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991.
Bacillus subtilis or licheniformis facilitated production of soyiru with the best results being given by using both together. Fermentation employing Streptococcus enterococcus was unsuccessful.H.A. Suberu is with the Department of Biological Sciences, Usmanu Danfodiyo University, Sokoto, Nigeria. J.A. Akinyanju is with the Department of Biological Sciences, University of Ilorin, P.M.B. 1515, Ilorin, Nigeria. 相似文献
992.
C. Coronado B. Sánchez-Andújar A. J. Palomares 《World journal of microbiology & biotechnology》1996,12(2):127-136
The extracellular and surface polysaccharides produced by Rhizobium species constitute a composite macromolecular interface between the bacterial cell and its environment. Several of these polysaccharides are involved in the complex series of interactions leading to the establishment of an effective Rhizobium-legume symbiosis. Extracellular heteropolysaccharides (EPSs) are found in culture supernatants, while capsular polysaccharides adhere to the cell surface. Cyclic (1–2)--d glucan is a periplasmic oligosaccharide that has also been found in the culture supernatants of some strains. The lipopolysaccharides (LPSs), which form part of the outer membrane and contain the O-somatic antigens, comprise the other major group of extracellular polysaccharides. In this review we will describe the major Rhizobium extracellular structures and their role in symbiosis with leguminous plants.The authors are with the Departamento de Microbiologia y Parasitologia, Facultad de Farmacia. Universidad de Sevilla, 41012 Sevilla, Spain 相似文献
993.
Piotr Orlewski Vassilios Tsikaris Maria Sakarellos-Daitsiotis Constantinos Sakarellos Ketty P. Soteriadou Michel Marraud Manh Thong Cung 《Letters in Peptide Science》1996,3(5):317-326
Summary The IASRYDQL synthetic octapeptide (250–257) of the Leishmania major surface glycoprotein gp63 efficiently inhibits parasite attachment to the macrophage receptors in in vitro experiments, and the SRYD-containing tetrapeptide mimics antigenically and functionally the RGDS sequence of fibronectin. The conformational properties of the octapeptide were investigated in dimethylsulfoxide (DMSO) with the combined use of NMR data (vicinal coupling constants, nuclear Overhauser effects (NOEs) and temperature coefficient values), molecular modeling by energy minimization and molecular dynamics. The structure is characterized by the high occurrence, exceeding 95%, of the Arg-Asp side-chain-side-chain ionic interaction, which plays a key role in the backbone folding through a distorted type-I -turn involving the Gln256-NH to Arg253-CO hydrogen bond. 相似文献
994.
Pieter H. B. De Visser Willem G. Keltjens Günther R. Findenegg 《Trees - Structure and Function》1996,10(5):301-307
In a pot trial growth and transpiration of 3-year-old Douglas-fir seedlings on an acid, sandy soil was examined at a deficient
(30 kg N ha –
1 year –
1) and an excessive level (120 kg N ha –
1 year –
1) of NH4 application. Dissolved ammonium sulphate was applied to the pots weekly for two growing seasons. In half of the pots a complete
set of other nutrients was applied in optimal proportions to the applied nitrogen. Water supply was optimal and transpiration
was recorded. At the end of the second treatment season irrigation was stopped for 2 weeks during dry and sunny weather. Both
high application of NH4 and additional nutrients increased shoot growth and transpiration demand in the first treatment year. The root system was
smaller at higher N level and this reduced water uptake accordingly. In the second year the combination of high NH4
+ and additional nutrients affected root functioning predominantly due to salinity effects and this seriously decreased water
uptake capacity and shoot water potentials, finally resulting in tree death. Without addition of other nutrients the high
NH4
+ application resulted in a high degree of soil acidification, which damaged the roots, that showed a decrease in water uptake
capacity. At the low NH4 supply level soil acidification was lower, and root functioning was not affected, and the trees recovered quickly from the
imposed drought. Higher needle K and P status depressed transpiration rates at the low NH4 application rate.
Received: 9 January 1995 / Accepted: 18 September 1995 相似文献
995.
Infectivity of preserved Cryptosporidium parvum oocysts for immunosuppressed adult mice 总被引:1,自引:0,他引:1
Shiguang Yang Mark C. Healey Chunwei Du 《FEMS immunology and medical microbiology》1996,13(2):141-145
Abstract The present study was undertaken to determine the infectivity of Cryptosporidium parvum oocysts for immunosup-pressed adult C57BL/6N mice after the oocysts had been stored from 1–48 months at 4°C in 2.5% potassium dichromate. All mice inoculated with oocysts 1–18 months old developed patent infections, while mice inoculated with older oocysts remained uninfected. The prepatent period was extended from 2 to 6 or 7 days as the storage time for oocysts increased. The finding that C. parvum oocysts remain infective for mice for at least 18 months offers important economic and time-saving advantages for investigators who frequently require large numbers of oocysts that must be painstakingly purified from calf manure. 相似文献
996.
