全文获取类型
收费全文 | 242829篇 |
免费 | 7390篇 |
国内免费 | 5080篇 |
专业分类
耳鼻咽喉 | 1539篇 |
儿科学 | 7289篇 |
妇产科学 | 3854篇 |
基础医学 | 24966篇 |
口腔科学 | 2725篇 |
临床医学 | 21555篇 |
内科学 | 40925篇 |
皮肤病学 | 1431篇 |
神经病学 | 19886篇 |
特种医学 | 11308篇 |
外国民族医学 | 41篇 |
外科学 | 35669篇 |
综合类 | 14323篇 |
现状与发展 | 18篇 |
一般理论 | 2篇 |
预防医学 | 22266篇 |
眼科学 | 4548篇 |
药学 | 16720篇 |
76篇 | |
中国医学 | 4300篇 |
肿瘤学 | 21858篇 |
出版年
2024年 | 236篇 |
2023年 | 1226篇 |
2022年 | 2912篇 |
2021年 | 3651篇 |
2020年 | 2673篇 |
2019年 | 2423篇 |
2018年 | 24082篇 |
2017年 | 19282篇 |
2016年 | 21392篇 |
2015年 | 4053篇 |
2014年 | 4752篇 |
2013年 | 4013篇 |
2012年 | 11643篇 |
2011年 | 26450篇 |
2010年 | 21923篇 |
2009年 | 13902篇 |
2008年 | 22761篇 |
2007年 | 25058篇 |
2006年 | 4101篇 |
2005年 | 5532篇 |
2004年 | 5514篇 |
2003年 | 6445篇 |
2002年 | 4255篇 |
2001年 | 1950篇 |
2000年 | 2168篇 |
1999年 | 2123篇 |
1998年 | 1446篇 |
1997年 | 1550篇 |
1996年 | 1093篇 |
1995年 | 985篇 |
1994年 | 861篇 |
1993年 | 543篇 |
1992年 | 637篇 |
1991年 | 601篇 |
1990年 | 567篇 |
1989年 | 468篇 |
1988年 | 375篇 |
1987年 | 320篇 |
1986年 | 271篇 |
1985年 | 201篇 |
1984年 | 122篇 |
1983年 | 91篇 |
1982年 | 62篇 |
1981年 | 52篇 |
1980年 | 67篇 |
1979年 | 40篇 |
1938年 | 60篇 |
1934年 | 30篇 |
1932年 | 56篇 |
1930年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Chou TH Wang S Sakhatskyy PV Mboudjeka I Mboudoudjeck I Lawrence JM Huang S Coley S Yang B Li J Zhu Q Lu S 《Virology》2005,334(1):134-143
Inactivated severe acute respiratory syndrome-associated coronavirus (SARS-CoV) has been tested as a candidate vaccine against the re-emergence of SARS. In order to understand the efficacy and safety of this approach, it is important to know the antibody specificities generated with inactivated SARS-CoV. In the current study, a panel of twelve monoclonal antibodies (mAbs) was established by immunizing Balb/c mice with the inactivated BJ01 strain of SARS-CoV isolated from the lung tissue of a SARS-infected Chinese patient. These mAbs could recognize SARS-CoV-infected cells by immunofluorescence analysis (IFA). Seven of them were mapped to the specific segments of recombinant spike (S) protein: six on S1 subunit (aa 12-798) and one on S2 subunit (aa 797-1192). High neutralizing titers against SARS-CoV were detected with two mAbs (1A5 and 2C5) targeting at a subdomain of S protein (aa 310-535), consistent with the previous report that this segment of S protein contains the major neutralizing domain. Some of these S-specific mAbs were able to recognize cleaved products of S protein in SARS-CoV-infected Vero E6 cells. None of the remaining five mAbs could recognize either of the recombinant S, N, M, or E antigens by ELISA. This study demonstrated that the inactivated SARS-CoV was able to preserve the immunogenicity of S protein including its major neutralizing domain. The relative ease with which these mAbs were generated against SARS-CoV virions further supports that subunit vaccination with S constructs may also be able to protect animals and perhaps humans. It is somewhat unexpected that no N-specific mAbs were identified albeit anti-N IgG was easily identified in SARS-CoV-infected patients. The availability of this panel of mAbs also provided potentially useful agents with applications in therapy, diagnosis, and basic research of SARS-CoV. 相似文献
992.
