全文获取类型
收费全文 | 2216篇 |
免费 | 241篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
综合类 | 3篇 |
化学工业 | 695篇 |
金属工艺 | 27篇 |
机械仪表 | 20篇 |
建筑科学 | 96篇 |
矿业工程 | 77篇 |
能源动力 | 32篇 |
轻工业 | 472篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
无线电 | 142篇 |
一般工业技术 | 335篇 |
冶金工业 | 285篇 |
原子能技术 | 13篇 |
自动化技术 | 226篇 |
出版年
2023年 | 30篇 |
2022年 | 65篇 |
2021年 | 94篇 |
2020年 | 56篇 |
2019年 | 53篇 |
2018年 | 63篇 |
2017年 | 92篇 |
2016年 | 119篇 |
2015年 | 102篇 |
2014年 | 104篇 |
2013年 | 187篇 |
2012年 | 131篇 |
2011年 | 140篇 |
2010年 | 121篇 |
2009年 | 101篇 |
2008年 | 120篇 |
2007年 | 124篇 |
2006年 | 79篇 |
2005年 | 76篇 |
2004年 | 62篇 |
2003年 | 49篇 |
2002年 | 55篇 |
2001年 | 42篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 53篇 |
1997年 | 43篇 |
1996年 | 21篇 |
1995年 | 23篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 14篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 6篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1970年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有2458条查询结果,搜索用时 31 毫秒
941.
Ecological compensation is an example of a trade-off whereby loss of natural values is remedied or offset by a corresponding compensatory action on the same site or elsewhere, determined through the process of Environmental Impact Assessment (EIA). Ecological compensation actions are often criticised for having low levels of compliance: meaning that they are achieved only partially or not at all, while development activity proceeds with much greater certainty. Our research investigated compliance with 245 conditions relating to ecological compensation across 81 case studies across New Zealand under the Resource Management Act 1991. Our results show that present tools and practice in New Zealand are not adequately securing the necessary benefits from ecological compensation requirements, with 35.2% of requirements not being achieved. Significant variation in non-compliance with ecological compensation occurs between different activities, applicant types and condition types, while critical variables within the planning process influence levels of compliance. Our research demonstrates the importance of understanding the nature of non-compliance and of providing a consistent and robust decision-making framework for the consideration of ecological compensation in practice. 相似文献
942.
Michèle Kessler Concetta Gangemi Alberto Gutierrez Martones Jean‐Louis Lacombe Marie‐Jeanne Krier‐Coudert Roula Galland Jan T. Kielstein Frédérique Moureau Nathalie Loughraieb 《Hemodialysis international. International Symposium on Home Hemodialysis》2013,17(2):282-293
This prospective, multicenter, proof‐of‐concept study aimed to evaluate the possibility to reduce the ordinary heparin dose and the systemic anti‐Xa activity during hemodialysis (HD) sessions using a new heparin‐grafted HD membrane. In 45 stable HD patients, the use of a heparin‐grafted membrane with the ordinary heparin dose was followed by a stepwise weekly reduction of dose. Reduction was stopped when early signs of clotting (venous pressure, quality of rinse‐back) occurred during two out of three weekly HD sessions. Heparin dose was decreased for 67% of patients resulting in the lowering of these patients' anti‐Xa activity by 50%. Dose reductions were achieved with both types of heparin (low‐molecular‐weight heparin: 64 ± 14 to 35 ± 12 IU/kg, P < 0.0001; unfractionated heparin: 82 ± 18 to 46 ± 13 IU/kg, P < 0.0001) resulting in a decrease of anti‐Xa activity at dialysis session end (low‐molecular‐weight heparin: 0.51 ± 0.25 to 0.25 ± 0.11 IU/mL, P < 0.0001; unfractionated heparin: 0.28 ± 0.23 to 0.13 ± 0.07 IU/mL, P < 0.0001). Failure to further decrease heparin dose was related to signs of clotting in blood lines (57% of sessions), in dialyzer (9%), or both (34%). Significant reduction of heparin dose and anti‐Xa activity at the end of HD sessions was possible in stable HD patients using heparin‐grafted membrane. HD patients who require low anti‐Xa activity at the end of HD sessions might benefit from a heparin‐grafted membrane to reduce bleeding risk and other heparin adverse events. 相似文献
943.
