全文获取类型
收费全文 | 30275篇 |
免费 | 2523篇 |
国内免费 | 121篇 |
专业分类
32919篇 |
出版年
2022年 | 227篇 |
2021年 | 443篇 |
2020年 | 294篇 |
2019年 | 431篇 |
2018年 | 505篇 |
2017年 | 405篇 |
2016年 | 640篇 |
2015年 | 1001篇 |
2014年 | 1102篇 |
2013年 | 1569篇 |
2012年 | 1710篇 |
2011年 | 1603篇 |
2010年 | 1148篇 |
2009年 | 922篇 |
2008年 | 1358篇 |
2007年 | 1274篇 |
2006年 | 1231篇 |
2005年 | 1115篇 |
2004年 | 1130篇 |
2003年 | 1069篇 |
2002年 | 1126篇 |
2001年 | 989篇 |
2000年 | 885篇 |
1999年 | 804篇 |
1998年 | 384篇 |
1997年 | 390篇 |
1996年 | 301篇 |
1995年 | 310篇 |
1994年 | 235篇 |
1993年 | 280篇 |
1992年 | 538篇 |
1991年 | 512篇 |
1990年 | 469篇 |
1989年 | 433篇 |
1988年 | 347篇 |
1987年 | 341篇 |
1986年 | 331篇 |
1985年 | 371篇 |
1984年 | 351篇 |
1983年 | 307篇 |
1982年 | 221篇 |
1981年 | 230篇 |
1980年 | 210篇 |
1979年 | 272篇 |
1978年 | 240篇 |
1977年 | 263篇 |
1976年 | 253篇 |
1975年 | 247篇 |
1974年 | 245篇 |
1973年 | 234篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
921.
I De Dios M Manso V Leon A Lopez Borrasca 《Biochemical medicine and metabolic biology》1986,35(1):12-17
The specificity and affinity of eight lectins (concanavalin A, L. culinaris, P. sativum, phytohemagglutinin P, D. biflorus, soybean agglutinin, T. purpureus, and T. vulgaris) to B, T, T gamma, and T mu lymphocytes from the blood of normal subjects were determined. Lectins attached to latex particles were used to evaluate the binding of each lectin to individual cells. The rosette percentage found in each lymphocyte population expresses the specificity index and the specific sugar concentrations needed to decrease the rosette percentage by 50% is taken as the affinity index. B Lymphocytes showed a major subclass, with respect to T lymphocytes, with receptors for WGA, SBA, D. biflorus, L. culinaris, and P. sativum lectins. In contrast, T lymphocytes exhibit a greater number of cells with specific receptors for Con A, T. purpureus, and PHA lectins than B lymphocytes, the T gamma subpopulation being responsible for the specificity of the first two lectins and the T mu subpopulation for the PHA lectin. 相似文献
922.
Insulin and IGF receptors are developmentally regulated in the chick embryo eye lens 总被引:1,自引:0,他引:1
Lluis Bassas Peggy S. Zelenka Jose Serrano Flora De Pablo 《Experimental cell research》1987,168(2):561-566
We have previously reported that insulin-like growth factor (IGF) receptors appear to predominate over insulin receptors in early stages of embryogenesis in the chick (days 2-3 whole embryo membranes). Overall, [125I]IGF I and II binding to specific receptors was maximal when the rate of brain growth is highest. In the present study we used the embryonic chick lens, a well-defined tissue composed of a single type of cell, to analyse whether changes of insulin and IGF I binding are correlated with changes in growth rate and differentiation state of the cells. We show that both insulin receptors and IGF receptors are present in the lens epithelial cells, and that each type is distinctly regulated throughout development. While there is a direct correlation between IGF-binding capability and growth rate of the cells, there is less relation to differentiation status and embryo age. Insulin receptors, by contrast, appear to be mostly related to the differentiated state of cells, decreasing sharply in fibers, irrespective of their developmental age. 相似文献
923.
B Velkeniers P Buydens A Baldys S De Boel E Finné J Golstein L Vanhaelst 《Life sciences》1987,40(25):2415-2420
In adult male Wistar rats submitted to a standardized noise stress, intravenous TRH induced a prolactin (PRL) secretory response. Prior IV naloxone administration not only lowered plasma PRL levels in those stressed rats but abolished also the stimulatory action of TRH. This effect was further studied by superfusion experiments on enriched PRL cell suspensions (70% lactotrophs) from female adult Wistar rats. Naloxone kept unaffected the basal PRL secretion but lowered significantly that induced by TRH. These experiments suggest a dual effect of naloxone on rat PRL secretion, one exerted on central opioid receptors lowering stress-related increased basal PRL levels, the other inhibiting the TRH-dependent PRL secretion exerted at the lactotroph level itself. 相似文献
924.
