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   29521篇
  免费   2435篇
  国内免费   50篇
耳鼻咽喉   383篇
儿科学   768篇
妇产科学   859篇
基础医学   3996篇
口腔科学   1000篇
临床医学   2957篇
内科学   6714篇
皮肤病学   283篇
神经病学   3205篇
特种医学   1033篇
外国民族医学   2篇
外科学   3724篇
综合类   570篇
一般理论   18篇
预防医学   2195篇
眼科学   748篇
药学   1916篇
中国医学   11篇
肿瘤学   1624篇
  2021年   360篇
  2020年   213篇
  2019年   370篇
  2018年   424篇
  2017年   359篇
  2016年   367篇
  2015年   445篇
  2014年   621篇
  2013年   1072篇
  2012年   1431篇
  2011年   1533篇
  2010年   843篇
  2009年   875篇
  2008年   1477篇
  2007年   1622篇
  2006年   1664篇
  2005年   1640篇
  2004年   1529篇
  2003年   1458篇
  2002年   1495篇
  2001年   630篇
  2000年   621篇
  1999年   536篇
  1998年   381篇
  1997年   357篇
  1996年   316篇
  1995年   314篇
  1994年   274篇
  1993年   258篇
  1992年   445篇
  1991年   422篇
  1990年   472篇
  1989年   432篇
  1988年   463篇
  1987年   446篇
  1986年   396篇
  1985年   440篇
  1984年   375篇
  1983年   307篇
  1982年   323篇
  1981年   326篇
  1980年   238篇
  1979年   328篇
  1978年   255篇
  1977年   214篇
  1976年   180篇
  1975年   165篇
  1974年   245篇
  1973年   212篇
  1972年   182篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
The federal Medicare Diagnosis Related Group payment mechanism is undergoing constant change. Significant interest has been generated at the health policy level regarding reimbursement for patients with complications and comorbidities. The purpose of this study was to analyze hospital resource consumption for patients in the seventeen urology non-complicating condition (CC) stratified Diagnostic Related Groups (DRGs), currently 45 percent of urology DRGs. We analyzed 185 Medicare patients in these non-CC stratified urology DRGs and found that patients with more CCs per patient had higher total hospital costs per patient, financial risk under DRGs, a greater percentage of outliers, and a higher mortality, than patients in these same DRGs with fewer CCs per patient. These findings suggest that the current DRG system is inequitable to some patients and certain hospitals vis-a-vis non-CC stratified urology DRGs. The Health Care Financing Administration has not significantly changed the complicating condition urology DRG classification, as of its recent May, 1988 legislation. Financial disincentives to treat these patients may affect both their access and quality of care in the future.  相似文献   
72.
Inhalation of benzene produces a prolongation of mouse red blood cell glycerol hemolysis time. This was not observed in red blood cells directly incubated in benzene. Increased resistance to the hemolytic action of glycerol should be explored as a potentially useful biological monitoring procedure in the red blood cells of benzene-exposed humans.  相似文献   
73.
Federal regulations prescribe distinct protections for children participating in research studies. Procedures for collecting tissue specimens from children solely for research purposes must pose no more than a minor increase over minimum risk, thereby limiting the approvable correlative biologic studies to evaluate molecularly targeted agents in children with cancer. Ethical issues arise when approvable correlative studies are a mandatory component of an early-phase pediatric clinical trial of new anticancer agents. The National Cancer Institute Cancer Therapy Evaluation Program sponsored a workshop in 2002 to discuss tissue collection for correlative biologic studies in early-phase childhood cancer clinical studies of molecularly targeted agents. Workshop participants recommended the following: (1) tissue specimens for correlative studies should provide vital clinical and scientific results to qualify for early-phase pediatric study consideration; (2) parents should receive a realistic appraisal of the risks, requirements, and potential for benefit of phase I protocol participation; (3) investigators should clearly distinguish clinically necessary procedures from research procedures of no benefit to the child to improve correlative study informed consent; and (4) participation in correlative research studies included in clinical trials generally should be voluntary. The need to acquire important biologic data regarding new molecular agents will challenge the ingenuity of pediatric cancer researchers, necessitating the application of highly sensitive laboratory assay methods, new imaging procedures, and preclinical models of childhood cancer. Such innovative methods can allow necessary scientific information to be obtained while simultaneously respecting the protections appropriately afforded to children participating in research studies and minimizing the burden of research participation for children with cancer and their families.  相似文献   
74.
