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   8439篇
  免费   429篇
  国内免费   38篇
耳鼻咽喉   144篇
儿科学   438篇
妇产科学   221篇
基础医学   856篇
口腔科学   222篇
临床医学   691篇
内科学   1866篇
皮肤病学   159篇
神经病学   582篇
特种医学   301篇
外科学   1695篇
综合类   179篇
一般理论   2篇
预防医学   369篇
眼科学   192篇
药学   494篇
中国医学   32篇
肿瘤学   463篇
  2023年   72篇
  2022年   213篇
  2021年   329篇
  2020年   196篇
  2019年   226篇
  2018年   275篇
  2017年   186篇
  2016年   237篇
  2015年   260篇
  2014年   387篇
  2013年   504篇
  2012年   653篇
  2011年   652篇
  2010年   378篇
  2009年   299篇
  2008年   493篇
  2007年   553篇
  2006年   527篇
  2005年   480篇
  2004年   421篇
  2003年   361篇
  2002年   307篇
  2001年   112篇
  2000年   93篇
  1999年   74篇
  1998年   39篇
  1997年   22篇
  1996年   31篇
  1995年   38篇
  1994年   30篇
  1993年   29篇
  1992年   44篇
  1991年   50篇
  1990年   28篇
  1989年   43篇
  1988年   29篇
  1987年   21篇
  1986年   24篇
  1985年   20篇
  1984年   18篇
  1983年   15篇
  1982年   8篇
  1981年   21篇
  1980年   14篇
  1979年   10篇
  1978年   9篇
  1977年   10篇
  1973年   7篇
  1972年   6篇
  1967年   12篇
排序方式: 共有8906条查询结果,搜索用时 0 毫秒
131.
132.
Objective:Premature thelarche (PT) is defined as isolated breast development in girls before eight years of age. Gonadotropin-releasing hormone (GnRH) stimulation test is sometimes used to distinguish between PT and central precocious puberty (CPP), although the interpretation of the test at early ages is challenging. The objective of this study was to determine the follicle stimulating hormone (FSH) and luteinizing hormone (LH) responses to GnRH stimulation in girls with PT below 3 years of age.Methods:A standardized GnRH stimulation test, bone age and pelvic ultrasound were evaluated and those without pubertal progression after a minimum of one-year follow up were included in the study.Results:On GnRH stimulation test, the median (range) baseline LH was 0.29 (0.10-0.74) IU/L, baseline FSH was 4.96 (3.18-7.05) mIU/mL, and the peak median LH was 5.75 (3.31-8.58) IU/L with the peak mean±standard deviation FSH was 40.38±20.37 mIU/mL. Among the patients, 33.3% (n=10) had baseline LH >0.3 IU/L, 67% (n=20) had peak LH >5 IU/l and 16.6% (n=5) >10 IU/L. The mean peak LH/FSH ratio was 0.17±0.09 and was ≤0.43 in all participants.Conclusion:Although consensus statements usually define baseline LH >0.3-0.5 IU/L, peak LH >5 IU/L, and LH/FSH ratios >0.66-1.0 as diagnostic cut-offs for CPP, in children below 3 years of age, the baseline and peak LH values may be similar to pubertal values, possibly due to mini-puberty. A dominant FSH response on GnRH stimulation test is more valuable than the peak LH response in the diagnosis of PT.  相似文献   
133.
134.
Objectives:To explore the changing patterns of long-stay patients (LSP) to improve the utilization of pediatric intensive care units (PICUs) resources.Methods:This is a 2-points cross-sectional study (5 years apart; 2014-2019) conducted among PICUs and SCICUs in Riyadh, Saudi Arabia. Children who have stayed in PICU for more than 21 days were included.Results:Out of the 11 units approached, 10 (90%) agreed to participate. The prevalence of LSP in all these hospitals decreased from 32% (48/150) in 2014 to 23.4% (35/149) in 2019. The length of stay ranged from 22 days to 13.5 years. The majority of LSP had a neuromuscular or cardiac disease and were admitted with respiratory compromise. Ventilator-associated pneumonia was the most prevalent complication (37.5%). The most commonly used resources were mechanical ventilation (93.8%), antibiotics (60.4%), and blood-products transfusions (35.4%). The most common reason for the extended stay was medical reasons (51.1%), followed by a lack of family resources (26.5%) or lack of referral to long-term care facilities (22.4%).Conclusion:A long-stay is associated with significant critical care bed occupancy, complications, and utilization of resources that could be otherwise utilized as surge capacity for critical care services. Decreasing occupancy in this multicenter study deserves further engagement of the healthcare leaders and families to maximize the utilization of resources.  相似文献   
135.
