全文获取类型
收费全文 | 35206篇 |
免费 | 83篇 |
国内免费 | 87篇 |
专业分类
系统科学 | 334篇 |
丛书文集 | 852篇 |
教育与普及 | 75篇 |
理论与方法论 | 107篇 |
现状及发展 | 15848篇 |
研究方法 | 1299篇 |
综合类 | 16366篇 |
自然研究 | 495篇 |
出版年
2013年 | 168篇 |
2012年 | 415篇 |
2011年 | 945篇 |
2010年 | 176篇 |
2008年 | 519篇 |
2007年 | 611篇 |
2006年 | 585篇 |
2005年 | 604篇 |
2004年 | 537篇 |
2003年 | 595篇 |
2002年 | 492篇 |
2001年 | 1090篇 |
2000年 | 1111篇 |
1999年 | 634篇 |
1992年 | 637篇 |
1991年 | 538篇 |
1990年 | 578篇 |
1989年 | 513篇 |
1988年 | 547篇 |
1987年 | 562篇 |
1986年 | 547篇 |
1985年 | 715篇 |
1984年 | 525篇 |
1983年 | 449篇 |
1982年 | 396篇 |
1981年 | 435篇 |
1980年 | 540篇 |
1979年 | 1131篇 |
1978年 | 929篇 |
1977年 | 923篇 |
1976年 | 726篇 |
1975年 | 813篇 |
1974年 | 1111篇 |
1973年 | 939篇 |
1972年 | 906篇 |
1971年 | 1093篇 |
1970年 | 1448篇 |
1969年 | 1187篇 |
1968年 | 1019篇 |
1967年 | 1073篇 |
1966年 | 946篇 |
1965年 | 694篇 |
1964年 | 181篇 |
1959年 | 419篇 |
1958年 | 652篇 |
1957年 | 461篇 |
1956年 | 407篇 |
1955年 | 369篇 |
1954年 | 400篇 |
1948年 | 253篇 |
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
51.
52.
53.
54.
55.
A New Discipline of Science-The Study of Open Complex Giant System and Its Methodology 总被引:2,自引:0,他引:2
Qian XuesenChina Association for Science Technology Beijing ChinaYu JingyuanBeijing Institute of Information Control P.O.Box Beijing ChinaDai RuweiInstitute of Automation Chinese Academy of Sciences Beijing China 《系统工程与电子技术(英文版)》1993,(2)
This paper introduces the conception of open complex giant system and the methodology for dealing with the system, with stress on its profound significance in development of science and technology. The authors conclude that the reductionism underlying the exact science is not suitable to open complex giant system, and the only feasible alternative is the meta-synthetic engineering from the qualitative to the quantitative. 相似文献
56.
The effects of alcohol consumption, cigarette smoking and age on sister chromatid exchange (SCE) frequency in human lymphocytes were assessed by means of multiple linear regression. An increase in SCE rates was associated with alcohol consumption (p = 0.0001), smoking (p = 0.0231), and, to a small extent (p = 0.057), age. These three confounding factors explain 48% of the inter-personal variation in SCE rates among subjects studied. 相似文献
57.
58.
T R Garbe 《Experientia》1992,48(7):635-639
Invasive microorganisms encounter defensive attempts of the host to starve, destroy and eliminate the infection. In experimental model systems aiming to imitate defensive actions of the host, microorganisms respond by the rapid acceleration in the rate of expression of heat shock and other stress proteins. Heat shock proteins (hsp) of most if not all pathogens are major immune targets for both B- and T-cells. Host cells involved in the defensive action cannot avoid exposure to their own reactive compounds, such as oxygen radicals, resulting in premature cell death and tissue damage. Long-term consequences to the host may include cancer. In cells in tissue culture, induction of host-specific hsps occurs upon exposure to oxidants and in viral infections. Drugs that bind to members of the hsp70 family induce peroxisome proliferation and hepatocarcinoma, but may open the way for the development of novel drugs in support of antimetabolite treatment of infections and cancer. 相似文献
59.
J A Martignetti A A Aqeel W A Sewairi C E Boumah M Kambouris S A Mayouf K V Sheth W A Eid O Dowling J Harris M J Glucksman S Bahabri B F Meyer R J Desnick 《Nature genetics》2001,28(3):261-265
The inherited osteolyses or 'vanishing bone' syndromes are a group of rare disorders of unknown etiology characterized by destruction and resorption of affected bones. The multicentric osteolyses are notable for interphalangeal joint erosions that mimic severe juvenile rheumatoid arthritis (OMIMs 166300, 259600, 259610 and 277950). We recently described an autosomal recessive form of multicentric osteolysis with carpal and tarsal resorption, crippling arthritic changes, marked osteoporosis, palmar and plantar subcutaneous nodules and distinctive facies in a number of consanguineous Saudi Arabian families. We localized the disease gene to 16q12-21 by using members of these families for a genome-wide search for homozygous-by-descent microsatellite markers. Haplotype analysis narrowed the critical region to a 1.2-cM region that spans the gene encoding MMP-2 (gelatinase A, collagenase type IV; (ref. 3). We detected no MMP2 enzymatic activity in the serum or fibroblasts of affected family members. We identified two family-specific homoallelic MMP2 mutations: R101H and Y244X. The nonsense mutation effects a deletion of the substrate-binding and catalytic sites and the fibronectin type II-like and hemopexin/TIMP2 binding domains. Based on molecular modeling, the missense mutation disrupts hydrogen bond formation within the highly conserved prodomain adjacent to the catalytic zinc ion. 相似文献
60.
Induction of hemopoietic chimerism in the caprine fetus by intraperitoneal injection of fetal liver cells 总被引:1,自引:0,他引:1
R. D. Pearce D. Kiehm D. T. Armstrong P. B. Little J. W. Callahan L. R. Klunder J. T. R. Clarke 《Cellular and molecular life sciences : CMLS》1989,45(3):307-308
Summary Intraperitoneal injection of allogeneic liver cells from 43-day-old male fetuses into normal 60-day female goat fetuses resulted in persistent hemopoietic chimerism in surviving recipients without clinical evidence of graft-versus-host disease. Transplantation of normal fetal liver cells into preimmunocompetent goat fetuses affected with -D-mannosidosis may provide an alternative strategy for evaluating hemopoietic stem cell transplantation in the treatment of human lysosomal storage diseases. 相似文献