全文获取类型
收费全文 | 131888篇 |
免费 | 12069篇 |
国内免费 | 4136篇 |
专业分类
耳鼻咽喉 | 905篇 |
儿科学 | 3089篇 |
妇产科学 | 3773篇 |
基础医学 | 12325篇 |
口腔科学 | 3030篇 |
临床医学 | 13158篇 |
内科学 | 18914篇 |
皮肤病学 | 1930篇 |
神经病学 | 8890篇 |
特种医学 | 2778篇 |
外国民族医学 | 15篇 |
外科学 | 10939篇 |
综合类 | 20232篇 |
现状与发展 | 11篇 |
一般理论 | 7篇 |
预防医学 | 16793篇 |
眼科学 | 2989篇 |
药学 | 13136篇 |
137篇 | |
中国医学 | 7560篇 |
肿瘤学 | 7482篇 |
出版年
2024年 | 520篇 |
2023年 | 2485篇 |
2022年 | 4670篇 |
2021年 | 6304篇 |
2020年 | 5988篇 |
2019年 | 5027篇 |
2018年 | 4832篇 |
2017年 | 4944篇 |
2016年 | 5178篇 |
2015年 | 4761篇 |
2014年 | 8728篇 |
2013年 | 10457篇 |
2012年 | 8163篇 |
2011年 | 8633篇 |
2010年 | 6831篇 |
2009年 | 6159篇 |
2008年 | 5956篇 |
2007年 | 5907篇 |
2006年 | 5229篇 |
2005年 | 4624篇 |
2004年 | 3820篇 |
2003年 | 3533篇 |
2002年 | 2852篇 |
2001年 | 2595篇 |
2000年 | 2126篇 |
1999年 | 1812篇 |
1998年 | 1628篇 |
1997年 | 1521篇 |
1996年 | 1321篇 |
1995年 | 1241篇 |
1994年 | 1089篇 |
1993年 | 876篇 |
1992年 | 839篇 |
1991年 | 783篇 |
1990年 | 717篇 |
1989年 | 619篇 |
1988年 | 478篇 |
1987年 | 402篇 |
1986年 | 454篇 |
1985年 | 583篇 |
1984年 | 539篇 |
1983年 | 336篇 |
1982年 | 428篇 |
1981年 | 339篇 |
1980年 | 343篇 |
1979年 | 261篇 |
1978年 | 204篇 |
1977年 | 187篇 |
1976年 | 189篇 |
1975年 | 129篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Marc G Weisskopf Honglei Chen Michael A Schwarzschild Ichiro Kawachi Alberto Ascherio 《Movement disorders》2003,18(6):646-651
Anxiety disorders are common in Parkinson's disease (PD). However, the risk of PD among people with anxiety has not been examined in a prospective cohort study. We examined this relation prospectively within the Health Professionals Follow-Up Study, a cohort of US male health professionals. In 1988, anxiety was assessed using the Crown-Crisp phobic anxiety index in 35,815 men without PD, stroke, or cancer at baseline. There were 189 incident cases of PD during 12 years of follow-up. After adjusting for age, smoking, and caffeine intake, the relative risk of PD among men with the highest level of anxiety (Crown-Crisp index scores of 4 and above) was 1.5 (95% CI = 1.0-2.1; P-trend = 0.01) compared to men with the lowest level of anxiety. This positive association persisted after excluding cases of PD with onset in the first 2 years of follow-up. Use of anxiolytic medication was also associated with an elevated risk of PD (RR= 1.6; 95% CI = 0.9-3.1), but adjusting for this potential confounder did not materially affect the association between anxiety and risk of PD. Our results suggest that anxiety is a risk factor for PD. Whether this association is causal or the result of shared underlying biology remains a question. 相似文献
82.
S. Kølvraa J. Koch N. Gregersen P. K. A. Jensen A. L. Jørgensen K. B. Petersen K. Rasmussen L. Bolund 《Clinical genetics》1991,39(4):278-286
Two cloned DNA fragments, one derived from an alpha satellite subfamily common to chromosomes 13 and 21, and the other derived from a similar subfamily common to chromosomes 14 and 22, have been used as biotinylated probes in in situ hybridization studies. Under high stringency conditions, chromosome specific centromeric labelling can be obtained. The applications of this technique in clinical situations are illustrated on metaphases from a fetus with trisomy 21, a fetus with trisomy 13, and a child with clinical features of cat-eye syndrome. 相似文献
83.