The production of a high-value xylooligosaccharide (XOS) prebiotic product from lignocellulosic autohydrolysate requires processing for the removal of non-carbohydrate components such as lignin and furfural. In this research, the nature of XOS dissolved in autohydrolysate is evaluated including the XOS degree of polymerization (DP) distribution and potential covalent association between XOS and lignin (LCC). The impact of these factors on the yield of XOS during treatment of Miscanthus autohydrolysate with hydrophobic resin is assessed. Over 30% of the XOS in autohydrolysate was found to be likely associated with lignin (“tied” XOS), all of which was removed during hydrophobic resin treatment along with over 90% of the dissolved lignin. However, loss of dissolved XOS during resin treatment was found to not be due solely to XOS association with lignin. Over 50% of the “free,” non-lignin-associated XOS was also removed by resin treatment. Interaction between “free” XOS and the hydrophobic resin was found to be highly dependent on DP with higher DP XOS being removed far more readily than low DP XOS. Over 80% of dissolved “free” XOS with a DP of six and above (X6+) was removed from autohydrolysate during treatment while only 17% of xylose (X1) was removed. Efforts to understand the interaction between the hydrophobic resin and XOS and to improve the recovery of XOS during hydrophobic resin treatment are presented.

∼30% of xylooligosaccharides (XOS) in autohydrolysate are likely bonded to lignin “tied,” contributing to loss during resin purification. Loss of “free” XOS depends on DP.  相似文献   
136.
Genomic characterization of translocation breakpoints is relevant to identify possible mechanisms underlying their origin. The consistent association of anthracylines (e.g., epirubicin and idarubicin) in inducing therapy‐related acute leukemias (t‐AL) with mixed lineage leukemia (MLL) gene rearrangement suggests that MLL translocations are causative events for t‐AL. Using asymmetric multiplex PCR strategy followed by direct DNA sequencing, we characterized the genomic breakpoints of the MLL and AFF1 genes in two patients who developed t‐AL with t(4;11)(q21;q23). Chemotherapeutic treatment of the primary disease in both patients included topoisomerase II (topo II) targeting agents. In one case, the MLL breakpoint was located in intron 9 at nucleotide position chr11:118354284 while the AFF1 breakpoint was in intron 3 at nucleotide position chr4:87992070. The breakpoint junction sequences revealed an insertion of two nucleotides at the MLL‐AFF1 junction. In the other patient, the MLL breakpoint was located in intron 11 at nucleotide position chr11:118359130‐32 and the AFF1 break was in intron 3 at nucleotide position chr4:87996215‐17. The MLL breakpoint found in the latter patient was identical to that of two previously reported cases, strongly suggesting the presence of a preferential site of DNA cleavage in the presence of topo II inhibitor. In addition, microhomologies at the breakpoint junctions were indicative of DNA repair by the non‐homologous end joining (NHEJ) pathway. This study further supports the evidence that MLL breakpoints in therapy‐related acute leukemia with MLL‐AFF1 are clustered in the telomeric half of the breakpoint cluster region that contains topo II recognition sites. © 2013 Wiley Periodicals, Inc.  相似文献   
137.
138.
