全文获取类型
收费全文 | 2211篇 |
免费 | 128篇 |
国内免费 | 67篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 99篇 |
妇产科学 | 37篇 |
基础医学 | 244篇 |
口腔科学 | 65篇 |
临床医学 | 252篇 |
内科学 | 444篇 |
皮肤病学 | 37篇 |
神经病学 | 88篇 |
特种医学 | 333篇 |
外科学 | 251篇 |
综合类 | 43篇 |
一般理论 | 1篇 |
预防医学 | 215篇 |
眼科学 | 36篇 |
药学 | 101篇 |
肿瘤学 | 133篇 |
出版年
2021年 | 21篇 |
2019年 | 16篇 |
2018年 | 18篇 |
2016年 | 15篇 |
2015年 | 24篇 |
2014年 | 34篇 |
2013年 | 51篇 |
2012年 | 71篇 |
2011年 | 64篇 |
2010年 | 52篇 |
2009年 | 55篇 |
2008年 | 49篇 |
2007年 | 119篇 |
2006年 | 62篇 |
2005年 | 68篇 |
2004年 | 65篇 |
2003年 | 52篇 |
2002年 | 57篇 |
2001年 | 48篇 |
2000年 | 52篇 |
1999年 | 52篇 |
1998年 | 80篇 |
1997年 | 78篇 |
1996年 | 81篇 |
1995年 | 62篇 |
1994年 | 49篇 |
1993年 | 57篇 |
1992年 | 43篇 |
1991年 | 45篇 |
1990年 | 58篇 |
1989年 | 67篇 |
1988年 | 50篇 |
1987年 | 68篇 |
1986年 | 43篇 |
1985年 | 57篇 |
1984年 | 32篇 |
1983年 | 44篇 |
1982年 | 31篇 |
1981年 | 27篇 |
1980年 | 27篇 |
1979年 | 25篇 |
1978年 | 18篇 |
1977年 | 21篇 |
1975年 | 14篇 |
1972年 | 18篇 |
1971年 | 20篇 |
1970年 | 14篇 |
1969年 | 14篇 |
1968年 | 15篇 |
1947年 | 15篇 |
排序方式: 共有2406条查询结果,搜索用时 0 毫秒
81.
小鼠皮肤超氧化物歧化酶活性与枸杞多糖的干预 总被引:1,自引:0,他引:1
目的:观察枸杞多糖对皮肤胶原代谢和自由基产生的影响,探讨其抗皮肤衰老的作用。方法:实验于2005-06/2006-05在广东医学院整形外科研究所完成。①实验材料:清洁级昆明小鼠60只,月龄2个月,体质量16~24g,雌雄各半。②实验分组:将小鼠随机分为正常对照组、衰老模型组和抗衰老模型组,每组20只。③实验干预:模型组每日用D-半乳糖溶液皮下注射制造衰老模型,用量和时间为80mg/(kg·d)7d,120mg/(kg·d)14d,140mg/(kg·d)14d,180mg/(kg·d)7d。正常对照组每日注射同体积的生理盐水。抗衰老模型组在注射D-半乳糖期间以枸杞多糖灌胃,剂量为20mg/(kg·d),正常对照组和衰老组则以同体积的生理盐水代之灌胃。④实验评估:42d后切取小鼠颈背部皮肤,测定超氧化物歧化酶活力、羟脯氨酸和丙二醛含量。结果:56只小鼠进入结果分析(4只死亡)。①小鼠皮肤超氧化物歧化酶活力:与正常对照组相比,衰老组和抗衰老组小鼠皮肤超氧化物歧化酶活力降低,差异有显著性意义(P<0.01);抗衰老组与衰老模型组比较,超氧化物歧化酶活力增加,差异有显著性意义(P<0.01)。②与正常对照组相比,衰老组和抗衰老组小鼠皮肤羟脯氨酸和丙二醛含量增加,差异有显著性意义(P<0.01);抗衰老组与衰老组比较,羟脯氨酸和丙二醛含量均降低,差异有显著性意义(P<0.01)。结论:枸杞多糖改善皮肤老化的作用与提高小鼠皮肤超氧化物歧化酶活力,降低羟脯氨酸、丙二醛含量,影响胶原代谢有关。 相似文献
82.
