全文获取类型
收费全文 | 102974篇 |
免费 | 1060篇 |
国内免费 | 882篇 |
专业分类
104916篇 |
出版年
2021年 | 99篇 |
2020年 | 43篇 |
2019年 | 79篇 |
2018年 | 11907篇 |
2017年 | 10754篇 |
2016年 | 7576篇 |
2015年 | 812篇 |
2014年 | 588篇 |
2013年 | 833篇 |
2012年 | 4607篇 |
2011年 | 13230篇 |
2010年 | 12248篇 |
2009年 | 8480篇 |
2008年 | 10224篇 |
2007年 | 11834篇 |
2006年 | 696篇 |
2005年 | 984篇 |
2004年 | 1430篇 |
2003年 | 1485篇 |
2002年 | 1154篇 |
2001年 | 642篇 |
2000年 | 560篇 |
1999年 | 362篇 |
1998年 | 124篇 |
1997年 | 153篇 |
1996年 | 126篇 |
1995年 | 120篇 |
1994年 | 106篇 |
1993年 | 132篇 |
1992年 | 268篇 |
1991年 | 264篇 |
1990年 | 255篇 |
1989年 | 212篇 |
1988年 | 203篇 |
1987年 | 193篇 |
1986年 | 153篇 |
1985年 | 149篇 |
1984年 | 136篇 |
1983年 | 136篇 |
1982年 | 94篇 |
1981年 | 71篇 |
1980年 | 66篇 |
1979年 | 90篇 |
1978年 | 87篇 |
1977年 | 71篇 |
1976年 | 47篇 |
1975年 | 44篇 |
1974年 | 50篇 |
1972年 | 294篇 |
1971年 | 302篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
961.
Amelia K. Sofjan Rachel J. Musgrove Kevin W. Garey 《Current fungal infection reports》2016,10(2):68-77
Background
Invasive candidiasis (IC) including candidemia and deep-seated candidiasis is associated with up to 50 % overall mortality and up to $80,000 in attributable cost (2015 US$). Rapid diagnostic tests (RDTs) for Candida have been developed. However, whether RDTs along with real-time decision support translate to better attainment of stewardship goals—improve clinical outcomes, minimize unintended consequences of antifungal use, and reduce healthcare costs—is unknown. The purpose of this systematic review was to provide an up-to-date review of recently published studies that have assessed how RDTs for IC impact attainment of these goals.Methods
Three electronic bibliographic databases were searched using a pre-defined search strategy evaluating the impact of RDTs for IC on attainment of antifungal stewardship goals. Quality assessments were performed by two reviewers using established study methodology metrics.Results and Conclusions
Eight studies were identified of which five had sufficient information to be included in the review. Despite the limitations of the various studies and the different methodologies employed, the studies all produced similar conclusions. Compared to conventional methods and baseline stewardship activities, the integration of RDTs for IC and real-time decision support, mainly through antifungal stewardship, was associated with decreased mortality, more optimal use of antifungals, and reduced healthcare costs. However, larger clinical studies are needed to confirm these trends.962.
Onychomycosis is a common and difficult to treat infection, owing predominately to the limited penetration of topical drugs to the site of infection. Systemic drugs are not an option for all patients due to adverse events and drug-drug interactions. In this article, we review the nail penetration and clinical efficacy data of topical drugs, including older agents such as ciclopirox and amorolfine, as well as the newer agents, efinaconazole and tavaborole. Additionally, we describe some unresolved questions in the management of onychomycosis. 相似文献
963.
Peter J. H. Hulshof Martijn R. K. Mes Richard J. Boucherie Erwin W. Hans 《Flexible Services and Manufacturing Journal》2016,28(1-2):30-61
Tactical planning in hospitals involves elective patient admission planning and the allocation of hospital resource capacities. We propose a method to develop a tactical resource allocation and patient admission plan that takes stochastic elements into consideration, thereby providing robust plans. Our method is developed in an Approximate Dynamic Programming (ADP) framework and copes with multiple resources, multiple time periods and multiple patient groups with uncertain treatment paths and an uncertain number of arrivals in each time period. As such, the method enables integrated decision making for a network of hospital departments and resources. Computational results indicate that the ADP approach provides an accurate approximation of the value functions, and that it is suitable for large problem instances at hospitals, in which the ADP approach performs significantly better than two other heuristic approaches. Our ADP algorithm is generic, as various cost functions and basis functions can be used in various hospital settings. 相似文献
964.
Various software packages for project management include a procedure for resource-constrained scheduling. In several packages, the user can influence this procedure by selecting a priority rule. However, the resource-allocation methods that are implemented in the procedures are proprietary information; therefore, the question of how the priority-rule selection impacts the performance of the procedures arises. We experimentally evaluate the resource-allocation methods of eight recent software packages using the 600 instances of the PSPLIB J120 test set. The results of our analysis indicate that applying the default rule tends to outperform a randomly selected rule, whereas applying two randomly selected rules tends to outperform the default rule. Applying a small set of more than two rules further improves the project durations considerably. However, a large number of rules must be applied to obtain the best possible project durations. 相似文献
965.
966.
967.
