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排序方式: 共有563条查询结果,搜索用时 125 毫秒
71.
Isabel Moura Sofia R. Pauleta José J. G. Moura 《Journal of biological inorganic chemistry》2008,13(8):1185-1195
Metalloenzymes control enzymatic activity by changing the characteristics of the metal centers where catalysis takes place.
The conversion between inactive and active states can be tuned by altering the coordination number of the metal site, and
in some cases by an associated conformational change. These processes will be illustrated using heme proteins (cytochrome
c nitrite reductase, cytochrome c peroxidase and cytochrome cd
1 nitrite reductase), non-heme proteins (superoxide reductase and [NiFe]-hydrogenase), and copper proteins (nitrite and nitrous
oxide reductases) as examples. These examples catalyze electron transfer reactions that include atom transfer, abstraction
and insertion. 相似文献
72.
Laiyong Mu Roy E. Ritzmann 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2008,194(3):283-298
Tethered cockroaches turn from unilateral antennal contact using asymmetrical movements of mesothoracic (T2) legs (Mu and
Ritzmann in J Comp Physiol A 191:1037–1054, 2005). During the turn, the leg on the inside of the turn (the inside T2 leg) has distinctly different motor patterns from those
in straight walking. One possible neural mechanism for the transformation from walking to inside leg turning could be that
the descending commands alter a few critical reflexes that start a cascade of physical changes in leg movement or posture,
leading to further alterations. This hypothesis has two implications: first, the descending activities must be able to influence
thoracic reflexes. Second, one should be able to initiate the turning motor pattern without descending signals by mimicking
a point farther down in the reflex cascade. We addressed the first implication in this paper by experiments on chordotonal
organ reflexes. The activity of depressor muscle (Ds) and slow extensor tibia muscle (SETi) was excited and inhibited by stretching
and relaxing the femoral chordotonal organ. However, the Ds responses were altered after eliminating the descending activity,
while the SETi responses remain similar. The inhibition to Ds activity by stretching the coxal chordotonal organ was also
altered after eliminating the descending activity. 相似文献
73.
Highly toxic beryllium(II) is divalent metal ion with a high charge density, making it a potential target for binding to bio-molecules rich in O donor groups. In aqueous solution Be2+ binds to ATP and ADP to form 1:1 Be2+:ATP and Be2+:ADP complexes in relatively acidic media. At neutral pH the complex formed undergoes hydrolysis. Be2+ binding to ATP and ADP is much stronger than Ca2+ and Mg2+ binding. The high affinity of Be2+ toward ATP and ADP binding suggests a mechanism relevant to understanding the in vivo chemical toxicity of this metal. 相似文献
74.
Low-temperature, single crystal X-ray structural characterisations of trans-[NiCl2(HOMe)4], trans-O-[Ni(MeOH)2(μ-Cl)(2/2)2](∞∣∞) · 0.5dioxan and trans-trans-[Ni(H2O)2Cl2(O-dioxan-O)(2/2)](∞∣∞) · dioxan are recorded, offering intriguing insights into O-donor/Ni(II) relativities. All nickel atoms in all structures are located on crystallographic inversion centres, the last two compounds being one-dimensional polymers. 相似文献
75.
M. Tsaramyrsi D. Kavousanaki C. P. Raptopoulou A. Terzis A. Salifoglou 《Inorganica chimica acta》2001,320(1-2):47-59
The aqueous chemistry of vanadium with physiologically relevant ligands constitutes a subject of burgeoning research, extending from bacterial metalloenzymic functions to human-health physiology. Vanadium, in the form of VCl3 and V2O5, reacted expediently with citric acid, in a 1:2 molar ratio in water at pH4, and, in the presence of various cations, afforded crystalline materials bearing the general formula (Cat)2[V2O4(C6H6O7)2]·nH2O (A) (Cat+=Na+, NH4 +, n=2; Me4N+, K+, n=4). Exploration of the reactivity of A toward H2O2 yielded the peroxo-containing complexes (Cat)2[V2O2(O2)2(C6H6O7)2]·2H2O (B) (Cat+=K+, NH4 +). Both classes of compounds were characterized analytically and spectroscopically. The X-ray structures of complexes A and B emphasize the exceptional stability of the dimeric rhombic unit VV 2O2, which is retained upon H2O2 reaction, and the preserved mode of coordination of the citrate ligand as a doubly deprotonated moiety. In these complexes, typical six and eight coordination numbers were observed for the Na+ and K+ counter-ions, respectively. The variety of synthetic approaches leading to A, along with the stepwise and direct assembly and isolation of peroxo-compounds (B), denotes the significance of reaction pathways and intermediates in vanadium(III–V)–citrate synthetic chemistry. Hence, a systematic investigation of reactivity modes in aqueous vanadium–citrate systems emerges as a crucial tool for the establishment of chemical interconnectivity among low MW complex species, potentially participating in the intricate biodistribution of that metal ion in biological fluids. 相似文献
76.
