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   3431篇
  免费   275篇
  国内免费   79篇
耳鼻咽喉   46篇
儿科学   55篇
妇产科学   35篇
基础医学   620篇
口腔科学   83篇
临床医学   200篇
内科学   541篇
皮肤病学   32篇
神经病学   287篇
特种医学   98篇
外科学   165篇
综合类   271篇
一般理论   2篇
预防医学   486篇
眼科学   20篇
药学   529篇
  1篇
中国医学   252篇
肿瘤学   62篇
  2024年   8篇
  2023年   41篇
  2022年   83篇
  2021年   119篇
  2020年   90篇
  2019年   111篇
  2018年   113篇
  2017年   120篇
  2016年   106篇
  2015年   96篇
  2014年   178篇
  2013年   298篇
  2012年   162篇
  2011年   147篇
  2010年   116篇
  2009年   169篇
  2008年   136篇
  2007年   131篇
  2006年   126篇
  2005年   102篇
  2004年   93篇
  2003年   109篇
  2002年   91篇
  2001年   65篇
  2000年   61篇
  1999年   45篇
  1998年   62篇
  1997年   55篇
  1996年   68篇
  1995年   70篇
  1994年   65篇
  1993年   54篇
  1992年   54篇
  1991年   57篇
  1990年   37篇
  1989年   30篇
  1988年   37篇
  1987年   32篇
  1986年   27篇
  1985年   36篇
  1984年   27篇
  1983年   20篇
  1982年   34篇
  1981年   16篇
  1980年   20篇
  1979年   19篇
  1978年   12篇
  1976年   11篇
  1975年   8篇
  1973年   5篇
排序方式: 共有3785条查询结果,搜索用时 15 毫秒
1.
In forensic medicine, although various alcohols have been reported as indicators of decomposition in collected blood, no studies have examined short-chain fatty acids as indicators. In this study, the blood n-butyric acid concentration was quantified, and the association between n-butyric acid and decomposition was investigated to determine whether the detection of n-butyric acid could be a new indicator of decomposition. Among the forensic autopsies performed from 2016 to 2018 in our laboratory, the cases were divided into decomposed (n = 20) and non-decomposed (n = 20) groups based on macroscopic findings. Blood samples collected at the time of autopsy were derivatized with 3-nitrophenylhydrazine hydrochloride after solid-phase extraction. The n-butyric acid concentration was measured using liquid chromatography–tandem mass spectrometry. In addition, ethanol and n-propanol were measured using a gas chromatography-flame ionization detector. There was a significant difference (p < 0.01) in the concentrations of n-butyric acid between the decomposed and non-decomposed groups (0.343 ± 0.259 [0.030–0.973] and 0.003 ± 0.002 [0.001–0.007] mg/mL, respectively). In the decomposed group, n-butyric acid was detected at high concentrations, even in cases where n-propanol was low. These results suggest that n-butyric acid is more likely to be an indicator of blood decomposition than n-propanol.  相似文献   
2.
The research and development of penicillin started with difficulty before 1949 and achieved certain results. In 1951, after the founding of the People's Republic of China, Zhang Weishen, as the only Chinese scientist who had been trained and worked in a penicillin research and development center in the United States for many years, overcame many difficulties and returned to China. In 1953, with the efforts of Zhang Weishen and his colleagues, China realized the industrialized production of penicillin, alleviating the urgent needs of the masses. Antibiotics has also become the first discipline to achieve major scientific and technological achievements after the founding of the New China. In the mid-1950s, the technical breakthrough in the localization of lactose substitutes marked the localization of the raw materials of the penicillin-producing culture medium, which paved the way for the industrialized production of penicillin with Chinese characteristics. Antibiotics have become one of the most widely used and affordable drugs for hundreds of millions of patients in China, and China has since ended the humiliating history of the “Sick Man of East Asia".  相似文献   
3.
《Vaccine》2019,37(47):6987-6995
Vero cells are nowadays widely used in the production of human vaccines. They are considered as one of the most productive and flexible continuous cell lines available for vaccine manufacturing. However, these cells are anchorage dependent, which greatly complicates upstream processing and process scale-up. Moreover, there is a recognized need to reduce the costs of vaccine manufacturing to develop vaccines that are affordable worldwide. The use of cell lines adapted to suspension growth contributes to reach this objective.The current work describes the adaptation of Vero cells to suspension culture in different serum free media according to multiple protocols based on subsequent passages. The best one that relies on cell adaption to IPT-AFM an in-house developed animal component free medium was then chosen for further studies. Besides, as aggregates have been observed, the improvement of IPT-AFM composition and mechanical dissociation were also investigated.In addition to IPT-AFM, three chemically defined media (CD293, Hycell CHO and CD-U5) and two serum free media (293SFMII and SFM4CHO) were tested to set up a serum free culture of the suspension-adapted Vero cells (VeroS) in shake flasks. Cell density levels higher than 2 × 106 cells/mL were obtained in the assessed conditions. The results were comparable to those obtained in spinner culture of adherent Vero cells grown on Cytodex 1 microcarriers.Cell infection with LP-2061 rabies virus strain at an MOI (Multiplicity of Infection) of 0.1 and a cell density of 8 ± 0.5 × 105 cells/mL resulted in a virus titer higher than 107 FFU/mL in all media tested. Nevertheless, the highest titer equal to 5.2 ± 0.5 × 107 FFU/mL, was achieved in IPT-AFM containing a reduced amount of Ca++ and Mg++. Our results demonstrate the suitability of the obtained VeroS cells to produce rabies virus at a high titer, and pave the way to develop VeroS cells bioreactor process for rabies vaccine production.  相似文献   
4.
5.
