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   5256篇
  免费   236篇
  国内免费   13篇
耳鼻咽喉   29篇
儿科学   170篇
妇产科学   152篇
基础医学   907篇
口腔科学   39篇
临床医学   459篇
内科学   1102篇
皮肤病学   362篇
神经病学   398篇
特种医学   87篇
外国民族医学   6篇
外科学   687篇
综合类   16篇
一般理论   1篇
预防医学   317篇
眼科学   94篇
药学   331篇
中国医学   5篇
肿瘤学   343篇
  2022年   31篇
  2021年   52篇
  2020年   27篇
  2019年   66篇
  2018年   75篇
  2017年   48篇
  2016年   54篇
  2015年   79篇
  2014年   96篇
  2013年   173篇
  2012年   277篇
  2011年   295篇
  2010年   185篇
  2009年   185篇
  2008年   324篇
  2007年   338篇
  2006年   339篇
  2005年   331篇
  2004年   365篇
  2003年   333篇
  2002年   320篇
  2001年   111篇
  2000年   105篇
  1999年   129篇
  1998年   82篇
  1997年   68篇
  1996年   78篇
  1995年   59篇
  1994年   53篇
  1993年   39篇
  1992年   75篇
  1991年   60篇
  1990年   58篇
  1989年   57篇
  1988年   50篇
  1987年   53篇
  1986年   45篇
  1985年   52篇
  1984年   35篇
  1983年   34篇
  1982年   26篇
  1981年   24篇
  1980年   17篇
  1979年   30篇
  1978年   15篇
  1977年   18篇
  1976年   18篇
  1973年   14篇
  1972年   14篇
  1971年   14篇
排序方式: 共有5505条查询结果,搜索用时 15 毫秒
1.
2.
3.
Synthetic amorphous silica (SAS) in its nanosized form is now used in food applications although the potential risks for human health have not been evaluated. In this study, genotoxicity and oxidative DNA damage of two pyrogenic (NM‐202 and 203) and two precipitated (NM‐200 and ‐201) nanosized SAS were investigated in vivo in rats following oral exposure. Male Sprague Dawley rats were exposed to 5, 10, or 20 mg/kg b.w./day for three days by gavage. DNA strand breaks and oxidative DNA damage were investigated in seven tissues (blood, bone marrow from femur, liver, spleen, kidney, duodenum, and colon) with the alkaline and the (Fpg)‐modified comet assays, respectively. Concomitantly, chromosomal damage was investigated in bone marrow and in colon with the micronucleus assay. Additionally, malondialdehyde (MDA), a lipid peroxidation marker, was measured in plasma. When required, a histopathological examination was also conducted. The results showed neither obvious DNA strand breaks nor oxidative damage with the comet assay, irrespective of the dose and the organ investigated. Similarly, no increases in chromosome damage in bone marrow or lipid peroxidation in plasma were detected. However, although the response was not dose‐dependent, a weak increase in the percentage of micronucleated cells was observed in the colon of rats treated with the two pyrogenic SAS at the lowest dose (5 mg/kg b.w./day). Additional data are required to confirm this result, considering in particular, the role of agglomeration/aggregation of SAS NMs in their uptake by intestinal cells. Environ. Mol. Mutagen. 56:218–227, 2015. © 2014 Wiley Periodicals, Inc.  相似文献   
4.
Several antisera specific to neuropeptides of vertebrates were applied to sections of the earthworm Eisenia fetida Sav. Some of them were able to reveal specific neurones of the supraoesophageal ganglion: h-GHRF, CRF, Leu- and Met-enkephalin, dynorphin, substance P, CCK-8, and CCK-8S. A map of different areas or nuclei was established in the brain, taking position of reactive cells into account. Four symmetrically paired nuclei and one mediodorsal nucleus were identified and plotted. There is generally no characteristic modification correlated with maturation of the worms. However, the reaction against anti-Leu-enkephalin differs significantly according to age of Eisenia in nucleus No. 1 and particularly in nuclei No. 2 where one cell group presents specific reactivity on and after puberty. Moreover, the successive application of two antisera to the same sections after elution showed no coexistence of substances in a single neurone. By comparison with these vertebrate peptide-like containing nerve cells, the assay to anti-5-HT showed only a few reactive aminergic neurones. An attempt of correlation of cellular types with reactive perikarya is started.  相似文献   
5.
