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81.
Peter J. Sims 《生物化学与生物物理学报:生物膜》1983,732(3):541-552
The number of membrane-bound terminal complement proteins (C5b-9) required to generate a functional pore in the human erythrocyte membrane ghost has been determined. Resealed erythrocyte ghost membranes (ghosts) were treated with human complement proteins C5b6, C7, 131I-C8, and 125I-C9 under non-lytic conditions. Following C5b-9 assembly, sucrose-permeant ghosts were separated from C5b-9 ghosts that remained impermeant to sucrose by centrifugation over density barriers formed of 43% (w/v) sucrose. Analysis of 131I-C8 and 125I-C9 bound to sucrose-permeant and sucrose-impermeant subpopulations of C5b-9 ghosts revealed: 1. Sucrose-permeant C5b-9 ghosts show increased uptake of both 131I-C8 and 125I-C9 as compared to ghosts that remain impermeant to sucrose. Ghosts with less than 300 molecules 131I-C8 bound remain impermeant to sucrose, irrespective of the total C9 input, or, the multiplicity of C9 uptake by membrane C5b-8. 2. In the presence of excess 125I-C9, the ratio of 125I-C9/131I-C8 bound to membrane C5b67 is 3.2 ± 0.8 (mean ± 2 S.D.), suggesting an average stoichiometry of 3 C9 per C5b-8. Under these conditions, the ratio of 125I-C9/131I-C8 bound to sucrose-permeant ghosts (3.3 ± 0.7) does not significantly differ from the ratio bound to sucrose-impermeant ghosts (2.9 ± 0.6). 3. With limiting C9 input, the threshold of total C5b-8 uptake required for sucrose permeability increases significantly above 300 per cell when the ratio of bound 125I-C9/131I-C8 is decreased below unity. In the complete absence of C9, 11 700 C5b-8 complexes are bound to sucrose-permeant ghosts. It is concluded that more than 300 C5b-9 complexes must bind to the human erythrocyte to form a sucrose-permeant lesion. Although the binding of one C9 per C5b-8 is critical to the pore-forming activity of these proteins, the binding of additional molecules of C9 to each complex (C9/C8 > 1) does not significantly alter the threshold of total C5b-9 uptake required for lesion formation. 相似文献
82.
Annie Giraud Simone Bouchilloux 《Biochemical and biophysical research communications》1983,111(2):353-359
The synthesis of glycosaminoglycans (GAGs) was investigated in porcine thyroid cells under the influence or not of thyrotropin. After labelling with [3H] glucosamine and [35S] , enriched GAG-fractions prepared from culture media, cells, and eventually substrate adhering materials, were analyzed by cellulose acetate electrophoresis combined with specific degradations. They comprised heparan sulfate and hyaluronic acid together with an unknown sulfated component labile to endo-β-galactosidase. Whereas global labellings of newly made GAGs were not significantly modified by thyrotropin, we reproducibly observed with the hormone a substantial increase in the proportion of hyaluronic acid [3H] label and, when cells organized into follicles, of the proportion of cell-associated [3H] GAGs. This system thus offers an interesting model to study how the responsiveness to an hormone and the reorganization that follows might implicate specific glycoconjugates. 相似文献
83.
Ginette Pauly Abdelhamid Yani Louis Piovetti Colette Bernard-Dagan 《Phytochemistry》1983,22(4):957-959
The essential oils of the leaves of Cupressus dupreziana and Cupressus sempervirens were compared. The composition of the hydrocarbon fraction showed a great similarity between the two species. 相似文献
84.
