全文获取类型
收费全文 | 2213篇 |
免费 | 3篇 |
专业分类
化学工业 | 17篇 |
建筑科学 | 2篇 |
能源动力 | 1篇 |
轻工业 | 14篇 |
石油天然气 | 2篇 |
无线电 | 1篇 |
一般工业技术 | 1篇 |
冶金工业 | 2176篇 |
自动化技术 | 2篇 |
出版年
2019年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 68篇 |
1998年 | 740篇 |
1997年 | 428篇 |
1996年 | 267篇 |
1995年 | 153篇 |
1994年 | 112篇 |
1993年 | 116篇 |
1992年 | 13篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 28篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 33篇 |
1976年 | 66篇 |
1975年 | 4篇 |
1971年 | 1篇 |
1965年 | 1篇 |
1959年 | 3篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1948年 | 2篇 |
1909年 | 1篇 |
1890年 | 3篇 |
排序方式: 共有2216条查询结果,搜索用时 15 毫秒
21.
22.
23.
The first case of the unstable Hb Genova as a result of sporadic mutation is described. It is found in a 3-year-old Canadian boy of East Indian extraction with chronic Heinz body haemolytic anaemia. 相似文献
24.
David A. Conner Ph.D. P.E. Gary J. Grimes Ph.D. Jay Goldman D.SC. P.E. 《Journal of Systems Integration》2000,10(1):81-94
For telemedicine to reach its potential in the Internet2 environment,significant progress must be made in a number of areas. The emergingtelecommunications will include the Internet2 between medicalinstitutions and emerging broadband loop and wireless technologiesfor interconnections to homes. Within the technical environment,problems that must be addressed include the development of robotic-controlled,remote-monitoring devices unique to the various medical specialties;the encoding, transmission, and decoding of raw data specificto the specialized needs of various medical application areas;and the reduction of data for storage and retrieval in patientrecords. Institutionally, human factor and information accessissues with respect to physicians, patients, and non-physicianhealthcare providers must be addressed; healthcare insuranceprovider policies, government regulation, and state licensinglaws must be adapted for a new paradigm of healthcare delivery;and the philosophy of capital investment for the delivery ofhealthcare must be revised.Many current practiceswill be supplanted by home healthcare alternatives, the use ofpatient-initiated preventive healthcare initiatives, and remote-clinicactivity. These applications will result in central record archivingsystems; the need for encryption schemes, virus protection, andvandalism protection; extensive, additional connectivity betweenhealthcare providers and professionals; and new commercial playersin the healthcare arena.The hot applicationareas will include women's health, children's health, healthcarefor senior citizens, home healthcare, well-patient monitoring,and early-detection of medical problems. 相似文献
25.
JM Casasnovas TA Springer JH Liu SC Harrison JH Wang 《Canadian Metallurgical Quarterly》1997,387(6630):312-315
Recognition by integrin proteins on the cell surface regulates the adhesive interactions between cells and their surroundings. The structure of the 'I' domain that is found in some but not all integrins, has been determined. However, the only integrin ligands for which structures are known, namely fibronectin and VCAM-1, are recognized by integrins that lack I domains. The intercellular adhesion molecules ICAM-1, 2 and 3 are, like VCAM-1, members of the immunoglobulin superfamily (IgSF), but they are recognized by an I domain-containing integrin, lymphocyte-function-associated antigen 1 (LFA-1, or CD11a/CD18). Here we present the crystal structure of the extracellular region of ICAM-2. The glutamic acid residue at position 37 is critical for LFA-1 binding and is proposed to coordinate the Mg2+ ion in the I domain; this Glu 37 is surrounded by a relatively flat recognition surface and lies in a beta-strand, whereas the critical aspartic acid residue in VCAM-1 and fibronectin lie in protruding loops. This finding suggests that there are differences in the architecture of recognition sites between integrins that contain or lack I domains. A bend between domains 1 and 2 of ICAM-2 and a tripod-like arrangement of N-linked glycans in the membrane-proximal region of domain 2 may be important for presenting the recognition surface to LFA-1. A model of ICAM-1 based on the ICAM-2 structure provides a framework for understanding its recognition by pathogens. 相似文献
26.
H Inoue J Ferrer M Warren-Perry Y Zhang H Millns RC Turner SC Elbein CL Hampe BK Suarez N Inagaki S Seino MA Permutt 《Canadian Metallurgical Quarterly》1997,46(3):502-507
The septate gregarine parasites of flour beetles (Tribolium spp.) include Gregarina minuta Ishii, 1914, a relatively small species in which both primite and satellite possess an obvious protomerite, and a larger species that lacks the satellite protomerite. The latter species has been placed in the genera Didymophyes and Hirmocystis by various authors, but studies reported here demonstrate that this species, herein described as Gregarina triboliorum, exhibits early pairing and produces oocyst chains, both characteristics of the genus Gregarina. The oocysts of this new species are described for the first time. In addition, experimental infections using oocyst from single gametocysts reveal that oocyst chain number is variable but is typically 1, 2, or 4. Prior experiments involving a related beetle, Tenebrio molitor, demonstrated extreme host specificity within the 4 Gregarina species parasitizing larval and adult hosts. However, G. triboliorum is not limited either stadially or specially, infecting both adults and larvae of Tribolium confusum and Tribolium castaneum. 相似文献
27.
