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   1618篇
  免费   99篇
  国内免费   17篇
  1734篇
  2023年   18篇
  2022年   35篇
  2021年   44篇
  2020年   38篇
  2019年   37篇
  2018年   53篇
  2017年   51篇
  2016年   66篇
  2015年   79篇
  2014年   94篇
  2013年   122篇
  2012年   139篇
  2011年   134篇
  2010年   58篇
  2009年   56篇
  2008年   78篇
  2007年   78篇
  2006年   63篇
  2005年   65篇
  2004年   56篇
  2003年   55篇
  2002年   47篇
  2001年   40篇
  2000年   30篇
  1999年   18篇
  1998年   16篇
  1997年   9篇
  1996年   9篇
  1995年   8篇
  1993年   5篇
  1992年   9篇
  1991年   8篇
  1990年   4篇
  1989年   12篇
  1988年   9篇
  1987年   3篇
  1986年   9篇
  1985年   6篇
  1984年   6篇
  1983年   3篇
  1982年   3篇
  1981年   3篇
  1979年   4篇
  1978年   4篇
  1977年   6篇
  1976年   5篇
  1974年   3篇
  1970年   3篇
  1968年   3篇
  1933年   3篇
排序方式: 共有1734条查询结果,搜索用时 0 毫秒
81.
The group of small poor cods and pouts from the genus Trisopterus, belonging to the Gadidae family, comprises four described benthopelagic species that occur across the North-eastern Atlantic, from the Baltic Sea to the coast of Morocco, and the Mediterranean. Here, we combined molecular data from mitochondrial (cytochrome b) and nuclear (rhodopsin) genes to confirm the taxonomic status of the described species and to disentangle the evolutionary history of the genus. Our analyses supported the monophyly of the genus Trisopterus and confirmed the recently described species Trisopterus capelanus. A relaxed molecular clock analysis estimated an Oligocene origin for the group (∼30 million years ago; mya) indicating this genus as one of the most ancestral within the Gadidae family. The closure and re-opening of the Strait of Gibraltar after the Messinian Salinity Crisis (MSC) probably triggered the speciation process that resulted in the recently described T. capelanus.  相似文献   
82.
External genitalia development occurs through a combination of hormone independent, hormone dependent, and endocrine pathways. Perturbation of these pathways can lead to abnormal external genitalia development. We review human and animal mechanisms of normal and abnormal external genitalia development, and we evaluate abnormal mechanisms that lead to hypospadias. We also discuss recent laboratory findings that further our understanding of animal models of hypospadias.  相似文献   
83.
Background aimsMesenchymal stromal cells (MSC) are being used to treat and prevent a variety of clinical conditions. To be readily available, MSC must be cryopreserved until infusion. However, the optimal cryopreservation methods, cryoprotector solutions and MSC sensitivity to dimethyl sulfoxide (DMSO) exposure are unknown. This study investigated these issues.MethodsMSC samples were obtained from human umbilical cord (n = 15), expanded with Minimal Essential Medium-alpha (α-MEM) 10% human serum (HS), resuspended in 25 mL solution (HS, 10% DMSO, 20% hydroxyethyl starch) and cryopreserved using the BioArchive® system. After a mean of 18 ± 7 days, cell suspensions were thawed and diluted until a DMSO concentration of 2.5% was reached. Samples were tested for cell quantification and viability, immunophenotype and functional assays.ResultsPost-thaw cell recovery: 114 ± 2.90% (mean ± SEM). Recovery of viable cells: 93.46 ± 4.41%, 90.17 ± 4.55% and 81.03 ± 4.30% at 30 min, 120 min and 24 h post-thaw, respectively. Cell viability: 89.26 ± 1.56%, 72.71 ± 2.12%, 70.20 ± 2.39% and 63.02 ± 2.33% (P < 0.0001) pre-cryopreservation and 30 min, 120 min and 24 h post-thaw, respectively. All post-thaw samples had cells that adhered to culture bottles. Post-thaw cell expansion was 4.18 ± 0.17 ×, with a doubling time of 38 ± 1.69 h, and their capacity to inhibit peripheral blood mononuclear cells (PBMC) proliferation was similar to that observed before cryopreservation. Differentiation capacity, cell-surface marker profile and cytogenetics were not changed by the cryopreservation procedure.ConclusionsA method for cryopreservation of MSC in bags, in xenofree conditions, is described that facilitates their clinical use. The MSC functional and cytogenetic status and morphologic characteristics were not changed by cryopreservation. It was also demonstrated that MSC are relatively resistant to exposure to DMSO, but we recommend cell infusion as soon as possible.  相似文献   
84.
85.
86.
Particular RNA fragments obtained by action of pancreatic ribonuclease on purified RNAs originating from species totally unrelated to Agrobacterium tumefaciens (Escherichia coli, rabbit, monkey) are capable of inducing the formation of transplantable tumorous tissue when introduced at wounded sites in inverted stems of Datura stramonium maintained under axenic conditions on a medium containing auxin and kinetin. Reovirus RNA and a small size RNA (5–6 S) isolated from RNA bound RNA directed DNA polymerase from Escherichia coli also induced the appearance of tumorous tissues which grow on solid synthetic medium in the absence of auxin and kinetin.  相似文献   
87.

