首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   70195篇
  免费   5002篇
  国内免费   1544篇
耳鼻咽喉   447篇
儿科学   1416篇
妇产科学   1664篇
基础医学   7441篇
口腔科学   1534篇
临床医学   8739篇
内科学   11429篇
皮肤病学   425篇
神经病学   3774篇
特种医学   3596篇
外国民族医学   12篇
外科学   6136篇
综合类   10094篇
现状与发展   2篇
预防医学   7698篇
眼科学   795篇
药学   6514篇
  102篇
中国医学   2394篇
肿瘤学   2529篇
  2024年   97篇
  2023年   849篇
  2022年   1394篇
  2021年   2533篇
  2020年   2383篇
  2019年   2090篇
  2018年   2196篇
  2017年   2022篇
  2016年   2085篇
  2015年   2155篇
  2014年   4072篇
  2013年   4444篇
  2012年   3768篇
  2011年   4128篇
  2010年   3222篇
  2009年   3013篇
  2008年   3162篇
  2007年   3327篇
  2006年   2819篇
  2005年   2612篇
  2004年   2351篇
  2003年   2005篇
  2002年   1874篇
  2001年   1746篇
  2000年   1470篇
  1999年   1363篇
  1998年   1253篇
  1997年   1247篇
  1996年   1165篇
  1995年   1084篇
  1994年   1021篇
  1993年   783篇
  1992年   778篇
  1991年   688篇
  1990年   596篇
  1989年   546篇
  1988年   480篇
  1987年   401篇
  1986年   363篇
  1985年   502篇
  1984年   385篇
  1983年   249篇
  1982年   354篇
  1981年   274篇
  1980年   256篇
  1979年   205篇
  1978年   170篇
  1977年   155篇
  1976年   148篇
  1975年   114篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
41.
Stress related to parenting a child with autism spectrum disorder can differently affect caregiver's physiological reactivity to acute stress. Here, parental stress levels, psychological characteristics, and coping strategies were assessed alongside measures of heart rate, heart rate variability, and cortisol during a psychosocial stress test in mothers of children with ASD (M‐ASD, n = 15) and mothers of typically developing children (n = 15). M‐ASD reported significantly higher levels of parental stress, anxiety, negative affectivity, social inhibition, and a larger preference for avoidance strategies. M‐ASD showed larger heart rate and cortisol responses to the psychosocial stress test. A positive relationship was found between parental stress levels and the magnitude of the cortisol stress response in both groups. The present findings indicate exaggerated physiological reactivity to acute psychosocial stress in M‐ASD and prompt further research to explore the role of individual differences in mediating the effects of parental stress on physiological stress responses.  相似文献   
42.
43.
44.
45.

Background

Partial nephrectomy (PN) is generally favored for cT1 tumors over radical nephrectomy (RN) when technically feasible. However, it can be unclear whether the additional risks of PN are worth the magnitude of renal function benefit.

Objective

To develop preoperative tools to predict long-term estimated glomerular filtration rate (eGFR) beyond 30 d following PN and RN, separately.

Design, setting, and participants

In this retrospective cohort study, patients who underwent RN or PN for a single nonmetastatic renal tumor between 1997 and 2014 at our institution were identified. Exclusion criteria were venous tumor thrombus and preoperative eGFR <15 ml/min/1.73 m2.

Intervention

RN and PN.

Outcome measurements and statistical analysis

Hierarchical generalized linear mixed-effect models with backward selection of candidate preoperative features were used to predict long-term eGFR following RN and PN, separately. Predictive ability was summarized using marginal RGLMM2, which ranges from 0 to 1, with higher values indicating increased predictive ability.

Results and limitations

The analysis included 1152 patients (13 206 eGFR observations) who underwent RN and 1920 patients (18 652 eGFR observations) who underwent PN, with mean preoperative eGFRs of 66 ml/min/1.73 m2 (standard deviation [SD] = 18) and 72 ml/min/1.73 m2 (SD = 20), respectively. The model to predict eGFR after RN included age, diabetes, preoperative eGFR, preoperative proteinuria, tumor size, time from surgery, and an interaction between time from surgery and age (marginal RGLMM2=0.41). The model to predict eGFR after PN included age, presence of a solitary kidney, diabetes, hypertension, preoperative eGFR, preoperative proteinuria, surgical approach, time from surgery, and interaction terms between time from surgery and age, diabetes, preoperative eGFR, and preoperative proteinuria (marginal RGLMM2). Limitations include the lack of data on renal tumor complexity and the single-center design; generalizability needs to be confirmed in external cohorts.

Conclusions

We developed preoperative tools to predict renal function outcomes following RN and PN. Pending validation, these tools should be helpful for patient counseling and clinical decision-making.

Patient summary

We developed models to predict kidney function outcomes after partial and radical nephrectomy based on preoperative features. This should help clinicians during patient counseling and decision-making in the management of kidney tumors.  相似文献   
46.

