全文获取类型
收费全文 | 299031篇 |
免费 | 1643篇 |
国内免费 | 327篇 |
专业分类
化学 | 137559篇 |
晶体学 | 4662篇 |
力学 | 16899篇 |
综合类 | 3篇 |
数学 | 42201篇 |
物理学 | 99677篇 |
出版年
2021年 | 3132篇 |
2020年 | 3464篇 |
2019年 | 4252篇 |
2018年 | 6273篇 |
2017年 | 6486篇 |
2016年 | 8009篇 |
2015年 | 3577篇 |
2014年 | 6927篇 |
2013年 | 12172篇 |
2012年 | 10231篇 |
2011年 | 11900篇 |
2010年 | 10047篇 |
2009年 | 10170篇 |
2008年 | 11462篇 |
2007年 | 11277篇 |
2006年 | 10048篇 |
2005年 | 8666篇 |
2004年 | 8410篇 |
2003年 | 7801篇 |
2002年 | 8085篇 |
2001年 | 7678篇 |
2000年 | 6064篇 |
1999年 | 4493篇 |
1998年 | 4271篇 |
1997年 | 4130篇 |
1996年 | 3744篇 |
1995年 | 3298篇 |
1994年 | 3372篇 |
1993年 | 3379篇 |
1992年 | 3383篇 |
1991年 | 3787篇 |
1990年 | 3790篇 |
1989年 | 3800篇 |
1988年 | 3548篇 |
1987年 | 3630篇 |
1986年 | 3320篇 |
1985年 | 3854篇 |
1984年 | 4084篇 |
1983年 | 3488篇 |
1982年 | 3689篇 |
1981年 | 3375篇 |
1980年 | 3133篇 |
1979年 | 3621篇 |
1978年 | 3687篇 |
1977年 | 3856篇 |
1976年 | 3929篇 |
1975年 | 3672篇 |
1974年 | 3529篇 |
1973年 | 3688篇 |
1972年 | 3180篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
E. A. Andrianova V. D. Davidenko V. F. Tsibulskiy S. V. Tsibulskiy 《Physics of Atomic Nuclei》2015,78(11):1252-1258
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed. 相似文献
152.
153.
154.
155.
Ozonolysis of a Series of Methylated Alkenes: Reaction Rate Coefficients and Gas‐Phase Products
下载免费PDF全文
![点击此处可从《国际化学动力学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tristan Braure Véronique Riffault Alexandre Tomas Romeo Iulian Olariu Cecilia Arsene Yuri Bedjanian Patrice Coddeville 《国际化学动力学杂志》2015,47(9):596-605
The gas‐phase ozonolysis of three methylated alkenes, i.e., trans‐2,2‐dimethyl‐3‐hexene (22dM3H), trans‐2,5‐dimethyl‐3‐hexene (25dM3H), and 4‐methyl‐1‐pentene (4M1P), has been investigated in the presence of sufficient hydroxyl radical scavenger in a laminar flow reactor at ambient temperature (296 ± 2 K) and P = 1 atm of dry air (RH ≤ 5%). Ozone levels in the reactor were monitored by an automatic analyzer. Alkene and gas‐phase product concentrations were determined via online sampling either on three‐bed adsorbent cartridges followed by thermodesorption and GC/FID‐MS analysis or on 2,4‐dinitrophenylhydrazine (DNPH) cartridges for subsequent HPLC/UV analysis. Reaction rate coefficients of (3.38 ± 0.12) × 10?17 for 22dM3H and (2.71 ± 0.26) × 10?17 for 25dM3H, both in cm3 molecule?1 s?1 units, have been obtained under pseudo–first‐order conditions. Primary carbonyl products have been identified for the three investigated alkenes, and branching ratios are reported. In the case of 4M1P ozonolysis, the yield of a Criegee intermediate was indirectly determined. Kinetics and product study results are compared to those of literature when available. This work represents the first investigation of reaction products in the ozonolysis of 22dM3H, 25dM3H, and 4M1P in a flow reactor. 相似文献
156.
Colloid Journal - It has been found that the addition of ammonia water to a gold sol obtained by the Duff method induces the growth of the gold particles. The growth kinetics of such particles in... 相似文献
157.
158.
159.
Andrey Vyacheslavovich Vasilyev Valeriya Sergeevna Kuznetsova Tatyana Borisovna Bukharova Timofei Evgenevich Grigoriev Yuriy Dmitrievich Zagoskin Irina Alekseevna Nedorubova Igor Ivanovich Babichenko Sergey Nicolaevich Chvalun Dmitry Vadimovich Goldstein Anatoliy Alekseevich Kulakov 《Molecules (Basel, Switzerland)》2021,26(2)
Compositions based on chitosan/β-glycerophosphate hydrogels with highly porous polylactide granules can be used to obtain moldable bone graft materials that have osteoinductive and osteoconductive properties. To eliminate the influence of such characteristics as chain length, degree of purification, and molecular weight on a designed material, the one-stock chitosan sample was reacetylated to degrees of deacetylation (DD%) of 19.5, 39, 49, 55, and 56. A study of the chitosan/β-glycerophosphate hydrogel with chitosan of a reduced DD% showed that a low degree of deacetylation increased the MSCs (multipotent stromal cells) viability rate in vitro and reduced the leukocyte infiltration in subcutaneous implantation to Wistar rats in vivo. The addition of 12 wt% polylactide granules resulted in optimal composite mechanical and moldable properties, and increased the modulus of elasticity of the hydrogel-based material by approximately 100 times. Excessive filling of the material with PLA (polylactide) granules (more than 20%) led to material destruction at a ~10% strain. Osteoinductive and osteoconductive properties of the chitosan hydrogel-based material with reacetylated chitosan (39 DD%) and highly porous polylactide granules impregnated with BMP-2 (bone morphogenetic protein-2) have been demonstrated in models of orthotopic and ectopic bone formation. When implanted into a critical-size calvarial defect in rats, the optimal concentration of BMP-2 was 10 μg/mL: bone tissue areas filled the entire material’s thickness. Implantation of the material with 50 μg/mL BMP-2 was accompanied with excessive growth of bone tissue and material displacement beyond the defect. Significant osteoinductive and osteoconductive properties of the material with 10 μg/mL of BMP-2 were also shown in subcutaneous implantation. 相似文献
160.
Russian Journal of Applied Chemistry - A spectral-kinetic investigation was carried out to study the fluorescent properties of complexes of molecules of photochromic nitro-substituted spiropyran... 相似文献