全文获取类型
收费全文 | 2234篇 |
免费 | 326篇 |
出版年
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 21篇 |
2018年 | 22篇 |
2016年 | 45篇 |
2015年 | 53篇 |
2014年 | 61篇 |
2013年 | 73篇 |
2012年 | 112篇 |
2011年 | 85篇 |
2010年 | 60篇 |
2009年 | 50篇 |
2008年 | 93篇 |
2007年 | 93篇 |
2006年 | 86篇 |
2005年 | 84篇 |
2004年 | 88篇 |
2003年 | 92篇 |
2002年 | 70篇 |
2001年 | 89篇 |
2000年 | 68篇 |
1999年 | 69篇 |
1998年 | 31篇 |
1997年 | 35篇 |
1996年 | 31篇 |
1995年 | 23篇 |
1994年 | 21篇 |
1992年 | 51篇 |
1991年 | 46篇 |
1990年 | 50篇 |
1989年 | 51篇 |
1988年 | 52篇 |
1987年 | 40篇 |
1986年 | 36篇 |
1985年 | 45篇 |
1984年 | 24篇 |
1983年 | 31篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1980年 | 35篇 |
1979年 | 35篇 |
1978年 | 21篇 |
1977年 | 24篇 |
1976年 | 28篇 |
1974年 | 22篇 |
1973年 | 17篇 |
1972年 | 27篇 |
1971年 | 30篇 |
1970年 | 24篇 |
1969年 | 25篇 |
排序方式: 共有2560条查询结果,搜索用时 15 毫秒
91.
Eftihia Cayanis A. B. Lane T. Jenkins G. T. Nurse Doris Balinsky 《Biochemical genetics》1977,15(7-8):765-773
A new variant of the red cell enzyme glucose-6-phosphate dehydrogenase has been detected in a South African male of Indian descent and in several of his relatives. The enzyme variant is characterized by slow electrophoretic mobility, low Michaelis constants for the substrates glucose-6-phosphate and NADP, and increased utilization of the substrate analogues 2-deoxyglucose-6-phosphate and deamino-NADP relative to the normal (B+) enzyme. There is no evidence that the enzyme variant, for which the name G6PD Porbandar is suggested, is associated with any hematological abnormality.The Atomic Energy Board and the South African Medical Research Council provided support for part of this work. 相似文献
92.
John R. Porter Michael F. Allen Leslie C. Lane Michael G. Boosalis 《Plant and Soil》1982,68(2):283-287
Summary A chlorotic condition of soybeans in the river valleys of eastern Nebraska was studied. The pattern of chlorosis, presence
of petiolar necrosis, reductions in rhizobial and mycorrhizal infection, and plant and soil chemical analyses suggest that
the condition is more complex than normal iron deficiency chlorosis or other mineral deficiencies or toxicities. Nodulation
is almost totally inhibited in affected plants. Mycorrhizal fungi, while able to infect early in the season, do not persist
on affected plants. Breakdown of endodermis was observed in the roots of affected plants. The factors contributing to this
condition have not yet been determined.
Published with the approval of the director as Paper No. 5672, Journal Series, Nebraska Agricultural Experiment Station. 相似文献
93.
Effects of SV40 transformation on the cytoskeleton and behavioural properties of human keratinocytes 总被引:14,自引:0,他引:14
J Taylor-Papadimitriou P Purkis E B Lane I A McKay S E Chang 《Cell differentiation》1982,11(3):169-180
A cloned cell line (SVK14) with apparently unlimited growth potential was isolated from simian virus 40 (SV40)-infected human foreskin keratinocytes which did not appear to pass through any obvious 'crisis' (Girardi et al., J. Cell. Comp. Physiol., 1965, 65, 69-84). Indirect immunofluorescence microscopy showed that the transformed cells have the SV40 large T antigen in their nuclei and stain positively with LE61, a monoclonal antibody that reacts with a tonofilament determinant normally only found in non-keratinizing simple epithelia. SVK14 cells can be grown in the absence of 3T3 feeders and show an impaired ability to differentiate into squames, and this impairment becomes more marked with passage. At later passages the cells acquire the ability to form colonies in agar and to produce a factor with mitogenic activity which stimulates DNA synthesis in quiescent 3T3 cells. Concomitantly, the SVK14 cells become less sensitive to the growth inhibitory effect of human alpha interferons. 相似文献
94.