L Zhang MJ Dresser AT Gray SC Yost S Terashita KM Giacomini 《Canadian Metallurgical Quarterly》1997,51(6):913-921
OBJECTIVE: The triglyceride-lowering effects of omega-3 fats and HDL cholesterol-raising effects of exercise may be appropriate management for dyslipidemia in NIDDM. However, fish oil may impair glycemic control in NIDDM. The present study examined the effects of moderate aerobic exercise and the incorporation of fish into a low-fat (30% total energy) diet on serum lipids and glycemic control in dyslipidemic NIDDM patients. RESEARCH DESIGN AND METHODS: In a controlled, 8-week intervention, 55 sedentary NIDDM subjects with serum triglycerides > 1.8 mmol/l and/or HDL cholesterol < 1.0 mmol/l were randomly assigned to a low-fat diet (30% daily energy intake) with or without one fish meal daily (3.6 g omega-3/day) and further randomized to a moderate (55-65% VO2max) or light (heart rate < 100 bpm) exercise program. An oral glucose tolerance test (75 g), fasting serum glucose, insulin, lipids, and GHb were measured before and after intervention. Self-monitoring of blood glucose was performed throughout. RESULTS: In the 49 subjects who completed the study, moderate exercise improved aerobic fitness (VO2max) by 12% (from 1.87 to 2.07 l/min, P = 0.0001). Fish consumption reduced triglycerides (0.80 mmol/l, P = 0.03) and HDL3 cholesterol (0.05 mmol/l, P = 0.02) and increased HDL2 cholesterol (0.06 mmol/l, P = 0.01). After adjustment for age, sex, and changes in body weight, fish diets were associated with increases in GHb (0.50%, P = 0.05) and self-monitored glucose (0.57 mmol/l, P = 0.0002), which were prevented by moderate exercise. CONCLUSIONS: A reduced fat diet incorporating one daily fish meal reduces serum triglycerides and increases HDL2 cholesterol in dyslipidemic NIDDM patients. Associated deterioration in glycemic control can be prevented by a concomitant program of moderate exercise. 相似文献
28.
Prostate enlargement in mice due to fetal exposure to low doses of estradiol or diethylstilbestrol and opposite effects at high doses 总被引:7,自引:0,他引:7
FS vom Saal BG Timms MM Montano P Palanza KA Thayer SC Nagel MD Dhar VK Ganjam S Parmigiani WV Welshons 《Canadian Metallurgical Quarterly》1997,94(5):2056-2061
On the basis of results of studies using high doses of estrogens, exposure to estrogen during fetal life is known to inhibit prostate development. However, it is recognized in endocrinology that low concentrations of a hormone can stimulate a tissue, while high concentrations can have the opposite effect. We report here that a 50% increase in free-serum estradiol in male mouse fetuses (released by a maternal Silastic estradiol implant) induced a 40% increase in the number of developing prostatic glands during fetal life; subsequently, in adulthood, the number of prostatic androgen receptors per cell was permanently increased by 2-fold, and the prostate was enlarged by 30% (due to hyperplasia) relative to untreated males. However, as the free serum estradiol concentration in male fetuses was increased from 2- to 8-fold, adult prostate weight decreased relative to males exposed to the 50% increase in estradiol. As a model for fetal exposure to man-made estrogens, pregnant mice were fed diethylstilbestrol (DES) from gestation days 11 to 17. Relative to controls, DES doses of 0.02, 0.2, and 2.0 ng per g of body weight per day increased adult prostate weight, whereas a 200-ng-per-g dose decreased adult prostate weight in male offspring. Our findings suggest that a small increase in estrogen may modulate the action of androgen in regulating prostate differentiation, resulting in a permanent increase in prostatic androgen receptors and prostate size. For both estradiol and DES, prostate weight first increased then decreased with dose, resulting in an inverted-U dose-response relationship. 相似文献
29.
30.
LG Lee SL Spurgeon CR Heiner SC Benson BB Rosenblum SM Menchen RJ Graham A Constantinescu KG Upadhya JM Cassel 《Canadian Metallurgical Quarterly》1997,25(14):2816-2822
We have synthesized a set of four energy transfer dyes and demonstrated their use in automated DNA sequencing. The donor dyes are the 5- or 6-carboxy isomers of 4'-aminomethylfluorescein and the acceptor dyes are a novel set of four 4,7-dichloro-substituted rhodamine dyes which have narrower emission spectra than the standard, unsubstituted rhodamines. A rigid amino acid linker, 4-aminomethylbenzoic acid, was used to separate the dyes. The brightness of each dye in an automated sequencing instrument equipped with a dual line argon ion laser (488 and 514 nm excitation) was 2-2.5 times greater than the standard dye-primers with a 2 times reduction in multicomponent noise. The overall improvement in signal-to-noise was 4- to 5-fold. The utility of the new dye set was demonstrated by sequencing of a BAC DNA with an 80 kb insert. Measurement of the extinction coefficients and the relative quantum yields of the dichlororhodamine components of the energy transfer dyes showed their values were reduced by 20-25% compared with the dichlororhodamine dyes alone. 相似文献