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101.
杂草科学管理——理论基础与实施途径 总被引:4,自引:0,他引:4
Scientific management of weeds is theoretically based on ecology.The implementation methods incladeIntensifying the weed biology and ecology research, especially those of the heavy weeds;Intensifying the research of developing competition between the crop and the weed;Utilizing a allelopathy the gene engineering and breeding against the weeds;Utilizing allelopathy between the crop and the weed, and utilizing biological and agricultural measurements to control the weeds. 相似文献
102.
目的观察Nogo—p4是否通过与NgR结合的途径对大鼠脊髓来源神经干细胞分化形成双极形星形胶质细胞突起长度产生抑制。方法取4只出生24h内的Wistar大鼠,悬浮培养法培养大鼠脊髓来源的神经干细胞。把神经干细胞分为A、B、C、D四组,A组加入血清,B组加入血清和Nogo—p4,C组神经干细胞经RNA干扰沉默NgR基因后加入血清分化,D组神经干细胞经RNA干扰沉默NgR基因后加入血清和Nogo—p4。分化第7d,GFAP抗体标记星形胶质细胞,使用Image—ProPlus5.0软件测量双极形星形胶质细胞突起长度。结果神经干细胞分化第7d,四组均可形成双极形星形胶质细胞。B组中双极形星形胶质细胞的突起长度明显短于其它各组。A、C、D组中双极形星形胶质细胞的突起长度没有显著差异。结论Nogo—p4经与NgR结合途径显著抑制脊髓来源神经干细胞分化成的双极形星形胶质细胞的突起生长。 相似文献
103.
Relationship Between the Membrane Envelope of Rhizobial Bacteroids and the Plasma Membrane of the Host Cell as Demonstrated by Histochemical Localization of Adenyl Cyclase 总被引:1,自引:1,他引:1 下载免费PDF全文
J. C. Tu 《Journal of bacteriology》1974,119(3):986-991
By using adenyl cyclase as a marker enzyme, the relationship between the membrane envelope of the bacteroids of rhizobia and the plasma membrane of the host cell was demonstrated histochemically. Electron-dense deposits were found on the outer surface of the plasma membrane of the host cell and on the inner surface of the membrane envelopes of the bacteroids, but not in vacuole membranes, endoplasmic reticula, Golgi apparatus, and mitochondrial membranes. The results suggest that the membrane envelopes of the bacteroids are closely related to the host plasma membrane, and that entry of the bacteroids into the cytoplasm is in a manner similar to endocytosis. 相似文献
104.
A physiological role for cyanate-induced carbonic anhydrase in Escherichia coli. 总被引:2,自引:3,他引:2 下载免费PDF全文
M B Guilloton A F Lamblin E I Kozliak M Gerami-Nejad C Tu D Silverman P M Anderson J A Fuchs 《Journal of bacteriology》1993,175(5):1443-1451
Cyanate induces expression of the cyn operon in Escherichia coli. The cyn operon includes the gene cynS, encoding cyanase, which catalyzes the reaction of cyanate with bicarbonate to give ammonia and carbon dioxide. A carbonic anhydrase activity was recently found to be encoded by the cynT gene, the first gene of the cyn operon; it was proposed that carbonic anhydrase prevents depletion of bicarbonate during cyanate decomposition due to loss of CO2 by diffusion out of the cell (M. B. Guilloton, J. J. Korte, A. F. Lamblin, J. A. Fuchs, and P. M. Anderson, J. Biol. Chem. 267:3731-3734, 1992). The function of the product of the third gene of this operon, cynX, is unknown. In the study reported here, the physiological roles of cynT and cynX were investigated by construction of chromosomal mutants in which each of the three genes was rendered inactive. The delta cynT chromosomal mutant expressed an active cyanase but no active carbonic anhydrase. In contrast to the wild-type strain, the growth of the delta cynT strain was inhibited by cyanate, and the mutant strain was unable to degrade cyanate and therefore could not use cyanate as the sole nitrogen source when grown at a partial CO2 pressures (pCO2) of 0.03% (air). At a high pCO2 (3%), however, the delta cynT strain behaved like the wild-type strain; it was significantly less sensitive to the toxic effects of cyanate and could degrade cyanate and use cyanate as the sole nitrogen source for growth. These results are consistent with the proposed function for carbonic anhydrase. The chromosomal mutant carrying cynS::kan expressed induced carbonic anhydrase activity but no active cyanase. The cynS::kan mutant was found to be much less sensitive to cyanate than the delta cynT mutant at a low pCO2, indicating that bicarbonate depletion due to the reaction of bicarbonate with cyanate catalyzed by cyanase is more deleterious to growth than direct inhibition by cyanate. Mutants carrying a nonfunctional cynX gene (cynX::kan and delta cynT cynX::kan) did not differ from the parental strains with respect to cyanate sensitivity, presence of carbonic anhydrase and cyanase, or degradation of cyanate by whole cells; the physiological role of the cynX product remains unknown. 相似文献
105.
