全文获取类型
收费全文 | 35749篇 |
免费 | 2314篇 |
国内免费 | 107篇 |
专业分类
耳鼻咽喉 | 503篇 |
儿科学 | 872篇 |
妇产科学 | 485篇 |
基础医学 | 4329篇 |
口腔科学 | 486篇 |
临床医学 | 3948篇 |
内科学 | 7234篇 |
皮肤病学 | 434篇 |
神经病学 | 3184篇 |
特种医学 | 1442篇 |
外科学 | 5922篇 |
综合类 | 413篇 |
一般理论 | 41篇 |
预防医学 | 3201篇 |
眼科学 | 586篇 |
药学 | 2698篇 |
中国医学 | 30篇 |
肿瘤学 | 2362篇 |
出版年
2024年 | 27篇 |
2023年 | 255篇 |
2022年 | 491篇 |
2021年 | 1111篇 |
2020年 | 651篇 |
2019年 | 1001篇 |
2018年 | 1196篇 |
2017年 | 827篇 |
2016年 | 843篇 |
2015年 | 1006篇 |
2014年 | 1531篇 |
2013年 | 1985篇 |
2012年 | 2869篇 |
2011年 | 2940篇 |
2010年 | 1533篇 |
2009年 | 1422篇 |
2008年 | 2450篇 |
2007年 | 2401篇 |
2006年 | 2212篇 |
2005年 | 2226篇 |
2004年 | 2107篇 |
2003年 | 1878篇 |
2002年 | 1742篇 |
2001年 | 241篇 |
2000年 | 210篇 |
1999年 | 263篇 |
1998年 | 329篇 |
1997年 | 249篇 |
1996年 | 249篇 |
1995年 | 173篇 |
1994年 | 181篇 |
1993年 | 153篇 |
1992年 | 136篇 |
1991年 | 102篇 |
1990年 | 90篇 |
1989年 | 98篇 |
1988年 | 86篇 |
1987年 | 80篇 |
1986年 | 68篇 |
1985年 | 76篇 |
1984年 | 72篇 |
1983年 | 79篇 |
1982年 | 87篇 |
1981年 | 56篇 |
1980年 | 38篇 |
1979年 | 42篇 |
1978年 | 33篇 |
1977年 | 34篇 |
1975年 | 31篇 |
1974年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Cardiac imaging in the evaluation of patients presenting to the emergency department with chest pain
Conclusions Despite the utility and benefits that each imaging modality has to offer, it is easy to see why there is still no perfect
choice for a noninvasive cardiac imaging modality to assist in the management of chest pain patients. All of the current imaging
techniques have their own significant strengths and weaknesses when compared with other modalities. SPECT and echocardiography
are wellestablished technologies that can directly assess the presence of myocardial ischemia and its functional consequence
on RF; newer and more expensive techniques such as MDCT and CMR can directly assess coronary anatomy and have just started
to be evaluated in the acute chest pain setting. There are no studies that directly compare these technologies, and more data
are clearly needed before the question of whether anatomic imaging versus perfusion/function imaging is the better approach
can be answered. Other comparisons such as relative safety, availability, logistics, and cost-effectiveness between the various
technologies are also lacking.
Of all of the imaging modalities discussed, MCE is the only portable technology. The images do not require expensive software
or other technology for offline processing before interpretation, and any trained cardiologist can read the study at the bedside
or, potentially, over the Internet, providing near-instantaneous results in the acute cardiac setting, where time is of the
essence.
MCE is also relatively cheap compared with other technologies, a potential advantage for payors but not necessarily for payees.
How reimbursement rates and fee structures eventually affect clinical practice is also unknown.
Despite these and other questions that need to be answered before any one technique will be used exclusively, the future of
noninvasive cardiac imaging remains an exciting and ever-changing field. The adaptation of any one of these techniques into
its proper role in the ED Journal of Nuclear Cardiology Wyrick and Wei 753 Volume 13, Number 6;749-55 Cardiac imaging in patients
with chest pain will take considerably more time and effort in terms of research, money, and time-tested clinical experience. 相似文献
42.
