全文获取类型
收费全文 | 1864篇 |
免费 | 145篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 35篇 |
儿科学 | 82篇 |
妇产科学 | 48篇 |
基础医学 | 237篇 |
口腔科学 | 38篇 |
临床医学 | 186篇 |
内科学 | 360篇 |
皮肤病学 | 35篇 |
神经病学 | 160篇 |
特种医学 | 211篇 |
外科学 | 219篇 |
综合类 | 57篇 |
一般理论 | 2篇 |
预防医学 | 161篇 |
眼科学 | 10篇 |
药学 | 96篇 |
中国医学 | 7篇 |
肿瘤学 | 75篇 |
出版年
2023年 | 11篇 |
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 20篇 |
2017年 | 13篇 |
2016年 | 41篇 |
2015年 | 65篇 |
2014年 | 44篇 |
2013年 | 57篇 |
2012年 | 67篇 |
2011年 | 68篇 |
2010年 | 51篇 |
2009年 | 52篇 |
2008年 | 53篇 |
2007年 | 45篇 |
2006年 | 70篇 |
2005年 | 70篇 |
2004年 | 49篇 |
2003年 | 62篇 |
2002年 | 52篇 |
2001年 | 47篇 |
2000年 | 51篇 |
1999年 | 40篇 |
1998年 | 38篇 |
1997年 | 52篇 |
1996年 | 45篇 |
1995年 | 32篇 |
1994年 | 32篇 |
1993年 | 28篇 |
1992年 | 46篇 |
1991年 | 48篇 |
1990年 | 47篇 |
1989年 | 59篇 |
1988年 | 54篇 |
1987年 | 44篇 |
1986年 | 49篇 |
1985年 | 44篇 |
1984年 | 38篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 13篇 |
1980年 | 24篇 |
1979年 | 28篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1976年 | 10篇 |
1974年 | 17篇 |
1972年 | 11篇 |
1970年 | 10篇 |
排序方式: 共有2019条查询结果,搜索用时 15 毫秒
31.
Ultimate tensile strength of dentin: Evidence for a damage mechanics approach to dentin failure 总被引:2,自引:0,他引:2
Staninec M Marshall GW Hilton JF Pashley DH Gansky SA Marshall SJ Kinney JH 《Journal of biomedical materials research》2002,63(3):342-345
Dentin structure and properties are known to vary with orientation and location. The present study explored the variation in the ultimate tensile strength (UTS) of dentin with location in the tooth. Hourglass specimens were prepared from dentin located in the center, under cusps, and in the cervical regions of human molar teeth. These were tested in tension at various distances from the pulp. Median tensile strengths ranged from 44.4 MPa in the inner dentin near the pulp, to 97.8 MPa near the dentino-enamel junction (DEJ). This increase in the median UTS with distance from the pulp to the DEJ was statistically significant (P <.001). Of particular importance was the observation that the UTS measurements followed a Weibull probability distribution, with a Weibull modulus of about 4.5. The Weibull behavior of the UTS data strongly suggests that the large variances in fracture strength data result from a distribution of preexisting defects in the dentin. These findings justify a damage-mechanics approach to studies of dentin failure. 相似文献
32.
33.
34.
目的;探讨手术治疗胸椎结核的更好方法。方法;自1990年以来,对21例胸椎结核导致椎柱不稳的患者,应用病灶清除,哈氏棒内固定,椎间及椎板植骨的手术方法。本组平均33.2岁。胸7椎体6例,胸8椎体8例,胸10椎体7例,椎体压缩〈1/2椎体高度13例,〉1/2椎体高度8例,并不全瘫14例。手术中先行病灶清除,然后哈氏棒内固一,撑开后再次清除病灶,取肋骨和髂骨行椎间及椎板上植骨。术后化疗12~15月。结 相似文献
35.
