全文获取类型
收费全文 | 1468篇 |
免费 | 106篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 9篇 |
儿科学 | 77篇 |
妇产科学 | 21篇 |
基础医学 | 181篇 |
口腔科学 | 33篇 |
临床医学 | 191篇 |
内科学 | 292篇 |
皮肤病学 | 23篇 |
神经病学 | 164篇 |
特种医学 | 22篇 |
外科学 | 148篇 |
综合类 | 10篇 |
一般理论 | 1篇 |
预防医学 | 274篇 |
眼科学 | 14篇 |
药学 | 59篇 |
中国医学 | 4篇 |
肿瘤学 | 55篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 50篇 |
2020年 | 21篇 |
2019年 | 33篇 |
2018年 | 41篇 |
2017年 | 36篇 |
2016年 | 36篇 |
2015年 | 46篇 |
2014年 | 60篇 |
2013年 | 59篇 |
2012年 | 87篇 |
2011年 | 107篇 |
2010年 | 60篇 |
2009年 | 54篇 |
2008年 | 78篇 |
2007年 | 81篇 |
2006年 | 98篇 |
2005年 | 91篇 |
2004年 | 80篇 |
2003年 | 78篇 |
2002年 | 61篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 13篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1973年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有1578条查询结果,搜索用时 28 毫秒
21.
This study demonstrates the importance of using a complete set of 16 reciprocal crosses (F1, backcrosses, and F2) to thoroughly investigate both genetic and nongenetic influences on patterns of inheritance of larval pupation behavior inDrosophila melanogaster. Larvae derived from natural populations show significant variation in pupal height, defined as the distance a larva pupates above the feeding substrate. Differences in the distance a larva pupates from fruit in nature is known to affect the fitness ofDrosophila populations. In this study the heredity of pupal height is analyzed by performing crosses between high- and low-pupating strains. We found that the inheritance of pupal height fit a classical additive polygenic model of inheritance, with intermediate F1 pupal heights and greater variances in the F2 generation. In addition, a significant maternal effect was also found by analyzing the reciprocal backcrosses. Progeny with low-pupating mothers had lower pupation heights than those with low-pupating fathers. Similarly, progeny with high-pupating mothers tended to have higher pupal heights than those with high-pupating fathers. This maternal effect was not attributable to strain differences in permanent cytoplasmic factors, sex chromosomes, or developmental time. Finally, we speculate upon the environmental conditions under which a transient maternal effect on pupation behavior would be expected to evolve in natural populations.This work was supported by a University Research Fellowship and Operating Grant from the Natural Sciences and Engineering Research Council to M. B. Sokolowski. S. J. Bauer was the recipient of an Ontario Graduate Scholarship. 相似文献
22.
23.
Pyle MA Jasinevicius TR Lalumandier JA Kohrs KJ Sawyer DR 《General dentistry》1999,47(5):500-3; quiz 504-5
The occurrence of retromolar foramina (RMF) was examined in a sample of dry skulls (African American n = 249; Causcasian n = 226) to consider the potential clinical impact. A prevalence rate of 7.8% of RMF was found. There were no statistical differences based on race or gender. The prevalence may contribute to the explanation of a portion of inferior alveolar nerve block failures and provide insight into potential implications of surgery in the posterior mandible. 相似文献
24.
The effects of cocaine on speech sound discriminations was examined to determine whether cocaine's previously demonstrated effect in reducing speech sound discriminability was dependent upon either the type of stimuli employed (simple tones versus complex speech) or the procedure (stimulus detection versus stimulus discrimination). Because of demonstrated similarities in the way that baboons and humans discriminate speech, and in the way the CNS is thought to encode and process speech sounds in these two species, baboons were trained to perform a choice procedure to identify the occurrence of different synthetic vowel sounds (/a/, /æ/, //, /U/, and /љ/). Animals held down a lever and released the lever only when one of four target vowels sounded, and not when a fifth, standard vowel sounded. Acute IM administration of cocaine (0.0032–1.0 mg/kg) produced dose-dependent decreases in vowel discriminability that were mostly due to elevations in false alarms (i.e., releases to the standard vowel) following cocaine. Cocaine also shortened reaction times to the stimuli in two of three baboons, but to a much lesser extent than observed previously. These results suggest that cocaine may interfere with the ability of the CNS to process the acoustic cues in speech sounds, and that the effects of cocaine on reaction times may depend upon the complexity of the reaction time procedure employed. 相似文献
25.