Smith Kevin C. BA BSc MD FACP FRCPC Melnychuk Michael BSc DDS 《Dermatologic surgery》2005,31(S4):1635-1637
Background. Injection of filler substances into the lips is painful, and many patients also find the injection of local or regional anesthesia into the lips painful.
Objective. To develop a highly effective and painless form of anesthesia to facilitate injection of filler substances into the lips.
Methods. Five percent lidocaine cream was applied simultaneously to the skin, vermilion, and mucosa of the lips (with the use of a barrier to keep the cream in contact with the mucosa and out of the rest of the mouth) for 20 to 30 minutes.
Results. Profound anesthesia of the lips was reliably produced, with no complications.
Conclusions. This "anesthetic cream block" is easier to perform and better tolerated than injectable anesthetics. Use of this technique is likely to expand the range of physicians who perform filler injections on the lips and will probably also expand the range of patients who wish to have filler injections done on their lips and who (because they had little or no discomfort) are willing to return for additional filler injections in the future. 相似文献
Objective. To develop a highly effective and painless form of anesthesia to facilitate injection of filler substances into the lips.
Methods. Five percent lidocaine cream was applied simultaneously to the skin, vermilion, and mucosa of the lips (with the use of a barrier to keep the cream in contact with the mucosa and out of the rest of the mouth) for 20 to 30 minutes.
Results. Profound anesthesia of the lips was reliably produced, with no complications.
Conclusions. This "anesthetic cream block" is easier to perform and better tolerated than injectable anesthetics. Use of this technique is likely to expand the range of physicians who perform filler injections on the lips and will probably also expand the range of patients who wish to have filler injections done on their lips and who (because they had little or no discomfort) are willing to return for additional filler injections in the future. 相似文献
43.
An ecologically based examination of barriers to physical activity in students from grade seven through first-year university 总被引:1,自引:0,他引:1
Nancy C. Gyurcsik Ph.D. Kevin S. Spink Ph.D. Steven R. Bray Ph.D. Karen Chad Ph.D. Matt Kwan B.Sc. 《The Journal of adolescent health》2006,38(6):704-711
PurposeThe first purpose was to identify barriers to physical activity that students in grade seven through first-year university experienced. A second purpose was to classify barriers using an ecological framework and to examine the pattern of barrier categories (i.e., intrapersonal, interpersonal, institutional, community, public policy, and physical environmental) and specific barrier types as grade increased. The use of an ecological model addressed limitations in prior research revolving around the identification of salient barriers in a manner that makes the design of effective interventions difficult.MethodsParticipants in grades 7–8 (n = 35), 9–10 (n = 67), 11–12 (n = 80), and the freshmen year of university (n = 109) listed barriers to physical activity on an open-ended measure.ResultsFindings revealed a trend for the average number of barriers reported per student to increase as grade in school increased. First-year university students reported significantly more barriers than all other grade groupings. The frequency of barriers reported within the ecological categories was dependent on the specific grade groupings. Further, within each ecological category, distinct barriers were reported across the different grade groupings.ConclusionsFindings highlight the utility of using an ecological model to categorize barriers, rather than simply classifying barriers as internal or external to an individual, as done in prior research. Understanding the pattern of ecologically based barrier categories and specific types of barriers will help to inform the content of future research and interventions designed to alleviate salient barriers to physical activity. 相似文献
44.
45.
