收费全文 | 116844篇 |
免费 | 8199篇 |
国内免费 | 4001篇 |
耳鼻咽喉 | 592篇 |
儿科学 | 2096篇 |
妇产科学 | 2048篇 |
基础医学 | 11272篇 |
口腔科学 | 2243篇 |
临床医学 | 9341篇 |
内科学 | 15075篇 |
皮肤病学 | 2073篇 |
神经病学 | 8461篇 |
特种医学 | 2963篇 |
外国民族医学 | 15篇 |
外科学 | 7730篇 |
综合类 | 16379篇 |
现状与发展 | 4篇 |
预防医学 | 11760篇 |
眼科学 | 925篇 |
药学 | 23166篇 |
118篇 | |
中国医学 | 8582篇 |
肿瘤学 | 4201篇 |
2024年 | 248篇 |
2023年 | 1555篇 |
2022年 | 2344篇 |
2021年 | 4019篇 |
2020年 | 3795篇 |
2019年 | 3251篇 |
2018年 | 3238篇 |
2017年 | 3490篇 |
2016年 | 3745篇 |
2015年 | 3790篇 |
2014年 | 7129篇 |
2013年 | 8199篇 |
2012年 | 6877篇 |
2011年 | 7503篇 |
2010年 | 5667篇 |
2009年 | 5359篇 |
2008年 | 5464篇 |
2007年 | 5660篇 |
2006年 | 4845篇 |
2005年 | 4350篇 |
2004年 | 3778篇 |
2003年 | 3217篇 |
2002年 | 2750篇 |
2001年 | 2405篇 |
2000年 | 2102篇 |
1999年 | 1897篇 |
1998年 | 1736篇 |
1997年 | 1681篇 |
1996年 | 1608篇 |
1995年 | 1477篇 |
1994年 | 1375篇 |
1993年 | 1122篇 |
1992年 | 1127篇 |
1991年 | 1071篇 |
1990年 | 971篇 |
1989年 | 949篇 |
1988年 | 854篇 |
1987年 | 740篇 |
1986年 | 754篇 |
1985年 | 1051篇 |
1984年 | 980篇 |
1983年 | 691篇 |
1982年 | 741篇 |
1981年 | 673篇 |
1980年 | 620篇 |
1979年 | 458篇 |
1978年 | 352篇 |
1977年 | 294篇 |
1976年 | 260篇 |
1975年 | 220篇 |
Background Context
The concept of dynamic stabilization (DS) of the lumbar spine for treatment of degenerative instability has been introduced almost two decades ago. Dynamic stabilization follows the principle of controlling movement in the coronal plane by providing load transfer of the spinal segment without fusion and, at the same time, reducing side effects such as adjacent segment disease (ASD). So far, only little is known about revision rates after DS due to ASD and screw loosening (SL).Purpose
The present study aimed to evaluate the longitudinal revision rates following dynamic pedicle screw stabilization in the lumbar spine and to determine specific risk factors predictive for ASD, SL, and overall reoperation in a large cohort with considerable follow-up.Design
We carried out a post hoc analysis of a prospectively collected database in a level I spine center.Patients Example
The patient sample comprised 283 (151 female/132 male) consecutive patients suffering from painful degenerative lumbar segmental instability with or without spinal stenosis who underwent DS of the lumbar spine (Ulrich Cosmic, Ulrich Medical, Ulm, Germany) between January 2008 and December 2011.Outcome Measures
Longitudinal reoperation rate and risk factors predictive for revision surgery were evaluated.Methods
We analyzed the longitudinal reoperation rate due to ASD and SL and overall reoperation. Risk factors such as age, gender, body mass index, lumbar lordosis (LL), number of segments, and number of previous surgeries were taken into account. Regular and mixed model logistic regressions were performed to determine risk factors for revision surgery on a patient and on a screw level.Results
The mean age was 65.7±10.2 years (range 31–88). One hundred thirty-two patients were stabilized in 1 segment, 134 in 2 segments, 15 in 3 segments, and 2 patients in 4 segments. Reoperation rate for ASD and SL after 1 year was 7.4 %, after 2 years was 15.0%, and after a mean follow-up of 51.4±15 months was 22.6%. Reasons for revision were SL in 19 cases (6.6%), ASD in 39 cases (13.7%), SL and ASD in 6 cases, hematoma in 2 cases (0.7%), cerebrospinal fluid fistulae in 3 cases (1.1%), infection in 6 cases (2.1%), and implant failure in 1 case (0.4%). The patients' age, the number of stabilized segments, and the number of previous surgeries and postoperative LL had a significant influence on the probability for revision surgery.Conclusions
Reoperation rates after DS of the lumbar spine are comparable with rigid fixations. The younger the patient and the more segments are involved, the lower the LL and the more previous surgeries were found, the higher was the risk of revision. Risk of revision was almost twice as high in men compared with women. We therefore conclude that for clear clinical indication and careful evaluation of preoperative imaging data, DS using the Cosmic system seems to be a possible option. The presented data will help to further tailor indication and patient selection. 相似文献2. The CGA is administered intravenously (IV) and intranasally (IN) at the dose of 10?mg/kg. Further, its concentration in the plasma, cerebrospinal fluid (CSF) and the whole brain is analyzed by HPLC-UV method.
3. The study observes that CGA is rapidly absorbed in plasma with tmax of 1?min similar to IV route after IN administration. The peak plasma concentration and AUC0–24 are higher by 3.5 and 4.0 times respectively in IV administration, compared to IN delivery that represents the significant less systemic exposure of CGA in IN route.
4. However, the concentration of CGA in the brain is 4, 6.5, 5.3, 5.2 and 4.5 times higher at 30, 60, 120, 240 and 360?min, respectively in IN administration compared to IV administration. The exposure of CGA in the brain after IN administration (AUCbrain, IN) was significantly greater (4 times) as compared to the exposure of CGA in the brain (AUCbrain, IV) after IV administration reflecting significant brain uptake of CGA through nasal route. Therefore, IN delivery of CGA can be a promising approach for the treatment of stroke and neurodegenerative disorders. 相似文献