944.
Bernard Fache Bernard Gallot Marie Pierre Gelin Jean Claude Milano Quang Trung Pham 《应用聚合物科学杂志》2013,127(5):3798-3813
Four bismaleimides with mesogen “amide–ester” aromatic and flexible polymethylenic group variable length (8 ≤ n ≤ 11) were synthesized in two stages, producing yields exceeding 80%. These bismaleimides (BMIs) were obtained after several purifications by dissolution—precipitation in dimethylformamide–methanol (1/4) with over 94% purity (high‐performance liquid chromatography). These pure BMIs were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and elemental analysis and studied by differential scanning calorimetry, thermogravimetric analysis, polarized light microscopy, and X‐ray diffraction. Solubilities and thermal properties show effects of parity. The even BMIs are more difficult to solubilize than the odd BMI. The melting points of the even BMI (approximately, 220°C) are far higher than those of odd BMI (approximately, 160°C). Crosslinking temperatures of even BMI are close to 230°C, whereas odd BMI crosslinking temperatures are higher (approximately, 250°C). Even BMIs give rise to a liquid crystal state upon melting. Under the same conditions, odd BMIs give rise to an amorphous state; however, after crosslinking, the four bismaleimides give rise to an ordered liquid crystal state of smectic type. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
945.
Nicolas Ducruet Luc Delmotte Gautier Schrodj Francine Stankiewicz Nancy Desgardin Marie‐France Vallat Bassel Haidar 《应用聚合物科学杂志》2013,128(1):436-443
Crosslinking reaction of hydroxyl‐terminated polybutadiene (HTPB)/isophorone di‐isocyanate (IPDI) was monitored by infrared spectroscopy, dynamic mechanical analysis (DMA), swelling measurements, and by relaxation time (T2) measurements obtained by low‐field NMR technique. Chemical reaction monitored by FTIR shows that urethane bonds were predominantly formed throughout the whole reaction period while DMA and swelling became only effective once the three‐dimensional network was formed. NMR results allow differentiating between relaxation‐processes associated with different fractions of the reactants in the mixture prior to the network formation. The most important finding in this study is that two of the relaxation processes were found to decline whereas a new fraction with a short relaxation time which emerged specifically at an early stage of reaction and progressed along with advancement of the reaction. All results pointed out to a change in the mixture behavior around 30 h of crosslinking reaction at 60°C, reflecting an important restriction in molecules diffusion and mobilities which were attributed to the gel point formation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
946.
Bio‐based polyamide 11 and natural halloysite nanotubes (HNTs) were used for the preparation of PA‐11/HNT nanocomposites with varying nanotubes concentrations by melt extrusion using a masterbatch dilution process. The prepared nanocomposites were analyzed for microstructural changes, transparency, thermal stability, rheological behavior, dielectric, and mechanical properties. The HNT nanotubes are well dispersed in PA‐11 matrix in the studied composition range as shown by microscopy and spectrophotometry. Interestingly, good halloysite dispersion in PA‐11 matrix increases the tensile strength and Young modulus of PA‐11 without sacrificing the ductility. Highly dispersed nanotubes also bring favorable changes in the thermal stability, dielectric, and rheological characteristics of PA‐11. Additionally, glass transition temperature, crystallization temperature, and degree of crystallinity of the nanocomposites tend to increase with increase in nanotubes loading. Thus, PA‐11 can become a tailor‐made material with multifunctional characteristics, thanks to the addition of HNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
947.
948.