Anabolic‐androgenic steroids are synthetic compounds prohibited due to their performance‐enhancing characteristics. The use of these substances is known to cause health‐related issues, which highlights the importance of being able to evaluate the scale of consumption by the general population. However, most available research on the analysis of anabolic steroids is focused on animals and athletes in connection with doping. The potential of wastewater‐based epidemiology as an intelligence tool for the assessment of community level use of anabolic steroids is presented herein. A liquid chromatography tandem mass spectrometry method was developed for the analysis of 10 anabolic‐androgenic steroids and 14 endogenous hormones in influent wastewater. The validated method was applied to sixteen 24‐hour composite wastewater influent samples that were collected over a period of five years from two wastewater treatment plants in Queensland, Australia. Nine investigated compounds were found to be present at concentrations between 14 and 611 ng L?1 which translated into 3–104 mg excreted per 1000 individuals per day. It was concluded that the developed analytical method is suitable for the analysis of AAS in wastewater matrix. Additionally, both the inclusion of metabolites and further investigation into deconjugation by enzymatic hydrolysis would aid in understanding and evaluating community anabolic steroid use. For the first time, this study presents the application of wastewater‐based epidemiology on anabolic‐androgenic steroids in Australia.  相似文献   
139.
Objective:To determine the patterns of resistance to first line anti-tuberculosis(TB)drugs among a collection of Mycobacterium tuberculosis(MTB)isolates from 5 provinces of Iran.Methods:A total of the 6 426 clinical specimens from patients suspected of active TB were collected from March 2010 to June 2012.All specimens were subjected for microscopy and culture tests in the TB centers of studies provinces.Drug susceptibility testing to the first line anti-TB drugs for culture positive MTB was performed on Lwenstein-Jensen(LJ)medium using proportion method.Results:Of 6 426 clinical specimens,261 were culture positive for mycobacteria,of which 252 were MTB and 9 were MOTT(mycobacteria other than tuberculosis).Of 252 MTB isolates.211(83.7%)were pan-susceptible and 41(16.3%)were resistant to at least one drug.Resistance was most common to streptomycin.30 isolates(12.0%),followed by isoniuzid,20isolates(8.0%),rifampin,15 isolates(6.0%)and ethambutol,14 isolates(5.5%).Sixteen(6.3%)MTB isolates were MDR.A clear evidence of heterogeneity amongst the 5 provinces in the proportions with resistance to one or more drugs was observed[χ~2=12.209(4 degrees of freedom),P values=0.015 9].Conclusions:The prevalence of drug resistance in this study area underscoring the need for further enforcement of TB control strategies in the Iran.Drug susceptibility testing for all TB cases to provide optimal treatment,establishing advanced diagnostic facilities for rapid detection of MDR-TB and continuous monitoring of drug resistance are recommended for prevention and control of drug-resistant TB.  相似文献   
140.
The nucleotide-binding oligomerization domain (NOD)-like receptor family pyrin domain containing 12 (NLRP12) plays a protective role in intestinal inflammation and carcinogenesis, but the physiological function of this NLR during microbial infection is largely unexplored. Salmonella enterica serovar Typhimurium (S. typhimurium) is a leading cause of food poisoning worldwide. Here, we show that NLRP12-deficient mice were highly resistant to S. typhimurium infection. Salmonella-infected macrophages induced NLRP12-dependent inhibition of NF-κB and ERK activation by suppressing phosphorylation of IκBα and ERK. NLRP12-mediated down-regulation of proinflammatory and antimicrobial molecules prevented efficient clearance of bacterial burden, highlighting a role for NLRP12 as a negative regulator of innate immune signaling during salmonellosis. These results underscore a signaling pathway defined by NLRP12-mediated dampening of host immune defenses that could be exploited by S. typhimurium to persist and survive in the host.The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family consists of a large number of intracellular pathogen recognition receptors that function as sensors of microbial-derived and danger-associated molecules in the cytoplasm of host cells. A subset of NLR proteins, including NLRP1, NLRP3, and NLRC4, activate caspase-1 via the formation of a cytosolic multiprotein complex termed the