B Birdsall J De Graw J Feeney S Hammond M S Searle G C Roberts W T Colwell J Crase 《FEBS letters》1987,217(1):106-110
The binding of folate to Lactobacillus casei dihydrofolate reductase in the presence and absence of NADP+ has been studied by 15N NMR, using [5-15N]folate. In the presence of NADP+, three separate signals were observed for the single 15N atom, in agreement with our earlier evidence from 1H and 13C NMR for multiple conformations of this complex [(1982) Biochemistry 21, 5831-5838]. The 15N spectra of the binary enzyme-folate complex provide evidence for the first time that this complex also exists in at least two conformational states. This is confirmed by the observation of two separate resonances for the 7-proton of bound folate, located by two-dimensional exchange spectroscopy. 相似文献
925.
926.
Hans J. De Boeck Juliette M. G. Bloor Rien Aerts Michael Bahn Claus Beier Bridget A. Emmett Marc Estiarte Jos M. Grünzweig Aud H. Halbritter Petr Holub Anke Jentsch Karel Klem Juergen Kreyling Gyrgy Krel‐Dulay Klaus Steenberg Larsen Alexandru Milcu Jacques Roy Bjarni D. Sigurdsson Melinda D. Smith Marcelo Sternberg Vigdis Vandvik Thomas Wohlgemuth Ivan Nijs Alan K. Knapp 《Global Change Biology》2020,26(2):e6-e7
927.
A unified framework to model the potential and realized distributions of invasive species within the invaded range 下载免费PDF全文
Tarek Hattab Carol X. Garzón‐López Michael Ewald Sandra Skowronek Raf Aerts Hélène Horen Boris Brasseur Emilie Gallet‐Moron Fabien Spicher Guillaume Decocq Hannes Feilhauer Olivier Honnay Pieter Kempeneers Sebastian Schmidtlein Ben Somers Ruben Van De Kerchove Duccio Rocchini Jonathan Lenoir 《Diversity & distributions》2017,23(7):806-819
928.
929.
Xu J Reumers J Couceiro JR De Smet F Gallardo R Rudyak S Cornelis A Rozenski J Zwolinska A Marine JC Lambrechts D Suh YA Rousseau F Schymkowitz J 《Nature chemical biology》2011,7(5):285-295
Many p53 missense mutations possess dominant-negative activity and oncogenic gain of function. We report that for structurally destabilized p53 mutants, these effects result from mutant-induced coaggregation of wild-type p53 and its paralogs p63 and p73, thereby also inducing a heat-shock response. Aggregation of mutant p53 resulted from self-assembly of a conserved aggregation-nucleating sequence within the hydrophobic core of the DNA-binding domain, which becomes exposed after mutation. Suppressing the aggregation propensity of this sequence by mutagenesis abrogated gain of function and restored activity of wild-type p53 and its paralogs. In the p53 germline mutation database, tumors carrying aggregation-prone p53 mutations have a significantly lower frequency of wild-type allele loss as compared to tumors harboring nonaggregating mutations, suggesting a difference in clonal selection of aggregating mutants. Overall, our study reveals a novel disease mechanism for mutant p53 gain of function and suggests that, at least in some respects, cancer could be considered an aggregation-associated disease. 相似文献
930.
Assessment of two flexible and compatible SNP genotyping platforms: TaqMan SNP Genotyping Assays and the SNPlex Genotyping System 总被引:3,自引:0,他引:3
In this review we describe the principles, protocols, and applications of two commercially available SNP genotyping platforms, the TaqMan SNP Genotyping Assays and the SNPlex Genotyping System. Combined, these two technologies meet the requirements of multiple SNP applications in genetics research and pharmacogenetics. We also describe a set of SNP selection tools and validated assay resources which we developed to accelerate the cycle of experimentation on these platforms. Criteria for selecting the more appropriate of these two genotyping technologies are presented: the genetic architecture of the trait of interest, the throughput required, and the number of SNPs and samples needed for a successful study. Overall, the TaqMan assay format is suitable for low- to mid-throughput applications in which a high assay conversion rate, simple assay workflow, and low cost of automation are desirable. The SNPlex Genotyping System, on the other hand, is well suited for SNP applications in which throughput and cost-efficiency are essential, e.g., applications requiring either the testing of large numbers of SNPs and samples, or the flexibility to select various SNP subsets. 相似文献