全文获取类型
收费全文 | 7424篇 |
免费 | 743篇 |
国内免费 | 1篇 |
出版年
2021年 | 91篇 |
2020年 | 87篇 |
2019年 | 80篇 |
2018年 | 117篇 |
2017年 | 89篇 |
2016年 | 128篇 |
2015年 | 229篇 |
2014年 | 244篇 |
2013年 | 393篇 |
2012年 | 408篇 |
2011年 | 417篇 |
2010年 | 270篇 |
2009年 | 238篇 |
2008年 | 310篇 |
2007年 | 338篇 |
2006年 | 346篇 |
2005年 | 302篇 |
2004年 | 296篇 |
2003年 | 299篇 |
2002年 | 301篇 |
2001年 | 112篇 |
2000年 | 115篇 |
1999年 | 135篇 |
1998年 | 107篇 |
1997年 | 73篇 |
1996年 | 81篇 |
1995年 | 86篇 |
1994年 | 76篇 |
1993年 | 76篇 |
1992年 | 98篇 |
1991年 | 81篇 |
1990年 | 99篇 |
1989年 | 85篇 |
1988年 | 82篇 |
1987年 | 82篇 |
1986年 | 84篇 |
1985年 | 103篇 |
1984年 | 100篇 |
1983年 | 70篇 |
1982年 | 92篇 |
1981年 | 74篇 |
1980年 | 83篇 |
1979年 | 73篇 |
1978年 | 80篇 |
1977年 | 65篇 |
1976年 | 59篇 |
1975年 | 58篇 |
1974年 | 54篇 |
1973年 | 59篇 |
1970年 | 41篇 |
排序方式: 共有8168条查询结果,搜索用时 15 毫秒
51.
52.
A general method is described for the assay of glycosyltransferase activity, which makes use of synthetic glycoside acceptors attached to hydrophobic aglycones. The products formed by incubation of an enzyme with acceptor and radiolabelled sugarnucleotide can then be rapidly (one minute) separated from interfering radioactivity by adsorption on to reverse-phase C-18 cartridges. After aqueous washing, products are easily isolated by elution with methanol. The utility of the method for the assay of (1–4)galactosyltransferase, (1–2)fucosyltransferase andN-acetylglucosaminyltransferase I and V is demonstrated. 相似文献
53.
William J. Kraemer Lawrence E. Armstrong Roger W. Hubbard Louis J. Marchitelli Natalie Leva Paul B. Rock Joseph E. Dziados 《European journal of applied physiology and occupational physiology》1988,57(4):399-403
No data exists regarding responses of human atrial natriuretic factor (ANF) to exercise in the heat. The purpose of this study was to examine the responses of plasma ANF to high intensity submaximal (71% +/- 0.9 VO2max) exercise in the heat over an eight day acclimation period. Fourteen healthy males volunteered to participate in the study. Subjects performed intermittent exercises on a treadmill (0% grade) during 50 min of each 100 min trial in an environmental chamber maintained at 41.2 +/- 0.5 degrees C, 39.0 +/- 1.7% relative humidity. Blood was obtained from an antecubital vein after standing 20 min in the heat prior to exercise, and immediately after exercise. Measures were compared on days 1, 4 and 8. ANF did not change pre- to post-exercise nor did it change over the eight day heat acclimation period despite other heat acclimation adaptations. Conversely, plasma aldosterone (ALDO), renin activity (PRA) and cortisol (COR) all increased (p less than 0.05) pre- to post-exercise on each day but again no changes were observed over the eight day period. These data support that ANF may not increase when ALDO and PRA increases are observed. 相似文献
54.
Tenascin interferes with fibronectin action 总被引:54,自引:0,他引:54
Primary chick embryo fibroblasts attach to a tenascin substrate, but remain rounded and do not spread out. The proportion between tenascin and fibronectin in mixtures used to coat the substrate determines the shape of the cells. Tenascin inhibits integrin-mediated chick fibroblast attachment to fibronectin, laminin, and the GRGDS peptide. Rat fibroblast attachment to fibronectin, but not to laminin, is inhibited by tenascin. A monoclonal antibody against tenascin, as well as its Fab fragments, is able to neutralize the inhibitory activity on cell attachment and is therefore assumed to mask the cell-binding site of tenascin. On electron micrographs showing this monoclonal antibody bound to tenascin, its epitope can be localized to the terminal knob at the distal ends of the tenascin arms. 相似文献
55.
