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   8873篇
  免费   535篇
  国内免费   58篇
耳鼻咽喉   68篇
儿科学   190篇
妇产科学   145篇
基础医学   1169篇
口腔科学   179篇
临床医学   901篇
内科学   2108篇
皮肤病学   283篇
神经病学   766篇
特种医学   375篇
外科学   1316篇
综合类   15篇
一般理论   3篇
预防医学   707篇
眼科学   71篇
药学   579篇
中国医学   41篇
肿瘤学   550篇
  2024年   6篇
  2023年   40篇
  2022年   74篇
  2021年   178篇
  2020年   134篇
  2019年   234篇
  2018年   279篇
  2017年   159篇
  2016年   202篇
  2015年   228篇
  2014年   352篇
  2013年   493篇
  2012年   675篇
  2011年   730篇
  2010年   402篇
  2009年   360篇
  2008年   584篇
  2007年   681篇
  2006年   604篇
  2005年   590篇
  2004年   583篇
  2003年   509篇
  2002年   465篇
  2001年   72篇
  2000年   67篇
  1999年   79篇
  1998年   91篇
  1997年   74篇
  1996年   61篇
  1995年   50篇
  1994年   45篇
  1993年   43篇
  1992年   19篇
  1991年   43篇
  1990年   20篇
  1989年   21篇
  1988年   22篇
  1987年   16篇
  1986年   27篇
  1985年   35篇
  1984年   19篇
  1983年   18篇
  1982年   14篇
  1981年   12篇
  1980年   6篇
  1979年   10篇
  1977年   6篇
  1975年   4篇
  1974年   4篇
  1972年   4篇
排序方式: 共有9466条查询结果,搜索用时 15 毫秒
31.
32.
33.
The role of tumour suppressor genes in the development of human cancers has been studied extensively. In viral carcinogenesis, the inactivation of suppressor proteins such as retinoblastoma (pRb) and p53, and cellular oncogenes overexpression, such as c-myc, has been the subject of a number of investigations. In uterine-cervix carcinomas, where high-risk human papillomavirus (HPV) plays an important role, pRb and p53 are inactivated by E7 and E6 viral oncoproteins, respectively. However, little is known about the in situ expression of some of these proteins in pre-malignant and malignant cervical tissues. On the other hand, it has also been demonstrated that c-myc is involved in cervical carcinogenesis, and that pRb participates in the control of c-myc gene expression. By using immunostaining techniques, we investigated pRb immunodetection pattern in normal tissues, squamous intraepithelial lesions (SILs) and invasive carcinomas from the uterine cervix. Our data show low pRb detection in both normal cervical tissue and invasive lesions, but a higher expression in SILs. C-Myc protein was observed in most of the cellular nuclei of the invasive lesions, while in SILs was low. These findings indicate a heterogeneous pRb immunostaining during the different stages of cervical carcinogenesis, and suggest that this staining pattern could be a common feature implicated in the pathogenesis of uterine-cervix carcinoma.  相似文献   
34.
Luc L 《Obesity surgery》1993,3(2):179-180
During the past 7 years, 170 morbidly obese patients have been subjected to a biliopancreatic diversion. Mean weight loss achieved over 2 years was greater than 70% of excess weight and was maintained. Early complications were rare. The most common side-effects are discussed. The re-operation rate because of these side-effects was 7%. Eating normal meals, together with a stable weight loss, has provided these patients with a better quality of life.  相似文献   
35.
电解可脱性铂弹簧圈栓塞治疗颅内动脉瘤26例   总被引:2,自引:0,他引:2  
目的:报告使用电解可脱性钱弹簧圈(Guglielmi detachable coil,GDC)栓塞治疗颅内动脉瘤的情况。方法:气管内插管全订和肝素抗凝下,使用Seldinger’s技术,经Tracker微导管放置GDC栓塞颅内动脉瘤。成功栓塞26例31个颅内动脉瘤,其中27个为100%栓塞,3个为95%,1个为90%。3个95%栓塞均为宽颈动脉瘤。1个90%栓塞者,为Hunt分级Ⅳ级,存在严重脑血  相似文献   
36.