In this paper, we consider the problem of interval estimation for the mean of diagnostic test charges. Diagnostic test charge data may contain zero values, and the nonzero values can often be modeled by a log-normal distribution. Under such a model, we propose three different interval estimation procedures: a percentile-t bootstrap interval based on sufficient statistics and two likelihood-based confidence intervals. For theoretical properties, we show that the two likelihood-based one-sided confidence intervals are only first-order accurate and that the bootstrap-based one-sided confidence interval is second-order accurate. For two-sided confidence intervals, all three proposed methods are second-order accurate. A simulation study in finite-sample sizes suggests all three proposed intervals outperform a widely used minimum variance unbiased estimator (MVUE)-based interval except for the case of one-sided lower end-point intervals when the skewness is very small. Among the proposed one-sided intervals, the bootstrap interval has the best coverage accuracy. For the two-sided intervals, when the sample size is small, the bootstrap method still yields the best coverage accuracy unless the skewness is very small, in which case the bias-corrected ML method has the best accuracy. When the sample size is large, all three proposed intervals have similar coverage accuracy. Finally, we analyze with the proposed methods one real example assessing diagnostic test charges among older adults with depression. 相似文献
106.
Short of a complete genomic DNA sequence, sequence tagged sites (STSs) have emerged as major genomic reagents for the genetic
analysis of little-studied ecologically and agriculturally important organisms. Here, we report STS developed for the turkey
(Meleagris gallopavo), guinea fowl (Numidea meleagris), Japanese quail (Coturnix coturnix) and pigeon using primers specific for reference DNA sequences of two chicken (Gallus gallus) genes, aggrecan (agc1) and type X collagen (col10). Additional STSs were also developed for turkey, quail and chicken using primers specific for the human apobec-1 gene. The total length of the STSs developed was 5990, 2522, 4127, 1539 and 6600 bp for the turkey, guinea fowl, Japanese
quail, pigeon and chicken, respectively. Based on splice site consensus GT and AG sequences, four of the seven agc1-based chicken STS appear to contain introns. The human gene-based STSs showed no significant sequence identity with the
reference GenBank sequences. Maximum likelihood, maximum parsimony and neighbour-joining analysis of an agc1-based STS that was common to all five species showed phylogenetic relationships consistent with those previously defined
using mitochondria DNA sequences and nuclear gene restriction maps. Additionally, several putative single nucleotide polymorphisms
(SNPs) were detected within the STSs, including eight in the turkey, two in the quail, and two in the chicken when multiple
sequences were evaluated from each species. This report describes new STSs that are resources for genetic and physical mapping
and genome analysis within and among avian species. These resources should further aid in our understanding of the biology
of agriculturally important but little-studied guinea fowl and turkey.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
107.
