全文获取类型
收费全文 | 2299篇 |
免费 | 87篇 |
国内免费 | 41篇 |
专业分类
耳鼻咽喉 | 41篇 |
儿科学 | 55篇 |
妇产科学 | 49篇 |
基础医学 | 309篇 |
口腔科学 | 73篇 |
临床医学 | 174篇 |
内科学 | 218篇 |
皮肤病学 | 12篇 |
神经病学 | 363篇 |
特种医学 | 76篇 |
外科学 | 287篇 |
综合类 | 208篇 |
预防医学 | 108篇 |
眼科学 | 33篇 |
药学 | 326篇 |
1篇 | |
中国医学 | 12篇 |
肿瘤学 | 82篇 |
出版年
2023年 | 27篇 |
2022年 | 45篇 |
2021年 | 66篇 |
2020年 | 45篇 |
2019年 | 55篇 |
2018年 | 47篇 |
2017年 | 59篇 |
2016年 | 55篇 |
2015年 | 75篇 |
2014年 | 149篇 |
2013年 | 140篇 |
2012年 | 112篇 |
2011年 | 133篇 |
2010年 | 92篇 |
2009年 | 129篇 |
2008年 | 123篇 |
2007年 | 122篇 |
2006年 | 100篇 |
2005年 | 79篇 |
2004年 | 79篇 |
2003年 | 54篇 |
2002年 | 48篇 |
2001年 | 48篇 |
2000年 | 45篇 |
1999年 | 49篇 |
1998年 | 39篇 |
1997年 | 31篇 |
1996年 | 37篇 |
1995年 | 40篇 |
1994年 | 32篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 12篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有2427条查询结果,搜索用时 15 毫秒
1.
The Institute of Medicine distinguishes between programs based on who is targeted: the entire population (universal), those
at risk (selective), or persons exhibiting the early stages of use or related problem behavior (indicated). Evaluations suggest
that although universal programs can be effective in reducing and preventing substance use, selective and indicated programs
are both more effective and have greater cost-benefit ratios. This paper tests these assumptions by comparing the impact of
these program types in reducing and preventing substance use at the individual level (i.e., those exposed to intervention
services) and in the population (i.e., those exposed and not exposed to intervention services). A meta-analysis was performed
on 43 studies of 25 programs to examine program comparability across IOM categories. When examining unadjusted effect sizes
at the individual level, universal programs were modestly more successful in reducing tobacco use, but selective and indicated
programs were modestly more successful in reducing alcohol and marijuana use. When adjusted to the population level, the average
effect sizes for selective and indicated programs were reduced by approximately half. At the population level, universal programs
were more successful in reducing tobacco and marijuana use and selective and indicated programs were more successful in reducing
alcohol use. Editors’ Strategic Implications: The authors’ focus on the public health value of a prevention strategy is compelling and provides a model for analyses of
other strategies and content areas. 相似文献
2.
Cylindrical matrices were prepared by compression either of polyvinyl alcohol 100000 or mixtures of the excipient and a drug (sodium salicylate or theophylline). To modify the cylindrical shape, a hole was bored in the centre of the flat surface through both sides of the matrices. Different swellable systems were obtained applying an impermeable coating to one, two or three surfaces of the perforated matrices. The swelling of the perforated matrices was modified according to the number and the position of the coated surfaces (selective coating) and the loaded drug. Pseudo-zero order kinetics were obtained when the interior hole was the only uncoated surface. 相似文献
3.
4.
Intravenous cholangiography,ERCP, and selective operative cholangiography in the performance of laparoscopic cholecystectomy 总被引:1,自引:0,他引:1
Between March 1990 and March 1993 some 822 consecutive patients underwent an attempt at laparoscopic cholecystectomy. Intravenous cholangiography (IVC), ERCP, and selective intraoperative cholangiography (IOC) were used in the evaluation of common bile duct (CBD) stones. Two hundred thirteen patients (26%) were identified preoperatively with either abnormal liver functions or a dilated common bile duct suggestive of CBD stones. IVC was performed in 143 patients (67%). Choledocholithiasis was identified in 14 patients (10%). Preoperative therapeutic ERCP was successful in all 14 patients (100%). Diagnostic ERCP was attempted in 61 patients and successful in 59 (97%). Choledocholithiasis was identified in 25 patients (41%). Successful extraction was accomplished in 23 patients (92%). Transcystic common bile duct exploration was used effectively in the patients with an unsuccessful ERCP. IOC was attempted in 50 patients and successful in 48 (96%). Choledocholithiasis was identified in three (6%). A retained CBD stone was present in eight patients (1%). There was one level I CBD injury (0.122%). The use of IVC, selective ERCP, and selective IOC is a reasonable approach in the performance of laparoscopic cholecystectomy. 相似文献
5.
