全文获取类型
收费全文 | 2003篇 |
免费 | 181篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 14篇 |
儿科学 | 46篇 |
妇产科学 | 42篇 |
基础医学 | 322篇 |
口腔科学 | 21篇 |
临床医学 | 191篇 |
内科学 | 536篇 |
皮肤病学 | 97篇 |
神经病学 | 114篇 |
特种医学 | 53篇 |
外科学 | 391篇 |
综合类 | 8篇 |
一般理论 | 1篇 |
预防医学 | 57篇 |
眼科学 | 14篇 |
药学 | 122篇 |
中国医学 | 10篇 |
肿瘤学 | 160篇 |
出版年
2023年 | 16篇 |
2022年 | 103篇 |
2021年 | 131篇 |
2020年 | 56篇 |
2019年 | 71篇 |
2018年 | 93篇 |
2017年 | 66篇 |
2016年 | 86篇 |
2015年 | 69篇 |
2014年 | 104篇 |
2013年 | 91篇 |
2012年 | 126篇 |
2011年 | 147篇 |
2010年 | 77篇 |
2009年 | 66篇 |
2008年 | 113篇 |
2007年 | 124篇 |
2006年 | 112篇 |
2005年 | 116篇 |
2004年 | 85篇 |
2003年 | 67篇 |
2002年 | 60篇 |
2001年 | 17篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 3篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 3篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1969年 | 4篇 |
1968年 | 7篇 |
1967年 | 7篇 |
1934年 | 2篇 |
1933年 | 2篇 |
排序方式: 共有2199条查询结果,搜索用时 15 毫秒
41.
Andressa Kelly Alves Ferreira Srgio Henrique Gonalves de Carvalho Ana Flvia Granville-Garcia Dmitry Jos de Santana Sarmento Gustavo Gomes Agripino Mauro Henrique Nogueira Guimares de Abreu Maria Cecília Freire de Melo Arnaldo de Frana Caldas Jr Gustavo Pina Godoy 《Medicina oral, patología oral y cirugía bucal》2021,26(3):e387
Background This study aimed to evaluate sociodemographic and clinical factors influencing overall survival (OS) in patients with oral squamous cell carcinoma (OSCC). Material and Methods Medical charts of 547 patients with OSCC from a public hospital in northeastern Brazil seen between 1999 and 2013 were evaluated. Survival analysis was performed using the Kaplan-Meier method. The influence of age, sex, ethnicity, clinical stage, anatomical location, type of treatment, and comorbidities on the patients’ prognosis was evaluated. Cox proportional hazards regression model was used to identify independent prognostic factors. Results The 5-year OS was 39%. Multivariate analysis showed that age < 40 years (HR = 2.20; 95%CI: 1.02-4.72) and a single treatment modality (HR = 1.91; 95%CI: 1.37-2.67) were associated with a poor prognosis, while early clinical stage resulted in better outcomes (HR = 0.38; 95%CI: 0.25-0.58). Conclusions OSCC patients in advanced clinical stages, diagnosed at a younger age, and submitted to a single therapeutic modality have a poorer prognosis. Key words:Head and neck cancer, oral cancer, oral squamous cell carcinoma, survival, prognosis. 相似文献
42.
43.
44.
Proteins of the S100 family regulate the oligomerization of p53 tumor suppressor 总被引:14,自引:0,他引:14
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Fernandez-Fernandez MR Veprintsev DB Fersht AR 《Proceedings of the National Academy of Sciences of the United States of America》2005,102(13):4735-4740
S100B protein is elevated in the brains of patients with early stages of Alzheimer's disease and Down's syndrome. S100A4 is correlated with the development of metastasis. Both proteins bind to p53 tumor suppressor. We found that both S100B and S100A4 bind to the tetramerization domain of p53 (residues 325-355) only when exposed in lower oligomerization states and so they disrupt the tetramerization of p53. In addition, S100B binds to the negative regulatory and nuclear localization domains, which results in a very tight binding to p53 protein sequences that exposed the tetramerization domain in their C terminus. Because the trafficking of p53 depends on its oligomerization state, we suggest that S100B and S100A4 could regulate the subcellular localization of p53. But, the differences in the way these proteins bind to p53 could result in S100B and S1004 having different effects on p53 function in cell-cycle control. 相似文献
45.
