全文获取类型
收费全文 | 156631篇 |
免费 | 31547篇 |
国内免费 | 2396篇 |
专业分类
耳鼻咽喉 | 5201篇 |
儿科学 | 5614篇 |
妇产科学 | 2522篇 |
基础医学 | 3727篇 |
口腔科学 | 1656篇 |
临床医学 | 27990篇 |
内科学 | 48064篇 |
皮肤病学 | 7477篇 |
神经病学 | 15193篇 |
特种医学 | 6531篇 |
外科学 | 41336篇 |
综合类 | 312篇 |
现状与发展 | 72篇 |
一般理论 | 9篇 |
预防医学 | 7898篇 |
眼科学 | 3415篇 |
药学 | 1273篇 |
中国医学 | 8篇 |
肿瘤学 | 12276篇 |
出版年
2024年 | 690篇 |
2023年 | 4808篇 |
2022年 | 1224篇 |
2021年 | 3158篇 |
2020年 | 6070篇 |
2019年 | 2215篇 |
2018年 | 7480篇 |
2017年 | 7407篇 |
2016年 | 8485篇 |
2015年 | 8488篇 |
2014年 | 15645篇 |
2013年 | 15858篇 |
2012年 | 5843篇 |
2011年 | 5923篇 |
2010年 | 10564篇 |
2009年 | 14432篇 |
2008年 | 6166篇 |
2007年 | 4479篇 |
2006年 | 6917篇 |
2005年 | 4210篇 |
2004年 | 3434篇 |
2003年 | 2386篇 |
2002年 | 2485篇 |
2001年 | 3840篇 |
2000年 | 3039篇 |
1999年 | 3278篇 |
1998年 | 3696篇 |
1997年 | 3523篇 |
1996年 | 3405篇 |
1995年 | 3250篇 |
1994年 | 1984篇 |
1993年 | 1592篇 |
1992年 | 1414篇 |
1991年 | 1440篇 |
1990年 | 1088篇 |
1989年 | 1217篇 |
1988年 | 1037篇 |
1987年 | 878篇 |
1986年 | 907篇 |
1985年 | 733篇 |
1984年 | 578篇 |
1983年 | 536篇 |
1982年 | 539篇 |
1981年 | 421篇 |
1980年 | 388篇 |
1979年 | 319篇 |
1978年 | 341篇 |
1977年 | 401篇 |
1975年 | 291篇 |
1972年 | 312篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Acrocentric interconnections and NOR (nucleolus organizer region) variants are frequently observed in silver-stained metaphase preparations from lymphocytes of phenotypically normal individuals. The types of interconnections and of NOR variants are outlined. It is speculated that the satellite acrocentrics (both normal and variant) are the consequence of breakage and recoiling of these interconnections. Awareness of these two features of the human genome may facilitate understanding of the NOR/nucleolus interaction(s) in such important processes as nucleolus formation and in development and/or diagnosis of disease states (i.e., malignancy). 相似文献
992.
993.
A. N. Chalazonitis MD Ph.D D. Koumarianos RT J. Tzovara MD P. Chronopoulos MD 《Journal of digital imaging》2003,16(2):216-229
Over the past decade, the technology that permits images to be digitized and the reduction in the cost of digital equipment allows quick digital transfer of any conventional radiological film. Images then can be transferred to a personal computer, and several software programs are available that can manipulate their digital appearance. In this article, the fundamentals of digital imaging are discussed, as well as the wide variety of optional adjustments that the Adobe Photoshop 6.0 (Adobe Systems, San Jose, CA) program can offer to present radiological images with satisfactory digital imaging quality. 相似文献
994.
Robert J. Calsyn Gary A. Morse Robert D. Yonker Joel P. Winter Kathy J. Pierce Matthew J. Taylor 《Journal of community psychology》2003,31(4):339-348
Participants in this study suffered from severe mental illness and were homeless at baseline. They were given their choice of five different treatment programs. The current study investigated two major questions: (1) what is the impact of positive expectancies about the efficacy of the chosen program on number of contacts with the chosen program and client outcomes; and (2) what is the impact of positive views about nonchosen programs (alternative choice variables) on contact with the chosen program and client outcomes. Client outcomes assessed were psychotic symptoms, days homeless, and client satisfaction. Positive expectancy variables were the number of reasons for choosing a program and confidence that the program would help. Alternative choice variables were the number of nonchosen programs visited and the attractiveness of a nonchosen program. Only the number of reasons for choosing the program was significantly related to program contact with the chosen program. Both of the positive expectancy variables and program contact were significantly correlated with consumer satisfaction. In general, neither the positive expectancy variables nor the alternative choice variables predicted changes in psychotic symptoms nor days homeless. © 2003 Wiley Periodicals, Inc. J Comm Psychol 31: 339–348, 2003. 相似文献
995.
Sabina Rak MD PhD Anette Bjrnson MSc Lena Hkanson MSc PhD Sverre Srenson MD PhD Per Venge MD PhD 《The Journal of allergy and clinical immunology》1991,88(6):878-888
Two groups of birch pollen--allergic patients with seasonal rhinoconjunctivitis and asthma were followed during two consecutive birch-pollen seasons, one group, N = 10, during a season with high pollen load, and one group, N = 15, during a season of low pollen load. Half the patients were treated with immunotherapy (IT) for 3 and 4 years, respectively. The other half of the patients served as control group (non-IT). Bronchoalveolar lavage (BAL) was performed once before each season and once during the pollen season. Eosinophil (EOS) numbers in BAL were increased (p less than 0.01) during the season with high pollen load but not in the season with a low pollen load, and this increment was absent in the IT-treated group. Also, the EOS cationic protein levels were raised in the non-IT-treated group during the season with a high pollen load. The levels of EOS and neutrophil chemotactic activity were raised in BAL in both seasons in the non-IT-treated group compared with the IT-treated group (p less than 0.02, p less than 0.003, p less than 0.04, and p less than 0.005 in high- and low-load pollen season, respectively). Serum and BAL eosinophil chemotactic activity (ECA) were positively correlated (p less than 0.001). We conclude that there is an influx of active EOSs into the lung of pollen-allergic patients with asthma during a pollen season, which may be abrogated by IT. Furthermore, the generation of ECA appears to be an extremely sensitive marker of antigenic exposure, and the potent inhibition of the generation of ECA by IT may provide a clue as to the mechanism of this treatment. 相似文献
996.