In a rat model, the left kidney was subjected to 60 min of normothermic ischemia followed by 15 min of reperfusion, whereas the right kidney, serving as a paired control, was not rendered ischemic. Both kidneys were then perfused in situ with either Euro-Collins (EC) solution (n=12) or University of Wisconsin (UW) solution (n=6) for 10 min. Each kidney was then harvested and stored at 4°C in its respective solution. After 24 and 48 h of cold storage, the following vasoactive substances were measured in the preservation media: endothelin (ET), angiotensin II (A-II), thromboxane (B2) (TxB2), and prostaglandin I2 (PGI2). After 24 h in EC solution, left kidneys uniformly produced significantly higher concentrations of each vasoactive substance than right kidneys: ET 1.64±0.3 pg/ml vs 0.82±0.1 pg/ml (P0.009); A-II 20.8±6.2 pg/ml vs 7.75+2.3 pg/ml (P0.007); TxB2 100.8±17.7 pg/ml vs 40.1±11.7 pg/ml (P0.04); PGI2 638.3±41.1 pg/ml vs 318.3±36.4 pg/ml (P0.001), respectively. At 48 h, a similar pattern of results was obtained as the kidney continued to produce TxB2 and prostacyclins during the 24–48 h period. In the UW solution, basal levels of ET and A-II were lower than those in EC solution, but similarly increased after initial ischemia. At 24 h, the concentrations produced by the left and right kidneys were as follows: ET 0.66±0.1 pg/ml vs 0.48±0.1 pg/ml (P0.14); A-II 10.36±3.7 pg/ml vs 2.14±0.7 pg/ml (P0.006); TxB2 178±53 pg/ml vs 52±23.1 pg/ml (P0.001); and PGI2 448.3±49 pg/ml vs 323±44.3 pg/ml (P0.01), respectively. After 48 h, the range of concentrations of each substance was similar to that obtained after 24 h. In further studies, the concentrations of ET and A-II were measured in solution previously used to preserve human kidneys (n=7). The mean concentration of ET and A-II in these samples was 3.82±1.14 pg/ml and 21.3±9.2 pg/ml, respectively, whereas in control media both substances were below the limits of detection. These results demonstrate that vasoconstrictive substances can be measured in the preservation media after a kidney has been stored cold and that higher concentrations are found when the organ has been subjected to prior normothermic ischemia. The measurement of these vasoactive substances before transplantation may reveal that the kidney has been subjected to previous ischemic events. Moreover, these vasoactive substances could be involved in the early recovery of renal function after kidney transplantation.  相似文献   
37.
We have used a quantitative immunoblotting technique to analyze the repertoires of self-reactive antibodies in serum samples obtained from the same five healthy adults over a 25-year interval. The average age of the donors was 43 years at the time of the first serum sample and 69 years at the time of the second serum sample. The antibody repertoires of IgM and IgG were found to be strikingly similar among individuals in both early and late samples. Densitometric profiles of self-reactivity of serum IgM and of purified serum IgG remained unchanged over the 25-year interval. The total reactivity of serum IgG decreased significantly over the 25-year period. The observed stability of the natural self-reactive IgM and IgG antibody repertoires with aging supports the view that autoreactive B cells in the normal immune system are positively selected for reactivity with a limited set of immuno-dominant self-antigens throughout life.  相似文献   
38.
The effect of suppository bases on rabbit rectal mucosa was investigated using six triglyceride bases, polyethylene glycol, and a triglyceride base combined with monoglycerides or fatty acids and methyl esters of those acids. Rectal irritation was evaluated and scored according to defined pathological features. Pure triglycerides and a triglyceride to which a nonionic surfactant was added caused severe mucosal damage with ulceration and inflammation. Hyperemia was characteristic for irritation by polyethylene glycol suppositories. Mucosal damage by a pure triglyceride combined with monoglycerides or fatty acids and methyl esters of those acids was similar but statistically less pronounced than with all other bases.  相似文献   
39.
Summary The turnover of noradrenaline (NA) and dopamine (DA) was estimated in various rat brain regions by measuring the depletion of the amines after inhibition of their biosynthesis by -methyltyrosine. Acute treatment with clonidine (0.1 mg/kg) reduced NA turnover in the brain stem, hypothalamus and rest of the brain but had no effect on DA turnover in the corpus striatum and rest of the brain. After chronic clonidine treatment (0.1 mg/kg, twice daily for 15 days), NA turnover was not affected by an additional injection of clonidine in the brain stem or in the hypothalamus but was still markedly reduced in the rest of the brain. In addition, DA turnover was reduced in the corpus striatum and rest of the brain, an effect which was also observed after a single injection of a high dose of clonidine (1 mg/kg). These findings suggest that a chronic administration of clonidine may cause regionally differential changes in the sensitivity of central NA receptors.  相似文献   
40.
BACKGROUND AND PURPOSE: To compare intensity-modulated treatment plans of patients with head and neck cancer generated by forward and inverse planning. MATERIALS AND METHODS: Ten intensity-modulated treatment plans, planned and treated with a step&shoot technique using a forward planning approach, were retrospectively re-planned with an inverse planning algorithm. For this purpose, two strategies were applied. First, inverse planning was performed with the same beam directions as forward planning. In addition, nine equidistant, coplanar incidences were used. The main objective of the optimisation process was the sparing of the parotid glands beside an adequate treatment of the planning target volume (PTV). Inverse planning was performed both with pencil beam and Monte Carlo dose computation to investigate the influence of dose computation on the result of the optimisation. RESULTS: In most cases, both inverse planning strategies managed to improve the treatment plans distinctly due to a better target coverage, a better sparing of the parotid glands or both. A reduction of the mean dose by 3-11Gy for at least one of the parotid glands could be achieved for most of the patients. For three patients, inverse planning allowed to spare a parotid gland that had to be sacrificed by forward planning. Inverse planning increased the number of segments compared to forward planning by a factor of about 3; from 9-15 to 27-46. No significant differences for PTV and parotid glands between both inverse planning approaches were found. Also, the use of Monte Carlo instead of pencil beam dose computation did not influence the results significantly. CONCLUSION: The results demonstrate the potential of inverse planning to improve intensity-modulated treatment plans for head and neck cases compared to forward planning while retaining clinical utility in terms of treatment time and quality assurance.  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