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   10811篇
  免费   821篇
  国内免费   41篇
耳鼻咽喉   135篇
儿科学   338篇
妇产科学   286篇
基础医学   1594篇
口腔科学   231篇
临床医学   1065篇
内科学   2206篇
皮肤病学   144篇
神经病学   895篇
特种医学   237篇
外科学   1251篇
综合类   285篇
现状与发展   1篇
一般理论   9篇
预防医学   1145篇
眼科学   220篇
药学   1002篇
中国医学   29篇
肿瘤学   600篇
  2022年   136篇
  2021年   255篇
  2020年   131篇
  2019年   174篇
  2018年   214篇
  2017年   143篇
  2016年   205篇
  2015年   207篇
  2014年   240篇
  2013年   489篇
  2012年   653篇
  2011年   690篇
  2010年   380篇
  2009年   345篇
  2008年   569篇
  2007年   587篇
  2006年   572篇
  2005年   554篇
  2004年   525篇
  2003年   490篇
  2002年   525篇
  2001年   258篇
  2000年   204篇
  1999年   206篇
  1998年   101篇
  1997年   114篇
  1996年   111篇
  1995年   94篇
  1994年   74篇
  1993年   68篇
  1992年   161篇
  1991年   140篇
  1990年   123篇
  1989年   109篇
  1988年   126篇
  1987年   126篇
  1986年   113篇
  1985年   100篇
  1984年   96篇
  1983年   91篇
  1982年   78篇
  1981年   89篇
  1980年   74篇
  1979年   75篇
  1978年   63篇
  1977年   55篇
  1976年   62篇
  1974年   62篇
  1973年   54篇
  1972年   59篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
91.
The cost of building, installing, and maintaining a full hospital laboratory communication system is expensive. Using an outside accountant, our books were audited to determine the expenses in each of our major cost centers. These data are tabulated along with services provided. Although the initial expenditures are high, the actual cost per test for full service capability is somewhere between 13 and 17 cents. If viewed as a cost per patient day, the price ranges between 59 and 85 cents.  相似文献   
92.
Attempts to repopulate the retina with grafted neurons have been unsuccessful, in large part because donor cells prefer not to integrate with those of the host. Here we describe the first use of neural progenitor cells in the diseased adult retina. Adult rat hippocampal progenitor cells were injected into the eyes of rats with a genetic retinal degeneration. After survival times up to 16 weeks, the retinae of 1-, 4-, and 10-week-old recipients exhibited widespread incorporation of green fluorescent protein-expressing (GFP+) donor cells into the host retina. The 18-week-old recipients showed a similar pattern, but with fewer cells. Grafted cells expressed the mature neuronal markers NF-200, MAP-5, and calbindin. GFP+ cells extended numerous neurites into the host plexiform layers and these processes were intimately associated with synaptophysin+ profiles. GFP+ neurites also extended into the host optic nerve head. These results demonstrate the differentiation of substantial numbers of new neurons within the mature dystrophic retina.  相似文献   
93.
94.
95.
We report the case of a 13-year-old boy who presented with deafness due to a posterior fossa cystic lesion which was surgically excised. Histological examination showed it to be an enterogenous cyst. These extremely rare lesions seldom occur within the neural axis.  相似文献   
96.
Accepted 30 January 1997
OBJECTIVE—To evaluate the efficiency of the screening programme for congenital hypothyroidism in Scotland and to determine the outcome in the cohort of children with positive testing for thyroid stimulating hormone (TSH).
DESIGN—Establishment of comprehensive database for all Scottish infants with high TSH, detected on Guthrie screening.
SUBJECTS—344 infants born between August 1979 and December 1993 with TSH greater than 40 mU/l on initial Guthrie, or 15-40 mU/l on repeat Guthrie.
MAIN OUTCOME MEASURES—Ages at time of: (a) Guthrie collection, (b) notification of positive result by laboratory, and (c) start of treatment; audit of late diagnosis/missed cases; categorisation of positive cases into definite and probable congenital hypothyroidism, transient TSH elevation, and uncertain status; educational status of children with definite and probable congenital hypothyroidism.
