全文获取类型
收费全文 | 931633篇 |
免费 | 66524篇 |
国内免费 | 1347篇 |
专业分类
耳鼻咽喉 | 12969篇 |
儿科学 | 24363篇 |
妇产科学 | 23232篇 |
基础医学 | 132883篇 |
口腔科学 | 28246篇 |
临床医学 | 80534篇 |
内科学 | 183279篇 |
皮肤病学 | 19229篇 |
神经病学 | 72171篇 |
特种医学 | 36806篇 |
外国民族医学 | 79篇 |
外科学 | 152072篇 |
综合类 | 18043篇 |
现状与发展 | 1篇 |
一般理论 | 234篇 |
预防医学 | 61742篇 |
眼科学 | 21308篇 |
药学 | 72522篇 |
3篇 | |
中国医学 | 2162篇 |
肿瘤学 | 57626篇 |
出版年
2018年 | 8962篇 |
2017年 | 7025篇 |
2016年 | 7758篇 |
2015年 | 8856篇 |
2014年 | 11980篇 |
2013年 | 17490篇 |
2012年 | 24073篇 |
2011年 | 25025篇 |
2010年 | 14797篇 |
2009年 | 14261篇 |
2008年 | 24590篇 |
2007年 | 25679篇 |
2006年 | 26470篇 |
2005年 | 25416篇 |
2004年 | 24550篇 |
2003年 | 23595篇 |
2002年 | 23141篇 |
2001年 | 54724篇 |
2000年 | 56542篇 |
1999年 | 46947篇 |
1998年 | 10730篇 |
1997年 | 9464篇 |
1996年 | 9592篇 |
1995年 | 8926篇 |
1994年 | 8278篇 |
1993年 | 7593篇 |
1992年 | 35487篇 |
1991年 | 33911篇 |
1990年 | 32734篇 |
1989年 | 31869篇 |
1988年 | 28991篇 |
1987年 | 28249篇 |
1986年 | 26288篇 |
1985年 | 25144篇 |
1984年 | 17832篇 |
1983年 | 15141篇 |
1982年 | 7795篇 |
1981年 | 6771篇 |
1979年 | 15781篇 |
1978年 | 10598篇 |
1977年 | 9052篇 |
1976年 | 7871篇 |
1975年 | 8628篇 |
1974年 | 10466篇 |
1973年 | 9858篇 |
1972年 | 9357篇 |
1971年 | 8852篇 |
1970年 | 8426篇 |
1969年 | 7923篇 |
1968年 | 7200篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Testing association of rare genetic variants with resistance to three common antiseizure medications
Stefan Wolking Claudia Moreau Anne T. Nies Elke Schaeffeler Mark McCormack Pauls Auce Andreja Avbersek Felicitas Becker Martin Krenn Rikke S. Møller Marina Nikanorova Yvonne G. Weber Sarah Weckhuysen Gianpiero L. Cavalleri Norman Delanty Chantal Depondt Michael R. Johnson Bobby P.C. Koeleman Wolfram S. Kunz Anthony G. Marson Josemir W. Sander Graeme J. Sills Pasquale Striano Federico Zara Fritz Zimprich Matthias Schwab Roland Krause Sanjay M. Sisodiya Patrick Cossette Simon L. Girard Holger Lerche EpiPGX Consortium 《Epilepsia》2020,61(4):657-666
22.
Kristen McAlpine Rodney H. Breau Dawn Stacey Christopher Knee Michael A.S. Jewett Philippe D. Violette Patrick O. Richard Ilias Cagiannos Christopher Morash Luke T. Lavalle 《Canadian Urological Association journal》2020,14(12):385
IntroductionShared decision-making incorporates patients’ values and preferences to achieve high-quality decisions. The objective of this study was to develop an acceptable patient decision aid to facilitate shared decision-making for the management of small renal masses (SRMs).MethodsThe International Patient Decision Aids Standards were used to guide an evidence-based development process. Management options included active surveillance, thermal ablation, partial nephrectomy, and radical nephrectomy. A literature review was performed to provide incidence rates for outcomes of each option. Once a prototype was complete, alpha-testing was performed using a 10-question survey to assess acceptability with patients, patient advocates, urologists, and methodological experts. The primary outcome was acceptability of the decision aid.ResultsA novel patient decision aid was created to facilitate shared decision-making for the management of SRMs. Acceptability testing was performed with 20 patients, 10 urologists, two patient advocates, and one methodological expert. Responders indicated the decision aid was appropriate in length (82%, 27/33), well-balanced (82%, 27/33), and had language that was easy to follow (94%, 31/33). All patient responders felt the decision aid would have been helpful during their consultation and would recommend the decision aid for future patients (100%, 20/20). Most urologists reported they intend to use the decision aid (90%, 9/10).ConclusionsA novel patient decision aid was created to facilitate shared decision-making for management of SRMs. This clinical tool was acceptable with patients, patient advocates, and urologists and is freely available at: https://decisionaid.ohri.ca/decaids.html. 相似文献
23.
