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61.
Optical coherence tomography derived differences of plaque characteristics in coronary culprit lesions between type 2 diabetic patients with and without acute coronary syndrome 下载免费PDF全文
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Simon J. Sonntag Wei Li Michael Becker Wiebke Kaestner Martin R. Büsen Nikolaus Marx Dorit Merhof Ulrich Steinseifer 《Annals of biomedical engineering》2014,42(5):971-985
Mitral regurgitation (MR) is one of the most frequent valvular heart diseases. To assess MR severity, color Doppler imaging (CDI) is the clinical standard. However, inadequate reliability, poor reproducibility and heavy user-dependence are known limitations. A novel approach combining computational and experimental methods is currently under development aiming to improve the quantification. A flow chamber for a circulatory flow loop was developed. Three different orifices were used to mimic variations of MR. The flow field was recorded simultaneously by a 2D Doppler ultrasound transducer and Particle Image Velocimetry (PIV). Computational Fluid Dynamics (CFD) simulations were conducted using the same geometry and boundary conditions. The resulting computed velocity field was used to simulate synthetic Doppler signals. Comparison between PIV and CFD shows a high level of agreement. The simulated CDI exhibits the same characteristics as the recorded color Doppler images. The feasibility of the proposed combination of experimental and computational methods for the investigation of MR is shown and the numerical methods are successfully validated against the experiments. Furthermore, it is discussed how the approach can be used in the long run as a platform to improve the assessment of MR quantification. 相似文献
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Ian Charest Rogier A. Kievit Taylor W. Schmitz Diana Deca Nikolaus Kriegeskorte 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(40):14565-14570
The unique way in which each of us perceives the world must arise from our brain representations. If brain imaging could reveal an individual’s unique mental representation, it could help us understand the biological substrate of our individual experiential worlds in mental health and disease. However, imaging studies of object vision have focused on commonalities between individuals rather than individual differences and on category averages rather than representations of particular objects. Here we investigate the individually unique component of brain representations of particular objects with functional MRI (fMRI). Subjects were presented with unfamiliar and personally meaningful object images while we measured their brain activity on two separate days. We characterized the representational geometry by the dissimilarity matrix of activity patterns elicited by particular object images. The representational geometry remained stable across scanning days and was unique in each individual in early visual cortex and human inferior temporal cortex (hIT). The hIT representation predicted perceived similarity as reflected in dissimilarity judgments. Importantly, hIT predicted the individually unique component of the judgments when the objects were personally meaningful. Our results suggest that hIT brain representational idiosyncrasies accessible to fMRI are expressed in an individual''s perceptual judgments. The unique way each of us perceives the world thus might reflect the individually unique representation in high-level visual areas.Everyone’s perception of the world is unique. Psychologists and psychotherapists, using methods including questionnaires and free association, have long attempted to peer into an individual’s subjective experiential world. The unique aspects of our experience coexist with a shared experiential component. We can all recognize the objects that surround us and name them in a common language. Consistent with this shared component of experience, there is evidence that visual stimuli are processed similarly in the brains of different individuals (1). However, the unique way in which each of us perceives an object also must arise from brain activity. Is there an individually unique component to our brain representations?Unidimensional aspects of subjective visual percepts, ranging from estimates of object size, color, vividness, and emotional valence, have separately been found to correlate with interindividual variation in both univariate regional-average activation and cortical anatomy (2, 3). However, it remains unclear how a person’s multidimensional subjective percept reflects the multivariate brain-activity pattern that represents a particular object.Functional magnetic resonance imaging (fMRI) studies of object vision have focused largely on commonalities among subjects and category averages across particular stimuli. These studies have revealed regions in human inferior temporal cortex (hIT) that preferentially respond to specific categories (4–9) as well as widely distributed category information (10). More recently, similarity analyses of response patterns to particular stimulus images have revealed exemplar-specific representations (11–14), clustering of response patterns by natural categories (15–17), and reinstatement of neural representations during memory