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871.
Zhu G Zhai P Liu J Terzyan S Li G Zhang XC 《Nature structural & molecular biology》2004,11(10):975-983
Rab5 is a small GTPase that regulates early endosome fusion. We present here the crystal structure of the Rab5 GTPase domain in complex with a GTP analog and the C-terminal domain of effector Rabaptin5. The proteins form a dyad-symmetric Rab5-Rabaptin5(2)-Rab5 ternary complex with a parallel coiled-coil Rabaptin5 homodimer in the middle. Two Rab5 molecules bind independently to the Rabaptin5 dimer using their switch and interswitch regions. The binding does not involve the Rab complementarity-determining regions. We also present the crystal structures of two distinct forms of GDP-Rab5 complexes, both of which are incompatible with Rabaptin5 binding. One has a dislocated and disordered switch I but a virtually intact switch II, whereas the other has its beta-sheet and both switch regions reorganized. Biochemical and functional analyses show that the crystallographically observed Rab5-Rabaptin5 complex also exists in solution, and disruption of this complex by mutation abrogates endosome fusion. 相似文献
872.
Chromatographic and electrophoretic methods for pharmaceutically active compounds in Rhododendron dauricum 总被引:1,自引:0,他引:1
Cao Y Chu Q Ye J 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2004,812(1-2):231-240
In this review, chemical constituents present in Rhododendron dauricum L. were briefly surveyed, and the methods of pretreatment of this plant prior to analysis were also summarized. The analysis methods reported for determining pharmaceutically active compounds in R. dauricum L. include gas chromatography with mass spectrscopy, thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). In addition, both advantages and disadvantages of the above methods were mentioned. 相似文献
873.
Expression of a modified Cry1Ie gene in E. coli and in transgenic tobacco confers resistance to corn borer 总被引:1,自引:0,他引:1
Liu YJ Song FP He KL Yuan Y Zhang XX Gao P Wang JH Wang GY 《Acta biochimica et biophysica Sinica》2004,36(4):309-313
The wild-type Crylle gene from Bacillus thuringiensis was modified for its efficient expression in transgenic plants. Modified Crylle gene (designated as Cryllem) was cloned into prokaryotic expressionvector pET28b and its expression in E.coli was confirmed by SDS-PAGE analysis. Bioassays using crude expression products in E.coli revealed that CrylIem protein had a similar toxicity to corn borer as wild-type CrylIe. CrylIem gene was then inserted downstream of the maize ubiquitin-1 promoter in plant expression vector p3301. Transgenic tobacco plants carrying Cryllem showed insecticidal activity against corn borer. 相似文献
874.
Spider venoms are complex mixtures of neurotoxicpeptides, proteins and low molecular mass organicmolecules. Their neurotoxic activity is due to the interac-tion of the venom components with cellular receptors, inparticular ion channels. Spider venoms have… 相似文献
875.
876.
Volodymyr Dvornyk Ji-Rong Long Dong-Hai Xiong Peng-Yuan Liu Lan-Juan Zhao Hui Shen Yuan-Yuan Zhang Yong-Jun Liu Sonia Rocha-Sanchez Peng Xiao Robert R Recker Hong-Wen Deng 《BMC genetics》2004,5(1):1-15
Background
Public SNP databases are frequently used to choose SNPs for candidate genes in the association and linkage studies of complex disorders. However, their utility for such studies of diseases with ethnic-dependent background has never been evaluated.Results
To estimate the accuracy and completeness of SNP public databases, we analyzed the allele frequencies of 41 SNPs in 10 candidate genes for obesity and/or osteoporosis in a large American-Caucasian sample (1,873 individuals from 405 nuclear families) by PCR-invader assay. We compared our results with those from the databases and other published studies. Of the 41 SNPs, 8 were monomorphic in our sample. Twelve were reported for the first time for Caucasians and the other 29 SNPs in our sample essentially confirmed the respective allele frequencies for Caucasians in the databases and previous studies. The comparison of our data with other ethnic groups showed significant differentiation between the three major world ethnic groups at some SNPs (Caucasians and Africans differed at 3 of the 18 shared SNPs, and Caucasians and Asians differed at 13 of the 22 shared SNPs). This genetic differentiation may have an important implication for studying the well-known ethnic differences in the prevalence of obesity and osteoporosis, and complex disorders in general.Conclusion
A comparative analysis of the SNP data of the candidate genes obtained in the present study, as well as those retrieved from the public domain, suggests that the databases may currently have serious limitations for studying complex disorders with an ethnic-dependent background due to the incomplete and uneven representation of the candidate SNPs in the databases for the major ethnic groups. This conclusion attests to the imperative necessity of large-scale and accurate characterization of these SNPs in different ethnic groups. 相似文献877.
