全文获取类型
收费全文 | 2202篇 |
免费 | 164篇 |
国内免费 | 1篇 |
出版年
2022年 | 14篇 |
2021年 | 30篇 |
2020年 | 14篇 |
2019年 | 41篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 61篇 |
2015年 | 108篇 |
2014年 | 87篇 |
2013年 | 150篇 |
2012年 | 153篇 |
2011年 | 114篇 |
2010年 | 110篇 |
2009年 | 81篇 |
2008年 | 101篇 |
2007年 | 100篇 |
2006年 | 128篇 |
2005年 | 90篇 |
2004年 | 103篇 |
2003年 | 82篇 |
2002年 | 85篇 |
2001年 | 43篇 |
2000年 | 45篇 |
1999年 | 25篇 |
1998年 | 25篇 |
1997年 | 15篇 |
1996年 | 15篇 |
1995年 | 17篇 |
1994年 | 20篇 |
1993年 | 16篇 |
1992年 | 22篇 |
1991年 | 33篇 |
1990年 | 30篇 |
1989年 | 21篇 |
1988年 | 20篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1974年 | 14篇 |
1973年 | 18篇 |
1970年 | 9篇 |
排序方式: 共有2367条查询结果,搜索用时 15 毫秒
1.
Optimized linker sequences for the expression of monomeric and dimeric bispecific single-chain diabodies. 总被引:5,自引:0,他引:5
Bispecific single-chain diabodies (scDb) consist of the variable heavy and light chain domains of two antibodies connected by three linkers. The structure of an scDb in the V(H)-V(L) orientation is V(H)A-linkerA-V(L)B-linkerM-V(H)B-linkerB-V(L)A, with linkers A and B routinely chosen to be 5-6 residues and linker M 15-20 residues. Here, we applied display of scDb on filamentous phage to analyse the composition of optimal linker sequences. The three linkers were randomized in length and sequence using degenerated triplets coding for only six hydrophilic or aliphatic amino acids (Thr, Ser, Asp, Asn, Gly, Ala). Antigen-binding clones were then isolated by one to two rounds of selection on the two different antigens recognized by the bispecific scDb. Using an scDb directed against carcinoembryonic antigen (CEA) and beta-galactosidase (Gal), we found that monomeric scDb had a preferred length of 15 or more amino acid residues for the middle linker M and of 3-6 residues for the linkers A and B. No obvious bias towards a preferred linker sequence was observed. Reduction of the middle linker below 13 residues led to the formation of dimeric scDb, which most likely results from interchain pairing between all the V(H) and V(L) domains. Dimeric scDb were also formed by fragments possessing a long linker M and linkers A and B of 0 or 1 residue. We assume that these dimeric scDb are formed by intrachain pairing of the central variable domains and interchain pairing of the flanking variable domains. Thus, the latter molecules represent a novel format of bispecific and tetravalent molecules. The described strategy allows for the isolation of both optimized and minimal linker sequences for the assembly of monomeric or dimeric single-chain diabodies. 相似文献
2.
Valentina Isetta Josep M. Montserrat Raquel Santano Alison J. Wimms Dinesh Ramanan Holger Woehrle Daniel Navajas Ramon Farré 《PloS one》2016,11(3)
Bench testing is a useful method to characterize the response of different automatic positive airway pressure (APAP) devices under well-controlled conditions. However, previous models did not consider the diversity of obstructive sleep apnea (OSA) patients’ characteristics and phenotypes. The objective of this proof-of-concept study was to design a new bench test for realistically simulating an OSA patient’s night, and to implement a one-night example of a typical female phenotype for comparing responses to several currently-available APAP devices. We developed a novel approach aimed at replicating a typical night of sleep which includes different disturbed breathing events, disease severities, sleep/wake phases, body postures and respiratory artefacts. The simulated female OSA patient example that we implemented included periods of wake, light sleep and deep sleep with positional changes and was connected to ten different APAP devices. Flow and pressure readings were recorded; each device was tested twice. The new approach for simulating female OSA patients effectively combined a wide variety of disturbed breathing patterns to mimic the response of a predefined patient type. There were marked differences in response between devices; only three were able to overcome flow limitation to normalize breathing, and only five devices were associated with a residual apnea-hypopnea index of <5/h. In conclusion, bench tests can be designed to simulate specific patient characteristics, and typical stages of sleep, body position, and wake. Each APAP device behaved differently when exposed to this controlled model of a female OSA patient, and should lead to further understanding of OSA treatment. 相似文献
3.
4.