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   
47.
The purpose of this study was to elucidate the involvement of Mate1 in the tubular secretion of trimethoprim and saturation of Mate1-mediated efflux to address the mechanisms underlying the pharmacokinetic drug interactions with trimethoprim. Trimethoprim is a more potent inhibitor of MATE2-K than MATE1 with Ki values (μM) of 0.030–0.28 and 2.4–5.9, respectively. Trimethoprim is a substrate of human MATE1 and MATE2-K with Km values of 2.3 ± 0.9 and 0.018 ± 0.004 μM, and mouse Mate1, but not human OCT2, mouse Oct1 and Oct2. Pyrimethamine significantly reduced the renal clearance (CLR) of trimethoprim (mL/min/kg) from 40.0 ± 5.1 to 20.1 ± 3.7 (p < 0.05). Trimethoprim was given to mice at three infusion rates (150, 500, and 1500 nmol/min/kg). Together with an increase in the plasma concentrations of trimethoprim, the CLR (mL/min/kg) of trimethoprim decreased to 25.9 ± 3.2, 13.5 ± 5.7, and 8.92 ± 1.50 at the respective rates. Trimethoprim decreased the CLR of rhodamine 123 in an infusion rate-dependent manner: 11.5 ± 1.3 (control), 5.17 ± 1.55, 1.31 ± 0.50, and 0.532 ± 0.180. These results suggest that Mate1 mediates the tubular secretion of trimethoprim, and at therapeutic doses, MATEs-mediated efflux can be saturated, and thereby, cause drug interactions with other MATE substrates.  相似文献   
48.
Accurately predicting the hepatic clearance of compounds using in vitro to in vivo extrapolation (IVIVE) is crucial within the pharmaceutical industry. However, several groups have recently highlighted the serious error in the process. Although empirical or regression-based scaling factors may be used to mitigate the common underprediction, they provide unsatisfying solutions because the reasoning behind the underlying error has yet to be determined. One previously noted trend was intrinsic clearance-dependent underprediction, highlighting the limitations of current in vitro systems. When applying these generated in vitro intrinsic clearance values during drug development and making first-in-human dose predictions for new chemical entities though, hepatic clearance is the parameter that must be estimated using a model of hepatic disposition, such as the well-stirred model. Here, we examine error across hepatic clearance ranges and find a similar hepatic clearance-dependent trend, with high clearance compounds not predicted to be so, demonstrating another gap in the field.  相似文献   
49.
目的了解上海市黄浦区社会办医疗美容机构的管理人员和医师对《医疗美容管理办法》相关内容的掌握情况,发现存在的问题并提出改善建议.方法采用现场调查与现场问卷调查相结合的方式,对在上海市黄浦区开展医疗美容科目的所有社会办医疗机构(共计38家)进行全覆盖现场调查,并对其中的管理人员41人、相关医师31人进行问卷调查.结果38家社会办医疗美容机构中,美容外科和美容皮肤科的开展率较高,分别为96.8%和97.2%,而美容牙科开展率为52.4%,美容中医科开展率最低(25.0%).管理人员关于非主诊医师可在主诊医师指导下工作的知晓率仅68.3%.关于美容外科、皮肤科、中医科、牙科主诊医师应具备的工作年限,管理人员答对率为90.2%,医师答对率为72.0%,二者有显著性差异(P<0.05).结论社会办医疗美容机构中的二级科目设置需进一步优化,以减少资源空置.应加强对医疗机构管理人员和医师的法律培训,改变经营模式,制定明确的准入与退出机制,从而减少违法违规行为的发生.  相似文献   
50.
《中国现代医生》2020,58(34):60-63
目的 通过检测老年轻度认知障碍(MCI)患者血清瘦素(LEP)、甲状腺激素水平,分析其与局部脑血流量(rCBF)的关系。方法 选择本院收治的128 例老年MCI 患者,另选健康者128 例作为对照组。检测血清LEP、甲状腺激素、大脑各区域rCBF 水平并分析其相关性。结果 老年MCI 组患者左右侧额叶、右侧颞叶、左侧顶叶、左右侧基底节区域脑血流量[(43.81±8.62)mL/(100 g·min)、(43.24±7.93)mL/(100 g·min)、(45.14±6.98)mL/(100 g·min)、(45.86±6.77)mL/(100 g·min)、(67.95±8.52)mL/(100 g·min)、(68.36±8.34)mL/(100 g·min)]低于对照组[(46.39±8.31)mL/(100 g·min)、(46.52±8.56)mL/(100 g·min)、(47.37±7.04)mL/(100 g·min)、(48.25±6.98)mL/(100 g·min)、(70.34±8.96)mL/(100 g·min)、(70.58±8.57)mL/(100 g·min)](P<0.05)。老年MCI 组患者血清LEP、T3、FT3 水平[(4.87±1.56)μg/L、(1.21±0.16)nmol/L、(3.04±0.36)pmol/L]低于对照组[(11.45±3.92)μg/L、(1.68±0.21)nmol/L、(4.82±1.21)pmol/L](P<0.05),TSH 水平为(2.78±0.75)IU/mL,高于对照组的(1.13±0.38)IU/mL(P<0.05)。老年MCI 患者血清LEP 水平与左侧额叶、右侧颞叶、左侧顶叶rCBF 呈正相关(r=0.452、0.537、0.544,P 均<0.05),T3 水平与左侧额叶、右侧颞叶rCBF 呈正相关(r=0.427、0.521,P 均<0.05),FT3 水平与右侧颞叶rCBF 呈正相关(r=0.492,P<0.05),TSH 水平与左侧额叶、右侧颞叶rCBF 呈负相关(r=-0.463、-0.489,P 均<0.05)。结论 老年MCI 患者血清中LEP、T3、FT3 水平降低,TSH 水平升高,且与不同区域rCBF 有相关性,可通过调控脑血管功能影响rCBF 变化水平。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号