Normal morphology of sacroiliac joints in children: magnetic resonance studies related to age and sex 总被引:2,自引:0,他引:2
M. Bollow J. Braun J. Kannenberg T. Biedermann C. Schauer-Petrowskaja S. Paris S. Mutze B. Hamm 《Skeletal radiology》1997,26(12):697-704
Objective. To determine in a prospective study the normal MRI morphology of the sacroiliac joints (SIJs) in relation to age and sex
during adolescence. Design and patients. A total of 98 children (63 boys, mean age 12.7±2.8 years; 35 girls, mean age 13.7±2.3 years), ranging in age from 8 to 17
years, with juvenile chronic arthritis (JCA) but without signs of sacroiliitis fulfilled the study prerequisites (no back
pain and no pathologic changes of the SIJs on physical examination before MRI in a 1.5-year follow-up). An additional eight
HLA-B27-negative boys and eight HLA-B27-negative girls without arthritis served as controls. The MRI protocol comprised a
T1-weighted SE sequence, an opposed-phase T2*-weighted GE sequence, and a dynamic contrast-enhanced study in single-section
technique. Results. Noncontrast MRI permitted differentiation of “open” from ossified segmental and lateral apophyses of the sacral wings, with
a significant difference in age (P <0.05) between children with open and ossified apophyses. Ossification of the apophyses of the sacral wings was seen significantly
earlier (P <0.05) in girls than in boys. Girls also had a significantly higher incidence of transitional lumbosacral vertebrae, pelvic
asymmetries, and accessory joints. In the contrast-enhanced opposed-phase MRI study, normal cartilage of the SIJs showed no
contrast enhancement whereas the joint capsule showed a moderate enhancement. Conclusion. There are significant age- and sex-related differences in the normal MRI morphology of juvenile SIJs. Our findings might
serve as a standard of comparison for the evaluation of pathologic changes – in particular for the early identification of
juvenile sacroiliitis. 相似文献
84.
OBJECTIVE: This study proposes a method for self-report health questionnaires to adjust test-retest reliability for changes during the test-retest interval based on an external measure, and to distinguish such changes from random response errors. METHODS: In our application, eighty participants completed the Symptoms of Illness Checklist (SIC) on two occasions, two weeks apart, immediately before interviews given on each occasion by one of two physicians in a crossover design. The physician interview scores served as external measures, and structural equation modeling was used to estimate the parameters of a model that corrected for the occasion-specific effect of participants' responses using information from the interviews. RESULTS: Correcting for changes in symptoms during the test-retest interval increased SIC test-retest reliability from .744 to .804 and significantly improved model fit (chi2(diff)(1) = 30.78, p < .001). CONCLUSIONS: The results suggest methods that can improve the evaluation of self-report health questionnaire test-retest reliability by identifying changes using an external measure, and distinguishing these from random response errors; these increased the estimated SIC test-retest reliability and indicated that the SIC was indeed able to measure changes over the studied time interval. This method can be applied across a broad range of questionnaires. 相似文献
85.
86.
J. M. Varela C. Regordán F. J. Medrano N. Respaldiza C. de la Horra M. A. Montes-Cano E. J. Calderón 《Clinical microbiology and infection》2004,10(8):770-772
The modes of infection and transmission of Pneumocystis jiroveci remain unclear. This study explored the relationship between the incidence of infection and climatic factors. In total, 536 cases of P. jiroveci infection were identified in the period 1994-1998, with an inverse correlation between the incidence of Pneumocystis pneumonia and the minimum mean ambient temperature (Spearman correlation coefficient: r - 0.30; p 0.02; ARIMA model: r - 0.250, p 0.07). The highest number of cases occurred in winter (anova test, p < 0.05), and there was a clear season-related incidence of P. jiroveci infection. 相似文献
87.