Louise Marie Sørensen Klaus Gori Mikael Agerlin Petersen Lene Jespersen Nils Arneborg 《International Dairy Journal》2011,21(12):970-978
A simple cheese model mimicking a cheese surface was developed for the detection of cheese flavour formation of yeasts. A total of 56 flavour compounds were detected by dynamic headspace sampling followed by gas chromatography–mass spectrometry analysis. Yarrowia lipolytica CBS 2075 primarily produced sulphides, furans and short-chain ketones; Saccharomyces cerevisiae D7 primarily produced esters and Debaryomyces hansenii D18335 primarily produced branched-chain aldehydes and alcohols. For several of the detected flavour compounds, an increase in production was observed upon exposure to dairy-relevant environmental stress conditions including high NaCl concentration and low temperature. The predominant yeasts on the cheese surface may be important for development of flavour, and thus the use of yeasts as ripening cultures has the potential to affect the flavour of cheese. 相似文献
949.
Pål Anders Wang Birthe Vang Alice Marie Pedersen Iciar Martinez Ragnar Ludvig Olsen 《Food chemistry》2011
Fish muscle is rapidly degraded during post-mortem storage, due to proteolytic enzymes acting probably both on muscle cells and connective tissue. In this work we have developed a model system which may be used to study the enzymatic degradation occurring in intact post-mortem fish muscle. Degradation of myosin heavy chain (MHC) was monitored in muscle with pH adjusted to 6.05, 6.3 and 6.9 and in the presence of the enzyme inhibitors PMSF, EDTA, phenanthroline, pepstatin A, antipain, E-64 and the cysteine proteinase activator dithiothreithol (DTT). After storage, myofibrillar proteins were isolated and MHC-specific antibodies used to study the degradation in the different samples. MHC from muscle with pH 6.05 and 6.3 was degraded, while no severe degradation was observed at pH 6.9. Introduction of enzyme inhibitors into the muscle tissue clearly showed that mainly cysteine and aspartic proteinases are responsible for the in situ MHC degradation. This is supported by the severe breakdown of MHC in the muscle samples containing DTT. 相似文献
950.
Kedra Cyrus Dr. Marie Wehenkel Eun‐Young Choi Dr. Hyosung Lee Dr. Hollie Swanson Prof. Dr. Kyung‐Bo Kim Prof. Dr. 《ChemMedChem》2010,5(7):979-985
Estrogen receptor‐α (ER) antagonists have been widely used for breast cancer therapy. Despite initial responsiveness, hormone‐sensitive ER‐positive cancer cells eventually develop resistance to ER antagonists. It has been shown that in most of these resistant tumor cells, the ER is expressed and continues to regulate tumor growth. Recent studies indicate that tamoxifen initially acts as an antagonist, but later functions as an ER agonist, promoting tumor growth. This suggests that targeted ER degradation may provide an effective therapeutic approach for breast cancers, even those that are resistant to conventional therapies. With this in mind, we previously demonstrated that proteolysis targeting chimeras (PROTACs) effectively induce degradation of the ER as a proof‐of‐concept experiment. Herein we further refined the PROTAC approach to target the ER for degradation. The ER‐targeting PROTACs are composed of an estradiol on one end and a hypoxia‐inducing factor 1α (HIF‐1α)‐derived synthetic pentapeptide on the other. The pentapeptide is recognized by an E3 ubiquitin ligase called the von Hippel Lindau tumor suppressor protein (pVHL), thereby recruiting the ER to this E3 ligase for ubiquitination and degradation. Specifically, the pentapeptide is attached at three different locations on estradiol to generate three different PROTAC types. With the pentapeptide linked through the C7α position of estradiol, the resulting PROTAC shows the most effective ER degradation and highest affinity for the estrogen receptor. This result provides an opportunity to develop a novel type of ER antagonist that may overcome the resistance of breast tumors to conventional drugs such as tamoxifen and fulvestrant (Faslodex). 相似文献