The comparative susceptibility of over 400 strains of aerobic and anaerobic pathogens, isolated from clinical specimens in late 1987 and early 1988, to imipenem and 15 other antimicrobial agents was studied using a uniform broth microdilution technique recommended by the National Committee for Clinical Laboratory Standards. Imipenem had the widest spectrum of activity and was consistently the most active agent tested. It was active against aerobic gram-positive cocci, aerobic gram-negative bacilli, and anaerobic bacteria.  相似文献   
75.
BACKGROUND: The aim of the study was to investigate the inhibitory control of an ongoing motor response and to identify underlying neural deficiencies, manifested in event-related potentials, that cause poorer inhibitory performance in children with attention-deficit/hyperactivity disorder. METHODS: A stop-signal paradigm with a primary visual task and auditory stop signal was used to compare performance in 13 children with attention-deficit/hyperactivity disorder and 13 control children, while event-related potentials were recorded simultaneously. RESULTS: Children with attention-deficit/hyperactivity disorder showed poorer inhibitory performance through a slower inhibitory process. Inhibitory processing of auditory stop signals was marked by a frontal N2 component that was reduced in the attention-deficit/hyperactivity disorder group relative to controls. A central positive component (P3) was associated with the success of inhibiting a response, but there were no group differences in its amplitude or latency. CONCLUSIONS: Findings support the hypothesis of deficient inhibitory control in children with attention-deficit/hyperactivity disorder. Slower inhibitory processing appears to be due to a specific neural deficiency that manifests in the processing of the stop signal as attenuated negativity in the N2 latency range.  相似文献   
76.
Cis-diammine dichloroplatinum (cisplatin) is an effective anticancerdrug which forms adducts with DNA, in both bacterial and mammaliancells. It is suspected of producing tumors as well. To determinethe molecular nature of geneti alterations induced by cisplatin,we cloned and sequenced cisplatin-induced mutants in the adeninephosphoribosyl-transferase (aprt) gene of Cinese hamster ovary(CHO) cells. Mutation by cisplatin appears to be targeted asthe sites of mutation are consistent with the known bindingspecificity of cisplatin. Many mutations occur at or proximalto the sequence 5'-AGG-3' and 5'-GAG-3' and include transversions,transitions, frameshifts and short deletions and duplications.Several double changes were also observed. No major rearrangementswere recovered in our collection. At several locations, a numberof mutants were found to be clustered within a small targetregion, but unlike traditional hotspots, tese represent diversechanges occurring in a localized region of a few base pairs.  相似文献   
77.
78.
79.
80.
The history of the European Community Atlas of “Avoidable Death” is given. Data from the second Atlas are presented. For all causes of death except asthma there was a decrease in mortality in the period 1980–1984 with respect to 1974–1978. Taking the EC as a whole as the standard (100) population the standardised mortality ratio (SMR) in Ireland in the period 1980-1984 for tuberculosis was 160, for asthma 180 and maternal mortality 58. Ireland had the highest mortality for tuberculosis in both time periods. Asthma mortality increased in all countries except Scotland between 1974–1978 and 1980–1984. Ireland had one of the highest declines in maternal mortality over the two time periods. Within Ireland tuberculosis mortality was highest in the Mid-Western Health Board and lowest in the North-Western Health Board. Asthma mortality was highest in the Western Health Board and lowest in the Mid-Western Health Board. Maternal mortality was highest in the Midland Health board and lowest in the Southern Health Board.  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