全文获取类型
收费全文 | 25864篇 |
免费 | 2619篇 |
国内免费 | 789篇 |
专业分类
耳鼻咽喉 | 192篇 |
儿科学 | 313篇 |
妇产科学 | 239篇 |
基础医学 | 1282篇 |
口腔科学 | 620篇 |
临床医学 | 4128篇 |
内科学 | 2065篇 |
皮肤病学 | 173篇 |
神经病学 | 1340篇 |
特种医学 | 648篇 |
外国民族医学 | 7篇 |
外科学 | 1530篇 |
综合类 | 3441篇 |
现状与发展 | 1篇 |
一般理论 | 5篇 |
预防医学 | 6526篇 |
眼科学 | 135篇 |
药学 | 3664篇 |
81篇 | |
中国医学 | 2172篇 |
肿瘤学 | 710篇 |
出版年
2024年 | 192篇 |
2023年 | 683篇 |
2022年 | 1091篇 |
2021年 | 1276篇 |
2020年 | 1367篇 |
2019年 | 1082篇 |
2018年 | 1039篇 |
2017年 | 1084篇 |
2016年 | 1145篇 |
2015年 | 1087篇 |
2014年 | 1973篇 |
2013年 | 2207篇 |
2012年 | 1706篇 |
2011年 | 1805篇 |
2010年 | 1374篇 |
2009年 | 1292篇 |
2008年 | 1222篇 |
2007年 | 1156篇 |
2006年 | 1018篇 |
2005年 | 802篇 |
2004年 | 709篇 |
2003年 | 609篇 |
2002年 | 460篇 |
2001年 | 398篇 |
2000年 | 334篇 |
1999年 | 311篇 |
1998年 | 264篇 |
1997年 | 208篇 |
1996年 | 184篇 |
1995年 | 162篇 |
1994年 | 149篇 |
1993年 | 117篇 |
1992年 | 113篇 |
1991年 | 95篇 |
1990年 | 76篇 |
1989年 | 66篇 |
1988年 | 61篇 |
1987年 | 47篇 |
1986年 | 54篇 |
1985年 | 57篇 |
1984年 | 46篇 |
1983年 | 20篇 |
1982年 | 21篇 |
1981年 | 21篇 |
1980年 | 31篇 |
1979年 | 9篇 |
1978年 | 18篇 |
1977年 | 12篇 |
1976年 | 4篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
N. J. Besansky 《Insect molecular biology》1993,1(4):171-178
Codon usage was compiled for fourteen chromosomal genes and four retrotransposons from the mosquito Anopheles gambiae. Variation exists among chromosomal genes in the degree of bias. The genes showing the highest bias are probably most highly expressed. In these genes, the base composition at the third codon position is much richer in G + C than is the overall coding sequence. Thus, codon usage is biased toward G- or C-ending codons. Codon usage in each retrotransposon is quite different, not only from chromosomal genes but also from the other retrotransposons. Codon usage comparisons among homologous genes from An. gambiae and two other Dipterans, the yellow fever mosquito Aedes aegypti and the fruitfly Drosophila melanogaster, show that while there are similarities, particularly between An. gambiae and D. melanogaster in the preference for G-and C-ending codons, each species has evolved a distinct pattern of codon usage. 相似文献
12.
13.
A postal survey of 100 hospitals throughout the United Kingdom and Ireland was conducted to assess current practice in the pre-operative assessment and use of pulmonary artery catheters in patients undergoing elective abdominal aortic aneurysm repair. Seventy-four completed questionnaires were received. The survey revealed that 53% of respondents hold designated pre-operative assessment clinics, attended by anaesthetists in 54% and cardiologists in 26%. However, only 4% of respondents have a written protocol for stratifying patients and assessing peri-operative risk. By far the commonest investigation of choice for further cardiological assessment is transthoracic echocardiography (67%). Other investigations of choice are multiple update gated acquisition (MUGA) scan (13%), dipyridamole thallium imaging (9%), exercise ECG (6%), stress echocardiography (1%) and stress MUGA (1%). Two units (3%) never undertook further investigation. Pulmonary artery flotation catheters are used as a routine by 9% of respondents, dependent upon left ventricular ejection fraction by 65%, dependent on other factors by 7% and not used at all by 19%. The survey reveals widespread variation in pre-operative assessment of patients undergoing elective repair of abdominal aortic aneurysm. 相似文献
14.
A. Morgado N. Raoux M. Smith J.-F. Allilaire D. Widlcher 《Acta psychiatrica Scandinavica》1989,80(6):541-547
Twenty-five depressed inpatients were asked to report their adjustment at work during the 4-month period preceding their hospitalization. Two separate reports were given: the first during the acute illness phase and the second one 10-28 days later, after symptomatic remission following standardized pharmacotherapy. Thirty-two percent more patient ratings showed absence of adjustment problems on the second report compared with the first. Significant differences between the 2 reports were found in 7 of the 9 items on the Structured and Scaled Interview to Assess Maladjustment, which is designed to assess specific aspects of maladjustment at work. The changes in the scores of maladjustment correlated with the changes in the scores of depressive symptoms, and 40% of the variation in maladjustment scores was accounted for by the pessimism item of the Montgomery-Asberg Depression Rating Scale. Much of the poor work adjustment reported by the acutely depressed patients thus seems to be caused by symptom-related subjective bias. 相似文献
15.