Trans-imidazolium (bis imidazole) tetrachloro ruthenate (RuIm) and trans-indazolium (bis indazole) tetrachloro ruthenate (RuInd) are ruthenium coordination complexes, which were first synthesized and exploited for their anticancer activity. These molecules constitute two of the few most effective anticancer ruthenium compounds. The clinical use of these compounds however was hindered due to toxic side effects on the human body. Our present study on topoisomerase II poisoning by these compounds shows that they effectively poison the activity of topoisomerase II by forming a ternary cleavage complex of DNA, drug and topoisomerase II. The thymidine incorporation assays show that the inhibition of cancer cell proliferation correlates with topoisomerase II poisoning. The present study on topoisomerase II poisoning by these two compounds opens a new avenue for renewing further research on these compounds. This is because they could be effective lead candidates for the development of more potent and less toxic ruthenium containing topoisomerase II poisons. Specificity of action on this molecular target may reduce the toxic effects of these ruthenium-containing molecules and thus improve their therapeutic index. 相似文献
77.
We examined hand preferences in 23 tufted capuchins (Cebus apella) in 2 tasks requiring the lid of a box to be lifted before taking out a peanut. The first task, Box 1, could entail either 2 or 3 problem-solving acts, with the 3-act solution involving bimanual coordination for food retrieval. The second task, Box 2, involved only the 3-act solution. The results indicated that the types of solution employed to perform the task influenced capuchin hand preferences. In the 2-act solution, capuchins exhibited a significant right-hand bias for the final one-handed reaching action, but not for the initial lid lifting action. In contrast, in the 3-act solution, no significant asymmetry emerged for any act. We noted a significant effect of subject's sex on the strength of laterality, with males being more strongly lateralized than females. We discuss results in the light of recent models of primate laterality. 相似文献
78.
Chemical aspects of siderophore mediated iron transport 总被引:15,自引:7,他引:8
In this mini-review we describe selected aspects of the coordination chemistry relevant to siderophore mediated iron transport and bioavailability. Specific emphasis is placed on a discussion of in vitro kinetic and thermodynamic data that are relevant to elucidating possible in vivo mechanisms for environmental iron acquisition by microbial cells. 相似文献
79.
Recent experiments on the sensory and central mechanisms that coordinate animal locomotory movements have advanced our understanding of the relative importance of these two components and overturned some previously held notions. In different experimental preparations, sensory inputs and central pattern generators have now been shown to play different roles in setting intersegmental phase lags. 相似文献
80.
Ralf Heinrich N. Elsner 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1997,180(3):257-269
Stridulation in many gomphocerine grasshoppers is characterized by specific phase shifts between the two hindlegs as well
as different movement patterns produced by the left and the right leg. The underlying neuronal excitation patterns are generated
by networks on either side of the metathoracic ganglion. The role of the intraganglionic commissures in right-left coordination
and the production of differing movement patterns was investigated by transecting the metathoracic ganglion mediosagittally
in Omocestus viridulus, Chorthippus biguttulus and Chorthippus mollis. In all three species, after this operation both hindlegs produced the same pattern and no longer different movements. The effects of transection on coordination differed: rapid movement rhythms, like
those typical of Ch. biguttulus and the vibratory parts of the song of Ch. mollis, on the two sides drifted with respect to one another. In contrast, the slow rhythms characteristic of O. viridulus and the song subunits of Ch. mollis were completely synchronized. It is inferred that in intact animals the pathways for coordination of the rapid stridulatory
rhythms are exclusively intraganglionic, whereas the phase relations of the slow rhythms are additionally influenced by way
of anterior right-left connections, perhaps within the suboesophageal ganglion.
Accepted: 15 October 1996 相似文献