全文获取类型
收费全文 | 15700篇 |
免费 | 659篇 |
国内免费 | 44篇 |
专业分类
化学 | 10644篇 |
晶体学 | 248篇 |
力学 | 509篇 |
综合类 | 1篇 |
数学 | 1205篇 |
物理学 | 3796篇 |
出版年
2024年 | 67篇 |
2023年 | 181篇 |
2022年 | 464篇 |
2021年 | 446篇 |
2020年 | 491篇 |
2019年 | 547篇 |
2018年 | 514篇 |
2017年 | 494篇 |
2016年 | 704篇 |
2015年 | 492篇 |
2014年 | 805篇 |
2013年 | 1361篇 |
2012年 | 1198篇 |
2011年 | 1208篇 |
2010年 | 825篇 |
2009年 | 645篇 |
2008年 | 794篇 |
2007年 | 781篇 |
2006年 | 608篇 |
2005年 | 532篇 |
2004年 | 413篇 |
2003年 | 327篇 |
2002年 | 266篇 |
2001年 | 160篇 |
2000年 | 139篇 |
1999年 | 104篇 |
1998年 | 81篇 |
1997年 | 108篇 |
1996年 | 96篇 |
1995年 | 78篇 |
1994年 | 75篇 |
1993年 | 102篇 |
1992年 | 107篇 |
1991年 | 80篇 |
1990年 | 72篇 |
1989年 | 73篇 |
1988年 | 50篇 |
1987年 | 50篇 |
1986年 | 45篇 |
1985年 | 68篇 |
1984年 | 72篇 |
1983年 | 57篇 |
1982年 | 54篇 |
1981年 | 43篇 |
1980年 | 51篇 |
1979年 | 71篇 |
1978年 | 54篇 |
1977年 | 55篇 |
1976年 | 47篇 |
1975年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
11.
Das Pritam Kumar Mallik Arnab Kumar Molla Altaf Hossain Santra Apurba Kumar Ganguly Ranjan Saha Abhijit Kumar Sugam Aswal V. K. 《Journal of Thermal Analysis and Calorimetry》2022,147(10):5617-5635
Journal of Thermal Analysis and Calorimetry - Nanofluids have gained recent attention because of their potential applications in diverse engineering fields like enhancing thermal transport,... 相似文献
12.
In the present work, the use of cylindrical turbulators in a double pipe heat exchanger has been investigated. Cylindrical fin type of turbulators has been placed circumferentially separated by 90° on the outer side of an inner pipe at a regular pitch. Experimental studies were undertaken for different air flow rates in a turbulent regime whose Reynolds number range between 2500 and 10000. Heat transfer characteristics like Nu and friction factor have been experimentally determined. Parametric studies were conducted by changing the pitch and also the orientation of the turbulators. Nu and friction factor were found to increase as the pitch is reduced. A model with alternatively changed orientation outperformed others by exhibiting highest Nu and reduced friction factor. 相似文献
13.
Molecular Diversity - The antifungals that are in current clinical practice have a high occurrence of a side effect and multidrug resistance (MDR). Researchers across the globe are trying to... 相似文献
14.
15.
Sajeesh Kumar Madhurakkat Perikamana Sang Min Lee Jinkyu Lee Taufiq Ahmad Min Suk Lee Hee Seok Yang Heungsoo Shin 《Macromolecular bioscience》2019,19(4)
Plant derived flavonoids have not been well explored in tissue engineering applications due to difficulties in efficient formulations with biomaterials for controlled presentation. Here, the authors report that surface coating of epigallocatechin gallate (EGCG) on polymeric substrates including poly (L‐lactic acid) (PLLA) nanofibers can be performed via oxidative polymerization of EGCG in the presence of cations, enabling regulation of biological functions of multiple cell types implicated in bone regeneration. EGCG coating on the PLLA nanofiber promotes osteogenic differentiation of adipose‐derived stem cells (ADSCs) and is potent to suppress adipogenesis of ADSCs while significantly reduces osteoclastic maturation of murine macrophages. Moreover, EGCG coating serves as a protective layer for ADSCs against oxidative stress caused by hydrogen peroxide. Finally, the in vivo implantation of EGCG‐coated nanofibers into a mouse calvarial defect model significantly promotes the bone regeneration (61.52 ± 28.10%) as compared to defect (17.48 ± 11.07%). Collectively, the results suggest that EGCG coating is a simple bioinspired surface modification of polymeric biomaterials and importantly can thus serve as a promising interface for tuning activities of multiple cell types associated with bone fracture healing. 相似文献
16.
Raju Surapuraju Pavan Kumar Narayanam Mallikarjun Kumar Banothu Kranthi Tejaswee Sreeram Singh Saranjit 《Chromatographia》2015,78(19):1245-1250
Alendronate sodium is widely used in the treatment of osteoporosis and Paget’s disease. The HPLC method development for alendronate sodium, in particular, is challenging owing to the absence of chromophoric group and its high polarity. In the present study, a short and simple isocratic method was developed involving hydrophilic interaction liquid chromatography, coupled with a charged aerosol detector. The developed method was validated according to the ICH Q2(R1) guideline and was successfully applied for the analysis of a marketed formulation containing the drug.
相似文献17.
An attempt is made to find out the suitable entrainment and exit boundary conditions in laminar flow situations. Streamfunction vorticity formulation of the Navier–Stokes equations are solved by ADI method. Two‐dimensional laminar plane wall jet flow is used to test different forms of the boundary conditions. Results are compared with the experimental and similarity solution and the proper boundary condition is suggested. The Kind 1 boundary condition is recommended. It consists of zero first derivative condition for velocity variable and for streamfunction equation, mixed derivative at the entrainment and exit boundaries. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
18.
Open circuit voltage (OCV) measurements in H2O/air concentration cells at T<580 K using Yb-doped SrCeO3 electrolyte indicate that under these conditions, protons are transported through the electrolyte as -ve ions, possibly as
hydroxyl (OH−) ions. The H+ ionic transport, which is generally reported, becomes the dominant mode for H2O/air concentration cells at temperatures greater than 750 K or when H2O/air electrodes are replaced by H2/Ar, and the anomalous OCV sign disappears. The combination of low temperature and the presence of hydrogen and oxygen as
provided by the H2O/air system appears to be necessary for the postulated hydroxyl ion electrode reactions to take place.
In addition to OCV measurements, results from impedance spectroscopy are used to provide evidence in support of the suggested
hydroxyl ion mode of protonic transport under the specified conditions. These findings are directly relevant in the development
of novel humidity sensors in the temperature range 450–580K and is reported in a separate paper in this conference.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
19.
An M/G/1 retrial queueing system with additional phase of service and possible preemptive resume service discipline is considered. For an arbitrarily distributed retrial time distribution, the necessary and sufficient condition for the system stability is obtained, assuming that only the customer at the head of the orbit has priority access to the server. The steady-state distributions of the server state and the number of customers in the orbit are obtained along with other performance measures. The effects of various parameters on the system performance are analysed numerically. A general decomposition law for this retrial queueing system is established. 相似文献
20.