全文获取类型
收费全文 | 1275062篇 |
免费 | 94204篇 |
国内免费 | 1984篇 |
专业分类
耳鼻咽喉 | 18185篇 |
儿科学 | 42260篇 |
妇产科学 | 37812篇 |
基础医学 | 186985篇 |
口腔科学 | 35380篇 |
临床医学 | 108103篇 |
内科学 | 251430篇 |
皮肤病学 | 26497篇 |
神经病学 | 99174篇 |
特种医学 | 49981篇 |
外国民族医学 | 366篇 |
外科学 | 197583篇 |
综合类 | 26513篇 |
现状与发展 | 1篇 |
一般理论 | 300篇 |
预防医学 | 92584篇 |
眼科学 | 29056篇 |
药学 | 97755篇 |
1篇 | |
中国医学 | 2496篇 |
肿瘤学 | 68788篇 |
出版年
2018年 | 11809篇 |
2015年 | 11614篇 |
2014年 | 15994篇 |
2013年 | 24344篇 |
2012年 | 33541篇 |
2011年 | 35936篇 |
2010年 | 21207篇 |
2009年 | 20017篇 |
2008年 | 34974篇 |
2007年 | 37940篇 |
2006年 | 38498篇 |
2005年 | 37791篇 |
2004年 | 36376篇 |
2003年 | 35366篇 |
2002年 | 34915篇 |
2001年 | 58093篇 |
2000年 | 59583篇 |
1999年 | 50687篇 |
1998年 | 14232篇 |
1997年 | 12809篇 |
1996年 | 13071篇 |
1995年 | 12345篇 |
1994年 | 11757篇 |
1993年 | 10860篇 |
1992年 | 40986篇 |
1991年 | 40360篇 |
1990年 | 39886篇 |
1989年 | 38707篇 |
1988年 | 36109篇 |
1987年 | 35349篇 |
1986年 | 33723篇 |
1985年 | 32134篇 |
1984年 | 23922篇 |
1983年 | 20818篇 |
1982年 | 12377篇 |
1981年 | 10928篇 |
1980年 | 10204篇 |
1979年 | 22635篇 |
1978年 | 15877篇 |
1977年 | 13729篇 |
1976年 | 12970篇 |
1975年 | 14201篇 |
1974年 | 16682篇 |
1973年 | 16076篇 |
1972年 | 15318篇 |
1971年 | 14229篇 |
1970年 | 13214篇 |
1969年 | 12731篇 |
1968年 | 11978篇 |
1967年 | 10478篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Usher syndrome: clinical findings and gene localization studies 总被引:3,自引:0,他引:3
William J. Kimberling Sandra L. H. Davenport Ira Priluck Valorie White Karen Biscone-Halterman Patrick E. Brookhouser Claes G. Mller Gunnar Lund Timothy J. Grissom Michael D. Weston 《The Laryngoscope》1989,99(1):66-72
The issue of genetic heterogeneity is a critical problem in the localization of the gene(s) for Usher syndrome. Based on the data obtained on families studied to date, the differences between type I and type II Usher syndrome appear quite distinct with regard to auditory and vestibular function. Although the majority of families can be confidently diagnosed as typical type I or type II, clinical investigations revealed four families with findings that did not fit into either of the two more common subtypes. These findings emphasize the critical importance of an in-depth clinical analysis concomitant with the linkage investigation to assure accurate subtyping of Usher syndrome. Based on an analysis of only those families with definite type I or type II Usher syndrome, approximately 17% of the genome can be excluded as a potential site of the gene for type I, and 14% can be excluded as the site for the type II gene. This study will continue until the Usher gene(s) is successfully localized. 相似文献
972.
973.
Five 3'-fluorinated ribonucleosides were prepared and evaluated for their inhibitory properties against different viruses. The synthesis of these compounds was achieved by treatment of 2',5'-di-O-tritylated nucleoside analogues possessing a xylo-configuration with diethylaminosulfur trifluoride, followed by deprotection. 3'-Fluoro-3'-deoxyadenosine was active against a broad range of viruses, encompassing both DNA viruses [pox (vaccinia)], single-stranded (+) RNA viruses [picorna (polio, Coxsackie B), toga (sindbis, Semliki Forest)] and double-stranded RNA viruses (reo). In its antiviral activity spectrum 3'-fluoro-3'-deoxyadenosine clearly differed from those adenosine analogues that are known as inhibitors of S-adenosylhomocysteine hydrolase. 3'-Fluoro-3'-deoxyadenosine also proved effective in vivo, in inhibiting tail lesion formation in mice inoculated intravenously with vaccinia virus. 相似文献
974.
Gram negative endotoxins play a contributory role in the syndrome which results from over consumption of carbohydrates by horses and ponies. Since the antibiotic polymyxin B exerts a direct anti-endotoxin effect by chemically modifying the active lipid A moiety of endotoxin, it might be expected to protect horses after carbohydrate overload and provide a new therapeutic and experimental tool for this condition. The present study was undertaken to evaluate the effect of polymyxin B on hemostatic, hemodynamic, acid-base, and clinical aspects of the syndrome resulting from carbohydrate overload. Experimentally-induced carbohydrate overload resulted in lactic acidosis, hypercoagulability, hypovolemic shock and lameness. Although there was a slight delay in the onset of clinical signs resulting from experimental carbohydrate overload in treated animals, polymyxin B administered iv at 2.5 mg/kg every 6 hr failed to significantly ameliorate the coagulopathy, acidosis, lameness and shock induced by alimentary carbohydrate overload. 相似文献
975.
