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   24695篇
  免费   1761篇
  国内免费   81篇
耳鼻咽喉   267篇
儿科学   562篇
妇产科学   496篇
基础医学   3411篇
口腔科学   745篇
临床医学   2843篇
内科学   4923篇
皮肤病学   208篇
神经病学   2653篇
特种医学   970篇
外国民族医学   2篇
外科学   2988篇
综合类   369篇
一般理论   24篇
预防医学   1966篇
眼科学   502篇
药学   2020篇
中国医学   23篇
肿瘤学   1565篇
  2023年   100篇
  2022年   153篇
  2021年   379篇
  2020年   251篇
  2019年   335篇
  2018年   381篇
  2017年   353篇
  2016年   407篇
  2015年   502篇
  2014年   706篇
  2013年   1049篇
  2012年   1607篇
  2011年   1735篇
  2010年   1022篇
  2009年   883篇
  2008年   1673篇
  2007年   1615篇
  2006年   1615篇
  2005年   1704篇
  2004年   1561篇
  2003年   1534篇
  2002年   1442篇
  2001年   302篇
  2000年   232篇
  1999年   318篇
  1998年   376篇
  1997年   287篇
  1996年   271篇
  1995年   255篇
  1994年   209篇
  1993年   182篇
  1992年   172篇
  1991年   155篇
  1990年   143篇
  1989年   145篇
  1988年   140篇
  1987年   131篇
  1986年   139篇
  1985年   144篇
  1984年   159篇
  1983年   157篇
  1982年   199篇
  1981年   164篇
  1980年   185篇
  1979年   98篇
  1978年   119篇
  1977年   110篇
  1976年   84篇
  1975年   89篇
  1974年   71篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Opiate activation of mu-opioid receptors (muORs) in the ventral tegmental area (VTA) modulates gamma-aminobutyric acid (GABA) neurotransmission within the mesocorticolimbic dopamine (DA) reward system. We combined in vivo extracellular electrophysiological recordings in anesthetized and freely behaving rats with intracellular Neurobiotin filling and immunocytochemistry to characterize the effects of opiates on VTA GABA neurons, evaluate their discharge activity during opiate self-administration, and identify the cellular sites for opiate activation. We identified a subpopulation of VTA GABA neurons that was characterized by location, spike discharge profile, activation by microelectrophoretic DA, and response to internal capsule (IC) stimulation. Systemic administration of heroin or microelectrophoretic application of the selective muOR agonist [d-Ala2, N-Me-Phe4, Gly-ol]-Enkephalin (DAMGO) reduced VTA GABA neuron firing rate (heroin IC(50) = 0.35 mg/kg) and was blocked by the muOR antagonist naloxone. Heroin also reduced IC-evoked post-stimulus spike discharges, a manifestation of gap-junction-mediated electrical coupling between VTA GABA neurons. The baseline firing rate of VTA GABA neurons significantly increased (239%) following the acquisition of heroin self-administration behavior and transiently increased during each response for heroin (105%), but decreased (49%) following heroin, similar to non-contingent heroin. Electrophysiologically characterized VTA GABA neurons were filled with Neurobiotin and labeled dendrites contained plasmalemmal muOR immunoreactivity. Dually labeled muOR dendrites contained dendrodendritic appositions characteristic of gap junctions. These findings indicate that inhibition of this population of GABAergic neurons by opiates acting on dendritic muORs has implications for modulation of electrical coupling between VTA GABA neurons and dopamine (DA) neurotransmission in the VTA and terminal field regions.  相似文献   
992.
Plasma serotonin in autism   总被引:1,自引:0,他引:1  
Serotonin is necessary for normal fetal brain development. Administration of serotonin inhibitors to pregnant rats results in offspring with abnormal behaviors, brain morphology, and serotonin receptor numbers. Low maternal plasma serotonin may contribute to abnormal brain development in autism. In this study, plasma serotonin levels in autism mothers and control mothers of typically developing children were compared, and plasma serotonin levels in children with autism (n = 17) and their family members were measured. Plasma serotonin levels in autism mothers were significantly lower than in mothers of normal children (P = 0.002). Plasma serotonin levels correlated between autism mothers and their children, but differed between autistic children and their fathers (P = 0.028) and siblings (P = 0.063). Low maternal plasma serotonin may be a risk factor for autism through effects on fetal brain development.  相似文献   
993.
The specific impedance of cardiac tissue cannot be measured directly. Instead, the investigator obtains voltage and current measurements and places them into a model of the tissue's structure to infer the impedances of elements of the model. If the model fails to describe major aspects of the real tissue, the results may be worthless, although possibly self-consistent. In the literature of impedance measurement in cardiac tissue, only rarely is the model explicitly described; more commonly, the tissue model is adopted implicitly when equations giving the impedance in terms of voltage and current measurements are adopted. This paper examines the series of models that have been used in specific impedance measurements of cardiac tissue and shows how the same or similar measurements can accurately describe tissue impedivity or can lead to significant errors when inadequate models such as isotropic and anisotropic monodomains (although a part of work of historical merit) are used.  相似文献   
994.
Benign prostatic hyperplasia (BPH) is a common cause of lower urinary tract symptoms (LUTS) in men. Patients with BPH often present with a combination of obstructive and overactive bladder (OAB) symptoms. It is postulated that bladder outlet obstruction (BOO) from BPH results in concomitant OAB symptoms through ischemic induced variations in the response to neurotransmitters of both the detrusor and the urothelium. This altered response leads to the pathologic activation of the micturition reflex, generating sensory dysfunction and involuntary bladder contractions. Alpha-1 adrenoceptor antagonists (alpha-blockers) and 5-alpha reductase inhibitors (5-ARIs) are commonly used to treat the BOO caused by BPH. Anticholinergic agents are frequently used to treat concurrently OAB symptoms caused by the BOO. Unfortunately, anticholinergic medications demonstrate bothersome side effects and a theoretical risk of urinary retention. Basic science and clinical research has led to the development of a new class of pharmaceuticals for the treatment of overactive bladder with diminished risk of urinary retention and lacking many anticholinergic side effects. This novel compound, mirabegron (Mybertriq, Astellas Pharma US, Inc.), is a β3-adrenoceptor agonist and represents a promising new class of oral agents designed for the treatment of OAB symptoms, with minimal effect on voiding.  相似文献   
995.
恒河猴中TTV感染的回顾性实验研究   总被引:1,自引:0,他引:1  
目的:了解接种患者血清的恒河猴能否复制TT病毒(TT virus,TTV),正常恒河猴中是否有TTV感染,分析猴中TTV基因结构特点。方法:用PCR方法检测血清标本中TTV DNA,对TTV DNA阳性的标本进行序列测定。结果:健康猴中无TTV感染;10只接种患者血清的恒河猴中,经验检测有4只为TTV阳性,将其中一株TTV进行序列测定,该序列与日本TTV部分基因相对应位置的核苷酸同源性为96%,将  相似文献   
996.