Background

Posaconazole is used for the prophylaxis of invasive fungal disease (IFD). Previous studies have shown it to be cost-effective compared to fluconazole/itraconazole. However, posaconazole has never been economically evaluated in developing countries.

Aims

The aim of the present study was to perform a cost-effectiveness analysis of posaconazole compared to fluconazole in public (SUS) and private hospitals (PHS) in Brazil.

Methods

A cost-effectiveness simulation was conducted on the basis of a pivotal study on the use of posaconazole in acute myeloid leukemia (AML) patients, adjusting the costs to Brazilian data.

Results

A pharmacoeconomic analysis was performed on a hypothetical sample of 100 patients in each drug group. The total cost of posaconazole use alone was USD$ 220,656.31, whereas that for fluconazole was USD$ 83,875.00. Our results showed that patients with IFD remain hospitalized for an additional 12 days, at an average cost of USD$ 850.85 per patient per day. The total money spent by PHS for 100 patients for 100 days was USD$ 342,318.00 for the posaconazole group and USD$ 302,039.00 for the fluconazole group. An analysis of sensitivity (10%) revealed no intergroup difference.

Conclusions

In Brazil posaconazole is cost-effective, and should be considered for the prophylaxis of patients with AMD/myelodysplasia (AML/MDS) undergoing chemotherapy.  相似文献   
88.
Responses of cultured rat trigeminal ganglion neurons to bitter tastants   总被引:3,自引:2,他引:1  
Liu  L; Simon  SA 《Chemical senses》1998,23(2):125-130
The initial steps in taste and olfaction result from the activation by chemical stimuli of taste receptor cells (TRCs) and olfactory receptor neurons (ORNs). In parallel with these two pathways is the chemosensitive trigeminal pathway whose neurons terminate in the oral and nasal cavities and which are activated by many of the same chemical stimuli that activate TRCs and ORNs. In a recent single unit study we investigated the responses of rat chorda tympani and glossopharnygeal neurons to a variety of bitter-tasting alkaloids, including nicotine, yohimbine, quinine, strychnine and caffeine, as well as capsaicin, the pungent ingredient in hot pepper. Here we apply many of these same compounds to cultured rat trigeminal ganglion (TG) neurons and measure changes in intracellular calcium [Ca2+]i to determine whether TG neurons will respond to these same compounds. Of the 89 neurons tested, 34% responded to 1 mM nicotine, 7% to 1 mM caffeine, 5% to 1 mM denatonium benzoate, 22% to 1 mM quinine hydrochloride, 18% to 1 mM strychnine and 55% to 1 microM capsaicin. These data suggest that neurons from the TG respond to the same bitter-tasting chemical stimuli as do TRCs and are likely to contribute information sent to the higher CNS regarding the perception of bitter/irritating chemical stimuli.   相似文献   
89.
90.
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