Studies on the Tissue Distribution of the Puromycin-Sensitive Enkephalin-Degrading Aminopeptidases 总被引:3,自引:0,他引:3
Stacey McLellan Simon H. Dyer Gerry Rodriguez Louis B. Hersh 《Journal of neurochemistry》1988,51(5):1552-1559
An antiserum generated to the soluble form of the rat brain puromycin-sensitive enkephalin-degrading aminopeptidase was used to determine the tissue distribution of the soluble and membrane-associated forms of this enzyme. All tissues examined contained significant levels of the soluble enzyme form, with this enzyme accounting for greater than 90% of the arylamidase activity in brain, heart, and skeletal muscle. Native gel electrophoresis coupled with activity staining as well as inhibition studies were used to confirm the presence of this enzyme in various tissues. Serum was found not to contain this particular aminopeptidase. In contrast to the results obtained with the soluble enzyme form, brain was the only tissue found to contain the membrane-associated enzyme form. Although all tissues contained membrane-associated aminopeptidase activity only the brain enzyme could be maintained in solution in the absence of detergent. In addition, the brain membrane-associated enzyme could be distinguished from the membrane-associated aminopeptidase activity in other tissues on the basis of its sensitivity to inhibition by puromycin. 相似文献
56.
J Nakagawa D von der Ahe D Pearson B A Hemmings S Shibahara Y Nagamine 《The Journal of biological chemistry》1988,263(5):2460-2468
57.
58.
59.
Influence of maize root mucilage on soil aggregate stability 总被引:9,自引:0,他引:9
This study was undertaken to determine the effects of root exudates on soil aggregate stability. Root mucilage was collected
from two-month old maize plants (Zea mays L.) Mucilage and glucose solutions were added at a rate of 2.45 g C kg−1 dry soil to silty clay and silt loam soils. Amended soils, placed in serum flasks, were incubated for 42 d with a drying-wetting
cycle after 21 d. Evolved CO2 was measured periodically as well as the water-stable aggregates and soluble sugar and polysaccharide content of the soil.
In mucilage-amended soils CO2 evolution started with a lag phase of 2–3 days, which was not observed in glucose-amended soils. There was then a sharp increase
in evolved CO2 up to day 7. During the second incubation period there were only small differences in evolved C between treatments. Incorporation
of mucilage in both soils resulted in a spectacular and immediate increase in soil aggregate stability. Thereafter, the percent
of water-stable aggregates quickly decreased parallel to microbial degradation. On completion of the incubation, aggregate
stability in the silty clay soil was still significantly higher in the presence of mucilage than in the control. This work
supports the assumption that freshly released mucilage is able to stick very rapidly to soil particles and may protect the
newly formed aggregates against water destruction. On the silty clay, microbial activity contributes to a stabilization of
these established organo-mineral bounds. 相似文献
60.
Acree JA Echternkamp SE Kappes SM Luedke AJ Holbrook FR Pearson JE Ross GS 《Theriogenology》1991,36(4):689-697
Sixty heifers were infected with bluetongue virus (BTV) by the bites of the vector and by inoculation with insect origin virus. During the acute and convalescent stages of the infection, embryos were collected nonsurgically from these animals and washed according to the recommendations of the International Embryo Transfer Society (1). No BTV was isolated from 77 of these embryos when they were inoculated onto cell culture and into embryonating chicken eggs. There was no evidence of lateral BTV transmission when 231 of these embryos were transferred into susceptible recipients, nor was there evidence of vertical BTV transmission to the 88 calves resulting from these transfers. Another six donors that were assumed to have recovered from a natural infection of BTV, were added to the study to increase the probability of obtaining embryos from a persistently infected BTV carrier. However, it was determined later that these animals had not been infected with BTV but with the closely-related epizootic hemorrhagic disease virus (EHDV). Embryos were collected from these donors and washed as above. Neither BTV nor EHDV was isolated from 26 of these embryos by the inoculation of cell culture and embryonating chicken eggs. There was no evidence of lateral BTV or EHDV transmission to recipients of 15 of these embryos or of vertical BTV or EHDV transmission to the resulting 7 calves. However, two recipients of embryos from one of these donors developed antibodies to BTV 6 to 9 months after transfer. Passive antibodies to BTV were also detected in their calves. There is good evidence that these two recipients acquired BTV from natural exposure to infected insect vectors and not from the transferred embryos. 相似文献