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971.
Michael Klockmann Uta Schröder Fajes Karajoli Klaus Fischer 《Entomologia Experimentalis et Applicata》2016,158(1):60-68
Temperature is one of the most important ecological factors affecting species survival and distributions. Therefore, global climate change, involving increases in mean surface temperature and the occurrence of extreme weather events, may pose a substantial challenge to biodiversity. Whereas tropical ectotherms are believed to be very sensitive to climate change, temperate‐zone species may actually benefit from higher temperatures. However, as in temperate zones large parts of the year are unsuitable for growth and reproduction, seasonal time constraints may complicate matters. Against this background we here investigate the impact of simulated climate change, involving increased mean temperatures and heat waves, across developmental pathways of the butterfly Lycaena tityrus (Poda) (Lepidoptera: Lycaenidae). Increased temperatures speeded up development but decreased pupal mass as expected. However, we found no evidence for detrimental effects of increased temperatures or even simulated heat waves. Furthermore, patterns did not differ between indirectly and directly developing individuals, which are assumed to be more time constrained. Our findings support the notion that not all species will be detrimentally affected by climate change, and suggest that species attributes may be more important than potential time constraints imposed by different developmental pathways. 相似文献
972.
We studied domain formation in mixtures of the monounsaturated lipids SOPC and POPE as a function of temperature and composition by NMR. Magic angle spinning at kHz frequencies restored resolution of (1)H NMR lipid resonances in the fluid phase, whereas the linewidth of gel-phase lipids remained rather broad and spinning frequency dependent. In regions of fluid- and gel-phase coexistence, spectra are a superposition of resonances from fluid and gel domains, as indicated by the existence of isosbestic points. Quantitative determination of the amount of lipid in the coexisting phases is straightforward and permitted construction of a binary phase diagram. Lateral rates of lipid diffusion were determined by (1)H MAS NMR with pulsed field gradients. At the onset of the phase transition near 25 degrees C apparent diffusion rates became diffusion time dependent, indicating that lipid movement is obstructed by the formation of gel-phase domains. A percolation threshold at which diffusion of fluid-phase lipid becomes confined to micrometer-size domains was observed when approximately 40% of total lipid had entered the gel phase. The results indicate that common phosphatidylethanolamines may trigger domain formation in membranes within a physiologically relevant temperature range. This novel NMR approach may aid the study of lipid rafts. 相似文献
973.
Sex-related differences in reaction norms in the butterfly Lycaena tityrus (Lepidoptera: Lycaenidae)
We investigate sexual differences in reaction norms in directly developing individuals of the copper butterfly Lycaena tityrus predicted from sexual selection theory. As recent studies on butterflies revealed a high degree of adaptive plasticity in growth and development, which may undermine the basic trade‐offs assumed in life‐history theory, we focus on effects of temperature, trying to drive growth rates to their physiological upper limit and thus disclosing otherwise potentially concealed responses. Development time strongly depended on temperature, leading in accordance with a central assumption in life‐history theory to a larger size at low temperatures, and vice versa. At all temperatures larval development time of males was significantly shorter compared to females, as was predicted by protandry theory. This was partially due to an invariably higher growth rate of males. However, sexes responded in different ways to developmental time constraints caused by increasing temperatures. Despite the shorter larval time of males, both sexes achieved similar body sizes at lower temperatures, because males avoided a reduction in weight due to plastic growth. At high temperatures, in contrast, males were forced to make a trade‐off in which they favoured early emergence over large size, leading to a dramatic weight loss. Weight of females, however, remained similar throughout showing no trade‐off. These different reaction norms reflect divergent selective pressures acting on males and females, which can be explained in relation to the reproductive system. The strong selection for early emergence in males is likely to be due to monandry, discrete non‐overlapping generations (as was already predicted by theory), and territoriality, because prior ownership of a territory seems to be a major advantage for successful reproduction. On the other hand, the preference of females for large body size was expected due to the close relationship between this trait and fecundity. Thus, our results highlight the extraordinary importance of the specific reproductive system, which can influence central life‐history traits in manifold ways. 相似文献
974.
Auxin and the developing root of Arabidopsis thaliana 总被引:3,自引:0,他引:3
William D. Teale Ivan A. Paponov Franck Ditengou Klaus Palme 《Physiologia plantarum》2005,123(2):130-138
The plant hormone auxin has long been known to play a crucial role in plant growth and development, but how it affects so many different processes has remained a mystery. Recent evidence from genetic and molecular studies has begun to reveal a possible mechanism for auxin action. In this article we will present an overview with specific emphasis on auxin's role in roots of Arabidopsis thaliana , focusing on cell division, elongation and differentiation. 相似文献
975.
Death receptor-induced signaling pathways are differentially regulated by gamma interferon upstream of caspase 8 processing 下载免费PDF全文
Siegmund D Wicovsky A Schmitz I Schulze-Osthoff K Kreuz S Leverkus M Dittrich-Breiholz O Kracht M Wajant H 《Molecular and cellular biology》2005,25(15):6363-6379
FasL and gamma interferon (IFN-gamma) are produced by activated T cells and NK cells and synergistically induce apoptosis. Although both cytokines can also elicit proinflammatory responses, a possible cross talk of these ligands with respect to nonapoptotic signaling has been poorly addressed. Here, we show that IFN-gamma sensitizes KB cells for apoptosis induction by facilitating death-inducing signaling complex (DISC)-mediated caspase 8 processing. Moreover, after protection against death receptor-induced apoptosis by caspase inhibition or Bcl2 overexpression, IFN-gamma also sensitized for Fas- and TRAIL death receptor-mediated NF-kappaB activation leading to synergistic upregulation of a variety of proinflammatory genes. In contrast, Fas-mediated activation of JNK, p38, and p42/44 occurred essentially independent from IFN-gamma sensitization, indicating that the apoptosis- and NF-kappaB-related FasL-IFN-gamma cross talk was not due to a simple global enhancement of Fas signaling. Overexpression of FLIP(L) and FLIP(S) inhibited Fas- as well as TRAIL-mediated NF-kappaB activation and apoptosis induction in IFN-gamma-primed cells suggesting that both responses are coregulated at the level of the DISC. 相似文献
976.
