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71.
Summary The ultrastructure of atrial and ventricular myocardial cells from Acipenser stellatus is described. The cells of the atrium are more loosely connected than those of the ventricle. Cell contact is by simple intercalated discs and by desmosomes. The cells are flattened, with peripheral myofibrils and a central region of mitochondria and the nucleus. The sarcoplasmic reticulum consists of subsarcolemmal tubules, that frequently extend towards the central mitochondria. Dyads are small and positioned at any sarcomeric level. No T-tubules are present. Specific granules are restricted to the atrial cell, and are sometimes present within the SR tubules. 相似文献
72.
Harald Riedl 《Plant Systematics and Evolution》1979,131(3-4):217-233
25 species of lichens have been collected in semidesertic to desertic areas of Iran. On the basis of spatial relations to the substrate and anatomical features of the thallus three main groups (one with a subdivision based on colour and morphology of the thallus) can be differentiated. Selective advantages and peculiarities in connection with the desert habitat are pointed out, such as inverse thallus-structure, a dense network of skeletal hyphae in the substrate in otherwise epilithic species, proliferating areolae of the thallus, immersed pycnidia with trichogynes and brownish spores in groups with usually colourless spores. Most of the species are wide-spread in arid and often also in humid regions; only one species,Verrucaria buschirensis
J. Steiner, seems to be endemic. The prevalence of cyanophilic lichens in deserts may have phylogenetic reasons, as these groups appear to date back to periods without higher vegetation and a desert-like environment.
Herrn Prof. Dr. L.Geitler zum 80. Geburtstag gewidmet. 相似文献
73.
Harald Fuge 《Chromosoma》1978,65(3):241-246
Chromatin bridges of autosomal bivalents in anaphase I were observed in spermatocytes of Pales ferruginea. The bridges are formed without simultaneous production of akinetochoric (akinetic) fragments. A bridge consists of a single fiber up to approximately. 500 Å in diameter. Filamentous substructures of approximately 100 Å diameter can be visualized. It is suggested that these bridges represent a low order coiling of the chromatid, and may be caused by non-separation of the terminal segments of the chromatids (telomeres). 相似文献
74.
Summary Diffusates from flower buds, flower fruits, and scape segments, and extracts of flower stalks of Narcissus pseudonarcissus contain an auxin active in the Avena geo-curvature test. The auxin behaved like indole-3-acetic acid (IAA) in thin-layer chromatography (TLC) with neutral and basic solvents on different adsorbents. After TLC, the auxin of the extracts showed chromogenic reactions identical with those of IAA; in gas-liquid chromatography on two different columns, the purified substance, after methylation, appeared at the retention time of IAA methyl ester. The auxin content of the extracts has been estimated to be equivalent to ca. 10 g IAA kg–1 fresh weight. Diffusates, collected at the basal end of excised flowering apices and of scape segments at different developmental stages, showed highest auxin activity when collected from old buds and young flowers, and from the basal, rapidly elongating scape regions. The diffusible auxin obtained from scape segments was very likely produced by the segments themselves. Thus, the shoot of Narcissus appears to possess two different sites of auxin production, namely, the apical region represented by the flower bud, the flower or the fruit, and the scape.Abbreviations IAA
indole-3-acetic acid
- IAA-OMe
indole-3-acetic-acid methyl ester
- TLC
thin-layer chromatography
- GLC
gas-liquid chromatography 相似文献
75.
Harald Fuge 《Chromosoma》1975,52(2):149-158
Akinetochoric chromosomal fragments in spermatocytes of mutant Pales ferruginae are transported polewards in anaphase. During migration their surfaces form radial lamellar projections between which non-kinetochoric spindle microtubules become arranged in an orderly fashion. The same morphological features had been observed earlier in intact chromosomes in late anaphase. It is assumed that the fragments are transported by some kind of poleward directed "streaming" force of the anaphase spindle, which is applied to the fragment's surface. Non-kinetochoric microtubules are thought to be engaged in the generation or, at least, in the transmission of this spindle force. Due to the morphological similarities with akinetochoric fragments, extra-kinetochoral application sites for anaphase spindle forces can be also suggested for chromosomes possessing kinetochores. 相似文献
76.
Harald H. O. Schmid Patricia C. Schmid Viswanathan Natarajan 《Chemistry and physics of lipids》1996,80(1-2):133-142
Long-chain N-acylethanolamines (NAEs) elicit a variety of biological and pharmacological effects, Anandamide (20:4n-6 NAE) and other polyunsaturated NAEs bind to the cannabinoid receptor and may thus serve as highly specific lipid mediators of cell signalling. NAEs can be formed by phospholipase D-catalyzed hydrolysis of N-acylethanolamine phospholipids or by direct condensation of ethanolamine and fatty acid, So far, most of the latter biosynthetic activity has been shown to be the reverse reaction of the NAE amidohydrolase that catalyzes NAE degradation. Thus, increasing evidence supports the hypothesis that the N-acylation-phosphodiesterase pathway yields not only saturated-monounsaturated NAEs, but polyunsaturated ones, including anandamide, as well. 相似文献
77.