Rationale: The neurochemical effects of psychostimulant exposure may depend on how these drugs are encountered. A useful method for examining
this issue is to compare neurotransmitter release following response-dependent, or self-administered, drug exposure and response-independent
exposure. Objectives: This experiment examined the effect of active and passive cocaine administration on acetylcholine (ACh) efflux in the shell
region of the nucleus accumbens (NAc) in rats. Methods: One group of rats (CSA: cocaine self-administration) was trained to lever-press for intravenous infusions of cocaine (0.42
mg/kg per infusion) on a fixed-ratio-1 schedule of reinforcement. Cocaine infusions were accompanied by the onset of a stimulus
light that signaled a 20-s time-out period. Control rats received intravenous cocaine (cocaine non-contingent: CNC) or saline
(SAL) in a manner that was not contingent upon their behavior. Drug infusions in these groups were determined by the lever-press
behavior of the animals in the CSA group, i.e. they were yoked to rats in the self-administration group such that CNC animals
received equal amounts of cocaine as CSA rats. Animals received cocaine or saline in 3-h sessions for 13 consecutive days
before testing. On day 14, extracellular ACh was measured in 15-min intervals before, during and after a 3-h session of cocaine
exposure using unilateral microdialysis probes located in the NAc shell coupled with HPLC. Results: ACh efflux was significantly increased above baseline in both groups of rats that received cocaine but CSA rats had significantly
higher ACh levels during the self-administration period compared to their yoked counterparts. In addition, ACh efflux remained
elevated longer in CSA animals relative to CNC rats following cessation of cocaine exposure. Conclusions: These results demonstrate that ACh interneurons in the NAc shell are responsive to cocaine exposure. In addition, these findings
suggest that the manner in which the drug is administered (i.e. either by active self-administration or passive exposure)
may be relevant to the magnitude of the neural response.
Received: 28 April 1998 / Final version: 4 November 1998 相似文献
36.
Free fatty acid mobilization and oxidation during total parenteral nutrition in trauma and infection. 总被引:7,自引:2,他引:5 下载免费PDF全文
J Nordenstrm Y A Carpentier J Askanazi A P Robin D H Elwyn T W Hensle J M Kinney 《Annals of surgery》1983,198(6):725-735
Free fatty acid (FFA) metabolism was studied in 18 traumatized and/or septic patients. Each patient was studied while receiving 5% dextrose (D5W) and after 4 to 7 days of total parenteral nutrition (TPN). Nonprotein energy during TPN was given either entirely as glucose (Glucose System) or as equal portions of intravenous fat and glucose (Lipid System). Plasma FFA concentrations were in the normal range on D5W and decreased markedly with TPN. FFA turnover was higher than normal on D5W and did not decrease significantly with TPN. The poor correlation between these two variables emphasizes the need to perform kinetic studies to characterize FFA metabolism in trauma and sepsis. Plasma FFA oxidation and net whole body fat oxidation measured by indirect calorimetry were in the normal range on D5W, 35 and 82%, respectively, of resting energy expenditure (REE). With a glucose intake averaging 108% of REE, plasma FFA oxidation and net fat oxidation decreased to 17 and 13%, respectively, of REE. Nonprotein RQ increased only to 0.94 despite administration of glucose in excess of REE, indicating an abnormal persistence of fat oxidation. During D5W administration, plasma FFA accounted for less than one half of total fat oxidation, indicating that unlabeled fat, such as tissue or plasma triglycerides not in rapid equilibrium with plasma FFA, accounted for the bulk of fat oxidation. Glucagon concentrations which were high on D5W did not decrease significantly with TPN. Insulin concentrations were normal on D5W and increased in response to TPN. The abnormal hormonal milieu may account for much of the abnormal fat metabolism. Administration of large amounts of glucose decreased FFA oxidation much more than FFA mobilization. Thus, the infused glucose acts to increase the rate of "futile cycling" of FFA in these acutely ill patients. 相似文献
37.
Regina K. Kinney Robert J. Gatchel Peter B. Polatin Tom G. Mayer 《Journal of occupational rehabilitation》1991,1(3):235-243
The functional restoration approach to treating chronic spinal disability consists of a medically directed, interdisciplinary team approach to physical reconditioning and a cognitive-behavioral crisis intervention procedure for dealing with related psychosocial problems. One- and two-year follow-up studies have demonstrated the clinical efficacy of this approach. The present article describes this approach and summarizes the research documenting its success in treating patients with chronic spinal disability. This article also highlights the pitfalls in misunderstanding and misrepresenting the components of the functional restoration approach when evaluating treatment efficacy. 相似文献
38.
