全文获取类型
收费全文 | 49032篇 |
免费 | 2967篇 |
国内免费 | 240篇 |
专业分类
耳鼻咽喉 | 500篇 |
儿科学 | 922篇 |
妇产科学 | 626篇 |
基础医学 | 6389篇 |
口腔科学 | 1081篇 |
临床医学 | 5153篇 |
内科学 | 10795篇 |
皮肤病学 | 986篇 |
神经病学 | 5625篇 |
特种医学 | 2497篇 |
外科学 | 8212篇 |
综合类 | 295篇 |
一般理论 | 13篇 |
预防医学 | 2251篇 |
眼科学 | 643篇 |
药学 | 2932篇 |
中国医学 | 69篇 |
肿瘤学 | 3250篇 |
出版年
2023年 | 431篇 |
2022年 | 689篇 |
2021年 | 1411篇 |
2020年 | 838篇 |
2019年 | 1266篇 |
2018年 | 1432篇 |
2017年 | 1122篇 |
2016年 | 1342篇 |
2015年 | 1552篇 |
2014年 | 1966篇 |
2013年 | 2421篇 |
2012年 | 3890篇 |
2011年 | 3921篇 |
2010年 | 2329篇 |
2009年 | 2099篇 |
2008年 | 3344篇 |
2007年 | 3431篇 |
2006年 | 3164篇 |
2005年 | 3115篇 |
2004年 | 2757篇 |
2003年 | 2637篇 |
2002年 | 2375篇 |
2001年 | 436篇 |
2000年 | 330篇 |
1999年 | 397篇 |
1998年 | 477篇 |
1997年 | 361篇 |
1996年 | 286篇 |
1995年 | 221篇 |
1994年 | 219篇 |
1993年 | 164篇 |
1992年 | 140篇 |
1991年 | 130篇 |
1990年 | 97篇 |
1989年 | 89篇 |
1988年 | 93篇 |
1987年 | 60篇 |
1986年 | 72篇 |
1985年 | 69篇 |
1984年 | 102篇 |
1983年 | 80篇 |
1982年 | 75篇 |
1981年 | 57篇 |
1980年 | 55篇 |
1979年 | 48篇 |
1978年 | 47篇 |
1977年 | 50篇 |
1976年 | 46篇 |
1975年 | 47篇 |
1974年 | 47篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
71.
OBJECTIVE: This study analyzed the influence of the acquisition method in image-free computer-assisted total knee arthroplasty (CAS-TKA), and the reproducibility of implant planning using BoneMorphing, a 3D morphometric model obtained by a 3D-to-3D elastic registration of statistical models to sparse point clouds acquired directly on the bone surface with a pointer. MATERIALS AND METHODS: Five surgeons (one expert, four trainees) each performed a CAS-TKA hybrid protocol based on morphometric models and landmarks on a cadaveric knee 10 times. In addition, several additional landmarks were digitized during each acquisition. The reproducibility of the implant positioning and sizing, as determined by an implant planning algorithm with morphometric models, was compared to direct digitization accuracy. RESULTS: Femoral and tibial implant positioning parameters with the hybrid protocol resulted in intra-surgeon standard deviations (SDs) of less than+/-1.4 degrees for rotation and 1.9 mm for translation for all surgeons in all directions except for tibial axial rotation (the only parameter determined by a digitized landmark and not recomputed in the 3D model). The variability in individual landmark digitization varied from 2 to 5 mm SD for certain landmarks, with ranges of 15-25 mm across all surgeons. The comparison study showed an improvement in femoral rotation reproducibility with the morphometric model when using the posterior condylar axis. Tibial implant reproducibility for each method was comparable, with the morphometric model giving better results in well-digitized areas such as the tibial plateau. CONCLUSION: A CAS-TKA protocol based on a deformed statistical model offers reproducible implant positioning. Some landmarks, such as distal condyles, show sufficient reproducibility in the direction of interest, while others, such as the anterior tibial tubercle, can lead to hazardous implant positioning. This should be taken into consideration when designing a CAS-TKA system with bony landmarks. In areas where a sufficient number of points have been digitized with good coverage, such as on the distal and posterior femoral condyles or the tibial plateau areas, the information derived from the 3D model is more accurate and reproducible than that derived from digitization. Good training and a guiding user interface are essential to guarantee coverage quality. 相似文献
72.
