全文获取类型
收费全文 | 36190篇 |
免费 | 2740篇 |
国内免费 | 196篇 |
专业分类
耳鼻咽喉 | 401篇 |
儿科学 | 729篇 |
妇产科学 | 759篇 |
基础医学 | 4918篇 |
口腔科学 | 889篇 |
临床医学 | 4128篇 |
内科学 | 8133篇 |
皮肤病学 | 659篇 |
神经病学 | 3300篇 |
特种医学 | 1170篇 |
外国民族医学 | 6篇 |
外科学 | 5440篇 |
综合类 | 509篇 |
现状与发展 | 1篇 |
一般理论 | 14篇 |
预防医学 | 2212篇 |
眼科学 | 493篇 |
药学 | 2248篇 |
1篇 | |
中国医学 | 125篇 |
肿瘤学 | 2991篇 |
出版年
2023年 | 206篇 |
2022年 | 377篇 |
2021年 | 930篇 |
2020年 | 585篇 |
2019年 | 878篇 |
2018年 | 1028篇 |
2017年 | 748篇 |
2016年 | 821篇 |
2015年 | 986篇 |
2014年 | 1258篇 |
2013年 | 1623篇 |
2012年 | 2651篇 |
2011年 | 2807篇 |
2010年 | 1412篇 |
2009年 | 1290篇 |
2008年 | 2155篇 |
2007年 | 2249篇 |
2006年 | 2018篇 |
2005年 | 2071篇 |
2004年 | 1901篇 |
2003年 | 1672篇 |
2002年 | 1697篇 |
2001年 | 651篇 |
2000年 | 629篇 |
1999年 | 650篇 |
1998年 | 350篇 |
1997年 | 316篇 |
1996年 | 223篇 |
1995年 | 209篇 |
1994年 | 197篇 |
1993年 | 181篇 |
1992年 | 376篇 |
1991年 | 342篇 |
1990年 | 301篇 |
1989年 | 327篇 |
1988年 | 246篇 |
1987年 | 281篇 |
1986年 | 237篇 |
1985年 | 233篇 |
1984年 | 201篇 |
1983年 | 156篇 |
1982年 | 134篇 |
1981年 | 140篇 |
1980年 | 112篇 |
1979年 | 139篇 |
1978年 | 102篇 |
1977年 | 94篇 |
1976年 | 94篇 |
1975年 | 83篇 |
1974年 | 87篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
To investigate an association between colon cancer and obesity during early adulthood—a potentially important period in the etiology of this disease—the authors assembled, by computer linkage, a population-based historical cohort of 52,539 men born between 1913 and 1927 residing in Hawaii (USA), for whom weight and height had been recorded in 1942–43 and 1972. Linkage of this cohort to the Hawaii Tumor Registry resulted in the identification of 737 incident cases of colorectal cancer for 1972–86. An average of 3.8 cancer-free controls were matched to each case on month and year of birth and ethnicity of the parents. A case-control analysis in each anatomic subsite of the large bowel revealed that both early and middle-age body mass increased the risk of sigmoid cancer in men in a dose-dependent fashion. The odds ratios (OR) for sigmoid cancer for the highest compared with the lowest tertiles of Quetelet index were: 2.1 (95 percent confidence interval [CI]=1.4–3.2) and 1.7 (CI=1.1–2.5), at ages 15–29 and in prediagnostic years, respectively. These associations were additive and idependent of socioeconomic status. Men who were above the median Quetelet index in 1942 and 1972 had an OR of 2.7 (CI=1.8–4.0), compared with those who were below the median in both periods. This study provides further evidence for an association of obesity with colon cancer in men and suggests that this association is limited to the sigmoid colon and may be related to both early and late events of colon carcinogenesis.The authors are with the Epidemiology Program, Cancer Research Center of Hawaii, University of Hawaii. Address correspondence to Dr Le Marchand, Epidemiology Program, Cancer Research Center of Hawaii, 1236 Lauhala Street, Suite 407, Honolulu, HI 96813, USA. This work was supported in part by Public Health Service grant 5-R29-CA44503 and contract NO1-CN-55424 from the National Cancer Institute, National Institutes of Health, Department of Health and Human Services. 相似文献
83.
