共查询到20条相似文献，搜索用时 187 毫秒
1.
Nuclear weapons that are safe and secure, reliable, survivable, and effective will be a critical element of this nation's deterrent for the foreseeable future. The existence of these weapons reflects the tension that exists between the United States and the Soviet Union. Nuclear test bans will not reduce or eliminate nuclear weapons or this tension. Imprudent nuclear test bans, however, could impair the viability of this vital element of U.S. security. New, more restrictive test limitations would not enhance our national security. They do not address the two most important issues-namely, major reductions in strategic and conventional forces of both the Soviet Union and the United States, and a widespread lessening of tension between our two countries. In fact, it is conceivable that the diversion of political attention from arms reduction efforts and the distrust generated by test-ban verification problems could actually increase tensions between the two countries. We believe that more restrictive test limitations or a nuclear test ban should be considered only as part of an integrated and comprehensive approach to arms control. We must reduce the numbers of the most destabilizing weapons and the overall size of the strategic arsenals through negotiations. A restrictive test ban may be a proper last step in our quest for nuclear arms control and a stable peace, but it would, in our opinion, be an imprudent first step. Further test limitations will be consistent with increased stability and decreased tension between the United States and the Soviet Union only if they are instituted after major stabilizing reductions are made in the strategic nuclear and conventional forces of both countries. 相似文献
2.
枝叶油对四纹豆象成虫的产卵趋避及熏蒸作用研究 总被引：1，自引：0，他引：1
[目的]探讨桉叶油对四纹豆象[Callosobruchus maculates(Fabricius)]成虫的产卵趋避及熏蒸作用。[方法]采用简化后的干扰作用控制指数(IIPC)作为评价指标,评价了桉叶油对四纹豆象成虫的产卵趋避作用,并采用药纸熏蒸法测定了桉叶油及其主要成分1,8-桉叶素对四纹豆象成虫的熏蒸毒杀作用。[结果]桉叶油对四纹豆象成虫具有显著的产卵驱避作用,在800μg/cm2的剂量下24 h的产卵IIPC达0.204 5。桉叶油及1,8-桉叶素对四纹豆象成虫均具有强烈的熏蒸毒杀作用,24 h的LC50分别为3.28和3.30 mg/L,而72 h的LC50仅分别为1.83和2.08 mg/L。[结论]为非嗜食性植物次生物质在害虫控制中的利用研究以及对植物次生物质作为粮食保护剂的生产应用提供了理论依据。 相似文献
3.
李红梅 《安徽农业大学学报》2004,(5):129-133
英语中的歧义现象，根据成因可分为语音歧义，词汇歧义，句法歧义等。探讨英语中的歧义现象的成因及排除方法，有助于我们阅读、翻译、教学和交际。 相似文献
4.
[目的]为了评估稀土元素对鱼类的长期潜在影响。[方法]利用半静态致死法研究了镧对鲤鱼的急性毒性。将鲤鱼暴露于0.01、0.10、2.00、5.00mg/L的La3+溶液中4个月,用来研究镧对鲤鱼外周血细胞数量及红细胞微核和核异常的影响。[结果](1)La3+对鲤鱼24、48、72、96h的半致死浓度分别为13.20、11.90、11.90、11.49mg/L;96h的安全浓度为1.149mg/L。(2)0.01、0.10mg/L组红细胞微核率、总核异常率,0.1mg/L组核异常率均显著低于对照(P<0.05),5.00mg/L组核异常率显著高于对照(P<0.05)。(3)各La3+处理组较对照组红细胞数显著增多(P<0.01)。0.01mg/L组白细胞数较对照组也显著增多,5.00mg/L组白细胞数却显著低于对照(P<0.05);[结论]镧属低毒物质,在La3+的长期暴露下,镧能使血细胞数量发生变化,较低浓度的镧不具遗传毒性。 相似文献
5.
金点九 《黑龙江八一农垦大学学报》2006,18(1):70-74
保证可信度的评价标准得到了统一,但各国的评价方法等客观性的保证方面上的一些部分还是有点模糊。换言之,脆弱性评价有范围,深度,实验用道具,提纲和评价者因素,而随着这些因素的不同其评价结果也会出现差异,这样一来,评价的公正性和客观性的保证上就存在困难。本论文提出了能保证信息保护产品保安脆弱性评价的公正性客观性和效率性的信息保护产品保安脆弱性评价方法,体现了自动化完成评价系统的设计。 相似文献
6.
