全文获取类型
收费全文 | 18060篇 |
免费 | 97篇 |
国内免费 | 229篇 |
专业分类
系统科学 | 383篇 |
丛书文集 | 382篇 |
教育与普及 | 72篇 |
理论与方法论 | 60篇 |
现状及发展 | 6257篇 |
研究方法 | 776篇 |
综合类 | 9935篇 |
自然研究 | 521篇 |
出版年
2014年 | 140篇 |
2013年 | 278篇 |
2012年 | 480篇 |
2011年 | 1014篇 |
2010年 | 360篇 |
2009年 | 343篇 |
2008年 | 528篇 |
2007年 | 612篇 |
2006年 | 607篇 |
2005年 | 544篇 |
2004年 | 399篇 |
2003年 | 308篇 |
2002年 | 317篇 |
2001年 | 507篇 |
2000年 | 559篇 |
1999年 | 411篇 |
1992年 | 288篇 |
1991年 | 252篇 |
1990年 | 250篇 |
1989年 | 229篇 |
1988年 | 209篇 |
1987年 | 226篇 |
1986年 | 203篇 |
1985年 | 245篇 |
1984年 | 235篇 |
1983年 | 159篇 |
1982年 | 172篇 |
1981年 | 157篇 |
1980年 | 199篇 |
1979年 | 449篇 |
1978年 | 343篇 |
1977年 | 367篇 |
1976年 | 264篇 |
1975年 | 322篇 |
1974年 | 448篇 |
1973年 | 379篇 |
1972年 | 360篇 |
1971年 | 421篇 |
1970年 | 484篇 |
1969年 | 425篇 |
1968年 | 407篇 |
1967年 | 443篇 |
1966年 | 384篇 |
1965年 | 301篇 |
1959年 | 155篇 |
1958年 | 231篇 |
1957年 | 179篇 |
1956年 | 138篇 |
1955年 | 154篇 |
1954年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Taking a cue from remarks Thomas Kuhn makes in 1990 about the historical turn in philosophy of science, I examine the history of history and philosophy of science within parts of the British philosophical context in the 1950s and early 1960s. During this time, ordinary language philosophy's influence was at its peak. I argue that the ordinary language philosophers' methodological recommendation to analyze actual linguistic practice influences several prominent criticisms of the deductive-nomological model of scientific explanation and that these criticisms relate to the historical turn in philosophy of science. To show these connections, I primarily examine the work of Stephen Toulmin, who taught at Oxford from 1949 to 1954, and Michael Scriven, who completed a dissertation on explanation under Gilbert Ryle and R.B. Braithwaite in 1956. I also consider Mary Hesse's appeal to an ordinary language-influenced account of meaning in her account of the role of models and analogies in scientific reasoning, and W.H. Watson's Wittgensteinian philosophy of science, an early influence on Toulmin. I think there are two upshots to my historical sketch. First, it fills out details of the move away from logical positivism to more historical- and practice-focused philosophies of science. Second, questions about linguistic meaning and the proper targets and aims of philosophical analysis are part and parcel of the historical turn, as well as its reception. Looking at the philosophical background during which so-called linguistic philosophers also had a hand in bringing these questions to prominence helps us understand why. 相似文献
133.
In this paper, we shall describe a new account of information in communicational contexts, namely, a causal-deflationary one. Our approach draws from Timpson's deflationary view and supplies the field of philosophy of information with new tools that will help to clarify the underlying structure of communication: information is an abstract entity that must be involved in a causal link in order to achieve communication. In light of our account, communication is not merely the existence of statistical correlations between source and receiver, as usually understood from a purely formal view. Instead, communication is an asymmetric phenomenon involving causal notions: the destination system must be able to be causally manipulated by intervening on the source for successful communication. In a nutshell, we shall support the following lemma: no communication without manipulation. 相似文献
134.
Steven J. Collins Carolin Tumpach Bradley R. Groveman Simon C. Drew Cathryn L. Haigh 《Cellular and molecular life sciences : CMLS》2018,75(17):3231-3249
Neurogenesis continues in the post-developmental brain throughout life. The ability to stimulate the production of new neurones requires both quiescent and actively proliferating pools of neural stem cells (NSCs). Actively proliferating NSCs ensure that neurogenic demand can be met, whilst the quiescent pool makes certain NSC reserves do not become depleted. The processes preserving the NSC quiescent pool are only just beginning to be defined. Herein, we identify a switch between NSC proliferation and quiescence through changing intracellular redox signalling. We show that N-terminal post-translational cleavage products of the prion protein (PrP) induce a quiescent state, halting NSC cellular growth, migration, and neurite outgrowth. Quiescence is initiated by the PrP cleavage products through reducing intracellular levels of reactive oxygen species. First, inhibition of redox signalling results in increased mitochondrial fission, which rapidly signals quiescence. Thereafter, quiescence is maintained through downstream increases in the expression and activity of superoxide dismutase-2 that reduces mitochondrial superoxide. We further observe that PrP is predominantly cleaved in quiescent NSCs indicating a homeostatic role for this cascade. Our findings provide new insight into the regulation of NSC quiescence, which potentially could influence brain health throughout adult life. 相似文献
135.