Vincent B. Killeen Harry Reich Fran McGlynn Lawrence A. Virgilio Michael A. Krawitz Lisa Sekel 《JSLS, Journal of the Society of Laparoendoscopic Surgeons》1997,1(3):267-268
The third reported case of pelvic gliomatosis found within foci of endometriosis is documented 16 years after the removal of a benign cystic teratoma. Grossly at laparoscopy the lesions appear as typical deep fibrotic endometriotic implants. 相似文献
84.
Daniel W. Walsh Vincent B. Ho Michael F. Haggerty 《Journal of magnetic resonance imaging : JMRI》1997,7(2):312-315
Mycotic aneurysms of the abdominal aorta are potentially fatal but uncommon. We report the MRI and MRA features of an abdominal aortic mycotic aneurysm in a patient who presented with nonspecific low back pain. By delineating the saccular nature of the aneurysm and identifying the coexistence of vertebral enhancement, MRI was crucial for the final diagnosis. A potential pitfall of contrast-enhanced MRA is also demonstrated. 相似文献
85.
BACKGROUND: There are obvious advantages to increasing donor retention. However, for reasons of blood safety, certain donors may, in fact, be more desirable to retain than others. “Safe” donors are defined as those who provided a blood donation that was negative on all laboratory screening tests and who subsequently reported no behavioral risks in response to an anonymous survey. This study identifies the most important factors affecting the intention of “safe” donors to provide another donation. STUDY DESIGN AND METHODS: An anonymous survey asking about donation history, sexual history, injecting drug use, and recent donation experience was mailed to 50,162 randomly selected allogeneic donors (including directed donors) who gave blood from April through July or from October through December 1993 at one of the five United States blood centers participating in the Retrovirus Epidemiology Donor Study. Before mailing, questionnaires were coded to designate donors with nonreactive laboratory screening tests at their most recent donation. RESULTS: A total of 34,726 donors (69%) responded, with substantially higher response among repeat donors. According to reported intentions only, the vast majority of “safe” donors indicated a high likelihood of donating again within the next 12 months. Only 3.4 percent reported a low likelihood of donating again. A comparison of those likely to return and those unlikely to return reveals significant differences in demographics and in ratings of the donation experience. A higher proportion of those unlikely to return were first-time donors, minority-group donors, and donors with less education. The highest projected loss among “safe” donors was seen for those who gave a fair to poor assessment of their treatment by blood center staff or of their physical well-being during or after donating. CONCLUSION: These data suggest that efforts to improve donors' perceptions of their donation experience, as well as attention to the physical effects of blood donation, may aid in the retention of both repeat and first-time donors. 相似文献
86.
Peptides may function as neurotransmitters liberated antidromically by sensory nerve fibres, provoking vascular responses having potential importance in some neurological disorders. Dose-response relaxation curves induced by substance P (SP) and calcitonin gene related peptide (CGRP) have been studied in porcine ophthalmic arteries in vitro. Both peptides induced vasodilation when tested separately (CGRP much greater than SP). Because of the putative interactions between such peptides in this vascular territory, a computerised system was also used for analysing over time the response to a single addition of either 10(-8) M CGRP, 10(-8) M SP or a combination of 10(-8) M SP + 10(-8) M CGRP. SP did not augment the maximum relaxation induced by CGRP alone, but increased significantly the rate of relaxation during the initial phase of the response. The effect induced by the SP+CGRP combination was stronger than the sum of the individual SP and CGRP-induced relaxations during the first 4 min of the response, which suggests a SP-CGRP synergism in this artery. 相似文献
87.