The authors reviewed the literature to assess the relationship between psychological factors and gastrointestinal conditions. The conditions that were found to be more relevant and worthy of future investigation were nonulcerative dyspepsia, inflammatory bowel disease (regional enteritis), and irritable bowel syndrome. The pertinent findings suggest that an important link exists between psychological factors and gastroenterological disorders, which supports the need for modification of the DSM-III-R's diagnostic category, "Psychological Factors Affecting Physical Condition." In concert with a subcommittee addressing other organ systems and psychological factors, the authors conclude that a diagnostic approach with greater utility would be useful for both researchers and clinicians. A conceptual framework as proposed in DSM-IV could also advance knowledge of psychological factors and their contribution or role in the etiology, perpetuation, and exacerbation of certain gastrointestinal conditions. 相似文献
39.
OBJECTIVES: To investigate maternal knowledge and attitudes about otitis media (OM) risk, to estimate the prevalence of risk factors in the first year of life, and to identify barriers to the reduction of risk factors (eg, formula feeding, day care attendance, and exposure to passive smoke). METHODS: Questionnaires mailed to a systematic sample of 504 Minnesota women >/=18 years old identified through 1994 birth certificates. RESULTS: Eighty percent returned a completed survey. According to maternal report, 29% of infants (age 8 to 13 months) had recurrent OM (>/=3 episodes) and 2% had tympanostomy tubes. Forty-six percent attended day care, 29% had >/=1 smoking parent, and 49% breastfed for =2 months. Women were more knowledgeable about OM signs and symptoms than about risk factors. Mean OM knowledge score (the sum of correct true-false responses) was 7.0 (standard deviation = 1.6). Using multiple linear regression, knowledge score was significantly related to marital status, education, age, area of residence, breastfeeding (months), and number of cigarettes smoked per day by the mother, but not to infant or sibling OM history or day care attendance (R = .23). Infant history of OM (odds ratio, 1.9; 95% confidence interval, 1.1 to 3.2) and white race (odds ratio, 0.3; 95% confidence interval, 0. 1 to 0.8), but not the presence of risk factors, were significantly related to having received clinicians' advice about OM prevention advice. CONCLUSION: OM education and prevention programs should target pregnant women and new mothers with OM risk factors, and those who are young, single, and less educated. 相似文献
40.
Dietary polyamines promote the growth of azoxymethane-induced aberrant crypt foci in rat colon 总被引:1,自引:1,他引:1
We have examined whether dietary polyamines influence the formation and
initial growth of azoxymethane (AOM)-induced aberrant crypt foci (ACF) in
rat colon. Effects of a combination of dietary polyamines at three dose
levels (putrescine: 50, 280, 740 nmol/g; spermidine: 10, 261, 763 nmol/g;
spermine: 1, 31, 91 nmol/g) in the polyamine-poor AIN-76A diet were studied
in animals in two different experimental situations: animals treated with
AOM alone and animals treated with AOM + difluoromethylornithine (DFMO), a
specific inhibitor of endogenous polyamine synthesis. In both experimental
situations, dietary polyamines enhanced the growth of ACF, expressed as the
number of large ACF (foci with three or more aberrant crypts, ACF > or =
3), whereas the formation of ACF, expressed as the number of ACF, was
apparently not altered. In animals treated with AOM alone, maximal growth
enhancing effect on ACF was nearly obtained with the median level of
dietary polyamine. In rats fed a low polyamine diet, basic AIN-76A, DFMO
reduced the growth of AOM-induced ACF by 83%. This inhibitory effect of
DFMO was counteracted by dietary polyamines in a dose- dependent manner,
and it was abolished at the highest level of polyamines. In conclusion, it
was demonstrated that dietary polyamines are able to enhance the growth of
AOM-induced ACF. Further, dietary polyamines reversed the DFMO-caused
inhibition of ACF growth, probably by compensating for the DFMO-reduced
endogenous polyamine synthesis.
相似文献