Jana Fischer Gunnar Kleinau Claudia Rutz Denise Zwanziger Noushafarin Khajavi Anne Müller Maren Rehders Klaudia Brix Catherine L. Worth Dagmar Führer Heiko Krude Burkhard Wiesner Ralf Schülein Heike Biebermann 《Cellular and molecular life sciences : CMLS》2018,75(12):2227-2239
G-protein-coupled receptors (GPCRs) can constitute complexes with non-GPCR integral membrane proteins, while such interaction has not been demonstrated at a single molecule level so far. We here investigated the potential interaction between the thyrotropin receptor (TSHR) and the monocarboxylate transporter 8 (MCT8), a member of the major facilitator superfamily (MFS), using fluorescence cross-correlation spectroscopy (FCCS). Both the proteins are expressed endogenously on the basolateral plasma membrane of the thyrocytes and are involved in stimulation of thyroid hormone production and release. Indeed, we demonstrate strong interaction between both the proteins which causes a suppressed activation of Gq/11 by TSH-stimulated TSHR. Thus, we provide not only evidence for a novel interaction between the TSHR and MCT8, but could also prove this interaction on a single molecule level. Moreover, this interaction forces biased signaling at the TSHR. These results are of general interest for both the GPCR and the MFS research fields. 相似文献
136.
137.
Juliana L. Segadilha Priscila S. Nascimento Fábio M. Mauro Cristiana S. Serejo Taiara R. Ramos Irene A. Cardoso 《Journal of Natural History》2018,52(1-2):1-11
A total of 3109 crustaceans belonging to 50 taxa distributed in 42 families were found in 117 analysed stomachs of flying gurnard (Dactylopterus volitans). Samples were obtained in April 2008 by the R/V Gyre using a bottom trawl towed in 12 stations at 14–100 m depth on the continental shelf of the Campos Basin, Brazil. The carcinofauna was analysed and the order Calanoida (Copepoda) found to be the most important item in terms of relative abundance and frequency of occurrence, followed by the order Amphipoda (Peracarida), the infraorder Brachyura (Decapoda), the order Stomatopoda and the subclass Myodocopa (Ostracoda). In the order Calanoida, the species Pontellopsis cf. villosa (Pontellidae) represented 98.04% of total crustacean abundance. The diet of Dactylopterus volitans varied according to fish size, with higher diversity of Crustacea at smaller size classes, decreasing in larger fishes. A similar pattern regarding depth was obtained, with greater diversity of taxa in gurnard stomachs caught at shallower depths. Flying gurnard is considered a generalized carnivore of invertebrates, eating mobile macrobenthic organisms, such as crustaceans, and its diet varies with its life stage, without any specific group as its main food source. 相似文献
138.
Z. Campos F. Muniz A. L. J Desbiez W. E. Magnusson 《Journal of Natural History》2016,50(25-26):1543-1548
Nests of Schneider’s dwarf caiman, Paleosuchus trigonatus, were located in the forests around three streams that drain into the Xingu River, Brazilian Amazonia, in October 2014. Camera traps were installed at the edge of four nests to document predators and female parental care. At two nests, females unsuccessfully defended their nests against one or more giant armadillos, Priodontes maximus, and nine-banded armadillos, Dasypus novemcinctus. Both armadillo species responded to the attack by fleeing and returning on the opposite side of the nest by going around the tree under which the nest was located. Giant armadillos have never before been recorded consuming caiman eggs and their diet has been described as consisting mostly of ants and termites. Another species of armadillo, Cabassous unicinctus, was also registered digging into a nest and probably consuming eggs, though it is generally considered to be primarily insectivorous. A tayra (Eira barbara), lizard (Tupinambis teguixin) and coati (Nasua nasua) were also registered taking eggs from nests during the day, but we obtained no registers of nest defence by caimans during the day. The three nests were attacked after 60 days of incubation, when the eggs were well developed. 相似文献
139.
Gandhi TK Zhong J Mathivanan S Karthick L Chandrika KN Mohan SS Sharma S Pinkert S Nagaraju S Periaswamy B Mishra G Nandakumar K Shen B Deshpande N Nayak R Sarker M Boeke JD Parmigiani G Schultz J Bader JS Pandey A 《Nature genetics》2006,38(3):285-293
We present the first analysis of the human proteome with regard to interactions between proteins. We also compare the human interactome with the available interaction datasets from yeast (Saccharomyces cerevisiae), worm (Caenorhabditis elegans) and fly (Drosophila melanogaster). Of >70,000 binary interactions, only 42 were common to human, worm and fly, and only 16 were common to all four datasets. An additional 36 interactions were common to fly and worm but were not observed in humans, although a coimmunoprecipitation assay showed that 9 of the interactions do occur in humans. A re-examination of the connectivity of essential genes in yeast and humans indicated that the available data do not support the presumption that the number of interaction partners can accurately predict whether a gene is essential. Finally, we found that proteins encoded by genes mutated in inherited genetic disorders are likely to interact with proteins known to cause similar disorders, suggesting the existence of disease subnetworks. The human interaction map constructed from our analysis should facilitate an integrative systems biology approach to elucidating the cellular networks that contribute to health and disease states. 相似文献
140.
Sung LY Gao S Shen H Yu H Song Y Smith SL Chang CC Inoue K Kuo L Lian J Li A Tian XC Tuck DP Weissman SM Yang X Cheng T 《Nature genetics》2006,38(11):1323-1328
Since the creation of Dolly via somatic cell nuclear transfer (SCNT), more than a dozen species of mammals have been cloned using this technology. One hypothesis for the limited success of cloning via SCNT (1%-5%) is that the clones are likely to be derived from adult stem cells. Support for this hypothesis comes from the findings that the reproductive cloning efficiency for embryonic stem cells is five to ten times higher than that for somatic cells as donors and that cloned pups cannot be produced directly from cloned embryos derived from differentiated B and T cells or neuronal cells. The question remains as to whether SCNT-derived animal clones can be derived from truly differentiated somatic cells. We tested this hypothesis with mouse hematopoietic cells at different differentiation stages: hematopoietic stem cells, progenitor cells and granulocytes. We found that cloning efficiency increases over the differentiation hierarchy, and terminally differentiated postmitotic granulocytes yield cloned pups with the greatest cloning efficiency. 相似文献