全文获取类型
收费全文 | 30615篇 |
免费 | 1839篇 |
国内免费 | 105篇 |
专业分类
耳鼻咽喉 | 278篇 |
儿科学 | 747篇 |
妇产科学 | 660篇 |
基础医学 | 3841篇 |
口腔科学 | 923篇 |
临床医学 | 3196篇 |
内科学 | 6098篇 |
皮肤病学 | 401篇 |
神经病学 | 2935篇 |
特种医学 | 1211篇 |
外科学 | 3436篇 |
综合类 | 317篇 |
一般理论 | 31篇 |
预防医学 | 3027篇 |
眼科学 | 748篇 |
药学 | 2522篇 |
中国医学 | 43篇 |
肿瘤学 | 2145篇 |
出版年
2023年 | 101篇 |
2022年 | 160篇 |
2021年 | 395篇 |
2020年 | 269篇 |
2019年 | 452篇 |
2018年 | 511篇 |
2017年 | 411篇 |
2016年 | 433篇 |
2015年 | 525篇 |
2014年 | 821篇 |
2013年 | 1360篇 |
2012年 | 1971篇 |
2011年 | 2106篇 |
2010年 | 1158篇 |
2009年 | 1184篇 |
2008年 | 2041篇 |
2007年 | 2268篇 |
2006年 | 2266篇 |
2005年 | 2173篇 |
2004年 | 2144篇 |
2003年 | 2026篇 |
2002年 | 1989篇 |
2001年 | 302篇 |
2000年 | 195篇 |
1999年 | 316篇 |
1998年 | 445篇 |
1997年 | 369篇 |
1996年 | 345篇 |
1995年 | 298篇 |
1994年 | 282篇 |
1993年 | 265篇 |
1992年 | 162篇 |
1991年 | 186篇 |
1990年 | 156篇 |
1989年 | 146篇 |
1988年 | 133篇 |
1987年 | 133篇 |
1986年 | 115篇 |
1985年 | 165篇 |
1984年 | 213篇 |
1983年 | 160篇 |
1982年 | 242篇 |
1981年 | 244篇 |
1980年 | 233篇 |
1979年 | 110篇 |
1978年 | 105篇 |
1977年 | 105篇 |
1976年 | 82篇 |
1975年 | 72篇 |
1974年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Nuclear division and microgametogony ofEimeria nieschulzi were studied by transmission electron microscopy. All nuclear divisions occurred in close proximity to the gamont surface with four centrioles situated between the nuclear envelope and the gamont plasmalemma. During early nuclear divisions, each nucleus had a rod or hourglass-shaped nucleolus, indicating that the nucleolus probably pinched in two during nuclear division. Nuclear divisions occurred by nearly centrally located intranuclear spindles. Two centrioles were associated with each centrocone. Spindle microtubules, which originated from each centrocone, either traversed to the other centrocone or terminated at kinetochores. Four to 6 chromosome-like structures were present in each dividing nucleus. The formation of 50 to 100 biflagellate microgametes occurred at the margin of the microgamont by a process similar to that described for other coccidian species. Microgametes were limited by a single membrane with a prominent glycocalyx, 13 nm thick.Based on a thesis submitted by G.J. Sibert to the Graduate School of the University of Montana in partial fulfillment of the requirements for the Master of Science degree 相似文献
92.
Rabbits treated with benzo(a)pyrene developed cardiac arrhythmias when exposed by inhalation to 8100 ppm trichloroethylene or 15000 ppm halothane to a greater extent and at lower doses of epinephrine challenge than did controls. Benzo(a)pyrene and 3-methylcholanthrene both increased the metabolism of trichloroethylene, but 3-methylcholanthrene did not increase its cardiotoxic effect. The basis of the arrythmogenic action of benzo(a)pyrene appears to be unrelated to its ability to induce xenobiotic metabolism. 相似文献
93.
Colleen E. Kelley MD James Mathews MD Gary A. Noskin MD 《The Journal of emergency medicine》1991,9(6):417-420
Acute transverse myelitis (ATM) is a neurologic condition that presents with bilateral lower extremity weakness and sensory loss associated with bowel and bladder dysfunction. Whereas the time of onset may be hours to days, the time to either partial or complete recovery may require months. The etiology is varied and may be idiopathic. Laboratory and radiographic evaluation may be nonrevealing. Corticosteriods have been used for treatment, but their efficacy is controversial. As illustrated by this case report, the essential aspect of the initial management of ATM is the elimination of potentially treatable causes. 相似文献
94.
Carter R Coberley Gary A Puckrein Angela C Dobbs Matthew A McGinnis Sadie S Coberley Dexter W Shurney 《Disease management》2007,10(3):147-155
In addition to race and ethnicity, specific geographic regions are associated with poorer outcomes of care. Individuals with diabetes experiencing health disparities typically have worse long-term outcomes, such as increased diabetes complications and mortality. Zip code mapping, or geocoding, was utilized in this study to identify regions of the United States with high diabetes prevalence rates and to identify areas with high densities of minority populations. Use of this methodology to examine the effect of disease management on a large, diverse diabetes population revealed greater improvement in clinical testing rates in health disparity zones compared with members living outside of these areas. In particular, significant improvement was achieved by members living in minority zip codes and by members aged 65 years or older. These findings demonstrate that members living in areas of health disparity obtain even greater benefit from diabetes disease management program participation, helping to reduce gaps in care. 相似文献
95.
