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91.
津白_3侏儒小鼠(dW~t)是1982年从津白_3纯系小鼠(TA_3)中发现,进而培育成侏的变种。本实验应用免疫细胞化学技术,对dw ̄t小鼠垂体前叶生长激素(GH)细胞进行观察,并根据体视学原理进行定量分析,以探讨dw~t小鼠是否存在垂体发育缺陷。实验结果显示,dw~t小鼠GH细胞的体积密度(Vv)和数密度(Nv)值均低于正常对照组,P<0.01~0.001。表明dw~t小鼠由于垂体前叶GH细胞数量减少,导致GH分泌不足,从而形成侏儒。 相似文献
92.
岩豆凝集素的圆二色性与生物学活性关系的研究 总被引:1,自引:0,他引:1
岩豆凝集素(MDL)的远紫外圆二色性谱(CD谱)显示216-217nm处的单一负峰。此时MDL分子含有16.2%的α螺旋,46.3%的β折叠和37.5%的无规卷曲。pH9.0时负峰红移至220nm,且在217-222nm处的峰值几乎相同;在20-40℃范围内,CD谱的变化甚微;60℃时谱峰蓝移;在80℃或100℃时,212nm处出现一大负峰。1mol/L或2mol/L脲时,MDL的CD谱已发生明显变化,二级结构单元也有变化,凝集兔红细胞的活性也随之减弱;随脲浓度的增加,MDL的谱峰蓝移,最终在212nm处出现大负峰。当胍浓度为0.75mol/L时,MDL的CD谱即有明显变化和活性丧失;胍浓度继续增加,CD谱逐渐成为特征的无规卷曲的谱形。在pH9.0、温度超过80℃、脲或胍浓度分别高于2mol/L和0.75mol/L时,MDL的CD谱发生显著变化的同时,其凝集兔红细胞的生物学活性全部丧失,分子的二级结构单元也发生很大改变。 相似文献
93.
Zhuang XC Sun YZ Cui J Zhu JM Jiang C Xiang QL Li CS 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1994,1(1):P61-P63
In the environment of microgravity, the disused atrophy of skeletal muscle, especially leg's muscle, would occur. The three purposes of this study were: 1. To observe the dynamic changes of disused atrophy of skeletal muscle under simulated weightlessness; 2. To approach the mechanism of disused atrophy of muscle; 3. To approach the countermeasures for reducing the degree of atrophy of muscle. 相似文献
94.
Conrad GW Luer CA Paulsen AQ Funderburgh JL 《Transactions of the Kansas Academy of Science. Kansas Academy of Science》1993,96(1-2):62-68
Morphogenesis of the clearnose skate, Raja eglanteria, was not significantly inhibited as a result of 7 days of exposure to 1-2 mM selenate in the sea water during Days 59-69 of embryonic development (hatching would normally have occurred at 82 +/- 4 days of incubation). Although corneal transparency appeared normal in the eye, preliminary measurements of the thickness of Bowman's layer of the cornea suggested that it was significantly thinner in the corneas of embryos exposed to 1-2 mM selenate. Selenate is an ion reported to inhibit sulfation of glycosaminoglycans in connective tissue. 相似文献
95.
Induction of B-A transitions of deoxyoligonucleotides by multivalent cations in dilute aqueous solution. 总被引:4,自引:1,他引:3 下载免费PDF全文
Circular dichroism (CD) spectra of d(CCCCGGGG) in the presence of Co(NH3)6(3+) are very similar to spectra of r(CCCCGGGG). In contrast, B-form characteristics are observed for d(CCCCGGGG) in the presence of Na+ and Mg2+, even at high salt concentrations. Spermidine induces modest changes of the CD of d(CCCCGGGG). The NMR chemical shifts of the nonexchangeable protons of d(CCCCGGGG) in the absence and presence of Co(NH3)6(3+) were assigned by proton two-dimensional (2D) NOESY and COSY measurements. The chemical shifts of the GH8 protons of d(CCCCGGGG) move upfield upon titration with Co(NH3)6Cl3. The sums of the sugar H1' coupling constants decrease with added Co(NH3)6Cl3. Cross peak intensities in the 2D proton NOESY spectra show a transformation from B-DNA to A-DNA characteristics upon the addition of Co(NH3)6Cl3. The temperature-dependent 59Co transverse and longitudinal relaxation rates demonstrate that Co(NH3)6(3+) is site-bound to the oligomer. Such localization is not a general feature of Co(NH3)6(3+) binding to oligonucleotides. 59Co NMR relaxation and CD measurements demonstrate chiral discrimination by d(CCCCGGGG) for the two stereoisomers of Co(en)3(3+). Both stereoisomers bind tightly as judged by 59Co NMR, and both cause large (but nonequivalent) changes in the CD of this oligomer. 相似文献
96.
