全文获取类型
收费全文 | 16522篇 |
免费 | 828篇 |
国内免费 | 92篇 |
专业分类
耳鼻咽喉 | 171篇 |
儿科学 | 292篇 |
妇产科学 | 167篇 |
基础医学 | 2331篇 |
口腔科学 | 378篇 |
临床医学 | 1055篇 |
内科学 | 3845篇 |
皮肤病学 | 386篇 |
神经病学 | 1369篇 |
特种医学 | 623篇 |
外科学 | 2778篇 |
综合类 | 58篇 |
一般理论 | 1篇 |
预防医学 | 652篇 |
眼科学 | 391篇 |
药学 | 1333篇 |
中国医学 | 59篇 |
肿瘤学 | 1553篇 |
出版年
2023年 | 81篇 |
2022年 | 216篇 |
2021年 | 362篇 |
2020年 | 183篇 |
2019年 | 227篇 |
2018年 | 321篇 |
2017年 | 276篇 |
2016年 | 328篇 |
2015年 | 313篇 |
2014年 | 428篇 |
2013年 | 560篇 |
2012年 | 760篇 |
2011年 | 916篇 |
2010年 | 512篇 |
2009年 | 462篇 |
2008年 | 759篇 |
2007年 | 865篇 |
2006年 | 823篇 |
2005年 | 851篇 |
2004年 | 772篇 |
2003年 | 736篇 |
2002年 | 779篇 |
2001年 | 462篇 |
2000年 | 468篇 |
1999年 | 453篇 |
1998年 | 194篇 |
1997年 | 160篇 |
1996年 | 142篇 |
1995年 | 114篇 |
1994年 | 126篇 |
1993年 | 101篇 |
1992年 | 366篇 |
1991年 | 327篇 |
1990年 | 324篇 |
1989年 | 307篇 |
1988年 | 295篇 |
1987年 | 293篇 |
1986年 | 289篇 |
1985年 | 221篇 |
1984年 | 152篇 |
1983年 | 148篇 |
1982年 | 56篇 |
1981年 | 64篇 |
1979年 | 122篇 |
1978年 | 58篇 |
1977年 | 60篇 |
1974年 | 52篇 |
1973年 | 60篇 |
1972年 | 66篇 |
1970年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 43 毫秒
941.
We report a patient with a spindle cell lipoma on the nape and three ordinary lipomas on the abdomen and extremities. The coexistence of spindle cell lipoma and ordinary lipoma in a single patient is rare. Abundant CD34-positive spindle cells and mast cells were found in the spindle cell lipoma, but in the ordinary lipomas, only a small number of CD34-positive spindle cells were found in the interstitial connective tissue and no mast cells were seen. Because mast cells are known to stimulate mesenchymal cell proliferation and collagen production, mast cell infiltration may be a trigger for the proliferation of CD34-positive spindle cells, leading to the conversion of ordinary lipoma into spindle cell lipoma. 相似文献
942.
Tanaka T Horikawa Y Kawamoto T Kabe-Sakurai N Takeda J Mikuni M 《Brain research. Molecular brain research》2004,129(1-2):20-32
Stress refers to physiological or psychological stimuli that disrupt homeostasis and induce pathophysiological conditions due to maladaptive response, sometimes resulting in mental disorders including depression and post-traumatic stress disorder. Severe stress has been shown to induce neuronal atrophy and apoptosis, especially in the hippocampus, which is thought to be a region of the brain important in stress-related disorders. We have analyzed gene expression in rat hippocampus comprehensively to clarify the molecular mechanism of stress-related disorders. In the present study, we identified and catalogued 13,660 partial complementary DNA sequences (expressed sequence tags (ESTs)) of randomly selected clones from a cDNA library of rat hippocampus. Sequence analysis showed that these clones cluster into 7173 non-redundant sequences comprising 1794 clusters and 5379 singletons. As a result of nucleotide and peptide database search, 2594 were found to represent known rat sequences. Of the remaining 4579 genes, 599 non-redundant ESTs represent rat homologs of genes identified in other species or new members of structurally related families. In addition, we illustrate the use of these clone sets by constructing a cDNA microarray focused on genes categorized into "cell/organism defense". These ESTs and our own microarray thus provide an improved genomic source for molecular studies of animal models of stress-related disorders. 相似文献
943.
