全文获取类型
收费全文 | 4315篇 |
免费 | 332篇 |
国内免费 | 3篇 |
出版年
2021年 | 63篇 |
2020年 | 29篇 |
2019年 | 34篇 |
2018年 | 51篇 |
2017年 | 46篇 |
2016年 | 87篇 |
2015年 | 123篇 |
2014年 | 145篇 |
2013年 | 222篇 |
2012年 | 283篇 |
2011年 | 271篇 |
2010年 | 198篇 |
2009年 | 210篇 |
2008年 | 258篇 |
2007年 | 263篇 |
2006年 | 227篇 |
2005年 | 245篇 |
2004年 | 259篇 |
2003年 | 222篇 |
2002年 | 193篇 |
2001年 | 58篇 |
2000年 | 38篇 |
1999年 | 53篇 |
1998年 | 64篇 |
1997年 | 63篇 |
1996年 | 40篇 |
1995年 | 37篇 |
1994年 | 34篇 |
1993年 | 45篇 |
1992年 | 45篇 |
1991年 | 47篇 |
1990年 | 32篇 |
1989年 | 27篇 |
1988年 | 34篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 32篇 |
1984年 | 41篇 |
1983年 | 31篇 |
1982年 | 33篇 |
1981年 | 38篇 |
1980年 | 28篇 |
1979年 | 23篇 |
1978年 | 19篇 |
1977年 | 38篇 |
1976年 | 19篇 |
1975年 | 18篇 |
1974年 | 29篇 |
1973年 | 18篇 |
1970年 | 16篇 |
排序方式: 共有4650条查询结果,搜索用时 703 毫秒
141.
Characterization of Clostridia by Gas Chromatography: I. Differentiation of Species by Cellular Fatty Acids 总被引:25,自引:10,他引:15 下载免费PDF全文
Fatty acids of 41 strains representing 13 species of Clostridium were extracted directly from whole cells and examined as methyl esters by gas-liquid chromatography. Both visual and quantitative comparisons of the resulting chromatograms for the presence and relative amounts of large major peaks allowed rapid differentiation of C. perfringens, C. sporogenes, and C. bifermentans from each other and from 10 other species. Each of the three former species possessed a different characteristic fatty acid methyl ester profile that was exhibited by all strains tested within the respective species. Culture age and growth media influenced the relative proportions of certain of the acids, but such differences did not limit species differentiation. 相似文献
142.
Production of Glutaric Acid: a Useful Criterion for Differentiating Pseudomonas diminuta from Pseudomonas vesiculare 总被引:5,自引:0,他引:5 下载免费PDF全文
A gas-liquid chromatographic procedure was used to determine short-chain acids produced by Pseudomonas diminuta and P. vesiculare after growth on Trypticase soy agar. Each of nine strains of P. diminuta produced glutaric acid, whereas none of the strains of P. vesiculare produced this acid. 相似文献
143.
Wayne Rickoll David Rehkopf Catherine Dunn Amy Malmberg Karen VanWinkle-Swift 《Journal of phycology》1998,34(1):147-151
Iodine staining of clones of nitrogen-starved Chlamydomonas cells was used to screen for mutants with altered levels or altered composition of storage starch. Mutations leading to defects in quantity or morphology of starch granules not only can provide information on storage starch biosynthesis and granule assembly but can also be used as morphological markers in genetic and cell biological studies. A mutant of Chlamydomonas monoica Strehlow devoid of starch granules was obtained following ultraviolet mutagenesis. Nitrogen-starved cells of the sta-1 strain lacked pyrenoidal starch granules and granules normally associated with thylakoid membranes. The mutant phenotype was the consequence of a single Mendelian mutation that appeared to affect granule assembly rather than starch biosynthesis per se and that had no effect on vegetative growth, sexual reproduction, or zygospore viability. 相似文献
144.
Wayne W. Deatsch 《The Western journal of medicine》1956,85(3):180-182
A method of treatment of carcinoma of the nasopharynx is described, using a bead of radioactive cobalt in a Foley catheter placed through the nose and inside the nasopharynx. As an aid in proper placement of the cobalt bead a portion of the nasal septum is removed first. This method of treatment is to supplement rather than replace other methods of treatment such as external x-ray therapy and surgical excision of lymph nodes in the neck.Twenty-two patients were treated with radioactive cobalt beads and the results indicated that it is a useful method for treating carcinoma in the nasopharynx. 相似文献
145.
Stephen R. Malone Herman S. Mayeux Hyrum B. Johnson H. Wayne Polley 《American journal of botany》1993,80(12):1413-1418
Stomatal density, stomatal aperture length, area/leaf, and number of stomata/leaf were measured after the annual C3 agronomic grasses oats (Avena sativa) and wheat (Triticum aestivum), the C, woody legume honey mesquite (Prosopis glandulosa), and the perennial C4 grass little bluestem (Schizachyrium scoparium) were grown across a subambient carbon dioxide concentration ([CO2]) gradient from near 200 to 350 μmol/mol in a growth chamber. The purpose was to determine if the size and density of stomata vary in response to atmospheric [CO2] during growth, across a subambient [CO2] range representative of the doubling that has occurred since the last ice age. Changes in stomatal density and aperture length with increasing [CO2] were small when detected. Stomatal density decreased on adaxial flag leaf surfaces of wheat, and aperture length increased slightly with [CO2], Leaf area and number of stomata/flag leaf increased by similar proportions with [CO2] in two wheat cultivars. No consistent relationship between [CO2] and stomatal density or size was detected in mesquite, oats, or little bluestem. We conclude that individual plants of these species lack the plasticity to significantly alter stomatal density and aperture length in response to increasing atmospheric [CO2] in a single generation (annuals) or growing season (perennials). 相似文献
146.