Theoretical and experimental studies suggest that mating and pair formation are not likely to be random. Assortative mating, characterized as self seeking like, seems to be widely practiced in nature. Experimental evidence for it is strong among humans seeking a mate. Assortative mating increases the probability of finding a genetically similar mate, without fomenting inbreeding, achieving assortative mating without hindering the working of other mate-selection strategies that aim to maximize the search for good genes, optimizing the working of sex in evolutionary terms. Self seeking like seems to be a behavioural inborn trait among humans, and here we present evidence that the same behavioural mechanism seems to be at work when humans choose a pet. We show that in a significant proportion of human–pet pairs, sampled in pet beauty contests, the partners show much higher facial resemblances than can be expected by random pair formation. 相似文献
977.
To investigate natural killer (NK) and lymphokine-activated killer (LAK) cell functions from 10 healthy dogs and 29 dogs with a variety of spontaneous neoplasms, large granular lymphocytes (LGLs) from blood samples were separated by a 58.5% Percoll density gradient. LGLs were stimulated with a low dose of recombinant human interleukin 2 (rhIL-2) for 7 days. Cytotoxicity of effector cells against the susceptible CTAC cell line was measured before and after stimulation. Compared with those before stimulation, the percentage of LGLs after stimulation with rhIL-2 was found to be significantly increased (P<0.01) in both dogs with tumors and controls. However, the increase was significantly higher in control animals, indicating a defect in proliferation ability of NK cells in canine tumor patients. After stimulation with rhIL-2, lymphokine-activated killer (LAK) cell activity in dogs with tumors was significantly lower (P<0.01) when compared with controls. Reduced cytotoxicity of rhIL-2–activated NK cells in dogs with tumors seems to be attributable to the presence of a diminished proliferative capacity of NK cells and a decreased ability of LAK cells to lyse target cells. Further knowledge of the precise function of IL-2–activated NK cells in dogs with tumors may help to optimize new and therapeutically beneficial treatment strategies in canine and human cancer patients. Our findings suggest that the dog could also serve as a relevant large animal model for cancer immunotherapy with IL-2. 相似文献
978.
Smith DF Galkina E Ley K Huo Y 《American journal of physiology. Heart and circulatory physiology》2005,289(5):H1976-H1984
Chemokines participate in various processes of monocyte recruitment including monocyte arrest and migration. Our group and others have demonstrated that growth-related oncogene (GRO)-alpha (CXCL1) can support monocyte arrest in models of inflammation. Here we employed a parallel plate-flow chamber and Transwell reconstitution assay to test whether GRO family chemokines were sufficient for Mono Mac 6 (a human monocytic cell line) and isolated human monocyte recruitment. Our study shows that 1) GRO-alpha, -beta (CXCL2), and -gamma (CXCL3) all act as arrest chemokines for monocyte adhesion on vascular cell adhesion molecule (VCAM)-1 under flow in the presence of P-selectin; 2) CXCR2 is the functional receptor for GRO-family chemokines in monocyte arrest; however, CXCR2 is not an arrest chemokine receptor in general, since epithelial neutrophil-activating peptide ENA-78 failed to arrest monocytes; 3) GRO-alpha, -beta, and -gamma all fail to increase intracellular free Ca2+ or mediate monocyte chemotaxis; and 4) signaling through G alpha(i) protein, phosphoinositide 3-kinase, and actin polymerization but not Ca2+ mobilization or the mitogen-activated kinases p38 and MAPK/extracellular signal-related kinase are necessary for GRO-alpha-mediated Mono Mac 6 cell arrest under flow. We conclude that the GRO-family chemokines are specialized monocyte-arrest chemokines. Their role in monocyte recruitment in inflammation can be inhibited by blocking CXCR2 function or downstream signaling events. 相似文献
979.
980.
Fission yeast MO25 protein is localized at SPB and septum and is essential for cell morphogenesis 下载免费PDF全文
Kanai M Kume K Miyahara K Sakai K Nakamura K Leonhard K Wiley DJ Verde F Toda T Hirata D 《The EMBO journal》2005,24(17):3012-3025
Cell morphogenesis is of fundamental significance in all eukaryotes for development, differentiation, and cell proliferation. In fission yeast, Drosophila Furry-like Mor2 plays an essential role in cell morphogenesis in concert with the NDR/Tricornered kinase Orb6. Mutations of these genes result in the loss of cell polarity. Here we show that the conserved proteins, MO25-like Pmo25, GC kinase Nak1, Mor2, and Orb6, constitute a morphogenesis network that is important for polarity control and cell separation. Intriguingly, Pmo25 was localized at the mitotic spindle pole bodies (SPBs) and then underwent translocation to the dividing medial region upon cytokinesis. Pmo25 formed a complex with Nak1 and was required for both the localization and kinase activity of Nak1. Pmo25 and Nak1 in turn were essential for Orb6 kinase activity. Further, the Pmo25 localization at the SPBs and the Nak1-Orb6 kinase activities during interphase were under the control of the Cdc7 and Sid1 kinases in the septation initiation network (SIN), suggesting a functional linkage between SIN and the network for cell morphogenesis/separation following cytokinesis. 相似文献