全文获取类型
收费全文 | 716篇 |
免费 | 60篇 |
专业分类
776篇 |
出版年
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2018年 | 11篇 |
2016年 | 8篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 28篇 |
2012年 | 37篇 |
2011年 | 31篇 |
2010年 | 16篇 |
2009年 | 19篇 |
2008年 | 28篇 |
2007年 | 32篇 |
2006年 | 20篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 28篇 |
2002年 | 24篇 |
2001年 | 17篇 |
2000年 | 22篇 |
1999年 | 23篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 6篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 18篇 |
1978年 | 9篇 |
1977年 | 11篇 |
1976年 | 12篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 10篇 |
1971年 | 8篇 |
1969年 | 5篇 |
1968年 | 8篇 |
排序方式: 共有776条查询结果,搜索用时 0 毫秒
11.
A G Diamond G W Butcher J C Howard 《Journal of immunology (Baltimore, Md. : 1950)》1984,132(3):1169-1175
We describe two monoclonal antibodies, R3/47 and YR1/1, directed against different epitopes of the expressed rat class I major transplantation antigen RT1Aa, that interact with each other so that the binding of one antibody, YR1/1, is greatly enhanced by the binding of the other. The positive interaction between R3/47 and YR1/1 also occurs when using RT1Aa molecules solubilized from cell membranes in detergent. It is therefore unlikely that the molecular environment of the membrane contributes to the interaction. The ability of R3/47 to modify the YR1/1 determinant on the RT1Aa molecule is mediated without any significant loss of potency by highly purified monomeric Fab fragments. This result suggests that the binding of R3/47 to the RT1Aa molecule alters the YR1/1 determinant by initiating a propagated conformational change in the antigen. 相似文献
12.
Polyribosome binding of rabbit globin messenger RNA and messenger ribonucleoprotein labelled with bacteriophage-T4 RNA ligase and 5''-[32P] phosphocytidine 3''-phosphate 总被引:2,自引:1,他引:1 下载免费PDF全文
Rabbit polyribosomal globin messenger RNA (mRNA) and messenger ribonucleoprotein (mRNP) were labelled at the 3′ poly(A) tail to high specific activity with T4 RNA ligase and [5′-32P]pCp without consequent loss of functional activity. Labelled message was translated in both micrococcal nuclease treated and untreated rabbit reticulocyte lysates, as shown by the formation of labelled polyribosomes. The utilisation of labelled messenger was abolished by T2 toxin or sodium fluoride which are known to inhibit protein synthesis. 相似文献
13.
14.
R W Butcher R J Ho H C Meng E W Sutherland 《The Journal of biological chemistry》1965,240(11):4515-4523
15.
16.
Melaleuca alternifolia andM. linariifolia are commercially important Australian species harvested for their essential oils. Both species have relatively narrow and disjunct distributions on the central coast of eastern Australia. Variation in the chloroplast genome was assessed for eight individuals from each of twelve populations, representing the species' geographic range. Low nucleotide diversity withinM. alternifolia contrasted with high nucleotide diversity inM. linariifolia. CpDNA data are consistent with the southern population ofM. alternifolia being a hybrid population withM. linariifolia. The two species are sympatric in this region. Variation inM. linariifolia was geographically structured, with northern populations differing from southern populations by seven restriction site mutations, five length mutations and an inversion. There was no evidence of hybridisation of the cp genome of northernM. linariifolia with the partially sympatric speciesM. trichostachya. Intra- and interspecific variation in the chloroplast genomes ofM. alternifolia, M. linariifolia, andM. trichostachya indicate considerable potential for the use of intraspecific cpDNA studies in examining phylogenetic relationships in melaleucas. 相似文献
17.
A homing receptor-bearing cortical thymocyte subset: implications for thymus cell migration and the nature of cortisone-resistant thymocytes 总被引:6,自引:0,他引:6
The thymus exports a selected subset of virgin T lymphocytes to the peripheral lymphoid organs. The mature phenotype of these thymus emigrants is similar to that of medullary thymocytes and has been cited as supporting a medullary rather than cortical exit site. Using the monoclonal antibody MEL-14, we identify a 1%-3% subpopulation of thymocytes that expresses high levels of a receptor molecule involved in lymphocyte homing to peripheral lymph nodes. We present evidence that these rare MEL-14hi thymocytes are predominantly of mature phenotype and represent the major source of thymus emigrants. Surprisingly, MEL-14hi thymocytes are exclusively cortical in location, although their mature phenotype may allow them to masquerade as medullary cells in conventional studies. We also demonstrate that unlike medullary thymocytes, many cortisone-resistant thymocytes (CRT) are MEL-14hi. Thus, in contrast to current dogma, CRT do not represent a sample of medullary thymocytes as they are found in situ and their level of immunocompetence does not necessarily reflect that of the medullary population. Our findings refute the hypothesis that phenotypically and functionally mature cells are restricted to the medulla, and support our proposition that most thymus emigrants are derived from the MEL-14hi cortical subset. 相似文献
18.
R G Butcher 《Histochemistry》1984,81(6):567-572
The reaction velocity of glucose-6-phosphate dehydrogenase has been quantified by continuous monitoring on a Vickers microdensitometer of the reaction product as it formed in sections of different thickness of rat tracheal epithelium. Reaction velocity was directly proportional to section thickness when either tetranitro BT or neotetrazolium was used as the final acceptor; the rate was the same with each tetrazolium salt. However, the amount of formazan deposited in a given time was not proportional to section thickness. When tetranitro BT was employed the reaction became non-linear in the thicker sections due to the inability of the instrument to record beyond a certain absorbance value. Using neotetrazolium a lag phase, due to the failure to overcome the critical supersaturation level of the formazan, preceded the linear response. The duration of this phase decreased as section thickness increased. The implications of these findings on studies using conventional "end point" methods of measurement are discussed. 相似文献
19.
Localization of Acid hydrolases in protoplasts: examination of the proposed lysosomal function of the mature vacuole 下载免费PDF全文
The development of techniques to isolate and purify relatively large quantities of intact vacuoles from mature tissues permits direct biochemical analysis of this ubiquitous mature plant cell organelle. Vacuoles and a fraction enriched in soluble cytoplasmic constituents were quantitatively prepared from Hippeastrum flower petal protoplasts. Vacuolar lysate and soluble cytoplasmic fractions were examined for acid hydrolase activities commonly associated with animal lysosomes, and pH optima were determined. Esterase, protease, carboxypeptidase, β-galactosidase, α-glycosidase and β-glycosidase, not found in the vacuole lysate fraction, were components of the soluble cytoplasmic fraction. Acid phosphatase, RNase and DNase were present in both fractions. Vacuolar enzyme activities were also examined as a function of flower development from bud through senescent stages. The data obtained are not consistent with the concept that the mature plant cell vacuole functions as a generalized lysosome. 相似文献
20.
Recombination inH-1, the major histocompatibility complex (MHC) of the rat, has defined two regions,H-1A andH-1B, which determine antigens apparently homologous to the KJD and Ia antigens of the mouse, respectively. Alloantisera directed at these antigens have been absorbed with kidney homogenates. The results showed that cells in the kidney express serologically detectable MHC antigens determined by both theH-1A andH-1B region. Control absorptions indicated that to account for these results in terms of recirculating lymphocytes, two perfused kidneys would need to contain more than 60 percent of the recirculating lymphocyte pool. It appears likely, therefore, that H-1B antigens are expressed by cells resident in the kidney. 相似文献