全文获取类型
收费全文 | 27331篇 |
免费 | 1367篇 |
国内免费 | 159篇 |
专业分类
耳鼻咽喉 | 277篇 |
儿科学 | 557篇 |
妇产科学 | 626篇 |
基础医学 | 3470篇 |
口腔科学 | 1067篇 |
临床医学 | 2002篇 |
内科学 | 7281篇 |
皮肤病学 | 701篇 |
神经病学 | 2102篇 |
特种医学 | 605篇 |
外科学 | 4420篇 |
综合类 | 176篇 |
一般理论 | 3篇 |
预防医学 | 1980篇 |
眼科学 | 487篇 |
药学 | 1480篇 |
中国医学 | 122篇 |
肿瘤学 | 1501篇 |
出版年
2023年 | 216篇 |
2022年 | 441篇 |
2021年 | 962篇 |
2020年 | 449篇 |
2019年 | 906篇 |
2018年 | 1050篇 |
2017年 | 585篇 |
2016年 | 596篇 |
2015年 | 765篇 |
2014年 | 1117篇 |
2013年 | 1398篇 |
2012年 | 2228篇 |
2011年 | 2291篇 |
2010年 | 1352篇 |
2009年 | 1164篇 |
2008年 | 1831篇 |
2007年 | 1895篇 |
2006年 | 1736篇 |
2005年 | 1549篇 |
2004年 | 1436篇 |
2003年 | 1377篇 |
2002年 | 1253篇 |
2001年 | 163篇 |
2000年 | 128篇 |
1999年 | 167篇 |
1998年 | 196篇 |
1997年 | 149篇 |
1996年 | 150篇 |
1995年 | 128篇 |
1994年 | 106篇 |
1993年 | 92篇 |
1992年 | 80篇 |
1991年 | 66篇 |
1990年 | 61篇 |
1989年 | 44篇 |
1988年 | 56篇 |
1987年 | 41篇 |
1986年 | 33篇 |
1985年 | 47篇 |
1984年 | 42篇 |
1983年 | 51篇 |
1982年 | 57篇 |
1981年 | 59篇 |
1980年 | 53篇 |
1979年 | 28篇 |
1978年 | 30篇 |
1977年 | 29篇 |
1976年 | 21篇 |
1975年 | 22篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
921.
Pseudo-continuous arterial spin labeling (pCASL) is a very powerful technique to measure cerebral perfusion, which circumvents the problems affecting other continuous arterial spin labeling schemes, such as magnetization transfer and duty cycle. However, some variability in the tagging efficiency of the pCASL technique has been reported. This article investigates the effect of B(0) field inhomogeneity on the tagging efficiency of the pCASL pulse sequence as a possible cause of this variability. Both theory and simulated data predict that the efficiency of pseudo-continuous labeling pulses can be degraded in the presence of off-resonance effects. These findings are corroborated by human in vivo measurements of tagging efficiency. On the basis of this theoretical framework, a method utilizing B(0) field map information is proposed to correct for the possible loss in tagging efficiency of the pCASL pulse sequence. The efficiency of the proposed correction method is evaluated using numerical simulations and in vivo implementation. The data show that the proposed method can effectively recover the lost tagging efficiency and signal-to-noise ratio of pCASL caused by off-resonance effects. 相似文献
922.
Scott RS Bustillo D Olivos-Oré LA Cuchillo-Ibañez I Barahona MV Carbone E Artalejo AR 《Pflügers Archiv : European journal of physiology》2011,462(4):545-557
BK channels modulate cell firing in excitable cells in a voltage-dependent manner regulated by fluctuations in free cytosolic
Ca2+ during action potentials. Indeed, Ca2+-independent BK channel activity has ordinarily been considered not relevant for the physiological behaviour of excitable
cells. We employed the patch-clamp technique and selective BK channel blockers to record K+ currents from bovine chromaffin cells at minimal intracellular (about 10 nM) and extracellular (free Ca2+) Ca2+ concentrations. Despite their low open probability under these conditions (V50 of +146.8 mV), BK channels were responsible for more than 25% of the total K+ efflux during the first millisecond of a step depolarisation to +20 mV. Moreover, BK channels activated about 30% faster
(τ = 0.55 ms) than the rest of available K+ channels. The other main source of fast voltage-dependent K+ efflux at such a low Ca2+ was a transient K+ (IA-type) current activating with V
50 = −14.2 mV. We also studied the activation of BK currents in response to action potential waveforms and their contribution
to shaping action potentials both in the presence and the absence of extracellular Ca2+. Our results show that BK channels activate during action potentials and accelerate cell repolarisation even at minimal Ca2+ concentration, and suggest that they could do so also in the presence of extracellular Ca2+, before Ca2+ entering the cell facilitates their activity. 相似文献
923.
