全文获取类型
收费全文 | 1541篇 |
免费 | 113篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 423篇 |
金属工艺 | 51篇 |
机械仪表 | 51篇 |
建筑科学 | 41篇 |
矿业工程 | 2篇 |
能源动力 | 49篇 |
轻工业 | 319篇 |
水利工程 | 19篇 |
石油天然气 | 16篇 |
无线电 | 88篇 |
一般工业技术 | 274篇 |
冶金工业 | 126篇 |
原子能技术 | 11篇 |
自动化技术 | 165篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 39篇 |
2021年 | 89篇 |
2020年 | 46篇 |
2019年 | 64篇 |
2018年 | 69篇 |
2017年 | 82篇 |
2016年 | 67篇 |
2015年 | 41篇 |
2014年 | 66篇 |
2013年 | 120篇 |
2012年 | 101篇 |
2011年 | 124篇 |
2010年 | 81篇 |
2009年 | 90篇 |
2008年 | 89篇 |
2007年 | 61篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 35篇 |
2003年 | 27篇 |
2002年 | 19篇 |
2001年 | 15篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 18篇 |
1994年 | 21篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 5篇 |
1973年 | 1篇 |
排序方式: 共有1655条查询结果,搜索用时 15 毫秒
191.
AE Omu S al-Othman AS Mohamad NM al-Kaluwby S Fernandes 《Canadian Metallurgical Quarterly》1998,43(10):857-864
OBJECTIVE: To investigate the effect of antibiotic therapy on seminal infection. STUDY DESIGN: The seminal plasma of 50 men was evaluated in three groups: (1) men with seminal infection (20), (2) men with leukocytospermia only (18), and (3) men of proven fertility (12). The evaluation protocol included semen analysis, culture and antibiotic sensitivity test, total antioxidant activity, alpha-tocopherol and retinol, T-helper cytokines, IL-2, IL-8, IL-4 and antisperm antibodies. RESULTS: Sperm parameters were worse with seminal infection: 25 versus 84 million per milliliter for fertile men. Antioxidant activity, total alpha-tocopherol and retinol were reduced in leukocytospermia (P < .02, .01) and seminal infection (P < .01, .05) as compared to controls. Antisperm antibodies IL-2 and IL-8 were highly expressed, while IL-4 was low in men with leukocytospermia and bacteriospermia. Gram-negative organisms were more associated with expression of T-helper 1 cytokines than T-helper 2 cytokines. Antibiotic therapy significantly improved the sperm parameters, antioxidant activity and IL-4 but reduced IL-2 and IL-8 and had no effect on antisperm antibody titer. CONCLUSION: Antibiotic therapy improves sperm parameters by increasing antioxidant activity and IL-4 and by reducing IL-2 and IL-8. 相似文献
192.
Several clinically active anticancer drugs are known to interfere with DNA topoisomerase II activity. However, the importance of the individual alpha (170 kDa) and beta (180 kDa) isozymes as targets of topoisomerase II-active drugs is not clear. To address this question, human CCRF-CEM leukemia cells were incubated with bromodeoxyuridine, and either the nascent DNA or bulk DNA not undergoing replication was purified by immunoprecipitation with an anti-bromodeoxyuridine antibody. The topoisomerase II isozymes that coprecipitated with either the nascent DNA or bulk DNA were analyzed by Western blotting. The alpha isozyme formed complexes with nascent DNA in cells pretreated with either VM-26 or mitoxantrone, while the beta isozyme was only bound to bulk DNA. At moderately cytotoxic concentrations, VM-26 enhanced the binding of topoisomerase II alpha to nascent DNA at least 5.2-fold compared to bulk DNA. However, in VM-26 resistant CEM/VM-1 cells incubated with equitoxic concentrations of VM-26, topoisomerase II alpha complex formation with nascent DNA was decreased at least 5.5-fold compared to bulk DNA. Drug-induced binding of topoisomerase II beta with bulk DNA in CEM/VM-1 cells did not correlate with cytotoxicity. Collectively, these results indicate that the formation of VM-26 stabilized complexes of topoisomerase II alpha with nascent DNA are critical to the development of cytotoxicity, and that resistance of CEM/VM-1 cells to VM-26 is related to impaired formation of these complexes. The results also provide indirect evidence that topoisomerase II alpha is involved in DNA, replication. 相似文献
193.
