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   5819篇
  免费   443篇
  国内免费   51篇
耳鼻咽喉   40篇
儿科学   132篇
妇产科学   132篇
基础医学   1091篇
口腔科学   96篇
临床医学   502篇
内科学   1469篇
皮肤病学   178篇
神经病学   593篇
特种医学   83篇
外科学   562篇
综合类   26篇
一般理论   3篇
预防医学   428篇
眼科学   81篇
药学   456篇
中国医学   21篇
肿瘤学   420篇
  2024年   5篇
  2023年   91篇
  2022年   123篇
  2021年   404篇
  2020年   192篇
  2019年   265篇
  2018年   286篇
  2017年   183篇
  2016年   224篇
  2015年   225篇
  2014年   307篇
  2013年   346篇
  2012年   492篇
  2011年   519篇
  2010年   271篇
  2009年   231篇
  2008年   362篇
  2007年   353篇
  2006年   311篇
  2005年   298篇
  2004年   236篇
  2003年   212篇
  2002年   197篇
  2001年   20篇
  2000年   8篇
  1999年   33篇
  1998年   28篇
  1997年   22篇
  1996年   13篇
  1995年   10篇
  1994年   2篇
  1993年   4篇
  1992年   7篇
  1991年   4篇
  1990年   5篇
  1988年   1篇
  1987年   4篇
  1983年   1篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1977年   2篇
  1975年   2篇
  1974年   1篇
  1973年   3篇
  1969年   1篇
  1968年   1篇
  1963年   1篇
  1931年   1篇
  1928年   1篇
排序方式: 共有6313条查询结果,搜索用时 15 毫秒
51.
In the natural environment, bacteria predominantly exist in matrix‐enclosed multicellular communities associated with various surfaces, referred to as biofilms. Bacteria in biofilms are extremely resistant to antibacterial agents thus causing serious problems for antimicrobial therapy. In this study, we showed that different plant phenolic compounds, at concentrations that did not or weakly suppressed bacterial growth, increased the capacity of Pseudomonas aeruginosa PAO1 to form biofilms. Biofilm formation of P. aeruginosa PAO1 was enhanced 3‐ to 7‐fold under the action of vanillin and epicatechin, and 2‐ to 2.5‐fold in the presence of 4‐hydroxybenzoic, gallic, cinnamic, sinapic, ferulic, and chlorogenic acids. At higher concentrations, these compounds displayed an inhibiting effect. Similar experiments carried out for comparison with Agrobacterium tumefaciens C58 showed the same pattern. Vanillin, 4‐hydroxybenzoic, and gallic acids at concentrations within the range of 40 to 400 μg/mL increased the production of N–3‐oxo‐dodecanoyl‐homoserine lactone in P. aeruginosa PAO1 which suggests a possible relationship between stimulation of biofilm formation and Las Quorum Sensing system of this bacterium. Using biosensors to detect N‐acyl‐homoserine lactones (AHL), we demonstrated that the plant phenolics studied did not mimic AHLs.  相似文献   
52.
53.
We studied the epidemiology of drug-resistant tuberculosis (TB) in Vladimir Region, Russia, in 2012. Most cases of multidrug-resistant TB (MDR TB) were caused by transmission of drug-resistant strains, and >33% were in patients referred for testing after mass radiographic screening. Early diagnosis of drug resistance is essential for preventing transmission of MDR TB.  相似文献   
54.
Hospital chaplaincy and spiritual care services are important to patients’ medical care and well-being; however, little is known about healthcare providers’ experiences receiving spiritual support. A phenomenological study examined the shared experience of spiritual care between hospital chaplains and hospital-based healthcare providers (HBHPs). Six distinct themes emerged from the in-depth interviews: Awareness of chaplain availability, chaplains focus on building relationships with providers and staff, chaplains are integrated in varying degrees on certain hospital units, chaplains meet providers’ personal and professional needs, providers appreciate chaplains, and barriers to expanding hospital chaplains’ services. While HBHPs appreciated the care received and were able to provide better patient care as a result, participants reported that administrators may not recognize the true value of the care provided. Implications from this study are applied to hospital chaplaincy clinical, research, and training opportunities.  相似文献   
55.