Koike K Ohno S Takahashi N Suzuki N Nozaki N Murakami K Sugiura K Yamada K Inoue M 《Clinical neuropharmacology》2004,27(4):157-162
OBJECTIVE: Although hormone replacement therapy (HRT) improves menopausal depressive symptoms, women unresponsive to HRT need an antidepressant drug as an effective adjunctive therapy. The aim of this study was to assess whether the herbal medicine Unkei-to has an impact on HRT-resistant menopausal depressive symptoms as an effective adjunctive therapy combined with HRT. METHODS: Twenty-four HRT-resistant menopausal depressive women were randomly assigned to group 1 (n = 12) or group 2 (n = 12). Subjects in group 1 were accessioned into 6 months of open treatment with Unkei-to as an adjunctive therapy and changed to Toki-shakuyaku-san for 6 months following a 1-month washout period. Group 2 started with Toki-shakuyaku-san for 6 months and then changed to Unkei-to for 6 months following a 1-month washout period. RESULTS: Three months' treatment with Unkei-to as an adjunctive therapy significantly improved Zung's Self-Rating Depression Scale (ZSDS) scores, State-Anxiety (STAI-1) scores, and Trait-Anxiety (STAI-2) scores noted before treatment, and this effect continued at 6 months. Treatment with Unkei-to was also significantly effective in reduction of ZSDS scores, STAI-1 scores, and STAI-2 scores at 3 months compared with Toki-shakuyaku-san treatment, and this effect continued at 6 months. CONCLUSIONS: Unkei-to is another option as an adjunctive herbal therapy in HRT-resistant menopausal depressive women. 相似文献
944.
Sakai JT Hall SK Mikulich-Gilbertson SK Crowley TJ 《Journal of the American Academy of Child and Adolescent Psychiatry》2004,43(9):1080-1088
OBJECTIVE: Little is known about adolescents with DSM-IV-defined inhalant abuse and dependence. The aim of this study was to compare comorbidity among (1) adolescents with inhalant use disorders, (2) adolescents who reported using inhalants without inhalant use disorder, and (3) other adolescent patients drawn from an adolescent drug and alcohol treatment program. METHOD: The authors examined 847 admissions of patients who had completed structured diagnostic assessments. The three groups were compared for noninhalant substance use disorders, posttraumatic stress disorder, conduct disorder, major depression, previous suicide attempts, and physical/sexual abuse and neglect. RESULTS: Adolescents with inhalant abuse or dependence (group 1; n = 28) were significantly more likely to meet lifetime criteria for abuse or dependence on alcohol, hallucinogens, nicotine, cocaine, and amphetamines, to have had major depression, and to have attempted suicide compared with other adolescent patients who reported never using inhalants (group 3); adolescents with inhalant use disorders also reported significantly more abuse and neglect. Adolescents with inhalant abuse or dependence (group 1) did not differ significantly on any measure compared with adolescents who reported using inhalants without an inhalant use disorder (group 2). CONCLUSIONS: Adolescent patients with a history of inhalant use, abuse, or dependence entering treatment should be carefully screened for noninhalant substance use disorders, major depression, suicidality, and abuse and neglect. 相似文献
945.
Association of the Neprilysin gene with susceptibility to late-onset Alzheimer's disease 总被引:3,自引:0,他引:3
Sakai A Ujike H Nakata K Takehisa Y Imamura T Uchida N Kanzaki A Yamamoto M Fujisawa Y Okumura K Kuroda S 《Dementia and geriatric cognitive disorders》2004,17(3):164-169
Neprilysin (NEP), also known as neutral endopeptidase, enkephalinase, CD 10, and common acute lymphoblastic leukemia antigen, is a 97-kD protein. NEP can degrade amyloid beta peptides, and its mRNA and protein levels are known to be reduced in the brains of patients with Alzheimer's disease (AD), making the NEP gene a substantial candidate for an AD risk factor. We examined the genetic association of three NEP polymorphisms, a GT-repeat polymorphism and two single nucleotide polymorphisms (SNPs, -1075A>G and -1284G>C) in its promoter region, with AD in a Japanese case-control sample (240 patients and 163 controls). The GT-repeat polymorphism, but not the SNPs, was significantly associated with late-onset AD (p = 0.0007). Our findings suggest that the GT-repeat polymorphism in the promoter region of the NEP gene or some other unknown polymorphisms, which are in a linkage disequilibrium, confer a susceptibility to late-onset AD. 相似文献
946.
Kusumi M Araki H Ijiri T Kowa H Adachi Y Takeshima T Sakai F Nakashima K 《Acta neurologica Scandinavica》2004,109(6):407-409
OBJECTIVES: The goal of this study is to clarify the association between migraine and Serotonin 2C receptor Cys23Ser polymorphism in Japanese population. MATERIALS AND METHOD: This study included 37 individuals with migraine with aura (MWA), 80 with migraine without aura, 43 with tension type headache (TH) and 360 with controls. The genotypes of Cys23Ser polymorphism were confirmed by polymerase chain reaction-restriction fragment length polymorphism techniques. RESULTS: The Ser allele frequency in control subjects is much less than that in Caucasian population. The Ser allele frequency in patients with MWA was higher than that in control subjects. CONCLUSION: The present study provides that 5HTR2c Cys23Ser polymorphism may be associated with MWA in Japanese population. 相似文献
947.