recall (18, 19). These prior studies either tacitly assumed similar representations across individuals or explicitly demonstrated commonalities between individuals and even between species (14, 20–29).Previous studies have shown that the hIT representation has a semantic component (23) and is reflected in perception at the level of group averages (30). Here we tested the hypothesis that an individual’s hIT representation predicts idiosyncrasies in his or her perception of natural objects. Because of hIT’s reciprocal connections to the memory regions of the medial temporal lobe (31), we further predicted that personally meaningful objects elicit individually unique mnemonic associations and are more distinctly represented in each individual.We presented familiar and unfamiliar object images to subjects during fMRI and investigated whether early visual cortex (EVC) and hIT exhibit individually unique representations. We characterized the representational geometry of each region by the dissimilarity matrix of activity patterns elicited by particular object images. This matrix is called the “representational dissimilarity matrix” (RDM) (16). To address whether the detailed representational geometries are reflected in behavior, we tested whether individual idiosyncrasies in similarity judgments can be predicted on the basis of a subject’s brain RDM. 相似文献
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Objectives: The aim of the present prospective clinical study was to evaluate the match between the positions and axes of the virtually planned and the placed implants using laboratory‐based surgical guides generated from cone beam computed tomography (CBCT). Materials and methods: A total of 132 implants were placed with the aid of 3D‐based transfer templates in 52 consecutive partially edentulous patients between April 2008 and March 2010. After individual adaptation of the scan templates and CBCT scanning, the acquired data for virtual implant planning and simulation were processed using the med3D software program. After finalizing the virtual placement of the implants the radiographic templates were converted into operative guides containing titanium sleeves for cavity preparation. Preoperative planning was merged with postoperative CBCT data to identify linear and angular deviations between virtually planned and placed implants. Results: Compared with the planned implants the installed implants showed linear deviations in the median at the neck and apex of 0.27 mm (range 0.01–0.97 mm), and of 0.46 mm (range 0.03–1.38 mm), respectively. The angle deviation was 1.84° in median, with a range of 0.07–6.26°. The extent of deviation depends on the size of the tooth gap and the distribution of the remaining teeth. Conclusion: The results of this study suggested that laboratory‐fabricated surgical guides using CBCT data may be reliable in implant placement under prosthodontic considerations in partial edentulism. To cite this article: Behneke A, Burwinkel M, Knierim K, Behneke N. Accuracy assessment of cone beam computed tomography‐derived laboratory‐based surgical templates on partially edentulous patients.Clin. Oral Impl. Res. 23 , 2012; 137–143. doi: 10.1111/j.1600‐0501.2011.02176.x 相似文献
67.
Nevzorova YA Bangen JM Hu W Haas U Weiskirchen R Gassler N Huss S Tacke F Sicinski P Trautwein C Liedtke C 《Hepatology (Baltimore, Md.)》2012,56(3):1140-1149
Liver fibrogenesis is associated with the transition of quiescent hepatocytes and hepatic stellate cells (HSCs) into the cell cycle. Exit from quiescence is controlled by E-type cyclins (cyclin E1 [CcnE1] and cyclin E2 [CcnE2]). Thus, the aim of the current study was to investigate the contribution of E-type cyclins for liver fibrosis in man and mice. Expression of CcnE1, but not of its homolog, CcnE2, was induced in fibrotic and cirrhotic livers from human patients with different etiologies and in murine wild-type (WT) livers after periodical administration of the profibrotic toxin, CCl(4) . To further evaluate the potential function of E-type cyclins for liver fibrogenesis, we repetitively treated constitutive CcnE1(-/-) and CcnE2(-/-) knock-out mice with CCl(4) to induce liver fibrosis. Interestingly, CcnE1(-/-) mice were protected against CCl(4) -mediated liver fibrogenesis, as evidenced by reduced collagen type I α1 expression and the lack of septum formation. In contrast, CcnE2(-/-) mice showed accelerated fibrogenesis after CCl(4) treatment. We isolated primary HSCs from WT, CcnE1(-/-) , and CcnE2(-/-) mice and analyzed their activation, proliferation, and survival in vitro. CcnE1 expression in WT HSCs was maximal when they started to proliferate, but decreased after the cells transdifferentiated into myofibroblasts. CcnE1(-/-) HSCs showed dramatically impaired survival, cell-cycle arrest, and strongly reduced expression of alpha smooth muscle actin, indicating deficient HSC activation. In contrast, CcnE2-deficient HSCs expressed an elevated level of CcnE1 and showed enhanced cell-cycle activity and proliferation, compared to WT cells. Conclusions: CcnE1 and CcnE2 have antagonistic roles in liver fibrosis. CcnE1 is indispensable for the activation, proliferation, and survival of HSCs and thus promotes the synthesis of extracellular matrix and liver fibrogenesis. (HEPATOLOGY 2012;56:1140-1149). 相似文献
68.