Background

Arthrofibrosis is a debilitating postoperative complication of total knee arthroplasty (TKA). It is one of the leading causes of hospital readmission and a predominant reason for TKA failure. The prevalence of arthrofibrosis will increase as the annual incidence of TKA in the United States rises into the millions.

Methods

In a narrative review of the literature, the etiology, economic burden, treatment strategies, and future research directions of arthrofibrosis after TKA are examined.

Results

Characterized by excessive proliferation of scar tissue during an impaired wound healing response, arthrofibrotic stiffness causes functional deficits in activities of daily living. Postoperative, supervised physiotherapy remains the first line of defense against the development of arthrofibrosis. Also, adjuncts to traditional physiotherapy such as splinting and augmented soft tissue mobilization can be beneficial. The effectiveness of rehabilitation on functional outcomes depends on the appropriate timing, intensity, and progression of the program, accounting for the patient's ability and level of pain. Invasive treatments such as manipulation under anesthesia, debridement, and revision arthroplasty improve range of motion, but can be traumatic and costly. Future studies investigating novel treatments, early diagnosis, and potential preoperative screening for risk of arthrofibrosis will help target those patients who will need additional attention and tailored rehabilitation to improve TKA outcomes.

Conclusion

Arthrofibrosis is a multi-faceted complication of TKA, and is difficult to treat without an early, tailored, comprehensive rehabilitation program. Understanding the risk factors for its development and the benefits and shortcomings of various interventions are essential to best restore mobility and function.  相似文献   
997.

Background

Debridement-antibiotics-and-implant-retention (DAIR) may be considered a suitable surgical option in periprosthetic joint infections (PJIs) with soundly fixed prostheses, despite chronicity. This study aims to define the long-term outcome following DAIR in hip PJI.

Methods

We reviewed all hip DAIRs performed between 1997 and 2013 (n = 122) to define long-term outcome and identify factors influencing it. Data recorded included patient demographics, medical history, type of DAIR performed (+/? exchange of modular components), and organisms identified. Outcome measures included complications and/or mortality rate, implant survivorship, and functional outcome (Oxford Hip Score).