Retamal MA Evangelista-Martínez F León-Paravic CG Altenberg GA Reuss L 《Pflügers Archiv : European journal of physiology》2011,461(6):635-643
Connexins form hemichannels at undocked plasma membranes and gap-junction channels (GJCs) at intercellular contacting zones.
Under physiological conditions, hemichannels have low open probabilities, but their activation under pathological conditions,
such as ischemia, induces and/or accelerates cell death. Connexin 46 (Cx46) is a major connexin of the lens, and mutations
of this connexin induce cataracts. Here, we report the effects of linoleic acid (LA) on the electrical properties of Cx46
GJCs and hemichannels expressed in Xenopus laevis oocytes. LA has a biphasic effect, increasing hemichannel current at 0.1 μM and decreasing it at concentrations of 100 μM
or higher. The effects of extracellular and microinjected LA conjugated to coenzyme A (LA-CoA) suggest that the current activation
site is accessible from the intracellular but not extracellular compartment, whereas the current inhibitory site is either
located in a region of the hemichannel pore inaccessible to intracellular LA-CoA, or requires crossing of LA through an organelle
membrane. Experiments with other fatty acids demonstrated that the block of hemichannels depends on the presence of a hydrogenated
double bond at position 9 and is directly proportional to the number of double bonds. Experiments in paired oocytes expressing
Cx46 showed that LA does not affect GJCs. The block by unsaturated fatty acids reported here opens the possibility that increases
in the concentration of these lipids in the lens induce cataract formation by blocking Cx46 hemichannels. 相似文献
924.
Ana Treviño Rafael Benito Estrella Caballero José Manuel Ramos Patricia Parra Lourdes Roc Jose Maria Eiros Antonio Aguilera Juan García Carmen Cifuentes Goitzane Marcaida Carmen Rodríguez Matilde Trigo Luis A. Arroyo Carmen de Mendoza Raúl Ortíz de Lejarazu Vincent Soriano 《Journal of clinical virology》2011,52(2):119-122
Background
The overall seroprevalence of HTLV infection among pregnant women in Spain is below 0.02% and accordingly universal antenatal screening is not recommended. However, as the number of immigrants has significantly increased during the last decade, this population might warrant specific considerations.Objective
To evaluate the seroprevalence of HTLV infection among immigrant pregnant women living in Spain.Methods
From January 2009 to December 2010 a cross-sectional study was carried out in all foreign pregnant women attended at 14 Spanish clinics. All were tested for HTLV antibodies using a commercial enzyme-immunoassay, being reactive samples confirmed by Western blot or PCR.Results
A total of 3337 foreign pregnant women were examined. Their origin was as follows: Latin America 1579 (47%), North Africa 507 (16%), East Europe 606 (18%), Sub-Saharan Africa 316 (9%), North America and West Europe 116 (3.5%) and Asia and Australia 163 (5%). A total of 7 samples were confirmed as HTLV positive, of which 6 were HTLV-1 and 1 HTLV-2. HTLV-1 infection was found in 5 women coming from Latin America and 1 from Morocco. The only woman with HTLV-2 came from Ghana. The overall HTLV seroprevalence was 0.2%, being 0.3% among Latin Americans and 0.2% among Africans. It was absent among women coming from other regions.Conclusions
The seroprevalence of HTLV infection among foreign pregnant women in Spain is 0.2%, being all cases found in immigrants from Latin America and Africa. Given the benefit of preventing vertical transmission, antenatal screening should be recommended in pregnant women coming from these regions. 相似文献925.
Lugo-Reyes Saul Oswaldo Pastor Nina González-Serrano Edith Yamazaki-Nakashimada Marco Antonio Scheffler-Mendoza Selma Berron-Ruiz Laura Wakida Guillermo Nuñez-Nuñez Maria Enriqueta Macias-Robles Ana Paola Staines-Boone Aide Tamara Venegas-Montoya Edna Alaez-Verson Carmen Molina-Garay Carolina Flores-Lagunes Luis Leonardo Carrillo-Sanchez Karol Niemela Julie Rosenzweig Sergio D. Gaytan Paul Yañez Jorge A. Martinez-Duncker Ivan Notarangelo Luigi D. Espinosa-Padilla Sara Cruz-Munoz Mario Ernesto 《Journal of clinical immunology》2021,41(7):1708-1708
Journal of Clinical Immunology - A Correction to this paper has been published: https://doi.org/10.1007/s10875-021-01075-7 相似文献
926.