Novak V Yang AC Lepicovsky L Goldberger AL Lipsitz LA Peng CK 《Biomedical engineering online》2004,3(1):39
Background
This study evaluated the effects of stroke on regulation of cerebral blood flow in response to fluctuations in systemic blood pressure (BP). The autoregulatory dynamics are difficult to assess because of the nonstationarity and nonlinearity of the component signals.Methods
We studied 15 normotensive, 20 hypertensive and 15 minor stroke subjects (48.0 ± 1.3 years). BP and blood flow velocities (BFV) from middle cerebral arteries (MCA) were measured during the Valsalva maneuver (VM) using transcranial Doppler ultrasound.Results
A new technique, multimodal pressure-flow analysis (MMPF), was implemented to analyze these short, nonstationary signals. MMPF analysis decomposes complex BP and BFV signals into multiple empirical modes, representing their instantaneous frequency-amplitude modulation. The empirical mode corresponding to the VM BP profile was used to construct the continuous phase diagram and to identify the minimum and maximum values from the residual BP (BPR) and BFV (BFVR) signals. The BP-BFV phase shift was calculated as the difference between the phase corresponding to the BPR and BFVR minimum (maximum) values. BP-BFV phase shifts were significantly different between groups. In the normotensive group, the BFVR minimum and maximum preceded the BPR minimum and maximum, respectively, leading to large positive values of BP-BFV shifts.Conclusion
In the stroke and hypertensive groups, the resulting BP-BFV phase shift was significantly smaller compared to the normotensive group. A standard autoregulation index did not differentiate the groups. The MMPF method enables evaluation of autoregulatory dynamics based on instantaneous BP-BFV phase analysis. Regulation of BP-BFV dynamics is altered with hypertension and after stroke, rendering blood flow dependent on blood pressure.878.
Anti-AIDS agents. Part 56: Synthesis and anti-HIV activity of 7-thia-di-O-(-)-camphanoyl-(+)-cis-khellactone (7-thia-DCK) analogs 总被引:1,自引:0,他引:1
Chen Y Zhang Q Zhang B Xia P Xia Y Yang ZY Kilgore N Wild C Morris-Natschke SL Lee KH 《Bioorganic & medicinal chemistry》2004,12(24):67-6387
Two thia-DCK analogs (3a,b) were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. Compound 3a showed potent anti-HIV activity with an EC50 value of 0.14 μM and a therapeutic index of 1110. However, the corresponding 6-tert-butyl-substituted compound (3b) showed no suppression. The bioassay results indicated that thia-DCK analogs merit attention as potential HIV-1 inhibitors. 相似文献
879.
Cloning and functional analysis of a cDNA encoding Ginkgo biloba farnesyl diphosphate synthase 总被引:3,自引:0,他引:3
Farnesyl diphosphate synthase (FPS; EC2.5.1.1/EC2. 5.1.10) catalyzes the synthesis of farnesyl diphosphate, and provides precursor for biosynthesis of sesquiterpene and isoprenoids containing more than 15 isoprene units in Ginkgo biloba. Here we report the cloning, characterization and functional analysis of a new cDNA encoding FPS from G. biloba. The full-length cDNA (designated GbFPS) had 1731 bp with an open reading frame of 1170 bp encoding a polypeptide of 390 amino acids. The deduced GbFPS was similar to other known FPSs and contained all the conserved regions of trans-prenyl chain-elongating enzymes. Structural modeling showed that GbFPS had the typical structure of FPS, the most prominent feature of which is the arrangement of 13 core helices around a large central cavity. Southern blot analysis revealed a small FPS gene family in G. biloba. Expression analysis indicated that GbFPS expression was high in roots and leaves, and low in stems. Functional complementation of GbFPS in an FPS-deficient strain confirmed that GbFPS mediates farnesyl diphosphate biosynthesis. 相似文献
880.
Liu K Zheng B Hong H Jiang C Peng R Peng J Yu Z Zheng J Yang H 《In vitro cellular & developmental biology. Animal》2004,40(10):312-317
Summary Selection for resistance against Bacillus thuringiensis (Bt) Cry1Ac10 in the Trichoplusia ni (Hübner) cell line BTI-TN-5B1-4 (TnH5) was tested, and the development of resistance in the selected cells was like a S-form
curve. Monitoring at the Cry1Ac10 50th challenge, the resistance ratio was 1, 294-fold as many as that of initial cells. But
the resistance to Cry1Ac10 declined gradually when the selection was relaxed. The resistance declined rapidly at the low level
of resistance and slowly at the high level of resistance. This resistant cell had high resistance to all the tested solubilized
trypsin-treated mixture of crystal multitoxins of B. thuringiensis subsp. aizawai GC-91, an engineering bacterium of Bt, B. thuringiensis subsp. aizawai HD-133 and B. thuringiensis subsp. kurstaki HD-1, and low cross-resistance (19.7-fold) to activated Cry1C. Both N-acetyl-d-galactosamine (GalNAc) and tunicamycin did not inhibit the toxicity of Cry1Ac10 to the susceptible TnH5 cells. Comparison
of the total proteins of the selected resistant cells with that of the nonselected susceptible cells by two-dimensional electrophoresis
analysis showed that were obvious differences among the 11 protein expression. These results strongly suggest that there exists
an unknown mechanism of resistance in the cell line that was different from the reported mechanisms in insects. 相似文献