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   251039篇
  免费   12583篇
  国内免费   510篇
耳鼻咽喉   3185篇
儿科学   7647篇
妇产科学   5235篇
基础医学   35746篇
口腔科学   5697篇
临床医学   20004篇
内科学   56266篇
皮肤病学   6542篇
神经病学   22432篇
特种医学   7551篇
外国民族医学   101篇
外科学   31220篇
综合类   1226篇
一般理论   72篇
预防医学   22833篇
眼科学   4866篇
药学   17616篇
中国医学   727篇
肿瘤学   15166篇
  2023年   1371篇
  2022年   1184篇
  2021年   4120篇
  2020年   2356篇
  2019年   4442篇
  2018年   8015篇
  2017年   5268篇
  2016年   5261篇
  2015年   5889篇
  2014年   6439篇
  2013年   10087篇
  2012年   17467篇
  2011年   17457篇
  2010年   8783篇
  2009年   6692篇
  2008年   14899篇
  2007年   15944篇
  2006年   14611篇
  2005年   14468篇
  2004年   13566篇
  2003年   12328篇
  2002年   11705篇
  2001年   6214篇
  2000年   6308篇
  1999年   5642篇
  1998年   1052篇
  1997年   869篇
  1996年   797篇
  1995年   719篇
  1992年   3243篇
  1991年   2897篇
  1990年   2770篇
  1989年   2534篇
  1988年   2391篇
  1987年   2221篇
  1986年   2107篇
  1985年   1904篇
  1984年   1416篇
  1983年   1201篇
  1979年   1226篇
  1978年   869篇
  1977年   815篇
  1975年   819篇
  1974年   992篇
  1973年   999篇
  1972年   944篇
  1971年   932篇
  1970年   866篇
  1969年   908篇
  1968年   792篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
A cross-sectional study of 976 coloured subjects aged 15-64 years identified a population consuming a typical Western diet. Nutrient intake, determined by the 24-hour dietary recall method, reflected a diet high in fat (37% of total energy intake) and animal protein and a polyunsaturated/saturated fatty acid ratio of 0.85. Only 32.2% of men and 27.5% of women consumed a prudent diet (Keys score less than or equal to 28). The influence of this Western diet on serum total cholesterol (TC) levels was seen to be marked when participants with a high risk of developing coronary heart disease (CHD) were compared with those with a TC level putting them at low risk; the former consumed significantly more saturated fat and had a higher mean Keys score. Multiple linear regression analysis on TC levels of men identified six variables that explained 26.9% of the variation of TC. These were body mass index, age, the inverse of the polyunsaturated fat intake, saturated fat intake, polyunsaturated/saturated fat ratio and cholesterol intake. For women only three variables (age, the inverse of the polyunsaturated/saturated fat ratio, and body mass index) explained 30.2% of the variation of TC. Promotion of the prudent diet to lower TC levels of the coloured population of the Cape Peninsula is an increasingly urgent priority.  相似文献   
993.
A group of 466 leukemic bone marrow transplanted patients were reported from 17 European bone marrow transplantation teams. Of these, 285 survived more than 3 months and could be evaluated for chronic GVHD. The cumulative incidence of chronic GVHD was 32% two years after BMT. The following factors were statistically significantly associated with chronic GVHD in bivariate analysis: high donor and recipient age, splenecacute GVHD, pretransplant seropositivity to CMV among the recipients and the donors, and donor seropositivity to 3 or 4 different herpesviruses, compared with 0-2, prior to BMT. In multivariate analysis pretransplant recipient CMV seropositivity in combination with donor CMV seropositivity prior to BMT (P = 0.0006), a previous grade II-IV acute GVHD (P = 0.001), and splenectomy (P = 0.01) were significantly associated with chronic GVHD. Thus, in addition to acute GVHD, CMV immune donor cells may be triggered by latent CMV in the recipient, which may play a role in the triggering of chronic GVHD. The possible role of splenectomy in GVHD is also discussed.  相似文献   
994.