The hippocampal system contains neural populations that encode an animal's position and velocity as it navigates through space. Here, we show that such populations can embed two codes within their spike trains: a firing rate code ( R ) conveyed by within‐cell spike intervals, and a co‐firing rate code () conveyed by between‐cell spike intervals. These two codes behave as conjugates of one another, obeying an analog of the uncertainty principle from physics: information conveyed in R comes at the expense of information in , and vice versa. An exception to this trade‐off occurs when spike trains encode a pair of conjugate variables, such as position and velocity, which do not compete for capacity across R and . To illustrate this, we describe two biologically inspired methods for decoding R and , referred to as sigma and sigma‐chi decoding, respectively. Simulations of head direction and grid cells show that if firing rates are tuned for position (but not velocity), then position is recovered by sigma decoding, whereas velocity is recovered by sigma‐chi decoding. Conversely, simulations of oscillatory interference among theta‐modulated “speed cells” show that if co‐firing rates are tuned for position (but not velocity), then position is recovered by sigma‐chi decoding, whereas velocity is recovered by sigma decoding. Between these two extremes, information about both variables can be distributed across both channels, and partially recovered by both decoders. These results suggest that populations with different spatial and temporal tuning properties—such as speed versus grid cells—might not encode different information, but rather, distribute similar information about position and velocity in different ways across R and . Such conjugate coding of position and velocity may influence how hippocampal populations are interconnected to form functional circuits, and how biological neurons integrate their inputs to decode information from firing rates and spike correlations. 相似文献
24.
R.J. van de Peppel M.T. van der Beek L.G. Visser M.G.J. de Boer J. Wallinga 《International journal of antimicrobial agents》2019,53(3):284-293
Objectives
Triazole resistance in Aspergillus spp. is emerging and complicates prophylaxis and treatment of invasive aspergillosis (IA) worldwide. New polymerase chain reaction (PCR) tests on broncho-alveolar lavage (BAL) fluid allow for detection of triazole resistance at a genetic level, which has opened up new possibilities for targeted therapy. In the absence of clinical trials, a modelling study delivers estimates of the added value of resistance detection with PCR, and which empiric therapy would be optimal when local resistance rates are known.Design
A decision-analytic modelling study was performed based on epidemiological data of IA, extended with estimated dynamics of resistance rates and treatment effectiveness. Six clinical strategies were compared that differ in use of PCR diagnostics (used vs not used) and in empiric therapeutic choice in case of unknown triazole susceptibility: voriconazole, liposomal amphotericin B (LAmB) or both. Outcome measures were proportion of correct treatment, survival and serious adverse events.Results
Implementing aspergillus PCR tests was projected to result in residual treatment-susceptibility mismatches of <5% for a triazole resistance rate up to 20% (using voriconazole). Empiric LAmB outperformed voriconazole at resistance rates >5–20%, depending on PCR use and estimated survival benefits of voriconazole over LAmB. Combination therapy of voriconazole and LAmB performed best at all resistance rates, but the advantage over the other strategies should be weighed against the expected increased number of drug-related serious adverse events. The advantage of combination therapy over LAmB monotherapy became smaller at higher triazole resistance rates.Conclusions
Introduction of current aspergillus PCR tests on BAL fluid is an effective way to increase the proportion of patients that receive targeted therapy for IA. The results indicate that close monitoring of background resistance rates and adverse drug events are important to attain the potential benefits of LAmB. The choice of strategy ultimately depends on the probability of triazole resistance, the availability of PCR and individual patient characteristics. 相似文献25.
26.