Shoji Kawamura 《Genes & genomics.》2016,38(9):779-791
Color provides a reliable cue for object detection and identification during various behaviors such as foraging, mate choice, predator avoidance and navigation. The total number of colors that a visual system can discriminate is largely dependent on the number of different spectral types of cone opsins present in the retina and the spectral separations among them. Thus, opsins provide an excellent model system to study evolutionary interconnections at the genetic, phenotypic and behavioral levels. Primates have evolved a unique ability for three-dimensional color vision (trichromacy) from the two-dimensional color vision (dichromacy) present in the majority of other mammals. This was accomplished via allelic differentiation (e.g. most New World monkeys) or gene duplication (e.g. Old World primates) of the middle to long-wavelength sensitive (M/LWS, or red–green) opsin gene. However, questions remain regarding the behavioral adaptations of primate trichromacy. Allelic differentiation of the M/LWS opsins results in extensive color vision variability in New World monkeys, where trichromats and dichromats are found in the same breeding population, enabling us to directly compare visual performances among different color vision phenotypes. Thus, New World monkeys can serve as an excellent model to understand and evaluate the adaptive significance of primate trichromacy in a behavioral context. I shall summarize recent findings on color vision evolution in primates and introduce our genetic and behavioral study of vision-behavior interrelationships in free-ranging sympatric capuchin and spider monkey populations in Costa Rica. 相似文献
968.
Apolipoprotein C3 (ApoC3) plays a regulatory role in triglyceride (TG) metabolism. The higher level of TG can be a cause in pathogenesis of the vascular diseases or metabolic syndrome (MetS). In this study, we examined the associations of ApoC3 polymorphisms (?482C>T rs2854117 and 3238G>C rs5128) with Korean MetS patients. A total of 835 subjects were investigated, including 320 patients with MetS and 515 healthy subjects. The genotype analysis of the ApoC3 polymorphisms was performed by polymerase chain reaction-restriction fragment length polymorphism methods. Of the two polymorphisms studied, we observed a significant difference in the ?482C>T polymorphism between the MetS and control groups. The TT genotype of the ?482C>T polymorphism was associated with increased risk for MetS, compared with the controls (OR 1.627, 95 % CI 1.075–2.463, P = 0.021). The association was female-specific. No associations were found for the risk of MetS in the 3238G>C polymorphism. Haplotypes composed of two polymorphisms, however, were associated with MetS susceptibility in only male group. The 3238G>C polymorphism was significantly associated with TG levels (P = 0.013). Our data suggest that the ApoC3 ?482C>T polymorphism is associated with increased MetS susceptibility in the Korean population. 相似文献
969.
Yurong Jiang Shuijin Zhu Junjie Yuan Guolin Chen Guoquan Lu 《Genes & genomics.》2016,38(11):1013-1020
Betaine aldehyde dehydrogenase (BADH) is widely considered as a key enzyme in glycine betaine metabolism in higher plants. Several paralogous genes encoding different isozymes of BADH have been identified and characterized in some plants; however, until now, only limited information is available about BADH genes in quinoa (Chenopodium quinoa). Here, we report the molecular cloning, structural organization, phylogenetic evolution, and expression profile of a BADH gene (CqBADH1) from quinoa. The translated putative CqBADH1 protein included five conserved features of the ALDH Family 10. Comparisons between the cDNA and genomic sequences revealed that the CqBADH1 gene contained 15 exons and 14 introns. Comparative screening of introns in homologous genes demonstrated that the number and position of the BADH introns were highly conserved among the BADH genes in Amaranthaceae plants and in other more distantly related plant species. A phylogenetic analysis showed that CqBADH1 had the closest relationship with a protein from Atriplex canescens and belonged to the ALDH10 family. Expression profile analyses indicated that CqBADH1 was expressed only in root, and showed time-dependent expression profiles under NaCl-stress condition. Moreover, in quinoa, NaCl stress led to increased levels of CqBADH1 mRNA accompanied by the accumulation of glycine betaine. This is the first study to describe a BADH gene in quinoa. 相似文献
970.
Meihong Sun Xiuyan Zhao Nan Xu Xiaocui Luo Yuemin Zhang Ruirui Xu 《Genes & genomics.》2016,38(8):671-684
S-acylation is one of a group of lipid modifications that occurs on eukaryotic proteins, mediated by DHHC-CRD-containing proteins, which plays an important role in regulating the membrane association, trafficking and function of target proteins. Although genome-wide identification of PAT family has been carried out in yeast, mice, humans and Arabidopsis, little is known about apple PAT genes. In this study, a total of 33 putative apple PAT proteins, containing DHHC-CRD by domain analysis, have been identified, and were classified into three groups according to the phylogenetic analysis of PAT proteins in apple and Arabidopsis. More complex TMDs in the most MdPATs revealed the PM location of the gene family. Gene structure, gene chromosomal location and paralogs analysis of MdPAT genes within the apple genome demonstrated that tandem and segmental duplications, as well as whole genome duplications, have likely contributed to the expansion and evolution of the PAT gene family in apple. According to the microarray and expressed sequence tag (ESTs) analysis, the different expression patterns indicate that they may play different roles during fruit development and rootstock-scion interactions process. Moreover, PATs were performed expression profile analyses in different tissues, indicating that the PATs are involved in various aspects of physiological and developmental processes of apple. To our knowledge, this is the first report of a genome-wide analysis of the apple PAT gene family, and this genomic analysis of apple DHHC-CRD PAT genes provides the first step towards a functional study of this gene family in apple. 相似文献