全文获取类型
收费全文 | 1440篇 |
免费 | 95篇 |
国内免费 | 4篇 |
专业分类
耳鼻咽喉 | 55篇 |
儿科学 | 41篇 |
妇产科学 | 23篇 |
基础医学 | 153篇 |
口腔科学 | 45篇 |
临床医学 | 152篇 |
内科学 | 298篇 |
皮肤病学 | 11篇 |
神经病学 | 68篇 |
特种医学 | 25篇 |
外科学 | 246篇 |
综合类 | 21篇 |
一般理论 | 2篇 |
预防医学 | 224篇 |
眼科学 | 14篇 |
药学 | 38篇 |
肿瘤学 | 123篇 |
出版年
2023年 | 5篇 |
2022年 | 25篇 |
2021年 | 38篇 |
2020年 | 20篇 |
2019年 | 31篇 |
2018年 | 52篇 |
2017年 | 30篇 |
2016年 | 23篇 |
2015年 | 31篇 |
2014年 | 43篇 |
2013年 | 63篇 |
2012年 | 115篇 |
2011年 | 90篇 |
2010年 | 52篇 |
2009年 | 49篇 |
2008年 | 83篇 |
2007年 | 83篇 |
2006年 | 68篇 |
2005年 | 76篇 |
2004年 | 70篇 |
2003年 | 66篇 |
2002年 | 60篇 |
2001年 | 33篇 |
2000年 | 23篇 |
1999年 | 26篇 |
1998年 | 8篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 22篇 |
1991年 | 15篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1966年 | 6篇 |
1940年 | 8篇 |
排序方式: 共有1539条查询结果,搜索用时 15 毫秒
1.
Clanton C. Shipp Paul S. Berger Manya S. Deehr Bess Dawson-Hughes M.D. 《Calcified tissue international》1988,42(5):287-292
Summary Precision of dual-photon absorptiometry (DPA) measurements was determined in a lumbar spine phantom and in humans. Approximately
half of the measurements were made before and half after a153gadolinium source change. The phantom was measured with different amounts of acrylic, which simulates human soft tissue, in
order to evaluate the influence of body thickness on bone mineral density (BMD). Results of scans analyzed with two software
versions from Lunar Radiation Corp., the widely used 08B and a prototype 08C, are compared. DPA with a cold source significantly
overestimated BMD in the phantom in the presence of large amounts (more than 25 cm) of soft tissue equivalent with version
08B but not with the newer version 08C. Similiarly, in nine subjects, there was a significant decrease in spine BMD after
a source change when scans were analyzed with version 08B (mean difference 0.026 g/cm2,P=0.002) but not with 08C (0.01 g/cm2,P=0.234). No systematic effect of source change on femoral BMD measurements was observed. The SD of the mean difference of
two measurements of the nine subjects was 0.019 g/cm2 (1.6% of the mean value) for the spine with software version 08B and 0.024 g/cm2 (2.0%) with version 08C, 0.03 g/cm2 (3.3%) for the femur neck, 0.03 g/cm2 (4.0%) for the greater trochanter, and 0.04 g/cm2 (4.9%) for Ward's triangle region of the proximal femur. The spine phanton was scanned on two other commercial bone densitometers
in order to assess inter-instrument variation. Phantom measurements of L2-4 BMD made on two Lunar Radiation Corp model DP3
scanners which differed by 2% were 10 and 12% higher than those with a Norland Corp. model 2600 scanner. 相似文献
2.
S W Pyle B Morein J W Bess L Akerblom P L Nara S M Nigida N W Lerche W G Robey P J Fischinger L O Arthur 《Vaccine》1989,7(5):465-473
In mice, immunostimulatory complexes (ISCOMs) prepared from HIV-1 B external envelope glycoprotein (gp120) induced 10-fold higher antibody titres than gp120 emulsified in depot adjuvant, as measured by enzyme-linked immunosorbent assay (ELISA). Rhesus monkeys immunized with gp120 ISCOMs produced precipitating and virus neutralizing antibody titres equivalent to those seen in HIV-infected chimpanzees and humans. After multiple immunizations with HIV-1 B gp120 ISCOMs, a rhesus monkey developed a neutralizing response to the HIV-1 isolates RF and MN, but not to the CC isolate. Antisera from ISCOM-immunized rhesus monkeys recognized gp120 on the membranes of HIV-1 B-infected H9 cells, indicating the preservation of epitope structure in the ISCOMs matrix. 相似文献
3.