ObjectiveThis study aimed to evaluate the concurrent validity and reliability of a low-cost digital dynamometer to assess maximal isometric strength in neck movements.MethodsTwelve recreationally active participants (6 women, 6 men; age: 24.1 ± 3.4 years; height: 1.71 ± 0.06 m; weight: 64.6 ± 11.7 kg) performed neck flexion, extension, and lateral flexion, and maximal isometric strength was simultaneously measured using an isokinetic dynamometer (gold standard) and a digital dynamometer to evaluate the concurrent validity of the latter. One week later, all the participants repeated 3 trials of each neck movement (3 minutes apart) registered only with the digital dynamometer. The first and second trial were guided by tester 1 and the third trial was guided by tester 2.ResultsThe concurrent validity of the digital dynamometer showed a nearly perfect correlation between both devices (r > 0.986, P < .001), with Bland-Altman plots showing absolute agreement. Intertester and intratester reliability were nearly perfect for all neck movements (intraclass correlation coefficient > 0.86).ConclusionThe low-cost digital dynamometer showed valid and reliable measurements of maximal isometric strength in neck movements.  相似文献   
56.
The effect of the methylating compound streptozotocin (STZ) on interstitial telomeric sequences (ITSs) was investigated in Chinese hamster ovary (CHO) cells by using peptide nucleic acid‐fluorescence in situ hybridization with a pantelomeric probe. Cells were exposed to increasing concentrations of STZ, and chromosomal aberrations were analyzed at the first mitosis after treatment. The frequency of chromosomal aberrations directly involving ITSs increased in STZ‐treated cells by a factor of 2.6 (2 mM) and 3.6 (4 mM) when compared with the frequency of these aberrations in control cells (P < 0.05). However, no significant differences were found between control and exposed cells in the percentage of aberrations directly involving ITSs, demonstrating that these repeat regions were not preferentially involved in the chromosome damage induced by STZ. In addition, STZ did not alter telomerase activity, suggesting that this enzyme may not be involved in the induction of chromosomal aberrations by this compound. Environ. Mol. Mutagen., 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
57.
While conflict-induced forced migration is a global phenomenon, the situation in Colombia, South America, is distinctive. Colombia has ranked either first or second in the number of internally displaced persons for 10 years, a consequence of decades of armed conflict compounded by high prevalence of drug trafficking. The displacement trajectory for displaced persons in Colombia proceeds through a sequence of stages: (1) pre-expulsion threats and vulnerability, (2) expulsion, (3) migration, (4) initial adaptation to relocation, (5) protracted resettlement (the end point for most forced migrants), and, rarely, (6) return to the community of origin. Trauma signature analysis, an evidence-based method that elucidates the physical and psychological consequences associated with exposures to harm and loss during disasters and complex emergencies, was used to identify the psychological risk factors and potentially traumatic events experienced by conflict-displaced persons in Colombia, stratified across the phases of displacement. Trauma and loss are experienced differentially throughout the pathway of displacement.  相似文献   
58.
fMRI studies of brain activity at rest study slow (<0.1 Hz) intrinsic fluctuations in the blood‐oxygenation‐level‐dependent (BOLD) signal that are observed in a temporal scale of several minutes. The origin of these fluctuations is not clear but has previously been associated with slow changes in rhythmic neuronal activity resulting from changes in cortical excitability or neuronal synchronization. In this work, we show that individual spontaneous BOLD events occur during rest, in addition to slow fluctuations. Individual spontaneous BOLD events were identified by deconvolving the hemodynamic impulse response function for each time point in the fMRI time series, thus requiring no information on timing or a‐priori spatial information of events. The patterns of activation detected were related to the motor, visual, default‐mode, and dorsal attention networks. The correspondence between spontaneous events and slow fluctuations in these networks was assessed using a sliding window, seed‐correlation analysis, where seed regions were selected based on the individual spontaneous event BOLD activity maps. We showed that the correlation varied considerably over time, peaking at the time of spontaneous events in these networks. By regressing spontaneous events out of the fMRI signal, we showed that both the correlation strength and the power in spectral frequencies <0.1 Hz decreased, indicating that spontaneous activation events contribute to low‐frequency fluctuations observed in resting state networks with fMRI. This work provides new insights into the origin of signals detected in fMRI studies of functional connectivity. Hum Brain Mapp, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
59.
60.
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