Naoyuki Hashiguchi Yu Chen Christian Rusu David B. Hoyt Wolfgang G Junger 《European Journal of Trauma》2005,31(4):379-388
AbstractBackground and Purpose: Polymorphonuclear neutrophils (PMNs) protect the host from invading microorganisms, but excessive PMN activation after trauma causes tissue injury. Rapid monitoring of PMN function is critical for the assessment of the inflammatory state of trauma patients. Here, the authors adapted two simple and rapid methods to measure oxidative burst and degranulation of human PMNs in whole blood to avoid potential interference of cell isolation procedures with the assessment of PMN function.Material and Methods: Heparinized blood was drawn from healthy volunteers or trauma patients, preincubated at 37 °C for 5 min, and stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP). Four assays for oxidative burst were tested: (1) cytochrome C; (2) homovanillic acid (HVA); (3) Amplex® Red; and (4) flow cytometry with dihydrorhodamine 123 (DHR). PMN degranulation was assessed with flow cytometry using antibodies to: (1) CD11b/Mac-1 (CD18); (2) CD63; and (3) CD66b (CD67).Results: With the exception of the DHR method, all methods to measure oxidative burst were found to be unsuitable in whole blood due to interference of plasma proteins and hemoglobin with the fluorimetric or photometric readouts. By contrast, all degranulation methods were suitable for whole-blood studies. However, for the assessment of formyl peptide-induced degranulation, anti-antibodies to CD11b/Mac-1 and CD66b were up to five times more sensitive than antibodies to CD63. Thus, the degranulation and DHR methods were optimized for increased sensitivity, speed, and specificity and their usefulness to measure PMN function in trauma patients was tested.Conclusion: The whole-blood methods based on flow cytometry with DHR, anti-CD11b/Mac-1, and anti- CD66b are rapid, simple, and reliable techniques to assess PMN function for trauma research. 相似文献
73.
Christian Lee Norman Tinanoff Glenn Minah Elaine Romberg 《Journal of public health dentistry》2008,68(1):57-60
OBJECTIVES: Visible plaque on the maxillary anterior teeth of young children has been identified as a risk indicator for early childhood caries. The present study examined whether this plaque is related to the colonization of children's teeth with Mutans streptococci (MS) or toothbrushing frequency. METHODS: Thirty-nine children, aged 12 to 36 months, had plaque scores, and plaque samples were taken from the labial surfaces of the maxillary incisors at baseline and repeated 3 days after suspended oral hygiene (plaque regrowth). RESULTS: A positive correlation was found between the baseline percent MS and regrowth plaque score and between baseline and regrowth plaque scores. Plaque scores of those that brushed zero to one time a day were not different from those who brushed two or more times a day. CONCLUSIONS: This study suggests that the presence of plaque on the anterior teeth of young children is consistent and related to MS colonization. 相似文献
74.
75.
Daniel Klase Stefan Gottschalk Erich Reusche Christian Hagel Einar Goebel Volker Tronnier Alf Giese 《Child's nervous system》2007,23(8):907-912
CASE REPORT: The reported female patient underwent sub-total resection of an intra-medullary cervicothoracic astrocytoma classified as WHO grade II in 1984 at the age of 18 months and received local irradiation. In 1989, a local recurrence was diagnosed and a partial resection was performed. Sixteen years later, a small recurrent cervicothoracic tumour was found and spinal seeding to the equine nerve roots and the left cerebellar cortex was apparent on MRI. The patient was implanted with a ventriculoperitoneal shunt for a pseudo-tumour cerebri producing papilloedema, which eventually lead to amaurosis. After an extended biopsy, the invasive lumbosacral tumour was classified as glioblastoma multiforme. Two months later, the patient died after rapid progression of the caudal cranial nerve dysfunction. DISCUSSION AND CONCLUSION: Anaplastic progression and dissemination of spinal astrocytomas even two decades after initial diagnosis and treatment are rare. Therapies and diagnostic follow-up strategies are discussed. 相似文献
76.
Thompson Debra A.; Janecke Andreas R.; Lange Jessica; Feathers Kecia L.; Hubner Christian A.; McHenry Christina L.; Stockton David W.; Rammesmayer Gabriele; Lupski James R.; Antinolo Guillermo; Ayuso Carmen; Baiget Montserrat; Gouras Peter; Heckenlively John R.; den Hollander Anneke; Jacobson Samuel G.; Lewis Richard A.; Sieving Paul A.; Wissinger Bernd; Yzer Suzanne; Zrenner Eberhart; Utermann Gerd; Gal Andreas 《Human molecular genetics》2006,15(9):1559
Human Molecular Genetics 相似文献
77.