Serge A. Mitelman Monte S. Buchsbaum Bradley T. Christian Brian M. Merrill Bradley R. Buchsbaum Jogeshwar Mukherjee 《The world journal of biological psychiatry》2020,21(5):368-382
AbstractObjectives: Overlapping decreases in extrastriatal dopamine D2/D3-receptor availability and glucose metabolism have been reported in subjects with schizophrenia. It remains unknown whether these findings are physiologically related or coincidental.Methods: To ascertain this, we used two consecutive 18F-fluorodeoxyglucose and 18F-fallypride positron emission tomography scans in 19 healthy and 25 unmedicated schizophrenia subjects. Matrices of correlations between 18F-fluorodeoxyglucose uptake and 18F-fallypride binding in voxels at the same xyz location and AFNI-generated regions of interest were evaluated in both diagnostic groups.Results: 18F-fluorodeoxyglucose uptake and 18F-fallypride binding potential were predominantly positively correlated across the striatal and extrastriatal grey matter in both healthy and schizophrenia subjects. In comparison to healthy subjects, significantly weaker correlations in subjects with schizophrenia were confirmed in the right cingulate gyrus and thalamus, including the mediodorsal, lateral dorsal, anterior, and midline nuclei. Schizophrenia subjects showed decreased D2/D3-receptor availability in the hypothalamus, mamillary bodies, thalamus and several thalamic nuclei, and increased glucose uptake in three lobules of the cerebellar vermis.Conclusions: Dopaminergic system may be involved in modulation of grey matter metabolism and neurometabolic coupling in both healthy human brain and psychopathology. Hyperdopaminergic state in untreated schizophrenia may at least partly account for the corresponding decreases in grey matter metabolism. 相似文献
27.
F. Fruzzetti G. Palla A. Sbrana T. Simoncini M. R. Sessa 《Gynecological endocrinology》2020,36(10):938-940
AbstractObjective: To understand the origin of extremely high gonadotropin levels in a perimenopausal woman.Methods: A 52-year-old woman with a 2?months of amenorrhea followed spontaneous menstrual cycles recovery was referred to our outpatient clinic with elevated follicle-stimulating hormone (FSH, 483 mUI/ml), luteinizing hormone (LH, 475 mUI/ml) and prolactin (PRL, 173?ng/ml). She was known to take levosulpiride. The gonadotropin levels did not fit with the clinical features.Results: A gonadotroph tumor was ruled out. Further analysis confirmed constantly high FSH, LH and PRL levels. The measurements were repeated using different analytical platforms with different results. After serial dilutions, nonlinearity was present suggesting an immunoassay interference. After post-polyethylene glycol recovery, hormone levels appeared in the normal range. Anti-goat antibodies were recognized in the serum of the patient.Conclusions: This case report shows a case of falsely abnormal high gonadotropin and PRL levels in a woman during menopause transition. In the clinical practice the evaluation of gonadotropin profile is not recommended at this age, but the abnormal levels stimulated further evaluation. An interference in the assay due to anti-goat antibodies resulted in abnormally high level of FSH and LH. A strict collaboration between clinicians and the laboratory is needed, when laboratory findings do not correspond to clinical findings. 相似文献
28.