Current models hold that CD4+ depletion occurs as a result of direct and indirect effects of HIV, which both kill peripheral CD4+ cells and prevent adequate regeneration. Although age-associated involution diminishes thymic reserve and HIV is clearly thymotoxic, clinical trials have nonetheless shown that large proportions of patients who sustain adequate control of viral replication with highly active antiretroviral therapy (HAART) will demonstrate some evidence for thymic-dependent immune reconstitution, which is associated with improved immune competence. Furthermore, patients with insufficient or absent immune reconstitution following HAART generally lack evidence for thymopoiesis. Current studies are focused on improving our understanding of the causes for thymic failure in HIV infection. Recent work has demonstrated that some HIV strains, especially those that are CXCR4 trophic, are more thymotoxic and may contribute to irreversible thymic damage in this population. 相似文献
993.
Wen FQ Kohyama T Sköld CM Zhu YK Liu X Romberger DJ Stoner J Rennard SI 《Inflammation》2002,26(6):279-290
TGF- is thought to play a central role in pulmonary fibrosis inducing fibroblast differentiation and extracellular matrix synthesis. In human lung fibroblasts, it is still unclear how various TGB- isoforms affect TGF- production and whether glucocorticoids, commonly used agents to treat fibrotic lung disease, modulate these processes. To this end, human fetal lung fibroblasts (HFL-1) were cultured with various concentrations of glucocorticoids (budesonide, dexamethasone or hydrocortisone) with and without TFG-1, -2, and -3. TGF- mRNA was assessed by real time RT-PCR. Smad 2, 3, and 4 and AP-1 complex (c-fos and c-Jun) cellular localization were evaluated by immunostaining. TGF-2 and -3 stimulated TGF-1 production significantly (p < 0.01 relative to control). TGF-1 stimulated TGF-2 production (p < 0.01 relative to control). TGF-3 was undetectable. Glucocorticoids significantly inhibited TGF-1 and -2 production and reduced expression of the upregulated TGF-1 and -2 mRNA induced by exogenous TGF-1, -2 or -3 (p < 0.01 for each) but had no effect on Smads. Although c-jun-related nuclear staining was not intensified in TGF--stimulated cells, it was reduced by glucocorticoids. Thus, TGF- isoforms may stimulate production of various TGF- isoforms in the lung. Glucocorticoids then may block TGF- production by modulating mRNA levels and c-Jun. 相似文献
994.
免疫磁珠法分离白血病转基因小鼠骨髓造血干细胞 总被引:1,自引:0,他引:1
本文分离转基因小鼠骨髓造血干细胞。运用针对小鼠干细胞表面特异表达的干细胞抗原 1(stemcellantigen 1,Sca 1)的单克隆抗体和包被于磁颗粒表面的第二抗体 ,采用磁吸附细胞分选方法 (MACS )分离小鼠骨髓造血干细胞 ,用流式细胞术 (FACS )检测MACS分离后骨髓细胞中干细胞 (Sca 1阳性细胞 )比例 ,监测细胞分选效果。结果显示MACS分离后骨髓细胞中Sca 1阳性细胞所占比例达 85 %以上 ,涂片观察发现细胞组成和细胞形态学特征与FACS所得结果一致。MACS可以从转基因小鼠全骨髓细胞中分离出Sca 1阳性的骨髓造血干细胞 ,细胞纯度可达 85 %以上。 相似文献
995.
Primary sensory neurons can generate irregular burst firings in which the existence of significant deterministic behaviors of chaotic dynamics has been proved with nonlinear time series analysis. But how well the deterministic characteristics and neural information of presynaptic chaotic spike trains were transmitted into postsynaptic spike trains is still an open question. Here we investigated the synaptic transmission of chaotic spike trains between primary Adelta afferent fiber and spinal dorsal horn neuron. Two kinds of basic stimulus unit, brief burst and single pulse, were employed by us to comprise chaotic stimulus trains. For time series analysis, we defined "events" as the longest sequences of spikes with all interspike intervals less than or equal to a certain threshold and extracted the interevent intervals (IEIs) from spike trains. Return map analysis of the IEI series showed that the main temporal structure of chaotic input trains could be detected in postsynaptic output trains, especially under brief-burst stimulation. Using correlation dimension and nonlinear prediction methods, we found that synaptic transmission could influence the nonlinear characteristics of chaotic trains, such as fractal dimension and short-term predictability, with greater influence made under single-pulse stimulation. By calculating the mutual information between input and output trains, we found the information carried by presynaptic spike trains could not be completely transmitted at primary afferent synapses, and that brief bursts could more reliably transmit the information carried by chaotic input trains across synapses. These results indicate that although unreliability exists during synaptic transmission, the main deterministic characteristics of chaotic burst trains can be transmitted across primary afferent synapses. Moreover, brief bursts that come from the periphery can more reliably transmit neural information between primary afferent fibers and spinal dorsal horn neurons. 相似文献
996.