Tatyana V. Lisovskaya Galina B. Mal’gina Tatyana A. Perepletina Valentina V. Medvedeva Dmitry E. Kireev German A. Shipulin 《Gynecological endocrinology》2015,31(10):18-21
AbstractAim: The purpose of the study is to detect endometrial pathology in individuals with blood-borne infections (hepatitis C virus [HCV] and HIV) and to assess the impact of quality of the endometrium on the efficiency of assisted reproductive technologies (ART).Materials and methods of research: The study involved 56 women of reproductive age, 33 women with HCV, 22 with HIV infection (stages 3 and 4A) and 1 patient with co-infection of HCV and HIV, which was excluded from the further study. Ultrasound investigation of the small pelvic organs, hysteroscopy with biopsy of the mucosa of the uterine cavity, histological examination of the endometrium, determination of HCV RNA and HIV RNA in serum and endometrial tissue by PCR method were conducted.Results: Ultrasound and histological studies of the endometrium revealed a high incidence of development of hyperplastic and inflammatory processes of the endometrium in women with HCV (86% and 100%) and HIV (51% and 99%). When molecular biological examination of endometrial tissue of these patients was performed with the use of a set of reagents “AmpliSens HCV/HBV/HIV-FL” produced by Federal Budgetary Institution of Science (FBUN) Central Research Institute of Epidemiology of Rospotrebnadzor of Russia, HCV was detected in 16.7% and HIV in 14.3% of cases. In 5% of patients with HCV infection and 7% with HIV, pathogens were detected in the endometrium under the non-detectable viral load in the blood plasma. Lower effectiveness of IVF in women with HIV and HCV is defined compared to the women without blood-borne infections.Conclusion: Detected HIV and HCV replications in the endometrium is the likely cause of hyperplastic and inflammatory processes of the endometrium leading to reduced efficiency of the ART programs in patients with chronic hepatitis C and HIV. 相似文献
46.
You-Sheng Li Naoki Kikugawa Dmitry A. Sokolov Fabian Jerzembeck Alexandra S. Gibbs Yoshiteru Maeno Clifford W. Hicks Jrg Schmalian Michael Nicklas Andrew P. Mackenzie 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(10)
A key question regarding the unconventional superconductivity of remains whether the order parameter is single- or two-component. Under a hypothesis of two-component superconductivity, uniaxial pressure is expected to lift their degeneracy, resulting in a split transition. The most direct and fundamental probe of a split transition is heat capacity. Here, we report measurement of heat capacity of samples subject to large and highly homogeneous uniaxial pressure. We place an upper limit on the heat-capacity signature of any second transition of a few percent of that of the primary superconducting transition. The normalized jump in heat capacity, , grows smoothly as a function of uniaxial pressure, favoring order parameters which are allowed to maximize in the same part of the Brillouin zone as the well-studied van Hove singularity. Thanks to the high precision of our measurements, these findings place stringent constraints on theories of the superconductivity of .Obtaining a full understanding of the superconductivity of is a core challenge for condensed-matter physics. Since soon after its discovery over a quarter of a century ago (1), the superconducting order parameter of has been known to be unconventional (2, 3) and to condense from a well-understood and fairly simple quasi-two-dimensional Fermi liquid metallic state (4–7). Given the profound advances in theoretical techniques in recent decades a full understanding of its superconductivity is an important, and attainable, challenge for the field. The form of the wave-vector-dependent susceptibility of leads to the prediction of a rich superconducting phase diagram in weak-coupling calculations which aim to perform a bias-free estimate of the condensation energies of different order parameters. A notable feature of the results is how close a number of different odd- and even-parity solutions are seen to be in energy (8–10). On the one hand, this emphasizes the potential of as a test-bed material on which to refine the predictive capabilities of modern theories of unconventional superconductivity (11). On the other hand, realizing this potential will likely first require a conclusive experimental determination of which of the many possible order parameters wins out in the real material. This is a particularly exciting stage of the quest to complete this empirical determination, for reasons that we will now outline.For over 20 y the large majority of attention was paid to odd-parity order parameter candidates for (12), because of NMR measurements of spin susceptibility in the superconducting state that seemed to be inconsistent with any even-parity order parameter (13). However, thanks to the discovery of a systematic error in the original NMR measurements (14, 15), that situation has now been more or less completely reversed. Taking into account the most recent measurements of the magnetic field dependence of the spin susceptibility (16), it seems clear that the order parameter must be even-parity or at least dominated by an even-parity component. The spin susceptibility results would be most easily describable in terms of a single-component, likely -wave, order parameter, but recent thermodynamic evidence from ultrasound experiments is most straightforwardly interpreted in terms of an order parameter with two degenerate components (17, 18). Such order parameters do not of necessity break time-reversal symmetry, but they can, if the two degenerates have the appropriate phase relationship. In the context it is significant that long-standing muon-spin relaxation (SR) (19, 20) and magneto-optic Kerr rotation measurements (21) have indicated time-reversal symmetry breaking in the superconducting state.To investigate any order parameter with two degenerate components, whether or not it breaks time-reversal symmetry, uniaxial pressure is a powerful probe because it can split the degeneracy, creating a split superconducting phase transition (22). In a significant experimental advance, the muon-spin relaxation experiments have recently been extended to high uniaxial pressures (23). In line with naive expectation, the temperature at which time-reversal symmetry is broken () splits from the main superconducting transition (), with remaining nearly pressure-independent while increases under the application of the pressure. However, there has been a long-standing question about whether the Kerr and muon signals correspond to bulk thermodynamic transitions, so it is highly desirable to compare the new muon-spin relaxation data with those from a bulk thermodynamic probe. In this context, it is natural to look at heat capacity, because it has an intrinsic sensitivity to transitions within the superconducting state, as is well known from work on (24, 25). 相似文献
47.