Jaclyn A. Shepard Marc Breton Revital Nimri Joseph T. F. Roberts Timothy Street David Klonoff Katharine Barnard-Kelly 《Journal of diabetes science and technology》2022,16(1):224
A growing number of individuals with type 1 diabetes are choosing to use “do-it-yourself” artificial pancreas systems (DIY APS) to support their diabetes self-management. Observational and self-report data of glycemic benefits of DIY APS are promising; however, without rigorous clinical trials or regulation from governing bodies, liability and user safety continue to be central concerns for stakeholders. Despite DIY APS having been used for several years now, there are no guidelines to assist users and healthcare professionals in addressing DIY APS use in routine clinical care. This commentary reports key stakeholders’ perspectives presented at the annual Advanced Technologies and Treatments in Diabetes conference in February 2020. Important considerations to inform the development of clinical care guidelines are also presented to generate further debate. 相似文献
83.
Efficient gene delivery to multipotential hematopoietic stem cells would greatly facilitate the development of effective gene therapy for certain hematopoietic disorders. We have recently described a rapid multiparameter sorting procedure for significantly enriching stem cells with competitive long-term lymphomyeloid repopulating ability (CRU) from 5-fluorouracil (5-FU)-treated mouse bone marrow. The sorted cells have now been tested as targets for retrovirus-mediated delivery of a marker gene, NeoR. They were cocultured for 4 days with fibroblasts producing a high titer of retrovirus in medium containing combinations of the hematopoietic growth factors interleukin-3 (IL-3), IL-6, c-kit ligand (KL), and leukemia inhibitory factor (LIF) and then injected into lethally irradiated recipients, together with sufficient "compromised" bone marrow cells to provide short-term support. Over 80% of the transplanted mice displayed high levels (> or = 20%) of donor- derived leukocytes when analyzed 4 to 6 months later. Proviral DNA was detected in 87% of these animals and, in half of them, the majority of the hematopoietic cells were marked. Thus, infection of the stem cells was most effective. The tissue and cellular distribution of greater than 100 unique clones in 55 mice showed that most sorted stem cells had lymphoid as well as myeloid repopulating potential. Secondary transplantation provided strong evidence for infection of very primitive stem cells because, in several instances, different secondary recipients displayed in their marrow, spleen, thymus and day 14 spleen colony-forming cells the same proviral integration pattern as the primary recipient. Neither primary engraftment nor marking efficiency varied for stem cells cultured in IL-3 + IL-6, IL-3 + IL-6 + KL, IL-3 + IL-6 + LIF, or all four factors, but those cultured in IL-3 + IL-6 + LIF appeared to have lower secondary engraftment potential. Provirus expression was detected in 72% of the strongly marked mice, albeit often at low levels. Highly efficient retroviral marking of purified lymphomyeloid repopulating stem cells should enhance studies of stem cell biology and facilitate analysis of genes controlling hematopoietic differentiation and transformation. 相似文献
84.
Soubhagya R. Nayak Ashwin Krishnamurthy SJ Madhan Kumar Latha V. Prabhu Bhagath Kumar Potu Sujatha D’Costa Anu Vinod Ranade 《Hand (New York, N.Y.)》2010,5(1):31-36
The superficial palmar arch (SPA) and its contributing arteries are highly variable. The palmar type of median artery (PMA)
can be involved in the formation of the SPA by replacing the superficial palmar branch of the radial artery (RA) or the ulnar
artery (UA). The present study was undertaken to investigate the presence of the PMA and its contribution in the formation
of SPA in 42 cadavers (84 upper limbs) of Indian origin. When there was a PMA, its outer diameter was measured in the carpal
tunnel. The PMA was found in 13 upper limbs (15.4%), and of these ten incidences (11.9%), the PMA took part in the formation
of SPA, and in three instances (3.5%), the PMA did not make up part of the SPA. Out of the ten cases in which the PMA contributed
to the formation of SPA, in six cases (7.1%), the PMA anastomosed with the UA; in three cases (3.5%), the PMA anastomosed
with both the UA and the RA, and in one incidence (1.1%), the PMA joined the arteria radialis indicis (deep branch of the
RA) to complete the SPA. The outer diameters of the median arteries varied between 0.8 and 2.6 mm with the mean value of 1.7 mm.