C.A.P.F. Alves U. Lbel J.S. Martin-Saavedra S. Toescu M.H. Tsunemi S.R. Teixeira K. Mankad D. Hargrave T.S. Jacques C. da Costa Leite F.G. Gonalves A. Vossough F. D'Arco 《AJNR. American journal of neuroradiology》2021,42(5):961
BACKGROUND AND PURPOSE:Primary posterior fossa tumors comprise a large group of neoplasias with variable aggressiveness and short and long-term outcomes. This study aimed to validate the clinical usefulness of a radiologic decision flow chart based on previously published neuroradiologic knowledge for the diagnosis of posterior fossa tumors in children.MATERIALS AND METHODS:A retrospective study was conducted (from January 2013 to October 2019) at 2 pediatric referral centers, Children''s Hospital of Philadelphia, United States, and Great Ormond Street Hospital, United Kingdom. Inclusion criteria were younger than 18 years of age and histologically and molecularly confirmed posterior fossa tumors. Subjects with no available preoperative MR imaging and tumors located primarily in the brain stem were excluded. Imaging characteristics of the tumors were evaluated following a predesigned, step-by-step flow chart. Agreement between readers was tested with the Cohen κ, and each diagnosis was analyzed for accuracy.RESULTS:A total of 148 cases were included, with a median age of 3.4 years (interquartile range, 2.1–6.1 years), and a male/female ratio of 1.24. The predesigned flow chart facilitated identification of pilocytic astrocytoma, ependymoma, and medulloblastoma sonic hedgehog tumors with high sensitivity and specificity. On the basis of the results, the flow chart was adjusted so that it would also be able to better discriminate atypical teratoid/rhabdoid tumors and medulloblastoma groups 3 or 4 (sensitivity = 75%–79%; specificity = 92%–99%). Moreover, our adjusted flow chart was useful in ruling out ependymoma, pilocytic astrocytomas, and medulloblastoma sonic hedgehog tumors.CONCLUSIONS:The modified flow chart offers a structured tool to aid in the adjunct diagnosis of pediatric posterior fossa tumors. Our results also establish a useful starting point for prospective clinical studies and for the development of automated algorithms, which may provide precise and adequate diagnostic tools for these tumors in clinical practice.In the past 10 years, there has been an exponential increase in knowledge of the molecular characteristics of pediatric brain tumors, which was only partially incorporated in the 2016 World Health Organization Classification of Tumors of the Central Nervous System.1 The main update in the 2016 Classification was the introduction of the molecular profile of a tumor as an important factor for predicting different biologic behaviors of entities which, on histology, look very similar or even indistinguishable.2 A typical example is the 4 main groups of medulloblastoma: wingless (WNT), sonic hedgehog (SHH) with or without the p53 mutation, group 3, and group 4. Although they may appear similar on microscopy, these categories have distinct molecular profiles, epidemiology, prognosis, and embryologic origin.3Subsequent to the publication of the 2016 World Health Organization Classification, further studies have identified even more molecular subgroups of medulloblastoma with possible prognostic implications4 and also at least 3 new molecular subgroups of atypical teratoid/rhabdoid tumor (AT/RT)5 and several subgroups of ependymoma.6 MR imaging shows promise as a technique for differentiating histologic tumors and their molecular subgroups. This capability relies on not only various imaging characteristics but also the location and spatial extension of the tumor, evident on MR imaging, which can be traced to the embryologic origin of the neoplastic cells.5,7-10One approach to the challenge of identifying imaging characteristics of different tumors in children is to use artificial intelligence. Yet despite this exciting innovation, correctly identifying the location of the mass and its possible use as an element for differential diagnosis still requires the expertise of an experienced radiologist. Previously, D''Arco et al11 proposed a flow chart (Fig 1) for the differential diagnosis of posterior fossa tumors in children based on epidemiologic, imaging signal, and location characteristics of the neoplasm. The aims of the current study were the following: 1) to validate, in a retrospective, large cohort of posterior fossa tumors from 2 separate pediatric tertiary centers, the diagnostic accuracy of that flow chart, which visually represents the neuroadiologist''s mental process in making a diagnosis of posterior fossa tumors in children, 2) to describe particular types of posterior fossa lesions that are not correctly diagnosed by the initial flow chart, and 3) to provide an improved, clinically accessible flow chart based on the results.Open in a separate windowFIG 1.Predesigned radiologic flow chart created according to the literature before diagnostic accuracy analysis. The asterisk indicates brain stem tumors excluded from the analysis. Double asterisks indicate relative to gray matter. Modified with permission from D''Arco et al.11 相似文献
29.
Aaron T. Seaman 《Medical anthropology》2020,39(1):29-40
ABSTRACTSpousal caregivers draw upon understandings of shifting relationality to maintain a familial understanding of their spouse with Alzheimer’s disease. Working through what it means to think of an adult with Alzheimer’s disease “like a child,” I trace how spouses negotiate their shifting relationships across the course of Alzheimer’s. While regarding adults as childlike can be perceived as dehumanizing infantilization, for families living with Alzheimer’s disease, conceiving of one’s spouse as like a child can actually enable processes of continued care, sustained recognition, and love to uphold personhood in the midst of often radical change. 相似文献
30.
Chahine C. Assi Hanane B. Barakat Jacques H. Caton Elie N. Najjar Camille T. Samaha Kaissar F. Yammine 《The Journal of arthroplasty》2019,34(2):333-337