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911.
In this work, direct DNA damage induced by low-energy electrons (<5 keV) is simulated using Monte Carlo methods, and the resulting
yield of various strand breaks and base damages in cellular environment is presented. The simulation is based on a new inelastic
cross section for the production of electron track structure in liquid water, and on ionization cross sections of DNA bases
to generate base radical. Especially, a systematic approach of simulating detailed base damage is suggested. This approach
includes improvement of a volume model of DNA, generation of the DNA base sequence, conversion of ionization events in liquid
water at hit site to the ionization interaction of electrons with DNA bases and development of an algorithm to convert a base
radical to a damage. The results obtained in terms of strand breaks are compared with those of experiments and other theoretical
calculations, and good agreement was obtained. The yield of detailed base damages and clustered DNA damages caused by the
combination of various strand breaks and base damages is presented, and the corresponding distribution characteristics are
analyzed. The influence of the relative content of base pairs A-T and G-C in a DNA segment on the yield of both strand breaks
and base damages is also explored. The present work provides fundamental information on DNA damage and represents the first
effort toward the goal of obtaining the spectrum of clustered DNA damage including detailed base damages, for the mechanistic
interpretation and prediction of radiation effects. 相似文献
912.
Background and Aims
Diptychocarpus strictus is an annual ephemeral in the cold desert of northwest China that produces heteromorphic fruits and seeds. The primary aims of this study were to characterize the morphology and anatomy of fruits and seeds of this species and compare the role of fruit and seed hetermorphism in dispersal and germination.Methods
Shape, size, mass and dispersal of siliques and seeds and the thickness of the mucilage layer on seeds were measured, and the anatomy of siliques and seeds, the role of seed mucilage in water absorption/dehydration, germination and adherence of seeds to soil particles, the role of pericarp of lower siliques in seed dormancy and seed after-ripening and germination phenology were studied using standard procedures.Key Results
Plants produce dehiscent upper siliques with a thin pericarp containing seeds with large wings and a thick mucilage layer and indehiscent lower siliques with a thick pericarp containing nearly wingless seeds with a thin mucilage layer. The dispersal ability of seeds from the upper siliques was much greater than that of intact lower siliques. Mucilage increased the amount of water absorbed by seeds and decreased the rate of dehydration. Seeds with a thick mucilage layer adhered to soil particles much better than those with a thin mucilage layer or those from which mucilage had been removed. Fresh seeds were physiologically dormant and after-ripened during summer. Non-dormant seeds germinated to high percentages in light and in darkness. Germination of seeds from upper siliques is delayed until spring primarily by drought in summer and autumn, whereas the thick, indehiscent pericarp prevents germination for >1 year of seeds retained in lower siliques.Conclusions
The life cycle of D. strictus is morphologically and physiologically adapted to the cold desert environment in time and space via a combination of characters associated with fruit and seed heteromorphism. 相似文献913.
Background
Caffeine, a nonselective adenosine A1 and A2A receptor antagonist, is the most widely used psychoactive substance in the world. Evidence demonstrates that caffeine and selective adenosine A2A antagonists interact with the neuronal systems involved in drug reinforcement, locomotor sensitization, and therapeutic effect in Parkinson's disease (PD). Evidence also indicates that low doses of caffeine and a selective adenosine A2A antagonist SCH58261 elicit locomotor stimulation whereas high doses of these drugs exert locomotor inhibition. Since these behavioral and therapeutic effects are mediated by the mesolimbic and nigrostriatal dopaminergic pathways which project to the striatum, we hypothesize that low doses of caffeine and SCH58261 may modulate the functions of dopaminergic neurons in the striatum. 相似文献914.
Isozyme and protein electrophoresis data from mycelial extracts of 27 isolates of Trichoderma harzianum, 10 isolates of T. aureoviride and 10 isolates of T. longibrachiatum from Southern Peninsular Malaysia were investigated. The eight enzyme and a single protein pattern systems were analyzed. Three isozyme and total protein patterns were shown to be useful for the detection of three Trichoderma species. The isozyme and protein data were analyzed using the Nei and Li Dice similarity coefficient for pairwise comparison between individual isolates, species isolate group, and for generating a distance matrix. The UPGMA cluster analysis showed a higher degree of relationship between T. harzianum and T. aureoviride than to T. longibrachiatum. These results suggested that the T. harzianum isolates had high levels of genetic variation compared to the other isolates of Trichoderma species. 相似文献
915.