Results

Most DAIRs (67%) were of primary arthroplasties and 60% were performed within 6 weeks from the index arthroplasty. Infection eradication was achieved in 68% of the first DAIR procedure. In 32 cases, more than one DAIR was required. Infection eradication was achieved in 85% of the cases (104/122) with the (single or multiple) DAIR approach. The most common complication was PJI-persistence (15%), followed by dislocation (14%). Very good functional outcomes were obtained, especially in primary arthroplasties. All streptococcus infections were resolved with DAIR and had better outcome. Twenty-one hips have been revised (17%) to-date, 16 were for persistence of PJI. The 10-y implant survivorship was 77%. Early PJI and exchanging modular components at DAIR were independent factors for a 4-fold increased infection eradication and improved long-term implant survival.

Conclusion

DAIR is, therefore, a valuable option in the treatment of hip PJI, especially in the early postoperative period (≤6 weeks), with good outcomes. However, DAIR is associated with increased morbidity; further surgery may be necessary and instability may occur. Where possible, exchange of modular implants should be undertaken.  相似文献   
998.

Introduction and hypothesis

Several reports have described vaginal prolapse in Mayer–Rokitansky–Küster–Hauser (MRKH) syndrome patients after creation of a neovagina. To our knowledge, no reports of primary vaginal prolapse of a blind pouch without previous intervention, or surgery for this condition, have been described.

Methods

In this case report, we describe a 19-year-old woman with MRKH and complete prolapse of her shortened vaginal pouch. Surgical correction utilizing permanent suture-based sacrospinous ligament fixation was performed.

Results

The patient had a successful outcome.

Conclusions

Sacrospinous ligament fixation provided a safe and effective method for the management of vaginal pouch prolapse. Long-term follow-up is planned. To our knowledge, this is the first report describing surgical repair of primary prolapse of a blind vaginal pouch in the setting of MRKH.
  相似文献   
999.

Background  

Some patients with gastroesophageal reflux disease (GERD) suffer from laryngopharyngeal reflux (LPR). There is no reliable diagnostic test for LPR as there is for GERD. We hypothesized that detection of pepsin (a molecule only made in the stomach) in laryngeal epithelium or sputum should provide evidence for reflux of gastric contents to the larynx, and be diagnostic of LPR. We tested this hypothesis in a prospective study in patients with LPR symptoms undergoing antireflux surgery (ARS).  相似文献   
1000.
Study Type – Prevention (individual cohort)
Level of Evidence 2b What’s known on the subject? and What does the study add? Statin medications reduce inflammation. Inflammation may be important in causing prostate enlargement and lower urinary tract symptoms in aging men. Therefore, statin use may decrease inflammation and help prevent prostate enlargement and lower urinary tract symptoms. Men who took statin medications were less likely to develop an enlarged prostate or lower urinary tract symptoms compared to men who did not take statins. Additionally, men who took statins for the longest period of time had the lowest risk of developing these urological problems. These results suggest that statin use may help prevent common urological problems in aging men.

OBJECTIVE

  • ? To determine whether statin use is associated with a decreased risk of developing benign prostatic enlargement (BPE) and lower urinary tract symptoms (LUTS).

SUBJECTS AND METHODS

  • ? We conducted a retrospective, population‐based cohort study of 2447 men, 40–79 years of age, residing in Olmsted County, MN, USA, in 1990, and followed these men biennially through 2007.
  • ? Cox proportional hazard models were used to assess associations between statin use and new onset of moderate/severe LUTS (American Urological Association Symptom Index score >7), a decreased maximum urinary flow rate (<12 mL/s) or BPE (prostate volume >30 mL).

RESULTS

  • ? Statin use was inversely associated with new onset of LUTS (Hazard ratio (HR) 0.39; 95% confidence interval (CI) 0.31–0.49), a decreased maximum flow rate (HR 0.53; 95% CI 0.34–0.82) and BPE (HR 0.40; 95% CI 0.23–0.69) after adjustment for baseline age and body mass index, diabetes, hypertension, coronary heart disease, smoking, alcohol use, activity level and non‐steroidal anti‐inflammatory use.
  • ? The longest duration of statin use was associated with the lowest risk of developing each outcome (all tests for trend: P < 0.001).

CONCLUSION

  • ? In this study, statin use was associated with a 6.5‐ to 7‐year delay in the new onset of moderate/severe LUTS or BPE.
  • ? While men typically take statin medications to prevent coronary heart disease events and related outcomes, these data suggest that men who use statins may also receive urologic benefits.
  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