David Gutirrez‐Larruscain Santiago Andrs‐Snchez Enrique Rico María Montserrat Martínez‐Ortega 《植物分类学报:英文版》2019,57(1):42-54
Forty-five populations of Pentanema corresponding to seven species included in the Pentanema conyzae clade have been studied using AFLP fingerprinting. The results show that allopolyploidization could have been involved in the diversification of this group, specifically in species P. langeanum and P. maletii. Molecular data confirm the presence of P. britannicum in the Iberian Peninsula and key steps are provided to identify the species that are morphologically the most challenging. 相似文献
5.
Distinct effects of climate warming on populations of silver fir (Abies alba) across Europe 下载免费PDF全文
6.
B Vernet-der-Garabédian E Morel J F Bach 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1984,298(16):449-456
Inhibitory effect of myasthenic patients antibodies on alpha-bungarotoxin binding to the human acetylcholine receptor has been demonstrated by radioimmunoassay. By using decamethonium, an acetylcholine agonist, we have shown the existence of two antibody sub-groups reacting with the toxin-binding site: one sub-group is represented by antibodies which block the binding directly, the other by antibodies that inhibit the binding, only in the presence of decamethonium. 相似文献
7.
The activation of the phagocyte oxidative respiratory burst by various mycobacteria was evaluated in an in vitro assay, by measuring the chemiluminescence, associated to the release of oxidizing species, generated by normal human whole blood phagocytes. All mycobacterium species, except Mycobacterium leprae, induced a significant chemiluminescence response. The strongest stimulus was provided by BCG, followed by M. triviale, M. chelonei, and M. fortuitum. M. kansasii, M. intracellulare, and M. lepraemurium elicited a weak response, although higher than that triggered by M. leprae. Both polymorphonuclear and mononuclear cells contributed to the whole blood cell chemiluminescence stimulated by mycobacteria, mononuclear cells being more efficient on a per cell basis. Phagocyte activation by recombinant interferon gamma did not improve M. leprae ability to trigger a significant chemiluminescence response. The failure of M. leprae and of some atypical mycobacteria to stimulate a strong phagocyte oxidative respiratory burst may have some relevance to their pathogenicity. 相似文献
8.
Target Detection Assay (TDA): a versatile procedure to determine DNA binding sites as demonstrated on SP1 protein. 总被引:34,自引:10,他引:24 下载免费PDF全文
We developed a rapid method designated Target Detection Assay (TDA) to determine DNA binding sites for putative DNA binding proteins. A purified, functionally active DNA binding protein and a pool of random double-stranded oligonucleotides harbouring PCR primer sites at each end are included the TDA cycle which consists of four separate steps: a DNA protein incubation step, a protein DNA complex separation step, a DNA elution step and a polymerase chain reaction (PCR) DNA amplification step. The stringency of selection can be increased in consecutive TDA cycles. Since tiny amounts of retained DNA can be rescued by PCR, buffer systems, salt concentrations and competitor DNA contents can be varied in order to determine high affinity binding sites for the protein of choice. To test the efficiency of the TDA procedure potential DNA binding sites were selected by the DNA binding protein SP1 from a pool of oligonucleotides with random nucleotides at 12 positions. Target sites selected by recombinant SP1 closely matched the SP1 consensus site. If DNA recognition sites have to be determined for known, mutated or putative DNA binding proteins, the Target Detection Assay (TDA) is a versatile and rapid technique for consideration. 相似文献
9.
Prolonged submaximal exercise and L-carnitine in humans 总被引:1,自引:0,他引:1
S Oyono-Enguelle H Freund C Ott M Gartner A Heitz J Marbach F Maccari A Frey H Bigot A C Bach 《European journal of applied physiology and occupational physiology》1988,58(1-2):53-61
Changes in the main physiological parameters and circulating indicators of carbohydrate, protein, lipid (and ketone body) metabolism were measured in ten exercising subjects before L-carnitine (L-carn) loading, after 4 weeks of daily loading with 2 g L-carn, and 6-8 weeks after terminating L-carn administration. Measurements were made on venous blood samples collected during each experiment at fixed time intervals over an initial rest of 45 min, 60 min bicycle exercise performed near 50% VO2max and 120 min recovery. Free and total plasma carnitine levels reached a plateau corresponding to an average rise of 25% for both fractions, 9-10 days after the beginning of the L-carn diet. These levels returned to their initial values 6-8 weeks after cessation of the supply. Generally L-carn supplementation did not significantly modify the physiological parameters and circulating metabolites. No distinct increase of the relative participation of endogenous lipids in the fuel supply of prolonged submaximal exercise was observed. In normal human subjects the increased demand for fatty acid oxidation resulting from exercise seems to be adequately supported by endogenous levels of carnitine. 相似文献
10.