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   2540篇
  免费   309篇
  国内免费   10篇
耳鼻咽喉   10篇
儿科学   75篇
妇产科学   33篇
基础医学   405篇
口腔科学   43篇
临床医学   364篇
内科学   534篇
皮肤病学   25篇
神经病学   193篇
特种医学   103篇
外科学   331篇
综合类   75篇
一般理论   1篇
预防医学   205篇
眼科学   92篇
药学   249篇
肿瘤学   121篇
  2023年   13篇
  2022年   21篇
  2021年   61篇
  2020年   29篇
  2019年   44篇
  2018年   61篇
  2017年   50篇
  2016年   50篇
  2015年   61篇
  2014年   82篇
  2013年   95篇
  2012年   133篇
  2011年   136篇
  2010年   69篇
  2009年   87篇
  2008年   133篇
  2007年   143篇
  2006年   130篇
  2005年   153篇
  2004年   133篇
  2003年   148篇
  2002年   138篇
  2001年   68篇
  2000年   58篇
  1999年   44篇
  1998年   47篇
  1997年   55篇
  1996年   50篇
  1995年   25篇
  1994年   54篇
  1993年   34篇
  1992年   32篇
  1991年   43篇
  1990年   30篇
  1989年   37篇
  1988年   29篇
  1987年   25篇
  1986年   17篇
  1985年   19篇
  1984年   17篇
  1983年   16篇
  1982年   15篇
  1981年   13篇
  1980年   15篇
  1979年   11篇
  1978年   18篇
  1976年   10篇
  1972年   12篇
  1971年   9篇
  1967年   12篇
排序方式: 共有2859条查询结果,搜索用时 15 毫秒
1.
2.
3.
Through understanding the relationships between the previous day's (Sunday) demand and the remaining days' demand, a prediction model can be constructed. The staff level can be determined based on this prediction model. This model can also be applied in different hospital units or a staff environment other than hospitals.  相似文献   
4.
OBJECTIVE: To identify the possible contribution of electromyogram (EMG) to scalp electroencephalogram (EEG) rhythms at rest and induced or evoked by cognitive tasks. METHODS: Scalp EEG recordings were made on two subjects in presence and absence of complete neuromuscular blockade, sparing the dominant arm. The subjects undertook cognitive tasks in both states to allow direct comparison of electrical recordings. RESULTS: EEG rhythms in the paralysed state differed significantly compared with the unparalysed state, with 10- to 200-fold differences in the power of frequencies above 20 Hz during paralysis. CONCLUSIONS: Most of the scalp EEG recording above 20 Hz is of EMG origin. Previous studies measuring gamma EEG need to be re-evaluated. SIGNIFICANCE: This has a significant impact on measurements of gamma rhythms from the scalp EEG in unparalysed humans. It is to be hoped that signal separation methods will be able to rectify this situation.  相似文献   
5.
Determining sufficient staff levels and providing quality, economical and efficient service is a problem that is difficult for some staffing managers to solve. The objectives in this paper are to derive a stochastic model for determining the necessary staff levels in various service environments such as hospitals, banks, or in manufacturing settings where the demand for a good staff is erratic. In order to assess the proper staff levels, an equation must be used which involves previous service demand hours that are considered as a distribution integrated within the statistical capability scale distribution. The most important property of this staffing model is that the results are independent of the mix of the jobs, the variation of the in-service time for jobs, and the stationary or nonstationary job arrival rate.  相似文献   
6.
Benign intracranial hypertension (BIH) is reported in three children from Australia and one from New Zealand, who were being treated with recombinant human growth hormone (rhGH). Three males and one female, aged between 10.5 and 14.2 y, developed intracranial hypertension within 2 weeks to 3 months of starting treatment. A national database, OZGROW, has been prospectively collecting data on all 3332 children treated with rhGH in Australia and New Zealand from January 1986 to 1996. The incidence of BIH in children treated with growth hormone (GH) is small, 1.2 per 1000 cases overall, but appears to be greater with biochemical GHD (<10IUml -1), i.e. 6.5/1000 (3 in 465 cases), relative risk 18.4, 95% confidence interval 1.9-176.1, than in all other children on the database. The incidence in patients with Turner's syndrome was 2.3/1000 (1 in 428 cases). No cases in patients with partial GHD (10–20 IUml -1) or chronic renal failure were identified. Possible causative mechanisms are discussed. The authors'practice is now to start GH replacement at less than the usual recommended dose of 14IUm-2 week-1 in those children considered to be at high risk of developing BIH. Ophthalmological evaluation is recommended for children before and during the first few months following commencement of rhGH therapy and is mandatory in the event of peripheral or facial oedema, persistent headaches, vomiting or visual symptoms. The absence of papilledema does not exclude the diagnosis.  相似文献   
7.
