全文获取类型
收费全文 | 18635篇 |
免费 | 1996篇 |
国内免费 | 16篇 |
专业分类
耳鼻咽喉 | 150篇 |
儿科学 | 630篇 |
妇产科学 | 649篇 |
基础医学 | 2615篇 |
口腔科学 | 355篇 |
临床医学 | 2184篇 |
内科学 | 3775篇 |
皮肤病学 | 192篇 |
神经病学 | 1435篇 |
特种医学 | 523篇 |
外科学 | 2641篇 |
综合类 | 565篇 |
一般理论 | 43篇 |
预防医学 | 2301篇 |
眼科学 | 297篇 |
药学 | 1371篇 |
中国医学 | 15篇 |
肿瘤学 | 906篇 |
出版年
2021年 | 315篇 |
2020年 | 199篇 |
2019年 | 301篇 |
2018年 | 335篇 |
2017年 | 272篇 |
2016年 | 244篇 |
2015年 | 280篇 |
2014年 | 410篇 |
2013年 | 625篇 |
2012年 | 842篇 |
2011年 | 953篇 |
2010年 | 495篇 |
2009年 | 470篇 |
2008年 | 777篇 |
2007年 | 823篇 |
2006年 | 759篇 |
2005年 | 798篇 |
2004年 | 721篇 |
2003年 | 712篇 |
2002年 | 670篇 |
2001年 | 597篇 |
2000年 | 636篇 |
1999年 | 545篇 |
1998年 | 246篇 |
1997年 | 204篇 |
1996年 | 223篇 |
1995年 | 201篇 |
1994年 | 164篇 |
1993年 | 157篇 |
1992年 | 433篇 |
1991年 | 476篇 |
1990年 | 442篇 |
1989年 | 406篇 |
1988年 | 351篇 |
1987年 | 381篇 |
1986年 | 350篇 |
1985年 | 337篇 |
1984年 | 283篇 |
1983年 | 238篇 |
1982年 | 150篇 |
1981年 | 142篇 |
1979年 | 192篇 |
1978年 | 145篇 |
1977年 | 148篇 |
1976年 | 122篇 |
1974年 | 182篇 |
1973年 | 163篇 |
1972年 | 131篇 |
1971年 | 115篇 |
1970年 | 133篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
Detection of clustered gastrointestinal contractions in partial intestinal obstruction by surface vibration analysis.
下载免费PDF全文
![点击此处可从《Annals of surgery》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gastrointestinal contraction "clusters" with alternating quiescence occur in partial intestinal obstruction and are conventionally detected by intraluminal manometry. Surface Vibration Analysis (SVA), which is a noninvasive test, was evaluated in this study in experimental and clinical situations. In the experimental situation, former SVA was assessed against simultaneous manometry in two volunteers, in whom partial obstruction had been induced by intrajejunal balloon distension. Manometry showed typical contraction "clusters" with alternating quiescence, each of two to four minutes duration, in obstructed jejunum proximal to the balloon. The distal jejunum was inhibited. SVA showed a pattern of hyperactivity and quiescence corresponding to proximal jejunal activity. In the clinical situation, SVA recordings taken after a standard meal in nine patients with suspected chronic obstruction adhesive obstruction, (subsequently proven in seven patients and disproved in two), and 36 volunteers were compared. All patients with proved obstruction showed an SVA pattern of alternating hyperactivity and quiescence. This pattern was not observed in volunteers or nonobstructed patients. 相似文献
132.
