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971.
Zhu L  Cui YY  Feng JM  Wu XJ  Chen HZ 《Life sciences》2006,78(14):1617-1623
The relationship between muscarinic receptor affinity states and the contractile response to the muscarinic agonists carbachol, aceclidine, and pilocarpine, has been examined in the isolated rabbit iris muscle. Contraction of the iris muscle by carbachol and aceclidine was more potent and/or more efficacious than the response to pilocarpine. Analysis of [3H]-Quinuclidinyl benzilate (QNB) binding showed that while both carbachol and aceclidine bound to high- and low-affinity forms of the muscarinic receptor, pilocarpine bound to one affinity state. The efficacy of carbachol and aceclidine to stimulate contraction of the iris muscle was consistent with receptor occupancy theory only when considering the low-affinity state of the muscarinic receptor, and activation of the low-affinity rather than high-affinity binding state of the receptor is likely to mediate the contraction of iris muscle. Therefore, the typical anti-glaucoma muscarinic agonists aceclidine and pilocarpine may interact differently with their target receptors in isolated rabbit iris muscle.  相似文献   
972.
In this study, we evaluated the effect of proton pump inhibitors (PPIs) on in vitro antimicrobial activity of tigecycline against several species of clinical pathogens. Clinical non-duplicate isolates of Acinetobacter baumannii, Staphylococcus aureus, Enterococcus faecalis and three species of Enterobacteriaceae (Escherichia coli, Klebsiella pneumonia and Enterobacter cloacae) were collected from a tertiary hospital and their MICs of tigecycline alone and in combination with PPIs (omeprazole, lansoprazole and pantoprazole) were determined. With one randomly selected isolate of each bacterial species, an in vitro time–kill study was performed for the confirmation of the effect of PPIs on tigecycline activity. The MIC changes after PPIs addition correlated with the PPIs concentrations in the test media. Compared with tigecycline alone, the addition of 5 mg/L PPIs could increase the MICs of tigecycline by 0 to 2-fold and the addition of 50 mg/L PPIs could increase the MICs of tigecycline by 4 to >128-fold. The time–kill study confirmed that the addition of PPIs could affect the in vitro activity of tigecycline. Even at low concentration (5 mg/L) of omeprazole and pantoprazole, antagonistic effect could be observed in E. cloacae and E. faecalis strains. We conclude that In vitro activity of tigecycline can be influenced by the presence of PPIs in a concentration-dependent manner.  相似文献   
973.
In China, brucellosis is an endemic disease typically caused by Brucella melitensis infection (biovars 1 and 3). Brucella canis infection in dogs has not traditionally recognized as a major problem. In recent years however, brucellosis resulting from Brucella canis infection has also been reported, suggesting that infections from this species may be increasing. Data concerning the epidemiology of brucellosis resulting from Brucella canis infection is limited. Therefore, the purpose of this study was to assess the diversity among Chinese Brucella canis strains for epidemiological purposes. First, we employed a 16-marker VNTR assay (Brucella MLVA-16) to assess the diversity and epidemiological relationship of 29 Brucella canis isolates from diverse locations throughout China with 38 isolates from other countries. MLVA-16 analysis separated the 67 Brucella canis isolates into 57 genotypes that grouped into five clusters with genetic similarity coefficients ranging from 67.73 to 100%. Moreover, this analysis revealed a new genotype (2-3-9-11-3-1-5-1:118), which was present in two isolates recovered from Guangxi in 1986 and 1987. Second, multiplex PCR and sequencing analysis were used to determine whether the 29 Chinese Brucella canis isolates had the characteristic BMEI1435 gene deletion. Only two isolates had this deletion. Third, amplification of the omp25 gene revealed that 26 isolates from China had a T545C mutation. Collectively, this study reveals that considerable diversity exists among Brucella canis isolates in China and provides resources for studying the genetic variation and microevolution of Brucella.  相似文献   
974.
Accumulating evidence indicates natural killer (NK) cells play crucial roles in successful pregnancy. To investigate whether the killer cell immunoglobulin-like receptor (KIR) gene polymorphism and the corresponding specific HLA ligands in parent couples possessing a susceptibility to unexplained recurrent spontaneous abortion (RSA), we searched 73 pairs of childless couples with three or more abortions characterized as unexplained RSA and 68 pairs of healthy control couples. Peripheral blood was drawn to obtain genomic DNA which was used for a polymerase chain reaction using sequence-specific primers (PCR-SSP) in order to determine whether 15 selected KIR genes and two groups of HLA-C alleles were present. Our result showed that gene frequency of KIR2DS1 was higher in patients with RSA compared to that of control subjects (P =0.029). Increased numbers of activating KIR genes was observed in patients (P =0.041). Women who possessed more than two activating KIR genes were found more frequently in patients than those in control subjects (P =0.018). From a cohort of husband and wife couples, the women with a KIR2DS1 gene, and with a decreased group 2 HLA-C allele for the homologous inhibitory receptor KIR2DL1, had a tendency to fall into the RSA group (P =0.004). The results suggest that a genetic variation at the KIR locus influences the susceptibility to unexplained RSA in the Chinese Han population. Moreover, decreased ligands for inhibitory KIRs could potentially lower the threshold for NK cell activation, mediated through activating receptors, thereby contributing to pathogenesis of RSA.  相似文献   
975.