RESULTS—344 positive cases were categorised as having definite (224) and probable (11) congenital hypothyroidism, transient TSH elevation (88), and status uncertain (21). The overall incidence of definite/probable congenital hypothyroidism was 1 in 4400 live births. For the definite/probable groups median age of Guthrie collection was consistently between 6 and 7 days from 1983 onwards but for the whole cohort was later than 10 days in 10.5%. Median age of notification fell from 14days in 1980 to 11 days in 1993. Median age of starting treatment ranged between 11 and 15 days from 1983 onwards. Treatment was delayed in four cases, three due to failed or late Guthrie card submission. Of 149 children with definite/probable congenital hypothyroidism who were of school age, educational status was ascertained in 139 (93%). Only two children (1.4%) were attending special school, one of whom was known to have mild hypothyroidism. Sixteen children (11.5%) were receiving extra help in mainstream education compared with 18% of control children in the Scottish very low birth weight study.
CONCLUSION—The current screening programme is working well, but efficiency could be increased by earlier and more reliable Guthrie collection. A substantial proportion of children picked up on the screening programme have a transient rise in TSH rather than true congenital hypothyroidism. The incidence of special education and learning support in Scottish children with congenital hypothyroidism appears to be no different to that of the general population.

  相似文献   
97.
Context  Cisapride, a gastrointestinal tract promotility agent, can cause life-threatening cardiac arrhythmias in patients susceptible either because of concurrent use of medications that interfere with cisapride metabolism or prolong the QT interval or because of the presence of other diseases that predispose to such arrhythmias. In June 1998, the US Food and Drug Administration (FDA) determined that use of cisapride was contraindicated in such patients and informed practitioners through additions to the boxed warning in the label and a "Dear Health Care Professional" letter sent by the drug's manufacturer. Objective  To evaluate the impact of the FDA's 1998 regulatory action regarding contraindicated use of cisapride. Design and Setting  Analysis of data for the 1-year periods before (July 1997-June 1998) and after (July 1998-June 1999) the regulatory action from the population-based, pharmacoepidemiology research databases of 2 managed care organizations (sites A and B) and a state Medicaid program (site C). Participants  Patients with at least 180 days of prior enrollment in 1 of the 3 sites who were prescribed cisapride at least once in the period before (n = 24 840) or after (n = 22 459) regulatory action. Patients could be included in both cohorts. Main Outcome Measures  Proportion of cisapride users in each period for whom cisapride use was contraindicated by the product label, based on computerized patient medical encounter records. Results  In the year prior to regulatory action, cisapride use was contraindicated for 26%, 30%, and 60% of users in study sites A, B, and C, respectively. In the year after regulatory action, use was contraindicated for 24%, 28%, and 58% of users, a reduction in contraindicated use of approximately 2 per 100 cisapride users at each site. When the analysis was restricted to new users of cisapride after regulatory action, only minor reductions in contraindicated use were found. Conclusion  The FDA's 1998 regulatory action regarding cisapride use had no material effect on contraindicated cisapride use. More effective ways to communicate new information about drug safety are needed.   相似文献   
98.
Objectives: Trends in first-time and later PSA procedure rates are ascertained using longitudinal data from a population-based cohort. These trends are compared to trends in prostate cancer incidence to determine the role of PSA in the recent decline in prostate cancer incidence.Methods: Medicare data were linked with tumor registry data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) Program. A 5 percent random sample (n=39985) of Medicare beneficiaries from the SEER areas without a previous diagnosis of prostate cancer as of January 1, 1988 was followed through 1994. Trends in first-time PSA use were distinguished from those of second or later for men without diagnosed prostate cancer.Results: Trends in the rate of first-time PSA procedures track closely with trends in prostate cancer incidence rates, increasing until 1992 and decreasing thereafter. Similar patterns were observed by race and age group. Geographic variability in the dissemination of PSA screening was observed, yet the association between testing and incidence remained. Men in the cohort had a 4.7 percent chance of being diagnosed within three months of an initial PSA test, with the percentage falling for subsequent tests.Conclusions: It is informative to distinguish first from later tests when assessing the effect of the diffusion of a test in a population. Taking this approach was useful in illuminating the role of PSA testing in a reversal of a long-term increase in prostate cancer incidence rates.  相似文献   
99.
Thirty-four consecutive women undergoing endometrial laser ablation, as a treatment of menorrhagia, were recruited to assess the validity of fluid absorption monitoring by a new continuous automated system (AquaSens). The same group of women also had monitoring of fluid absorption carried out by our standard technique of weighing. The intra-class correlation coefficient for the fluid deficit estimated by AquaSens compared to our standard technique of manually weighing the irrigation bags was 0.98 (95% CI 0.96–0.99). Aquasens therefore provides a valid and non-invasive method of continuously monitoring fluid deficit amongst patients undergoing operative hysteroscopy procedures, thereby reducing the risk of unexpected fluid absorption and its potentially fatal sequelae.  相似文献   
100.
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