We assessed the feasibility and psychometric properties of two commonly used health status questionnaires in Parkinson's disease (PD): the generic Nottingham Health Profile (NHP) and the disease-specific 39-item Parkinson's disease Questionnaire (PDQ-39), from a cross-sectional postal survey of PD patients (N = 81), using traditional and Rasch measurement methodologies. Overall response rate was 88%. Both questionnaires were found feasible, although the NHP performed less well. The PDQ-39 had fewer floor effects and was better able to separate respondents into distinct groups than the NHP, whereas the latter exhibited less ambiguous dimensionality and better targeting of respondents with non-extreme scores. Reliability and validity indices were similar, and potential differential item functioning by age and gender groups was found for both questionnaires. PDQ-39 response alternatives indicated ambiguity. With few exceptions, questionnaire scales were unable to meet recommended standards fully. While preliminary, this study illustrates the need for thorough evaluation of outcome measures and has implications beyond the questionnaires used here. Although promising, both questionnaires warrant further developmental work and stronger support of measurement validity before they could be considered fully suitable for valid use in PD, in particular in earlier stages of the disease. 相似文献
16.
17.
Summary: Some of the properties of 4–bromobenzalde-hyde semicarbazone (compound IV), a prototype molecule of a new class of anticonvulsants, aryl semicarbazones, are described. Compound IV demonstrated activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazol (scPTZ) tests in mice, with low neurotoxicity. When given orally to rats, it displayed high potency in the MES test and very low neurotoxicity, resulting in a high protective index (PI). Compound IV displayed no proconvulsant properties, and development of rapid tolerance was not noted. When administered intraperitoneally (i.p.) at doses of 100, 300, or 600 mg/kg to rats, compound IV had no effect on levels of γ-aminobu-tyric acid (GABA) or on GABA-T activity in whole brain. When tested in vitro, compound IV had no effect on rat brain GABA-T at a drug concentration of 100 μM. Although the activities of certain drug-metabolizing enzymes were increased after oral administration of compound IV to rats, these effects were less prominent than those of phenytoin (PHT) and carbamazepine (CBZ). The principal mode of action of compound IV does not appear to be an interaction with the GABAA receptor complex, and other mechanisms, involving excitatory amino acid neurotransmission, will have to be considered in future investigations of the anticonvulsant activity of this compound. 相似文献
18.
Monitoring of skin response to sodium lauryl sulphate: clinical scores versus bioengineering methods
The present trial was designed to evaluate clinical scores (single observer) of sodium lauryl sulphate (SLS)-induced skin irritation in a group of subjects (n = 10) over a 10-day period along with various skin function parameters. In order to avoid significant variations due to secondary phenomena, the following parameters were recorded with non-invasive instruments in this order: skin capacitance (C1; arbitrary units; CM420 Corneometer), transepidermal water loss (TEWL; g/m2.h; Evaporimeter) and laser Doppler flowmetry (CBFV: cutaneous blood flow values; Periflux). All examinations were performed during winter on reclined relaxed subjects present for at least 10 min in a test room with controlled temperature and relative humidity (t degrees: 19.5-20.7 degrees C and RH: 47.3-60.3%). The analysis of differential data (delta = value at tx-value before test; 2-way ANOVA) was made on single parameters as a function of site (volar forearm versus neck) and time (from 24 h after 48-h occlusion with 5% SLS up to 10 days later). The profile of erythema scores over time differed between neck and forearm, but the delta CBFV readings with the laser Doppler instrument did not detect significant site-time interactions. Roughness (blind evaluation with palpating finger) and capacitance readings (delta C1) showed significant differences between sites, but the profile over time was similar in both locations. delta TEWL did not differ according to anatomical location. The reason for different erythema scores on neck and forearm might be related to inherent regional variation of optical properties of the skin or to a substantial contribution of SLS-induced roughness to the readings of erythema.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
19.
本文对肺部三种疾病1536例患者的病历资料,按病种作了统计归类。运用模糊数学原理建立了征候一疾病间的模糊关系矩阵,用参量加权模糊综合评判模型,对肺部三种疾病鉴别诊断的符合率达82.91%以上,因此认为文中建立的模型,对肺部三种疾病鉴别诊断具有参考价值。 相似文献
20.
Safety evaluation of surgical materials by cytotoxicity testing 总被引:2,自引:1,他引:1
The cytotoxicity of three kinds of commercially available absorbable hemostats [oxidized cellulose (Surgicel, gauze and cotton
types), microfibrillar collagen (Avitene), and cotton-type collagen (Integran)] and one adhesion barrier [sodium hyaluronate
and carboxymethyl-cellulose membrane (Seprafilm)] were comparatively assessed by a colony assay using V79 cells and a minimum
essential medium (MEM) elution assay in combination with a neutral red assay using L929 cells. Strong cytotoxicity was detected
for Surgicel by both the MEM elution assay and the colony assay. For Avitene, both methods revealed weak cytotoxicity. For
Seprafilm, no cytotoxicity was detected by the MEM elution assay, while a moderate degree of cytotoxicity was observed in
the colony assay. For Integran cytotoxicity was not detected by either the MEM elution or the colony assay. The results of
the different methods showed some inconsistency in terms of the degree of cytotoxicity of the materials. It is proposed that
the combination of two or more sensitive cytotoxicity testing methods for the evaluation of biomaterials is necessary to avoid
false-negative results for biomaterials at the preclinical stage. Furthermore, investigation of the correlation between the
cytotoxicity and the extraction period of the surgical materials is helpful for predicting the effect of prolonged in vivo
use of biomaterials on surrounding cells, tissues, and organs. 相似文献