全文获取类型
收费全文 | 32239篇 |
免费 | 2282篇 |
国内免费 | 4586篇 |
出版年
2024年 | 28篇 |
2023年 | 506篇 |
2022年 | 558篇 |
2021年 | 922篇 |
2020年 | 879篇 |
2019年 | 1145篇 |
2018年 | 913篇 |
2017年 | 865篇 |
2016年 | 924篇 |
2015年 | 1141篇 |
2014年 | 1541篇 |
2013年 | 2157篇 |
2012年 | 1506篇 |
2011年 | 1533篇 |
2010年 | 1339篇 |
2009年 | 1646篇 |
2008年 | 1808篇 |
2007年 | 1951篇 |
2006年 | 1995篇 |
2005年 | 1846篇 |
2004年 | 1713篇 |
2003年 | 1611篇 |
2002年 | 1473篇 |
2001年 | 1203篇 |
2000年 | 999篇 |
1999年 | 918篇 |
1998年 | 776篇 |
1997年 | 653篇 |
1996年 | 636篇 |
1995年 | 657篇 |
1994年 | 626篇 |
1993年 | 446篇 |
1992年 | 389篇 |
1991年 | 323篇 |
1990年 | 274篇 |
1989年 | 189篇 |
1988年 | 207篇 |
1987年 | 187篇 |
1986年 | 135篇 |
1985年 | 120篇 |
1984年 | 105篇 |
1983年 | 49篇 |
1982年 | 64篇 |
1981年 | 33篇 |
1980年 | 36篇 |
1979年 | 24篇 |
1978年 | 18篇 |
1977年 | 10篇 |
1976年 | 16篇 |
1950年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
The release of genetically engineered micro-organisms and viruses into the environment 总被引:2,自引:0,他引:2
GLYNIS GIDDINGS 《The New phytologist》1998,140(2):173-184
This review considers the reasons for, and research governing, the regulation and monitoring of genetically engineered micro-organisms and viruses (GEMs) released into the environment. The hazards associated with releasing GEMs into the environment are the creation and evolution of new pests and diseases, and damage to the ecosystem and non target species. The similarities and differences between GEMs and conventional micro-organisms are discussed in relation to risk assessment. Other issues covered include the persistence of micro-organisms in the environment, transgene dispersal to non-engineered microbes and other organisms, the effects of transgenes and transformation on fitness, and the evolution of pests and pathogens that are given or acquire transgenes. Areas requiring further research are identified and recommendations for risk assessment made. 相似文献
42.
43.
《Cell》2021,184(23):5807-5823.e14
44.
We re-engineered a classic tool for mutagenesis and gene expression studies in Gram-negative bacteria. Our modified Tn5-based transposon contains multiple features that allow rapid selection for mutants, direct quantification of gene expression and straightforward cloning of the inactivated gene. The promoter-less gfp-km cassette provides selection and reporter assay depending on the activity of the promoter upstream of the transposon insertion site. The cat gene facilitates positive antibiotic selection for mutants, while the narrow R6Kγ replication origin forces transposition in recipient strains lacking the pir gene and enables cloning of the transposon flanked with the disrupted gene from the chromosome. The suicide vector pCKD100, a plasmid that could be delivered into recipient cells through biparental mating or electroporation, harbours the modified transposon. We used the transposon to mutagenize Pectobacterium versatile KD100, Pseudumonas coronafaciens PC27R and Escherichia coli 35150N. The fluorescence intensities of mutants expressing high GFP could be quantified and detected qualitatively. Transformation efficiency from conjugation ranged from 1600 to 1900 CFU per ml. We sequenced the upstream flanking regions, identified the putative truncated genes and demonstrated the restoration of the GFP phenotype through marker exchange. The mini-Tn5 transposon was also utilized to construct mutant a library of P. versatile for forward genetic screens. 相似文献
45.
目的:了解F10基因在部分正常组织及肿瘤组织中的表达情况。方法:利用原位杂交和免疫组化方法对F10在部分正常组织和肿瘤组织中的mRNA和蛋白表达情况进行分析。结果:F10基因不仅在腺癌组织中表达呈阳性,在鳞癌组织中表现出较腺癌更强的强阳性,并且在正常组织中也有一定的表达。结论:F10是一个在多种组织普遍表达的细胞内蛋白,其功能可能与物质转运相关。 相似文献
46.
47.