To evaluate the potential advantages of the administration of extradural morphine to control postoperative pain and its effects on respiratory function, 39 patients were randomly assigned to one of two groups before aortic surgery. The first group (20 patients) received intravenous analgesia as required (control group). The second group (19 patients) received extradural morphine in a programmed fashion. During the immediate postoperative period the following parameters were measured in both groups: respiratory rate, vital capacity, peak expiratory volume in the first second, PaO2, PaCO2, arterial pH, heart rate, and systolic and diastolic blood pressure. In the group treated with morphine the postoperative increase in heart and respiratory rate was significantly smaller than in the control group (p less than 0.01). Postoperative forced pulmonary volumes were higher in the morphine group (p less than 0.01). However, there were no differences in time of hospitalization between both groups. There were more complications in the control group, but the difference did not reach statistical significance.  相似文献   
995.
In 1987, we reported the 1-year migration of the prosthetic components in 16 hips followed by roentgen stereophotogrammetry after fixation with either low- or high-viscosity cement. We now report the migration of these prosthetic components during another 2 postoperative years. Eight acetabular components, four in each group, migrated cranially; and four femoral components, three in the low-viscosity and one in the high-viscosity group, migrated distally. All but two migrations were obvious 4 months postoperatively, which indicates that what is called late loosening is the result of late detection rather than of late occurrence of loosening. Low-viscosity cement did not provide improved prosthetic fixation.  相似文献   
996.
997.
Summary Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for dopaminergic neurons. Since dopaminergic neurons degenerate in Parkinson's disease, this factor is a potential therapeutical tool that may save dopaminergic neurons during the pathological process. Moreover, a reduced GDNF expression may be involved in the pathophysiology of the disease. In this study, we tested whether altered GDNF production may participate in the mechanism of cell death in this disease. GDNF gene expression was analyzed by in situ hybridization using riboprobes corresponding to a sequence of the exon 2 human GDNF gene. Experiments were performed on tissue sections of the mesencephalon and the striatum from 8 patients with Parkinson's disease and 6 control subjects matched for age at death and for post mortem delay. No labelling was observed in either group of patients. This absence of detectable expression could not be attributed to methodological problems as a positive staining was observed using the same probes for sections of astroglioma biopsies from human adults and for sections of a newborn infant brain obtained at post-mortem. These data suggest that GDNF is probably expressed at a very low level in the adult human brain and its involvement in the pathophysiology of Parkinson's disease remains to be demonstrated. GDNF may represent a powerful new therapeutic agent for Parkinson's disease, however.  相似文献   
998.
79 patients with ischaemic stroke were investigated, with 31 patients showing a pure hemiparesis, 22 an additional depressive syndrome and 26 a dementia. After an average time intervall of 28 months, a follow-up investigation was performed on these 3 groups relative to their course and rehabilitation outcome. No significant differences were present between the 3 groups as regards age and sex distribution as well as hemisyndrome severity. The neurological and psychiatric findings at follow-up differed significantly from the primary findings. Also, significant differences were found in the degree of disability, and in the self- and family ratings of rehabilitation outcome, with a poorer long-term course, i.e. a higher degree of disability, significantly more frequent in the dementia group. Comparison of self- and family-ratings showed that self-ratings given were significantly worse in the dementia and depressive groups, whereas patients with purely neurological symptoms rated themselves better than their relatives did.  相似文献   
999.
In order to investigate the possibility of using [1-11C] labelled 3,4-dihydroxyphenylalanine (DOPA) and tyrosine as radiopharmaceuticals for the detection of eye melanoma, the biodistributions of the same 1- and 3-14C-labelled compounds were investigated in Syrian golden hamsters with Greene melanoma. The results of these investigations were compared with positron emission tomography (PET) images of 11C labelled DOPA and tyrosine. The synthesis of these 11C labelled compounds procures of DL mixture, from which D and L forms can be separated. One h after intravenous injection, both 14C labelled DL-, L- and D-DOPA showed a high uptake in tumour tissue, that of DL- and D-DOPA being the highest. These high uptakes, together with relatively low uptake in bone, skin and eye resulted in high tumour/non tumour ratio (for DL-DOPA 5.9, 4.5 and 6.6 respectively). Extraction of the tumour tissue with trichloroacetic acid showed that L-DOPA was mainly incorporated into melanin, whereas D-DOPA was not. Also, the uptake 1 h after intravenous injection of 1-14C-L- and DL-tyrosine into the tumour were high, but L- and DL- were less different; tumour/non tumour ratios were favorable. PET images of the tumour obtained 40-80 min after injection of the [1-11C] labelled DOPA and tyrosine confirmed that melanoma detection was promising and that D-DOPA produced a better melanoma image than L-DOPA.  相似文献   
1000.
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