Volodymyr Trotsiuk Florian Hartig Maxime Cailleret Flurin Babst David I. Forrester Andri Baltensweiler Nina Buchmann Harald Bugmann Arthur Gessler Mana Gharun Francesco Minunno Andreas Rigling Brigitte Rohner Jonas Stillhard Esther Thürig Peter Waldner Marco Ferretti Werner Eugster Marcus Schaub 《Global Change Biology》2020,26(4):2463-2476
The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long‐term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3‐PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960–2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 ± 0.006 Mg C ha?1 year?1 km?1 for P. abies and 0.93 ± 0.010 Mg C ha?1 year?1 km?1 for F. sylvatica). During warm–dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm‐dry extremes. Importantly, cold–dry extremes had negative impacts on regional forest NPP comparable to warm–dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes. 相似文献
78.
Jason Lowery Edward R. Kuczmarski Harald Herrmann Robert D. Goldman 《The Journal of biological chemistry》2015,290(28):17145-17153
Intermediate filaments (IFs) are composed of one or more members of a large family of cytoskeletal proteins, whose expression is cell- and tissue type-specific. Their importance in regulating the physiological properties of cells is becoming widely recognized in functions ranging from cell motility to signal transduction. IF proteins assemble into nanoscale biopolymers with unique strain-hardening properties that are related to their roles in regulating the mechanical integrity of cells. Furthermore, mutations in the genes encoding IF proteins cause a wide range of human diseases. Due to the number of different types of IF proteins, we have limited this short review to cover structure and function topics mainly related to the simpler homopolymeric IF networks composed of vimentin, and specifically for diseases, the related muscle-specific desmin IF networks. 相似文献
79.
Schroeder CP Goeldner EM Schulze-Forster K Eickhoff CA Holtermann P Heidecke H 《Biological trace element research》2004,99(1-3):17-25
Selenite is frequently used in combination with cancer chemotherapeutic agents to reduce side effects. However, the cytoprotective
activity of selenite may also reduce the efficacy of chemotherapeutic drugs on tumor cells. This study was designed to examine
the effects of selenite combined with cytotoxic agents used in clinical protocols [e.g., doxorubicine, docetaxel, 5-fluorouracil
(5-FU), methotrexate (MTX), mafosphamide, mitomycin C, gemcitabine, etoposide, cisplatin, irinotecan, and oxaliplatin] on
the proliferation of various carcinoma cell types. The data demonstrated that selenite had no marked effects on the antiproliferative
activity of docetaxel, doxorubicine, 5-FU, MTX, and mafosphamide in MDA-MB-231 breast cancer cells. Likewise, no consistent
changes were observed in A549 lung cancer cell proliferation when selenite was combined with cisplatin, etoposide, gemcitabine,
or mitomycin C. On the other hand, selenite potentiated the cytotoxicity of 5-FU, oxaliplatin, and irinotecan in HCT116 colon
cancer cells by approx 1.1-fold, 2.7-fold, and 2.6-fold, respectively. In SW620 colon cancer cells, selenite induced a 1.5-fold
and 4.3-fold increase of the antiproliferative activity of 5-FU and oxaliplatin, respectively. Whereas irinotecan showed no
effects on SW620 cell growth, a combination with selenite resulted in 23% inhibition. Our results indicate that selenite did
not reduce the antiproliferative activity of chemotherapeutic agents in vitro. In addition, selenite was able to increase
the inhibitory activity of docetaxel in A549 lung cancer cells, and of 5-FU, oxaliplatin, and irinotecan in HCT116 and SW620
colon cancer cells implying selenite is potentially useful as an adjuvant chemotherapeutic agent. 相似文献
80.
Stefanie Wagner Frédéric Lagane Andaine Seguin‐Orlando Mikkel Schubert Thibault Leroy Erwan Guichoux Emilie Chancerel Inger Bech‐Hebelstrup Vincent Bernard Cyrille Billard Yves Billaud Matthias Bolliger Christophe Croutsch Katarina Čufar Frédérique Eynaud Karl Uwe Heussner Joachim Köninger Fabien Langenegger Frédéric Leroy Christine Lima Nicoletta Martinelli Garry Momber André Billamboz Oliver Nelle Antoni Palomo Raquel Piqué Marianne Ramstein Roswitha Schweichel Harald Stäuble Willy Tegel Xavier Terradas Florence Verdin Christophe Plomion Antoine Kremer Ludovic Orlando 《Molecular ecology》2018,27(5):1138-1154
Reconstructing the colonization and demographic dynamics that gave rise to extant forests is essential to forecasts of forest responses to environmental changes. Classical approaches to map how population of trees changed through space and time largely rely on pollen distribution patterns, with only a limited number of studies exploiting DNA molecules preserved in wooden tree archaeological and subfossil remains. Here, we advance such analyses by applying high‐throughput (HTS) DNA sequencing to wood archaeological and subfossil material for the first time, using a comprehensive sample of 167 European white oak waterlogged remains spanning a large temporal (from 550 to 9,800 years) and geographical range across Europe. The successful characterization of the endogenous DNA and exogenous microbial DNA of 140 (~83%) samples helped the identification of environmental conditions favouring long‐term DNA preservation in wood remains, and started to unveil the first trends in the DNA decay process in wood material. Additionally, the maternally inherited chloroplast haplotypes of 21 samples from three periods of forest human‐induced use (Neolithic, Bronze Age and Middle Ages) were found to be consistent with those of modern populations growing in the same geographic areas. Our work paves the way for further studies aiming at using ancient DNA preserved in wood to reconstruct the micro‐evolutionary response of trees to climate change and human forest management. 相似文献