全文获取类型
收费全文 | 278篇 |
免费 | 5篇 |
专业分类
化学 | 157篇 |
晶体学 | 12篇 |
力学 | 9篇 |
数学 | 25篇 |
物理学 | 80篇 |
出版年
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 27篇 |
2012年 | 11篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 10篇 |
2005年 | 10篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 12篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1959年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有283条查询结果,搜索用时 0 毫秒
1.
2.
3.
Trivedi VM 《Operations research》1981,29(5):1019-1034
This paper presents a mixed-integer goal programming model for expense budgeting in a hospital nursing department. The model incorporates several different objectives based upon such considerations as cost containment and providing appropriate nursing hours for delivering quality nursing care. Also considered are possible trade-offs among full-time, part-time and overtime nurses on weekdays as well as weekends. The budget includes vacation, sick leave, holiday, and seniority policies of a hospital and various constraints on a hospital nursing service imposed by nursing unions. The results are based upon data from a study hospital and indicate that the model is practical for budgeting in a hospital nursing department. 相似文献
4.
On the basis of micro- and macro-morphological studies the mechanism responsible for the growth of Se–Te whiskers has been suggested. It has been shown that Sc–Te whiskers grow by layer growth mechanism in which screw dislocation is not the source of step but the growth proceeds by two-dimensional nucleation. This has been supported by the supersaturation data. The plausible mechanism for the growth of hollow whiskers has also been suggested. 相似文献
5.
Experimental Mechanics - Understanding the mechanical response of elastomers to applied deformation at different strain rates and temperatures is crucial in industrial design and manufacture;... 相似文献
6.
Nerium odorum, Linn. (Apocynaceae) is an important evergreen shrub. It is heat, salinity and drought tolerant. Plants with milky sap have medicinal value, mainly cardenolides, flavonoids and terpenes. It is used for wastewater purification and for restoration of riparian woodlands. In view of these facts, the study was conducted for micropropagation of N. odorum. Murashige and Skoog (MS) media supplemented with different concentrations (0.5–10.0 mg/l) of 1-naphthaleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), 6-benzylaminopurine (BAP) and kinetin (Kin) were used singly and in combinations. Among all the growth hormones, 2,4-D was the best for callus induction (75 % in stem and 79 % in leaf) and in combination 2,4-D and BAP (78 % in stem and 81 % in leaf). The day of callus induction started from the 19th to the 37th day. This variation is due to the differences in culture conditions and the age of explants. The fresh and dry weight and moisture content showed good growth of callus, which is used in further studies of alkaloid production. Micropropagation of this plant allows the production of clones at a fast rate and in continuous manner. This work can lead to the development of an efficient protocol for callus induction and other issues. 相似文献
7.
Arun A. YadavPrajakta S. Sarang Manishankar SauSrinath Thirumalairajan Girish K. Trivedi Manikrao M. Salunkhe 《Tetrahedron letters》2012,53(28):3599-3602
[5+2] Cycloaddition followed by asymmetric dihydroxylation procedure have been utilized to prepare novel cyclitols. Accordingly, rac-2α-hydroxy-6α-ethoxy-1,5-anhydro cyclohept-3-ene, 10 derived from [5+2] cycloaddition of 3-oxidopyrylium ylide and vinyl ether has been recognized as a seven-membered carbasugar equivalent and elaborated to 1,4,5-tribenzoyloxy-2-ethoxy cycloheptanes through a flexible, regio- and stereoselective strategy involving Sharpless asymmetric dihydroxylation conditions to resolve the compounds obtained. The structures and relative configurations of newly synthesized (+)-2α-acetoxy-6α-ethoxy-3β,4β-dihydroxy-1,5-anhydro cycloheptane ((+)-12)); (−)-1β,4β,5β-tribenzoyloxy-6α-ethoxy cycloheptane ((−)-17) and (+)-1α,4α,5α-tribenzoyloxy-6β-ethoxy cycloheptane ((+)-17) are unambiguously established by single crystal X-ray analysis and duly supported by 1H and 13C NMR spectroscopy data. 相似文献
8.
9.
Ali Faraat Nandi Utpal Trivedi Manisha Prakash Anuj Dahiya Meenakshi Sahu Puran Lal Kumar Robin Singh Gyanendra Nath 《Journal of Thermal Analysis and Calorimetry》2018,132(1):385-396
Journal of Thermal Analysis and Calorimetry - The aim of this work was to evaluate the quantitative characterization and pharmaceutical compatibility study of teneligliptin (TNG) with the commonly... 相似文献
10.
Dyer JA Trivedi P Sanders SJ Scrivner NC Sparks DL 《Journal of colloid and interface science》2004,270(1):66-76
Previous studies demonstrated the environmental and economic benefits of treating lead(II)-contaminated water streams with ferrihydrite in multiple equilibrium sorption stages. In this work, multistage ferrihydrite sorption systems were evaluated for their effectiveness in reducing single-solute zinc(II) (Zn(II)) concentrations in contaminated water streams to very low levels. As for lead(II) (Pb(II)), experimental data and modeling results indicate that a multistage sorption system can significantly reduce Zn(II) effluent concentrations for the same total amount of sorbent or, alternatively, dramatically lower total sorbent consumption for the same effluent Zn(II) concentration. Compared to Pb(II), however, Zn(II) removal requires on the order of 10 times more sorbent to achieve the same target effluent concentration for the same pH and number of stages. Model predictions were made using a steady-state, multistage, equilibrium adsorber model that was previously developed for and integrated into OLI Systems' Environmental Simulation Program (ESP). The modified triple-layer model was used to simulate Zn(II) surface-liquid equilibria within the adsorber model. Engineering screening evaluations again indicate that a 2- to 3-stage sorption process can provide significant economic savings when compared to a 1-stage process operating with the same target effluent Zn(II) concentration. Additional equilibrium stages beyond 2 or 3 provide diminishing economic returns. The major economic driver for multiple contacting stages is reduced capital investment and operating costs for sludge handling, dewatering, and disposal. 相似文献