全文获取类型
收费全文 | 7207篇 |
免费 | 545篇 |
国内免费 | 230篇 |
专业分类
耳鼻咽喉 | 20篇 |
儿科学 | 107篇 |
妇产科学 | 72篇 |
基础医学 | 725篇 |
口腔科学 | 123篇 |
临床医学 | 933篇 |
内科学 | 517篇 |
皮肤病学 | 48篇 |
神经病学 | 426篇 |
特种医学 | 116篇 |
外国民族医学 | 3篇 |
外科学 | 377篇 |
综合类 | 1070篇 |
现状与发展 | 1篇 |
一般理论 | 9篇 |
预防医学 | 1141篇 |
眼科学 | 28篇 |
药学 | 1439篇 |
7篇 | |
中国医学 | 627篇 |
肿瘤学 | 193篇 |
出版年
2024年 | 25篇 |
2023年 | 113篇 |
2022年 | 184篇 |
2021年 | 265篇 |
2020年 | 276篇 |
2019年 | 254篇 |
2018年 | 249篇 |
2017年 | 247篇 |
2016年 | 248篇 |
2015年 | 220篇 |
2014年 | 420篇 |
2013年 | 577篇 |
2012年 | 484篇 |
2011年 | 480篇 |
2010年 | 381篇 |
2009年 | 365篇 |
2008年 | 382篇 |
2007年 | 368篇 |
2006年 | 298篇 |
2005年 | 250篇 |
2004年 | 238篇 |
2003年 | 201篇 |
2002年 | 161篇 |
2001年 | 124篇 |
2000年 | 116篇 |
1999年 | 101篇 |
1998年 | 91篇 |
1997年 | 65篇 |
1996年 | 76篇 |
1995年 | 69篇 |
1994年 | 73篇 |
1993年 | 65篇 |
1992年 | 51篇 |
1991年 | 62篇 |
1990年 | 46篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 44篇 |
1986年 | 33篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 26篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1974年 | 4篇 |
排序方式: 共有7982条查询结果,搜索用时 15 毫秒
101.
OBJECTIVES: To develop a video assessment method for General Practitioners (GPs) by analysing issues of validity, reliability and feasibility of observation of videotaped regular consultations. DESIGN: In a cross-sectional study consultations of 93 GPs were video recorded in the practice during 1 week. The GPs registered consultation and patient data in a logbook; 16 consultations per GP were selected using preset criteria. The quality of communicative and medical performance of these consultations was assessed by GP observers with a validated instrument. The validity of the procedure was evaluated by checking the content of each GP's sample using specific sample criteria. Selection bias was estimated by multiple regression analysis, with sample characteristics as independent variables and scores on communication and medical performance as dependent variables. The influence of observation on GPs and patients was assessed by a questionnaire. Generalizability theory was used to estimate reliability. Feasibility was assessed by conducting a questionnaire, by keeping accounts, and by checking the technical quality of the videotaped consultations. SETTING: Universities of Nijmegen and Maastricht, The Netherlands. SUBJECTS: General Practitioners (GPs). RESULTS: The domain of general practice was well covered in the samples; content validity was satisfactory. With regard to the sample characteristics, only the total duration of consultations appeared to correlate significantly with both the score on communication and the score on medical performance. A majority (71%) of GPs reported not being influenced by the observation, except in the first cases, and recognizing their usual daily performance in the videotaped consultations. An acceptable level of reliability was reached after 2.5 hours of observation, i.e. 12 cases by a single observer. The method was well accepted by both GPs and patients. The costs were pound250 per GP. CONCLUSIONS: Video assessment of GPs in daily practice according to the procedures described is a valid and reliable method, one which is useful for education and quality improvement. There is a trade-off between feasibility on one hand and validity, reliability and credibility on the other hand. Compared to investments in observation methods in standardized settings, the costs of video observation of GPs' actual performance are acceptable. 相似文献
102.
为探讨性伴关系属性与HIV 有关危险行为发生频率的相关性,对深圳收容教育所收容的813 名性罪错妇女进行调查。对其中性伴结构相同、性伴关系多重的两组人群进行单向有序变量的Logistic 回归分析,并将结果以数学模型形式表达出来。分析结果显示,性罪错妇女的性伴关系属性与HIV危险行为的发生频率密切相关。提示:加强性伴关系干预将可能提高目前在HIV 重点人群中开展的以健康宣传、健康教育为主的干预措施效果 相似文献
103.