Inhibition of allergic airways inflammation and airway hyperresponsiveness in mice by dexamethasone: role of eosinophils,IL-5, eotaxin,and IL-13 总被引:4,自引:0,他引:4
Eum SY Maghni K Hamid Q Eidelman DH Campbell H Isogai S Martin JG 《The Journal of allergy and clinical immunology》2003,111(5):1049-1061
BACKGROUND: Glucocorticoids inhibit allergen-induced airway eosinophilia and airway hyperresponsiveness (AHR). Whether glucocorticoids mediate their effects on AHR by inhibiting eotaxin and IL-5, 2 of the principal mediators of eosinophilia, or through IL-13, an important mediator of AHR, has not been established. OBJECTIVE: We sought to investigate the effects of glucocorticoids on airway eosinophilia and the expression of IL-5, eotaxin, and IL-13 in relation to the induction of AHR in a murine model of allergic asthma. METHODS: Dexamethasone (4 mg/kg) and mAbs against eotaxin (80 micro g/kg) and IL-5 (100 micro g/kg) singly and in combination were administered to immunized mice before antigen challenge. Airway responsiveness to methacholine was measured in anesthetized and mechanically ventilated animals. Eotaxin, IL-5, and IL-13 in bronchoalveolar lavage fluid (BALF), lung homogenates, or both were measured by means of ELISA. RESULTS: A single antigen challenge induced AHR that lasted at least 10 days. Eotaxin protein and mRNA levels increased in lung tissue but not in BALF after challenge. IL-5 protein and mRNA levels increased both in BALF and in lung tissue. Dexamethasone reduced airway eosinophilia, AHR, and protein and mRNA for eotaxin and IL-5. Anti-murine eotaxin and anti-IL-5 antibodies alone and in combination reduced the ovalbumin-induced airway eosinophilia significantly but failed to inhibit AHR. Both dexa-methasone and anti-IL-5/anti-eotaxin inhibited the increases in lung IL-13 levels after ovalbumin challenge to a similar extent. CONCLUSION: These findings suggest that the inhibition of AHR by the glucocorticoid dexamethasone does not appear to be explained by effects on eosinophilia, eotaxin, IL-5, or IL-13. 相似文献
133.
The present study investigated the duration of afterdepolarizations in Purkinje cell somata following climbing-fibre activation. Intracellular recordings revealed that, in cells with membrane potentials more negative than -50 mV and with normal spike-generating capabilities, climbing-fibre activation resulted in somatic responses with short afterdepolarizations. As the cell deteriorated and the resting membrane potential became more positive, the duration and form of the climbing-fibre response resembled the plateau potentials recorded from proximal dendrites. The absence of plateau potentials in undamaged Purkinje cell somata was confirmed by extracellular recording of test spike amplitudes following evoked climbing-fibre responses. 相似文献
134.
Gilbert TH Corley SM Teskey GC 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2002,146(3):336-344
This study addressed the anticonvulsant effects of phenobarbital, valproate, and ethosuximide in the amygdala of kindled guinea pigs to further validate this model for the screening of anticonvulsant drugs. Behavioral toxic effects were assessed at 30 min following drug administration using quantitative locomotor tests, as well as scores on a sedation and muscle relaxation rating index. The anticonvulsant efficacy of the drugs were evaluated from measurements of afterdischarge threshold (ADT), afterdischarge duration (ADD), and behavioral seizure severity (SS) during early and late phases of kindling acquisition, and in kindled guinea pigs. ADD and SS were also measured in response to both threshold and suprathreshold kindling stimulation. All drugs exerted slight to moderate sedative effects in guinea pigs on both the behavioral tests and rating index. We found that phenobarbital exhibited effective anticonvulsant properties in guinea pigs by consistently reducing ADD and SS in response to both threshold and suprathreshold kindling stimulation. Valproate exhibited effective anticonvulsant properties at threshold stimulation and less effective properties at suprathreshold stimulation. Lastly, we found that ethosuximide lacked effective anticonvulsant action at either threshold or suprathreshold kindling stimulation. Our results indicate that the guinea pig kindling model correctly predicted the actions of phenobarbital, valproate, and ethosuximide in the treatment of partial seizures. Guinea pig amygdala kindling appears to serve as a useful and valid model for partial epilepsy. 相似文献
135.
136.