Analysis of the biological effects of specific DNA alkylations by simple alkylating agents is complicated by the variety of sites involved. It is, therefore, of value to be able to incorporate into cellular DNA nucleosides alkylated in a single position, e.g., O6-methyldeoxyguanosine. Such cellular incorporation is particularly difficult to achieve because this nucleoside is rapidly demethylated by adenosine deaminase. We have attempted to achieve such incorporation into the DNA of V79 cells by using coformycin, an inhibitor of adenosine deaminase, and by forcing the cells to depend on exogenous purines by the use of medium containing aminopterin. The DNA of V79 cells exposed to O6-methyl-[8-3H]deoxyguanosine (2.4 μM, sp. act. 14 500 Ci/mole) showed an incorporation level of 4 × 10−8 nucleotides. When 1000-fold higher concentrations were employed (3–15 mM, sp. act. 1.6 Ci/mole), significant cytotoxicity and inhibition of DNA synthesis was observed. However, because it was not economically feasible to administer high specific activity O6-methyldeoxyguanosine to the cells at these concentrations, we could not determine the amount of labeled nucleoside incorporated into DNA. Examination of the frequency of 6-thioguanine-resistant cells in these treated populations showed no significant increase above the background level. Comparison of the cytotoxic effect of O6-methyldeoxyguanosine with deoxyadenosine showed that the toxicity induced by O6-methyldeoxyguanosine could have resulted from mimicry of deoxyadenosine, rather than by incorporation of the alkylated nucleoside itself. 相似文献
85.
An examination of the essential oil of myrrh from Commiphora molmol has permitted the identification of 1(10)Z,4Z-furanodiene-6-one, 2-meth 相似文献
86.
Z. Krupa 《Photosynthesis research》1983,4(3):229-239
Thylakoid membranes obtained from bean chloroplasts treated with bean galactolipase or phospholipase A2 (from Crotalus terr. terr.) showed marked changes in their polypeptide patterns when separated on SDS-PAGE. The obtained results have been discussed with regard to the relationship between chloroplast lipids and polypeptides originating from chlorophyll-protein complexes of bean thylakoids. A coexistence between galactolipids and the peripheral antennae in PS I complex and LHCP3 as well as a conspicuous role of phospholipids in PSI and PSII centre chlorophyll-protein complexes has to be underlined.Abbreviations CP1
chlorophyll a-protein complex of PSI
- CPa
chlorophyll a-protein complex of PSII
- D10
digitonin subchloroplast particles enriched in PSII
- D144
digitonin subchloroplast particles enriched in PSI
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- LHCP1–3
light harvesting chlorophyll a/b protein complexes
- PAGE
polyacrylamide gel electrophoresis
- PSI
photosystem I
- PSII
photosystem II
- SDS
sodium dodecyl sulphate
- TCA
trichloroacetic acid
- Tricine
N-Tris-(hydroxymethyl)-methylglycine
- Tris
Tris-(hydroxymethyl)-aminomethan 相似文献
87.
Michael Ready Sandra Bird Gail Rothe J.D. Robertus 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(1):19-28
It has been known for some time that pokeweed antiviral protein acts by enzymatically inhibiting protein synthesis on eucaryotic ribosome systems. The site of this action is known to be the ribosome itself. In this paper we show that the pokeweed antiviral protein reaction against ribosomes is a strong function of salt concentrations, where 160 mM K+ and 3 mM Mg2+ retards the reaction, while 20 mM K+ and 2 mM Mg2+ allows maximum reaction rate. It is also shown, however, that an unidentified protein in the postribosomal supernatant solution, together with ATP, allows the ribosome to be attacked even in the presence of high salt. Kinetic analysis of the antiviral protein reaction has been carried out under both sets of conditions, and reveals that the turnover number for the enzyme is about 300–400 mol/mol per min. in each case. The Km for ribosomes is 1 μM in the presence of low salt and 0.2 μM at higher salt in the presence of postribosomal supernatant factors plus ATP. The antiviral protein reaction is also shown to be pH dependent and is controlled by a residue with pKa value of approx. 7.0, apparently a histidine. Stoichiometric reaction of the enzyme with iodoacetamide results in a significant loss of antiribosomal activity. 相似文献
88.