M Wood J Uetrecht J M Phythyon S Shay B J Sweetman O Shaheen A J Wood 《Anesthesia and analgesia》1986,65(5):481-488
Because the H2-receptor antagonist cimetidine has been shown to inhibit drug metabolism, the effects of cimetidine on anesthetic metabolism and toxicity were investigated in a rat model. Cimetidine decreased inorganic plasma fluoride production after methoxyflurane administration both in 21% oxygen (P less than 0.001) and in 100% oxygen (P less than 0.001). Phenobarbital produces an increased fluoride formation after methoxyflurane anesthesia, and this fluoride formation is also reduced by cimetidine (P less than 0.005). There was no significant difference between the plasma fluoride levels in rats anesthetized with halothane or enflurane. Although cimetidine inhibited the in vivo defluorination of methoxyflurane, fluoride levels were still within the nephrotoxic range, and cimetidine is not likely to play a role as part of a preanesthetic regimen that would permit the increased clinical use of methoxyflurane. Cimetidine also inhibited the oxidative metabolism of halothane; cimetidine decreased (P less than 0.05) trifluoroacetic acid concentrations after halothane anesthesia in 21% oxygen and in 100% oxygen and decreased (P less than 0.05) bromide concentrations after halothane anesthesia in 100% oxygen. Trifluoroacetic acid levels were less (P less than 0.02) after halothane anesthesia in 14% oxygen as compared with 100% oxygen, indicating a reduction in oxidative metabolism under hypoxic conditions. However, bromide concentrations were maximal after halothane anesthesia in 21% oxygen, and significantly (P less than 0.001) less after halothane anesthesia in 14% and 100% oxygen. Bromide production, therefore, seems to be inhibited by both hypoxia and hyperoxia.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
4.
S Townson K E Shay A R Dobinson C Connelly J C Comley G Zea-Flores 《Transactions of the Royal Society of Tropical Medicine and Hygiene》1989,83(5):664-669
The viability and drug responses of cryopreserved adult Onchocerca have been examined in vitro. Male worms were cryopreserved in liquid nitrogen (-196 degrees C) using ethanediol as a cryoprotectant in a 2-step incubation procedure. After thawing, 85-90% of O. gutturosa males were normally motile. These motile worms were evaluated for viability using 4 measurements (long-term motility/survival in culture; [U-14C]adenine uptake and leakage; glucose utilization; MTT-formazan colorimetry) and were no different from unfrozen controls. Subsequent experiments demonstrated that the motility responses of cryopreserved worms exposed to the antifilarial drugs ivermectin, CGP 6140 and levamisole were virtually identical to unfrozen controls. Some success was also obtained with this technique in cryopreserving O. volvulus males, with 2 thawed specimens surviving in culture for 93 and 106 d respectively. Following collagenase isolation, female worms were cryopreserved in medium +10% serum without protectant at -79 degrees C. A batch of 8 female O. gutturosa were all motile when thawed 14 d later, with a mean survival time (based on 5 specimens) of 71 d (range 60-90). However, a batch of worms transferred from -79 degrees C to -196 degrees C were badly damaged when thawed. Female O. volvulus were cryopreserved at -79 degrees C in Guatemala and sent by air freight on solid CO2 to the UK. Most specimens were active when thawed. Survival of motile specimens ranged from 7 to 272 d in culture. It is concluded that these techniques are of practical value for the storage and transportation of adult Onchocerca. 相似文献
5.
6.
Objectives/Hypothesis: Numerous mechanical animal models for the creation of otitis media with effusion (OME) have been described since the 1920s. However, there are many problems associated with these models, including high infection rates, unreliability, and high resolution rates. The aim of the current study was to create a suitable mechanical animal model that would produce a sterile and long-lasting effusion. Study Design: A new technique using an external surgical approach on specific pathogen–free rats is described. Method: The eustachian tubes of 56 rats were obstructed in the mid portion along the skull base with gutta percha. Results: All animals developed an effusion within 1 week of the procedure. The resolution rate was 8%, with 80% maintaining sterile effusions for up to 1 year. Conclusions: This new procedure for an OME model has proved consistently reliable in creating a persistent and long-lasting effusion. It has a low infection rate and should benefit future studies on the prolonged effects of OME on the tympanic membrane and middle ear. 相似文献
7.