Kašparová Jana Lisá Vera Tuček Stanislav Doležal Vladimír 《Neurochemical research》2001,26(8-9):1079-1084
We investigated whether amyloid--peptide (A1–42) has an effect on the elevations of the intracellular concentration of Ca2+ ions ([Ca2+]i) induced by depolarizations of NG108-15 cells and on related Ca2+ channels. A1–42 (10-1000 nM) had no immediate effect on depolarization-induced [Ca2+]i elevations. [Ca2+]i increases were slightly diminished in cells grown in the presence of 100 or 1000 nM A1–42. Nifedipine (1 M) reduced these elevations equally in cells grown in the absence or presence of A1–42. In contrast, the ability of -conotoxin GVIA to diminish the depolarization-induced [Ca2+]i responses became lost in cells grown in the presence of 100 nM A1–42. This indicates that the influx of calcium through the N-type Ca2+ channels was compromised by the chronic exposure of cells to a submicromolar concentration of A1–42, presumably because of impairement of their function or diminished expression. This may be important in the pathogeny of Alzheimer's dementia in view of the pivotal role of N-type Ca2+ channels in neurotransmitter release. 相似文献
108.
Duda D Tu C Qian M Laipis P Agbandje-McKenna M Silverman DN McKenna R 《Biochemistry》2001,40(6):1741-1748
Histidine 64 in human carbonic anhydrase II (HCA II) functions in the catalytic pathway of CO(2) hydration as a shuttle to transfer protons between the zinc-bound water and bulk water. Catalysis of the exchange of (18)O between CO(2) and water, measured by mass spectrometry, is dependent on this proton transfer and was decreased more than 10-fold for H64A HCA II compared with wild-type HCA II. The loss of catalytic activity of H64A HCA II could be rescued by 4-methylimidazole (4-MI), an exogenous proton donor, in a saturable process with a maximum activity of 40% of wild-type HCA II. The crystal structure of the rescued complex at 1.6 A resolution shows 4-MI bound in the active-site cavity of H64A HCA II, through pi stacking interactions with Trp 5 and H-bonding interactions with water molecules. In this location, 4-MI is about 12 A from the zinc and approximates the observed "out" position of His 64 in the structure of the wild-type enzyme. 4-MI appears to compensate for the absence of His 64 and rescues the catalytic activity of the H64A HCA II mutant. This result strongly suggests that the out conformation of His 64 is effective in the transfer of protons between the zinc-bound solvent molecule and solution. 相似文献
109.
The nucleotide sequence of a rat liver glutathione S-transferase subunit cDNA clone 总被引:17,自引:0,他引:17
We have determined the nucleotide sequence of a cloned cDNA derived from liver poly(A) RNA of pentobarbital-treated rats encoding a glutathione S-transferase subunit. This cDNA clone pGTR261 contains one open reading frame of 222 amino acids, a complete 3' noncoding region, and 63 nucleotides in the 5' noncoding region. The cloned DNA hybridizes to rat poly(A) RNA in a tissue-specific fashion, with strong signals to liver and kidney poly(A) RNA(s) of approximately 1100 and approximately 1400 nucleotides in size but little or no hybridization to poly(A) RNAs from heart, lung, seminal vesicles, spleen, or testis under stringent conditions. Our sequence covers the cDNA sequence of pGST94 which contains a partial coding sequence for a liver glutathione S-transferase subunit of Ya size. Comparison of sequences with our earlier clone pGTR112 suggests that there are at least two mRNA species coding for two different subunits of the Ya (Mr = 25,600) subunit family with very limited amino acid substitutions mainly of conserved polarity. The divergent 3' noncoding sequences should be useful molecular probes in differentiating these two different but otherwise very similar subunits in induction and genomic structure analyses. Our results suggest that tissue-specific expression of the glutathione S-transferase subunits represented by the sequences of pGTR261 and pGTR112 may occur at or prior to the level of RNA processing. 相似文献
110.