全文获取类型
收费全文 | 345345篇 |
免费 | 46803篇 |
国内免费 | 2101篇 |
专业分类
耳鼻咽喉 | 4981篇 |
儿科学 | 9030篇 |
妇产科学 | 7808篇 |
基础医学 | 34821篇 |
口腔科学 | 9441篇 |
临床医学 | 54522篇 |
内科学 | 75894篇 |
皮肤病学 | 6494篇 |
神经病学 | 35260篇 |
特种医学 | 11709篇 |
外国民族医学 | 11篇 |
外科学 | 54857篇 |
综合类 | 3583篇 |
现状与发展 | 40篇 |
一般理论 | 318篇 |
预防医学 | 34017篇 |
眼科学 | 8491篇 |
药学 | 17737篇 |
6篇 | |
中国医学 | 365篇 |
肿瘤学 | 24864篇 |
出版年
2024年 | 855篇 |
2023年 | 6094篇 |
2022年 | 3340篇 |
2021年 | 7795篇 |
2020年 | 8143篇 |
2019年 | 7035篇 |
2018年 | 12403篇 |
2017年 | 11390篇 |
2016年 | 12369篇 |
2015年 | 13359篇 |
2014年 | 18434篇 |
2013年 | 23254篇 |
2012年 | 21254篇 |
2011年 | 22093篇 |
2010年 | 17093篇 |
2009年 | 18233篇 |
2008年 | 19839篇 |
2007年 | 19659篇 |
2006年 | 20611篇 |
2005年 | 19191篇 |
2004年 | 17566篇 |
2003年 | 16120篇 |
2002年 | 15028篇 |
2001年 | 3965篇 |
2000年 | 2763篇 |
1999年 | 4020篇 |
1998年 | 5230篇 |
1997年 | 4702篇 |
1996年 | 4314篇 |
1995年 | 3948篇 |
1994年 | 2977篇 |
1993年 | 2622篇 |
1992年 | 2097篇 |
1991年 | 1887篇 |
1990年 | 1603篇 |
1989年 | 1566篇 |
1988年 | 1537篇 |
1987年 | 1382篇 |
1986年 | 1369篇 |
1985年 | 1348篇 |
1984年 | 1522篇 |
1983年 | 1468篇 |
1982年 | 1647篇 |
1981年 | 1572篇 |
1980年 | 1302篇 |
1979年 | 829篇 |
1978年 | 910篇 |
1977年 | 802篇 |
1976年 | 725篇 |
1974年 | 568篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
Alfred E Buxton Hugh Calkins David J Callans John P DiMarco John D Fisher H Leon Greene David E Haines David L Hayes Paul A Heidenreich John M Miller Athena Poppas Eric N Prystowsky Mark H Schoenfeld Peter J Zimetbaum Paul A Heidenreich David C Goff Frederick L Grover David J Malenka Eric D Peterson Martha J Radford Rita F Redberg 《Journal of the American College of Cardiology》2006,48(11):2360-2396
992.
David B. Burr PhD 《Clinical reviews in bone and mineral metabolism》2006,4(3):155-166
Therapeutic agents used to treat osteoporosis reduce the incidence of vertebral and nonvertebral fractures in osteoporotic
women. The antiremodeling agents, such as the bisphosphonates, prevent bone loss by suppressing the remodeling rate, perhaps
increasing bone volume slightly, and increasing mineralization of the tissue. The anabolic agents, of which rhPTH(1–34) is
the only one approved, accomplish this in a manner that is almost completely the opposite in terms of biological process.
rhPTH(1–34) causes net bone gain by stimulating both modeling and remodeling, by increasing bone volume significantly through
direct bone apposition to trabecular and endocortical surfaces, and by reducing the mean degree of tissue mineralization (a
natural consequence of enhanced remodeling). Each of these treatments maintains or increases bone strength and is similarly
effective at preventing fractures. However, because of their different mode of action, each has different consequences for
bone matrix quality (defined here by microdamage accumulation and by the properties of mineral and collagen) and the mechanical
properties of the tissue. Although bone's composite nature makes it a relatively tough material—more like fiberglass than
glass—the accumulation of damage will nevertheless reduce its residual mechanical properties until the damage is repaired
through remodeling. Agents that suppress remodeling are associated with both microdamage accumulation and increased mineralization.
The biological importance of damage and mineralization to bone's mechanical properties is still a source of debate. 相似文献
993.
994.
995.
996.