In this paper, a new method on extraction of human skin grid centerlines is proposed. The method introduces the physics concepts of kinetic and potential energy into image processing. Regional energy is calculated. Energy transformation is performed to map the pixels from the grayscale space into energy space. Then, the energy image undergoes a morphological filter to remove noises and spurious minima. The amount of filtering can be manually tuned to get a different result. Subsequently, normal curvature of the energy surface is utilized to identify the principal direction and principal curvatures. The ridge centerlines can be detected at the image locations where the principal direction is perpendicular to the normal vector. The experiment shows that this method is an effective one for the purpose of extracting human skin grid. 相似文献
997.
Electrocardiographic imaging (ECGI) is a developing imaging modality for cardiac electrophysiology and arrhythmias. It reconstructs epicardial potentials, electrograms, and isochrones from electrocardiographic body-surface potentials noninvasively. Current ECGI methodology employs Tikhonov regularization, which imposes constraints on the reconstructed potentials or their derivatives. This approach can sometimes reduce spatial resolution by smoothing the solution. Accuracy depends on a priori knowledge of solution characteristics and determination of an optimal regularization parameter. These properties led us to implement an independent, iterative approach for ECGI—the generalized minimal residual (GMRes) method—which does not apply constraints. GMRes was applied to experimental data during activation/repolarization of normal and infarcted hearts. GMRes reconstructions were compared to Tikhonov reconstructions and to measured gold standards in isolated hearts. Overall, the accuracy of GMRes solutions was similar to Tikhonov regularization. However, in certain cases GMRes recovered localized potential features (e.g., multiple potential minima), which were lost in the Tikhonov solution. Simultaneous use of these two complementary methods in clinical ECGI will ensure reliability and maximal extraction of diagnostic information in the absence of a priori information about a patient's condition.© 2003 Biomedical Engineering Society.
PAC2003: 8719Hh, 8757Gg 相似文献
998.
Murine macrophages were treated with various doses of cyclosporin A (CsA) to enhance the killing of Leishmania major parasites. CsA reduced the rate of infected cells from 75% in non-treated controls to less than 15% with 1 micro g CsA/ml in a dose-dependent manner. The leishmanicidal effect was also observed when CsA was added 48 h after the infection of macrophages. In contrast, FK506, another structural non-related immunosuppressive drug with antiparasitic activities, showed no effect on the ability of macrophages to kill intracellular Leishmania parasites. Since nitric oxide has been identified as a key molecule for the leishmanicidal function of macrophages, we analyzed the role of this molecule. There was no influence on the leishmanicidal effect of CsA when L- N-(1-iminoethyl)lysine, a potent and selective inhibitor of mouse inducible nitric oxide synthase, was added. Furthermore, the presence of the macrophage-inhibiting cytokines interleukin (IL)-10 and IL-13 simultaneously or prior to CsA did not inhibit leishmania killing, while both cytokines completely prevented parasite killing by macrophages activated with gamma interferon and tumor necrosis factor (TNF). CsA was fully active on macrophages from TNF-receptor p55 knockout mice arguing against autocrine activation by TNF. We therefore conclude that the antileishmanial effect of CsA is independent of effector mechanisms employed by macrophage-activating cytokines. 相似文献
999.
Jacek Dabert Agnieszka Badek Maciej Skoracki 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2007,52(3):250-267
Two new genera and three new species of feather mites (Astigmata, Pterolichoidea, Analgoidea) are described from two closely
related species of cockatoos, Cacatua galerita (type host) and C. sulphurea (Psittaciformes, Cacatuidae): Astrolabelichus caudatus gen. nov., sp. nov. (Pterolichidae), Psittophagus lacunosus sp. nov. (Pterolichidae), and Cacatualges microdiscus gen. nov., sp. nov. (Xolalgidae). The presence of the same set of mite species on these two species of parrots points to
a very close affinity of Cacatua sulphurea and C. galerita and gives additional support for the recent hypothesis of the conspecificity of these birds. 相似文献
1000.
Anna Okulewicz Jerzy Okulewicz Joanna Hildebrand Grzegorz Zaleśny 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2007,52(3):292-294
Three male specimens of the eyeworm, Oxyspirura chabaudi, were found during the post mortem examination of one individual of Turdus merula L. (Passeriformes). This is the first record of Turdus merula as a host for O. chabaudi. 相似文献