全文获取类型
收费全文 | 5264篇 |
免费 | 197篇 |
国内免费 | 383篇 |
专业分类
化学 | 4611篇 |
晶体学 | 10篇 |
力学 | 297篇 |
综合类 | 16篇 |
数学 | 355篇 |
物理学 | 555篇 |
出版年
2024年 | 4篇 |
2023年 | 65篇 |
2022年 | 97篇 |
2021年 | 85篇 |
2020年 | 134篇 |
2019年 | 122篇 |
2018年 | 85篇 |
2017年 | 147篇 |
2016年 | 108篇 |
2015年 | 142篇 |
2014年 | 161篇 |
2013年 | 233篇 |
2012年 | 273篇 |
2011年 | 276篇 |
2010年 | 240篇 |
2009年 | 274篇 |
2008年 | 259篇 |
2007年 | 310篇 |
2006年 | 302篇 |
2005年 | 341篇 |
2004年 | 276篇 |
2003年 | 206篇 |
2002年 | 171篇 |
2001年 | 124篇 |
2000年 | 134篇 |
1999年 | 154篇 |
1998年 | 154篇 |
1997年 | 135篇 |
1996年 | 104篇 |
1995年 | 73篇 |
1994年 | 87篇 |
1993年 | 50篇 |
1992年 | 44篇 |
1991年 | 50篇 |
1990年 | 46篇 |
1989年 | 35篇 |
1988年 | 45篇 |
1987年 | 30篇 |
1986年 | 38篇 |
1985年 | 68篇 |
1984年 | 37篇 |
1983年 | 25篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1980年 | 18篇 |
1979年 | 19篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有5844条查询结果,搜索用时 15 毫秒
991.
Ramalingam Balamurugan 《Tetrahedron》2007,63(45):11078-11085
A detailed study on oxidation of N-protected bromomethylindoles into the respective aldehydes was carried out. Using a modified Hass procedure, synthesis of aryl-/hetero-aryl aldehydes in particular indolaldehydes is achieved in reasonable yields. 相似文献
992.
Protein–protein conjugates formed by carbodiimide crosslinking reactions have been analyzed for the first time using CE. Lysozyme and BSA were chosen as model proteins to study the efficacy of N‐(3‐dimethylaminopropyl)‐N‐ethylcarbodiimide and N‐hydroxysuccinimide as crosslinkers. Detection of the molecular mass increase was checked by SDS‐PAGE. Commercially available, PVA‐coated capillaries showed appropriate selection, while phospho‐deactivated and dynamic PVA‐coated capillaries did not give suitable resolution. CE was found to be an efficient tool to characterize homo‐ (lysozyme–lysozyme) and hetero‐ (lysozyme–BSA) protein coupling by suitable variations of electrophoretic mobilities. 相似文献
993.
Silica-based monolithic capillary columns—Effect of preparation temperature on separation efficiency
Josef Planeta Dana MoravcováMichal Roth Pavel KarásekVladislav Kahle 《Journal of chromatography. A》2010,1217(36):5737-5740
The temperature effects during the sol–gel process and ageing of the silica-based monolith on the structure and separation efficiency of the capillary columns (100 μm i.d., 150 mm) for HPLC separations were studied. The tested columns were synthesized from a mixture of tetramethoxysilane, polyethylene glycol and urea under the acidic conditions. The temperature was varied from 40 °C to 44 °C and formation of bypass channels between the silica mold and the capillary wall was examined. The temperature of 43 °C was estimated as optimal for preparation of efficient silica capillary columns which were subsequently modified by octadecyldimethyl-N,N-diethylaminosilane or covered by poly(octadecyl methacrylate) and tested using standard mixture of alkylbenzenes under the isocratic conditions. 相似文献
994.
A Kerr nonlinear blackbody (KNB) is a new kind of blackbody in which bare photons with opposite wave vectors and helicities are bound into pairs and unpaired photons are transformed into nonpolaritons. In the present paper, we focus our investigation on the modified radiation laws, such as Planck and Stefan-Boltzmann radiation laws, of a rectangular KNB. Besides, the case of a KNB with no symmetry axes is also discussed. Finally, we make a numerical calculation of modified radiation laws of a cubic KNB under appropriate conditions, and we consider this work may lay the foundation for the experimental verification of the model of a KNB. 相似文献
995.
