全文获取类型
收费全文 | 2387篇 |
免费 | 174篇 |
专业分类
2561篇 |
出版年
2023年 | 20篇 |
2022年 | 17篇 |
2021年 | 35篇 |
2020年 | 23篇 |
2019年 | 28篇 |
2018年 | 75篇 |
2017年 | 50篇 |
2016年 | 91篇 |
2015年 | 130篇 |
2014年 | 137篇 |
2013年 | 171篇 |
2012年 | 204篇 |
2011年 | 153篇 |
2010年 | 114篇 |
2009年 | 84篇 |
2008年 | 124篇 |
2007年 | 125篇 |
2006年 | 112篇 |
2005年 | 98篇 |
2004年 | 77篇 |
2003年 | 77篇 |
2002年 | 70篇 |
2001年 | 35篇 |
2000年 | 22篇 |
1999年 | 35篇 |
1998年 | 14篇 |
1997年 | 19篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 30篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 27篇 |
1988年 | 11篇 |
1987年 | 16篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1979年 | 9篇 |
1975年 | 15篇 |
1974年 | 13篇 |
1973年 | 18篇 |
1971年 | 10篇 |
1970年 | 11篇 |
1969年 | 8篇 |
1968年 | 34篇 |
1967年 | 10篇 |
排序方式: 共有2561条查询结果,搜索用时 9 毫秒
161.
162.
163.
Tiziana Vigliarolo Lucrezia Guida Enrico Millo Chiara Fresia Emilia Turco Antonio De Flora Elena Zocchi 《The Journal of biological chemistry》2015,290(21):13042-13052
Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [3H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [3H]ABA and [35S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone. 相似文献
164.
Victòria Marfâ Enric Mele Jean Michael Vassal Joaquima Messeguer 《In vitro cellular & developmental biology. Plant》2002,38(4):310-315
Summary To determine the degree of insect resistance in transgenic plants, different bioassays are used which typically use either
whole plant or small pieces of leaves or stems of transgenic plants, following culture under greenhouse conditions. An in vitro insect-feeding bioassay is presented which permits the infestation of transgenic plantlets with newly hatched larvae from
the striped stem borer. The bioassay consists of the germination of rice seeds in vitro using Murashige and Skoog medium in test tubes, and then infestation of each 3–4 cm long seedling with one neonate larva
obtained from surfacesterilized eggs of Chilo suppressalis. The infested in vitro plantlets are kept in culture rooms at 25°C for several days and then the seedling damage and the growth of the larvae are
analyzed. Senia (japonica variety) homozygous transgenic rice plants were used for these experiments. The plants were transformed
with either the cry1B or the maize proteinase inhibitor (mpi) genes. Both genes confer resistance to Chilo suppressalis. With non-transformed plants the larvae grew and developed normally, feeding on the small rice plantlets. In contrast, with
cry1B plants, the neonate larvae died during the first days of the infestation. These plantlets recovered completely and developed
similarly to the non-infested control plants. With transgenic plants transformed with the mpi gene, the neonate larvae did not die but grew more slowly compared with the controls. Thus, this in vitro insect-feeding bioassay is a rapid and easy method to detect the resistance of cry and mpi transgenic plants to stem borers such as Chilo suppressalis. 相似文献
165.