Intra-operative quick insulin assay to confirm complete resection of insulinomas guided by selective arterial calcium injection (SACI) 总被引:1,自引:0,他引:1
Oliver Gimm Evelyn König Phuong Nguyen Thanh Michael Brauckhoff Wolfram Karges Henning Dralle 《Langenbeck's archives of surgery / Deutsche Gesellschaft fur Chirurgie》2007,392(6):679-684
Background and aims Insulinomas are rare endocrine disorders. Pre-operatively, conventional imaging techniques often fail to localise the tumor.
In addition, due to the lack of quick insulin assays, intra-operative confirmation of complete resection was impossible until
recently.
Materials and methods Six patients with biochemical evidence of an insulinoma underwent pre-operative localisation studies and selective arterial
calcium injection (SACI). In addition, insulin was measured before surgery and every 10–15 min after resection of the tumor
using a quick insulin assay.
Results Pre-operative localisation studies identified the tumor correctly as follows: endosonography: three of four, magnetic resonance
imaging: two of four and SACI: six of six. Tumors in the head and body were enucleated while those in the tail were resected
(n = 2, each). Those three patients, in whom magnetic resonance imaging and/or endosonography could localise the tumors pre-operatively,
underwent laparoscopic surgery while the remaining three patients underwent open surgery. Intra-operatively, insulin dropped
to normal levels within 20 min in all cases. After a follow-up of 0.8–3 years, all patients remained biochemically cured.
Conclusions Pre-operatively, SACI appears to be a very sensitive localisation technique and may be most helpful in guiding the surgeon
if conventional imaging techniques fail to localise the tumor. Complete removal of an insulinoma can be reliably predicted
using a quick insulin assay.
This paper was presented at the 2nd Biennial Meeting of the European Society of Endocrine Surgeons (ESES), May 18–20, 2006,
Krakow, Poland. 相似文献
6.
肛门括约肌肌电图监测下双侧L2~S2选择性脊神经后根切断术治疗痉挛性脑瘫 总被引:2,自引:1,他引:1
目的为提高手术安全性,在L2~S2选择性脊神经后根切断(SPR)手术时,对肛门括约肌进行肌电图(EMG)监测,并评价其作用。方法在SPR手术监测中,当对S2后根小束进行电刺激时,采用针状电极记录双侧肛门括约肌的反应情况,有明显反应的后根小束予以保留。手术后随访患者踝痉挛改善情况和括约肌功能变化情况。结果所有患者手术后踝痉挛均有明显改善,无大小便功能障碍发生。结论SPR手术包括S2后根时,术中括约肌EMG监测对保证疗效,保护括约肌功能,提高手术安全,具有重要意义。 相似文献
7.
Effects of antipsychotic drugs on latent inhibition: sensitivity and specificity of an animal behavioral model of clinical drug action 总被引:1,自引:1,他引:0
Latent inhibition (LI) of a conditioned emotional response (CER) has been proposed as a quantitative measure of selective attention. We have assessed the parallels of the pharmacology of LI in rats with the clinical pharmacology of schizophrenia. Drug and vehicle treated rats were divided into groups and preexposed 20 times to cage illumination as a CS, or not preexposed. All groups were conditioned with 2 CS-footshock pairings. The following day CER, as measured by interruption of drinking in response to CS presentation, was recorded. LI was observed as a decreased CER in preexposed relative to non-preexposed animals. LI was enhanced by haloperidol 0.3 mg/kg after 7 or 14 daily treatments, but not after a single acute dose. Haloperidol doses of 0.3 and 0.03 mg/kg enhanced LI, while doses of 0.003 and 3.0 mg/kg had no effect. Haloperidol enhancement of LI was unaffected by the coadministration of the anticholinergic agent trihexyphenidyl. Enhancement of LI is exhibited by the antipsychotic drugs fluphenazine, chlorpromazine, thiothixene, thioridazine, mesoridazine, and metoclopramide but not clozapine. The non-antipsychotic drugs pentobarbital, imipramine, chlordiazepoxide, trihexyphenidyl, and promethazine failed to enhance LI. LI exhibits striking parallels to the clinical pharmacology of schizophrenia.Preliminary data were presented in part at the Society for Neuroscience Annual Meeting, Phoenix, AZ, 1989 相似文献
8.