Ernesto Nicolás Jordi Bacardit Tina Ferrer Ernest Giralt 《Letters in Peptide Science》1996,2(6):353-362
Summary Short peptides spanning the helicoidal sequences of the uteroglobin monomer (crystal forms P21 and C2221) were synthesized and studied by circular dichroism spectroscopy. None of them showed any secondary structure in the absence of HFIP. However, most peptides achieved a helical conformation when this structuring agent was used, with the exception of the analogue corresponding to the helicoidal fragment 19–24 (helix II, crystal P21). These results indicate that other factors, such as interchain interactions, have to contribute to helix stabilization in the molecule. On the other hand, while peptides corresponding to N- and C-terminal fragments that contain the first and fourth helices of the monomer, respectively (1–14 and 48–70) achieved a -like structure when 10–15% of HFIP was used, this behaviour was not observed when TFE was used. Moreover, substitution of cysteine by -aminobutyric acid at position 3 increased both the helicity of fragment 1–14 and its ability to adopt a -like structure, but the opposite effect was observed for fragment 48–70 when -aminobutyric acid was introduced at position 69. These results indicate that this part of the protein might be sensitive to the chemical environment it is exposed to and that the two cysteine residues at positions 3 and 69 of the monomer could play a different role in the folding process. 相似文献
997.
Kathleen P. Anderson Christine B. Kern Scott C. Crable Jon C. Neumann Jerry B. Lingrel 《Transgenic research》1996,5(4):245-255
Our interest in thecis-acting elements that promote the up-regulation of the globin gene has led to a systematic deletion analysis of portions of the globin gene in the context of the HS2 and globin gene using transgenic mice. In constructs that delete the 5 region to only 265 bp, high-level erythroid-specific expression was observed. Further deletion to 122 bp, however, results in significantly reduced expression levels A substitution of a minilocus control region for the single HS2 site was also produced, resulting in increased globin expression over that seen with the HS2 alone. These results are consistent with the presence of an enhancer-like element between –122 and –265. In addition, a construct in which the entire globin gene promoter was replaced by a thymidine kinase promoter was tested. Interestingly, no expression was detected in these transgenic mice. This may indicate the requirement for an erythroid-specific promoter to drive this gene. Finally, the 3 region of the globin gene was deleted in order to examine the effect of a previously defined 3 enhancer region. With deletion of this region, the expression of the human globin gene in transgenic mice is unchanged relative to the parental constructs. 相似文献
998.
A. Guivarc'h J. C. Caissard A. Azmi T. Elmayan D. Chriqui M. Tepfer 《Transgenic research》1996,5(5):281-288
Among the methods now available to localize the sites of gene expression in plant materials, reporter genes based on thegus (uidA) gene ofEscherichia coli, which encodes a -glucuronidase (E.C. 3.2.1.31; GUS), have been the most widely used during the last ten years. The apparent simplicity of the histochemical GUS assay has been a major factor in the increase in articles usinggus genes. However, over the last four years, there have been occasional reports expressing doubts concerning the specificity of the observed localizations based on discrepancies between results obtained with GUS histochemistry and immunocytochemistry and/orin situ hybridization. This brief review compares the results obtained with immunocytochemistry with those obtained with various GUS substrates for histochemical studies. Certain sources of artefact are discussed, as are the limits that should be imposed on interpretation of GUS histochemistry results at the organ, tissue and cell levels. 相似文献
999.
p21是近年来发现的一类调控细胞增殖的小分子,是依赖周期素的CDK抑制因子.这些蛋白因子可结合cyclin-CDK并抑制其激酶活性从而调节细胞周期p15、p16、p27均属该类分子,他们在G1期限制点及G1/S检查点调控中发挥作用.进一步的研究表明,p21为p53调控,在p53介导的DNA损伤诱发的细胞周期阻断中发挥作用p21在老化细胞中高表达、细胞分化的同时表达,表明其在细胞增殖、分化及老化中发挥调节作用. 相似文献
1000.
利用单克隆抗体免疫磁珠吸附方法分离脐血CD34+细胞,并观察了IL3/GMCSF融合蛋白(PIXY321)对脐血CD34+细胞的刺激作用。PIXY321对脐血CD34+细胞扩增作用大于IL3和GMCSF单独及联合应用。在液体培养条件下,每毫升20ngPIXY321可有效地扩增脐血造血祖细胞,适宜扩增时间为5-8天,扩增后造血祖细胞的数量可达扩增前的8-10倍,从而初步建立了一种简单可行的脐血造血细胞扩增方法。 相似文献