The cellular infiltrate present in human diseased gingiva was analyzed in biopsies from 12 patients with gingivitis or periodontitis. The samples studied had been obtained in the course of surgery at inflammatory sites remaining after institution of periodontal treatment. Histological and immunological techniques were used to identify macrophages, B-cells, plasma-cells, T-cells and T cell subsets, as well as cells expressing class II HLA membrane antigens. T-cells appeared as the predominant population, but plasma-cells were also visualized in nearly all samples. Both OKT4+ and OKT8+ cells were seen in all cases, the latter being more numerous in periodontitis patients. Interdigitating-like cells were observed, positively labelled for class II antigens, as well as macrophages which were more numerous in periodontitis patients. These results suggest the participation of all components of the immune response in gingival disease, in a way resembling chronic recurrent inflammatory diseases.  相似文献   
6.
Between 1977 and 1987, 27 consecutive patients (16 men, 11 women, mean age 66 years, range 54 to 75 years) with ventricular septal rupture complicating acute myocardial infarction underwent surgical repair. The purpose of this retrospective study was to analyse the post-operative mortality factors from clinical, haemodynamic and operative data in all patients and also from coronary angiographic data in 23/27 patients whose haemodynamic status allowed this type of exploration. Seventeen patients (63 p. 100) died during the first post-operative month, 10 survived and were discharged. Factors that influenced the prognosis were: (1) inferiorly-located necrosis associated with a 75 p. 100 mortality rate (9 out of 12 patients), as opposed to 53 p. 100 (8 out of 15 patients) with anterior necrosis; (2) right ventricular dysfunction, observed in 83 p. 100 of patients with inferior necrosis and 53 p. 100 with anterior necrosis, which was responsible for 7 out of 9 deaths in the inferior necrosis subgroup and contributed to 3 out of 8 deaths in the anterior necrosis subgroup; this established a cause-effect relationship between right ventricular function and the overmortality of patients with inferior necrosis; (3) independently of the haemodynamic status, two- and three-vessel lesions (56 p. 100 of all lesions) which had an 84 p. 100 mortality rate as opposed to 40 p. 100 with one-vessel lesions; (4) the presence of a state of shock which was associated with a 78 p. 100 mortality rate as opposed to 55 p. 100 in patients without shock. We conclude that when permitted by the patient's haemodynamic status coronary angiography should be part of the pre-operative evaluation to assess the operative risk and guide the surgical procedure.  相似文献   
7.
8.
The present study has been conducted to ascertain the level of allelic variation at codon 129 of the prion protein gene in France. Six French populations have been studied (Paris, Lille, Rennes, Chambéry, Grasse and Perpignan), totalling 1374 normal subjects. Mean heterozygosity in France is 46.5%, and the mean Met 129 allele (a high risk susceptibility factor for Creutzfeldt-Jakob disease) is 0.674. There is a genetic heterogeneity (chi(2)=38.44, p<0.001) between the six populations compared, and Met allele frequencies are inversely correlated with latitude (r=-0.93, p<0.01). Such an inverse correlation with latitude (r=-0.78, p=0.01) is also found when Met allele frequencies in France are compared to those already published in five other European countries and in Turkey. We hypothesise that high Met 129 frequencies populations may be at higher risk for Creutzfeldt-Jakob disease.  相似文献   
9.
10.
BACKGROUND: Acne is a multifactorial disease exhibiting distinct clinical presentations. Among them, the catamenial type is a matter of concern for young women. Some oral contraceptives may help without, however, clearing the skin condition. AIM: The present open study aimed at evaluating the effect of overnight applications of a paste made of petrolatum,15% zinc oxide and 0.25% miconazole nitrate. METHOD: The split-face trial was conducted in 35 women. A non-medicated cream was used as control. Clinical evaluations and biometrological assessments on cyanoacrylate follicular biopsies were performed monthly for 3 months. Comedometry and the density in autofluorescent follicular casts were used as analytical parameters. In addition, the five most severe cases at inclusion were tested at the completion of the study for follicular bacterial viability using dual flow cytometry. RESULTS: Compared with baseline and to the control hemi-face, the medicated paste brought significant improvement of acne. The number of papules and their redness were reduced beginning with the first treatment phase. A reduction in the follicular fluorescence was yielded beginning with the second treatment phase. The ratios between injured and dead bacteria, on the one hand, and live bacteria, on the other hand were significantly increased at completion of the study. CONCLUSION: A miconazole paste applied for 1 week at the end of the ovarian cycle has a beneficial effect on catamenial acne.  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