伍德林 《安徽农业大学学报》2004,(4):11-14
十六大报告中把“三个代表”重要思想作为我党的指导思想。在当前席卷全球新军事变革的时期，这一重要思想为如何使人民战争迸发出新的活力、为克敌制胜指明了方向。始终代表中国先进生产力的发展要求是实现人民战争的正义性基础:代表中国先进文化的前进方向是打牢人民战争的思想基础;代表中国最广大人民的根木利益是实现人民战争的群众基础:全面贯彻“三个代表”重要思想是实现党对人民战争领导的根本途径。 相似文献
7.
Our foregoing analysis of the role of a comprehensive test ban leads us to the following conclusions. 1) A CTB by itself will have little direct effect on the arms race between the superpowers. It would not hinder their nuclear arms production and deployment nor would it necessarily present a significant obstacle to the development of new nuclear weapons systems, despite limiting the development of new nuclear warhead designs. It can hardly make a dent in the destructive capability of the superpowers or in their ability to step up the pace of the arms race. 2) The chief merits of a CTB reside in the political sphere. It would help promote detente and could help to escalate interest in arms control agreements of broader scope. But in neither of these effects would it be as significant as a successful SALT (strategic arms limitation talks) agreement. The CTB also lingers as a piece of unfinished business since the signing of the LTB in 1963. The question can be and has been raised, "If the superpowers are serious about arms control, why have they not accepted the CTB, which is simple in concept and in form and is also free of serious military risks?" Such doubts about the sincerity of the superpowers' willingness to limit their own arms development will persist as long as there is no CTB. Substantial agreement at SALT would lessen some of this effect too, but would not eliminate it completely. 3) Recent progress in seismic identification has been impressive, and other means of obtaining technical intelligence about nuclear testing have probably also improved greatly. In addition, research on the technical means of on-site inspection has demonstrated its limited effectiveness. Therefore, the role of on-site inspections as an added deterrent to cheating on a CTB has diminished substantially. This is not to say that detection and identification of all nuclear tests is possible now, or ever, but only that on-site inspection would add very little to the other technical means now available for verification. 4) It will become increasingly difficult in the United States to oppose the CTB on the basis of risks that accompany possible Soviet evasion of a treaty that does not include the right of onsite inspection. The opposition to a CTB is now likely to shift to the more direct argument that nuclear testing is important to keep pace with continuing worldwide technical and military developments. The justification for U.S. testing is only in part because of advances in Soviet nuclear technology per se. Those opposing a CTB may argue that it makes little sense, and may even be courting danger, to freeze nuclear technology alone and that banning nuclear tests should await an agreement that copes with all military research and development and all qualitative improvements in weapons systems. This directly confronts the argument that the unique virtue of a CTB is that it provides a simple and feasible first step in the very complicated problems of controlling military technology. 5) The mutual deterrence of the superpowers will not be compromised if a CTB agreement is reached and one side or the other clandestinely violates such an agreement. The state of nuclear technology in both countries is mature, and the destructive capability of their nuclear arsenals can be easily maintained. Whatever small improvements can come as a consequence of clandestine testing would hardly affect the strategic balance. 6) It seems unlikely that China and France will agree to stop testing in the near future. These countries refused to join the nonproliferation treaty, which did not affect their nuclear programs, and it is doubtful that, proceeding from military considerations alone, they would join a CTB. Their nuclear programs are still not mature, and a CTB would freeze their positions of inferiority with respect to the superpowers. There may, however, be wider political and security arrangements to induce them to participate. Cessation of tests by the other nuclear powers might serve as an inducement to China and France to refrain from testing. 7) The key near-nuclear powers, such as Japan, India, and Israel, are much more concerned with the military activities of their neighbors than they are with those of the superpowers. The modest nuclear restraints that a CTB imposes on the superpowers are hardly likely to have a direct impact on the approach of these countries to their own security. However, for these critical near-nuclear countries a CTB may be much more acceptable than the nonproliferation treaty. A CTB would not prohibit the production of fissionable material, the development of nuclear weapons technology short of testing, nor the stockpiling of untested nuclear weapons, and is therefore less restrictive. Consequently, these powers may be willing to ratify a CTB, but not the nonproliferation treaty. On the other hand, the CTB may provide them with a ready excuse for not succumbing to the pressure to ratify the nonproliferation treaty, if indeed they need excuses or would bow to such pressure. 8) A CTB is of very little added, direct significance to other nonnuclear powers who have already ratified or are about to ratify the nonproliferation treaty. It may only lessen their pique about the treaty's being highly discriminatory-the treaty imposes no restraints on the nuclear weapons programs of the nuclear powers, while the CTB restricts all parties to the agreement. 9) Peaceful nuclear explosions do not now show great promise and significance for economic development. What can be done with peaceful explosions can often be done by other means, although possibly at a slightly higher cost. On the other hand, making allowance for peaceful explosions greatly complicates a CTB. A useful approach to the problem of banning military tests but not foregoing indefinitely the use of peaceful explosions might, therefore, be to ban all nuclear explosions for a period of several years and to stipulate in the agreement that in that time there would be negotiations on how peaceful explosions may be controlled in a way that would not jeopardize the CTB. 相似文献
8.