Gex-Fabry M Balant-Gorgia AE Balant LP 《European journal of clinical pharmacology》1999,54(12):895-902
Objectives: The aim of the present study was to characterise onset of response to clomipramine treatment in a naturalistic setting and to investigate the relationship between concentration and delayed response, postulated to reflect drug-specific response to antidepressant therapy. Methods: Ninety-eight depressed patients were prescribed clomipramine in an open flexible manner and followed for depressive symptoms (Montgomery-Åsberg depression scale) over a maximum 12 weeks follow-up period. All patients had at least one concentration measurement for therapeutic drug monitoring purpose. Results: Firstly, survival analysis revealed a probability of 15.4% for patients not to show 50% improvement over baseline by week 12, and thus to be considered as non-responders. Median time to onset of response was 31 days for responders, indicating a relatively high probability of delayed response under routine treatment. Secondly, pattern analysis indicated a significant association between early and abrupt response on the one hand and delayed and gradual response on the other. A tendency towards an association between delayed and persistent response was also observed. Finally, receiver operating characteristics analysis allowed identification of a highly significant lower threshold of 230?ng?·?ml?1 for the sum of clomipramine and desmethyl-clomipramine, as measured at week 3, with respect to response from week 3 onward. Predictive values were 68.8% and 81.0% for concentrations above and below this threshold to predict delayed response and non-response, respectively. Thresholds were 55?ng?·?ml?1 for parent compound and 180?ng?·?ml?1 for metabolite. Conclusion: This approach supports the hypothesis that delayed response may be concentration dependent and thus may reflect true drug effect. As a consequence, monitoring clomipramine concentration about 3 weeks after initiation of therapy may valuably contribute to help clinicians decide about the adequacy of ongoing therapy. 相似文献
104.
2-(1-Aryl-1-hydroxymethyl)- and 2-aroyl-DHAQ derivatives (DHAQ, 1,4-dihydroxy-9,10-anthraquinone), and 2-(1-aryl-1-hydroxymethyl)-ATO derivatives (ATO, anthracene-1,4,9,10-tetraone) were synthesized and their antitumor activities were determined. 2-(1-Aryl-1-hydroxymethyl)-DHAQ derivatives showed a stronger cytotoxicity compared to the series of 2-(1-hydroxyalkyl)-1,4-dihydroxy-9,10-anthraquinone derivatives. It was suggested that the presence of aryl group at the side chain accelerated the bioreductive activation leading to cell death. 2-Aroyl-DHAQ derivatives, despite their higher electrophilicity, revealed smaller cytotoxicity and antitumor activity (expressed by T/C value) than 2-(1-aryl-1-hydroxymethyl)-DHAQ derivatives. Thus, no consistent relationship between the electronic effect on aromatic side chain and the cytotoxicity was observed. ATO series exhibited a higher antitumor activity (T/C, 125 to approximately 218%), though their cytotoxicity was not further improved compared to that of 2-(1-aryl-1-hydroxymethyl)-1,4-dihydroxy-9,10-anthraquinones. They manifested no correlation between the cytotoxicity and the antitumor activity. In case of 2-[1-hydroxy-1-(4-propylphenyl)-methyl]-ATO, the most bioactive one in vivo among the same series, it showed an ED50 value of 10.2 mg/mL and a T/C value of 218%. It is assumed that the anthracene-1,4,9,10-tetraones after uptake into cellular tissues might be transformed to a cytotoxic metabolite(s). 相似文献
105.
Maria A. Annunziata Ph.D. Carlo Rossi M.D. Renato Talamini Sc.D. Salvatore Tumolo M.D. Silvio Monfardini M.D. 《Supportive care in cancer》1996,4(5):334-340
The aim of this study was to determine the influence of socio-demographic and professional factors on physicians' attitudes to the terminally ill. Between May 1992 and May 1993, a survey was conducted in the province of Pordenone (north-east, Italy) in order to analyse a number of specific issues, such as emotional involvement, the need for aggressive treatments and the communication of diagnosis and prognosis. After obtaining a list of board-certified physicians from the Medical Association office in Pordenone, a modification of the cancer questionnaire of Haley and Blanchard (QSPT) was mailed to 916 doctors. Of these, 605 (60%; 487 male, 118 female; mean age 41 ± 11 SD) returned the completed questionnaire. Within the group of responders, we identified three main subgroups, according to their type of activity: general practitioners (175, 29%), hospital doctors (235, 39%) and other doctors (195, 32%). In age, sex and activity, the only significant difference between responders and non-responders was age (mean age 41 and 43 years respeetively). Most of the responders (77%) stated that they were able to deal with the terminally ill patient and his/her needs; 44%, however, admitted that patients' anxiety is sometimes unbearable. For the vast majority of the doctors polled (91%), providing a comfortable environment for an incurable patient was more important than pursuing aggressive treatment, but only 44% were convinced of the uselessness of aggressive care. To the question on whether to disclose information about imminent death to allow patients to prepare spiritually, 37% answered No, 38% Yes, and 25% were uncertain. Almost all responders (95%), however, believed in the beneficial effect of hope on the terminally ill. Ourresults suggest that doctors' professional and, most of all, sociodemographic and cultural factors determine the relationship with the patient on both the emotional and the clinical decision-making levels. 相似文献
106.
