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   2836篇
  免费   148篇
  2984篇
  2023年   13篇
  2022年   35篇
  2021年   70篇
  2020年   48篇
  2019年   45篇
  2018年   65篇
  2017年   61篇
  2016年   71篇
  2015年   74篇
  2014年   120篇
  2013年   155篇
  2012年   213篇
  2011年   181篇
  2010年   118篇
  2009年   108篇
  2008年   144篇
  2007年   138篇
  2006年   106篇
  2005年   104篇
  2004年   93篇
  2003年   78篇
  2002年   89篇
  2001年   74篇
  2000年   78篇
  1999年   54篇
  1998年   20篇
  1997年   16篇
  1996年   33篇
  1995年   18篇
  1994年   18篇
  1993年   18篇
  1992年   50篇
  1991年   33篇
  1990年   26篇
  1989年   33篇
  1988年   28篇
  1987年   29篇
  1986年   19篇
  1985年   32篇
  1984年   25篇
  1982年   15篇
  1981年   18篇
  1980年   22篇
  1979年   26篇
  1978年   28篇
  1977年   18篇
  1975年   12篇
  1974年   13篇
  1973年   17篇
  1972年   13篇
排序方式: 共有2984条查询结果,搜索用时 15 毫秒
91.
AimsThe aim of the present investigation was to develop a nanoemulsion (NE) gel formulation for the transdermal delivery of meloxicam (MLX) in order to ensure maximum controlled and sustained drug release capacity.Main methodsThe MLX containing NE gel was prepared and characterized for particle size, zeta potential, pH, rheology, in vitro drug release, in vitro skin permeation, and in vitro hemolysis. Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) of MLX-NE gel treated rat skin was performed to investigate the skin permeation mechanism of meloxicam from NE gel. Skin permeation potential of the developed gel formulation was assessed using confocal laser scanning microscopy (CLSM). The in vivo toxicity of MLX-NE gel was assessed by histopathological examination in rat. The rat paw edema test was performed to evaluate the anti-inflammatory activity of MLX-NE gel.Key findingsPercutaneous absorption studies demonstrated a higher permeation of meloxicam from NE gel, than the drug solution. FTIR and DSC studies supported stratum corneum lipid extraction as a possible penetration enhancer mechanism for MLX-NE gel. CLSM studies confirmed the permeation of the NE gel formulation to the deeper layers of the skin (up to 130 μm). MLX-NE gel turned out to be non-irritant, biocompatible, and provided maximum inhibition of paw edema in rats over 24 h in contrast to MLX solution.SignificanceThe nanoemulsion gel formulation may hold promise as an effective alternative for the transdermal delivery of meloxicam.  相似文献   
92.
Summary Ethanol production from the inulin of Jerusalem artichoke byZ. mobilis was studied in batch and continuous fermentations. Both acid or enzymatic hydrolysis were used. In continuous cultures enzymatic hydrolysis showed better results. Ethanol productivities of 17.7 and 29.0 g/l.h were obtained at output concentrationsca 35 g/l (% of conversion 99 and 83; ethanol yield 0.45 g/g). The hydrolysed juice could be used without any nutrient addition.  相似文献   
93.
Immobilized growing cells of Zymomonas mobilis were found to ferment rapidly and efficiently media containing 100 g/L fructose in a continuous reactor. A volumetric ethanol productivity of 94.8 g/L h was achieved at a substrate conversion of 75.5%. With 97% conversion of substrate the productivity was 28.4 g/L h. At fructose concentrations of 150 and 200 g/L substrate and product inhibitions limited the performance of the reactor. Ethanol production was constant over a period of 55 days.  相似文献   
94.
Expansion of CTG/CAG trinucleotide repeats has been shown to cause a number of autosomal dominant cerebellar ataxias (ADCA) such as SCA1, SCA2, SCA3/ MJD, SCA6, SCA7, SCA8 and DRPLA. There is a wide variation in the clinical phenotype and prevalence of these ataxias in different populations. An analysis of ataxias in 42 Indian families indicates that SCA2 is the most frequent amongst all the ADCAs we have studied. In the SCA2 families, together with an intergenerational increase in repeat size, a horizontal increase with the birth order of the offspring was also observed, indicating an important role for parental age in repeat instability. This was strengthened by the detection of a pair of dizygotic twins with expanded alleles showing the same repeat number. Haplotype analysis indicates the presence of a common founder chromosome for the expanded allele in the Indian population. Polymorphism of CAG repeats in 135 normal individuals at the SCA loci studied showed similarity to the Caucasian population but was significantly different from the Japanese population.  相似文献   
95.
Chronic hepatitis is a major cause of liver cancer, so earlier treatment of hepatitis might be reducing liver cancer incidence. Hepatitis can be induced in mice by treatment with Concanavalin A (Con A); the resulting liver injury causes significant CD4+ T cell activation and infiltration. In these T cells, Roquin, a ring-type E3 ubiquitin ligase, is activated. To investigate the role of Roquin, we examined Con A-induced liver injury and T cell infiltration in transgenic (Tg) mice overexpressing Roquin specifically in T cells. In Roquin Tg mice, Con A treatment caused greater increases in both the levels of liver injury enzymes and liver tissue apoptosis, as revealed by TUNEL and H&E staining, than wild type (WT) mice. Further, Roquin Tg mice respond to Con A treatment with greater increases in the T cell population, particularly Th17 cells, though Treg cell counts are lower. Roquin overexpression also enhances increases in pro-inflammatory cytokines, including IFN-γ, TNF-α and IL-6, upon liver injury. Furthermore, Roquin regulates the immune response and apoptosis in Con A induced hepatitis via STATs, Bax and Bcl2. These findings suggest that over-expression of Roquin exacerbates T-cell mediated hepatitis.  相似文献   
96.
