiency, in Western countries compared to Japan might be due to the differences in the IS
ratio. Conclusions: A decline in total DF intake and DF density is predicted for Japan in the future, because these parameters were lower among
the younger generation. This may be due to the marked changes in the dietary habits of the younger generation, and is a problematic
trend for Japanese health.
Received: 26 April 2002, Accepted: 22 August 2002
Correspondence to: Shigeyuki Nakaji, MD, PhD 相似文献
40.