全文获取类型
收费全文 | 17163篇 |
免费 | 945篇 |
国内免费 | 181篇 |
专业分类
耳鼻咽喉 | 295篇 |
儿科学 | 459篇 |
妇产科学 | 367篇 |
基础医学 | 1835篇 |
口腔科学 | 617篇 |
临床医学 | 1310篇 |
内科学 | 4487篇 |
皮肤病学 | 312篇 |
神经病学 | 1748篇 |
特种医学 | 801篇 |
外科学 | 2862篇 |
综合类 | 51篇 |
一般理论 | 4篇 |
预防医学 | 563篇 |
眼科学 | 246篇 |
药学 | 886篇 |
中国医学 | 19篇 |
肿瘤学 | 1427篇 |
出版年
2024年 | 13篇 |
2023年 | 208篇 |
2022年 | 404篇 |
2021年 | 745篇 |
2020年 | 443篇 |
2019年 | 556篇 |
2018年 | 658篇 |
2017年 | 515篇 |
2016年 | 538篇 |
2015年 | 629篇 |
2014年 | 737篇 |
2013年 | 919篇 |
2012年 | 1365篇 |
2011年 | 1346篇 |
2010年 | 744篇 |
2009年 | 725篇 |
2008年 | 1101篇 |
2007年 | 1011篇 |
2006年 | 893篇 |
2005年 | 868篇 |
2004年 | 787篇 |
2003年 | 648篇 |
2002年 | 611篇 |
2001年 | 201篇 |
2000年 | 184篇 |
1999年 | 181篇 |
1998年 | 120篇 |
1997年 | 87篇 |
1996年 | 83篇 |
1995年 | 82篇 |
1994年 | 53篇 |
1993年 | 52篇 |
1992年 | 95篇 |
1991年 | 72篇 |
1990年 | 81篇 |
1989年 | 58篇 |
1988年 | 53篇 |
1987年 | 59篇 |
1986年 | 48篇 |
1985年 | 49篇 |
1984年 | 32篇 |
1983年 | 22篇 |
1982年 | 12篇 |
1980年 | 12篇 |
1979年 | 31篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1968年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Quality of life and length of survival in advanced cancer patients on home parenteral nutrition 总被引:6,自引:0,他引:6
Bozzetti F Cozzaglio L Biganzoli E Chiavenna G De Cicco M Donati D Gilli G Percolla S Pironi L 《Clinical nutrition (Edinburgh, Scotland)》2002,21(4):281-288
BACKGROUND: The use of home parenteral nutrition (HPN) in patients with advanced cancer is controversial because survival is usually short and there are no data regarding the quality of life (QoL). METHODS: Sixty-nine advanced cancer patients enrolled in a program of HPN in six different Italian centers were prospectively studied as regards nutritional status (body weight, serum albumin, serum transferrin and total lymphocyte count), length of survival and QoL through the Rotterdam Symptom Checklist questionnaire. These variables were collected at the start of HPN and then at monthly intervals. All these patients were severely malnourished, almost aphagic and beyond any possibility of cure. RESULTS: Nutritional indices maintained stable until death. Median survival was 4 months (range 1-14) and about one-third of patients survived more than 7 months. QoL parameters remained stable till 2-3 months before death. CONCLUSIONS: HPN may benefit a limited percentage of patients who may survive longer than the time allowed by a condition of starvation and depletion. Provided that these patients survive longer than 3 months, there is some evidence that QoL remains stable for some months and acceptable for the patients. 相似文献
992.
Perri P Longo L Cusano R McConville CM Rees SA Devoto M Conte M Ferrara GB Seri M Romeo G Tonini GP 《Oncogene》2002,21(54):8356-8360
The most frequent genetic alterations described in neuroblastoma (NB) are amplification of MYCN oncogene and deletion of chromosome 1p, although somatic deletions have been demonstrated at other chromosomal intervals. Since loss of heterozygosity (LOH) at distal 4p has been observed in about 20-29% of neuroblastomas, we have evaluated deletions in 41 Italian NB samples by LOH analysis at loci mapping to 4p as follows: pter-D4S2936-D4S412-D4S2957-D4S432-D4S3023-D4S431-cen. Our analysis showed allele losses in eight out of 41 samples (19.5%) and allowed the identification of a smallest region of overlapping deletion (SRO) of 3.0 cM, delimited by D4S412 and D4S3023. Two of these tumors with 4p LOH are from patients belonging to a family with recurrent NB. Interestingly the genotyping of this family revealed an identical haplotype that includes the nonrecombinant loci D4S412, D4S2957 and D4S432 shared by all affected children and demonstrated that this haplotype is retained in the two tumors carrying somatic deletions from patients of this family. Furthermore linkage analysis was performed in two NB families and yielded an overall lod-score of 3.0 in the interval including the haplotype. This provides a confirmatory indication that the region delimited by D4S2936 and D4S3023, which also includes the new defined SRO, may harbor NB predisposing gene/s. 相似文献
993.
