全文获取类型
收费全文 | 12559篇 |
免费 | 1399篇 |
国内免费 | 48篇 |
专业分类
耳鼻咽喉 | 104篇 |
儿科学 | 515篇 |
妇产科学 | 237篇 |
基础医学 | 1669篇 |
口腔科学 | 283篇 |
临床医学 | 1566篇 |
内科学 | 2431篇 |
皮肤病学 | 159篇 |
神经病学 | 1136篇 |
特种医学 | 496篇 |
外科学 | 1558篇 |
综合类 | 758篇 |
一般理论 | 13篇 |
预防医学 | 1227篇 |
眼科学 | 376篇 |
药学 | 761篇 |
中国医学 | 5篇 |
肿瘤学 | 712篇 |
出版年
2023年 | 62篇 |
2022年 | 93篇 |
2021年 | 225篇 |
2020年 | 146篇 |
2019年 | 187篇 |
2018年 | 327篇 |
2017年 | 214篇 |
2016年 | 213篇 |
2015年 | 219篇 |
2014年 | 329篇 |
2013年 | 554篇 |
2012年 | 544篇 |
2011年 | 527篇 |
2010年 | 396篇 |
2009年 | 359篇 |
2008年 | 484篇 |
2007年 | 568篇 |
2006年 | 582篇 |
2005年 | 544篇 |
2004年 | 497篇 |
2003年 | 451篇 |
2002年 | 452篇 |
2001年 | 430篇 |
2000年 | 413篇 |
1999年 | 395篇 |
1998年 | 239篇 |
1997年 | 200篇 |
1996年 | 240篇 |
1995年 | 190篇 |
1994年 | 165篇 |
1993年 | 156篇 |
1992年 | 292篇 |
1991年 | 289篇 |
1990年 | 292篇 |
1989年 | 261篇 |
1988年 | 234篇 |
1987年 | 257篇 |
1986年 | 207篇 |
1985年 | 171篇 |
1984年 | 161篇 |
1983年 | 138篇 |
1982年 | 116篇 |
1981年 | 76篇 |
1980年 | 81篇 |
1979年 | 113篇 |
1978年 | 103篇 |
1977年 | 88篇 |
1976年 | 78篇 |
1975年 | 79篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Optic nerve pathology was studied in C57BL/6J wabbler-lethal (wl/wl) and control (+/+) mice at postnatal age of 4 weeks (P28). Qualitative light and ultrastructural pathology in wl/wl animals conformed to the criteria of primary axonal (Wallerian) degeneration. Most optic nerve axons in mutant animals appeared normal, as did oligodendroglia, the degree of myelination, the integrity and maturity of vascular elements, astroglia, and most myelin. Still, degenerating axons surrounded by somewhat normal myelin and axons with thickened myelin sheaths were prevalent in wl/wl mice. Dysmyelination or hypomyelination was not evident. At P28, pathology appeared more prominent in large diameter fibers. In the optic nerve of wl/wl mice, axonal degeneration preceded myelin disruption, adding this nerve to other previously reported systems undergoing Wallerian degeneration in this mutant. 相似文献
62.
K Bachmann T J Sullivan L S Mauro M Martin L Jauregui L Levine 《Journal of clinical pharmacology》1992,32(5):476-482
The influence of usual regimens of the H2 blocking drugs, cimetidine, ranitidine, and nizatidine on the steady-state plasma concentrations and pharmacokinetic characteristics of theophylline was studied in seventeen patients with chronic obstructive pulmonary disease (COPD). Patients were dosed to steady-state with an oral, sustained-release formulation of theophylline given in therapeutic doses twice daily for 2 weeks. Over the next 4 weeks, each patient received a week-long regimen of each H2 blocker concomitantly with theophylline, and a week-long regimen of theophylline alone (control). At the end of each of the latter 4 weeks the steady-state pharmacokinetics of theophylline were assessed. Neither ranitidine nor nizatidine treatment altered the steady-state pharmacokinetics of theophylline relative to the control phase (i.e. no H2 blocker treatment). Values for theophylline C(ave), Cssmax, AUC0-12, and CLoral were significantly different during cimetidine treatment compared with all other treatments (ranitidine, nizatidine, and control). Cimetidine increased theophylline Cssmax, AUC0-12 and Cave by approximately 32%, and decreased theophylline oral clearance by approximately 23%. The authors conclude that cimetidine alters the steady-state pharmacokinetics of theophylline in COPD patients, whereas ranitidine and nizatidine are without effect. 相似文献
63.
64.
Involvement of the distal interphalangeal (DIP) joints was noted radiographically in 24 (43.6%) of 55 patients with polyarticular juvenile rheumatoid arthritis. DIP changes were apparent later in the course of the disease and were less severe than in other affected joints. Soft tissue swelling and joint space narrowing were the most frequent abnormalities in the DIP joints. Erosive changes and angular deformities were uncommon. There was no significant correlation between DIP joint involvement and sex, age at presentation, involvement of the hands and wrists at presentation, or positivity of either rheumatoid factor or antinuclear antibody. There was a strong correlation between the presence of extraarticular signs and symptoms and involvement of the DIP joints; however, this may reflect the greater severity of the disease in these patients generally. 相似文献
65.
66.
Surface-coil MR imaging of orbital neoplasms 总被引:2,自引:0,他引:2
Fifteen patients with orbital neoplasms demonstrated by CT were studied with magnetic resonance (MR) using a 13 cm surface coil and a 0.6 T superconducting magnet. The use of a surface coil allowed for a reduction in slice thickness and a significant improvement in spatial resolution resulting in better demonstration and improved characterization of orbital lesions. All neoplasms (15/15) were demonstrated by MR. The lesions were grouped into four main categories on the basis of signal intensities on T1- and T2-weighted images. CT was superior to MR in displaying densely calcified or bony lesions (two of 15 cases). MR was at least equal or superior to CT in demonstrating the other lesions (13 of 15 cases) and had the added advantage of improved tissue characterization in some cases. With the use of surface coils, MR could become the primary imaging technique for evaluation of orbital neoplasms. 相似文献
67.
68.
Stephanie Moriceau Tania L. Roth Terri Okotoghaide Regina M. Sullivan 《International journal of developmental neuroscience》2004,22(5-6):415-422
In many altricial species, fear responses such as freezing do not emerge until sometime later in development. In infant rats, fear to natural predator odors emerges around postnatal day (PN) 10 when infant rats begin walking. The behavioral emergence of fear is correlated with two physiological events: functional emergence of the amygdala and increasing corticosterone (CORT) levels. Here, we hypothesize that increasing corticosterone levels influence amygdala activity to permit the emergence of fear expression. We assessed the relationship between fear expression (immobility similar to freezing), amygdala function (c-fos) and the level of corticosterone in pups in response to presentation of novel male odor (predator), littermate odor and no odor. CORT levels were increased in PN8 pups (no fear, normally low CORT) by exogenous CORT (3 mg/kg) and decreased in PN12 pups (express fear, CORT levels higher) through adrenalectomy and CORT replacement. Results showed that PN8 expression of fear to a predator odor and basolateral/lateral amygdala activity could be prematurely evoked with exogenous CORT, while adrenalectomy in PN12 pups prevented both fear expression and amygdala activation. These results suggest that low neonatal CORT level serves to protect pups from responding to fear inducing stimuli and attenuate amygdala activation. This suggests that alteration of the neonatal CORT system by environmental insults such as alcohol, stress and illegal drugs, may also alter the neonatal fear system and its underlying neural control. 相似文献
69.
70.
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