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   2165篇
  免费   148篇
  国内免费   9篇
耳鼻咽喉   28篇
儿科学   46篇
妇产科学   61篇
基础医学   266篇
口腔科学   119篇
临床医学   231篇
内科学   454篇
皮肤病学   41篇
神经病学   162篇
特种医学   63篇
外科学   269篇
综合类   8篇
一般理论   1篇
预防医学   209篇
眼科学   29篇
药学   166篇
中国医学   14篇
肿瘤学   155篇
  2024年   7篇
  2023年   29篇
  2022年   78篇
  2021年   122篇
  2020年   76篇
  2019年   93篇
  2018年   97篇
  2017年   70篇
  2016年   88篇
  2015年   91篇
  2014年   120篇
  2013年   139篇
  2012年   190篇
  2011年   189篇
  2010年   105篇
  2009年   77篇
  2008年   130篇
  2007年   123篇
  2006年   105篇
  2005年   107篇
  2004年   100篇
  2003年   71篇
  2002年   54篇
  2001年   4篇
  2000年   1篇
  1999年   8篇
  1998年   3篇
  1997年   2篇
  1996年   5篇
  1995年   6篇
  1992年   3篇
  1991年   4篇
  1988年   2篇
  1985年   3篇
  1984年   2篇
  1983年   3篇
  1982年   1篇
  1981年   2篇
  1980年   2篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
  1974年   2篇
  1973年   1篇
  1969年   2篇
  1962年   1篇
排序方式: 共有2322条查询结果,搜索用时 15 毫秒
41.
Piperazine designer drugs are a group of synthetic drugs of abuse that have appeared on the illicit market since the second half of the 1990s. The most common derivatives are 1-benzylpiperazine (BZP), 1-(4-methoxyphenyl)piperazine (MeOPP) and 1-(3,4-methylenedioxybenzyl)piperazine (MDBP). They can be consumed as capsules, tablets, but also in powder or liquid forms. Generally, although less potent than amphetamines, piperazines have dopaminergic and serotonergic activities. The aim of this work was to evaluate the toxic effects of BZP, MeOPP and MDBP using Caenorhabditis elegans as in vivo model for acute toxicity, development, reproduction and behavior testing. The LC50 for BZP, MeOPP and MDBP were 52.21, 5.72 and 1.22 mm , respectively. All concentrations induced a significant decrease in the body surface of the worms, indicating developmental alterations, and decrease in the brood size. Worms exposed to piperazine designer drugs also presented a decrease in locomotor activity and mechanical sensitivity, suggesting the possible dysfunction of the nervous system. Neuronal damage was confirmed through the decrease in fluorescence of BY200 strains, indicating loss of dopaminergic transporters. In conclusion, we suggest that piperazine designer drugs lead to neuronal damage, which might be the underlying cause of the altered behavior observed in humans.  相似文献   
42.
The aim of this study was to evaluate the morphological and biomechanical characteristics of a wound entrance on the parietal bone from the impact of projectiles presenting three different calibres. Three-dimensional finite element models of dry human skull and of three projectiles with calibres .380 Auto, .40 S&W and 9 × 19 mm Luger were obtained. These geometries were used to perform a simulation of projectile impact on the parietal bone by the finite element method. We calculated the morphological aspect of the wounds on the external bone surface, the equivalent von Mises stress and the kinetic energy loss. The wounds from the 9 × 19 mm and .380 calibres presented a circular aspect, while the wound from the .40 calibre presented an oval aspect. The 9 × 19 mm caused a major wound area compared with the other calibres. The maximum von Mises stress in the bone was higher from the .40 calibre penetration, and the .380 had the major kinetic energy loss. In conclusion, the 9 × 19 mm and .380 presented similarity in the shape of the entrance hole. The projectile with 9 × 19 mm calibre seems to have greater penetration power and the .40 S&W projectile greater power of destruction and dissipation of energy.  相似文献   
43.

Purpose

One-third of all pregnancies in the United States are conceived within 18 months of a prior live birth. Preventing unintended pregnancies may help to decrease the prevalence of pregnancies with these short interpregnancy intervals. However, data on factors associated with pregnancy intention among women who have had short birth intervals are sparse. Pregnancy Risk Assessment Monitoring System data were used to further evaluate these associations.

Methods

Because only Mississippi and Tennessee Pregnancy Risk Assessment Monitoring System include a survey question about birth interval length, this analysis was limited to women from those states who recently had a short birth interval (n = 384). Pregnancy intention and demographic, lifestyle, and reproductive data were obtained from surveys and birth certificates. Logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Nearly 76% of women with short birth intervals reported their pregnancy as unintended. Women who were non-Hispanic black or consumed alcohol during pregnancy had statistically significant increased odds of reporting the pregnancy with a short birth interval as being unintended (OR = 3.98; 95% CI: 1.73–9.16 and OR = 10.56; 95% CI: 1.80–61.83, respectively).