Murugan Loganathan Subbiyan Maruthasalam Ling Yin Shiu Wei Ching Lien Wen Hwei Hsu Pei Fang Lee Chih Wen Yu Chin Ho Lin 《In vitro cellular & developmental biology. Plant》2010,46(3):265-273
We describe here a simple and efficient system of soybean (Glycine max L. Merrill) regeneration through direct somatic embryogenesis by using immature embryonic shoot tips (IEST) as explants.
The cultivar Kaohsiung 10 (cv. K10) used in this study did not show embryogenic response either from mature seed-derived explants
(cotyledon, embryonic tip, leaf, shoot and root) or immature cotyledons. However, it showed a high percentage (55.8%) of somatic
embryo (SEm) formation from the IEST excised 2–3 wk after flowering, thus indicating the crucial roles of type and age of
explants. The IEST put forth primary SEm after 2 mo of culturing on Murashige and Skoog (MS) medium supplemented with 6% sucrose,
164.8 μM 2,4-dichlorophenoxyacetic acid (2,4-D), 5 mM asparagine and 684 μM glutamine. Subsequently, secondary SEm were developed
1 mo after culturing on MS medium containing 123.6 μM 2,4-D and 3% sucrose. Cotyledonary embryos were induced on MS medium
supplemented with 0.5% activated charcoal after 1 mo. The embryos were desiccated for 72–96 h on sterile Petri dishes and
regenerated on hormone-free MS medium. Plantlets with well-developed shoots and roots were obtained within 5–6 mo of culturing
of IEST. The SEm-derived plants were morphologically normal and fertile. Various parameters thought to be responsible for
efficient regeneration of soybean through somatic embryogenesis are discussed. To our knowledge, this is the first report
to employ IEST as explants for successful direct somatic embryogenesis in soybean. 相似文献
916.
Tu Quang Tan Chutian Ge Yuling Mi Yanmei Jin Caiqiao Zhang 《Cell biology international》2010,34(7):769-775
The effect of GS (ginsenosides) on proliferation of chicken GCs (granulosa cells) from prehierarchical SYF (small yellow follicles) was evaluated, and involvement of the PKC (protein kinase C) signalling pathway as well as mRNA expression of cyclins and CDK (cyclin‐dependent kinase) were investigated. Whole SYF or GCs isolated from SYF were cultured in Medium 199 supplemented with 0.5% FCS (fetal calf serum). After 16 h, the cells were challenged with GS alone or in combination with PKC inhibitor H7 or activator PMA (phorbol 12‐myristate 13‐acetate) for 24 h in serum‐free medium. Results showed that in both whole follicles and pure GCs monolayer culture system, GS (0.1–10 μg/ml) significantly increased the number of GCs in SYF in a dose‐dependent manner, and this stimulatory effect was inhibited by H7, but enhanced by PMA. Meanwhile, the PCNA‐LI (proliferating cell nuclear antigen labelling index) of GCs displayed similar changes with the cell number. Mechanism of GS action was further evaluated in cultured GCs separated from SYF. Western blot analysis showed that 10 μg/ml GS increased PKC translocation from cytoplasm to the plasma membrane of the GCs to become the active state. This effect was blocked by H7. Furthermore, GS up‐regulated the expression of cyclin D1/CDK6 and cyclin E/CDK2 mRNAs in GCs; however, inhibition of PKC with H7 attenuated this stimulatory effect. These results indicated that GS could stimulate proliferation of chicken GCs through activated PKC‐involved up‐regulation of cyclin D1/CDK6 and cyclin E/CDK2 genes, subsequently promoting development of the chicken prehierarchical follicles. 相似文献
917.
