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   1076135篇
  免费   71847篇
  国内免费   1369篇
耳鼻咽喉   15027篇
儿科学   34665篇
妇产科学   28640篇
基础医学   153581篇
口腔科学   29586篇
临床医学   95072篇
内科学   203915篇
皮肤病学   24479篇
神经病学   81522篇
特种医学   43057篇
外国民族医学   201篇
外科学   163288篇
综合类   21713篇
现状与发展   1篇
一般理论   263篇
预防医学   74657篇
眼科学   24559篇
药学   86206篇
  7篇
中国医学   2805篇
肿瘤学   66107篇
  2019年   7773篇
  2018年   11318篇
  2017年   8926篇
  2016年   10123篇
  2015年   11286篇
  2014年   15304篇
  2013年   22257篇
  2012年   30627篇
  2011年   32364篇
  2010年   18998篇
  2009年   17854篇
  2008年   30016篇
  2007年   32151篇
  2006年   32753篇
  2005年   31082篇
  2004年   29768篇
  2003年   28607篇
  2002年   27590篇
  2001年   60062篇
  2000年   61533篇
  1999年   50959篇
  1998年   12462篇
  1997年   11019篇
  1996年   11024篇
  1995年   10331篇
  1994年   9348篇
  1993年   8864篇
  1992年   37802篇
  1991年   36292篇
  1990年   35753篇
  1989年   34301篇
  1988年   30876篇
  1987年   29997篇
  1986年   28231篇
  1985年   26461篇
  1984年   19193篇
  1983年   16120篇
  1982年   8827篇
  1979年   17039篇
  1978年   11418篇
  1977年   10236篇
  1976年   8841篇
  1975年   10074篇
  1974年   11662篇
  1973年   11282篇
  1972年   10767篇
  1971年   10106篇
  1970年   9264篇
  1969年   8949篇
  1968年   7925篇
排序方式: 共有10000条查询结果,搜索用时 15 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