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   1263903篇
  免费   94817篇
  国内免费   1578篇
耳鼻咽喉   16313篇
儿科学   41001篇
妇产科学   34948篇
基础医学   189401篇
口腔科学   34731篇
临床医学   117752篇
内科学   247801篇
皮肤病学   27278篇
神经病学   101853篇
特种医学   46791篇
外国民族医学   265篇
外科学   178588篇
综合类   25749篇
现状与发展   3篇
一般理论   568篇
预防医学   104670篇
眼科学   28044篇
药学   92556篇
  7篇
中国医学   2022篇
肿瘤学   69957篇
  2018年   13531篇
  2017年   10392篇
  2016年   11325篇
  2015年   13080篇
  2014年   18002篇
  2013年   27487篇
  2012年   37574篇
  2011年   39974篇
  2010年   23055篇
  2009年   22251篇
  2008年   37756篇
  2007年   40383篇
  2006年   39965篇
  2005年   39100篇
  2004年   37550篇
  2003年   35960篇
  2002年   34872篇
  2001年   56035篇
  2000年   57045篇
  1999年   48099篇
  1998年   13396篇
  1997年   12223篇
  1996年   12643篇
  1995年   11915篇
  1994年   11107篇
  1993年   10399篇
  1992年   38200篇
  1991年   37671篇
  1990年   36446篇
  1989年   35260篇
  1988年   32691篇
  1987年   32027篇
  1986年   30525篇
  1985年   28786篇
  1984年   21941篇
  1983年   19192篇
  1982年   11365篇
  1981年   10321篇
  1979年   20944篇
  1978年   15393篇
  1977年   12790篇
  1976年   11845篇
  1975年   12810篇
  1974年   15588篇
  1973年   15362篇
  1972年   14512篇
  1971年   13552篇
  1970年   12786篇
  1969年   12065篇
  1968年   11229篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
With their unique perspectives in the identification, design, promotion, and evaluation of cancer patient education programs and services, the National Cancer Institute and the American Cancer Society have the abilities to meet a wide variety of cancer patient education needs. With federal support and connections to national organizations and the comprehensive and clinical cancer center networks, the National Cancer Institute has access to nationwide experts in medical care and the resources to develop, design, and promote quality, state-of-the-art education programs. The American Cancer Society, with its strong volunteer community base, can pull together local expertise and collaborate with local organizations to meet the special needs of local population groups. In addition, the American Cancer Society volunteer committees have the flexibility to individualize programming and resources to answer specific patient/family education problems. As the number of people affected by cancer continues to raise, and as organizations realize the need to maximize their resources with collaborative efforts, the National Cancer Institute and the American Cancer Society are challenged to focus their energies on the patient education initiatives that build upon and combine their unique strengths.  相似文献   
972.
Benzene is metabolized to one or more hematotoxic species. Saturation of benzene metabolism could limit the production of toxic species. Saturation of phase II enzymes involved in the conjugation of the phenolic metabolites of benzene also could affect the hematotoxicity of benzene. To investigate the latter possibility, we exposed male Swiss mice, via the inhalation route, to various concentrations of benzene for 6 h per day for 5 days. Following termination of the final exposure the mice were killed and the levels of phenylsulfate and phenylglucuronide in the blood determined. Spleen weights were recorded and the number of white blood cells counted. At low benzene exposure concentrations phenylsulfate is the major conjugated form of phenol in the blood. At high exposure concentrations, phenylglucuronide is the predominant species. The reductions in spleen weight and white blood cell numbers correlated with the concentration of phenylsulfate in the blood, but are most probably not causally related.  相似文献   
973.
P E Granum  M Richardson 《Toxicon》1991,29(7):898-900
Chymotrypsin treatment of the enterotoxin from Clostridium perfringens results in the loss of 36 amino acids from the N-terminus and 3 amino acids from the C-terminus. This processing results in a 3.2 fold increase in activity on Vero cells, which is close to what had been found for trypsin treatment following the loss of 25 amino acids from the N-terminus.  相似文献   
974.