Human melanomas of fibroblast and epithelial morphology differ widely in their ability to synthesize retinyl esters 总被引:1,自引:0,他引:1
Reduced retinyl ester synthesis has been associated with several forms of cancer; we therefore proposed studying melanoma development from the perspective of this biochemical pathway. Cultures of human melanoma cells with fibroblastoid morphology showed negligible retinyl ester synthesis; in sharp contrast, those with epithelioid morphology were capable of retinol esterification. Further, isolated proliferating epidermal melanocytes (HFSC/2) esterified retinol, whereas proliferating normal skin fibroblasts (F:CCD-1121.Sk) did not. A primary site cutaneous melanoma and its metastatic match (both of epithelioid morphology) were capable of retinol esterification, while a matched fibroblastoid tumor pair did not synthesize retinyl esters; nevertheless, LRAT (lecithin:retinol acyltransferase) protein was found in microsomal fractions from all four tumors. A mutation screen in the LRAT coding region and adjacent intronic sequences revealed several novel mutations in these melanomas as well as in HFSC/2 and F:CCD-1121.Sk cells: a single nucleotide polymorphism in exon 1(37A-->G), a silent mutation in exon 2a (188 A-->G/186 G-->A), and an insertion in the 5'UTR (9-10insC). CRBP-1 basal expression was present in the HFSC/2, and in both sets of matched tumor pairs; however, steady-state levels in the fibroblastoid melanoma pair were one-third that found in the epithelioid matched tumor pair. Co-culture of human primary site epithelioid melanoma with proliferating normal human skin fibroblasts abrogated retinol esterification within 96 h and increased the expression of the active form of TGFbeta-1 by 2.4-fold. A concomitant 3.2-fold downregulation of CRBP-1 expression took place. This is the first study to (1) demonstrate an association between retinyl ester synthesis and cutaneous melanoma morphological phenotypes; (2) suggest the existence of a soluble, diffusible inhibitor of the retinol esterification pathway; (3) report the ability of the isolated, proliferating human epidermal melanocyte to esterify retinol; and (4) provide evidence of DNA variants in the coding region of LRAT. 相似文献
994.
Reduced DAT- and DBH-immunostaining in the limbic system of Sardinian alcohol-preferring rats 总被引:3,自引:0,他引:3
We have recently shown that tyrosine-hydroxylase immunostaining (TH-IM) is selectively decreased in the cingulate cortex and in the shell of the nucleus accumbens (nAcc) of Sardinian alcohol-preferring rats (sP) when compared with Sardinian alcohol-non preferring (sNP) and Wistar (W) rats. Since these regions contain both dopamine and noradrenaline (NA) fibers, clarification of the dopaminergic and noradrenergic contribution to the decreased TH-immunoreactivity was needed. To this aim, we carried out the present immunohistochemistry study using two antibodies raised against dopamine beta-hydroxylase (DBH), the enzyme responsible for the conversion of dopamine into noradrenaline, and against the dopamine transporter (DAT), as markers for noradrenergic and dopaminergic fibers, respectively. The results show that DBH-immunostaining (DBH-IM) and DAT-immunostaining (DAT-IM) were both lower in the cingulate cortex of the sP rats with respect to sNP and W rats. In the shell of the nAcc a reduced DAT-IM in sP rats was found, while the DBH-IM did not differ between the three lines of rats. The analysis of the cell-body area of noradrenergic neurons in the locus coeruleus, revealed no differences between sP, sNP and W rats. These results indicate a selective reduction of the terminal innervation in the mesocorticolimbic dopamine and NA systems in sP rats. This genetically-determined difference may be involved in the opposite alcohol preference and consumption of sP and sNP rats. 相似文献
995.
996.
