全文获取类型
收费全文 | 13045篇 |
免费 | 559篇 |
国内免费 | 64篇 |
专业分类
耳鼻咽喉 | 75篇 |
儿科学 | 238篇 |
妇产科学 | 119篇 |
基础医学 | 1693篇 |
口腔科学 | 400篇 |
临床医学 | 731篇 |
内科学 | 3154篇 |
皮肤病学 | 290篇 |
神经病学 | 1097篇 |
特种医学 | 449篇 |
外科学 | 2581篇 |
综合类 | 31篇 |
一般理论 | 1篇 |
预防医学 | 330篇 |
眼科学 | 105篇 |
药学 | 869篇 |
中国医学 | 25篇 |
肿瘤学 | 1480篇 |
出版年
2023年 | 56篇 |
2022年 | 102篇 |
2021年 | 183篇 |
2020年 | 87篇 |
2019年 | 120篇 |
2018年 | 179篇 |
2017年 | 139篇 |
2016年 | 200篇 |
2015年 | 216篇 |
2014年 | 270篇 |
2013年 | 345篇 |
2012年 | 591篇 |
2011年 | 654篇 |
2010年 | 368篇 |
2009年 | 323篇 |
2008年 | 635篇 |
2007年 | 739篇 |
2006年 | 725篇 |
2005年 | 783篇 |
2004年 | 779篇 |
2003年 | 779篇 |
2002年 | 704篇 |
2001年 | 319篇 |
2000年 | 296篇 |
1999年 | 340篇 |
1998年 | 211篇 |
1997年 | 189篇 |
1996年 | 190篇 |
1995年 | 169篇 |
1994年 | 182篇 |
1993年 | 135篇 |
1992年 | 240篇 |
1991年 | 246篇 |
1990年 | 204篇 |
1989年 | 219篇 |
1988年 | 232篇 |
1987年 | 205篇 |
1986年 | 157篇 |
1985年 | 166篇 |
1984年 | 113篇 |
1983年 | 82篇 |
1982年 | 64篇 |
1981年 | 57篇 |
1980年 | 62篇 |
1979年 | 62篇 |
1978年 | 57篇 |
1977年 | 39篇 |
1976年 | 53篇 |
1975年 | 38篇 |
1969年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Iwasaki-Ishizuka Y Yamato H Murayama H Abe M Takahashi K Kurokawa K Fukagawa M Ezawa I 《Journal of nutritional science and vitaminology》2003,49(4):256-261
Vitamin K2 (menaquinone) acts on the bone metabolism. Menatetrenon (MK-4) is a vitamin K2 homologue that has been used as a therapeutic agent for osteoporosis in Japan. Rat models of immobilization induced by sciatic neurectomy are characterized by transiently increased bone resorption and sustained reduction in bone formation. Using such a rat model, we investigated the efficacy of MK-4 on bone loss. Male Sprague-Dawley rats were subjected to unilateral sciatic neurectomy and administered MK-4 for 28 d beginning day 21 after operation. The effect of MK-4 on the immobilized bone was assessed by measuring the bone mineral density of the femur, breaking force of the femoral diaphysis, and bone histomorphometry in tibial diaphysis. The BMD on both the femoral distal metaphysis and diaphysis was reduced by sciatic neurectomy. The administration of MK-4 ameliorated this reduction in a dose-dependent manner. The administration of 30 mg/kg MK-4 ameliorated the reduction in bone strength. An improvement in bone formation was observed following the administration of MK-4. These results suggest that MK-4 has a therapeutic potential for immobilization-induced osteopenia. 相似文献
992.
Shizuma K Endo S Hoshi M Takada J Ishikawa M Iwatani K Hasai H Oka T Fujita S Watanabe T Yamashita T Imanaka T 《Journal of radiation research》2003,44(2):133-139
Residual 152Eu activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 m in the slant range and one control sample at 2,850 m from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of 152Eu are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of 60Co and 36Cl. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for 152Eu are also discussed. 相似文献
993.
Ozaki A Ogihara R Uchiyama M Ohta T Maeda K Shibata H Koitaya N Yamami N Mano Y Ohida T Sone K 《[Nihon kōshū eisei zasshi] Japanese journal of public health》2003,50(8):697-712
PURPOSE: To investigate quality of life (QOL) and associated factors in centenarians, we conducted a visitation interview survey for all male and one half of the female centenarians living in Japan, and studied QOL, lifestyle and health status. METHODS: All the male centenarians and a randomly-sampled half of the female centenarians living in Japan were included in the study based on the National Census. Finally, 556 male and 1341 female centenarians participated in the present visitation interview survey and were studied using a structured questionnaire. QOL was assessed from 3 aspects; activities of daily life (ADL), cognitive function (CF) and mental health (MH). RESULTS: Individuals having superior ADL accounted for 30.9% of the male and 13.6% of the female centenarians, those with superior CF were 58.1% and 35.6%, respectively, and those with superior MH were 39.2% and 26.8%, providing evidence that superior QOL was more dominant in males than in females. There were no effects of residential areas (north, east, middle, west, southwest and south of Japan) on the prevalence of ADL, CF and MH. Multiple logistic regression analyses conducted independently, for ADL, CF and MH as dependent valuables revealed that habitual exercise, less decline in visual ability and preservation of masticating ability were associated with better results for these 3 aspects of male centenarians' QOL, and that habitual exercise, less decline in visual ability, spontaneous awakening in the morning, good appetite and having cohabitating family members were associated with superior QOL in the females, suggesting that more factors are operating in the latter. CONCLUSIONS: Several lifestyle factors were found to be associated with preservation of QOL in centenarians in Japan. These results should facilitate establishing a public health and welfare policy for the most senior citizens, a group that has been increasing in Japan. 相似文献
994.