The contributors performed a study of the blastomogenic properties of the heavy high vanadium oil processed at different temperatures. Skin applications of the oil and oil products in hybrid mice induced skin tumours in 27.5 (48.7%), pregastric--6.4 (7.6%), genital--15.4 (21.1%) cases. It was established that high temperatures of oil sublimation increased the benzopyrene contents and the oil products' blastomogenic activity.  相似文献   
975.
The aim of this study was to evaluate the public opinion towards the possible replacement of ration cards by cash payment and to investigate the effect of partial termination of food price subsidy programme on food consumption by families from different income brackets. A purposive sample of 300 families from Alexandria Governorates were interviewed to assess the attitude of the consumer towards the possible termination of current food subsidy programme. After one year, during which the subsidy programme was reduced, a follow up sample of 240 were interviewed. The results show that a large proportion of the families prefer the continuation of the current programme (80-81.2%), meanwhile, around 90% of them believed that subsidized foods do not reach the target group. The data show that subsidized meat and poultry are consumed by high income families while frozen subsidized fish was mostly consumed by poor families. The partial termination of the subsidy programme forced the families to reduce their consumption from sugar, tea, oil, and rice. During the second phase of the study. However the results show that high income families were least affected by the partial termination of the subsidy programme.  相似文献   
976.
977.
As part of a larger investigation to determine the effect of animal vs. plant proteins on the vitamin B-6 requirement of young women, clinical changes during vitamin B-6 depletion were documented. Eight healthy young women were confined to a metabolic unit and fed a defined formula diet nearly devoid of vitamin B-6 (less than 0.05 mg/d). Serial electroencephalographic (EEG) tracings, peripheral nervous system tests, periodontal evaluations, and biochemical measures of vitamin B-6 status were conducted. Within 12 d on the depletion diet, two of the eight women exhibited abnormal EEG tracings. These changes were readily reversed by repletion of vitamin B-6 at the 0.5-mg/d level. Biochemical measures reflected lowered vitamin B-6 status but were not predictive of the onset of EEG changes. No detectable alterations in oral or periodontal status were found, nor did plaque flora change markedly. This study is the first report of EEG changes occurring in women undergoing vitamin B-6 depletion and the first report to document EEG changes in adults within 12 d on a vitamin B-6-depletion regimen.  相似文献   
978.
979.
We conducted a retrospective study of 411 women to determine whether a significant relationship existed between method of infant feeding (breast vs bottle) and postpartum weight loss at 6 weeks and 12 months. In addition to method of infant feeding, the variables parity, gravidity, mode of delivery, maternal age, maternal prepregnancy weight, infant sex, and payment status (whether receiving assistance from the Aid to Dependent Children [ADC] program) were studied in terms of their association with weight loss. In general, no consistent relationship was found between method of infant feeding and postpartum weight loss. However, in the ADC group at 6 weeks and in the non-ADC group at 12 months, nonlactating women had lost more weight than had their lactating counterparts, in spite of the theoretical energy deficiency of breast-feeding women. Women who gained more weight during pregnancy consistently lost more weight following delivery, regardless of their prepregnancy weight. These results indicate that infant feeding method was not related to differences in postpartum weight loss between lactating and nonlactating counterparts.  相似文献   
980.
We evaluated the consistency of three questionnaire methods of assessing work and leisure activity in the rural biethnic population of the San Luis Valley Diabetes Study. A 7-d physical activity recall (PAR), a ranking of usual activity, and a history of usual participation in vigorous activity were used. Energy expenditure (kJ.kg-1.wk-1) (EE) was estimated from PAR. Subjects were 503 adults [49% non-Hispanic white (NHW), 51% Hispanic]. Physical activity at work rather than leisure-time activity largely determined total energy expenditure. Average EE at work increased with work rank for all subjects combined [mean EE (SEE) for rank 1 (low) = 324.2 (24.4), rank 4 (high) = 874.0 (102.1)] and within sex, ethnic, and occupational subgroups. Leisure EE increased with leisure rank only for NHW men and employed women. Similar patterns were observed in comparisons of PAR data with history of vigorous activity. Further development and validation of instruments appropriate for use across population subgroups are needed.  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