首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   17281篇
  免费   1762篇
  国内免费   37篇
耳鼻咽喉   143篇
儿科学   601篇
妇产科学   525篇
基础医学   2516篇
口腔科学   329篇
临床医学   2050篇
内科学   3338篇
皮肤病学   230篇
神经病学   1315篇
特种医学   748篇
外国民族医学   3篇
外科学   2065篇
综合类   390篇
一般理论   11篇
预防医学   1940篇
眼科学   375篇
药学   1313篇
  1篇
中国医学   12篇
肿瘤学   1175篇
  2021年   210篇
  2020年   152篇
  2019年   244篇
  2018年   264篇
  2017年   211篇
  2016年   240篇
  2015年   263篇
  2014年   358篇
  2013年   550篇
  2012年   707篇
  2011年   790篇
  2010年   507篇
  2009年   434篇
  2008年   678篇
  2007年   723篇
  2006年   647篇
  2005年   685篇
  2004年   665篇
  2003年   675篇
  2002年   582篇
  2001年   548篇
  2000年   552篇
  1999年   474篇
  1998年   275篇
  1997年   237篇
  1996年   206篇
  1995年   218篇
  1994年   178篇
  1993年   187篇
  1992年   411篇
  1991年   423篇
  1990年   422篇
  1989年   389篇
  1988年   407篇
  1987年   384篇
  1986年   335篇
  1985年   309篇
  1984年   266篇
  1983年   226篇
  1982年   137篇
  1980年   133篇
  1979年   220篇
  1978年   184篇
  1977年   153篇
  1976年   160篇
  1975年   159篇
  1974年   153篇
  1973年   175篇
  1972年   142篇
  1970年   137篇
排序方式: 共有10000条查询结果,搜索用时 5 毫秒
991.
992.
An extract of the roots of Angelica dahurica BENTH. et HOOK. (Umbelliferae) showed potential tyrosinase inhibition against mushroom tyrosinase. Employing a bioassay-linked HPLC method, followed by semipreparative HPLC, the active principle was isolated and characterized as 9-hydroxy-4-methoxypsoralen.  相似文献   
993.
994.
Partnering with a reference lab can actually help grow a referring lab's own business. The reference lab provides a hospital's physicians with access to unique tests and clinical information and broadens the scope and depth of the referring lab's menu. As medicine moves toward prescribed treatments based on a patient's individual genotype or phenotype, the reference lab will play an even bigger role in helping the hospital to educate physicians and their patients to the most efficient testing strategies consistent with good patient management.  相似文献   
995.
996.
There are many arguments to support the hypothesis that there is a causal relationship between the presence of endometriosis and subfertility. These arguments are reviewed in this article and include: (1) an increased prevalence of endometriosis in subfertile women compared with women of proven fertility; (2) a reduced monthly fecundity rate (MFR) in baboons with mild to severe (spontaneous or induced) endometriosis compared with those with minimal endometriosis or a normal pelvis; (3) a trend toward a reduced MFR in infertile women with minimal to mild endometriosis compared with women with unexplained infertility; (4) a dose-effect relationship: a negative correlation between the r-AFS stage of endometriosis and the monthly fecundity rate and crude pregnancy rate; (5) a reduced monthly fecundity rate and cumulative pregnancy rate after donor sperm insemination in women with minimal-mild endometriosis compared with those with a normal pelvis; (6) a reduced MFR after husband sperm insemination in women with minimal to mild endometriosis compared with those with a normal pelvis; (7) a reduced implantation rate per embryo after IVF in women with moderate to severe endometriosis compared with women with a normal pelvis; and (8) an increased monthly fecundity rate and cumulative pregnancy rate after surgical removal of minimal to mild endometriosis.  相似文献   
997.
998.
This paper focuses on patterns in the care of children and dependent elders, providing a new perspective to understand impairment in family caregiving. One concept from evolutionary theory, kin selection, has promise for providing a broad framework for understanding patterns of family caregiving. We present an application of the evolutionary model to the issue of family care decisions in the face of potential conflicts of interest. Specifically, a mathematical biological model, which was developed to understand self-preservation motivation, is applied to the kin investment decision. Using the evolutionary model, the main predictors of investment would be relatedness, reproductive value, and expected benefit from the care invested. The biological model accounts very simply for decisions between caring for an elder parent or caring for your own child, and for decisions by two daughters (one with a child, one childless) to care for an elder parent. The factors that form the basis of an evolutionary model (relatedness, reproductive value, and benefit from care) have not been widely investigated in family care studies, however, and this absence reveals new directions for future research.  相似文献   
999.
OBJECTIVE: Fetal alcohol syndrome (FAS) results in stillbirth, fetal growth restriction, and mental retardation with injury attributed to oxidative stress. Our objective was to identify signal transduction pathways expressed in a model of FAS and to quantify expression of c-fos, a gene in the stress signal pathway. STUDY DESIGN: Timed, pregnant C57Bl6/J mice were injected on E8 with saline solution or alcohol. RNA was extracted from decidua and embryo 6 and 24 hours later. Microarray analysis was used to screen gene pathways. Differential gene expression was confirmed using real-time polymerase chain reaction with results presented as the ratio of c-fos concentration to that of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). RESULTS: Differential gene expression between alcohol and control was noted for stress signal pathway genes including c-fos. Real-time polymerase chain reaction demonstrated that c-fos messenger RNA expression was greater in the alcohol than control decidua at 6 hours after injection (P<.01). This effect persisted at 24 hours (P<.01). There was no difference in c-fos expression in embryos whose mothers received alcohol versus control after 6 hours (P=.12) or 24 hours (P=.89). CONCLUSION: Alcohol administration during pregnancy results in differential gene expression in the stress signal pathway, particularly in c-fos. C-fos expression in the decidua increases from 6 to 24 hours after alcohol injection, but does not change in the embryo, which may contribute to alcohol-induced damage in FAS.  相似文献   
1000.
OBJECTIVE: To evaluate the effect of once-daily, extended-release tolterodine on urinary urgency in patients with overactive bladder. METHODS: Patients with urinary frequency (eight or more micturitions per 24 hours) and urge incontinence (five or more episodes per week) were randomized to oral treatment with tolterodine extended release 4 mg once daily (n=398) or placebo (n=374) for 12 weeks. Efficacy was assessed by use of patient perception evaluations. RESULTS: The results presented are a secondary analysis of this double-blind, placebo-controlled study. Of patients treated with tolterodine extended release, 44% reported improved urgency symptoms (compared with 32% for placebo), and 62% reported improved bladder symptoms (placebo, 48%) (both P<.001 compared with placebo). The odds of reducing urgency and improving bladder symptoms were 1.68 and 1.78 times greater, respectively, for patients in the tolterodine extended release group than for patients receiving placebo. In response to urgency, there was a more than six-fold increase in the proportion of patients able to finish a task before voiding in the tolterodine extended release group. The proportion of patients unable to hold urine upon experiencing urgency was also decreased by 58% with tolterodine, compared with 32% with placebo (P<.001). The proportion of patients reporting "much benefit" from treatment was greater for tolterodine extended release than for placebo (43% versus 24%; P<.001). The only adverse events with an incidence of greater than 5% were dry mouth, headache, and constipation, with only dry mouth markedly more frequent with tolterodine than with placebo. CONCLUSION: Tolterodine extended release has demonstrable efficacy in reducing the severity of urinary urgency and is associated with improvements in overactive bladder symptoms that are meaningful to patients.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号