全文获取类型
收费全文 | 7237篇 |
免费 | 578篇 |
国内免费 | 4篇 |
出版年
2023年 | 21篇 |
2022年 | 55篇 |
2021年 | 117篇 |
2020年 | 52篇 |
2019年 | 99篇 |
2018年 | 105篇 |
2017年 | 102篇 |
2016年 | 209篇 |
2015年 | 325篇 |
2014年 | 397篇 |
2013年 | 502篇 |
2012年 | 641篇 |
2011年 | 551篇 |
2010年 | 371篇 |
2009年 | 313篇 |
2008年 | 465篇 |
2007年 | 469篇 |
2006年 | 404篇 |
2005年 | 415篇 |
2004年 | 388篇 |
2003年 | 355篇 |
2002年 | 337篇 |
2001年 | 68篇 |
2000年 | 43篇 |
1999年 | 74篇 |
1998年 | 79篇 |
1997年 | 52篇 |
1996年 | 53篇 |
1995年 | 63篇 |
1994年 | 39篇 |
1993年 | 45篇 |
1992年 | 55篇 |
1991年 | 39篇 |
1990年 | 40篇 |
1989年 | 23篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 19篇 |
1985年 | 25篇 |
1984年 | 39篇 |
1983年 | 17篇 |
1982年 | 38篇 |
1981年 | 19篇 |
1980年 | 13篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1976年 | 15篇 |
1975年 | 18篇 |
1974年 | 12篇 |
排序方式: 共有7819条查询结果,搜索用时 15 毫秒
1.
2.
Ulrich Weser Karl-Heinz Sellinger Edmund Lengfelder Walther Werner Joachim Strähle 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,631(2):232-245
The copper complex of indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate), a common anti-inflammatory drug, was prepared and characterized. Crystal structure determination revealed the dimeric form of the 1:2 complex, namely Cu2(indomethacin)4 · L2, in the unit cell. Suprisingly, the copper-copper distance (263 pm) was very close to metallic copper (256 pm). The two coordination sites in the copper-copper axis can be readily replaced by superoxide. An intriguing similarity to Cu2(acetate)4 was seen.Due to the lipophilic nature of the indomethacin ligand, this copper complex reacted with superoxide in aprotic solvents. The superoxide dismutating activity was successfully demonstrated in Me2SO/water and acetonitrile/water mixtures using the nitro-blue tetrazolium assay and pulse radiolysis. The second-order rate constant of 6 · 109 M?1 · s?1 in strictly aqueous systems dropped only slightly to 1.1 · 109 M?1 · s?1 when aprotic solvents were used. This is the fastest rate constant ever observed for a copper-dependent dismutation of superoxide. The KO2-induced lipid peroxidation in both erythrocytes and liver microsomes was suppressed by 70% in the presence of 1 · 10?10 mol · ml?1 of Cu2(indomethacin)4. The inhibitory action dropped to 25% when Cu2Zn2superoxide dismutase was employed. The formation of copper · indomethacin in rat serum after administration of indomethacin was shown in vitro and in vivo. 相似文献
3.
Hydrobiologia - To observe effects on the phosphorus retention mechanisms of a lake after re-colonisation by macrophytes, Potamogeton crispus L. and Elodea canadensis Michx. were planted in lab... 相似文献
4.
5.
Mechanics and modeling of plant cell growth 总被引:1,自引:0,他引:1
6.
7.
Martin Nichelmann Joachim Hchel Barbara Tzschentke 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》1999,124(4):769
The aim of this review is to show that probably the internal clock of precocial birds is imprinted in the prenatal period by exogenous factors (zeitgeber). The activity of organ functions occurs early during embryonic development, before this function is ultimately necessary to ensure the survival of the embryo. Prenatal activation of some functional systems may have a training effect on the postnatal efficiency.The development of physiological control systems is influenced by endogenous and exogenous factors during the late prenatal and early postnatal period: epigenetic adaptation processes play an important role in the development of animals; they have acquired characteristics which are innated but not genetically fixed. As a rule, the actual value during the determination period has a very strong influence on the set-point of the system. This will be explained using the example of thermoregulation.It is shown in detail that it seems to be possible to imprint the prenatal development of circadian rhythms by periodic changes of the light-dark cycle but not by rhythmic influence of acoustic signals.Altogether, there are more questions open than solved concerning the perinatal genesis of circadian rhythms in birds. Topics are given for the future research. 相似文献
8.
9.
Frank Josef Mller Oliver Zierau Torsten Hertrampf Anja Bliedtner Patrick Diel Günter Vollmer 《The Journal of steroid biochemistry and molecular biology》2009,113(3-5):296-303
Isoflavones (ISOs) are bioactive food ingredients of the traditional East Asian diet and currently discussed as alternatives to classical hormone replacement therapies and for reducing the prevalence of hormone-dependent cancers. Although there are many studies on ISOs, not much is known about their long-term effects.Therefore, we performed an animal experiment analyzing the effects of three different diets: a phytoestrogen-free diet, a diet supplemented with genistein (700 μg/g diet) and an ISO-high diet (232 μg daidzein and 240 μg genistein/g) at two distinct time points, juvenile (21 days) and adult (97 days). Exposure started prior to mating of the parents and throughout the life of the offspring.We observed a stronger increase of uterine wet weights in juvenile offspring with genistein exposure (1018 ± 350 mg/kg BW) than with ISO-high diet (497 ± 133 mg/kg BW). Whereas the expression of proliferation related genes (PCNA; Ki67; IGF-1; IGF-1R), analyzed by real-time-qPCR and Western blot, were significantly down-regulated in juvenile animals exposed to genistein. Additionally, genistein exposure led to estrogenic responses, observed upon increase of complement C3 and decrease of estrogen receptors gene expressions, while the exposure to ISO-high diet did not show these effects.In conclusion, both the time point on which phytoestrogen exposure starts together with the composition of the ingested phytoestrogen containing diet are of great importance for the biological response of the offspring. 相似文献
10.