Epidemiological data from the United States of America (USA) indicate that the incidence and mortality of prostate cancer is higher among Black African-American men (AAM) than among White (Caucasian) American men (CAM). Earlier studies suggesting that prostate cancer is relatively rare among indigenous Black men in Africa are probably flawed by underreporting because recent studies indicate that the incidence rates among Black men are similar to those of White men living in Africa. The higher incidence of prostate cancer among AAM has been ascribed to racial differences in genetic susceptibility, dietary factors, or androgen metabolism. However, it may also be due to registration artefacts because in Africa the reported incidence rates of prostate cancer in different countries correlate directly with the per capita gross national product, suggesting improved access to medical facilities is responsible for higher reported incidence rates.

The greater prostate cancer mortality among AAM may result from higher tumour grade and stage and higher serum PSA at presentation, but it has also been suggested that prostate cancer is biologically more aggressive in AAM than in CAM. However, recent studies indicate that tumour grade and stage and serum PSA at presentation are similar in the races, with no difference in survival after multivariate analysis controlling for pretreatment cancer severity. This suggests that the higher prostate cancer mortality among AAM results from socio-economic factors and limited access to healthcare. Black men living inside as well as outside of Africa still tend to present with locally advanced or metastatic prostate cancer due to lack of early detection programmes.  相似文献   

8.
9.
Our recent report that fructose supported the metabolism of some, but not all axons, in the adult mouse optic nerve prompted us to investigate in detail fructose metabolism in this tissue, a typical central white matter tract, as these data imply efficient fructose metabolism in the central nervous system (CNS). In artificial cerebrospinal fluid containing 10 mmol/L glucose or 20 mmol/L fructose, the stimulus-evoked compound action potential (CAP) recorded from the optic nerve consisted of three stable peaks. Replacing 10 mmol/L glucose with 10 mmol/L fructose, however, caused delayed loss of the 1st CAP peak (the 2nd and 3rd CAP peaks were unaffected). Glycogen-derived metabolic substrate(s) temporarily sustained the 1st CAP peak in 10 mmol/L fructose, as depletion of tissue glycogen by a prior period of aglycaemia or high-frequency CAP discharge rendered fructose incapable of supporting the 1st CAP peak. Enzyme assays showed the presence of both hexokinase and fructokinase (both of which can phosphorylate fructose) in the optic nerve. In contrast, only hexokinase was expressed in cerebral cortex. Hexokinase in optic nerve had low affinity and low capacity with fructose as substrate, whereas fructokinase displayed high affinity and high capacity for fructose. These findings suggest an explanation for the curious fact that the fast conducting axons comprising the 1st peak of the CAP are not supported in 10 mmol/L fructose medium; these axons probably do not express fructokinase, a requirement for efficient fructose metabolism.  相似文献   
10.
Features of 111 mammary carcinomas derived from breast cancer screening were compared with those of 69 carcinomas presenting 'clinically'. Screen detected cancers were smaller, had less likelihood of nodal metastases, included a higher proportion of in situ tumours and if invasive, tended to be of lower grade. Using immunohistochemical methods, the expression of c-erbB-2 oncoprotein, epidermal growth factor receptor (EGFR) and cathepsin D were compared in the two groups. A similar proportion of screened and unscreened tumours expressed c-erbB-2 oncoprotein and EGFR but expression of the oestrogen regulated protein cathepsin D was significantly more frequent in the screened group (P less than 0.05). Although a relatively small series, the results suggest a biological difference between 'screened' and 'clinical' tumours.  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