全文获取类型
收费全文 | 1055篇 |
免费 | 38篇 |
专业分类
电工技术 | 4篇 |
综合类 | 6篇 |
化学工业 | 192篇 |
金属工艺 | 9篇 |
机械仪表 | 7篇 |
建筑科学 | 88篇 |
矿业工程 | 1篇 |
能源动力 | 10篇 |
轻工业 | 156篇 |
水利工程 | 20篇 |
石油天然气 | 4篇 |
无线电 | 61篇 |
一般工业技术 | 135篇 |
冶金工业 | 304篇 |
原子能技术 | 1篇 |
自动化技术 | 95篇 |
出版年
2024年 | 5篇 |
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 34篇 |
2020年 | 14篇 |
2019年 | 18篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 26篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 50篇 |
2012年 | 43篇 |
2011年 | 91篇 |
2010年 | 59篇 |
2009年 | 57篇 |
2008年 | 70篇 |
2007年 | 66篇 |
2006年 | 59篇 |
2005年 | 58篇 |
2004年 | 48篇 |
2003年 | 47篇 |
2002年 | 44篇 |
2001年 | 23篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 19篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1972年 | 1篇 |
排序方式: 共有1093条查询结果,搜索用时 15 毫秒
141.
142.
Michael B. Power Andrew R. Barron Drhomír Hnyk Heather E. Robertson David W. H. Rankin 《Advanced functional materials》1995,5(3):177-185
The gallium sulphide cubane compounds [(Me2EtC)GaS]4 and [(Et2MeC)GaS]4, have been synthesised, and their potential as MOCVD precursors for GaS is discussed. The molecular structure of [(Et2MeC)GaS]4 has been determined by X-ray diffraction. In addition, the vapour phase structure of the GaSe precursor, [(tBu)GaSe]4 has been determined by gas phase electron diffraction and is compared with that previously determined in the solid state by X-ray diffraction. 相似文献
143.
Jane A Wetherall David G Armstrong Heather J Finlayson John A Rooke 《Journal of the science of food and agriculture》1995,68(4):497-505
Two experiments were carried out to assess the effectiveness of protease inhibitors in reducing proteolysis during ensilage. Perennial ryegrass (Lolium perenne) (279 g dry matter (DM) kg?1, experiment 1 and 170 gDM kg?1 experiment 2) was ensiled in laboratory silos for 82 and 50 days, respectively. With the exception of the application of formic acid (1.5 g kg?1) plus formalin (3 g kg?1) in experiment 1, all silages had pH values of less than 4.0 and lactic acid concentrations of greater than 100 g kg?1 DM. Application of the cysteine endopeptidase inhibitor E-64 (1-trans-epoxysuccinyl-leucylamido(4-guanidino) butane, 22.5 mg kg?1 reduced proteolysis during ensilage as measured by a reduction in the quantities of soluble non-protein N in silage to 0.76 and 0.91 of control values (528 and 643 g kg?1 total N) in experiments 1 and 2, respectively. In experiment 2 increasing the application rate of E-64 from 22.5 to 45 mg kg?1 further reduced the extent of proteolysis from 0.91 to 0.75 of control soluble non-protein N concentrations. Proteolysis was also reduced in experiment 2 by two other cysteine endopeptidase inhibitors, antipain (32 mg kg?1, 0.81 of control) and cystain (1.2 mg kg?1; 0.89 of control). Pepstatin A (300 mg kg?1), an inhibitor of aspartic acid endopeptidases, did not reduce soluble non-protein N concentrations in experiment 1 but did do so in experiment 2 (0.81 of control). Treatment of grass at ensiling with Lactobacillus plantarum (106 g?1) reduced silage non-protein N concentrations to 0.83 of the control. The effects of E-64 and pepstatin A and of E-64 and L plantarum in experiment 2 were addive. Cysteine endopeptidases therefore play an important role in protein breakdown during ensilage. 相似文献
144.
Modifications of Hermissenda's phototactic behavior by compound pairings of light, scallop extract, and rotation were assessed. In general, the scallop extract potentiated phototactic suppression. Potentiation was dependent on (a) conjunctive presentations of scallop and light, (b) number of conditioning trials, and (c) scallop extract concentration. In related experiments, no second-order conditioning or sensory preconditioning of phototactic suppression was observed, indicating that within-compound associations did not contribute appreciably to potentiation. These results represent the first detailed analysis of compound conditioning in a mollusk using discrete presentations of well-characterized conditioned stimuli from distinct sensory modalities. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
145.
Heron Reva L.; Twomey Heather B.; Jacobs Diana P.; Kaslow Nadine J. 《Canadian Metallurgical Quarterly》1997,34(4):410
This article focuses on interventions with low-income, African American women who are survivors of domestic abuse and who have made one or more suicide attempts. The authors review the literature on domestic abuse and suicidal behavior in African American women, and discuss the association between abuse and suicide in this population. Next, they propose an integrated theoretical model for understanding suicidal behavior as one possible coping response to the stress of a domestic abuse situation. The model utilizes concepts from the literature on stress and coping as well as stages of change. A culturally sensitive group treatment intervention that is based on the theoretical model is presented. The intervention focuses on ensuring women's safety, increasing coping skills and resource mobilization, and promoting supportive relationships in a manner that is consistent with each woman's sociocultural context. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
146.
