全文获取类型
收费全文 | 5850篇 |
免费 | 700篇 |
国内免费 | 7篇 |
专业分类
6557篇 |
出版年
2021年 | 54篇 |
2018年 | 54篇 |
2016年 | 95篇 |
2015年 | 121篇 |
2014年 | 140篇 |
2013年 | 192篇 |
2012年 | 247篇 |
2011年 | 191篇 |
2010年 | 146篇 |
2009年 | 144篇 |
2008年 | 204篇 |
2007年 | 207篇 |
2006年 | 215篇 |
2005年 | 192篇 |
2004年 | 192篇 |
2003年 | 182篇 |
2002年 | 186篇 |
2001年 | 200篇 |
2000年 | 194篇 |
1999年 | 165篇 |
1998年 | 84篇 |
1997年 | 108篇 |
1996年 | 103篇 |
1995年 | 87篇 |
1994年 | 89篇 |
1993年 | 90篇 |
1992年 | 118篇 |
1991年 | 113篇 |
1990年 | 145篇 |
1989年 | 123篇 |
1988年 | 104篇 |
1987年 | 114篇 |
1986年 | 97篇 |
1985年 | 123篇 |
1984年 | 90篇 |
1983年 | 72篇 |
1982年 | 81篇 |
1981年 | 69篇 |
1980年 | 76篇 |
1979年 | 86篇 |
1978年 | 73篇 |
1977年 | 64篇 |
1976年 | 77篇 |
1975年 | 70篇 |
1974年 | 73篇 |
1973年 | 73篇 |
1972年 | 76篇 |
1971年 | 63篇 |
1969年 | 47篇 |
1968年 | 51篇 |
排序方式: 共有6557条查询结果,搜索用时 15 毫秒
161.
Marie E. Portuallo David Y. Lu Gretchen M. Alicea Joel Bolling Rebecca Lee Jennifer McQuade Allison Betof Warner Michael Davies Ashani Weeraratna Jessie Villanueva Vito W. Rebecca 《Pigment cell & melanoma research》2023,36(5):441-447
The inaugural Diversity and Inclusion in Science Session was held during the 2021 Society for Melanoma Research (SMR) congress. The goal of the session was to discuss diversity, equity, and inclusion in the melanoma research community and strategies to promote the advancement of underrepresented melanoma researchers. An international survey was conducted to assess the diversity, equity, and inclusion (DEI) climate among researchers and clinicians within the Society for Melanoma Research (SMR). The findings suggest there are feelings and experiences of inequity, bias, and harassment within the melanoma community that correlate with one's gender, ethnic/racial group, and/or geographic location. Notably, significant reports of inequity in opportunity, discrimination, and sexual harassment demonstrate there is much work remaining to ensure all scientists in our community experience an academic workplace culture built on mutual respect, fair access, inclusion, and equitable opportunity. 相似文献
162.
Molecular weight markers which are detectable using labeled antispecies antibodies or labeled Protein A have been prepared for use as standards on protein blots. The standards were prepared by the controlled reduction followed by subsequent alkylation of gamma globulin. Separate sets of standards were prepared using gamma globulins derived from human, mouse, rabbit, and sheep species. Standards were also prepared using monoclonal-derived gamma globulins from human myeloma fluid and mouse ascites fluid. Standards produced from monoclonal-derived gamma globulins produced very sharp bands on sodium dodecyl sulfate-polyacrylamide gels and proved to be excellent standards for this technique alone. However, the markers were uniquely suitable for use as standards in protein blotting procedures because their detection was achieved by the procedure used to detect the transferred antigen(s). The detection of immunoglobulin G (IgG)-derived standards on protein blots from all the species listed above was demonstrated using appropriate horseradish peroxidase (HRP)-conjugated antispecies antibodies. The use of other detection systems (biotin-labeled antibody and subsequent detection with HRP-steptavidin, HRP-Protein A) was also validated with human IgG-derived standards. Furthermore, the standards were shown to be suitable for use on both nitrocellulose and cationized nylon-based supports and could be used when adjacent samples were run under reducing conditions. Hence the gamma globulin-derived standards serve as both a control to check the adequacy of transfer and immunodetection systems and as markers which enable the molecular weights of detected antigens to be calculated. 相似文献
163.
164.
OBJECTIVE: To describe survival, disability, and morbidity after radiotherapy for malignant glioma. DESIGN: Two year prospective study with home interviews with patients and relatives. SETTING: Seven neurosurgical and radiotherapy centres in London. SUBJECTS: 105 patients aged 21 to 75: 59 had biopsy; 46 had partial macroscopic resection; 92 received radiotherapy; and 13 received steroids alone. MAIN OUTCOME MEASURES: Survival, time free from disability, and changes in disability after treatment. RESULTS: Six and 12 month survival for radiotherapy patients was 70% and 39%, respectively. Age, World Health Organisation clinical performance status, extent of surgery, and history of seizures before diagnosis each influenced survival. The Medical Research Council prognostic index was also significantly related to survival. Multivariate analysis showed that initial clinical performance status was the most important component of the index. Most (80%; 49/61) patients with a clinical performance status of 0, 1, or 2 lived at least six months before becoming permanently disabled. Most patients who had initially had a good clinical performance status (0-2) and who were alive six months after radiotherapy (68%; 36/52), however, had experienced either clinical deterioration or severe tiredness after treatment. In 17% (9/52) of these some permanent loss of function remained. These adverse effects were associated with increasing radiotherapy dose. Severely disabled patients (clinical performance status 3 or 4) gained little benefit. CONCLUSION: Severely disabled patients gain little physical benefit from radiotherapy, whereas those not so disabled may experience considerable adverse effects. 相似文献
165.