Oka K 《[Nihon kōshū eisei zasshi] Japanese journal of public health》2003,50(3):208-215
The transtheoretical model of behavior change (TTM) has been used to account for how people change their health behavior. It was originally developed to explain or predict change in unhealthy addictive behavior (e.g., smoking), but recently the use of the TTM within the physical activity and exercise behavior domain has been proposed. In the present study, we examined its structure in this regard among middle-aged Japanese adults. In particular, the relationship between the stages of change for exercise behavior and self-efficacy was investigated. Firstly, a scale was developed to assess self-efficacy for exercise. Four hundred and sixty seven middle-aged adults completed questionnaires. As a result of stepwise variable selection procedure in exploratory factor analysis, a scale comprising 1 factor with 5 items was developed. Psychometric analyses revealed that this scale had high reliability and validity. Secondly, a cross-sectional investigation was conducted to examine the relationship between stage of change and self-efficacy among middle-aged adults (n = 808) using a questionnaire approach. Significant associations were found between stage of change for exercise behavior classification and self-efficacy for exercise. Specifically, scores on self-efficacy of the subjects in the present study were less for those in a precontemplation stage and greater for those in maintenance compared to all other stages, and generally followed a linear pattern of change across the stages. Although the use of a cross-sectional research design and nonrandom sampling methods in the present study limit interpretation, the similarity of these results to those in the previous literature suggests that the relationship between stages of change for exercise behavior and self-efficacy for exercise holds across different age groups and cultures. By accurately understanding these relationships, health promotion professionals may be able to improve physical activity and exercise promotion efforts. 相似文献
995.
Yamakawa K Nishitani K 《Yakushigaku zasshi. The Journal of Japanese history of pharmacy》2003,38(1):28-41
The separation of organic compounds has been carried out using the method of distillation and recrystallization since the 17th century.1st separation technology innovation (1950s to 1960s). After World War II, the science of separating organic compounds evolved to the use of paper or column chromatography. 2nd separation technology innovation (1960s to 1980s). In the 1960s, thin-layer chromatograpy (TLC) was developed. TLC is a convenient analytical technique for organic compounds. Separation methods for organic compounds using column chromatography and preparative TLC were carried out as practical applications. Gas chromatography (GC) was also introduced in the 1960s. GC is a useful analytical method for a mixture of various volatile organic compounds. Many GC instruments with new kinds of sensors were developed. Gas chromatography of nonbenzenoid organometallic compounds and metal complexes was successfully conducted by the author. 3rd separation technology innovation (1980s to 1990s). In the 1980s, high-performance liquid-chromatography (HPLC) was developed. HPLC analytical methods were useful for various kinds of organic compounds. In the 1990s, LC-MS and LC-NMR instruments were introduced for biomedical products. 4th separation technology innovation (1990s to present). Several new ionization methods for mass-spectrometry (electrospray, matrix-aided lazer desorption ionization, etc) are applied for proteins and biomedical products. Several new separation technologies (supercritical field chromatography, capillary electrophoresis, field-flow fractionization, etc.) are now being developed. 相似文献
996.
Liberal use of tricuspid valve detachment for transatrial ventricular septal defect closure 总被引:3,自引:0,他引:3
Aeba R Katogi T Hashizume K Koizumi K Iino Y Mori M Yozu R 《The Annals of thoracic surgery》2003,76(4):1073-1077
BACKGROUND: Although temporary tricuspid valve detachment is useful for improved visualization of ventricular septal defect through right atriotomy, liberal use of this adjunct is not widely supported, mainly because of concerns about iatrogenic complications such as heart blocks and tricuspid valve dysfunction. The objective of this study was to determine whether liberal use of this adjunct can improve operative outcome. METHODS: Between January 1997 and March 2002, trans-atrial closure of isolated ventricular septal defect (conoventricular or canal type) was performed in 87 consecutive patients. Tricuspid valve detachment was used in 4 out of 44 patients (prudent-use group) and 19 out of 43 patients (liberal-use group) in the first and second half of this period, respectively (p = 0.0002). Patient demographics and use of other surgical and cardiopulmonary bypass techniques remained virtually unchanged during this period. RESULTS: In the prudent-use group, there was one operative death with prolonged bypass time and one residual defect that required reoperation; neither of these patients underwent tricuspid valve detachment. All other patients (both groups) were free from mortality and clinically significant complications, including heart block, tricuspid regurgitation, and residual defect. The liberal-use group had shorter cardiopulmonary bypass time than the prudent-use group (59 +/- 14 vs 67 +/- 22 minutes, p = 0.037). CONCLUSIONS: Tricuspid valve detachment should be used liberally for moderate- or even low-difficulty exposure of ventricular septal defect, regardless of patient background, because it is a safe and effective adjunct that can improve speed, programmability, reproducibility, and reliability. 相似文献
997.