Introduction and objectivesThe Spanish Society of Cardiology/Spanish Heart Foundation (SEC/FEC) annually awards grants for cardiovascular research projects. Our objective was to analyze the trend in these investments and their resulting scientific production from 2007 to 2012.MethodsA search of the publications funded by the SEC/FEC was carried out, according to the following inclusion criteria: publication in a journal indexed in MEDLINE or EMBASE, publication date after the grant, authorship by the principal investigator of the grant, and acknowledgment of SEC/FEC funding. The impact factor and subsequent citations of the articles were analyzed (Web of Science).ResultsA total of 235 grants were awarded (39/y) with an allocation of €3 854 300 (€642 383/y), 37% of them to women. In all, 122 publications resulted from 88 research projects (37%) funded by the SEC/FEC. Up to October 2017, these publications had received 2258 citations in subsequent studies in the Web of Science, with a mean of 18.5 and a median of 8 citations/study.ConclusionsDespite the economic crisis, the mean number and size of the grants awarded by the SEC/FEC increased in the period analyzed. Grants were awarded on an equal opportunity basis to men and women. The bibliometric impact of the funded projects is acceptable, although efforts should be made to improve it.  相似文献   
6.
设计并试制了一种药用胶带纸层厚度在线检测系统.该系统将高精度电容传感器与计算机结合起来,同时配有丰富的外围器件,实现了多种实际生产中所需要的功能.它的出现,彻底解决了药用胶带纸胶层厚度在线检测这个难题,经过两年多的实际应用的检验,该系统实现了在线非接触测量,精度高,动态性能好,实现功能全面,价格合理,是药用胶带纸生产的必备检测仪器.由于该系统还可以很方便在纸张、塑料薄膜等其它生产线上进行推广,因而,其应用前景十分看好.  相似文献   
7.
This study was conducted to investigate the hypocholesterolemic effect of simvastatin (30 mg/kg BW) and antioxidant effect of coenzyme Q10 (CoQ10, 15 mg/kg BW) or green tea (5%) on erythrocyte Na leak, platelet aggregation and TBARS production in hypercholesterolemic rats treated with statin. Food efficiency ratio (FER, ADG/ADFI) was decreased in statin group and increased in green tea group, and the difference between these two groups was significant (p<0.05). Plasma total cholesterol was somewhat increased in all groups with statin compared with control. Plasma triglyceride was decreased in statin group and increased in groups of CoQ10 and green tea, and the difference between groups of statin and green tea was significant (p<0.05). Liver total cholesterol was not different between the control and statin group, but was significantly decreased in the group with green tea compared with other groups (p<0.05). Liver triglyceride was decreased in groups of statin and green tea compared with the control, and the difference between groups of the control and green tea was significant (p<0.05). Platelet aggregation of both the initial slope and the maximum was not significantly different, but the group with green tea tended to be higher in initial slope and lower in the maximum. Intracellular Na of group with green tea was significantly higher than the control or statin group (p<0.05). Na leak in intact cells was significantly decreased in the statin group compared with the control (p<0.05). Na leak in AAPH treated cells was also significantly reduced in the statin group compared with groups of the control and CoQ10 (p<0.05). TBARS production in platelet rich plasma was significantly decreased in the groups with CoQ10 and green tea compared with the control and statin groups (p<0.05). TBARS of liver was significantly decreased in the group with green tea compared with the statin group (p<0.05). In the present study, even a high dose of statin did not show a cholesterol lowering effect, therefore depletion of CoQ10 following statin treatment in rats is not clear. More clinical studies are needed for therapeutic use of CoQ10 as an antioxidant in prevention of degenerative diseases independent of statin therapy.  相似文献   
8.
 Because the immunomodulatory effects of antibiotics could possibly influence the degree of the systemic and local response to infection, knowledge of their intrinsic influence on the host's inflammatory response appears to be essential. Therefore, this study investigated the effects of frequently used antimicrobial agents (β-lactams, quinolones gentamicin, vancomycin and metronidazole) on the in-vitro tumor necrosis factor (TNF)-α and interleukin (IL)-6 production of isolated human peripheral blood mononuclear cells (PBMNC), cultured with or without endotoxin, in comparison with those effects obtained in a whole-blood assay system. In the presence of ciprofloxacin, ofloxacin, gentamicin, vancomycin, and metronidazole, a significant inhibition of the endotoxin-stimulated TNF-α production of human peripheral blood mononuclear cells (PBMNC) was found at therapeutic levels. Only ofloxacin showed a significant inhibitory influence on the endotoxin-induced IL-6 production of PBMNC. In the whole-blood assay, significant effects were not detectable. None of the antibiotics showed cytotoxicity. It is concluded that, at present, the direct immunological effects of antibiotics should be interpreted carefully with regard to the experimental conditions, and regardless of the therapeutic implications. To assess the potential direct immunomodulatory effect of antimicrobial agents, different cell culture procedures should be used. Received: October 19, 2001 / Accepted: February 15, 2002  相似文献   
9.
In this paper, we investigate the claim that although the same lexical units are involved in speech production and comprehension, there are separate input and output phoneme layers (Foygel and Dell, 2000). Data from a case series of aphasic patients are used to test this claim by examining the relationship between performance on a test of picture naming and performance on tests of phonological input. Estimates of each patient's semantic-lexical and phonological impairments in speech production were derived from Foygel and Dell's computational model of picture naming. It was found that the strength of the semantic-lexical impairments in speech production was significantly correlated with performance on auditory comprehension tests. This finding is consistent with the claim that the same lexical units are involved in speech comprehension and production. Conversely, the correlations between the strength of the phonological lesions in speech production and performance on tests of phonological input were non-significant, consistent with Foygel and Dell's claim that there are distinct input and output phoneme layers.  相似文献   
10.
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