Linda R White Lars Jacob Stovner Maurice B Vincent Ole Petter Løbben Yara D Fragoso Kristian S Bjerve Ottar Sjaastad 《Cephalalgia : an international journal of headache》1992,12(2):107-110
Our group has previously reported significant changes in the incorporation of precursors into glycerophospholipids, particularly phosphatidylserine, in polymorphonuclear cells obtained from the peripheral blood of cluster headache patients, when compared with controls. The potential of these results led to further work using both the previous methodology and a modified isolation technique to obtain polymorphonuclear cells in as pure a state as possible. Neither the new results obtained using the original technique, nor the results with high purity polymorphonuclear cells from controls and cluster headache patients, confirm the marked changes in precursor uptake into glycerophospholipids originally reported. 相似文献
88.
TNF alpha and Fas mediate tissue damage and functional outcome after traumatic brain injury in mice.
Daniela Bermpohl Zerong You Eng H Lo Hyung-Hwan Kim Michael J Whalen 《Journal of cerebral blood flow and metabolism》2007,27(11):1806-1818
Tumor necrosis factor-alpha (TNFalpha) and Fas are induced after traumatic brain injury (TBI); however, their functional roles are incompletely understood. Using controlled cortical impact (CCI) and mice deficient in TNFalpha, Fas, or both (TNFalpha/Fas-/-), we hypothesized that TNFalpha and Fas receptor mediate secondary TBI in a redundant manner. Compared with wild type (WT), TNFalpha/Fas-/- mice had improved motor performance from 1 to 4 days (P<0.05), improved spatial memory acquisition at 8 to 14 days (P<0.05), and decreased brain lesion size at 2 and 6 weeks after CCI (P<0.05). Protection in TNFalpha/Fas-/- mice from histopathological and motor deficits was reversed by reconstitution with recombinant TNFalpha before CCI, and TNFalpha-/- mice administered anti-Fas ligand antibodies had improved spatial memory acquisition versus similarly treated WT mice (P<0.05). Tumor necrosis factor-alpha/Fas-/- mice had decreased the numbers of cortical cells with plasmalemma damage at 6 h (P<0.05 versus WT), and reduced matrix metalloproteinase-9 activity in injured brain at 48 and 72 h after CCI. In immature mice subjected to CCI, genetic inhibition of TNFalpha and Fas conferred beneficial effects on histopathology and spatial memory acquisition in adulthood (both P<0.05 versus WT), suggesting that the beneficial effects of TNFalpha/Fas inhibition may be permanent. The data suggest that redundant signaling pathways initiated by TNFalpha and Fas play pivotal roles in the pathogenesis of TBI, and that biochemical mechanisms downstream of TNFalpha/Fas may be novel therapeutic targets to limit neurological sequelae in children and adults with severe TBI. 相似文献
89.
Jerrold S Petrofsky Ernie Schwab Takkin Lo Maria Cuneo Daryl Lawson 《Medical science monitor》2007,13(11):CR498-CR504
BACKGROUND: Wounds, especially in the elderly, can be life threatening. One modality which allegedly increases blood flow (BF) as an aid to heal chronic wounds is electrical stimulation. This technique applies electrical current (ES) across wounds. However, while many studies show positive findings, others do not. The purpose of this investigation was to investigate some of this inconsistency in results by determining the effect of environmental temperature on the circulation of the skin which may negate the effects of electrical stimulation in a clinical setting. MATERIAL/METHODS: Ten people with no wounds, controls (C), and 12 people with wounds (W) were examined in a thermally neutral or cool room (20 degrees C) and a warm room (34 degrees C) to observe the effect of reducing sympathetic vasoconstrictor activity on the response to 5 and 15 mA sine wave biphasic ES delivered by 2x2 cm surface electrodes. RESULTS: C and W subjects showed a greater BF in the skin in a warm room. In group C, after 30 minutes of stimulation at a current of 15 milliamps, BF increased significantly (p<0.05) but by an average of only 4 flux in the cool room. In the warm environment, BF increased significantly (p<0.01) by 19.3+/-7 flux and increased further during the 60 minute recovery phase. In the W group, BF during ES increased much more during stimulation in a warm room compared to a cool room. CONCLUSIONS: The results show that local vasoconstriction due to exposure to a warm global temperature greatly increases the response of the skin the ES. 相似文献
90.
