全文获取类型
收费全文 | 3263篇 |
免费 | 186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 31 毫秒
91.
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
92.
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
93.
Huyen Tran Tim Brighton Andrew Grigg Simon McRae Joanna Dixon Daniel Thurley Maher K. Gandhi Matt Truman Paula Marlton John Catalano 《British journal of haematology》2014,167(2):243-251
The efficacy of a fixed‐dose rituximab schedule was prospectively explored in primary/acute refractory, relapsed or chronic (platelet count >10 × 109/l and ≤50 × 109/l) idiopathic thrombocytopenic purpura (ITP). Patients received two doses of rituximab (1000 mg) on days 1 and 15 and were followed‐up on weeks 1–8, 12, 26, 39 and 52. A total of 122 patients were included in the safety population; efficacy was analysed in 108 patients. Overall response rate (ORR) at week 8, defined as the proportion of patients achieving complete response (CR; platelet count >150 × 109/l) or partial response (PR; platelet count >50 × 109/l) was 44%. Therapeutic response, defined as achieving a response at week 8, with at least a minor response (MR; platelet count >30 × 109/l), sustained up to weeks 26 and 52 and accompanied by a reduction in ITP medications, was achieved in 44% (week 26) and 35% (week 52) of patients, respectively. Treatment was well tolerated with no safety concerns. While this study failed to meet its primary endpoint of an ORR of 50%, the efficacy of two fixed doses of rituximab appear to provide similar efficacy to the standard 375 mg/m2 four‐dose schedule in relapsed/chronic ITP. 相似文献
94.
95.
96.
97.
Lieber SB Redberg RF Blumenthal RS Gandhi A Robb KJ Mora S 《The American journal of cardiology》2012,109(12):1754-1760
Increased physical activity (PA) is associated with improvement of cardiac risk factors and prevention of cardiovascular disease, yet many women remain sedentary. With rising Internet use, Web-based interventions provide an alternative to improve PA, but their effectiveness for change in PA and quality of life (QOL) in a real-world setting is unknown. Participants were United States women ≥18 years old who received 12 weekly PA modules and completed surveys on PA, QOL, and readiness for PA at registration (registration cohort, n = 3,796) or registration and 12 weeks (evaluation cohort, n = 892). QOL was assessed with a modified Short Form-36 with subscores for energy and well-being. Participants showed significant (p <0.001) favorable changes in PA (baseline, median 240 kcal/week, interquartile range 62 to 667; 12 weeks, 343 kcal/week, 131 to 828), stage of readiness for PA, and body mass index (baseline, 29.3 kg/m(2), 24.9 to 34.7; 12 weeks, 28.9 kg/m(2), 24.6 to 34.2). Significant improvements (p <0.0001) were also found in composite scores for energy and well-being. Compliance with PA guideline recommendations increased from 15.8% to 21.4%. Program weeks completed (p = 0.03), energy (p = 0.04), and well-being (p = 0.002) were significantly associated with achieving guideline compliance. In women reporting no PA at baseline (n = 88), program participation resulted in 54.6% achieving some PA and another 9.1% achieving total compliance with recommendations. In conclusion, in this national cohort of women, a 12-week Web-based intervention improved PA and QOL measurements, resulting in higher short-term PA guideline compliance and better QOL. Increasing use of this simple Web-based tool could improve PA and promote disease prevention. 相似文献
98.
Murine embryonic stem cells (mESCs) have the potential to differentiate into almost any type of cell, and hence, represent a useful biological resource for tissue engineering. The differentiation of mESCs into osteoblasts in vitro is usually dampened by simultaneous differentiation of adipocytes. Insulin exerts a profound effect on bone development through increased differentiation of osteoblasts and concurrent formation of adipocytes. Comparatively, Sirt1, which plays a crucial role in osteoblast differentiation, has been reported to down regulate adipocyte formation during osteoblast differentiation. This study analyzed the combined effects of insulin and Sirt1 on the differentiation of osteoblasts. Osteoblast differentiation was quantified by estimating the accumulation of mineralized matrix and expression of osteogenic genes. The present data show that the simultaneous action of the insulin and Sirt1-mediated pathways increased the efficiency of osteoblast differentiation. When the cells were tested for ALP activity and Alizarin red staining, there was a respective increase of ~180% and ~166% (P<0.05) compared to the control. Furthermore, the mRNA expression patterns of osteoprotegerin, osterix, runx2, and osteopontin were increased by 3.6, 2.3, 1.8, and 1.7-fold, respectively, with a concomitant decrease in the mRNA expression levels of adipocyte marker genes. Interestingly, blocking the effects of both Sirt1 and insulin resulted in decreased osteoblastogenesis (60%) and subsequent increased adipocyte differentiation (195%) (P<0.05). Moreover, immunoblotting analysis demonstrated that this activation was via an Akt-dependent pathway. In conclusion, the present data suggests an enhanced process of osteoblast differentiation that can be exploited further to improve mESC differentiation. 相似文献
99.
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
100.
Nolan B. Skop Frances Calderon Steven W. Levison Chirag D. Gandhi Cheul H. Cho 《Acta biomaterialia》2013,9(6):6834-6843
An effective paradigm for transplanting large numbers of neural stem cells after central nervous system (CNS) injury has yet to be established. Biomaterial scaffolds have shown promise in cell transplantation and in regenerative medicine, but improved scaffolds are needed. In this study we designed and optimized multifunctional and biocompatible chitosan-based films and microspheres for the delivery of neural stem cells and growth factors for CNS injuries. The chitosan microspheres were fabricated by coaxial airflow techniques, with the sphere size controlled by varying the syringe needle gauge and the airflow rate. When applying a coaxial airflow at 30 standard cubic feet per hour, ~300 μm diameter spheres were reproducibly generated that were physically stable yet susceptible to enzymatic degradation. Heparin was covalently crosslinked to the chitosan scaffolds using genipin, which bound fibroblast growth factor-2 (FGF-2) with high affinity while retaining its biological activity. At 1 μg ml?1 approximately 80% of the FGF-2 bound to the scaffold. A neural stem cell line, GFP + RG3.6 derived from embryonic rat cortex, was used to evaluate cytocompatibility, attachment and survival on the crosslinked chitosan–heparin complex surfaces. The MTT assay and microscopic analysis revealed that the scaffold containing tethered FGF-2 was superior in sustaining survival and growth of neural stem cells compared to standard culture conditions. Altogether, our results demonstrate that this multifunctional scaffold possesses good cytocompatibility and can be used as a growth factor delivery vehicle while supporting neural stem cell attachment and survival. 相似文献