The present study concludes that the median–ulnar type of SPA was the most common type of SPA when the PMA was encountered
as a source of superficial arterial arcade of the hand, followed by the radial–median–ulnar type. The vascular patterns found
in this study are important to hand surgeons. The present study of PMA origin, course, and its contribution to the SPA will
add to the existing knowledge of the vascular anatomy of forearm and hand. 相似文献
85.
Summary The purpose of this study was to evaluate the occurrence of superficial flaws after machining and to identify fracture initiation and propagation in three‐unit heat‐treated machined fixed partial dentures (FPDs) substructures made of hot isostatic pressed (HIPed) yttria‐stabilized tetragonal zirconia polycrystal (Y‐TZP) after loaded to fracture. Four three‐unit HIPed Y‐TZP‐based FPDs substructures were examined. To evaluate the occurrence of superficial flaws after machining, the surfaces were studied utilizing a fluorescent penetrant method. After static loading to fracture, characteristic fracture features on both mating halves of the fractured specimens were studied using a stereomicroscope and a scanning electron microscope. Grinding grooves were clearly visible on the surfaces of the machined FPDs substructures, but no other flaws could be seen with the fluorescent penetrant method. After loading to fracture, the characteristic fracture features of arrest lines, compression curl, fracture mirror, fracture origin, hackle and twist hackle were detected. These findings indicated that the decisive fracture was initiated at the gingival embrasure of the pontic in association with a grinding groove. Thus, in three‐unit heat‐treated machined HIPed Y‐TZP FPDs substructures, with the shape studied in this study, the gingival embrasure of the pontic seems to be a weak area providing a location for tensile stresses when they are occlusally loaded. In this area, fracture initiation may be located to a grinding groove. 相似文献
86.
A. Kyle Jones Raimund Polman Charles E. Willis S. Jeff Shepard 《Journal of digital imaging》2011,24(2):243-255
Rejected images represent both unnecessary radiation exposure to patients and inefficiency in the imaging operation. Rejected
images are inherent to projection radiography, where patient positioning and alignment are integral components of image quality.
Patient motion and artifacts unique to digital image receptor technology can result in rejected images also. We present a
centralized, server-based solution for the collection, archival, and distribution of rejected image and exposure indicator
data that automates the data collection process. Reject analysis program (RAP) and exposure indicator data were collected
and analyzed during a 1-year period. RAP data were sorted both by reason for repetition and body part examined. Data were
also stratified by clinical area for further investigation. The monthly composite reject rate for our institution fluctuated
between 8% and 10%. Positioning errors were the main cause of repeated images (77.3%). Stratification of data by clinical
area revealed that areas where computed radiography (CR) is seldom used suffer from higher reject rates than areas where it
is used frequently. S values were log-normally distributed for examinations performed under either manual or automatic exposure control. The distributions
were positively skewed and leptokurtic. S value decreases due to radiologic technology student rotations, and CR plate reader calibrations were observed. Our data
demonstrate that reject analysis is still necessary and useful in the era of digital imaging. It is vital though that analysis
be combined with exposure indicator analysis, as digital radiography is not self-policing in terms of exposure. When combined,
the two programs are a powerful tool for quality assurance. 相似文献
87.