inflammasome (1). These inflammasome-forming NLRs mediate processing of the proinflammatory cytokines pro–IL-1β and pro–IL-18, which are then secreted by the cell. The non–inflammasome-forming members of the NLR family contribute to regulation of other key inflammatory pathways. For example, NOD1 and NOD2 activate NF-κB and MAPK pathways (25), whereas NLRP6, NLRC3, NLRC5, and NLRX1 have been demonstrated to regulate inflammation negatively (69).NLRP12 (NALP12, MONARCH-1, or PYPAF7) is a poorly characterized member of the NLR family. It has a tripartite domain structure, which consists of an N-terminal PYRIN domain, a central nucleotide binding site domain, and a C-terminal domain composed of at least 12 leucine-rich repeat motifs (10). In humans, NLRP12 is expressed in peripheral blood leukocytes, including granulocytes, eosinophils, monocytes, and dendritic cells (DCs) (10, 11). Similarly, mouse NLRP12 is highly expressed in bone marrow neutrophils and granulocytes, macrophages, and DCs (12, 13). Genetic studies in humans have shown that mutations in the NLRP12 gene are associated with periodic fever syndromes and atopic dermatitis (1416). More recent studies have demonstrated that NLRP12 has both inflammasome-dependent and inflammasome-independent roles in health and disease. Our laboratory and others have previously reported that NLRP12 mediates protection against colon inflammation and tumorigenesis in vivo by negatively regulating inflammatory responses (12, 17).Recent studies have revealed a potential role for NLRP12 during infectious diseases. Vladimer et al. (18) reported that Nlrp12−/− mice are hypersusceptible to Yersinia pestis infection, whereby NLRP12 is required to drive caspase-1 activation and IL-1β and IL-18 release. Another study found that WT and Nlrp12−/− mice exhibit similar host innate responses in lung infections induced by Mycobacterium tuberculosis or Klebsiella pneumoniae (13). However, in vitro studies reported that a synthetic analog cord factor, trehalose-6,6-dimycolate (TDP), from M. tuberculosis and LPS from K. pneumoniae induced substantially elevated levels of TNF-α and IL-6 in Nlrp12−/− bone marrow-derived DCs compared with their WT counterpart, although levels of secreted IL-1β were not changed (13). These results suggest that unlike the case in Yersinia infection, NLRP12 does not contribute to inflammasome-mediated protection against M. tuberculosis and K. pneumoniae infections. Overall, the physiological and functional relevance of NLRP12 in the host defense against infectious diseases is not fully understood.Salmonella enterica serovar Typhimurium (S. typhimurium) is a Gram-negative intracellular pathogen, and one of the most prevalent etiological agents of gastroenteritis worldwide. Salmonella infection accounts for 93.8 million cases of gastroenteritis annually in the world and is a leading cause of death among bacterial foodborne pathogens in the United States (19, 20). Previous studies have found that members of the Toll-like receptor (TLR) family, especially TLR4, are critical for the recognition and clearance of S. typhimurium (21, 22). One consequence of Salmonella-induced TLR activation is the production of inflammatory cytokines and antimicrobial compounds, including pro–IL-1β, pro–IL-18, IFN-γ, TNF-α, and reactive oxygen species, which are critical mediators for the control of bacterial growth in host tissues (23). In addition to TLR-mediated host responses, certain members of the NLR family, including NLRC4 and NLRP3, initiate inflammasome formation to drive processing and release of IL-1β and IL-18 following Salmonella infection (24, 25). Although the precise signals that trigger NLRP3 activation during Salmonella infection are unknown, NLRC4 is activated by NAIPs, a subset of receptors within the NLR family that detect Salmonella flagellin (mouse NAIP5 and NAIP6) or certain rod (mouse NAIP2) or needle (human NAIP and mouse NAIP1) proteins associated with the Salmonella type III secretion system (2630). Nevertheless, the functional relevance of NLRP12 in response to Salmonella infection is unknown.Here, we show that NLRP12 negatively regulates antibacterial host defense during Salmonella infection independent of inflammasomes. NLRP12 inhibited TLR-induced NF-κB activation by dampening phosphorylation of IκBα and ERK, consequently enhancing intracellular bacterial survival. Together, our work unveiled an NLRP12-dependent innate immune pathway that may be strategically exploited by S. typhimurium to persist and survive in the host.  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