全文获取类型
收费全文 | 75964篇 |
免费 | 2775篇 |
国内免费 | 815篇 |
学科分类
工业技术 | 79554篇 |
出版年
2023年 | 366篇 |
2022年 | 485篇 |
2021年 | 1172篇 |
2020年 | 977篇 |
2019年 | 1161篇 |
2018年 | 2049篇 |
2017年 | 1991篇 |
2016年 | 2154篇 |
2015年 | 1594篇 |
2014年 | 2174篇 |
2013年 | 5058篇 |
2012年 | 3393篇 |
2011年 | 3733篇 |
2010年 | 2992篇 |
2009年 | 3151篇 |
2008年 | 2947篇 |
2007年 | 2996篇 |
2006年 | 2253篇 |
2005年 | 1933篇 |
2004年 | 1859篇 |
2003年 | 1689篇 |
2002年 | 1640篇 |
2001年 | 1542篇 |
2000年 | 1389篇 |
1999年 | 1459篇 |
1998年 | 4400篇 |
1997年 | 3229篇 |
1996年 | 2451篇 |
1995年 | 1588篇 |
1994年 | 1233篇 |
1993年 | 1318篇 |
1992年 | 805篇 |
1991年 | 771篇 |
1990年 | 676篇 |
1989年 | 641篇 |
1988年 | 524篇 |
1987年 | 533篇 |
1986年 | 486篇 |
1985年 | 534篇 |
1984年 | 432篇 |
1983年 | 409篇 |
1982年 | 440篇 |
1981年 | 438篇 |
1980年 | 501篇 |
1979年 | 426篇 |
1978年 | 378篇 |
1977年 | 684篇 |
1976年 | 1214篇 |
1975年 | 371篇 |
1973年 | 388篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Journal of Signal Processing Systems - 相似文献
3.
4.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
5.
Moghadam Seyedeh Hadis Ashofteh Parisa-Sadat Loáiciga Hugo A. 《Water Resources Management》2022,36(9):3181-3205
Water Resources Management - The water evaluation and planning (WEAP) approach and the invasive weed optimization algorithm (IWOA) are herein employed to determine the optimal operating policies in... 相似文献
6.
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials. 相似文献
7.
Prof. Andrea Baier Dr. Anne Kokel Dr. William Horton Ewa Gizińska Dr. Garima Pandey Prof. Ryszard Szyszka Prof. Béla Török Prof. Marianna Török 《ChemMedChem》2021,16(12):1927-1932
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays. 相似文献
8.
Esperanza González-Redondo 《建筑学研究前沿(英文版)》2022,11(2):255-277
The constructive analysis of Madrid's old timber-framed collective courtyard buildings, whether demolished, preserved intact, or enlarged, has achieved the dating of relevant case studies. New parameters established in this study set a chronology based on front sector original projects: old (1737–1788), pre-modern (1788–1847) and modern (1847–1892). The on-site inspection and archival research point to ongoing misleading construction in the historic Southern area. Some modern corralas erected on top of pre-existing buildings confirm the initial hypothesis. First dimensioning rules for new façades and the stability required in old ones before adding new storeys, maintaining the original masonry or double-layered system, are discovered. Undated buildings suggest their possible origin a la malicia and a later transformation into transitional corralas. Finally, an analysis of the demolished courtyards narrows down the dating and points to new conjectures in some preserved by showing their uneven layout, old features, and structural discordances in each sector. 相似文献
9.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
10.
Marcus Reppich Zdeněk Jegla Jakob Grondinger Yaovi Ouézou Azouma Vojtěch Turek 《化学,工程师,技术》2021,93(10):1581-1589
This study investigates the behavior of fruit and vegetable samples during drying. The experimental data are fitted to several different thin-layer drying models. Regression analysis is used to determine model parameters, while statistical indicators serve to evaluate the goodness of fit. The power function model gives the best fit for all examined samples. Based on this model, different drying and heat storage technologies can be combined to ensure that the required residual moisture content of an agricultural product is reached. It is demonstrated on the case of a specific Togolese processing plant that under favorable conditions, fossil fuel consumption can be decreased by 33 %. 相似文献