Patrick P. A. Humphrey Gary Buell Ian Kennedy Baljit S. Khakh Anton D. Michel Annmarie Surprenant Derek J. Trezise 《Naunyn-Schmiedeberg's archives of pharmacology》1995,352(6):585-596
Significant advances in understanding of P2X purinoceptor pharmacology have been made in the last few years. The limitations of nucleotide agonists as drug tools have now been amply demonstrated. Fortunately, inhibitors of the degrading ecto-ATPase enzymes are becoming available and it has become apparent that the complete removal of all divalent cations can be used experimentally in some systems to prevent nucleotide breakdown. Despite these issues, convincing evidence for P2X receptor heterogeneity, from data with agonists, has recently been reported.A number of new antagonists at P2X purinoceptors have also recently been described which to some degree appear to be more specific and useful than earlier antagonists like suramin. It is now apparent that suramin is a poor antagonist of ATP in many tissues because it potently inhibits ATPase activity at similar concentrations to those at which it blocks the P2X purinoceptor.Advances in the use of radiolabelled nucleotides as radioligands for binding studies has allowed the demonstration of P2X purinoceptors in a variety of tissues throughout the body including the brain. These studies have also provided evidence for receptor heterogeneity. Excitingly, two P2X purinoceptor genes have been cloned but operational studies suggest that more than two types exist. The cloning studies have also demonstrated a unique structure for the P2X purinoceptor which differentiates it from all other ligand-gated ion channel receptors. Further studies on P2X purinoceptor operation and structure are needed to help resolve controversies alluded to regarding the characterization and classification of nucleotide receptors. Hopefully such studies will also lead to a better understanding of the physiological and pathological importance of ATP and its activation of P2X purinoceptors. This will require the identification of better drug tools, in particular antagonists which may also provide the basis for novel therapeutic agents. 相似文献
96.
97.
98.
In Vivo Induction of Virulence and Antibiotic Resistance Transfer in Enterococcus faecalis Mediated by the Sex Pheromone-Sensing System of pCF10 总被引:1,自引:0,他引:1 下载免费PDF全文
Enterococcus faecalis has become one of the most notable nosocomial pathogens in the last decade. Aggregation substance (AS) on the sex pheromone plasmids of E. faecalis has been implicated as a virulence factor in several model systems. We investigated the AS-encoding plasmid pCF10 for its ability to increase virulence in a rabbit endocarditis model. Cells containing pCF10 increased the virulence in the model significantly, as assessed by an increase in aortic valve vegetation size. The results confirmed in vivo induction of the normally tightly controlled AS. In addition to the expression of AS when E. faecalis cells were in contact with plasma, plasmid transfer of the tetracycline resistance-carrying plasmid was also activated in vitro and in vivo. In vivo, plasmid transfer reached remarkable frequencies of 8 x 10(-2) to 9 x 10(-2). These values are comparable to the highest frequencies ever observed in vitro. Cells harboring pCF10 had a significant survival advantage over plasmid-free cells indicated by pCF10 present in two-thirds of the recipient population. Plasma induction was dependent on the presence of the plasmid-encoded PrgZ protein, indicating the requirement of the pheromone-sensing system in the induction process. The data suggested that the mechanism of in vivo induction may involve interference of plasma with the normal function of the pheromone peptide and its inhibitor. 相似文献
99.
Cardia: study design, recruitment, and some characteristics of the examined subjects 总被引:28,自引:0,他引:28
Gary D. Friedman Gary R. Cutter Richard P. Donahue Glenn H. Hughes Stephen B. Hulley David R. Jacobs Jr. Kiang Liu Peter J. Savage 《Journal of clinical epidemiology》1988,41(11):1105-1116
In 1984, a prospective cohort study, Coronary Artery Risk Development in Young Adults (CARDIA) was initiated to investigate life-style and other factors that influence, favorably and unfavorably, the evolution of coronary heart disease risk factors during young adulthood. After a year of planning and protocol development, 5,116 black and white women and men, age 18-30 years, were recruited and examined in four urban areas: Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota, and Oakland, California. The initial examination included carefully standardized measurements of major risk factors as well as assessments of psychosocial, dietary, and exercise-related characteristics that might influence them, or that might be independent risk factors. This report presents the recruitment and examination methods as well as the mean levels of blood pressure, total plasma cholesterol, height, weight and body mass index, and the prevalence of cigarette smoking by age, sex, race and educational level. Compared to recent national samples, smoking is less prevalent in CARDIA participants, and weight tends to be greater. Cholesterol levels are representative and somewhat lower blood pressures in CARDIA are probably, at least in part, due to differences in measurement methods. Especially noteworthy among several differences in risk factor levels by demographic subgroup, were a higher body mass index among black than white women and much higher prevalence of cigarette smoking among persons with no more than a high school education than among those with more education. 相似文献
100.