The purpose of this study was to evaluate the usefulness in a clinical setting of iodine-123-metaiodobenzylguanidine (123I-MIBG) scintigraphy, planar and single photon emission computed tomography (SPECT) images, in patients with neuroblastoma as detected by a mass screening survey. METHODS: 123I-MIBG planar whole body images, and regional SPECT images of patients with neuroblastoma in 51 studies were reviewed. They were all detected by a mass screening survey performed in the 6th month after birth using vanil mandelic acid (VMA), and homovanillic acid (HVA) and the neuroblastoma had been confirmed by surgery. Scintigraphy was performed 24 hours after injection of 111 MBq of 123I-MIBG. We assessed the accuracy of the planar whole body images in order to demonstrate the extent of the lesion and the correlation between the degree and extent of the lesions of 123I-MIBG accumulation and clinical staging with tumor markers, such as urinary VMA, urinary HVA, serum neuron specific enolase (NSE) and serum lactate dehydrogenase (LDH). Additionally, we evaluated SPECT how useful supplemental SPECT might be in a clinical setting as compared with planar whole body images. RESULTS: 123I-MIBG planar whole body images revealed all 33 (100%) primary lesions, 4 of the 5 cases (80%) with liver metastasis, 3 of the 13 (23%) with lymph nodes metastasis and 1 of 3 (33%) with bone marrow infiltration. The extent and degree of accumulation correlated with the values of urinary VMA, urinary HVA and serum NSE. SPECT images helped to understand the positional relation in all cases and provided useful additional information for clinical staging in 7 cases. CONCLUSION: 123I-MIBG scintigraphy with planar and SPECT images is useful for evaluating patients with neuroblastoma, following detection by a mass screening survey. 相似文献
998.
Three-dimensional stereotactic surface projection of brain perfusion SPECT improves diagnosis of Alzheimer’s disease 总被引:4,自引:0,他引:4
Honda N Machida K Matsumoto T Matsuda H Imabayashi E Hashimoto J Hosono M Inoue Y Koizum K Kosuda S Momose T Mori Y Oshima M 《Annals of nuclear medicine》2003,17(8):641-648
OBJECTIVES: Alzheimer's disease (AD) is diagnosed by either inspection of the brain perfusion SPECT, or three-dimensional stereotactic surface display (3D-SSP). The purpose was to compare diagnostic performances of these methods. METHODS: Sixteen nuclear medicine physicians independently interpreted 99mTc-ECD SPECT in one session and SPECT with 3D-SSP in another session without clinical information for 50 studies of AD patients and 40 studies of healthy volunteers. Probabilities of AD were reported according to a subjective scale from 0% (normal) to 100% (definite AD). Receiver operating characteristics curves were generated to calculate areas under the ROC curves (Az's) for the inspection as well as for an automated diagnosis based on a mean Z value in the bilateral posterior cingulate gyri in a 3D-SSP template. RESULTS: Mean Az for visual interpretation of SPECT alone (0.679 +/- 0.058) was significantly smaller than that for visual interpretation of both SPECT and 3D-SSP (0.778 +/- 0.060). Az for the automated diagnosis (0.883 +/- 0.037) was significantly greater than that for both modes of visual interpretation. CONCLUSIONS: 3D-SSP enhanced performance of the nuclear medicine physicians inspecting SPECT. Performance of the automated diagnosis exceeded that of the physicians inspecting SPECT with and without 3D-SSP. 相似文献
999.
1000.
Sequence polymorphisms of the hypervariable mitochondrial DNA (mtDNA) regions HVI and HVII, and coding region polymorphisms were investigated in 211 unrelated individuals from the Japanese population. Sequence comparison of the HVI and HVII regions led to the identification of 169 mitochondrial haplotypes defined by 147 variable positions. Among them 145 types were observed in only 1 individual; the other 24 types were shared by 2 or more individuals. The gene diversity was estimated at 0.9961, and the probability of two randomly selected individuals from the population having identical mtDNA types was 0.86%. We also established phylogenetic haplogroups in the Japanese population based on the coding and control region polymorphisms and compared the haplotypes with those in other Japanese, Korean and Chinese populations. As a result, three new subhaplogroups, G4a, G4b, and N9b, and several haplotypes specific for the Japanese and Korean populations were identified. The present database can be used not only for personal identification but also as an aid for geographic or phenotype (race) estimation in forensic casework in Japan.Electronic Supplementary Material Supplementary material is available for this article if you access the article at 相似文献