Wietlisbach Vincent 《Sozial- und Pr?ventivmedizin》1987,32(2):52-62
Résumé Parallèlement à l'enregistrement systématique des cas d'infarctus, le projet MONICA prévoit de mesurer à trois reprises le niveau des facteurs de risque cardio-vasculaires auprès d'un échantillon aléatoire. L'article présente le plan d'échantillonnage de ce premier «examen de santé» MONICA réalisé dans les cantons de Vaud, de Fribourg et du Tessin. Il s'agit d'un plan à deux niveaux, avec tirage stratifié des communes en fonction de leur taille, puis tirage des individus dans les fichiers communaux. Les conditions d'un plan d'échantillonnage efficace dans le cadre plus général de l'inférence statistique sont abordées dans une première partie théorique. Les raisons pratiques (contraintes budgétaires, problèmes de logistique, disponibilité des fichiers administratifs) qui ont motivé le choix de ce plan sont exposées ensuite. Une troisième partie décrit toutes les étapes de sa réalisation, avec les difficultés méthodologiques et concrètes rencontrées. La discussion porte sur une évaluation critique de toute la procédure qui, dans le cadre du projet MONICA, a produit des échantillons dont le degré d'adéquation avec la population est assez élevé.
Theoretical and practical aspects of sampling: the MONICA-Project.
Summary In parallel with the systematic registration of myocardial infarction, the MONICA-Project attempts to investigate at three different times the prevalence of risk factors for cardiovascular disease in the population. This article presents the sampling plan of the first MONICA survey in the cantons of Vaud, Fribourg and Tessin. The sampling procedure was at two levels: first, a sample of communes stratified according to community size was chosen, and secondly, within these communities, individuals were selected from the population registries. The prerequisites for an efficient sampling plan are discussed on a theoretical level. In addition, the practical constraints (budget, organizational problems, population registry files) are presented. Finally, all steps of the sampling procedure are described including the difficulties encountered. The discussion attempts a critical evaluation of the whole MONICA sampling procedure whose results are largely satisfactory.
Theorie und Praxis der Stichprobenbildung: das Beispiel des MONICA-Projektes
Zusammenfassung Neben einer systematischen Erfassung der Infarktfälle sieht das MONICA-Projekt eine dreimalige Erfassung der Risikofaktorenprävalenz vermittels einer Zufallsauswahl vor. Der vorliegende Artikel schildert den Stichprobenplan der ersten in den Kantonen Waadt, Freiburg und Tessin durchgeführten Untersuchung. Es handelt sich um einen zweistufigen Stichprobenplan: zuerst wurde eine Ziehung der Gemeinden — stratifiziert nach Gemeindegrösse — vorgenommen, danach wurden die Individuen auf Grund der Einwohnerregister gezogen. Die Grundbedingungen für einen effizienten Stichprobenplan werden in einem ersten theoretischen Abschnitt diskutiert. Im weiteren werden die konkreten Bedingungen der MONICA-Stichprobenziehung dargestellt (Budget-Limiten, organisatorische Probleme, Aufbau der Einwohnerregister). Ein dritter Teil beschreibt sämtliche Schritte der eigentlichen Stichprobenbildung einschliesslich der aufgetretenen Schwierigkeiten. Die Diskussion nimmt eine Gesamtbeurteilung der Stichprobenziehung im MONICA-Projekt vor, deren Ergebnis recht befriedigend ausfällt.相似文献