A glass/silicon composite intracortical electrode array 总被引:5,自引:0,他引:5
Kelly E. Jones Patrick K. Campbell Richard A. Normann 《Annals of biomedical engineering》1992,20(4):423-437
A new manufacturing technique has been developed for creating silicon-based, penetrating electrode arrays intended for implantation
into cerebral cortex. The arrays consist of a 4.2 mm×4.2 mm glass/silicon composite base, from which project 100 silicon needle-type
electrodes in a 10×10 array. Each needle is approximately 1,500 μm long, 80μm in diameter at the base, and tapers to a sharp
point at the metalized tip. The technique used to manufacture these arrays differs from our previous method in that a glass
dielectric, rather than ap-n-p junction, provides electrical isolation between the individual electrodes in the array. The new electrode arrays exhibit
superior electrical properties to those described previously. We have measured interelectrode impedances of at least 1013 Ω, and interelectrode capacitances of approximately 50 fF for the new arrays. In this paper, we describe the manufacturing
techniques used to create the arrays, focusing on the dielectric isolation technique, and discuss the electrical and mechanical
characteristics of these arrays. 相似文献
137.
Background
There is currently an unprecedented expressed need and demand for estimates of maternal mortality in developing countries. This has been stimulated in part by the creation of a Millennium Development Goal that will be judged partly on the basis of reductions in maternal mortality by 2015. 相似文献138.
139.
Fiona Campbell MD MRCPath John M Geraghty MBBS MRCPath Mark A.C Appleton MBChB MRCPath E.Dillwyn Williams MD FRCP FRCPath Geraint T Williams MD FRCP FRCPath 《Human pathology》1998,29(12):1531-1535
Colorectal tumorigenesis in familial adenomatous polyposis (FAP) results from somatic mutation of either the normal APC allele or another growth control gene in epithelial cells bearing a germline APC defect. The rate at which tumors develop is therefore dependent on the somatic mutation frequency; it is not known whether this is normal or elevated in FAP. We aimed to quantify stem cell somatic mutation in FAP, comparing it with hereditary nonpolyposis colorectal cancer (HNPCC) and Crohn's disease (CD). Stem cell somatic mutation frequency was studied in 47 FAP patients, 5 HNPCC patients, and 13 CD patients, all younger than 49 years, by quantifying crypt-restricted loss of O-acetyltransferase activity in sections of morphologically normal colonic mucosa from individuals heterozygous for this monogenically inherited polymorphism. Median stem cell somatic mutation frequency was significantly higher in FAP than HNPCC (4.2 × 10−4v 1.4 × 10−4, Mann-Whitney U, P < .02). The level in CD (4.0 × 10−4) was similar to FAR Mutated crypts occurred in groups more frequently in FAP (22%) than HNPCC (12%) or CD (10%), suggesting an increase in stem cell division associated with crypt fission in FAP. We conclude that stem cell somatic mutation frequency is raised in non-neoplastic colorectal mucosa in FAR This is probably related to increased stem cell proliferation and contributes to the high rate of tumor formation in this condition. 相似文献
140.
Bhaskar Thyagarajan Jennifer L. Cruise Colin Campbell 《Somatic Cell and Molecular Genetics》1996,22(1):31-39
We have characterized homologous DNA recombination activity in nuclear protein extracts prepared from quiescent and regenerating
rat livers. Activity measured in regenerating liver extracts was elevated approximately 35-fold above control, and its appearance
closely mirrored the first wave of DNA synthesis, peaking 24 hours after a regenerative stimulus, and returning fairly rapidly
to basal levels. We also identified a strand-transferase protein of approximately 100 kDa whose presence in these extracts
correlates with homologous recombination activity. Recent evidence suggests that mammalian somatic cells possess a recombinational
DNA repair mechanism analogous to that described in the yeastSaccharomyces cerevisiae. Our results indicate that this recombinational repair process may be regulated in vivo by, or play a role in, progression
through the cell division cycle. 相似文献