Tycko R Dabbagh G Rosseinsky MJ Murphy DW Fleming RM Ramirez AP Tully JC 《Science (New York, N.Y.)》1991,253(5022):884-886
The results of (13)C nuclear magnetic resonance (NMR) measurements on alkali fullerides KxC(60) are reported. The NMR spectra demonstrate that material with 0 < x < 3 is in fact a two-phase system at equilibrium, with x = 0 and x = 3. NMR lineshapes indicate that C(3-)(60) ions rotate rapidly in the K(3)C(60) phase at 300 K, while C(6)-(60) ions in the insulating K(6)C(60) phase are static on the time scale of the lineshape measurement. The temperature dependence of the (13)C spin-lattice relaxation rate in the normal state of K(3)C(60) is found to be characteristic of a metal, indicating the important role of the C(3-)(60) ions in the conductivity. From the relaxation measurements, an estimate of the density of electronic states at the Fermi level is derived. 相似文献
9.
呈味物质是人类经过漫长筛选形成的味感强烈的物质,可能在调控害虫取食行为中发挥重要作用,但传统的二分式定性法难以阐明其对昆虫味觉反应的复杂相互作用。为此,以菜粉蝶为研究对象,采用叶碟法结合正交设计测试了6种人类呈味物质(柠檬酸、蔗糖、奎宁、氯化钠、山椒醇和辣椒素)对菜粉蝶幼虫取食反应的影响。单一呈味物质与对照叶碟的配对测试表明,拒食反应指数较高的呈味物质为柠檬酸(93.89%)、奎宁(90.33%)、山椒醇(83.33%),但正交测试却发现辣椒素、蔗糖、山椒醇影响较大,且奎宁和氯化钠可能相互拮抗。进一步采用对菜粉蝶幼虫取食量影响较大的4种呈味物质进行选择性取食和非选择性取食测定,发现辣椒素效应最大。2种条件下均表现出较强拒食活性的样品组合为蔗糖9μL+山椒醇9μL+辣椒素3μL+柠檬酸12μL。结果表明,特定呈味物质在单剂刺激和混合刺激下的表现存在较大差异,利用多因素试验设计方法优化多元组分的拒食剂,可能有助于解决害虫味觉反应习惯化的问题。 相似文献
10.
苦瓜SRAP反应体系的建立与优化 总被引：6，自引：0，他引：6
[目的]分子标记技术的快速发展为在DNA水平上估计苦瓜种质的遗传差异提供了更准确、更高效的方法。[方法]采用正交试验设计,对影响苦瓜SRAP反应体系的5种因素(Mg2+、dNTPs、引物、Taq聚合酶及模板DNA)4个水平进行优化筛选。[结果]确立了适合苦瓜SRAP分析的优化反应体系,即1×buffer,1.0 ng/μl模板DNA,1.5 mmol/L Mg2+,0.3 mmol/L dNTPs,0.5μmol/L引物,0.075 U/μlTaq聚合酶,总体积20μl。[结论]优化的SRAP-PCR反应体系的建立为利用SRAP技术进行苦瓜种质资源分类、遗传图谱构建和基因定位奠定了技术基础。 相似文献
11.
通用试题库管理系统的设计及应用 总被引：1，自引：0，他引：1
张丽 《山西农业大学学报(自然科学版)》1998,18(1):17-19
本文介绍一个通用的试题库管理系统,该系统集制题、命题、试卷分析三个子系统为一体,是建立优秀的计算机命题题库的一个良好的工具。软件采用ＣＬＩＰＰＥＲ和Ｃ语言编程,菜单控制,窗口对话,操作简单,实用可靠。该系统已经在我校和我省一些中等专业学校使用多年,效果良好。 相似文献
12.
Broad WJ 《Science (New York, N.Y.)》1981,212(4499):1116-1120
Defense strategists today assume that a single Soviet warhead detonated 200 miles above Nebraska would knock out unprotected communications equipment all across the United States. The reason is electromagnetic pulse (EMP), a by-product of high-altitude nuclear explosions that blankets huge tracts of the earth with peak fields of 50,000 volts per meter. The first installment of this three-part series described how EMP was discovered and why its potentially chaos-producing effects were overlooked for more than a decade. The second part examines the ongoing debate in the Pentagon over how to cope with the EMP threat. The third part will discuss questions EMP raises about waging a limited nuclear war. 相似文献
13.