Visual spatial attention to stimuli presented on the vertical and horizontal meridian: An ERP study 总被引:6,自引:0,他引:6
THOMAS C. GUNTER ALBERTUS A. WIJERS JANET L. JACKSON GIJSBERTUS MULDER 《Psychophysiology》1994,31(2):140-153
In the first experiment, 48 subjects carried out a visual spatial attention task. Stimuli were presented at the vertical meridian, either above or below a fixation dot, and the subjects were instructed to attend to one of these stimulus positions and ignore the other position. In three different conditions, the distances between stimulus positions and fixation were 0.5°, 0.9°, and 1.3°. Subjects searched for the presence of prememorized target letters at the attended location: memory load was one or four items in different conditions. The P1/N1 enhancement typically found on the horizontal dimension was not observed on the vertical dimension. Instead, a positive shift of the attended compared with the unattended stimuli was found, which was most prominent at anterior electrodes. This positivity showed effects of the distance manipulation. The N2b-P3a effect of attention and the effect of memory load (search negativity) normally present in this kind of selective search task were also found. Reaction times were faster when attention was directed above fixation than when it was directed below fixation. The event-related potential data suggested that this difference could be attributed to a more efficient neglecting of irrelevant stimuli presented below fixation. In Experiment 2, we examined whether the absence of the P1/N1 enhancement as the result of spatial attention in Experiment 1 could be attributed to (a) the presentation of stimuli along the vertical meridian instead of along the horizontal meridian, (b) the use of midline electrodes instead of lateralized electrodes, and (c) the relatively small spatial separation between the relevant and irrelevant stimuli. Twelve subjects searched for the presence of a single target letter at an attended position in three different conditions. In two of the conditions the letters were presented to the left or right of fixation. The distance between fixation and the stimulus positions was 1.3° in one of these conditions and 3° in the other condition. In the third condition, the stimuli were presented at 3° above or below fixation. In all three conditions effects similar to those in Experiment 1 were observed. In addition, in all three conditions an enhancement of the P1 and N1 components was found at two lateral occipitotemporal electrodes. 相似文献
9.
Increased nasal air flow during exercise was examined as a possible heat loss avenue contributing to selective brain cooling in hyperthermic humans. On 2 separate days, eight subjects [mean (SE) age, 26.4 (1.2) years] exercised on a cycle ergometer in a warm room [28 (0.2)°C; 28 (5)% relative humidity] to induce a moderate level of hyperthermia. In one session the nostrils were physically dilatated [average dilatation 1.55 (0.17) times] and in the other they were not (control). Both sessions started with a 5-min resting period; then subjects pedaled at 60 W for 5 min, 100 W for 15 min, and 150 W for 20 min. During dilatation both tympanic temperature (T
ty) and forehead skin blood flow, estimated by laser doppler velocimetry, were significantly lower than during the control exercise of 150 W. Rates of increase of (T
ty) during the 100-W exercise were the same in both conditions; however, during the 150-W exercise with dilatated nostrils (T
ty) increased at a rate significantly lower than during control [1.1 (0.3)°C·h–1 vs 1.5 (0.4)°C·h–1]. The change in the rate of increase of T
ty between conditions was significantly correlated to the degree of nostril dilatation (r = –0.77, P = 0.02), suggesting that the lower (T
ty) observed was due to nostril dilatation. Facial skin temperature was not significantly different between sessions. The results suggest that the nasal cavity may act as a heat exchanger in selective brain cooling of exercising humans. 相似文献
10.
The prediction from Sokolov's (1960) theory that, following OR habituation, size of OR return is proportional to the amount of difference between the new stimulus and the habituating stimulus was tested using an auditory stimulus varying in frequency and intensity. Five Ss were allocated to each of 16 conditions, three conditions involving changes in frequency, three involving changes in intensity, nine involving changes in both frequency and intensity, with one control condition involving a repetition of the habituating stimulus. Following habituation of the GSR component of the OR to a criterion of response failure for three successive trials, magnitude of GSR under the 16 conditions was measured. Contrary to Sokolov's theory, only increase in intensity had a significantly different effect on OR return. More importantly, it was found that Ss habituating rapidly to the initial stimulus were less likely to show OR return to stimulus change. It was concluded that individual differences in habituation rate may be more important than stimulus difference effects in selective habituation. 相似文献