Gerhard Hildebrandt Martin Nikolaus Stienen Werner Surbeck 《Acta neurochirurgica》2013,155(9):1787-1799
Background
The rise of a neurosurgical subspecialisation in general surgery was strongly influenced by some key surgeons. In the German-speaking regions of Europe, Ernst von Bergmann, Emil Theodor Kocher and Rudolf Ulrich Krönlein have to be especially highlighted.Methods
This article describes their contributions to the neurosurgical field and their personal interactions. For this, the numerous publications on cranial neurosurgery of von Bergmann were reviewed. They are presented in chronological order. Kocher’s and Krönlein’s contributions to early neurosurgery have been valued recently by the authors and are briefly summarized.Results
All three developed early interest in the neurosurgical field and conducted clinical and experimental research at the turn of the twentieth century. It becomes evident that von Bergmann, Kocher and Krönlein provided a basis for a transnational neurosurgical school.Conclusion
This triumvirate developed a common neurosurgical concept that was grounded in the physiological experiments and scientific evidence. 相似文献69.
Kormann MS Hector A Marcos V Mays LE Kappler M Illig T Klopp N Zeilinger S Carevic M Rieber N Eickmeier O Zielen S Gaggar A Moepps B Griese M Hartl D 《The European respiratory journal》2012,39(6):1385-1390
Cystic fibrosis (CF) lung disease severity is largely independent on the CF transmembrane conductance regulator (CFTR) genotype, indicating the contribution of genetic modifiers. The chemokine receptors CXCR1 and CXCR2 have been found to play essential roles in the pathogenesis of CF lung disease. Here, we determine whether genetic variation of CXCR1 and CXCR2 influences CF lung disease severity. Genomic DNA of CF patients in Germany (n = 442) was analysed for common variations in CXCR1 and CXCR2 using a single-nucleotide polymorphism (SNP) tagging approach. Associations of CXCR1 and CXCR2 SNPs and haplotypes with CF lung disease severity, CXCR1 and CXCR2 expression, and neutrophil effector functions were assessed. Four SNPs in CXCR1 and three in CXCR2 strongly correlated with age-adjusted lung function in CF patients. SNPs comprising haplotypes CXCR1_Ha and CXCR2_Ha were in high linkage disequilibrium and patients heterozygous for the CXCR1-2 haplotype cluster (CXCR1-2_Ha) had lower lung function compared with patients with homozygous wild-type alleles (forced expiratory volume in 1 s ≤ 70% predicted, OR 7.24; p = 2.30 × 10(-5)). CF patients carrying CXCR1-2_Ha showed decreased CXCR1 combined with increased CXCR2 mRNA and protein expression, and displayed disturbed antibacterial effector functions. CXCR1 and CXCR2 genotypes modulate lung function and antibacterial host defence in CF lung disease. 相似文献
70.
Lukas A Kilian R Hay B Muche R von Arnim CA Otto M Riepe M Jamour M Denkinger MD Nikolaus T 《Zeitschrift für Gerontologie und Geriatrie》2012,45(4):298-309