全文获取类型
收费全文 | 1151篇 |
免费 | 87篇 |
国内免费 | 1篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 14篇 |
妇产科学 | 45篇 |
基础医学 | 98篇 |
口腔科学 | 40篇 |
临床医学 | 312篇 |
内科学 | 228篇 |
皮肤病学 | 1篇 |
神经病学 | 74篇 |
特种医学 | 58篇 |
外科学 | 55篇 |
综合类 | 13篇 |
预防医学 | 86篇 |
眼科学 | 5篇 |
药学 | 65篇 |
1篇 | |
肿瘤学 | 140篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 11篇 |
2017年 | 21篇 |
2016年 | 21篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 49篇 |
2012年 | 38篇 |
2011年 | 39篇 |
2010年 | 32篇 |
2009年 | 29篇 |
2008年 | 42篇 |
2007年 | 52篇 |
2006年 | 54篇 |
2005年 | 45篇 |
2004年 | 59篇 |
2003年 | 41篇 |
2002年 | 45篇 |
2001年 | 44篇 |
2000年 | 37篇 |
1999年 | 52篇 |
1998年 | 22篇 |
1997年 | 21篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 16篇 |
1993年 | 16篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 23篇 |
1987年 | 17篇 |
1986年 | 30篇 |
1985年 | 22篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1979年 | 12篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1968年 | 5篇 |
排序方式: 共有1239条查询结果,搜索用时 15 毫秒
1.
2.
Two experiments examined the ingestive responses of streptozotocin-diabetic rats fed low-fat or high-fat diets to glucose, fructose, sucrose and maltose solutions in brief (30 min) intake tests. In Experiment 1, one-bottle acceptability tests were used whereas two-bottle preference tests were used in Experiment 2. Three main findings resulted from these studies. Firstly, diabetic rats fed the low-fat diet displayed a reduced acceptance of and preference for all concentrated sugar solutions. Secondly, glucose consumption patterns of diabetic rats fed the low-fat diet were distinctly different from their responses to the other sugars. Thirdly feeding high-fat diets, either high or low in carbohydrate, normalized the responses of diabetic rats to the sugar solutions. The results suggest that feeding high-fat diets to diabetic rats normalizes their responses to sugar solutions because of reductions in hunger and thirst associated with the provision of a utilizable source of calories and an improvement in body fluid balance. 相似文献
3.
Many women report an increased frequency of headaches around the time of menses. For some women, these headaches are more severe, of longer duration, and lead to greater disability than those occurring at other times in the menstrual cycle. A headache diary is critical to properly diagnose menstrual migraine (MM) by prospectively documenting headache days, severity of headache, and the headaches' relationship to menses. In women with diagnosed MM, acute treatment has been proven to be effective in randomized clinical trials. For those women who have predictable periods and may require preventive therapy, short-term prevention is a reasonable approach due to the predictability of MM. Although several agents (eg, naproxen sodium, magnesium, triptans) have been evaluated for prevention of MM, all but triptans have been assessed in small trials of between 20 and 35 women. Naratriptan, frovatriptan, and, most recently, zolmitriptan have been proven effective in preventing MM. Triptans are generally well tolerated, and the long-term safety of these agents is currently being evaluated. The flexibility of using acute and preventive therapy allows physicians to tailor treatment of MM and meet the needs of individual patients. 相似文献
4.
5.
The potential antipsychotic activity of the partial dopamine receptor agonist (+)N-0437 总被引:1,自引:0,他引:1
The (+) enantiomer of the very potent and selective dopamine D-2 agonist, 2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin (N-0437), displays partial agonistic activity at dopamine D-2 receptors. In this study (+)N-0437 was investigated for its antagonistic activity at postsynaptic DA receptors in four behavioural tests which are commonly used to evaluate potential neuroleptic activity, i.e. d-amphetamine-induced stereotypy, passive avoidance responding, intracranial self-stimulation behaviour, and catalepsy. (+)N-0437 (25-50 mumol/kg) was active in the first three models, but did not cause catalepsy. Haloperidol, which was used as a reference compound for classical DA antagonists, showed clear activity in all four models at low doses (0.5-1.0 mumol/kg). (-)N-0437, a full D-2 agonist, displayed no activity in these behavioural models. These results suggest that (+)N-0437 could be used to examine the hypothesis that the use of partial agonists could provide a new treatment for schizophrenia. 相似文献
6.
Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging 总被引:2,自引:0,他引:2
Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy. 相似文献
7.
8.
Otitis media history until age 3 years were recorded for 233 children as part of the surveillance in a Community Program for Promotion of Growth and Development (PROD) conducted in a western neighborhood of Jerusalem. Recurrent otitis media (6 or more episodes) occurred more frequently among children who were of North African or Asian origin, of lower social class and maternal education, and whose duration of breast feeding was less than 26 weeks. Children with recurrent otitis media also failed the 7-month hearing test more frequently than other children. The mean Developmental Quotient score at 2 years and the mean Stanford Binet score at 3 years were statistically significantly lower among children with recurrent otitis media, even after controlling for maternal origin and length of breast feeding. These findings underscore the importance of early identification and early intervention for otitis media. 相似文献
9.
The connectivity of a region surrounding the established thalamic auditory nuclei, n. ovoidalis (Ov) and n. semilunaris parovoidalis (SPO), was explored in the ring dove by using the anterograde tracers, Phaseolus vulgaris leucoagglutinin (PHAL) and biocytin, and the retrograde tracer, fluorogold. The Ov-SPO surround received a projection from a cell group along the interface of the auditory midbrain and the n. intercollicularis, as revealed with PHAL and biocytin, and was composed of neurons exhibiting a common morphology. These features and the presence of overlapping projections from different portions of the Ov-SPO surround suggest that this region comprises a functionally discrete area, which we term the Ov shell. Single unit recording within the shell established the existence of acoustically responsive units. Both PHAL and fluorogold labeling revealed a robust projection from the Ov shell to the caudomedial hypothalamus. Major telencephalic projections of the shell terminated within the ventral paleostriatal complex, "end-zones" of the field L, the caudomedial hyperstriatum ventrale, and regions immediately dorsal and lateral to the auditory neostriatum. Except for a portion of the shell bordering medial ovoidalis, PHAL injections into the shell also labeled fibers within the caudolateral neostriatum and along the lateral neostriatal rim. The connectivity of the Ov shell suggests that this region may integrate auditory pathways with brain regions associated with endocrine mediated behavior. In addition, the shell may constitute a source of converging input to several levels of central auditory pathways. 相似文献
10.
The effects of antioxidant supplementation during Percoll preparation on human sperm DNA integrity 总被引:20,自引:6,他引:20
Hughes CM; Lewis SE; McKelvey-Martin VJ; Thompson W 《Human reproduction (Oxford, England)》1998,13(5):1240-1247
The integrity of sperm DNA is crucial for the maintenance of genetic
health. A major source of damage is reactive oxygen species (ROS)
generation; therefore, antioxidants may afford protection to sperm DNA. The
objectives of the study were, first, to measure the effects of antioxidant
supplementation in vitro on endogenous DNA damage in spermatozoa using the
single cell gel electrophoresis (comet) assay and, second, to assess the
effect of antioxidant supplementation given prior to X-ray irradiation on
induced DNA damage. Spermatozoa from 150 patients were prepared by Percoll
centrifugation in the presence of ascorbic acid (300, 600 microM), alpha
tocopherol (30, 60 microM), urate (200, 400 microM), or acetyl cysteine (5,
10 microM). DNA damage was induced by 30 Gy X-irradiation. DNA strand
breakage was measured using the comet assay. Sperm DNA was protected from
DNA damage by ascorbic acid (600 microM), alpha tocopherol (30 and 60
microM) and urate (400 microM). These antioxidants provided protection from
subsequent DNA damage by X-ray irradiation. In contrast, acetyl cysteine or
ascorbate and alpha tocopherol together induced further DNA damage.
Supplementation in vitro with the antioxidants ascorbate, urate and alpha
tocopherol separately has beneficial effects for sperm DNA integrity.
相似文献