Balasubramani GK Wisniewski SR Zhang H Eng HF 《Computer methods and programs in biomedicine》2005,79(2):179-187
When underlying distributions are unknown and sample sizes are small, permutation tests may have superior features to parametric tests, such as smaller type I error and more accurate probability values when testing the null hypothesis. However, permutation tests are not widely used in clinical trials because of their computational complexity. We developed an efficient SAS macro to generate all possible permutations of the data and to run subsequent permutation tests of difference between means for two independent samples. The macro performs permutation tests and provides the exact probability of significance for a wide range of statistics, including geometric means, medians, mid-ranges, mean-ranks, proportions and variances to meet the needs of data analysis in clinical trials. 相似文献
147.
Although long-chain fatty acyl-coenzyme A (LCFA-CoA) thioesters are specific high-affinity ligands for hepatocyte nuclear
factor-4α (HNF-4α) and peroxisome proliferator-activated receptor-α (PPARα), X-ray crystals of the respective purified recombinant
ligand-binding domains (LBD) do not contain LCFA-CoA, but instead exhibit bound LCFA or have lost all ligands during the purification
process, respectively. As shown herein: (i) The acyl chain composition of LCFA bound to recombinant HNF-4α reflected that
of the bacterial LCFA-CoA pool, rather than the bacterial LCFA pool. (ii) Bacteria used to produce the respective HNF-4α and
PPARα contained nearly 100-fold less LCFA-CoA than LCFA. (iii) Under conditions used to crystallize LBD (at least 3 wk at
room temperature in aqueous buffer), 16∶1-CoA was very unstable in buffer alone. (iv) In the presence of the respective nuclear
receptor (i.e., HNF-4α and PPARα), LBD 70–75% of 16∶1-CoA was degraded after 1 d at room temperature in the crystallization
buffer, whereas as much as 94–97% of 16∶1-CoA was degraded by 3 wk. (v) Cytoplasmic LCFA-CoA binding proteins such as acyl-CoA
binding protein, sterol carrier protein-2, and liver-FA binding protein slowed the process of 16∶1-CoA degradation proportional
to their respective affinities for this ligand. Taken together, these data for the first time indicated that the absence of
LCFA-CoA in the crystallized HNF-4α and PPARα was due to the paucity of LCFA-CoA in bacteria as well as to the instability
of LCFA-CoA in aqueous buffers and the conditions used for LBD crystallization. Furthermore, instead of protecting bound LCFA-CoA
from autohydrolysis like several cytoplasmic LCFA-CoA binding proteins, these nuclear receptors facilitated LCFA-CoA degradation. 相似文献
148.
149.
Foran Heather M.; Slep Amy M. Smith; Heyman Richard E. 《Canadian Metallurgical Quarterly》2011,79(3):391
Objective: Intimate partner violence (IPV) is a serious health concern, but little is known about prevalence of IPV in the armed forces, as military members cope with the pressures of long-standing operations. Furthermore, previous prevalence studies have been plagued by definitional issues; most studies have focused on acts of aggression without consideration of impact (clinically significant [CS] IPV). This is the first large-scale study to examine prevalences of IPV, CS-IPV, and clinically significant emotional abuse (CS-EA) for men and women. Method: A United States Air Force-wide anonymous survey was administered across 82 bases in 2006 (N = 42,744) to assess IPV, CS-IPV, and CS-EA. Results: The adjusted prevalence of CS-IPV perpetration was 4.66% for men and 3.54% for women. Prevalences of IPV perpetration were 12.90% for men and 15.14% for women. CS-EA victimization was 6.00% for men and 8.50% for women. Sociodemographic differences in risk for violence were found for gender, race/ethnicity, pay grade, religious faith, marital status, and career type even after controlling for other demographic variables. Conclusions: Partner maltreatment is widespread in military (and civilian) samples. Men were more likely to perpetrate CS-IPV, whereas women were more likely to perpetrate IPV. Specific demographic risk factors were identified for different types of partner maltreatment (e.g., lower rank predicted higher risk for both perpetration and victimization across men and women). Other sociodemographic differences varied across severity (IPV vs. CS-IPV) and across gender. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
150.
Renewable and low carbon fuel standards being developed at federal and state levels require an estimation of the life cycle carbon intensity (LCCI) of candidate fuels that can substitute for gasoline, such as second generation bioethanol. Estimating the LCCI of such fuels with a high degree of confidence requires the use of probabilistic methods to account for known sources of uncertainty. We construct life cycle models for the bioconversion of agricultural residue (corn stover) and energy crops (switchgrass) and explicitly examine uncertainty using Monte Carlo simulation. Using statistical methods to identify significant model variables from public data sets and Aspen Plus chemical process models,we estimate stochastic life cycle greenhouse gas (GHG) emissions for the two feedstocks combined with two promising fuel conversion technologies. The approach can be generalized to other biofuel systems. Our results show potentially high and uncertain GHG emissions for switchgrass-ethanol due to uncertain CO? flux from land use change and N?O flux from N fertilizer. However, corn stover-ethanol,with its low-in-magnitude, tight-in-spread LCCI distribution, shows considerable promise for reducing life cycle GHG emissions relative to gasoline and corn-ethanol. Coproducts are important for reducing the LCCI of all ethanol fuels we examine. 相似文献