97.
Genetic relationships among Indian aromatic and quality rice (Oryza sativa) germplasm were assessed using 30 fluorescently labeled rice microsatellite markers. The 69 rice genotypes used in this study included 52 Basmati and other scented/quality rice varieties from different parts of India and 17 indica and japonica varieties that served as controls. A total of 235 alleles were detected at the 30 simple sequence repeat (SSR) loci, 62 (26.4%) of which were present only in Basmati and other scented/quality rice germplasm accessions. The number of alleles per locus ranged from 3 to 22, with an average of 7.8, polymorphism information content (PIC) values ranged from 0.2 to 0.9, with an average of 0.6, and the size range between the smallest and the largest allele for a given microsatellite locus varied between 3 bp and 68 bp. Of the 30 SSR markers, 20 could distinguish traditional Basmati rice varieties, and a single panel of eight markers could be used to differentiate the premium traditional Basmati, cross-bred Basmati, and non-Basmati rice varieties having different commercial value in the marketplace. When estimates of inferred ancestry or similarity coefficients were used to cluster varieties, the high-quality Indian aromatic and quality rice genotypes could be distinguished from both indica and japonica cultivars, and crossbred varieties could be distinguished from traditional Basmati rices. The results indicate that Indian aromatic and quality germplasm is genetically distinct from other groups within O. sativa and is the product of a long, independent pattern of evolution. The data also suggest that there is scope for exploiting the genetic diversity of aromatic/quality rice germplasm available in India for national Basmati rice breeding programs.Electronic Supplementary Material Supplementary material is available for this article at .  相似文献   
98.
Low productivity of pilosae type lentils grown in South Asia is attributed to narrow genetic base of the released cultivars which results in susceptibility to biotic and abiotic stresses. For enhancement of productivity and production, broadening of genetic base is essentially required. The genetic base of released cultivars can be broadened by using diverse types including bold seeded and early maturing lentils from Mediterranean region and related wild species. Genetic diversity in eighty six accessions of three species of genus Lens was assessed based on twelve genomic and thirty one EST-SSR markers. The evaluated set of genotypes included diverse lentil varieties and advanced breeding lines from Indian programme, two early maturing ICARDA lines and five related wild subspecies/species endemic to the Mediterranean region. Genomic SSRs exhibited higher polymorphism in comparison to EST SSRs. GLLC 598 produced 5 alleles with highest gene diversity value of 0.80. Among the studied subspecies/species 43 SSRs detected maximum number of alleles in L. orientalis. Based on Nei’s genetic distance cultivated lentil L. culinaris subsp. culinaris was found to be close to its wild progenitor L. culinaris subsp. orientalis. The Prichard’s structure of 86 genotypes distinguished different subspecies/species. Higher variability was recorded among individuals within population than among populations.  相似文献   
99.
In situ gel-forming systems have drawn much attention of current researchers to overcome the poor bioavailability from the conventional eye drops. The present work described formulation and pharmacoscintigraphic evaluation of timolol-maleate-loaded chitosan/hydroxy propyl methyl cellulose (HPMC)-based polymer matrix for enhanced ocular retention. Chitosan and HPMC ratio was optimized and formulation was characterized for various in vitro parameters. The ocular retention was studied on New Zealand rabbits by gamma scintigraphy, which is a very simple and noninvasive technique. For scintigraphy study, the drug timolol maleate was radiolabeled 99mTc by direct labeling method using SnCl2·2H2O as reducing agent. The labeling procedure was optimized to get maximum labeling efficiency (>98%). In vitro stability of the radiolabeled drug (99mTc-timolol maleate complex) was checked and it was found to be stable for up to 24 h. Plain drug eliminates rapidly as significant activity was recorded in kidney and bladder after 2 h of ocular administration. It was evident from the scintigraphic images and the time–activity curve plotted from the data that the plain drug solution cleared very rapidly from the corneal region and reached into systemic circulation via nasolachrymal drainage system, as significant activity was recorded in kidney and bladder after 2 h of ocular administration. Developed formulation cleared at a slow rate and remained at corneal surface for longer time duration. No radioactivity was observed in systemic circulation after 2 h. Ocular irritation of the developed formulation was also checked by hen’s egg chorioallantoic membrane test and formulation was found to be practically nonirritant. The study signified the potential of gamma scintigraphy in evaluation of novel drug delivery systems in a noninvasive manner.  相似文献   
100.
The National Cancer Institute (NCI) Cancer Imaging Program organized two related workshops on June 26–27, 2013, entitled “Correlating Imaging Phenotypes with Genomics Signatures Research” and “Scalable Computational Resources as Required for Imaging-Genomics Decision Support Systems.” The first workshop focused on clinical and scientific requirements, exploring our knowledge of phenotypic characteristics of cancer biological properties to determine whether the field is sufficiently advanced to correlate with imaging phenotypes that underpin genomics and clinical outcomes, and exploring new scientific methods to extract phenotypic features from medical images and relate them to genomics analyses. The second workshop focused on computational methods that explore informatics and computational requirements to extract phenotypic features from medical images and relate them to genomics analyses and improve the accessibility and speed of dissemination of existing NIH resources. These workshops linked clinical and scientific requirements of currently known phenotypic and genotypic cancer biology characteristics with imaging phenotypes that underpin genomics and clinical outcomes. The group generated a set of recommendations to NCI leadership and the research community that encourage and support development of the emerging radiogenomics research field to address short-and longer-term goals in cancer research.  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