Long-bone growth in fetuses with Down syndrome 总被引:3,自引:0,他引:3
J FitzSimmons S Droste T H Shepard J Pascoe-Mason A Chinn L A Mack 《American journal of obstetrics and gynecology》1989,161(5):1174-1177
Short stature is a well-recognized component of Down syndrome. The femur lengths of affected fetuses have been observed to be shorter than normal, with a ratio of actual to expected femur length of less than 0.91 indicating a high risk of trisomy. To further evaluate this finding we have determined the relationship between limb lengths and gestational age in 37 postmortem fetal specimens with trisomy 21. Control values were obtained from 174 normal fetuses. Measurements of the femur, tibia, fibula, humerus, radius, and ulna were made from roentgenograms or by direct measurement of the bone. Most measurements for each bone of the affected fetuses fell below the normal regression line for that bone, but only 3/37 femurs, 4/32 tibias, 5/32 fibulas, 9/32 humeri, 10/32 radii, and 7/32 ulnas fell more than 2 SDs below the mean. The ratios of actual to expected femur lengths were computed and six fetuses with Down syndrome (16.2%) had ratios less than 0.91. The bones of the extremities of fetuses with trisomy 21 are shorter than normal, but the differences are relatively small. The ratio of actual/expected femur lengths was a less efficient predictor of Down syndrome than were either maternal age or maternal serum alpha-fetoprotein tests. The upper extremity bones were shorter than normal more often than were the bones of the lower extremity, and this finding should be explored further in a prospective study. 相似文献
88.
Shepard B 《Health and human rights》2000,4(2):110-143
This article examines how political controversies affect citizens' ability to exercise sexual and reproductive rights in Latin America. The article argues that societies accommodate conflicting views on sexuality and reproduction with a "double discourse system," which defends repressive or negligent public policies while privately tolerating unofficial and often illegal mechanisms that expand private sexual and reproductive choices. The examples of divorce policy in Chile and abortion policy in Colombia and Chile are highlighted to illustrate how this breach between public discourse and private actions operates in practice, and who is harmed by it. The article concludes by discussing the implications of this system for rights advocacy. 相似文献
89.
Auditory brain stem response (ABR) testing is widely used to detect lesions of the auditory neural pathways. The ABR waves depend not only on the integrity of the neural pathways, but also on the condition of the cochlea. To properly interpret the ABR response, it is necessary to understand the effects of cochlear hearing loss on the ABR wave latencies. We studied two populations of subjects with cochlear hearing loss: one with varying degrees of high-frequency hearing loss and the other with varying degrees of flat configuration hearing loss. The degree of cochlear hearing loss was quantified in several different ways and subjected to one linear and three nonlinear regression analyses to test for accuracy in predicting ABR wave latencies and interpeak intervals (waves I, III, V, I-V, I-III, and III-V) for three click intensities. Hearing loss levels from 2 to 6 kHz, in particular 4 kHz, were superior to other audiometric test frequencies as predictors of ABR wave latencies for the group with the high-frequency losses. No particular characterization was found to be superior for the flat hearing loss configurations. From these results, modeled predictions of wave latencies as a function of degree and configuration of hearing loss were made. The modeled predictions are then used to suggest guidelines for interpretations of ABR results where hearing impaired patients are involved. 相似文献
90.
Carriage of Haemophilus influenzae and Streptococcus pneumoniae in healthy Chinese and Vietnamese children in Hong Kong 总被引:1,自引:0,他引:1
RYT Sung JM Ling SM Fung SJ Oppenheimer DW Crook JTF Lau AFB Cheng 《Acta paediatrica (Oslo, Norway : 1992)》1995,84(11):1262-1267
Nasopharyngeal carriage of Haemophilus influenzae and Streptococcus pneumoniae was studied in 621 healthy Chinese children and 300 healthy Vietnamese children aged from 2 months to 5 years in Hong Kong. The carriage rate of H, influenzae type b in Vietnamese children was 1.3% (CI 0.04-2.63%); it was zero in Chinese. The carriage rate of non-typable H. influenzae was 5.8% (CI 1.4-7.6%) in Chinese and 65.4% (CI 58.9-69.8%) in Vietnamese. The carriage rates of S. pneumoniae were 10.8% (CI 8.3-13.2%) and 55.7% (CI 50.1-61.3%) in Chinese and Vietnamese children, respectively. Univariate and multivariate logistic regression analyses were performed to search for factors associated with differences in carriage rates of both H. influenzae and S. pneumoniae between Chinese and Vietnamese children. Although older age, smaller living area and parental smoking were associated with higher carriage rates, these could not explain the remarkably low carriage rates of both bacteria in Chinese children. 相似文献