C3H mice were infected subcutaneously with 105 promastigotes of Leishmania mexicana and subsequent lesions were examined at 3, 5, and 8 months. All animals developed persistent nonulcerating nodules of variable size which did not metastasize. The nodules contained amastigotes with a mononuclear infiltrate of histiocytes, lymphocytes, and plasma cells, but without formation of tuberculoid-type granulomas. Neutrophils and eosinophils were also encountered in some cases. Specific antileishmanial antibodies and delayed-type hypersensitivity to leishmanial antigen were present at 3, 5, and 8 months postinfection. L. mexicana infection in C3H mice differs from classic self-healing cutaneous leishmaniasis by the pesistence of nonhealing, nonulcerating, nonmetastasizing lesions, despite evidence of cellular and humoral immunity. 相似文献
95.
H. C. Lane 《Journal of fish biology》1979,15(4):425-436
Rainbow trout of the Kamploops variety were sampled at intervals from October to the end of March. During this period a decline was noted in red cell count, haematocrit, haemoglobin concentration and plasma osmotic concentration. Increases were seen, however, in mean cellular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration and the water content of liver and dorsal muscle. Sexual differences were found in all values with the exception of mean corpuscular haemoglobin concentration and the water content of both tissues. Males always had higher values in those parameters in which sexual differences were noted. All trends, with the exception of male haemoglobin and mean cellular volume and female mean cellular volume and osmotic concentration, were significantly linear.
None of the findings in this study could be correlated with temperature or photoperiod. Neither could the declining plasma osmotic concentration be correlated with the rising mean cellular volume or tissue water content. However, correlations were noted between haemoglobin and haematocrit, red cell count and haematocrit and between osmotic concentration and haematocrit. A negative correlation was seen between mean corpuscular haemoglobin concentration and mean cellular volume. 相似文献
None of the findings in this study could be correlated with temperature or photoperiod. Neither could the declining plasma osmotic concentration be correlated with the rising mean cellular volume or tissue water content. However, correlations were noted between haemoglobin and haematocrit, red cell count and haematocrit and between osmotic concentration and haematocrit. A negative correlation was seen between mean corpuscular haemoglobin concentration and mean cellular volume. 相似文献
96.
Gel electrophoresis of DNA from 95 clinical isolates of Shigella sonnei and Shigella flexneri resistant to antibiotics revealed a heterogeneous plasmid population. Most of the plasmids were smaller than 6 megadaltons (Mdal). Six S. sonnei isolates with the most common antibiotic resistance pattern were characterized. They had two plasmids in common: one was a self-transmissible Fi+ plasmid of 46 Mdal encoding resistance to streptomycin and sulphafurazole. In addition, several cryptic plasmids ranging in size from 1.0 to 24.5 Mdal were present. Mobilization of the 5.5 Mdal SuSm plasmid and a 1.0 Mdal cryptic plasmid was demonstrated with all six S. sonnei isolates during conjugation. This mobilization was mediated by the 46 Mdal self-transmissible Fi+ R plasmid and also by a 24.5 Mdal Fi- plasmid carrying no known drug resistance determinants. 相似文献
97.
D. Lane M. Chandler L. Silver A. Bruschi L. Caro 《Molecular & general genetics : MGG》1979,168(3):337-340
Summary We have cloned the entire r-determinant of the antibiotic resistance plasmid R100.1 on the plasmid vectors pCR1 and pSC201. We find that the hybrid plasmids segregate from cultures in which replication of the vector is blocked. This suggests that the r-det is not capable of autonomous replication. 相似文献
98.
Summary The structure of Merkel cells occurring in the epidermis of adult and larval stages of Lampetra spp. is described; it is comparable to that reported from the gnathostome classes. The cells bear microvilli, grouped on the distal and proximal aspects, and are associated with sparsely branching and varicose nerve fibres. One branch of the neurite bears a spur-like process which indents the proximal side of the Merkel cell. Most of the specific Merkel granules are situated in the vicinity of this neurite projection; the cell membrane adjacent to the tip of the spur process bears structures resembling presynaptic densities. Occasionally, desmosome-like junctions are found between the neurite and the Merkel cell.The authors thank the Fresh Water Biological Association and the Department of Biological Sciences, University of Bath, for supplying the material, Dr. H. Fox for giving some prepared blocks of Lampetra planeri adults, Mr. B.L. Pirie for technical assistance, and the Science Research Council for support through grant GR/A/3740.6 相似文献
99.
A non-Jewish family is presented in which the genes for Tay-Sachs disease and Sandhoff disease are segregating. Individuals heterozygous for both alleles have low serum and white cell total hexosaminidase levels together with a proportion of heat-labile hexosaminidase A (HEX A) which falls in the normal range. The individuals would not be detected as carriers of Tay-Sachs disease or Sandhoff disease in a population screening program. 相似文献
100.