RecQ helicases play an important role in preserving genomic integrity, and their cellular roles in DNA repair, recombination, and replication have been of considerable interest. Of the five human RecQ helicases identified, three are associated with genetic disorders characterized by an elevated incidence of cancer or premature aging: Werner syndrome, Bloom syndrome, and Rothmund-Thomson syndrome. Although the biochemical properties and protein interactions of the WRN and BLM helicases defective in Werner syndrome and Bloom syndrome, respectively, have been extensively investigated, less information is available concerning the functions of the other human RecQ helicases. We have focused our attention on human RECQ1, a DNA helicase whose cellular functions remain largely uncharacterized. In this work, we have characterized the DNA substrate specificity and optimal cofactor requirements for efficient RECQ1-catalyzed DNA unwinding and determined that RECQ1 has certain properties that are distinct from those of other RecQ helicases. RECQ1 stably bound to a variety of DNA structures, enabling it to unwind a diverse set of DNA substrates. In addition to its DNA binding and helicase activities, RECQ1 catalyzed efficient strand annealing between complementary single-stranded DNA molecules. The ability of RECQ1 to promote strand annealing was modulated by ATP binding, which induced a conformational change in the protein. The enzymatic properties of the RECQ1 helicase and strand annealing activities are discussed in the context of proposed cellular DNA metabolic pathways that are important in the maintenance of genomic stability.  相似文献   
976.
云南澜沧景迈古茶园生态系统植物多样性评价   总被引:5,自引:0,他引:5  
云南澜沧县境内的景迈古茶园是云南省现存面积最大的古茶园.本文应用植物学样地调查和农业生物多样性调查评价(HH-ABA)方法,在景迈古茶园内设置了78个20 m×20 m的样方,对植物多样性进行调查,并就古茶园的管理及资源利用等问题进行了问卷调查和农户访谈.研究结果表明,景迈芒景地区植物地理成分的热带性明显.在景迈古茶园中发现的珍稀濒危保护植物达15种,其中濒危种5个,易危种7个,稀有种3个,含国家三级保护植物11种.从古茶园、天然林、新式茶园3类生态系统的物种多样性分析来看,古茶园与天然林较为接近而比新式茶园高得多,因而在该区生物多样性的维护上起着非常重要的作用.古茶园的物种数按照生活型排序为草本>乔木>灌木>藤本>附生.与天然林相比,古茶园内乔木和灌木种类的比例减少,草本和附生(寄生)植物的比例大大增加,这与古茶园内乔木郁闭度及茶树的存在密切相关.农业生物多样性分析显示,不同村寨的物种丰富度和物种利用率均存在差异.6个村寨的农业物种丰富度指数的平均值为0.059,高于同纬度地区旱谷地和橡胶林,可见人们在古茶园管理中有意识地保留了可利用的物种.由于不同农户采取的管理措施不同,影响了古茶园内的植物多样性和古茶树的更新,因而使各农户的茶叶经济效益存在差别.古茶园生态系统是自然资源保护与利用相结合的典型例子,建议应当传承并发展当地人民对古茶园的管理经验,由政府、科研机构和农户共同参与,通过示范和培训加强学习指导,对古茶园进行保护和合理的开发利用.  相似文献   
977.
32℃高温对天蚕(Antheraea yamamai)卵黄发生影响明显,其中影响程度与开始经受32℃处理时天蚕发育阶段有关。结茧后第1天开始即受32℃处理时,脂肪体和血淋巴中卵黄原蛋白(Vg)与可溶性蛋白含量均低于受26℃处理的;化蛹后第1天开始即受32℃处理时,脂肪体中Vg滴度与26℃下的基本无明显差异,但血淋巴和卵巢中Vg或卵黄磷蛋白含量(Vt)均低于26℃的;而在化蛹后第6天开始受32℃处理时,脂肪体和血淋巴中Vg含量与26℃的无明显差异,卵巢中Vt则明显高于26℃的。此外,曾就化蛹后第1或6天开始受32℃处理后脂肪体、血淋巴和卵巢中可溶性蛋白含量的变化作了检测。建议在饲育或保护制种用茧蚕时,老熟幼虫和化蛹初期的蚕蛹不宜接触32℃高温。  相似文献   
978.
山岳型风景旅游区生态负荷与环境建设研究:泰山实证分析   总被引:13,自引:0,他引:13  
运用旅游生态学原理和方法,提出了测算山岳型风景旅游区生态负荷综合分级指数的8项1级指标和6项2级指标及计算模式。以泰山风景旅游区为案例进行了应用研究,将13个地块单元(功能区)按生态负荷强度大小划分为3级,并依据可持续发展理论提出了强负荷区生态补偿的方案,为山岳型风景旅游区寻求环境与旅游经济活动的协调发展提供可借鉴的研究方案和具体措施.  相似文献   
979.
980.
Platelets play a critical role in the pathophysiology of peripheral arterial disease (PAD). The mechanisms by which muscle ischemia regulates aggregation of platelets are poorly understood. We have recently identified the Nod-like receptor nucleotide-binding domain leucine rich repeat containing protein 3 (NLRP3) expressed by platelets as a critical regulator of platelet activation and aggregation, which may be triggered by activation of toll-like receptor 4 (TLR4). In this study, we performed femoral artery ligation (FAL) in transgenic mice with platelet-specific ablation of TLR4 (TLR4 PF4) and in NLRP3 knockout (NLRP3?/?) mice. NLRP3 inflammasome activity of circulating platelets, as monitored by activation of caspase-1 and cleavage of interleukin-1β (IL-1β), was upregulated in mice subjected to FAL. Genetic ablation of TLR4 in platelets led to decreased platelet caspase 1 activation and platelet aggregation, which was reversed by the NLRP3 activator Nigericin. Two weeks after the induction of FAL, ischemic limb perfusion was increased in TLR4 PF4 and NLRP3?/? mice as compared to control mice. Hence, activation of platelet TLR4/NLRP3 signaling plays a critical role in upregulating platelet aggregation and interfering with perfusion recovery in muscle ischemia and may represent a therapeutic target to improve limb salvage.  相似文献   
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