全文获取类型
收费全文 | 951篇 |
免费 | 0篇 |
专业分类
化学工业 | 4篇 |
能源动力 | 1篇 |
轻工业 | 1篇 |
无线电 | 4篇 |
一般工业技术 | 3篇 |
冶金工业 | 932篇 |
自动化技术 | 6篇 |
出版年
2013年 | 3篇 |
2012年 | 2篇 |
2008年 | 1篇 |
2007年 | 2篇 |
2006年 | 2篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 30篇 |
1998年 | 283篇 |
1997年 | 170篇 |
1996年 | 120篇 |
1995年 | 60篇 |
1994年 | 41篇 |
1993年 | 53篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 12篇 |
1978年 | 4篇 |
1977年 | 15篇 |
1976年 | 58篇 |
1974年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有951条查询结果,搜索用时 15 毫秒
1.
Ten groups of 14 immunosuppressed NMRI-mice (nu/nu) were raised and kept under germ-reduced conditions. The control animals were fed a germ-reduced diet, nine other groups received the same diet with selegiline (CAS 14611-51-9, Deprenyl) or lipoic acid (thioctic acid, CAS 62-46-4) admixed at various amounts. The 50% survival rate, the total life span of each group and the areas under the curves were determined to evaluate life expectancy as compared to the controls. The racemate of lipoic acid at high dosage (350 mg/kg body weight) reduced the life span significantly. The S(-)-enantiomer of lipoic acid (75 mg/kg body weight) increased the 50% survival rate, whereas the physiologic R(+)-enantiomer (9 mg/kg body weight) expanded the total life span of its group. Alteration of only one out of three parameters was not considered significant. All other groups except for one did not differ from controls: only animals which obtained 75 micrograms selegiline per kg of body weight and per day exerted increased life expectancies by all three parameters. This group exhibited also in statistical evaluation a significantly (p < 0.05) prolongated survival time up to about 200% as compared to the control animals. 相似文献
2.
DI Timokhin AV Istomin TS Shushkova TG Voronel' IG Mikha?lov 《Canadian Metallurgical Quarterly》1997,(2):19-21
Based on generalization and analysis of instructions and guidelines for therapeutical and prophylactic diets of workers, ways of its optimization were proposed, by using bifide-containing acid dairy products as a preventive agent against possible occupational diseases caused by occupational factors. 相似文献
3.
Cancer statistics, 1993 总被引:1,自引:0,他引:1
4.
Howden W.E. Wieand B. 《IEEE transactions on pattern analysis and machine intelligence》1994,20(6):445-462
Formal verification of program properties may be infeasible or impractical, and informal analysis may be sufficient. Informal analysis involves the informal acceptance, by inspection, of the validity of program properties or steps in an analysis. Informal analysis may also involve abstraction. Abstraction can be used to eliminate details and concentrate on more general properties. Abstraction will result in informal analysis if it includes the use of undefined properties. A systematic, informal method for analysis called QDA (Quick Defect Analysis) is described. QDA is a comments analysis process based on facts and hypotheses. Facts are used to create an abstract program model, and hypotheses are selected, nonobvious program properties which are identified as needing verification. Hypotheses are proved from the facts that define an abstraction. QDA is hypothesis-driven in the sense that only those parts of an abstraction that are needed to prove hypotheses are created. The QDA approach was applied to a previously well tested operational flight program (OFP). The QDA method and the results of the OFP experiment are presented. The problems of incomplete or unsound informal analysis are analyzed, the relationship of QDA to other analysis methods is discussed, and suggested improvements to the QDA method are described 相似文献
5.
6.
1. alpha-toxin of Staphylococcus aureus readily permeabilized rat uterine smooth muscle after incubation for a short time. 2. The permeabilized muscle responded to Ca2+ dose-dependently and repeatedly in the same manner. 3. The threshold concentration of Ca2+ for contraction was 0.1-0.3 microM and the maximal contraction was achieved with 1 or 3 microM Ca2+. 4. GTP gamma S or GTP augmented the contractile response to Ca2+. 5. GDP beta S or GDP suppressed the contraction. 6. The role of GTP-binding protein in sensitization of Ca(2+)-induced contractile response of smooth muscle is discussed. 相似文献
7.
BACKGROUND: Noncutaneous psammomatous melanotic schwannoma has recently been reported as an unusual component of Carney's complex (myxomas, spotty pigmentation, and endocrinopathy). The most common locations for this lesion include peripheral nerve roots and the gastrointestinal tract. OBSERVATIONS: A cutaneous psammomatous melanotic schwannoma is reported in a patient with known Carney's complex. This neoplasm was pseudoencapsulated, with epithelioid to spindle-shaped cells and no nuclear atypia. Immunostaining was positive for S100 protein and vimentin, as well for HMB-45 antibody. Electron microscopy showed melanosomes in cytoplasmic processes of cells that were ensheathed by layers of reduplicated basal lamina. CONCLUSIONS: Location in the superficial soft tissues is extremely unusual for psammomatous melanotic schwannomas. Recognition of this new cutaneous marker as a part of this complex may aid in identification of individuals at risk for cardiac myxomas. It is also important that this lesion is not mistaken for melanoma, given the strong HMB-45 positivity. 相似文献
8.
In Study One, a sample of 230 college students were asked to estimate the abuse potential and lethality of commonly used recreational drugs, both licit and illicit. In Study Two, a sample of 103 degreed nurses were asked to estimate the lethality of the same recreational drugs. The findings indicate that the illicit drugs under consideration are perceived as presenting the greatest danger to the user and that dangers attributed to the use of licit recreational drugs are generally minimized. Perception of danger was found to be unaffected by exposure to reported drug education programs. Results are discussed in terms of public health implications. 相似文献
9.
10.
LW Delbridge NA Younes AI Guinea TS Reeve P Clifton-Bligh BG Robinson 《Canadian Metallurgical Quarterly》1998,168(4):153-156
Twenty-two cases of ameloblastoma and ten cases of adenomatoid odontogenic tumour (AOT) were analyzed comparatively by the AgNOR technique. Ameloblastomas were distributed into three groups according to their clinical behaviour: primary lesions without recurrences (PLWTR), 5 cases; primary lesions with recurrences (PLWR), 4 cases; and recurrences, 13 cases. The cases were also regrouped according to their histological pattern: follicular (9 cases), plexiform (7 cases), acanthomatous (4 cases) and unicystic (2 cases). Considering histological patterns, there was a significant statistical difference only between follicular and plexiform types. There were no significant differences between the group of ameloblastomas and the group of AOTs or between the three groups of ameloblastomas with different clinical behaviour. Our results strongly suggest that the distinct clinical behaviour of ameloblastomas and AOT is not correlated with their cellular proliferation ratio. Thus, the infiltrative ability of the ameloblastomas is probably not related to the cellular proliferation index of these tumours. 相似文献