Marshall Alison L. Bauman Adrian E. Owen Neville Booth Michael L. Crawford David Marcus Bess H. 《Annals of behavioral medicine》2003,25(3):194-202
Background: Intervention trials with self-selected participants have shown that mailed stage-targeted print materials can increase participation
in physical activity in the short term. We examined the effects of a mailed stage-targeted print intervention designed to
promote physical activity, in a random sample of adults living in a regional city.Method: Participants (n = 462, 40–60 years of age) were randomly allocated to an intervention in - 227) or control group (n - 235).
Measures included validated 2-week physical activity recall and stage of motivational readiness for physical activity. The
intervention consisted of a single mailing of a letter and full-color stage-targeted booklets (specific to precontemplation,
contemplation, preparation, and action/maintenance) 1 week postbaseline. Follow-up interviews were conducted at 2 and 6 months
postbaseline.Results: After 2 months, participants in the intervention group were significantly More likely to meet the current American College
of Sports Medicine/Centers for Disease Control and Prevention recommendation for sufficient physical activity than those in
the control group (adjusted odds ratio [OR] - 2.40; 95% confidence interval [CI] = 1.44–3.99). After 6 months, intervention
participants who reported receiving and reading the intervention materials were significantly more likely to be meeting the
sufficient physical activity criterion compared with the control group (adjusted OR = 2.03; 95% Cl = 1.16–3.56).Conclusions: The stage-targeted print intervention was effective in promoting short-term increases in physical activity and was most
effective for participants who recognized and used the materials. This low-cost, generalizable intervention has demonstrated
potential as a practical population-based physical activity promotion strategy. Further research is required before widespread
dissemination would be justified, as additional strategies may be required to ensure sustained change.
This project was supported by a National Heart Foundation of Australia Research Project Grant. David Crawford was supported
by a Nutrition Research fellowship from the National Heart Foundation. 相似文献
8.
9.
Nathan R. Cleveland MD Shay Krier MD Kennon Heard MD 《Academic emergency medicine》2007,14(8):691-694
Background Acute cocaine poisoning is a common problem in the United States. Sedation with benzodiazepines is the standard treatment, but animal studies have suggested that ziprasidone is also protective.
Objectives To assess whether the combination of these two medications would offer more protection than either treatment alone.
Methods This was a randomized, blinded, placebo-controlled trial in CF-1 mice. The authors administered intraperitoneal injections of 2 mg/kg diazepam (group D), 4 mg/kg ziprasidone (group Z), the same dose of both drugs (group DZ), or saline 15 minutes before intraperitoneal administration of 105 mg/kg cocaine (an estimated lethal dose to 70%). The number of animals with seizures and apparent lethality over the following 30 minutes was recorded.
Results All treatments increased survival relative to placebo (relative risk: D = 2.6, Z = 2.3, DZ = 2.9) and decreased seizures (relative risk: D = 0.5, Z = 0.3, DZ = 0.02).
Conclusions This study suggests that diazepam and ziprasidone have efficacy for preventing lethality from cocaine poisoning in an animal model but that the combination offers little addition to either therapy alone. However, the combination may be more effective for prevention of cocaine-induced seizures. 相似文献
Objectives To assess whether the combination of these two medications would offer more protection than either treatment alone.
Methods This was a randomized, blinded, placebo-controlled trial in CF-1 mice. The authors administered intraperitoneal injections of 2 mg/kg diazepam (group D), 4 mg/kg ziprasidone (group Z), the same dose of both drugs (group DZ), or saline 15 minutes before intraperitoneal administration of 105 mg/kg cocaine (an estimated lethal dose to 70%). The number of animals with seizures and apparent lethality over the following 30 minutes was recorded.
Results All treatments increased survival relative to placebo (relative risk: D = 2.6, Z = 2.3, DZ = 2.9) and decreased seizures (relative risk: D = 0.5, Z = 0.3, DZ = 0.02).
Conclusions This study suggests that diazepam and ziprasidone have efficacy for preventing lethality from cocaine poisoning in an animal model but that the combination offers little addition to either therapy alone. However, the combination may be more effective for prevention of cocaine-induced seizures. 相似文献
10.
D. H. Schultz V. L. Shah W. Shay P. Wang 《Medical & biological engineering & computing》1977,15(2):98-105
The numerical solutions of diffusion equations have been obtained for the cases of oxygen and carbon dioxide diffusing through blood flowing between two porous parallel planes. It is assumed that at the entrance to the channel the concentration profiles are uniform and the velocity profile is fully developed. The rheological characteristics of blood are described by the Casson equation. The computations have been made employing the explicit finite-difference forward-marching procedure. The results have been obtained for a wide range of yield numbers, inlet partial pressures, pH, membrane resistances and haemoglobin concentrations. 相似文献