AIMS: To investigate whether availability of glucometer reagents increases the frequency of self-blood glucose monitoring (SBGM) and improves glycaemic control in diabetic patients. METHODS: Sixty-two insulin-treated diabetic patients were randomized to two groups, matched for age, gender, education, income, type and duration of diabetes, years of insulin treatment, number of daily insulin injections, and haemoglobin (Hb)A1c. All patients were given a glucometer, but one group (no cost, NC) was provided glucometer test strips free of charge. The other group (control, C) had to purchase strips as they found it necessary. Both groups of patients were followed longitudinally at 2-monthly intervals for 12 months with measurement of blood glucose and HbA1c, and the frequency of SBGM was determined by downloading the glucometer memory. RESULTS: The SBGM frequency was significantly higher in the NC group vs. the C group during the first 4 months (2.0 +/- 0.2 tests/day vs. 1.4 +/- 0.1 tests/day, P<0.025). Mean HbA1c remained stable over the 12 months in the NC group, whereas an increase with time was observed in the C group. The difference in HbA1c between the two groups was significant (P<0.002) after 6 months. Random blood glucose measured at each visit and average glucose recorded by the glucometer were also lower in the NC group vs. the C group (P<0.005). There was a negative correlation between HbA1c and SBGM frequency, and HbA1c in patients testing at least twice a day was lower than in those testing less than twice a day (8.8 +/- 0.2% vs. 9.6 +/- 0.2%, P<0.001). CONCLUSIONS: In this prospective study, having easy access to glucometer strips provided free of charge to patients increased SBGM frequency. The relationship between HbA1c and SBGM frequency supports the view that SBGM is an essential tool in diabetes management. 相似文献
88.
N. R. Saunders A. Deal G. W. Knott Z. M. Varga† J. G. Nicholls † 《Clinical and experimental pharmacology & physiology》1995,22(8):518-526
1. Repair and recovery following spinal cord injury (complete spinal cord crush) has been studied in vitro in neonatal opossum (Monodelphis domestica), fetal rat and in vivo in neonatal opossum. 2. Crush injury of the cultured spinal cord of isolated entire central nervous system (CNS) of neonatal opossum (P4–10) or fetal rats (E15–E16) was followed by profuse growth of fibres and recovery of conduction of impulses through the crush. Previous studies of injured immature mammalian spinal cord have described fibre growth occurring only around the lesion, unless implanted with fetal CNS. 3. The period during which successful growth occurred in response to a crush is developmentally regulated. No such growth was obtained after P12 in spinal cords crushed in vitro at the level of C7–8. 4. In vivo, in the neonatal (P4–8) marsupial opossum, growth of fibres through, and restoration of, impulse conduction across the crush was apparent 1–2 weeks after injury. With longer periods of time after crushing a considerable degree of normal locomotor function developed. 5. By the time the operated animals reached adulthood, the morphological structure of the spinal cord, both in the region of the crush and on either side of the site of the lesion, appeared grossly normal. 6. The results are discussed in relation to the eventual longterm possibility of devising effective treatments for patients with spinal cord injuries. 相似文献
89.
Risk factors for predicting recurrences of febrile seizures were studied in an unselected series of 169 children after their first febrile seizure. Follow-up data covering 2.1–6.8 (mean 3.8) years from the first febrile seizure were available from 167 of them (98.8%) including 72 girls. Altogether 35/167 (21.0%, 95% confidence intervals (CI) 14.6% to 29.1%) had further febrile seizures, and multivariate logistic regression analysis showed the number of febrile episodes (p = 0.011) and the occurrence of such seizures among first degree relatives (p = 0.015, relative risk 3.75, CI 1.22 to 11.5) to be significant risk factors for recurrences. Our findings indicate that more emphasis should be placed on preventing febrile episodes rather than concentrating only on preventing seizures with antiepileptic therapy. 相似文献
90.
Mayumi Matsuta Yuko Imamura Morimasa Matsuta Saiichi Kon Kohsuke Sasaki 《The Journal of dermatology》1994,21(1):14-19
We have applied DNA flow cytometric analysis to paraffin-embedded tissue sections of primary malignant melanomas. Conventionally, flow cytometric analysis of paraffin-embedded tissue sections has been done by the method of Hedley et al. We added ultrasound treatment to the method of Hedley et al. and a lower value of coefficient of variation was shown. Furthermore, a new technique, fluorescence in situ hybridization with a chromosome-specific repetitive DNA probe, was used for the analysis of chromosomal numerical aberrations in the same paraffin-embedded tissue sections. The DNA flow cytometric analysis showed that in 8 cases six primary malignant melanomas were of the aneuploid pattern and two cases of lentigo maligna (melamona in situ) were of the diploid pattern. By fluorescence in situ hybridization, the two cases with the diploid pattern had spots/nucleus of 1.28 and 1.12, and those with the aneuploid pattern had spots/nucleus from 2.01 to 2.27. Only one nodular melanoma in an aneuploid case showed spots/nucleus of 1.71. These data indicate that fluorescence in situ hybridization with chromosome-specific repetitive DNA probes can serve as a cytogenetic tool for the analysis of interphase nuclei of solid human tumors and may be useful for the study of tumor cell heterogeneity. 相似文献