Currently available systems for resolving membrane proteins are based only on size and charge differences. Recently, it has been shown that Triton-urea-acetic acid gels which separate proteins on the basis of charge, size and hydrophobicity are capable of resolving proteins differing only by the substitution of a single neutral amino acid. We have applied this new method to the resolution of bacterial envelope proteins. Conditions for optimal resolution of different bacterial envelope proteins were determined by electrophoresis through transverse urea and Triton X-100 gradient gels. We have also correlated the components resolved in this system with those resolved by classical sodium dodecyl sulfate-gel electrophoresis by using two-dimensional slab gels combining the two systems. Furthermore, envelope protein fractions from different species and strains of bacteria were compared to identify specific proteins. This system appears to be a promising method for investigating envelope proteins which are due to missense mutations. 相似文献
194.
KV Fernandes PA Sabelli DH Barratt M Richardson J Xavier-Filho PR Shewry 《Canadian Metallurgical Quarterly》1993,23(1):215-219
A cDNA encoding a cysteine proteinase inhibitor was isolated from a cDNA library prepared from developing seeds of an insect-resistant line of cowpea. The sequence of the encoded protein was homologous with those of other plant cysteine endoproteinase inhibitors, and with Type 2 cystatins from animals. Southern blot analyses indicated that small gene families were present in both resistant and susceptible lines of cowpea, while northern blot analyses showed similar levels of expression. It is concluded that the levels of expression of the inhibitor do not account for the differences in insect resistance of the two lines. 相似文献
195.
AF Fuente del Campo E Rojas Allegretti JA Fernandes Filho CB Gordon 《Canadian Metallurgical Quarterly》1998,22(9):981-986
Liposuction is the most commonly used procedure for focal reduction of body fat deposits and remodeling the body contour. The procedure consists in aspirating fat from lamellar deposits using a vacuum source connected to a cannula that is passed bluntly through fatty tissue. Adjuncts to the procedure include infiltration of solutions to aid in fat removal or to limit blood loss and the application of ultrasonic energy to lyse fat cells before suction aspiration. Surgical history, theory, procedures, indications, potential complications, and guidelines are discussed herein. 相似文献
196.
PURPOSE: To evaluate the affect of removing the crystalline lens and implanting an intraocular lens on the axial elongation of a neonatal eye. METHODS: Monocular lensectomy coupled with the implantation of a monofocal or multifocal intraocular lens was performed on 21 neonatal rhesus monkeys. Fellow eyes were randomized to part-time occlusion therapy or no treatment. Longitudinal axial elongation of the pseudophakic eyes was then compared to that of the fellow eyes, to the eyes of 19 monkeys made monocularly aphakic as neonates, and to the eyes of 39 normal monkeys. RESULTS: At 5 weeks of age, aphakic and pseudophakic eyes were significantly shorter than their fellow eyes (P < 0.01). After 1 year of follow-up, the mean axial lengths of the pseudophakic and aphakic eyes were 2.0 +/- 0.2 mm and 2.3 +/- 0.2 mm, respectively, shorter than their fellow eyes. This axial length difference persisted through a second year of follow-up. The difference between the mean axial lengths of the aphakic and pseudophakic eyes was not significant (P > 0.10). Part-time occlusion of the fellow eyes did not affect axial elongation. CONCLUSIONS: Removing the crystalline lens and implanting an intraocular lens in a neonatal monkey eye retards its axial elongation. 相似文献
197.
Multiple episodes of blood-brain barrier disruption were induced by sequential intraspinal injections of ethidium bromide. In addition to the barrier disruption, there was toxic demyelination and exposure of myelin components to the immune system. Twenty-seven 3-month-old Wistar rats received 2, 3 or 4 injections of 1 microliter of either 0.1% ethidium bromide in normal saline (19 rats) or 0.9% saline (8 rats) at different levels of the spinal cord. The time intervals between the injections ranged from 28 to 42 days. Ten days after the last injection, all rats were perfused with 2.5% glutaraldehyde. The spinal sections were evaluated macroscopically and by light and transmission electron microscopy. All the lesions demonstrated a mononuclear phagocytic infiltrate apparently removing myelin. Lymphocytes were not conspicuous and were found in only 34% of the lesions. No perivascular cuffings were detected. In older lesions (38 days and older) they were found only within Virchow-Robin spaces. This result suggests that multiple blood-brain barrier disruptions with demyelination and exposure of myelin components to the immune system were not sufficient to induce an immune-mediated reaction in the central nervous system. 相似文献
198.
199.
200.