全文获取类型
收费全文 | 90892篇 |
免费 | 5422篇 |
国内免费 | 10篇 |
专业分类
96324篇 |
出版年
2023年 | 552篇 |
2021年 | 1107篇 |
2020年 | 983篇 |
2019年 | 999篇 |
2018年 | 2538篇 |
2017年 | 2225篇 |
2016年 | 2912篇 |
2015年 | 3727篇 |
2014年 | 3844篇 |
2013年 | 5245篇 |
2012年 | 6189篇 |
2011年 | 5619篇 |
2010年 | 3591篇 |
2009年 | 2636篇 |
2008年 | 4483篇 |
2007年 | 4233篇 |
2006年 | 4168篇 |
2005年 | 3432篇 |
2004年 | 3478篇 |
2003年 | 3140篇 |
2002年 | 2888篇 |
2001年 | 2322篇 |
2000年 | 2280篇 |
1999年 | 1672篇 |
1998年 | 735篇 |
1997年 | 544篇 |
1996年 | 590篇 |
1995年 | 508篇 |
1994年 | 498篇 |
1992年 | 972篇 |
1991年 | 902篇 |
1990年 | 864篇 |
1989年 | 928篇 |
1988年 | 776篇 |
1987年 | 784篇 |
1986年 | 705篇 |
1985年 | 797篇 |
1984年 | 659篇 |
1983年 | 568篇 |
1979年 | 690篇 |
1978年 | 512篇 |
1977年 | 505篇 |
1975年 | 595篇 |
1974年 | 642篇 |
1973年 | 612篇 |
1972年 | 558篇 |
1971年 | 500篇 |
1970年 | 545篇 |
1969年 | 615篇 |
1968年 | 579篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
The sodium and potassium ion activated adenosinetriphosphatase [(Na+,K+)-ATPase] in membranous preparations from Squalus acanthias has been spin-labeled on sulfhydryl groups after prelabeling with N-ethylmaleimide. Saturation-transfer electron spin resonance spectroscopy has been used to study the rotational motions of the labeled protein on the microsecond time scale. Effective rotational correlation times deduced from the diagnostic line-height ratios in the second-harmonic, 90 degrees out-of-phase (V2') spectra are much larger than those deduced from the spectral integrals, indicating the presence of large-scale segmental motions, in addition to rotation of the protein as a whole. Experiments involving controlled cross-linking of the protein by glutaraldehyde, as well as measurements of the line broadening of the conventional electron spin resonance spectra, support this interpretation. Both the spectral integrals and diagnostic line-height ratios are found to increase irreversibly with time on incubation at temperatures greater than 20 degrees C, corresponding to a decrease in the segmental motion of the protein and probably also in the overall protein rotation. The native enzyme displays a marked nonlinearity in the Arrhenius temperature dependence of the activity at temperatures above 20 degrees C, and the activity decreases with a half-life of ca. 70 min on incubation at 37 degrees C (but not on incubation at low temperature), paralleling the time- and temperature-dependent changes in the saturation-transfer spectra of the labeled protein. Both of these observations suggest that the changes observed in the molecular dynamics could correspond to functional properties of the protein.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
103.
Fabián Michelangeli Dalia M. Sulcas Marie-Christine Ruiz 《Cell and tissue research》1987,250(2):413-419
Summary This study is concerned with electron-microscopic observations on endocrine or paracrine cells in the fundic gastric mucosa of the bullfrog. Also, an attempt was made to identify the histamine-releasing cells involved in the secretagogue response. At least three distinct endocrine-like cell types were found. The classification is based on the appearance of secretory granules and other organelles, and the relationship of endocrine-like cells with other cells in the tissue. The amphibian endocrine-like cells resemble the ECL, D and EC cells of mammals. Type-I (ECL) cells showed degranulation after repeated stimulation with tetragastrin (TG), acetylcholine (ACh) and K+ depolarizing solution, all of which release histamine. 相似文献
104.
105.
106.
107.
108.
109.
110.
Marie Lipoldová Helena Havelková Jana Badalová Jarmila Vojtíšková Lei Quan Magdaléna Krulová Yahya Sohrabi Alphons P. Stassen Peter Demant 《Cancer immunology, immunotherapy : CII》2010,59(2):203-213
Low infiltration of lymphocytes into cancers is associated with poor prognosis, but the reasons why some patients exhibit
a low and others a high infiltration of tumors are unknown. Previously we mapped four loci (Lynf1–Lynf4) controlling lymphocyte infiltration of mouse lung tumors. These loci do not encode any of the molecules that are involved
in traffic of lymphocytes. Here we report a genetic relationship between these loci and the control of production of IFNγ
in allogeneic mixed lymphocyte cultures (MLC). We found that IFNγ production by lymphocytes of O20/A mice is lower than by
lymphocytes of OcB-9/Dem mice (both H2
pz
) stimulated in MLC by irradiated splenocytes of C57BL/10SnPh (H2
b
) or BALB/cHeA (H2
d
) mice, or by ConA. IFNγ production in MLCs of individual (O20 × OcB-9)F2 mice stimulated by irradiated C57BL/10 splenocytes and genotyped for microsatellite markers revealed four IFNγ-controlling
loci (Cypr4-Cypr7), each of which is closely linked with one of the four Lynf loci and with a cluster of susceptibility genes for different tumors. This suggests that inherited differences in certain
lymphocyte responses may modify their propensity to infiltrate tumors and their capacity to affect tumor growth. 相似文献