Conclusions

Although all women should be counseled on postpartum contraceptive use, findings suggest that important subpopulations of women may benefit from more targeted counseling during prenatal care visits and the immediate postpartum hospital stay regarding the importance of using contraception to not only better space pregnancies but also prevent unintended pregnancies.  相似文献   
44.
OBJECTIVE: Assess the effect of antioxidant treatment on late memory impairment and early hippocampus oxidative stress after cecal ligation and perforation. SUBJECTS: Male Wistar rats. INTERVENTIONS: Rats underwent sham operation or cecal ligation and perforation. Animals that underwent cecal ligation and perforation were divided into groups: 1) treated with basic support (50 mL/kg saline, 30 mg/kg ceftriaxone, and 25 mg/kg clindamycin every 6 hrs), 2) treated with basic support plus N-acetylcysteine (20 mg/kg N-acetylcysteine at 3, 6, 12, 18, and 24 hrs after cecal ligation and perforation), 3) treated with basic support plus deferoxamine (20 mg/kg deferoxamine at 3 and 24 hrs after cecal ligation and perforation), 4) treated with basic support plus N-acetylcysteine and deferoxamine, or 5) treated with N-acetylcysteine plus deferoxamine. MEASUREMENTS AND MAIN RESULTS: On days 10 and 30 after surgery, the animals underwent behavioral tasks: inhibitory avoidance task, habituation to an open field, and continuous multiple-trials step-down inhibitory avoidance task. The sepsis group showed significantly decreased performance in latency retention compared with the sham group in the inhibitory avoidance task. In the open-field task, the sepsis group presented memory impairment after sepsis. In the continuous multiple-trials step-down inhibitory avoidance task, the sepsis group showed a significant increase in the number of training trials required to reach the acquisition criterion. All these memory impairments were prevented by N-acetylcysteine plus deferoxamine treatment, but not its isolate use. In addition, the combined use of antioxidants attenuated oxidative damage in hippocampus 6 hrs after sepsis induction. CONCLUSIONS: Antioxidant treatment prevented the development of late cognitive deficits in an animal model of sepsis.  相似文献   
45.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie - Dexmedetomidine and ketamine may be administered intraoperatively as continuous infusions to provide opioid-sparing...  相似文献   
46.
47.

Background

Animal models are useful to evaluate the efficacy of antimicrobials in experimental sepsis.

Aim

To elucidate the steps of producing an experimental model for the treatment of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae sepsis

Methods

Several ESBL inoculums ranging from 1.5x109 colony-forming units per milliliter (CFU/mL) to 2.0x1010CFU/mL were administered by peritoneal injection in adults Wistar rats. Outcomes and microbiological data of quantitative peritoneal and blood cultures were observed in untreated animals. Animals which received 2.0x1010CFU/mL inoculums were treated with single meropenem dose (30mg/kg) after one hour and those which received 1.0x1010CFU/mL inoculums were treated immediately with three doses of meropenem 50 mg/kg. Outcomes were observed for 24 hours after inoculation.

Results

Solutions with 1.5 x109 and 6.0x109 CFU/mL were not lethal within 24 hours. Inoculums of 1.0x1010CFU/mL were lethal in 80% and solutions with 2.0x1010 CFU/mL were lethal in 100% of animals. ESBL lethal sepsis (1.0x1010CFU/mL) was treated immediately with 50 mg/kg of meropenem every eight hours for 24 hours and presented 40% mortality compared with 80% mortality of the control group (p=0.033). Quantitative cultures of peritoneal fluid presented 104CFU/mL or less for treated animals compared to more than 105 for untreated animals (p=0.001).

Conclusion

Inoculums of 1.0x1010CFU/mL achieved the best results to study a model of lethal sepsis and this model of treatment of carbapenem-susceptible Enterobacteriaceae can serve as control to further evaluation of treatment of carbapenemase-producing Enterobacteriaceae models.  相似文献   
48.

Purpose

The optimal treatment strategy for ductal carcinoma in situ (DCIS) continues to evolve and should consider the consequences of initial treatment on the likelihood, type, and treatment of recurrences.

Methods

We conducted a retrospective cohort study using two data sources of patients who experienced a recurrence (DCIS or invasive cancer) following breast-conserving surgery (BCS) for index DCIS: patients with an index DCIS diagnosed from 1997 to 2008 at the academic institutions of the National Comprehensive Cancer Network (NCCN; N = 88) and patients with an index DCIS diagnosed from 1990 to 2001 at community-based integrated healthcare delivery sites of the Health Maintenance Organization Cancer Research Network (CRN) (N = 182).

Results

Just under half of local recurrences in both cohorts were invasive cancer. While 40 % of patients in both cohorts underwent mastectomy alone at recurrence, treatment of the remaining patients varied. In the earlier CRN cohort, most other patients underwent repeat BCS (39 %) with only 18 % receiving mastectomy with reconstruction, whereas only 16 % had repeat BCS and 44 % had mastectomy with reconstruction in the NCCN cohort. Compared with patients not treated with radiation, those who received radiation for index DCIS were less likely to undergo repeat BCS (NCCN: 6.6 vs. 37 %, p = 0.001; CRN: 20 vs. 48 %, p = 0.0004) and more likely to experience surgical complications after treatment of recurrence (NCCN: 15 vs. 4 %, p = 0.17; CRN: 40 vs. 25 %, p = 0.09).

Conclusion

We found that treatment of recurrences after BCS and subsequent complications may be affected by the use of radiotherapy for the index DCIS. Initial treatment of DCIS may have long-term implications that should be considered.  相似文献   
49.
50.
Journal of Interventional Cardiac Electrophysiology - We hypothesized that data in manufacturers’ product performance reports (PPRs) can provide clinically valuable ICD and cardiac...  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