Although psychophysical studies have revealed involvement of spectral edges in auditory perception, little is known about neural processing. This study investigates how spectral edges are processed in neurons of alert cat primary-auditory-cortex (A1) with sustained response property. Stimuli are low-pass, high-pass and band-pass tones with sharp spectral edges whose edge-frequencies were systematically shifted, constructing edge-frequency response functions. Pure- and two-tone stimuli served to delineate excitatory and inhibitory subfields of the frequency response field (FRF). Based on the response function characteristics, cells were divided into edge-sensitive and edge-insensitive cells: the edge sensitive cells had narrow tuning to the high-edge (type-II cells) or low-edge (type-III cells) frequencies, while the edge insensitive cells were driven by any static stimuli with energy on FRF (type-I) or only very narrowband stimuli with energy confined to FRF (type-IV cells). Edge-sensitive cells showed a close correlation between the best frequencies of the single-frequency (BFSF) and edge-frequency (BFEF) response functions and between their half-height bandwidths, suggesting that the edge-frequency identification is processed along the tonotopic axis in A1. BFSF shifted (mean 0.11 octaves) into the stimulus band from the BFEF (closely corresponding to pitch shift into stimulus band from the edge frequency in human psychophysical data of edge-pitch), suggesting central mechanism of edge-pitch sensation. Type-I cells had non-significant inhibitory subfields of FRF; type-II cells had the significant inhibitory subfield on the higher frequency side; type-III cells, on the lower frequency side; and type-IV cells, on both sides, suggesting that the inhibitory mechanism characterizes the cell-type specific spectral-edge sensitivity. 相似文献
948.
The study of the influence of spectral envelopes of complex tones on cortical neuron discharges is important with respect to understanding the formant processing of vowels. That the sharpness of formants can contribute to the vowel quality has previously been shown in psychophysical experiments. However, it is unknown how this parameter is reflected by cortical neuron discharges, especially when a formant falls into different portions of the neuronal frequency receptive field (FRF). To show this is the aim of this study focusing on the sustained discharging neurons in the low frequency portion of cat primary auditory cortex (A1). The stimuli were multi-frequency tones whose spectral envelope was sinusoidally modulated with a peak fixed at a neuron's best frequency. The modulation depth, defined as damping-amplitude (DA), varied systematically. Stimulus bandwidth also varied systematically. Large DA at off-center frequencies produces a prominent spectral peak with steep slope, whereas small DA has a less well-defined spectral peak with gentle slope. Single frequency and two tone stimuli served to delineate the excitatory and inhibitory subfields of FRF. The A1 neuron preferred large DA when the sound energy fell into FRF with the relatively large inhibitory-subfield, while the same cell preferred small DA when it fell into FRF with the relatively small inhibitory-subfield. It is concluded that the A1 neuron can estimate steepness of slope of a spectral peak, and that a preference for steep slopes stems from a shift of balance toward the spectral inhibition, whereas a preference for gentle slopes, toward the spectral excitation. 相似文献
949.
950.
Asymptomatic radiation-induced telangiectasia in children after cranial irradiation: frequency, latency, and dose relation 总被引:1,自引:0,他引:1
PURPOSE: To determine the frequency, dose relation, and latency of radiation-induced telangiectasias in children after cranial irradiation. MATERIALS AND METHODS: The authors identified 90 children who had undergone cranial irradiation between 1981 and 2001 and undergone magnetic resonance (MR) imaging with follow-up for at least 6 months. Patients were assigned to low-dose (LD) and high-dose (HD) groups. All 24 children in the LD group received a radiation dose of 18.0 or 19.8 Gy. The 66 patients in the HD group received a dose of 32.0 Gy or greater. Telangiectasias were defined as small low-signal-intensity foci on intermediate- or T2-weighted MR images. For the patients who underwent serial MR imaging, the first depicted appearance of each telangiectatic lesion was recorded. Statistical analyses were performed. RESULTS: Telangiectasias in at least one area were observed in 18 (20%) patients. The frequency of telangiectasia was 13% (three of 24 patients) in the LD group as compared with 23% (15 of 66 patients) in the HD group; this difference was not significant (P =.22, Fisher exact test). In 12 patients (one from LD and 11 from HD group) who underwent serial MR imaging follow-up for up to 10 years (mean, 8.1 years), a total of 31 lesions were detected. Twelve (39%) of these lesions were detected by the 3rd year, and 21 (68%) were evident by the 5th year. Six (50%) of the 12 patients who underwent serial MR imaging had telangiectatic foci after 5 years. CONCLUSION: Radiation-induced telangiectasia appears to occur in at least 20% of children who undergo cranial irradiation. In this small series, higher radiation dose was not significantly associated with higher frequency of telangiectasia, although there was a trend in this direction. 相似文献