H. R. Ochs MD D. J. Greenblatt U. Klehr 《Journal of molecular medicine (Berlin, Germany)》1984,62(16):765-767
Summary The pharmacokinetics of a single 30-mg oral dose of oxazepam was evaluated in seven patients with chronic renal failure on maintenance hemodialysis and in seven healthy controls matched for age and sex. Based on total (free plus bound) serum oxazepam concentrations, elimination half-life was prolonged in renal patients compared to controls (22 vs 8 h,p<0.001) and volume of distribution increased (3.0 vs 1.4 1/kg,p<0.02). However, total clearance was similar between groups (1.8 vs 1.9 ml/min per kilogram). These findings were confounded by the increased oxazepam free fraction in serum of renal failure patients (10.3%) as compared to healthy controls (4.3%). Correction for differences in binding indicates similar distribution of unbound oxazepam between groups, but reduced clearance of pharmacologically active unbound oxazepam in renal patients (18 vs 45 ml/min per kilogram). Oxazepam dosage, therefore, may require downward adjustment for renal failure patients on hemodialysis.Supported in part by grant OC 10/6-3 from the Deutsche Forschungsgemeinschaft, and by grant MH-34223 from the United States Public Health Service 相似文献
997.
Frederick L. Datz MD Charles Rosenberg Frank V. Gabor Paul E. Christian Grant T. Gullberg Raj Ahluwalia Kathryn A. Morton 《Journal of digital imaging》1993,6(2):67-80
Computer-assisted diagnosis (CAID) is commonly used to evaluate cardiac nuclear medicine studies such as thallium perfusion scans. Part 1 of this series (Journal of Digital Imaging, 5:209–222, 1992) reviewed the basic theory underlying CAID in nuclear medicine and its use in planar thallium imaging. Part 2 discussed the application of CAID to SPECT perfusion studies (Journal of Digital Imaging, 6:1–15, 1993). This article reviews new variations of CAID programs for SPECT imaging and the application of expert systems and neural networks to CAID of nuclear medicine perfusion studies. 相似文献
998.
Rooijens PP de Krijger RR Bonjer HJ van der Ham F Nigg AL Bruining HA Lamberts SW van der Harst E 《Endocrine pathology》2004,15(1):39-45
The purpose of this study was to investigate tumor angiogenesis in a series of benign and malignant pheochromocytomas and
to determine whether there is a correlation between angiogenesis and the presence of distant metastases. In this study, the
CD31 monoclonal antibody was selected to measure intratumoral microvessel density. Nineteen patients with malignant pheochromocytomas
and nineteen patients with benign pheochromocytomas who underwent operation were studied. In order to quantify intratumoral
microvessel density, the total number of pixels of CD31-positive reactivity was assessed and expressed as a percentage of
the total tissue area in the analyzed field. Analysis of variance revealed a statistically significant correlation between
malignancy and intratumoral microvessel density (p=0.0009). Although there was a considerable variability in the intratumoral microvessel density from tumor to tumor within
both the benign and the malignant group, a percentage of more than 28.5% anti-CD31 stained area was found only in malignant
tumors. In conclusion, this study shows that the mean intratumoral microvessel density in malignant pheochromocytomas is increased
approximately two-fold as compared with benign tumors. However, the clinical significance of this prognostic marker is rather
weak, because only 4 of the 19 malignant pheochromocytomas had microvesel density higher than this threshold of 28.5%. 相似文献
999.
1000.
A programme of clinical studies was carried out to determine the basic efficacy and safety of 2% nedocromil sodium eye drops (Tilavist) in treating allergic conjunctivitis, in 2,905 patients from 3–76 years of age. Results of all the double-masked placebo comparative studies completed to date - five in vernal keratoconjunctivitis (VKC), five in perennial (PAC) and 16 in seasonal allergic conjunctivitis (SAC) - have been assessed in a statistical overview analysis. Nedocromil sodium, administered four times daily to 153 patients with VKC, was significantly more effective than placebo (155 patients) and in the clinicians' opinion gave good control in 76% of cases, compared with 46% for placebo (p < 0.001). Patients with chronic symptoms of PAC also responded better to nedocromil sodium given four times daily (n = 146) rather than twice daily (n = 86), and significantly more patients (p < 0.001) were effectively controlled by four times daily treatment with nedocromil sodium (72%) than with placebo (47%; n= 156). Twice-daily dosage with nedocromil sodium (n = 677) was adequate for SAC, however, and the treatment was statistically better than placebo (p < 0.01-p < 0.001) whether dosed twice or four times daily. Speed of action was assessed in seven SAC studies in which 79% of all patients (n = 295) using nedocromil sodium had experienced relief of symptoms when questioned, half of them within 15 minutes and 74% during the first hour after dosing. Test treatments were well-accepted by both adults and children, and there were no major adverse events. Minor irritations reported more frequently with nedocromil sodium than placebo were stinging or burning of the eyes on application of the drops and a distinctive taste, noted by 5% of the active treatment group (n = 1,552). 相似文献