Lindsay D. Plank W.C. Hymeer M.Elaine Kunze Gary M. Marks J.Wayne Lanham Paul Todd 《Journal of biochemical and biophysical methods》1983,8(4):275-289
Growth hormone secreting cells of the rat anterior pituitary are heavily laden with granules of growth hormone and can be partially purified on the basis of their resulting high density. Two methods of preparative cell electrophoresis were investigated as methods of enhancing the purification of growth hormone producing cells: density gradient electrophoresis and continuous flows electrophoresis. Both methods provided a two- to four-fold enrichment in growth hormone production per cell relative to that achieved by previous methods. Measurements of electrophoretic mobilities by two analytical methods, microscopic electrophoresis and laser-tracking electrophoresis, revealed very little distinction between unpurified anterior pituitary cell suspensions and somatotroph-enriched cell suspensions. Predictions calculated on the basis of analytical electrophoretic data are consistent with the hypothesis that sedimentation plays a significant role in both types of preparative electrophoresis and the electrophoretic mobility of the growth hormone secreting subpopulation of cells remains unknown. 相似文献
147.
Joseph Tibbs Mohamed Ghoneim Colleen C Caldwell Troy Buzynski Wayne Bowie Elizabeth
M Boehm M
Todd Washington S
M
Ali Tabei Maria Spies 《Nucleic acids research》2021,49(9):e53
Molecular machines within cells dynamically assemble, disassemble and reorganize. Molecular interactions between their components can be observed at the single-molecule level and quantified using colocalization single-molecule spectroscopy, in which individual labeled molecules are seen transiently associating with a surface-tethered partner, or other total internal reflection fluorescence microscopy approaches in which the interactions elicit changes in fluorescence in the labeled surface-tethered partner. When multiple interacting partners can form ternary, quaternary and higher order complexes, the types of spatial and temporal organization of these complexes can be deduced from the order of appearance and reorganization of the components. Time evolution of complex architectures can be followed by changes in the fluorescence behavior in multiple channels. Here, we describe the kinetic event resolving algorithm (KERA), a software tool for organizing and sorting the discretized fluorescent trajectories from a range of single-molecule experiments. KERA organizes the data in groups by transition patterns, and displays exhaustive dwell time data for each interaction sequence. Enumerating and quantifying sequences of molecular interactions provides important information regarding the underlying mechanism of the assembly, dynamics and architecture of the macromolecular complexes. We demonstrate KERA’s utility by analyzing conformational dynamics of two DNA binding proteins: replication protein A and xeroderma pigmentosum complementation group D helicase. 相似文献
148.
Khanh B. Tran Gregory Gimenez Peter Tsai Sharada Kolekar Euan J. Rodger Aniruddha Chatterjee Anower Jabed Jen‐Hsing Shih Wayne R. Joseph Elaine S. Marshall Qian Wang Cristin G. Print Michael R. Eccles Bruce C. Baguley Peter R. Shepherd 《Pigment cell & melanoma research》2021,34(1):136-143
Melanoma is a disease associated with a very high mutation burden and thus the possibility of a diverse range of oncogenic mechanisms that allow it to evade therapeutic interventions and the immune system. Here, we describe the characterization of a panel of 102 cell lines from metastatic melanomas (the NZM lines), including using whole‐exome and RNA sequencing to analyse genetic variants and gene expression changes in a subset of this panel. Lines possessing all major melanoma genotypes were identified, and hierarchical clustering of gene expression profiles revealed four broad subgroups of cell lines. Immunogenotyping identified a range of HLA haplotypes as well as expression of neoantigens and cancer–testis antigens in the lines. Together, these characteristics make the NZM panel a valuable resource for cell‐based, immunological and xenograft studies to better understand the diversity of melanoma biology and the responses of melanoma to therapeutic interventions. 相似文献
149.
Reavis Zackery W. Mirjankar Nikhil Sarangi Srikant Boyle Stephen H. Kuhn Cynthia M. Matson Wayne R. Babyak Michael A. Matson Samantha A. Siegler Ilene C. Kaddurah‑Daouk Rima Suarez Edward C. Williams Redford B. Grichnik Katherine Stafford‑Smith Mark Georgiades Anastasia 《Metabolomics : Official journal of the Metabolomic Society》2021,17(6):1-13
Metabolomics - Metabolomics applications to the aquaculture research are increasing steadily. The use of standardized proton nuclear magnetic resonance (1H NMR) spectroscopy can provide the... 相似文献
150.