166.
Alteration of tobacco floral organ identity by expression of combinations of Antirrhinum MADS-box genes 总被引:4,自引:3,他引:1
Brendan Davies Alexandra Di Rosa Tinka Eneva Heinz Saedler Hans Sommer 《The Plant journal : for cell and molecular biology》1996,10(4):663-677
Floral organ identity is largely controlled by the spatially restricted expression of several MADS-box genes. In Antirrhinum majus these organ identity genes include DEF, GLO and PLE . Single and double mutant analyses indicated that the type of organ found in a particular whorl is dependent on which combination of these genes is expressed there. This paper reports the ectopic expression of Antirrhinum organ identity genes, alone and in combinations, in transgenic tobacco. Although the phenotypes are broadly in agreement with the genetic predictions, several unexpected features are observed which provide information concerning the action of the organ identity genes. The presumed tobacco homologue of DEF, NTDEF , has been isolated and used to investigate the influence of ectopic expression of the Antirrhinum organ identity genes on the endogenous tobacco genes. Analysis of the spatial and temporal expression patterns of NTDEF and NTGLO reveals that the boundaries are not coincident and that differences exist in the regulatory mechanisms of the two genes concerning both induction and maintenance of gene expression. Evidence is provided which indicates that organ development is sensitive to the relative levels of organ identity gene expression. Expression of the organ identity genes outside the flower or inflorescence produced no effects, suggesting that additional factors are required to mediate their activity. These results demonstrate that heterologous genes can be used to predictably influence floral organ identity but also reveal the existence of unsuspected control mechanisms. 相似文献
167.
A simple technic is described to produce well spread gymnosperm chromosomes. Root tip meristems are digested with a pectinase:cellulase mixture to produce a cell suspension which then is squashed to yield flat, well spread chromosome complements that can be stained or used for in situ hybridization. 相似文献
168.
169.
The nucleotide sequence of a cDNA prepared from poly(A)+ RNA from Lycopersicon esculentum fruit codes for a protein, M
r 20812, with features representative of the protein core of arabinogalactan proteins. The deduced amino acid sequence resembles that of peptides of arabinogalactan proteins isolated from carrot and rose and is most similar to the sequence of tryptic peptides from Lolium multiflorum (Gleeson et al., Biochem J 264 (1989) 857–862). The similar sequences include a number of Ala-Pro repeats, a feature considered distinctive of arabinogalactan proteins. The amino acid composition is similar to that of the peptide core of the Lolium multiflorum arabinogalactan protein; alanine, serine and proline account for 57% of the polypeptide. The mRNA corresponding to the cDNA sequence was detected in roots, leaves and fruit. The levels of mRNA are reduced in older leaves, in fruit that have commenced ripening and in leaves and fruit that have been wounded. 相似文献
170.
Rapid changes in oxidative metabolism as a consequence of elicitor treatment of suspension-cultured cells of French bean (Phaseolus vulgaris L.) 总被引:1,自引:0,他引:1
Duncan Robertson Dewi R. Davies Chris Gerrish Steven C. Jupe G. Paul Bolwell 《Plant molecular biology》1995,27(1):59-67
Stressed plant cells often show increased oxygen uptake which can manifest itself in the transient production of active oxygen species, the oxidative burst. There is a lack of information on the redox status of cells during the early stages of biotic stress. In this paper we measure oxygen uptake and the levels of redox intermediates NAD/NADH and ATP and show the transient induction of the marker enzyme for redox stress, alcohol dehydrogenase. Rapid changes in the redox potential of elicitor-treated suspension cultures of French bean cells indicate that, paradoxically, during the period of maximum oxygen uptake the levels of ATP and the NADH/NAD ratio fall in a way that indicates the occurrence of stress in oxidative metabolism. This period coincides with the maximum production of active oxygen species particularly H2O2. The cells recover and start producing ATP immediately upon the cessation of H2O2 production. This indicates that the increased O2 uptake is primarily incorporated into active O2 species. A second consequence of these changes is probably a transient compromising of the respiratory status of the cells as indicated in expression of alcohol dehydrogenase. Elicitor-induced bean ADH was purified to homogeneity and the Mr 40 000 polypeptide was subjected to amino acid sequencing. 15% of the whole protein was sequenced from three peptides and was found to have nearly 100% sequence similarity to the amino acid sequence for pea ADH1 (PSADH1). The cDNA coding for the pea enzyme was used to demonstrate the transient induction of ADH mRNA in elicitor-treated bean cells. Enzyme activity levels also increased transiently subsequently. Increased oxygen uptake has previously been thought to be associated with provision of energy for the changes in biosynthesis that occur rapidly after perception of the stress signal. However the present work shows that this rapid increase in oxygen uptake as a consequence of elicitor action is not wholly associated with respiration. 相似文献