G J Blauw P van Brummelen P C Chang P Vermeij P A van Zwieten 《Journal of cardiovascular pharmacology》1989,14(1):14-21
The influence of age on the regional arterial and venous effects of serotonin (5-HT) was investigated in 13 young (aged 22-31 years) and seven older (aged 50-69 years) healthy volunteers. Single-dose infusions of 5-HT (1, 10, and 80 ng/kg/min) and of the 5-HT2 receptor antagonist ritanserin (50, 150, and 500 ng/kg/min) were administered into the brachial artery. Subsequently, the relative arterial and venous effects of the highest dose of 5-HT were investigated. Forearm blood flow (FBF) and maximum venous outflow (MVO) were measured by venous occlusion plethysmography. Heart rate (HR) and intraarterial (i.a.) blood pressure were recorded semicontinuously. In both age groups, 5-HT induced an initial transient arterial dilation, followed by a persistent increase in FBF for the doses of 1 and 10 ng/kg/min and a relative small decrease in FBF for the highest dose. In both age groups, the highest dose of 5-HT induced a similar large reduction in MVO (p less than 0.05 for both). The reduction in MVO was attenuated by ritanserin (500 ng/kg/min, p less than 0.05 for both groups). In the younger subjects, this dose of ritanserin also unmasked an arterial dilator effect of the highest dose of 5-HT (p less than 0.05). The single infusions of ritanserin did not influence FBF significantly in either study group. No significant differences were observed between the age groups. These results show that in the forearm of healthy subjects arterial and venous vascular responses to 5-HT were not age-related. In the arterial vascular bed, 5-HT acted predominantly as a vasodilator; at high doses, mainly venous vasoconstriction was observed.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
976.
A M Cesura M D Galva R Imhof E Kyburz G B Picotti M Da Prada 《European journal of pharmacology》1989,162(3):457-465
This study demonstrated the existence of specific binding sites for [3H]Ro 19-6327 in human platelet membranes. This compound is a novel, time-dependent inhibitor of monoamine oxidase type B (MAO-B) and is structurally closely related to [3H]Ro 16-6491. The density of the sites labelled with high affinity by [3H]Ro 19-6327 was similar to that observed in previous studies with [3H]Ro 16-6491 as ligand. Binding was reversible at 20 degrees C and showed a relatively slow dissociation (t1/2 = 220 min). The dissociation rate was markedly decreased (t1/2 = greater than 24h) at 0 degrees C. MAO-B, but not MAO-A inhibitors, effectively prevented the binding of [3H]Ro 19-6327. Like [3H]Ro 16-6491, [3H]Ro 19-6327 is recognized as a substrate by MAO-B, being eventually deaminated by the enzyme. Since the deaminated aldehyde derivative of Ro 19-6327 did not inhibit MAO-B, a still unidentified reversible adduct, formed at the MAO-B active site, might explain the high potency and selectivity of [3H]Ro 19-6327. Incubation of the radioligand-enzyme complex from platelet and brain membranes with NaBH3CN and acetic acid (to pH 4.5) caused the irreversible incorporation of the radioactivity into a single polypeptide as shown by SDS-PAGE analysis. This polypeptide had a molecular weight identical to that of the MAO-B subunit, i.e. 58,000. The presence of unlabelled MAO-B inhibitors in the incubation mixture prevented the covalent incorporation of [3H]Ro 19-6327. The irreversible MAO-B inhibitor, [3H] pargyline, labelled a protein with a molecular weight identical to the protein labelled by [3H]Ro 19-6327.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
977.
Toward a model for improved targeting of aged at risk of institutionalization. 总被引:3,自引:1,他引:2
下载免费PDF全文
![点击此处可从《Health services research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A national sample of institutionalized and noninstitutionalized aged was created by merging the 1977 National Nursing Home Survey and its counterpart, the National Health Interview Survey for the same year. A weighted logistic regression analysis was conducted to identify factors that might be useful in calculating home- and community-based long-term care clients' risk of institutionalization. A model containing patient characteristics, nursing home bed supply, and a climate variable correctly classified 98.2 percent of cases residing in nursing homes or the community. Physical dependency, mental disorder and degenerative disease, lack of spouse, being white, poverty, old age, unoccupied nursing home beds, and climate all appear to be determinants of institutional residency among the aged. 相似文献
978.
Basic protein enhances the incorporation of DNA into lipid vesicles: model for the formation of primordial cells. 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
D G Jay W Gilbert 《Proceedings of the National Academy of Sciences of the United States of America》1987,84(7):1978-1980
DNA can be encapsulated into lipid vesicles formed by sonication. The presence of a basic protein, lysozyme, enhances the incorporation 100-fold above the level expected by random trapping. This is demonstrated by the ability of the lipid vesicles to protect DNA from digestion with DNase. Such an enhancement of nuclei acid incorporation into vesicles by basic polypeptides and the sharply increased concentration of these macromolecules in the internal volume may have been advantageous in prebiotic evolution. 相似文献
979.
Immunologic contact urticaria to fish 总被引:1,自引:0,他引:1
980.
G.E. ORLANDINI S. ZECCHI ORLANDINI A.F. HOLSTEIN R. EVANGELISTI and R. PONCHIETTI 《Andrologia》1987,19(3):315-321
The human prostatic urethra has been investigated by means of scanning electron microscopy. On the posterior wall of the urethra, the seminal colliculus with the orifices of the ejaculatory ducts is clearly detectable. The upper portion of the prostatic urethra shows a typical transitional epithelium with large superficial cells of a ruffled appearance. In the lower portion of the organ (underneath the openings of the ejaculatory ducts), the apical pattern of the cells varies considerably. Four main aspects are recognizable: apices provided with microvilli, dome-shaped apices with an almost smooth surface, large apices with labyrinthic microplicae and ciliated apices. Also, apices showing intermediate characteristics can be noted. The functional significance of the morphological patterns as well as the possibility of a transition among the various types of surface structures are discussed. 相似文献