Hirotsugu Yamada MD PhD Zoran B. Popovic MD PhD David O. Martin MD MPH Kenneth C. Civello MD MPH Don W. Wallick PhD 《Heart rhythm》2006,3(6):722-727
BACKGROUND: Coupled pacing (CP), which consists of delivering a premature electrical stimulation to the heart after the effective refractory period of ventricular activation, is a novel method for controlling ventricular rate during atrial fibrillation (AF). It also has been established that CP improves pump function by enhancing external cardiac work and myocardial efficiency. OBJECTIVE: The purpose of the present study was to determine if two time delays for CP (short and long) would result in similar improvements in ventricular function. METHODS: In a canine model, we applied CP at two time delays (CP-S and CP-L) during two stages: sinus rhythm (SR) and acute AF. The cardiac responses to CP during SR served as the nontachycardic and nondepressed control. During both rhythms, we shortened the coupling interval until we obtained maximal contractility, designated CP-S. Next, we increased the delay until we started to see a measurable secondary contraction (left ventricular pressure development of approximately 20 mmHg). These longer delays were designated CP-L. RESULTS: Our results showed that the ventricular rate of intrinsic activation (VRIA) remained decreased despite prolongation of the time delay of CP during both AF and SR. Also, both delays of CP increased left ventricular systolic pressure (LVSP) and dLVP/dt, which are indices of myocardial contractility. In contrast, CP increased external cardiac work only during AF. Prolonging this time delay did not markedly decrease the improvement in external cardiac work. Myocardial O(2) consumption (MVO(2)) did not significantly change as the result of CP during either SR or AF. Finally, myocardial efficiency improved during AF as the result of CP at both time delays. CONCLUSIONS: In conclusion, shorter time delays for CP increased contractile strength during both SR and AF. However, extending the time delay of CP had minimal effects on diminishing the improved ventricular pump function and energetics that resulted from CP during AF. Thus, the maximal enhancement of myocardial contractility via CP-S was not needed to maintain the improved ventricular function during acute AF when CP is applied. 相似文献
997.
Joseph Cofrancesco Nina Shah Khalil G Ghanem Adrian S Dobs Robert S Klein Kenneth Mayer Paula Schuman David Vlahov Anne M Rompalo 《Gynecological endocrinology》2006,22(5):244-251
Drug use and HIV infection may affect sex hormone levels in women. One hundred and ninety-six women with and without a history of illicit drug use (50 HIV-negative and 148 HIV-infected), with regular menses, who never used antiretrovirals, were evaluated. Luteinizing hormone levels were significantly higher in women with a CD4 cell count <200/microl (p < 0.002). Current methadone use was associated with lower levels of total testosterone (p = 0.03) and higher levels of prolactin (p = 0.002); mean estradiol levels were 43% lower in women who used intravenous drugs (p < 0.001). Alcohol and crack cocaine use was not associated with sex hormone levels. Age, race, body mass index and degree of HIV immunosuppression were also associated with differences in sex hormone levels. 相似文献
998.
Rebecca M. Schwartz PhD Edmond S. Malka Michael Augenbraun Steven Rubin Matthew Hogben Nicole Liddon William M. McCormack Tracey E. Wilson 《Journal of urban health》2006,83(6):1095-1104
Efforts to control chlamydial and gonococcal infections include notifying eligible sexual partners of possible infection,
primarily by asking the diagnosed patient to notify their partners. This approach, known as patient referral, is widely used
but poorly understood. The current study examined psychosocial and cognitive factors associated with patient referral among
an urban, minority sample of 168 participants recently diagnosed with Chlamydia trachomatis or Neisseria gonorrhoeae. At a follow-up interview 1-month from diagnosis, participants were more likely to have notified all eligible partners if
they had greater intention to notify at baseline (OR = 3.72; 95% CI = 1.34, 10.30) and if they had only one partner at baseline
(OR = 4.08; 95% CI = 1.61, 10.31). There were also gender differences as well as differences based on type of partner (i.e.,
regular, casual, one-time). The implications of these findings for the design of programs to promote patient referral for
sexually transmitted infections are discussed.
Schwartz, Malka, Augenbraun, McCormack, and Wilson are with the State University of New York, Downstate Medical Center, Brooklyn,
NY, USA; Rubin is with the New York City Department of Health, Bureau of STD Control, New York, NY, USA; Rubin, Hogben, and
Liddon are with the Centers for Disease Control and Prevention, Atlanta, GA, USA; Schwartz is with the Department of Preventive
Medicine and Community Health, SUNY Downstate Medical Center, Box 1240, 450 Clarkson Avenue, Brooklyn, NY 11203, USA. 相似文献
999.
1000.