天津滨海园林绿化中盐土治理的理论及工艺 总被引：11，自引：1，他引：11
在季风气候的影响下 ,天津滨海地区土壤剖面上盐分的运动具有周期性 ,而且在园林绿化建设中可以有目的地选择耐盐植物 .该文根据“临界深度”理论提出了用来指导该地区在园林绿化建设时治理盐土的“允许积盐”概念 ,其基本含义是如果积盐阶段并没有使植物根系活动层的盐分增加到马上危害植物的程度 ,即为随后的脱盐过程所消除 ,那么这种积盐是可以允许发生的 .相对应地 ,在确定排盐系统的埋深时 ,存在一个“允许深度” .天津开发区具有土壤基质软、潜水埋深浅、海水容易回浸等特殊水文地质条件 ,盐土的治理只能选择“允许深度”作为铺设排盐管的指导依据 ,并与开发区城市园林绿化建设相适应 ,建立了“浅密式”排盐系统 相似文献
14.
我国小麦根腐性病害研究现状及防治对策 总被引：31，自引：0，他引：31
系统论述了我国小麦根腐性病害的研究现状，内容包括：（1）发生、分布及危害；（2）根病危害上升的原因；（3）病原学及发病规律；（4）根病防治对策。重点介绍了危害我国小麦的4类根病，即全蚀病、纹枯病、镰孢菌根腐病、蠕孢菌根腐病。小麦根病的防治应立足于土壤生态控制，增施有机肥和磷钾肥，选用抗耐病品种，实施健身栽培，以及应用三唑类内吸杀菌剂拌种。 相似文献
15.
省级政府投融资平台公司在城镇化建设中发挥着重要作用,其投融资风险问题亦逐渐引起重视。基于平台公司的投资收益会随着市场等宏观环境的变化而波动的考虑,将平台公司的项目投资资产视为金融资产而度量其风险状况。考虑单笔投资的情形,建立极值理论和SV-t模型的相结合平台公司一维融资风险动态VaR模型;进而考虑多笔投资间的非线性关系,结合Copula函数和蒙特卡洛模拟思路,建立平台公司多维融资风险度量模型。所构建的模型避免了传统研究的强主观性,并实现了投资风险的实时、动态度量。 相似文献
16.
The behavior of smoke injected into the atmosphere by massive fires that might follow a nuclear war was simulated. Studies with a three-dimensional global atmospheric circulation model showed that heating of the smoke by sunlight would be important and might produce several effects that would decrease the efficiency with which precipitation removes smoke from the atmosphere. The heating gives rise to vertical motions that carry smoke well above the original injection height. Heating of the smoke also causes the tropopause, which is initially above the smoke, to reform below the heated smoke layer. Smoke above the tropopause is physically isolated from precipitation below. Consequently, the atmospheric residence time of the remaining smoke is greatly increased over the prescribed residence times used in previous models of nuclear winter. 相似文献
17.
玉米联合收获机电子监视系统的设计研究 总被引：1，自引：1，他引：0
玉米收获机在田间作业时,发生机械传动故障,特别是某些部位堵塞以后,不能及时排除故障而影响作业效率。针对这一问题,研制了4KY-3型玉米联合收获机械电子监视系统,监视发动机轴的转速,对各工作轴转速下降报警,使驾驶员及时发现故障,并排除故障。该转速监视系统具有结构简单,工作可靠,成本低的优点。 相似文献
18.
Cyclization of the phosphate side chain of adenosine triphosphate: formation of monoadenosine 5'-trimetaphosphate 总被引：1，自引：0，他引：1
Monoadenosine 5'-trimetaphosphate has been prepared from adeno-sine 5'-triphosphate by a carbodiimide-mediated condensation. The molecule was characterized by (3l)P nuclear magnetic resonance, and its (31)P spectrum was simulated through the assumption of a three-phosphorus spin system. The molecule is highly reactive and is rapidly converted to adenosine triphosphate upon contact with water. 相似文献
19.
20.
An inverse relationship between a volume estimated to be associated with interphase chromosomes and acute lethal exposure to x-or gamma radiation has been found in 16 plant species. The apparent differences in radiosensitivities found would seem spurious, since the estimated average energy absorbed in the nucleus per chromosome (3.6 x 10(6) ev) approaches a constant (variation less than fourfold) in spite of wide ranges of lethal exposures (0.6 to 75 kr), of nuclear volumes (43 to 1758 micro(3)), and of somatic chromosome numbers (6 to 136). The regression line obtained can be used to predict the radiosensitivities of other plant species if their nuclear volumes and chromosome numbers are known. 相似文献