The spatial distribution of pulmonary blood flow and its change over time was investigated in term fetal rabbits, using the plasma tracer fluorescein-isothiocyanate-labeled bovine serum albumin (FITC-BSA). A tracer bolus was injected intravenously and allowed to circulate in vivo for increasing periods of time (2-30 minutes) prior to arrest of the circulation and tissue preparation. Initially, fluorescence was present in the vasculature of 43% of lung parenchymal tissue, disposed as discrete regions or "lobules." Interspersed regions of lung tissue received no tracer inflow. With increasing tracer circulation times (10, 20, and 30 minutes), a greater percentage of lung cross-sectional area contained vessels exhibiting tracer fluorescence (64, 96, and 100%, respectively). In the fetal lung, a high pulmonary vascular resistance (PVR) is maintained. Our studies indicate that, at any given moment, fetal pulmonary blood flow is distributed only to a proportion of discrete lung "lobules," while interspersed "lobules" receive no flow at all. The "lobules" alternate between these "high" and "low" vascular resistance states with a periodicity of approximately 35 minutes, comprising 22 minutes of non-perfusion followed by 13 minutes of perfusion. This circulatory pattern permits both the maintenance of high PVR and uniform lung development. Further, by directing flow to only a portion of the vasculature, greater microvascular flow rates are achieved and hence the risk of blood sludging and stasis is reduced. Recruitment of these "non-perfused" regions at birth could thus produce a significant reduction in PVR. 相似文献
107.
Rats were trained in a T-shaped maze to discriminate the effects produced by i.p. injections of tetrahydrocannabinol (THC) and the no-drug state (state-dependency, StD). Several doses of both 8-THC (range: 0.75–5.0 mg/kg) and 9-THC (range: 0.75–10.0 mg/kg) were used in order to compare the number of sessions required by the animals until reaching criterion performance. An additional group of rats had to discriminate pentobarbital sodium (20.0 mg/kg) from the no-drug state.Results: THC discrimination was proportional to dose i.e., animals that had to differentiate high doses of THC from no drug acquired the T-maize task faster than animals trained with the lower doses of THC. Acquisition data further suggest that 8-THC is somewhat less potent than the 9-isomer. 9-THC (10.0 mg/kg) produces strong StD, as defined by Overton (1971), since both this group and the barbiturate group reached the criterion within the first 10 training sessions. Time and dose testings suggest that stimulus properties of drugs vary in a quantitative way and that the calculated ED50 values are mainly determined by the training dose used. It was found that the higher the training dose used the higher was the corresponding ED50 value. Hashish smoke can maintain drug responding among THC-trained rats. A lowered content of brain catecholamines and/or serotonin, induced by AMPT (150 mg/kg) and PCPA (310–350 mg/kg), did not lessen 9-THC (2.5 mg/kg) discrimination.Portions of the results were presented at the Fourth Scandinavian Meeting on Physiology and Behavior, Oslo May 22–24, 1975. 相似文献
108.
益骨胶囊对成骨细胞增殖影响的时效及量效关系研究 总被引:8,自引:1,他引:8
目的 :运用中药血清药理学方法 ,观察益骨胶囊含药血清对新生大鼠颅骨成骨细胞 (OB)体外增殖的影响 ,并探讨用于OB药效观察的益骨胶囊含药血清制备条件。方法 :雌性 12月龄SD大鼠 80只 ,随机分为生理盐水组、益骨胶囊低剂量 (11 6g/kg)、中剂量 (34 8g/kg)、高剂量 (10 4 4g/kg)组 ,每日灌胃一次 ,连续 12天 ,分别在灌胃后的 0 5h、1h、1 5h、2h采血 ,分离血清 ,用含不同浓度益骨胶囊的血清培养SD新生大鼠颅骨OB ,MTT法检测细胞增殖情况。结果 :末次灌胃后 1 5h采血组的吸收度 (A)值明显高于各组其它时间 (P <0 0 5 ) ;不同剂量各浓度的益骨胶囊含药血清对体外培养的OB增殖均有显著的促进作用 ,其中以高剂量组的稀释比为 2 5 %的血清浓度最佳。结论 :益骨胶囊含药血清对OB增殖具有明显的促进作用 ;益骨胶囊用于OB药效观察的大鼠含药血清制备条件以人等效剂量 9倍连续 12天灌胃、末次灌胃后 1 5h采血 ,血清添加浓度以 2 5 %为宜。 相似文献
109.
110.
喜树碱及其衍生物的研究进展 总被引:4,自引:0,他引:4
喜树碱及其衍生物有较强的抗癌活性,作用靶点为拓扑异构酶I,构效关系显示喜树碱内酯的E环对其活性影响较大,并确定20位为S型是发挥抗癌作用的重点部位;调整A环和B环尤其是改变9、10、11位基团,可得到水溶性增大、抗癌活性强的衍生物。喜树碱已成为临床评价较高的抗癌药物。至2002年已设计合成15个新化合物,其中3个已上市,12个正处于临床阶段。作者对2002年以前有关喜树碱及其衍生物的合成及构效关系的研究情况进行综述。 相似文献