Paloma Merino Jesús Guinea Irene Muñoz-Gallego Patricia González-Donapetry Juan Carlos Galán Nerea Antona Gustavo Cilla Silvia Hernáez-Crespo José Luis Díaz-de Tuesta Ana Gual-de Torrella Fernando González-Romo Pilar Escribano Miguel Ángel Sánchez-Castellano Mercedes Sota-Busselo Alberto Delgado-Iribarren Julio García Rafael Cantón Patricia Muñoz Mila Montes 《Clinical microbiology and infection》2021,27(5):758-761
ObjectivesThe standard RT-PCR assay for coronavirus disease 2019 (COVID-19) is laborious and time-consuming, limiting testing availability. Rapid antigen-detection tests are faster and less expensive; however, the reliability of these tests must be validated before they can be used widely. The objective of this study was to determine the performance of the Panbio? COVID-19 Ag Rapid Test Device (PanbioRT) (Abbott) in detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in nasopharyngeal swab specimens.MethodsThis prospective multicentre study was carried out in ten Spanish university hospitals and included individuals with clinical symptoms or epidemiological criteria of COVID-19. Only individuals with ≤7 days from the onset of symptoms or from exposure to a confirmed case of COVID-19 were included. Two nasopharyngeal samples were taken to perform the PanbioRT as a point-of-care test and a diagnostic RT-PCR test.ResultsAmong the 958 patients studied, 325 (90.5%) had true-positive results. The overall sensitivity and specificity for the PanbioRT were 90.5% (95%CI 87.5–93.6) and 98.8% (95%CI 98–99.7), respectively. Sensitivity in participants who had a threshold cycle (CT) < 25 for the RT-PCR test was 99.5% (95%CI 98.4–100), and in participants with ≤5 days of the clinical course it was 91.8% (95%CI 88.8–94.8). Agreement between techniques was 95.7% (κ score 0.90; 95%CI 0.88–0.93).ConclusionsThe PanbioRT performs well clinically, with even more reliable results for patients with a shorter clinical course of the disease or a higher viral load. The results must be interpreted based on the local epidemiological context. 相似文献
927.
Laura Argiz Sonsoles Infante Adrianna Machinena Teresa Bracamonte Luis Echeverria Ana Prieto Teresa Garriga Leticia Vila Purificación Gonzalez-Delgado Carlos Garcia-Magan Emilio Garcia Iria Carballeira Sonia Vazquez-Cortes Francesca Mori Simona Barni Stefania Arasi Mariona Pascal Robert J. Boyle Marta Vazquez-Ortiz the BIO-FPIES study network 《Clinical and experimental allergy》2021,51(9):1238-1241
928.
929.
The search for decoy cells (DC) in urine is widely used as screening for BK virus (BKV) reactivation in transplant recipients. BKV cytopathic effect of DC must not be confused with high-grade urothelial carcinoma. This report presents a case of coexistence of DC and malignant cells in the urine from a transplant recipient with BKV-associated nephropathy (BKVN) and bladder adenocarcinoma. A 38-year-old female with type 1 diabetes mellitus and end-stage renal disease underwent a simultaneous pancreas and kidney transplant. Four years post-transplantation, BK virus studies were performed for renal dysfunction. Isolated DC and DC in casts were identified in urine. Also, the tests for BKV DNA were positive in serum and renal allograft biopsy. BKVN was treatment-resistant and the patient returned to hemodialysis. A kidney transplant nephrectomy was performed 2 years later. The next urine cytology showed, in addition to DC, other distinct cells with nuclear atypia highly suggestive of malignancy. Some cells showed both, malignant and DC features. A bladder adenocarcinoma was diagnosed on biopsy and BKV proteins were demonstrated on tumor cells, supporting a possible role for BKV in the oncogenic pathway in this clinical setting. The presence of DC in the urine from a transplant recipient is the hallmark of BKV activation, but it does not exclude the existence of carcinoma. Furthermore, the presence of highly atypical cells should raise, not eliminate, the possibility of neoplastic transformation of the bladder. 相似文献
930.
Fedson DS Nicolas-Spony L Klemets P van der Linden M Marques A Salleras L Samson SI 《Expert review of vaccines》2011,10(8):1143-1167
Vaccination is the only public-health measure likely to reduce the burden of pneumococcal diseases. In 2010, a group of European experts reviewed evidence on the burden of pneumococcal disease and the immunogenicity, clinical effectiveness and cost-effectiveness of vaccination with 23-valent pneumococcal polysaccharide vaccine (PPV23). They also considered issues affecting the future use of PPV23 and pneumococcal conjugate vaccines in the elderly and adults at high risk of pneumococcal disease. PPV23 covers 80-90% of the serotypes responsible for invasive pneumococcal disease in Europe. Primary vaccination and revaccination with PPV23 are well tolerated, induce robust, long-lasting immune responses in elderly adults and are cost effective. Ensuring protection against pneumococcal disease requires monitoring of the changing epidemiology of pneumococcal serotypes causing invasive pneumococcal disease and improving vaccine coverage. In the future, it will be critically important for pneumococcal vaccination recommendations for elderly adults to be based on comparative evaluations of PPV23 and newer pneumococcal conjugate vaccines with regard to their long-term immunogenicity, clinical effectiveness and cost-effectiveness. 相似文献