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91.
Floral organogenesis of Chloranthus sessilifolius K. F. Wu is described. The inflorescence primordium is dome-like in the beginning and then elongates, and bract primordia
initiate almost decussately. Each floral primordium, arising from the axil of a bract, soon becomes a scale-like structure,
with three primordia of androecial lobes originating from its abaxial part, and the gynoecial primordium in adaxial position.
As the androecial lobes become more distinct, four thecae are already in differentiation, and the gynoecial primordium appears
as a shallow disc. The androecial lobes do not extend their length until the thecae approach maturity and the stigma is differentiated.
The androecial lobes are united at all the stages of development, and the entire androecium falls off as a unit at the end
of anthesis. Based on these results, combined with published evidence from neobotany, palaeobotany and phylogenetic studies,
the morphological nature of the androecium of Chloranthus is further discussed. Our studies support the viewpoint that the androecial structure of Chloranthus may have arisen by splitting of a single stamen with 2 marginal thecae.
Received May 2, 2001 Accepted December 18, 2001 相似文献
92.
S. Shi Y. Huang Y. Zhong Y. Du Q. Zhang H. Chang D. E. Boufford 《Plant Systematics and Evolution》2001,230(1-2):13-24
Phylogenetic relationships of the three genera of the family Altingiaceae, i.e., Altingia, Liquidambar and Semiliquidambar, based on matK sequences and the intergenic spacer between the psaA and ycf3 genes (PY-IGS) of cpDNA, and on the internal transcribed spacer (ITS) of nrDNA were studied. Phylogenetic trees based on
the three data sets (matK, PY-IGS and ITS) were generated using Hamamelis japonica and Mytilaria laosensis (Hamamelidaceae), Cercidiphyllum japonicum (Cercidiphyllaceae), and Daphniphyllum calycinum (Daphniphyllaceae) as outgroups. The partition-homogeneity tests indicated that the three data sets and the combined data
are homogeneous. A combined analysis also generated a strongly supported phylogeny. The phylogenetic trees show that the North
American and western Asian species, L. styraciflua and L. orientalis, respectively, form a monophyletic group which is sister to the clade including all Asian species in the family. The genus
Liquidambar is paraphyletic with Altingia and Semiliquidambar nested within. Phylogenetic analyses of the molecular data indicate that taxonomic reexamination of the generic delimitation
in the Altingiaceae is needed.
Received December 20, 2000 Accepted June 25, 2001 相似文献
93.
Double-Stranded RNA in Rice 总被引:2,自引:0,他引:2
Toshiyuki Fukuhara 《Journal of plant research》1999,112(1):131-138
Oryza sativa ) and wild rice (O. rufipogon) tissues. It is detected at every developmental stage, and is transmitted very efficiently to progeny via seeds (more than
98%). The dsRNA is maintained at a constant level (approximately 100 copies/cell) in almost all tissues. However, the number
of copies increases about 10-fold when host cells are grown in suspension culture. Complete nucleotide sequences of cultivated
rice (temperate japonica rice, cv. Nipponbare, J-dsRNA) and wild rice (W-1714, W-dsRNA) dsRNAs have been determined. Both wild and cultivated rice
dsRNAs have a single long open reading frame (ORF) containing the conserved motifs of RNA-dependent RNA polymerase and RNA
helicase. The coding strands of both contain a site-specific discontinuity (nick) at nt 1,211 (J-dsRNA) or at nt 1,197 (W-dsRNA)
from the 5′ end of their coding strand. Rice dsRNA has several unique properties and can be regarded as a novel RNA replicon.
This paper discusses the origin and evolution of the rice dsRNA.
Received 23 October 1998/ Accepted in revised form 15 December 1998 相似文献
94.
Sébastien Descamps Stan Boutin Andrew G. McAdam Dominique Berteaux Jean-Michel Gaillard 《Proceedings. Biological sciences / The Royal Society》2009,276(1659):1129-1135
The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits. 相似文献
95.
《Journal of molecular biology》2021,433(22):167254
Tau is an intrinsically disordered protein implicated in many neurodegenerative diseases. The repeat domain fragment of tau, tau-K18, is known to undergo a disorder to order transition in the presence of lipid micelles and vesicles, in which helices form in each of the repeat domains. Here, the mechanism of helical structure formation, induced by a phospholipid mimetic, sodium dodecyl sulfate (SDS) at sub-micellar concentrations, has been studied using multiple biophysical probes. A study of the conformational dynamics of the disordered state, using photoinduced electron transfer coupled to fluorescence correlation spectroscopy (PET-FCS) has indicated the presence of an intermediate state, I, in equilibrium with the unfolded state, U. The cooperative binding of the ligand (L), SDS, to I has been shown to induce the formation of a compact, helical intermediate (IL5) within the dead time (∼37 µs) of a continuous flow mixer. Quantitative analysis of the PET-FCS data and the ensemble microsecond kinetic data, suggests that the mechanism of induction of helical structure can be described by a U ↔ I ↔ IL5 ↔ FL5 mechanism, in which the final helical state, FL5, forms from IL5 with a time constant of 50–200 µs. Finally, it has been shown that the helical conformation is an aggregation-competent state that can directly form amyloid fibrils. 相似文献
96.
97.
《Journal of molecular biology》2021,433(5):166809
Macroautophagy is a bulk degradation mechanism in eukaryotic cells. Efficiency of an essential step of this process in yeast, Atg8 lipidation, relies on the presence of Atg16, a subunit of the Atg12–Atg5-Atg16 complex acting as the E3-like enzyme in the ubiquitination-like reaction. A current view on the functional structure of Atg16 in the yeast S. cerevisiae comes from the two crystal structures that reveal the Atg5-interacting α-helix linked via a flexible linker to another α-helix of Atg16, which then assembles into a homodimer. This view does not explain the results of previous in vitro studies revealing Atg16-dependent deformations of membranes and liposome-binding of the Atg12–Atg5 conjugate upon addition of Atg16. Here we show that Atg16 acts as both a homodimerizing and peripheral membrane-binding polypeptide. These two characteristics are imposed by the two distinct regions that are disordered in the nascent protein. Atg16 binds to membranes in vivo via the amphipathic α-helix (amino acid residues 113–131) that has a coiled-coil-like propensity and a strong hydrophobic face for insertion into the membrane. The other protein region (residues 64–99) possesses a coiled-coil propensity, but not amphipathicity, and is dispensable for membrane anchoring of Atg16. This region acts as a Leu-zipper essential for formation of the Atg16 homodimer. Mutagenic disruption in either of these two distinct domains renders Atg16 proteins that, in contrast to wild type, completely fail to rescue the autophagy-defective phenotype of atg16Δ cells. Together, the results of this study yield a model for the molecular mechanism of Atg16 function in macroautophagy. 相似文献
98.
99.
Spliceosome-targeted therapies trigger an antiviral immune response in triple-negative breast cancer
Elizabeth A. Bowling Jarey H. Wang Fade Gong William Wu Nicholas J. Neill Ik Sun Kim Siddhartha Tyagi Mayra Orellana Sarah J. Kurley Rocio Dominguez-Vidaña Hsiang-Ching Chung Tiffany Y.-T. Hsu Julien Dubrulle Alexander B. Saltzman Heyuan Li Jitendra K. Meena Gino M. Canlas Srinivas Chamakuri Thomas F. Westbrook 《Cell》2021,184(2):384-403.e21
100.
《Cell》2021,184(20):5215-5229.e17