SnO2-ZnO hollow nanofibers were fabricated through a facile single capillary electrospinning technology. The structure and toluene sensing properties of the hollow fibers were investigated. The results indicated that the fibers possess a hollow structure, a rough porous surface after being annealed at 600 °C and the diameters are in the range of 80-160 nm. A sensor fabricated from these fibers exhibits considerable sensitivity and good stability against toluene at 190 °C, which can be attributed to the special 1D hollow structure and the promoting effect of the SnO2/ZnO heterojunction. The formation mechanism and toluene sensing mechanism of SnO2-ZnO hollow nanofibers were also discussed. 相似文献
996.
Chung-jong BongKwon-sang Ryu Seung-hoon NahmEun Kyu Kim 《Journal of magnetism and magnetic materials》2011,323(5):379-382
We present a magnetic and nondestructive method to evaluate the remanent life of modified 9Cr-1Mo steel by measuring the reversible magnetic permeability. Specimens with ten different kinds of aging periods were prepared using an isothermal heat treatment at 690 °C. The Larson-Miller parameter (LMP) was calculated and the peak interval of reversible magnetic permeability (PIRMP) was measured using the surface type probe. PIRMP was inversely proportional to LMP. We can evaluate the remanent life of modified 9Cr-1Mo steel using the relationship between PIRMP and LMP. Also, we present the possibility that the tensile strength and yield strength measured by destructive methods could be estimated by PIRMP measured nondestructively. 相似文献
997.
We investigate cosmological consequences of a class of exponential f(R) gravity in the Palatini formalism. By using the current largest type Ia Supernova sample along with determinations of the cosmic expansion at intermediary and high-z we impose tight constraints on the model parameters. Differently from other f(R) models, we find solutions of transient acceleration, in which the large-scale modification of gravity will drive the Universe to a new decelerated era in the future. We also show that a viable cosmological history with the usual matter-dominated era followed by an accelerating phase is predicted for some intervals of model parameters. 相似文献
998.
999.
We study a problem in stochastic functional differential equations which, in addition to a standard one-one-parameter noise term involves a random perturbation of the memory. This problem can also be regarded as a first order hyperbolic system of stochastic partial differential equations with given initial data and nonlocal boundary data. Existence and uniqueness of a solution is established and the generator of the associated Markov process is analyzed. Thereafter, for two model problems arising from first- and second-order integro-differential equations suggested by physical applications we establish asymptotic stability in probability of the associated stochastic processes. 相似文献
1000.
Deyber Arley Vargas Medina Alessandra Timoteo Cardoso João Victor Basolli Borsatto Fernando Mauro Lanças 《Journal of separation science》2023,46(18):2300373
Nano-liquid chromatography (nanoLC) is gaining significant attention as a primary analytical technique across various scientific domains. Unlike conventional high-performance LC, nanoLC utilizes columns with inner diameters (i.ds.) usually ranging from 10 to 150 μm and operates at mobile phase flow rates between 10 and 1000 nl/min, offering improved chromatographic performance and detectability. Currently, most exploration of nanoLC has focused on particle-packed columns. Although open tubular LC (OTLC) can provide superior performance, optimized OTLC columns require very narrow i.ds. (< 10 μm) and demand challenging instrumentation. At the moment, these challenges have limited the success of OTLC. Nevertheless, remarkable progress has been made in developing and utilizing OTLC systems featuring narrow columns (< 2 μm). Additionally, significant efforts have been made to explore larger columns (10–75 μm i.d), demonstrating practical applicability in many situations. Due to their perceived advantages, interest in OTLC has resurged in the last two decades. This review provides an updated outlook on the latest developments in OTLC, focusing on instrumental challenges, achievements, and advancements in column technology. Moreover, it outlines selected applications that illustrate the potential of OTLC for performing targeted and untargeted studies. 相似文献