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991.
Acinus is a caspase-3-activated protein required for apoptotic chromatin condensation. 总被引:23,自引:0,他引:23
Apoptosis is defined by several unique morphological nuclear changes, such as chromatin condensation and nuclear fragmentation. These changes are triggered by the activation of a family of cysteine proteases called caspases, and caspase-activated DNase (CAD/DFF40) and lamin protease (caspase-6) have been implicated in some of these changes. CAD/DFF40 induces chromatin condensation in purified nuclei, but distinct caspase-activated factor(s) may be responsible for chromatin condensation. Here we use an in vitro system to identify a new nuclear factor, designated Acinus, which induces apoptotic chromatin condensation after cleavage by caspase-3 without inducing DNA fragmentation. Immunodepletion experiments showed that Acinus is essential for apoptotic chromatin condensation in vitro, and an antisense study revealed that Acinus is also important in the induction of apoptotic chromatin condensation in cells. 相似文献
992.
Expression of the transcription factor deltaFosB in the brain controls sensitivity to cocaine. 总被引:17,自引:0,他引:17
993.
Directional guidance of neuronal migration in the olfactory system by the protein Slit. 总被引:34,自引:0,他引:34
Although cell migration is crucial for neural development, molecular mechanisms guiding neuronal migration have remained unclear. Here we report that the secreted protein Slit repels neuronal precursors migrating from the anterior subventricular zone in the telencephalon to the olfactory bulb. Our results provide a direct demonstration of a molecular cue whose concentration gradient guides the direction of migrating neurons. They also support a common guidance mechanism for axon projection and neuronal migration and suggest that Slit may provide a molecular tool with potential therapeutic applications in controlling and directing cell migration. 相似文献
994.
Structure of the receptor for platelet-derived growth factor helps define a family of closely related growth factor receptors 总被引:185,自引:0,他引:185
Y Yarden J A Escobedo W J Kuang T L Yang-Feng T O Daniel P M Tremble E Y Chen M E Ando R N Harkins U Francke 《Nature》1986,323(6085):226-232
The primary structure of the receptor for platelet-derived growth factor (PDGF), determined by means of cloning a cDNA that encodes the murine pre-PDGF receptor, is closely related to that of the v-kit oncogene product and the receptor for macrophage colony stimulating factor (CSF-1). Common structural features include the presence of long sequences that interrupt the tyrosine-specific protein kinase domains of each molecule. The PDGF and CSF-1 receptors also share a characteristic distribution of extracellular cysteine residues. Ubiquitin is covalently bound to the purified PDGF receptor, the human gene for which is on chromosome 5. 相似文献
995.
无线传感器网络的能量有限是限制其作用的重要因素,因此如何高效使用能源并延长节点寿命成为研究的热点.结合已有算法,提出了一种改进的分簇路由算法,将簇头的选举由原先的随机选举变为基于剩余能量的选举,以平衡网络负载;在数据传输过程中采用多跳的通信方式降低簇节点的通信负载.仿真结果实现了节能、平衡节点能耗、延长网络寿命的目的. 相似文献
996.
Identification of CRE1 as a cytokinin receptor from Arabidopsis 总被引:29,自引:0,他引:29
Inoue T Higuchi M Hashimoto Y Seki M Kobayashi M Kato T Tabata S Shinozaki K Kakimoto T 《Nature》2001,409(6823):1060-1063
Cytokinins are a class of plant hormones that are central to the regulation of cell division and differentiation in plants. It has been proposed that they are detected by a two-component system, because overexpression of the histidine kinase gene CKI1 induces typical cytokinin responses and genes for a set of response regulators of two-component systems can be induced by cytokinins. Two-component systems use a histidine kinase as an environmental sensor and rely on a phosphorelay for signal transduction. They are common in microorganisms, and are also emerging as important signal detection routes in plants. Here we report the identification of a cytokinin receptor. We identified Arabidopsis cre1 (cytokinin response 1) mutants, which exhibited reduced responses to cytokinins. The mutated gene CRE1 encodes a histidine kinase. CRE1 expression conferred a cytokinin-dependent growth phenotype on a yeast mutant that lacked the endogenous histidine kinase SLN1 (ref. 10), providing direct evidence that CRE1 is a cytokinin receptor. We also provide evidence that cytokinins can activate CRE1 to initiate phosphorelay signalling. 相似文献
997.
甘南高寒草地牧场管理的最优控制模型及可持续利用对策研究 总被引:9,自引:2,他引:9
以甘南高寒草地放牧系统为研究对象,运用生物控制论的理论与方法,确定了放牧管理的主要指标,组建了放牧管理的最优控制模式。并根据试验监测结果进行了实例计算与生态经济效益分析,提出了可持续利用的对策与意见。 相似文献
998.
圆柱齿轮传动目标函数优化设计 总被引:1,自引:0,他引:1
朱艳笛 《科技情报开发与经济》2004,14(6):160-161
圆柱齿轮传动是机械传动中应用最为广泛的装置,以其为例建立了用料最小的目标函数的数学模型,并进行了优化设计。该优化模型和优化方案比常规优化更接近实际,而且设计方法简便,易掌握。 相似文献
999.
Liu Y.K. Dong Y. Wang G.H. 《中国科学基金(英文版)》2004,(2):42-44,49
Nanostructured materials have drawn considerable attention because they are promising candidates for nextgeneration electronic and photonic devices with low power consumption[1-5]. A number of methods, such as laser ablation[6], template-induced growth[7], arc discharge [8], vapor transport [9], and molecular-beam epitaxy[10] have been developed to synthesize Si, Ge, MgO,SnO2, GaN, and Ga2O3 nanowires or nanorods[11-15].…… 相似文献
1000.
Comparison of human genetic and sequence-based physical maps 总被引:40,自引:0,他引:40
Yu A Zhao C Fan Y Jang W Mungall AJ Deloukas P Olsen A Doggett NA Ghebranious N Broman KW Weber JL 《Nature》2001,409(6822):951-953
Recombination is the exchange of information between two homologous chromosomes during meiosis. The rate of recombination per nucleotide, which profoundly affects the evolution of chromosomal segments, is calculated by comparing genetic and physical maps. Human physical maps have been constructed using cytogenetics, overlapping DNA clones and radiation hybrids; but the ultimate and by far the most accurate physical map is the actual nucleotide sequence. The completion of the draft human genomic sequence provides us with the best opportunity yet to compare the genetic and physical maps. Here we describe our estimates of female, male and sex-average recombination rates for about 60% of the genome. Recombination rates varied greatly along each chromosome, from 0 to at least 9 centiMorgans per megabase (cM Mb(-1)). Among several sequence and marker parameters tested, only relative marker position along the metacentric chromosomes in males correlated strongly with recombination rate. We identified several chromosomal regions up to 6 Mb in length with particularly low (deserts) or high (jungles) recombination rates. Linkage disequilibrium was much more common and extended for greater distances in the deserts than in the jungles. 相似文献