SYNOPSIS. Media have been developed for axenic cultivation of 10 strains belonging to 7 species of small marine ciliates. A medium containing cerophyl extract, proteose peptone, trypticase, yeast nucleic acid, biotin, calcium pantothenate folic acid, nicotinamide, pyridoxal HCl, riboflavin, thiamine HCl, and DL-thioctic acid in sea water supports the growth of Uronema nigricans strains Pc and 34/2, Parauronema virginiatum strains 2/1 and 19/1, Miamiensis avidus strains Ma and 19/3, Miamiensis sp. strain 1/1, a strain of "G" ciliate, and strains 33/8 and 34/7 of 2 unidentified species. By substituting a mixture of asolecithin, cephalin, and Tween 80 for cerophyl in the medium, luxurious growth of all except the strains of the 2 unidentified species can be obtained. A defined medium consisting of 18 amino acids, 5 purine derivatives, 8 vitamins, asolecithin, cephalin, and Tween 80 in synthetic sea water also has been developed for 6 of the strains: M. avidus Ma and 19/3, Miamiensis sp. 1/1, P. virginiatum 2/1 and 19/1, and U. nigricans Pc. In general the ciliates grow best at pH 7.2 in the dark at 27 C in media containing sea water of density = 1.015. Under these conditions maximum populations are reached in 4–5 days and range from several hundred thousand to 3 or 4 × 106 depending upon the strain. Electronmicroscopic observations for the presence of endosymbiotes gave negative results. 相似文献
89.
Masahiro Miyazaki Yasunori Suzuki Munehiro Oda Akira Kawai Liyan Bai Jiro Sato 《In vitro cellular & developmental biology. Plant》1989,25(9):839-848
Summary For serum-free primary culture of adult rat hepatocytes, a synthetic medium DM-160 and rat-tail collagen were selected for
the basal medium and for the culture substratum, respectively. Barbiturates, such as phenobarbital and 1-ethyl-5-isobutylbarbiturate,
efficiently supported survival of hepatocytes and maintained their morphologic features at lower concentrations under the
serum-free conditions than under the serum-supplemented conditions. However, the hepatocyte survival rates under the serum-free
conditions were lower than those under the serum-supplemented conditions in the presence or absence of barbiturates. Supplementation
of the basal medium with a combination of five groups of factors (5Fs), such as eight amino acids (Ala, Arg, Gly, Ile, Met,
Phe, Pro, and Trp), two unsaturated fatty acids (linoleate and oleate), a protease inhibitor (aprotinin), three vitamins (A,
C, and E), and five trace elements (Mn, Fe, Cu, Zn, and Se), improved the hepatocyte survival under the serum-free conditions
in the presence or absence of barbiturates. In other words, the serum could be completely substituted by the 5Fs. Hepatocyte
cultures maintained in the 5Fs-suppelemented basal medium showed excellent induction of tyrosine aminotransferase activity
in response to dexamethasone in the presence or absence of barbiturates. The efficiency of the 5Fs-supplemented basal medium
for maintaining hepatocytes was not inferior to those of other media in common use with hepatocytes, such as Williams' medium
E and Waymouth's medium MB-752/1. In conclusion, maintenance of functional hepatocytes in serum-free primary culture could
be improved by use of the new medium preparation (the 5Fs-supplemented DM-160) in the presence of barbiturates.
This work was supported by a grant no. 61771923 from the Ministry of Education, Science and Culture of Japan. 相似文献
90.
Katrin Engelmann Peter Friedl 《In vitro cellular & developmental biology. Plant》1989,25(11):1065-1072
Summary Long-term cultivation of human corneal endothelial cells (HCEC) was optimized with respect to different components of the
culture system: 25 different nutrient media, different sera, 6 mitogens and various substrates were tested in their ability
to influence clonal growth and morphology of HCEC. F99, a 1∶1 mixture of the two media M199 and Ham’s F12, was the most effective
basal medium in promoting clonal growth of HCEC. Among various sera, human serum and fetal bovine serum showed optimal growth
promoting activities in combination with F99, whereas newborn bovine serum (NBS) was by far superior for the development of
a typically corneal endothelial morphology. Crude fibroblast growth factor (FGF), or alternatively endothelial cell growth
supplement, was absolutely essential for clonal growth of HCEC at low serum concentrations, for example 5% NBS. Formation
of a monolayer with a morphology similar to corneal endothelium in vivo was observed only on culture dishes coated with basal
membrane components such as collagen type IV, laminin, or fibronectin. The most pronounced effect on morphologic appearance
was obtained by culturing the cells on the extracellular matrix (ECM) produced by bovine corneal endothelial cells. Moreover,
ECM could substitute for crude FGF in clonal growth assays. 相似文献