全文获取类型
收费全文 | 3268篇 |
免费 | 181篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 130篇 |
妇产科学 | 75篇 |
基础医学 | 398篇 |
口腔科学 | 49篇 |
临床医学 | 297篇 |
内科学 | 715篇 |
皮肤病学 | 54篇 |
神经病学 | 175篇 |
特种医学 | 111篇 |
外科学 | 479篇 |
综合类 | 59篇 |
一般理论 | 3篇 |
预防医学 | 173篇 |
眼科学 | 106篇 |
药学 | 331篇 |
中国医学 | 8篇 |
肿瘤学 | 281篇 |
出版年
2023年 | 29篇 |
2022年 | 71篇 |
2021年 | 161篇 |
2020年 | 63篇 |
2019年 | 89篇 |
2018年 | 111篇 |
2017年 | 78篇 |
2016年 | 81篇 |
2015年 | 88篇 |
2014年 | 138篇 |
2013年 | 159篇 |
2012年 | 276篇 |
2011年 | 289篇 |
2010年 | 159篇 |
2009年 | 138篇 |
2008年 | 188篇 |
2007年 | 182篇 |
2006年 | 143篇 |
2005年 | 126篇 |
2004年 | 127篇 |
2003年 | 124篇 |
2002年 | 80篇 |
2001年 | 52篇 |
2000年 | 54篇 |
1999年 | 47篇 |
1998年 | 29篇 |
1997年 | 19篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 7篇 |
1992年 | 19篇 |
1991年 | 23篇 |
1990年 | 25篇 |
1989年 | 20篇 |
1988年 | 20篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1979年 | 15篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1972年 | 6篇 |
1971年 | 11篇 |
1970年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有3460条查询结果,搜索用时 15 毫秒
51.
Kalaimaran Francina Cecilia Ramalingam Ravindhran Munusamy Rajiv Gandhi Appadurai Daniel Reegan Kedike Balakrishna Savarimuthu Ignacimuthu 《Parasitology research》2014,113(9):3477-3484
The mosquitocidal activity of different fractions and isolated compounds from the ethyl acetate extract of Ecbolium viride root was assessed on larvae and pupae of Culex quinquefasciatus Say (Diptera: Culicidae). The larvae and pupae were exposed to concentrations of 6.125, 12.5, 25 and 50 ppm for fractions and 1, 2.5, 5 and 10 ppm for compound. Among the 12 fractions screened, fraction 6 from the ethyl acetate extract of E. viride was recorded to have the highest larvicidal and pupicidal activities against C. quinquefasciatus. The lethal concentration (LC50 and LC90) values of fraction 6 were 4.26 and 9.0 ppm against C. quinquefasciatus larvae and 6.55 and 12.19 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Fraction 7 was recorded to have moderate activity with LC50 and LC90 values of 11.25 and 25.02 ppm against C. quinquefasciatus larvae and 13.33 and 31.15 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Ecbolin A and ecbolin B were identified from fractions 7 and 6, respectively. The structure of the isolated compounds was identified on the basis of spectral data (1H NMR and 13C NMR) and compared with literature spectral data. Further, the isolated compound, ecbolin B, from fraction 6 was recorded to have strong larvicidal and pupicidal activities than ecbolin A. The LC50 and LC90 values of ecbolin B on C. quinquefasciatus larvae were 1.36 and 2.76 ppm, and on pupae, these were 1.54 and 3.51 ppm, respectively. The present results suggest that ecbolin B could be used as a mosquitocidal agent against C. quinquefasciatus. 相似文献
52.
Thanks to the advent of the random laser, new light applications have opened up, ranging from biophotonic to security devices. Here, by using the well-known but unexplored light-harvesting bio-pigment of butterfly pea (Clitoria ternatea, CT) flower extract, generation of continuous-wave (CW) random lasing at ∼660 nm has been demonstrated. Furthermore, a wavelength tunability of ∼30 nm in the lasing emission was obtained by utilizing the resonance energy transfer (RET) mechanism in a gain medium with a binary mixture of CT extract and a commercially available methylene blue (MB) dye as the gain medium. In the CT extract–dye mixture, the bio-pigments are acting as donors and the MB dye molecules are acting as acceptors. Amplification in intensity of the lasing emission of this binary system has further been achieved in the presence of optimized concentrations of metal (Ag)–semiconductor (ZnO) scattering nanoparticles. Interestingly, the lasing threshold has been reduced from 128 to 25 W cm−2, with a narrowed emission peak just after loading of the Ag nanoplasmon in the ZnO-doped binary gain medium. Thanks to the strong localized electric field in the metal nanoplasmon, and the multiple scattering effects of ZnO, the lasing threshold was reduced by approximately four times compared to that of the gain medium without the use of scatterers. Thus, we believe that our findings on wavelength-tunable, non-toxic, biocompatible random lasing will open up new applications, including the design of low-cost biophotonic devices.Tuning of the lasing emission from a bio-pigment using the resonance energy transfer process, with the help of a semiconductor and plasmonic scatterer. 相似文献
53.
54.
55.
56.
Jones K Nourse JP Keane C Crooks P Gottlieb D Ritchie DS Gill D Gandhi MK 《American journal of hematology》2012,87(3):258-265
Recently, nontumor specific circulating DNA was shown to be elevated in a broad range of lymphomas, implicating a role as a potential biomarker. Epstein-Barr virus' (EBV) presence within a proportion of lymphomas implies EBV-DNA has potential as a lymphoma-specific disease response biomarker. However, application would be restricted to EBV-associated lymphomas. Neither detailed comparison has been performed of lymphoma-specific versus nonspecific DNA as disease response biomarkers nor have the kinetics of circulating DNA during treatment been established, and the optimal methodology remains unknown. We prospectively evaluated DNA levels and clinical response of 63 lymphoma patients. DNA was measured in paired serum, plasma, and cell samples at five predetermined time-points taken prior, during and following treatment. Both cell-free (c-f) circulating EBV-DNA (in EBV-associated lymphoma) and nonspecific c-f DNA levels (in all lymphomas) were elevated and discriminatory at presentation compared to healthy controls. Nonspecific c-f DNA was significantly associated with baseline serum lactate dehydrogenase. Within EBV-associated lymphomas at presentation, there was a strong correlation between specific and nonspecific circulating c-f DNA (r = 0.9, P < 0.0001). However, only c-f EBV-DNA correlated with clinical/radiological response. In addition, c-f EBV-DNA, and not nonspecific c-f DNA, provided an early marker of relapsed and refractory disease. Serum versus plasma, and single versus multiple-copy EBV-gene targets were equivalent. Lymphoma-specific DNA is a disease response biomarker; however, nonspecific DNA reflected neither lymphoma-specific DNA nor therapeutic response. Lymphoma disease response can be monitored by blood tests, but new lymphoma-specific biomarkers need to be identified to broaden applicability. 相似文献
57.
58.
59.