《Bioscience, biotechnology, and biochemistry》2013,77(5):1190-1198
The Rhynchosciara americana C3-22 gene is located in an amplified domain and is developmentally expressed. The aim of the present work was to identify intrinsically bent DNA sites in a segment containing the gene promoter and downstream sequence. The results indicated that this gene is flanked by intrinsically bent DNA sites. Three bent DNA sites (b?3, b?2, and b?1) were localized in the promoter, and one was localized downstream of the gene (b+1). These sites had helical parameters that confirmed the curved structure, as well as segments with left-handed superhelical writhe. In silico analysis of the promoters of four other insect genes, which encode secreted polypeptides, showed that they all had curved structures and similar helical parameters. Correlation with other results indicates that the detected intrinsically bent DNA sites that flank the C3-22 gene might be a consensus feature of the gene structure in the amplified domains. 相似文献
48.
Tae Kyung Han 《Journal of Exercise Nutrition & Biochemistry》2013,17(4):209-217
The purpose of the current study was to investigate whether or not the FABP2 gene polymorphism modulated obesity indices, hemodynamic factor, blood lipid factor, and insulin resistance markers through 12-week aerobic exercise training in abdominal obesity group of Korean mid-life women. A total of 243 abdominally obese subjects of Korean mid-life women voluntarily participated in aerobic exercise training program for 12 weeks. Polymerase Chain Reaction with Restriction Fragment Length Polymorphism (PCR-RFLP) assay was used to assess the FABP2 genotype of the participants (117 of AA homozygotes, 100 of AT heterozygotes, 26 of TT homozygotes). Prior to the participation of the exercise training program, baseline obesity indices, hemodynamic factor, blood lipid factor, and insulin resistance markers were measured. All the measurements were replicated following the 12-week aerobic exercise training program, and then the following results were found. After 12-week aerobic exercise training program, wild type (Ala54Ala) and mutant type (Ala54Thr+Thr54Thr) significantly decreased weight (P > .001), BMI (P > .001), %bf (P > .001), waist circumference (P > .001), WHR (P > .001), muscle mass (wild type p < .022; mutant type P > .001), RHR (P > .001), viseceral adipose area (wild type p < .005; mutant type P > .001), subcutaneous area (P > .001), insulin (wild type p < .005; mutant type P > .001) and significantly increased VO2max (P > .001). And wild type significantly decresed NEFA (P > .05), glucose (P > .05), OGTT 120min glucose (P > .05) and significantly increased HDLC (p > .005). Mutant type significantly decreased SBP (P > .001), DBP (P > .01), TC (P > .01), LPL (P > .05), LDL (P > .001), HOMA index (P > .01). The result of the present study represents that regular aerobic exercise training may beneficially prevent obesity index, blood pressure, blood lipids and insulin resistance markers independent of FABP Ala54Thr wild type and mutant type. 相似文献
49.
《Autophagy》2013,9(6):816-818
Autophagy, a specialized lysosomal degradation pathway, has proven to be a potent cell-autonomous defense mechanism against a range of intracellular microbes. In addition, autophagy emerged recently as a critical regulator of innate and adaptive immune responses. Links between autophagy and innate immunity are being progressively unveiled. For instance, several TLR (Toll-Like Receptor) agonists upregulate autophagy flux in immune cell types such as DC (dendritic cells) or macrophages. Conversely, and perhaps surprisingly, is the observation that TLR7-mediated responses might depend on autophagy in plasmacytoid DC, thus suggesting a more complex link between TLR-dependent responses and autophagy. Recently, the demonstration that NOD2 increases autophagy suggests that innate immune responses initiated via a broad range of pathogen recognition receptors can regulate autophagy. In addition to its involvement in innate immune responses, autophagy regulates adaptive immune responses via both MHC class I and class II molecules depending on the cellular context and the nature of the antigen. 相似文献
50.
The vegetables germplasm conservation programme in Poland was started in 1982, activities under this program resulted up to
this date in building up a tomato germplasm collection of 782 accessions that are available for distribution to breeders and
researchers in Poland and abroad. Between 1990 and 1999 we distributed 651 tomato seed samples to breeders and scientists
in Poland, and 95 samples to users abroad. During 1990 – 1999 the 652 tomato accessions were evaluated for 43 traits of plants
and fruits. Work is in progress to expand the collection and identify useful characteristics of the collected material, and
to make use of them in breeding and other research works. 相似文献