首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3002篇
  免费   14篇
  国内免费   26篇
系统科学   51篇
丛书文集   2篇
教育与普及   14篇
理论与方法论   41篇
现状及发展   382篇
研究方法   383篇
综合类   2050篇
自然研究   119篇
  2021年   13篇
  2019年   11篇
  2018年   28篇
  2017年   17篇
  2016年   31篇
  2015年   24篇
  2014年   25篇
  2013年   50篇
  2012年   208篇
  2011年   374篇
  2010年   76篇
  2009年   11篇
  2008年   232篇
  2007年   241篇
  2006年   233篇
  2005年   266篇
  2004年   256篇
  2003年   196篇
  2002年   256篇
  2001年   14篇
  2000年   30篇
  1999年   23篇
  1997年   10篇
  1996年   9篇
  1995年   11篇
  1992年   18篇
  1991年   13篇
  1990年   7篇
  1989年   17篇
  1988年   9篇
  1986年   9篇
  1985年   11篇
  1984年   13篇
  1983年   15篇
  1982年   14篇
  1981年   12篇
  1979年   27篇
  1978年   18篇
  1977年   13篇
  1976年   12篇
  1975年   12篇
  1974年   18篇
  1973年   18篇
  1972年   13篇
  1971年   15篇
  1970年   18篇
  1969年   10篇
  1968年   9篇
  1967年   16篇
  1966年   14篇
排序方式: 共有3042条查询结果,搜索用时 0 毫秒
121.
Curie’s Principle says that any symmetry property of a cause must be found in its effect. In this article, I consider Curie’s Principle from the point of view of graphical causal models, and demonstrate that, under one definition of a symmetry transformation, the causal modeling framework does not require anything like Curie’s Principle to be true. On another definition of a symmetry transformation, the graphical causal modeling formalism does imply a version of Curie’s Principle. These results yield a better understanding of the logical landscape with respect to the relationship between Curie’s Principle and graphical causal modeling.  相似文献   
122.
This paper develops quantum state individualism, a fundamental ontology for what is usually known as ‘orthodox quantum mechanics.’ The central import of this ontology is that allows for a systematic evaluation of some of the main conclusions of the recent literature on quantum metaphysical indeterminacy. In particular, quantum state individualism supports the ‘gappy’ version of Jessica Wilson's determinable-based account of metaphysical indeterminacy; it implies that fundamental reality is perfectly precise; and third, it provides a non-disjunctive definition of determinables and thereby shields Wilson's account against the charge that it requires either a departure from classical logic or a revision of the quantum formalism.  相似文献   
123.
We have each spent more than 50 years doing research that has had little impact. Even more lamentable is that our field, judgment and decision making (JDM), has on the whole had little impact during that span. We attribute that failure to the use of methodologies that emphasize testing models rather than looking for differences in behavior. The “cognitive revolution” led the field astray, toward the goal of studying model fit rather than comparing observable results. With modeling as the goal, experimentation was stultified. Simple tasks became dominant. Although a poor metaphor for real decision making, the gambling paradigm has lasted forever because the inputs to the decision are known to the researcher and thus easily modeled.  相似文献   
124.
125.
126.
127.
A reinvestigation of the type specimen of Araucarioxylon? obscurum Knowlton (1900) from the Upper Jurassic Morrison Formation in the Freezeout Hills of Wyoming has determined that this fossil should be transferred to Mesembrioxylon Seward (1919) as M. obscurum comb. nov. (Knowlton) Medlyn and Tidwell. Knowlton (1900), who was uncertain of its appropriate generic disposition, tentatively referred the wood to Araucarioxylon because it had obscure growth rings and relatively low ray height. Reexamination of Knowltons slides demonstrates that the wood has uniseriate, rarely biseriate rays, podocarpoid pitting, and diffuse axial parenchyma, none of which Knowlton mentioned. Tracheary pitting is mostly separate, round, uniseriate, occasionally biseriate and, when biseriate, opposite to subopposite. The smooth-walled crossfields exhibit 1-3 thin-bordered podocarpaceous pits per field. All of these features are present in Mesembrioxylon Seward.  相似文献   
128.
Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 st1\:*{behavior:url(#ieooui) } /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Four near-surface locations in Pyramid Lake, Nevada, were sampled for larval tui chubs ( Gila bicolor ) during summer and early fall 1979. Numbers of larvae collected were highest in mid-July. Zooplankton was the only food eaten throughout the survey; the cladoceran Moina hutchinsoni was the major species eaten at all locations. Another cladoceran, Diaphanosoma leuchtenbergianum, was also important to the diet of pelagic larvae, and the copepod Cyclops vernalis was eaten in significant quantities by nearshore fish. Changes in diet composition of larval tui chubs during summer corresponded to seasonal succession of zooplankton species in Pyramid Lake.  相似文献   
129.
130.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号