Lack of apoptosis in patients with progressive external ophthalmoplegia and mutated adenine nucleotide translocator-1 gene 总被引:3,自引:0,他引:3
Fagiolari G Sciacco M Chiveri L Lamperti C Comi GP Scarlato G Moggio M Prelle A 《Muscle & nerve》2002,26(2):265-269
Adenine nucleotide translocator-1 (ANT-1), encoded by chromosome 4 (4q34-35 locus), is a component of the mitochondrial permeability transition pores that are involved in apoptotic mechanisms. We studied muscle biopsies from seven individuals with autosomal dominant progressive external ophthalmoplegia caused by ANT-1 mutations. We found no instance of terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) positivity nor significant expression of apoptosis-related proteins. Furthermore, there was no morphological evidence of apoptosis at the ultrastructural level. Thus, degeneration of muscle in this disorder is nonapoptotic. 相似文献
997.
Long Bone Osteomyelitis 总被引:4,自引:0,他引:4
Osteomyelitis is a complex disease that is often associated with high morbidity and considerable health care costs. Bacteremia,
contiguous focuses of infection, penetrating trauma, or surgery are the major predisposing factors for this infection. Bone
necrosis and bone destruction occur early in the course of osteomyelitis, leading to a chronic process and eliminating the
host’s ability to eradicate the pathogens. The presence of poorly vascularized tissues, the adherence to bone structures and
implants, and a slow bacterial replication rate are recognized as important factors for the persistence of the infection.
Treatment of osteomyelitis is particularly challenging and involves adequate antimicrobial therapy and surgical debridement
of all necrotic bone and soft tissues. Antibiotic treatment is usually started on an empiric basis and then modified according
to the results of cultures and sensitivity tests. Surgical treatment consists of debridement, obliteration of dead space,
adequate soft tissue coverage, restoration of blood supply, and stabilization. 相似文献
998.
999.
The prognostic significance of "switching" in patients with bipolar disorder: a 10-year prospective follow-up study 总被引:1,自引:0,他引:1
OBJECTIVE: This study explored whether "switching" (i.e., the direct transition from one mood polarity to the other) has significant prognostic implications in patients with bipolar disorder. METHOD: Bipolar disorder patients (N=97) whose first prospectively observed episode included at least one mood polarity switch and 97 bipolar disorder patients whose index episode was monophasic were compared with respect to several demographic and historical variables, symptomatic features of the index episode, time to recovery from the index episode, time spent in an affective episode during a prospective observation period, and psychopathological and psychosocial outcome at a 10-year follow-up interview. RESULTS: Patients whose index episode included at least two mood polarity switches spent significantly more time in an affective episode during the observation period and had a significantly worse psychopathological and psychosocial outcome 10 years after recruitment than those whose index episode included only one mood polarity switch or was monophasic. Patients whose polyphasic index episode started with depression spent a significantly higher proportion of time in an affective episode and had a significantly worse 10-year outcome than those whose polyphasic index episode started with mania or hypomania. Retention of the switching pattern throughout the observation period was seen in 42.4% of patients whose index episode started with mania and in 65.2% of those whose index episode started with depression. CONCLUSIONS: An index episode including at least two mood polarity switches, especially if starting with depression, is associated with a poor long-term outcome in patients with bipolar disorder. This pattern represents a significant target for new pharmacological and psychosocial treatment strategies. 相似文献
1000.
Neurons containing gamma aminobutyric acid (GABA) are widely distributed throughout the primary auditory cortex (AI). We investigated the effects of endogenous GABA by comparing response properties of 110 neurons in chinchilla AI before and after iontophoresis of bicuculline, a GABA(A) receptor antagonist, and/or CGP35348, a GABA(B) receptor antagonist. GABA(A) receptor blockade significantly increased spontaneous and driven discharge rates, dramatically decreased the thresholds of many neurons, and constricted the range of thresholds across the neural population. Some neurons with 'non-onset' temporal discharge patterns developed an onset pattern that was followed by a long pause. Interestingly, the excitatory response area typically expanded on both sides of the characteristic frequency; this expansion exceeded one octave in a third of the sample. Although GABA(B) receptor blockade had little effect alone, the combination of CGP35348 and bicuculline produced greater increases in driven rate and expansion of the frequency response area than GABA(A) receptor blockade alone, suggesting a modulatory role of local GABA(B) receptors. The results suggest that local GABA inhibition contributes significantly to intensity and frequency coding by controlling the range of intensities over which cortical neurons operate and the range of frequencies to which they respond. The inhibitory circuits that generate nonmonotonic rate-level functions are separate from those that influence other response properties of AI neurons. 相似文献