Milena Nasi Sara De Biasi Elena Bianchini Lara Gibellini Marcello Pinti Tiziana Scacchetti Tommaso Trenti Vanni Borghi Cristina Mussini Andrea Cossarizza 《PloS one》2015,10(1)
Background
An accurate and affordable CD4+ T cells count is an essential tool in the fight against HIV/AIDS. Flow cytometry (FCM) is the “gold standard” for counting such cells, but this technique is expensive and requires sophisticated equipment, temperature-sensitive monoclonal antibodies (mAbs) and trained personnel. The lack of access to technical support and quality assurance programs thus limits the use of FCM in resource-constrained countries. We have tested the accuracy, the precision and the carry-over contamination of Partec CyFlow MiniPOC, a portable and economically affordable flow cytometer designed for CD4+ count and percentage, used along with the “CD4% Count Kit-Dry”.Materials and Methods
Venous blood from 59 adult HIV+ patients (age: 25–58 years; 43 males and 16 females) was collected and stained with the “MiniPOC CD4% Count Kit-Dry”. CD4+ count and percentage were then determined in triplicate by the CyFlow MiniPOC. In parallel, CD4 count was performed using mAbs and a CyFlow Counter, or by a dual platform system (from Beckman Coulter) based upon Cytomic FC500 (“Cytostat tetrachrome kit” for mAbs) and Coulter HmX Hematology Analyzer (for absolute cell count).Results
The accuracy of CyFlow MiniPOC against Cytomic FC500 showed a correlation coefficient (CC) of 0.98 and 0.97 for CD4+ count and percentage, respectively. The accuracy of CyFlow MiniPOC against CyFlow Counter showed a CC of 0.99 and 0.99 for CD4 T cell count and percentage, respectively. CyFlow MiniPOC showed an excellent repeatability: CD4+ cell count and percentage were analyzed on two instruments, with an intra-assay precision below ±5% deviation. Finally, there was no carry-over contamination for samples at all CD4 values, regardless of their position in the sequence of analysis.Conclusion
The cost-effective CyFlow MiniPOC produces rapid, reliable and accurate results that are fully comparable with those from highly expensive dual platform systems. 相似文献166.
Youry Pii Massimo Crimi Giorgia Cremonese Angelo Spena Tiziana Pandolfini 《BMC plant biology》2007,7(1):21
Background
Rhizobia symbionts elicit root nodule formation in leguminous plants. Nodule development requires local accumulation of auxin. Both plants and rhizobia synthesise auxin. We have addressed the effects of bacterial auxin (IAA) on nodulation by using Sinorhizobium meliloti and Rhizobium leguminosarum bacteria genetically engineered for increased auxin synthesis. 相似文献167.
168.
An anther-derived doubled haploid (DH) population and an F2 mapping population were developed from an intraspecific hybrid between the eggplant breeding lines 305E40 and 67/3. The former incorporates an introgressed segment from Solanum aethiopicum Gilo Group carrying the gene Rfo-sa1, which confers resistance to Fusarium oxysporum; the latter is a selection from an intraspecific cross involving two conventional eggplant varieties and lacks Rfo-sa1. Initially, 28 AFLP primer combinations (PCs) were applied to a sample of 93 F2 individuals and 93 DH individuals, from which 170 polymorphic AFLP fragments were identified. In the DH population, the segregation of 117 of these AFLPs as well as markers closely linked to Rfo-sa1 was substantially distorted, while in the F2 population, segregation distortion was restricted to just 10 markers, and thus the latter was chosen for map development. A set of 141 F2 individuals was genotyped with 73 AFLP PCs (generating 406 informative markers), 32 SSRs, 4 tomato RFLPs, and 3 CAPS markers linked to Rfo-sa1. This resulted in the assignment of 348 markers to 12 major linkage groups. The framework map covered 718.7?cM, comprising 238 markers (212 AFLPs, 22 SSRs, 1 RFLP, and the Rfo-sa1 CAPS). Marker order and inter-marker distances in this eggplant map were largely consistent with those reported in a recently published SSR-based map. From an eggplant breeding perspective, DH populations produced by anther culture appear to be subject to massive segregation distortion and thus may not be very efficient in capturing the full range of genetic variation present in the parental lines. 相似文献
169.
Anaerobic reaction of ascorbate oxidase with ascorbate 总被引:1,自引:0,他引:1
L Avigliano G Rotilio S Urbanelli B Mondovi A F Agrò 《Archives of biochemistry and biophysics》1978,185(2):419-422
Ascorbate oxidase is fully reduced by 4 mol of ascorbate in the absence of air, as monitored by optical and electron paramagnetic resonance spectra. At less than stoichiometric ascorbate concentration there is a slow equilibration between the 605-and 330-nm absorption bands: The 605-nm chromophore is first reduced, then its color reappears while the 330-nm absorption band decreases. Upon reoxidation with air the process takes place in the opposite direction. Intramolecular rather than intermolecular electron exchange appears to be responsible for this process. The reduced protein is about twice as fluorescent as the oxidized protein. The fluorescence quenching in the oxidized protein is related to the 330-nm absorption band rather than to the 605-nm band as previously reported for laccase. 相似文献
170.
Dario Sorrentino Marco Marino Themistocles Dassopoulos Dimitra Zarifi Tiziana Del Bianco 《PloS one》2015,10(12)