Rakel Kling Marc Corbière Rebecca Milord Janet G Morrison Kevin Craib Annalee Yassi Claire Sidebottom Catherine Kidd Victoria Long Sharon Saunders 《AAOHN journal》2006,54(11):481-487
This study examined the use and effectiveness of the Alert assessment form. The form is part of the Alert system, used by one large acute care hospital to identify patients with a propensity for violence. All reported incidents of patient violence from August 1, 2003, through December 31, 2004, were included in patient charts. One hundred seventeen violent patient charts were reviewed and compared with 161 non-violent patient charts, randomly chosen from the same time period. Overall use of the Alert assessment form for violent and non-violent patients was 75.7% and 35.4%, respectively. The assessment form was found to have moderate sensitivity (71%) and high specificity (94%). It is reasonably effective in identifying potentially violent or aggressive patients when it is used according to protocol. Efforts to improve the tool are warranted, as is evaluation of its benefit in settings with low prevalence of violence. Also, greater effort must be taken to prevent violence once an aggressive patient has been identified. 相似文献
46.
47.
Kevin G Becker Insong J Lee James W Nagle Rachel D Canning Ameer M Gado Rosarelis Torres Mihael H Polymeropoulos Paul T Massa WilliamE Biddison Paul D Drew 《International journal of developmental neuroscience》1997,15(7):73
We describe a novel human zinc finger cNDA, C2H2-171. This cDNA represents an mRNA which encodes a protein of 484 amino acids and a calculated molecular weight of 54 kD. Four zinc finger-like domains are found in the C-terminal end of the protein. At the N-terminus, C2H2-171 contains a POZ/tramtrack-like domain similar to that found in the tumor associated zinc finger proteins LAZ-3/BCL-6 and PLZ-F, as well as in non-zinc finger proteins. C2H2-171 RNA is preferentially expressed in the brain, and increases during the course of murine development, with maximal expression in the adult. C2H2-171 RNA is differentially expressed in brain regions, with the highest level of expression in the cerebellum. C2H2-171 RNA was expressed at high levels in primary cerebellar granule cell neurons compared to astrocytes. The gene encoding C2H2-171 is highly conserved in vertebrates, and maps to the terminus of human chromosome 1 (1q44-ter). This chromosomal location is associated with a number of cytogenetic aberrations including those involving brain developmental anomalies and tumorigenesis. These data suggest that C2H2-171 may play an important role in vertebrate brain development and function. 相似文献
48.
K. H. McAllister 《Psychopharmacology》1994,116(3):317-325
D-Cycloserine (DCS) has been reported to affect the central nervous system in man. To investigate whether the compound produces specific behavioural effects, DCS was administered to male mice in a resident-intruder situation and the behaviour of the interacting mice assessed using ethological analysis. Resident mice given DCS (32.0–320.0 mg/kg PO, 60 min before testing) showed dose-dependent increases in social investigation, smaller increases in sexual behaviour and decreased aggressiveness. Defensive and flight behaviour were not affected. Intruder mice showed slight increases in sexual behaviour that were not dose-dependent, and small increases in social investigation. The increases in social investigation induced by DCS (320.0 mg/kg) in resident mice were not reversible with R-HA 966 (32.0 mg/kg IP, 30 min before testing), a blocker of the strychnine-insensitive glycine modulatory site associated with theN-methyl-D-aspartate receptor, but were blocked by the GABA antagonist bicuculline (0.56 mg/kg IP, 5 min before testing). The small DCS-induced increase in sexual behaviour in residents was reversed by R-HA 966. Within the parameters of the resident-intruder situation, DCS exerts socio-sexual behaviour-enhancing effects which are dependent upon the role of the interactant, and which are mediated by an action upon multiple substrates. DCS may be regarded as another example of a sociotropic (approach-promoting) agent.Some of these results have been presented at the 1st International Congress on Hormones, Brain and Neuropsychopharmacology, Rodos, Greece, September 12–17, 1993 相似文献
49.
Canadian Journal of Anesthesia/Journal canadien d'anesthésie - 相似文献
50.
Christina M Marra Clare L Maxwell Ann C Collier Kevin R Robertson Allison Imrie 《BMC infectious diseases》2007,7(1):37