全文获取类型
收费全文 | 7743篇 |
免费 | 485篇 |
国内免费 | 310篇 |
专业分类
8538篇 |
出版年
2024年 | 19篇 |
2023年 | 100篇 |
2022年 | 149篇 |
2021年 | 204篇 |
2020年 | 231篇 |
2019年 | 355篇 |
2018年 | 311篇 |
2017年 | 195篇 |
2016年 | 199篇 |
2015年 | 222篇 |
2014年 | 475篇 |
2013年 | 620篇 |
2012年 | 329篇 |
2011年 | 483篇 |
2010年 | 314篇 |
2009年 | 300篇 |
2008年 | 333篇 |
2007年 | 384篇 |
2006年 | 340篇 |
2005年 | 298篇 |
2004年 | 261篇 |
2003年 | 243篇 |
2002年 | 198篇 |
2001年 | 142篇 |
2000年 | 106篇 |
1999年 | 146篇 |
1998年 | 104篇 |
1997年 | 121篇 |
1996年 | 116篇 |
1995年 | 87篇 |
1994年 | 83篇 |
1993年 | 65篇 |
1992年 | 73篇 |
1991年 | 77篇 |
1990年 | 76篇 |
1989年 | 64篇 |
1988年 | 62篇 |
1987年 | 66篇 |
1986年 | 61篇 |
1985年 | 68篇 |
1984年 | 84篇 |
1983年 | 63篇 |
1982年 | 84篇 |
1981年 | 47篇 |
1980年 | 51篇 |
1979年 | 42篇 |
1978年 | 19篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1972年 | 10篇 |
排序方式: 共有8538条查询结果,搜索用时 15 毫秒
81.
Seedlings of eleven varieties of barley (Hordeum vulgare L.) showed differences in utilization of K+ from a full nutrient solution containing 3.0 mM K+. The K+ content of both roots and shoots was proportional to the fresh weights and dry weights after a week in the nutrient solution. The K+ use-efficiency ratio, which indicates the efficiency of nutrient utilization (mg dry weight produced per mg K+ absorbed), differed significantly among the varieties. There was no correlation between influx of Rb+ and the content of K+. It is suggested that there are wide varietal differences in such genetically-determined properties as ion influx and efflux and net ion transport to the shoot. Further-more, the influx of Rb+ was closely linked to transpiration, probably due to a variety-specific non-metabolic part of Rb+ influx. Varietal differences in influx of Rb+ were more pronounced in high-K+ roots than in low-K+ roots with maximum rate of Rb+ uptake, but the rank of varieties was the same in each case. – Criteria for the selection of K+ use-efficient varieties of barley are discussed. 相似文献
82.
Treatment of rats with pyrazole elevated the hepatic microsomal dimethylnitrosamine demethylase activity (DMNd) by several fold. Methylethylnitrosamine demethylase activity was also increased by pyrazole, but some classical monooxygenase activities were not induced. The treatment induced a new protein species which has an apparent molecular weight of 52,000 dal and is believed to be a cytochrome P-450 isozyme. The involvement of a hemoprotein in the pyrazole-induced DMNd was demonstrated in an experiment with CoCl2 which decreased both the microsomal cytochrome P-450 content and DMNd. The induced enzyme with a single Km value of 0.061 mM and Vmax of 12.1 nmol/min/mg is probably the most efficient enzyme known to metabolize nitrosamines. NADPH-cytochrome P-450 reductase was also demonstrated to be an essential component enzyme of the DMNd. These results further substantiate the idea that the P-450-containing monooxygenase is responsible for the metabolism of dimethylnitrosamine in both the control and pyrazole induced microsomes. 相似文献
83.
Hormonal requirements for the induction of cytochrome P-450 in hepatocytes cultured in a serum-free medium 总被引:11,自引:0,他引:11
J F Sinclair P R Sinclair H L Bonkowsky 《Biochemical and biophysical research communications》1979,86(3):710-717
Drug mediated induction of cytochrome P450 was studied in cultures of hepatocytes that had never been cultured in the presence of serum. Propylisopropylacetamide induced a five-fold increase in cytochrome P450, approximating induced levels, when triiodothyronine and/or dexamethasone were included in the culture medium. Insulin was apparently not required for this induction. Cytochrome P450, free of cytochrome oxidase, could be fully recovered from cell homogenates in a 8700g supernatant, by use of a buffer containing 0.2% Emulgen. 相似文献
84.
85.