Raymond C.S. Seet Chung-Yung J. Lee Erle C.H. Lim June J.H. Tan Amy M.L. Quek Wan-Ling Chong Woan-Foon Looi Shan-Hong Huang Huansong Wang Yiong-Huak Chan Barry Halliwell 《Free radical biology & medicine》2010,48(4):560-566
Oxidative damage has been implicated in the pathogenesis of Parkinson disease (PD) but the literature data are confusing. Using products of lipid and DNA oxidation measured by accurate methods, we assessed the extent of oxidative damage in PD patients. The levels of plasma F2-isoprostanes (F2-IsoPs), hydroxyeicosatetraenoic acid products (HETEs), cholesterol oxidation products, neuroprostanes (F4-NPs), phospholipase A2 (PLA2) and platelet activating factor–acetylhydrolase (PAF-AH) activities, urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), and serum high-sensitivity C-reactive protein were compared in 61 PD patients and 61 age-matched controls. The levels of plasma F2-IsoPs, HETEs, 7β-and 27-hydroxycholesterol, 7-ketocholesterol, F4-NPs, and urinary 8-OHdG were elevated, whereas the levels of plasma PLA2 and PAF-AH activities were lower, in PD patients compared to controls (p < 0.05). The levels of plasma F2-IsoPs, HETEs, and urinary 8-OHdG were higher in the early stages of PD (p trend < 0.05). There was a significant negative correlation between the cumulative intake of levodopa and urinary 8-OHdG (r = ?0.305, p = 0.023) and plasma total HETEs (r = ?0.285, p = 0.043). Oxidative damage markers are systemically elevated in PD, which may give clues about the relation of oxidative damage to the onset and progression of PD. 相似文献
918.
Human amniotic epithelial cells (hAECs) are potentially one of the key players in tissue engineering due to their easy availability. The aim of the present study was to develop an optimal isolation and transportation technique, as well as to determine the immunophenotype and epithelial gene expression of hAECs. Amnion was mechanically peeled off from the chorion and digested with trypsin-ethylenediaminetetraacetic acid. The isolated hAECs were cultured in medium containing 10 ng/mL epidermal growth factor until P4. The epithelial gene expression, cell surface antigen and protein expression of hAECs were analyzed by quantitative polymerase chain reaction, flow cytometry and immunocytochemistry. hAECs were also cultured in adipogenic, osteogenic and neurogenic induction media. The best cell yield of hAECs was seen in the digestion of 15 pieces of amnion (2 × 2 cm) and isolated 30 min after digestion with trypsin. F12:Dulbecco's modified eagle medium was the best medium for short term storage at 4 °C. hAECs expressed CD9, CD44, CD73 and CD90, and negligibly expressed CD31, CD34, CD45 and CD117. After serial passage, CK3, CK19 and involucrin gene expressions were upregulated, while p63, CK1 and CK14 gene expressions were downregulated. Sustained gene expressions of integrin β1 and CK18 were observed. At initial culture, these cells might have stem-like properties. However, they differentiated after serial passage. Nonetheless, hAECs have epithelial stem cell characteristics and have the potential to differentiate into corneal epithelial cells. Further investigations are still needed to elucidate the mechanism of differentiation involved and to optimize the culture condition for long term in vitro culture. 相似文献
919.
920.
Fangfang Zhong Hongyan Wang Tianlei Ying Zhong-Xian Huang Xiangshi Tan 《Amino acids》2010,39(2):399-408
Soluble guanylate cyclase (sGC), as a nitric oxide (NO) sensor, is a critical heme-containing enzyme in NO-signaling pathway
of eukaryotes. Human sGC is a heterodimeric hemoprotein, composed of a α-subunit (690 AA) and a heme-binding β-subunit (619
AA). Upon NO binding, sGC catalyzes the conversion of guanosine 5′-triphosphate (GTP) to 3′,5′-cyclic guanosine monophosphate
(cGMP). cGMP is a second messenger and initiates the nitric oxide signaling, triggering vasodilatation, smooth muscle relaxation,
platelet aggregation, and neuronal transmission etc. The breakthrough of the bottle neck problem for sGC-mediated NO singling
was made in this study. The recombinant human sGC β1 subunit (HsGCβ619) and its truncated N-terminal fragments (HsGCβ195 and
HsGCβ384) were efficiently expressed in Escherichia coli and purified successfully in quantities. The three proteins in different forms (ferric, ferrous, NO-bound, CO-bound) were
characterized by UV–vis and EPR spectroscopy. The homology structure model of the human sGC heme domain was constructed, and
the mechanism for NO binding to sGC was proposed. The EPR spectra showed a characteristic of five-coordinated heme-nitrosyl
species with triplet hyperfine splitting of NO. The interaction between NO and sGC was investigated and the schematic mechanism
was proposed. This study provides new insights into the structure and NO-binding of human sGC. Furthermore, the efficient
expression system of E. coli will be beneficial to the further studies on structure and activation mechanism of human sGC. 相似文献