The effect of hydration on the dynamics of trimethoprim bound to dihydrofolate reductase. A deuterium NMR study. 下载免费PDF全文
To determine the effect of hydration on the dynamics of a protein complex, we used deuterium nuclear magnetic resonance (NMR) techniques to examine a trimethoprim (TMP)/E. coli dihydrofolate reductase (DHFR) complex in its lyophilized, partially hydrated, polycrystalline, and ammonium sulfate-precipitated states. The results indicate that TMP is rigid in the lyophilized powder state. The dynamic behavior could be restored by partial rehydration. At 30 wt% hydration the deuterium spectrum of the partially hydrated sample was indistinguishable from that of the polycrystalline and ammonium sulfate-precipitated samples, suggesting that the structure of the protein/TMP complex is similar in the three physical states. Furthermore, we found that the para- and meta-methoxyl groups have very different dynamical behavior. 相似文献
97.
The localization of neuropeptide Y (NPY) and atrial natriuretic peptide (ANP) in the endothelial cells of human umbilical blood vessels was studied using the pre-embedding peroxidase-antiperoxidase (PAP) technique for electron microscopy and avidin-biotin-complex (ABC) immunostaining for endothelial cells cultured from umbilical vein. Subpopulations of NPY- and ANP-immunoreactive endothelial cells were present in term umbilical vein and artery. The umbilical vein contained more positive cells than the artery. The percentage of NPY- and ANP-immunoreactive umbilical vein cells in culture was 32% and 44%, respectively, out of a total of 3013 cells examined. The possibility that these potent vasoactive substances located in the endothelial cells of the non-innervated umbilical vessels are involved in the local regulation of blood flow is discussed. 相似文献
98.
Yu-xiao Wang Wei Dai Yi-zhou Li Zi-yao Wu Ya-qi Kan Huai-cai Zeng Qing-zhi He 《Journal of biochemical and molecular toxicology》2023,37(3):e23273
Bisphenol S (BPS) is an environmental endocrine disruptor widely used in industrial production. BPS induces oxidative stress and exhibits male reproductive toxicity in mice, but the mechanisms by which BPS impairs steroid hormone synthesis are not fully understood. Nuclear factor erythroid 2-related factor 2(Nrf2)/HO-1 signaling is a key pathway in improving cellular antioxidant defense capacities. Therefore, this study explored the effects of exposure to BPS on testosterone synthesis in adult male mice and its mechanisms with regard to the Nrf2/HO-1 signaling pathway. Adult male C57BL/6 mice were orally exposed to BPS (2, 20, and 200 mg/kg BW) with sesame oil as a vehicle (0.1 ml/10 g BW) per day for 28 consecutive days. The results showed that compared with the control group, serum testosterone levels were substantially reduced in the 20 and 200 mg/kg BPS treatment groups, and testicular testosterone levels were reduced in all BPS treatment groups. These changes were accompanied by a prominent decrease in the expression levels of testosterone synthesis-related enzymes (STAR, CYP11A1, CYP17A1, HSD3B1, and HSD17B3) in the mouse testis. In addition, BPS induced oxidative stress in the testis by upregulating the messenger RNA and protein levels of Keap1 and downregulating the levels of Nrf2, HO-1, and downstream antioxidant enzymes (CAT, SOD1, and Gpx4). In summary, our results indicate that exposure of adult male mice to BPS can inhibit Nrf2/HO-1 signaling and antioxidant enzyme activity, which induces oxidative stress and thereby may impair testosterone synthesis in testicular tissues, leading to reproductive damage. 相似文献
99.
100.
Le Zhang Yi-Wei Huang Jia-Lin Huang Ji-Dong Ya Meng-Qing Zhe Chun-Xia Zeng Zhi-Rong Zhang Shi-Bao Zhang De-Zhu Li Hong-Tao Li Jun-Bo Yang 《Molecular ecology resources》2023,23(2):424-439
Cymbidium is an orchid genus that has undergone rapid radiation and has high ornamental, economic, ecological and cultural importance, but its classification based on morphology is controversial. The plastid genome (plastome), as an extension of plant standard DNA barcodes, has been widely used as a potential molecular marker for identifying recently diverged species or complicated plant groups. In this study, we newly generated 237 plastomes of 50 species (at least two individuals per species) by genome skimming, covering 71.4% of members of the genus Cymbidium. Sequence-based analyses (barcoding gaps and automatic barcode gap discovery) and tree-based analyses (maximum likelihood, Bayesian inference and multirate Poisson tree processes model) were conducted for species identification of Cymbidium. Our work provides a comprehensive DNA barcode reference library for Cymbidium species identification. The results show that compared with standard DNA barcodes (rbcL + matK) as well as the plastid trnH-psbA, the species identification rate of the plastome increased moderately from 58% to 68%. At the same time, we propose an optimized identification strategy for Cymbidium species. The plastome cannot completely resolve the species identification of Cymbidium, the main reasons being incomplete lineage sorting, artificial cultivation, natural hybridization and chloroplast capture. To further explore the potential use of nuclear data in identifying species, the Skmer method was adopted and the identification rate increased to 72%. It appears that nuclear genome data have a vital role in species identification and are expected to be used as next-generation nuclear barcodes. 相似文献