George Christou C. David Garner Richard M. Miller 《Journal of inorganic biochemistry》1979,11(4):349-353
[NEt4]3[Fe6M2S8(SEt)9] (M = Mo or W) compounds are isomorphous and contain molybdenum and tungsten atoms in an essentially identical environment. These complexes undergo an irreversible one-electron oxidation at −0.46 V (Mo) and −0.51 V (W) and two one-electron reductions at −1.56 and −1.76 V (Mo) and −1.52 and −1.84 V (W), in DMSO solution versus
(0.1 M). The only distinction between the behavior of these molybdenum and tungsten complexes identified thus far is that, for the former the reductions are reversible whereas for the latter they are irreversible. This difference may be relevant to the low activity found for nitrogenases reconstituted with tungsten in place of molybdenum. 相似文献
86.
T-cell responsiveness was measured by the DNA response of disassociated spleen and lymph node cells when exposed to antigen in vitro. Sensitized splenic lymphocytes from fibrosarcoma-bearing mice immunized with 2,4-dinitro-1,5-difluorobenzene (DN2FB) demonstrated a progressive decrease in T-cell responsiveness to the haptenprotein conjugate DNP-BSA. Hyporesponsiveness to the dinitrophenylated-protein conjugate appeared in the spleens but not lymph nodes of tumorous animals. Normal host lymph node cells (LNC) responded strongly 24 to 48 h after sensitization and subsequently declined with a corresponding increase in responsiveness in the spleen. Tumor-bearing hosts (TBH) had similar LNC kinetics during immunization, however, spleen cells were significantly suppressed when compared to normal BALB/c mice sensitization kinetics. Spleen cells from TBH were also capable of suppressing the in vitro response of normal primed lymphocytes to DNP-BSA when admixed. Results from these experiments suggest that in vitro measurement of contact sensitivity was affected by suppressor cells/products existing in the spleens but not lymph nodes of fibrosarcoma-bearing mice. 相似文献
87.
Yuxiang Liu Tao V. Wang Yunfeng Cui Chaoyi Li Lifen Jiang Yi Rao 《The Journal of biological chemistry》2022,298(5)
We have recently purified mammalian sterile 20 (STE20)–like kinase 3 (MST3) as a kinase for the multifunctional kinases, AMP-activated protein kinase–related kinases (ARKs). However, unresolved questions from this study, such as remaining phosphorylation activities following deletion of the Mst3 gene from human embryonic kidney cells and mice, led us to conclude that there were additional kinases for ARKs. Further purification recovered Ca2+/calmodulin-dependent protein kinase kinases 1 and 2 (CaMKK1 and 2), and a third round of purification revealed mitogen-activated protein kinase kinase kinase kinase 5 (MAP4K5) as potential kinases of ARKs. We then demonstrated that MST3 and MAP4K5, both belonging to the STE20-like kinase family, could phosphorylate all 14 ARKs both in vivo and in vitro. Further examination of all 28 STE20 kinases detected variable phosphorylation activity on AMP-activated protein kinase (AMPK) and the salt-inducible kinase 3 (SIK3). Taken together, our results have revealed novel relationships between STE20 kinases and ARKs, with potential physiological and pathological implications. 相似文献
88.
Guangxin Zhao Jingying Wang Xi Chen Hanjing Sha Xin Liu Yunfei Han Guankai Qiu Fantao Zhang Jun Fang 《遗传学报》2022,49(9):870-880
COMPASS or COMPASS-like is a highly conserved polyprotein complex in eukaryotes that is often involved in methylation of histone H3 lysine 4(H3K4). However, the biological function of this complex in rice(Oryza sativa) is unclear. Here, we report the identifiction of their functions in growth and development. The osashl1osashl2 double mutant shows a dwarf and late-flowering phenotype. Lower expression of Ehd1, OsVIL4,and OsMADS51 in the osashl1 osashl2 double mutant background accompanies a dela... 相似文献
89.
In the early stages of infection, gaining control of the cellular protein synthesis machinery including its ribosomes is the ultimate combat objective for a virus. To successfully replicate, viruses unequivocally need to usurp and redeploy this machinery for translation of their own mRNA. In response, the host triggers global shutdown of translation while paradoxically allowing swift synthesis of antiviral proteins as a strategy to limit collateral damage. This fundamental conflict at the level of translational control defines the outcome of infection. As part of this special issue on molecular mechanisms of early virus–host cell interactions, we review the current state of knowledge regarding translational control during viral infection with specific emphasis on protein kinase RNA-activated and mammalian target of rapamycin-mediated mechanisms. We also describe recent technological advances that will allow unprecedented insight into how viruses and host cells battle for ribosomes. 相似文献