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   1076496篇
  免费   71930篇
  国内免费   1368篇
耳鼻咽喉   15024篇
儿科学   34645篇
妇产科学   28658篇
基础医学   153688篇
口腔科学   29662篇
临床医学   95125篇
内科学   203976篇
皮肤病学   24411篇
神经病学   81630篇
特种医学   43029篇
外国民族医学   201篇
外科学   163245篇
综合类   21725篇
现状与发展   1篇
一般理论   263篇
预防医学   74798篇
眼科学   24549篇
药学   86176篇
  7篇
中国医学   2807篇
肿瘤学   66174篇
  2019年   7793篇
  2018年   11329篇
  2017年   8937篇
  2016年   10118篇
  2015年   11299篇
  2014年   15308篇
  2013年   22253篇
  2012年   30618篇
  2011年   32352篇
  2010年   18975篇
  2009年   17863篇
  2008年   30017篇
  2007年   32120篇
  2006年   32783篇
  2005年   31101篇
  2004年   29772篇
  2003年   28614篇
  2002年   27588篇
  2001年   60072篇
  2000年   61527篇
  1999年   50982篇
  1998年   12465篇
  1997年   11017篇
  1996年   11033篇
  1995年   10339篇
  1994年   9357篇
  1993年   8874篇
  1992年   37830篇
  1991年   36325篇
  1990年   35780篇
  1989年   34332篇
  1988年   30907篇
  1987年   30026篇
  1986年   28264篇
  1985年   26474篇
  1984年   19209篇
  1983年   16149篇
  1982年   8844篇
  1979年   17061篇
  1978年   11424篇
  1977年   10242篇
  1976年   8853篇
  1975年   10079篇
  1974年   11661篇
  1973年   11286篇
  1972年   10774篇
  1971年   10098篇
  1970年   9262篇
  1969年   8948篇
  1968年   7927篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
This study compared the results of reflex modification (RM)--an objective technique for assessing brainstem sensorineural processing--with those of auditory brainstem response (ABR) for a group of high-risk infants at comparable postconceptional ages. For the RM procedure, an eyeblink-eliciting tap to the glabella was presented either alone or accompanied by a brief 90dB SPL tone. 37 high-risk infants were tested with both RM and ABR at a mean postconceptional age of 37.3 weeks. Seven had an increased brainstem conduction time ('failed ABR') and eight did not exhibit significant reflex augmentation ('failed RM'), seven of whom also failed the ABR. These data provide evidence that sensory stimuli which affect the neural mechanisms responsible for the organization of the startle response and auditory processing share essential neural components.  相似文献   
992.
We report the two-dimensional and Doppler color flow mapping echocardiographic findings in a neonate with left circumflex coronary arteriovenous fistula to a left superior vena cava. Doppler color flow mapping, in concert with detailed imaging, was essential to identify this rare fistula and to prepare for therapeutic intervention at initial cardiac catheterization.  相似文献   
993.
The author's original approach to the early repair of cleft palate which consists in the use of the extended vomer flap is presented. The evolution of primary procedure under the influence of the philosophy of Malek and Psaume and all additional improvements of the author are described and illustrated. The early results (up to 6 years) of 40 palatoplasties performed at the ages of 3-6 months are roughly evaluated and discussed.  相似文献   
994.
Seven patients with Parkinson's disease who experienced severe motor fluctuations in response to levodopa were studied in detail with relation to the effect of dietary protein on their motor function. The levodopa dose for each patient was not changed during the period of study, and no other antiparkinsonian drugs were used. Regular and high-protein diets resulted in a marked elevation in the plasma concentrations of large neutral amino acids (LNAAs) that are known to compete with levodopa for transport across the blood-brain barrier. Despite elevated plasma levodopa levels, all patients with elevated LNAA levels experienced parkinsonian symptoms. When the amino acid level dropped while plasma levodopa levels were elevated, patients experienced relief of these symptoms. On a low-protein diet, LNAA levels remained low and all patients were consistently dyskinetic throughout the day, even though the mean plasma levodopa levels were somewhat lower than when the patients consumed a high-protein diet. A redistribution diet that is virtually protein free until supper and then unrestricted until bedtime is tolerated by patients because this simple manipulation permits near-normal daytime motor function.  相似文献   
995.
996.
This article documents a patient with lung carcinoma that produced three oncofetal antigens including alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and human chorionic gonadotropin (hCG). Serum AFP, CEA, and hCG-beta-subunit were extremely high--118,000 ng/ml, 133 ng/ml and 0.9 ng/ml, respectively. Immunohistochemical staining of these tumor markers revealed that these proteins were present in different cells. The pattern of lectin affinity electrophoresis of AFP resembled that of hepatocellular carcinoma. Also investigated was the reactivity of serum CEA to monoclonal antibodies against peptide or sugar moieties. Serum CEA values measured by antipeptide monoclonal antibodies were higher than those measured by antisugar monoclonal antibodies. The demonstration of AFP, CEA, and hCG in different tumor cells suggests that three genomes were not reactivated together in a cell, and the lung carcinoma probably consisted of at least three clones of cancer cells with different phenotypes.  相似文献   
997.
The biological response to ambient air pollution may be a function of specific combinations of pollutants. Groups of rabbits were exposed to NO2 (0.3 ppm or 1 ppm) with and without H2SO4 (0.5 mg/m3) for 2 hr/day for up to 14 days for assessment of effects upon mucociliary clearance of tracer particles from the tracheobronchial tree. Exposure to NO2 did not alter clearance, while exposure to H2SO4 produced a retardation toward the middle of the exposure series. The combination of 0.3 ppm NO2 with H2SO4 resulted in a speeding of clearance, while no change from control was seen with the mixture employing 1 ppm NO2 with acid. These results emphasize the importance of performing studies with pollutant mixtures, since it is not always possible to extrapolate responses from studies examining effects of individual pollutants.  相似文献   
998.
999.
1000.
In determining the role inter-study variation should play in an overview analysis, it is important to consider three factors: which question one is trying to answer; the degree of similarity or dissimilarity of design, and the degree to which heterogeneity of outcomes can be explained. Three questions one might be interested in are: whether treatment can be effective in some circumstances; whether treatment is effective on average, and whether treatment was effective on average in the trials at hand. Under the assumption of no qualitative interaction, the answers to these questions coincide. The O-E analysis most directly answers the third question. Other analyses are suggested when the first question is of interest, using the aspirin post-MI studies as an example.  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