Christian Schoch 《Journal of ocular pharmacology and therapeutics》2003,19(2):153-159
The effects of ketotifen and lodoxamide on eosinophil infiltration were assessed in a guinea pig model of allergic conjunctivitis. The two active treatments were coded in this masked study in which 30 male guinea pigs, sensitized to chicken egg albumin (ovalbumin), were randomly assigned to one of three groups: Group 1, instillation of 0.9% NaCl into the conjunctival sac of both eyes; Group 2, instillation of 0.025% ketotifen into the left eye and 0.9% NaCl into the right eye; Group 3, instillation of 0.1% lodoxamide into the left eye and 0.9% NaCl into the right eye. Ovalbumin was administered topically to each eye, except in Group 1 where it was only applied to the left eye. (111)In-oxine labeled eosinophils were injected into the jugular vein of each guinea pig; the animals were sacrificed 17 hours after ovalbumin had been applied. The level of radioactivity in the ketotifen- and lodoxamide-treated eyes was approximately 60% of that in the saline-treated eyes. Moreover, the mean level of radioactivity in the ketotifen- and lodoxamide-treated eyes was comparable with the mean level of radioactivity in the saline-treated eye of Group 1, which had not been exposed to allergen. These results indicate that the therapeutic effects of ketotifen and lodoxamide in allergic conjunctivitis may be partly mediated by an inhibitory effect on eosinophils. 相似文献
78.
Surber Christian Wilhelm Klaus-P. Bermann David Maibach Howard I. 《Pharmaceutical research》1993,10(9):1291-1294
Etretinate and acitretin are given orally to treat psoriasis and various keratinization disorders. Acitretin, the main active metabolite of etretinate, has the pharmacokinetic advantage of being rapidly eliminated, but it shares etretinate's toxicologic profile. Thus a topical delivery of acitretin with no or reduced systemic adverse effects is desirable. To characterize the therapeutic potential of topically delivered acitretin, we quantitatively assessed its percutaneous penetration in healthy human volunteers. Additionally, three skin sampling techniques, the punch biopsy, the shave biopsy, and the suction blister technique, were validated to quantitate acitretin in the skin. The results suggest that topical delivery of acitretin renders skin concentrations which exceed those reported after oral administration of etretinate or acitretin. However, because of possible interlaminate drug contamination, drug localization within a particular skin compartment cannot be determined. 相似文献
79.
A wireless device for the assessment of tardive dyskinesia by means of digital image processing is presented. Four skin-cream dots placed around the subjects' mouth are recorded by a video camera. The image is passed to a framegrabber with a signal processor, where it is converted from analogue to digital. A fast spot-detecting algorithm implemented on the signal processor tracks the dots and passes the information to a personal computer, where a Fourier transformation is performed to calculate the frequency spectrum of the movements. The device provided detailed information on the magnitude and on the frequencies of the movements. Data from a longitudinal investigation suggest a higher sensitivity and reliability than conventional rating scales to detect and evaluate abnormal perioral movements. The device might be useful for the early detection, for the longitudinal assessment (p.e. clinical trials) and in some cases for the differential diagnosis of tardive dyskinesia, thus providing a tool for both research and clinical purposes. 相似文献
80.
Lead poisoning in six captive avian species 总被引:2,自引:0,他引:2
W. Nelson Beyer James W. Spann Louis Sileo J. Christian Franson 《Archives of environmental contamination and toxicology》1988,17(1):121-130
Red-winged blackbirds (Agelaius phoeniceus), brown-headed cowbirds (Molothrus ater), common grackles (Quiscalus quiscula), mallards (Anas platyrhynchos), northern bobwhites (Colinus virginianus), and eastern screech-owls (Otus asio) were poisoned with a concentration of lead (Pb) acetate in the diet which was increased by 60% each week until half of the birds in each treatment group died; surviving birds and all control birds except screech-owis were then killed by euthanasia. An additional group of mallards was poisoned with Pb shot. The gizzards of mallards poisoned either way usually were stained with bile; some of these birds also had proventricular impaction. Most poisoned birds of the other species were emaciated but lacked other gross lesions caused by Pb poisoning. In birds other than mallards, Pb poisoning could not be diagnosed without histological or hematological examinations or analysis of tissues. Poisoned birds of all six species could be reliably separated from control birds by an increase in the protoporphyrin concentrations in the blood and by a decrease in the activity of delta-aminolevulinic acid dehydratase (ALAD) in red blood cells. Hepatic iron (Fe) concentrations varied so much among individual birds that even though median hepatic Fe concentrations increased in poisoned birds, hepatic Fe concentrations were not useful in identifying poisoned birds. Renal intranuclear inclusion bodies occurred in 83% of all birds dying from Pb poisoning. Nephrosis, myocardial necrosis, and arterial fibrinoid necrosis were occasionally present. Median hepatic Pb concentrations varied from 20 ppm (wet wt) in male red-winged blackbirds to 111 ppm in female northern bobwhites. Median renal Pb concentrations varied from 22 ppm in redwinged blackbirds to 190 ppm in female northern bobwhites. Hepatic and renal Pb concentrations varied substantially among birds within each species. Median hepatic and renal Pb concentrations of birds that died were not statistically different (p > 0.05) from those of birds that were killed. Lead shot and Pb acetate affected mallards similarly. 相似文献