Olesya G. Bernikova Ksenia A. Sedova Natalia V. Arteyeva Aleksey O. Ovechkin Sergey N. Kharin Dmitry N. Shmakov Jan E. Azarov 《Journal of electrocardiology》2018,51(3):542-548
Background
Aim of the study was to find out which myocardial repolarization parameters predict reperfusion ventricular tachycardia and fibrillation (VT/VF) and determine how these parameters express in ECG.Methods
Coronary occlusion and reperfusion (30/30 min) was induced in 24 cats. Local activation and end of repolarization times (RT) were measured in 88 intramyocardial leads. Computer simulations of precordial electrograms were performed.Results
Reperfusion VT/VF developed in 10 animals. Arrhythmia-susceptible animals had longer RTs in perfused areas [183(177;202) vs 154(140;170) ms in susceptible and resistant animals, respectively, P < 0.05]. In logistic regression analysis, VT/VFs were associated with prolonged RTs in the perfused area (OR 1.068; 95% CI 1.012–1.128; P = 0.017). Simulations demonstrated that prolonged repolarization in the perfused/border zone caused precordial terminal T-wave inversion.Conclusions
The reperfusion VT/VFs were independently predicted by the longer RT in the perfused zone, which was reflected in the terminal negative phase of the electrocardiographic T-wave. 相似文献48.
49.
Pulkit Rastogi Prashant Sharma Neelam Varma Dmitry Sukhachev Naveen Kaushal Ishwar Bihana Man Updesh Singh Sachdeva Shano Naseem Pankaj Malhotra 《Indian journal of hematology & blood transfusion》2018,34(4):623-631
Automated blood counts revealing lymphocytosis necessitate smear reviews. Even expert morphological evaluation may however, fail to differentiate a benign-versus-malignant etiology without further testing. Automated analyser-derived quantitative data on leukocyte cell populations remain undertested for distinguishing such etiologies. Instrument manufacturers claim that if successful, they may be used to generate software flags that help under-resourced laboratories better triage hemogram specimens requiring further testing. We tested the diagnostic accuracy of volume-conductivity-scatter (VCS) indices together with complete blood count (CBC) parameters in such scenarios. We compared LH780-derived (Beckman Coulter, FL, USA) CBC + VCS parameters from patients with clonal lymphoproliferations (n = 42, including 30 chronic lymphocytic leukemia cases) versus 83 controls with absolute or relative lymphocytosis (derivation cohort). Diagnostic performances of 11 logistic regression equations derived were subsequently evaluated on two specific validation cohorts (n = 130 and n = 1465). Clonal lymphocytoses showed significantly lower hemoglobin and higher leukocyte counts but similar lymphocyte percentages (LY %) vis-à-vis controls. The most significant, albeit overlapping predictor of clonality was the absolute lymphocyte count, LY# (47.8 ± 48.4 × 109/L vs. 2.9 ± 1.4 × 109/L in clonal vs. benign cases). In eleven logistic regression equations constructed using four combinatorial approaches, only the models with LY# (highest sensitivity/specificity of 99.3%/100%) and the lymphocytic VCS parameters alone (highest sensitivity/specificity of 76.2%/90.2%) performed consistently in both validation cohorts. Lymphocytic VCS parameters were moderately successful in distinguishing benign-versus-malignant lymphocytes. Other approaches of CBC-plus-VCS parameters did not sustain their initial excellent performances in the validation cohorts, highlighting a need for careful appraisal and better standardization of automated cellular analysis technologies. 相似文献
50.
A lipid bilayer containing a ternary mixture of low- and high-melting lipids and cholesterol (Chol) can give rise to domain formation, referred to as lipid rafts. Low-frequency Raman spectroscopy at reduced temperatures allows detection of normal membrane mechanical vibrations. In this work, Raman spectra were obtained in the spectral range between 5 and 90 cm−1 for bilayers prepared from dioleoyl-glycero-phosphocholine (DOPC), dipalmitoyl-glycero-phosphocholine (DPPC) and Chol. A narrow peak detected between 13 and 16 cm−1 was attributed to the vibrational eigenmode of a lipid monolayer (a leaflet). For the equimolar DOPC/DPPC ratio, the Chol concentration dependence for the peak position, width and amplitude may be divided into three distinct ranges: below 9 mol%, the intermediate range between 9 mol% and 38 mol%, and above 38 mol%. In the intermediate range the peak position attains its minimum, and the peak width drops approximately by a factor of two as compared with the Chol-free bilayers. Meanwhile, this range is known for raft formation in a fluid state. The obtained results may be interpreted as evidence that bilayer structures in the raft-containing fluid state may be frozen at low temperatures. The drop of peak width indicates that at the spatial scale of the experiment (∼2.5 nm) the intermolecular bilayer structure with raft formation becomes more homogeneous and more cohesive.Upon lipid raft formation, the Raman peak corresponding to monolayer normal mechanical vibrations drops remarkably in position and width. 相似文献