Differential response of human ovarian cancer cells to induction of apoptosis by vitamin E Succinate and vitamin E analogue, alpha-TEA. 总被引:2,自引:0,他引:2
Kristen Anderson Marla Simmons-Menchaca Karla A Lawson Jeffrey Atkinson Bob G Sanders Kimberly Kline 《Cancer research》2004,64(12):4263-4269
A vitamin E derivative, vitamin E succinate (VES; RRR-alpha-tocopheryl succinate), and a vitamin E analogue, 2,5,7,8-tetramethyl-2R-(4R,8R,12-trimethyltridecyl)chroman-6-yloxy acetic acid (alpha-TEA), induce human breast, prostate, colon, lung, cervical, and endometrial tumor cells in culture to undergo apoptosis but not normal human mammary epithelial cells, immortalized, nontumorigenic breast cells, or normal human prostate epithelial cells. Human ovarian and cervical cancer cell lines are exceptions, with alpha-TEA exhibiting greater proapoptotic effects. Although both VES and alpha-TEA can induce A2780 and subline A2780/cp70 ovarian cancer cells to undergo DNA synthesis arrest within 24 h of treatment, only alpha-TEA is an effective inducer of apoptosis. VES or alpha-TEA treatment of cp70 cells with 5, 10, or 20 microg/ml for 3 days induced 5, 6, and 19% versus 9, 36, and 71% apoptosis, respectively. Colony formation data provide additional evidence that cp70 cells are more sensitive to growth inhibition by alpha-TEA than VES. Differences in stability of the ester-linked succinate moiety of VES versus the ether-linked acetic acid moiety of alpha-TEA were demonstrated by high-performance liquid chromatography analyses that showed alpha-TEA to remain intact, whereas VES was hydrolyzed to the free phenol, RRR-alpha-tocopherol. Pretreatment of cp70 cells with bis-(p-nitrophenyl) phosphate, an esterase inhibitor, before VES treatment, resulted in increased levels of intact VES and apoptosis. Taken together, these data show alpha-TEA to be a potent and stable proapoptotic agent for human ovarian tumor cells and suggest that endogenous ovarian esterases can hydrolyze the succinate moiety of VES, yielding RRR-alpha-tocopherol, an ineffective apoptotic-inducing agent. 相似文献
26.
This study reports the preliminary results of an outcomes approach to analysis of the effectiveness of endolymphatic sac decompression (ELSD). Using the medical outcomes survey's 36-item, shortform health survey (SF-36), we assessed the quality of life in 33 patients with disabling Meniere's disease undergoing ELSD for medically intractable vertigo. Results indicate that patients with 1995 American Academy of Otolaryngology-Head and Neck Surgery(AAO/HNS) class A or B outcomes showed no significant difference from population norms on the SF-36, whereas patients with AAO/HNS classes C to E outcomes scored significantly below norms. Six patients who were given the SF-36 preoperatively scored consistently below population norms. Postoperatively, they showed a statistically significant improvement and were statistically equal to norms. These findings suggest that the SF-36 is a good measure of the quality of life impairment in patients with disabling Meniere's disease. In addition, SF-36 scores correlated well with the 1995 AAO/HNS classification. 相似文献
27.
Kindergarten has become increasingly academic in nature. One of the primary dilemmas arising from this shift is the tension between the use of developmentally appropriate practices and the obligation to teach academic standards. To gain a deeper understanding of how kindergarten is enacted in the evolving curricular landscape, we look beyond these competing perspectives to develop a theoretical framework informed by Schwab's conception of the eclectic and the four commonplaces. We re-envision the four commonplaces – subject matter, teacher, milieu, and learner – to align them with contemporary conceptions of educational purposes, practical theory, classroom climate, and childhood. Acknowledging that kindergarten is an eclectic space, we create a robust theoretical framework for researchers interested in classroom research. The application of this framework is explored using an ethnographic methodology that integrates data from classroom observations, teacher interviews, and photo elicitation interviews with the students in one kindergarten classroom. 相似文献
28.
ABSTRACT: BACKGROUND: To evaluate the safety of pegaptanib sodium 0.3 mg intravitreal injection in the treatment of neovascular age-related macular degeneration in subjects with or without diabetes mellitus. METHODS: A pooled, retrospective, analysis was conducted of data from 9 sponsor-administered, randomized, open-label trials. Subjects who received pegaptanib by randomization or change in dose assignment, crossover design, or protocol amendment, were included. Reports of endophthalmitis, increased intraocular pressure, retinal injury, intraocular hemorrhage, traumatic cataract, hypersensitivity reactions, stroke, myocardial infarction, and other arterial thromboembolic events defined by the Antiplatelet Trialists' Collaboration were identified by Medical Dictionary for Regulatory Activities preferred terms. Adverse events were summarized from the first injection to 42 days after the last injection. The incidence of adverse events was stratified by the presence/absence of diabetes. RESULTS: Of 1,586 subjects enrolled, 165 (10.4%) had a history of diabetes mellitus and 1,421 (89.6%) did not. The 2 populations were similar at baseline. Based on the comparison of prespecified ocular, hypersensitivity, and Antiplatelet Trialists' Collaboration event terms, the safety review did not identify any notable differences between the 2 populations. CONCLUSIONS: This retrospective analysis found no increased safety risk resulting from treatment with pegaptanib 0.3 mg in individuals with neovascular age-related macular degeneration and concomitant diabetes mellitus. 相似文献
29.
30.
Vaginal rings for pre-exposure prophylaxis are a female-initiated HIV prevention method that does not require daily or coitally-dependent dosing. As part of a randomized placebo-controlled trial of a tenofovir disoproxil fumarate intravaginal ring, we assessed product acceptability through in-depth interviews with 18 women during and after 14 days of continuous use. Women reported that the ring was comfortable with few side effects, regardless of experimental arm. However, interest in future use by this cohort was modest for several reasons including: low self-perceived HIV risk; concern that use implied promiscuity; potential for interference with relationship formation and trust; concern for interference with menstruation and cleanliness; and worries about partners’ acceptability and sexual pleasure. Potential issues were raised with duration of use prior to ring exchange. Future studies should continue to identify and address individual and relationship factors that influence acceptability, early in the product development process. 相似文献