全文获取类型
收费全文 | 362826篇 |
免费 | 23486篇 |
国内免费 | 1148篇 |
专业分类
387460篇 |
出版年
2018年 | 15914篇 |
2017年 | 14875篇 |
2016年 | 11902篇 |
2015年 | 4538篇 |
2014年 | 5155篇 |
2013年 | 7240篇 |
2012年 | 12461篇 |
2011年 | 23038篇 |
2010年 | 19397篇 |
2009年 | 15035篇 |
2008年 | 18874篇 |
2007年 | 21224篇 |
2006年 | 7331篇 |
2005年 | 7945篇 |
2004年 | 7904篇 |
2003年 | 7978篇 |
2002年 | 7584篇 |
2001年 | 12456篇 |
2000年 | 12407篇 |
1999年 | 9299篇 |
1998年 | 2771篇 |
1997年 | 2849篇 |
1996年 | 2791篇 |
1995年 | 2553篇 |
1994年 | 2495篇 |
1993年 | 2398篇 |
1992年 | 7298篇 |
1991年 | 7122篇 |
1990年 | 7177篇 |
1989年 | 6942篇 |
1988年 | 6483篇 |
1987年 | 6116篇 |
1986年 | 5428篇 |
1985年 | 5765篇 |
1984年 | 4544篇 |
1983年 | 3965篇 |
1982年 | 2772篇 |
1981年 | 2550篇 |
1980年 | 2365篇 |
1979年 | 4169篇 |
1978年 | 3198篇 |
1977年 | 2951篇 |
1976年 | 2893篇 |
1975年 | 3344篇 |
1974年 | 3566篇 |
1973年 | 3579篇 |
1972年 | 3793篇 |
1971年 | 3510篇 |
1970年 | 2564篇 |
1969年 | 2347篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
Indices of physical work capacity in athletes with different types of adaptation of the cardiorespiratory system that are engaged in various kinds of sports and have sports ranks from Master of Sports to Grade 2 have been studied. It has been shown that the highest physical work capacity is typical of athletes that have the inotropic type of adaptation, and the lowest, of athletes with the chronotropic type of adaptation. High indices of physical work capacity were recorded in athletes with the respiratory type of adaptation. Types of adaptation affect the indices of physical work capacity, and it is possible to forecast sports results on their basis. 相似文献
123.
124.
The use of modernized photometric accessories to a model microscope manufactured by the Leningrad Optico-Mechanical Amalgamation (USSR), as well as the practical application of innovations facilitating and standardizing research work, has made it possible to obtain objective data indicating the presence of significant, direct, linear correlation between infectious activity and the intensity of fluorescence emitted by fluorescent antibodies bound with the antigen of 11 studied variants of Japanese encephalitis virus in continuous cell lines. The study of the dynamics of fluorescence intensity permitted the objective evaluation of the previously revealed regularity in the increase of the intensity of the induced fluorescence of Japanese encephalitis antigen in continuous cell cultures. 相似文献
125.
N D Klimchuk M S Kitsara O M Frolova N M Balaeva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1985,(2):41-45
Experiments on the laboratory cultures of lice infected by Weigl's method revealed that the spontaneous, erythromycin-resistant mutant of R. prowazekii strain E, adapted to the vector's organism, retained its resistance to erythromycin during 50 successive passages without the maintenance concentrations of this antibiotic. The above strain remained sensitive to tetracycline and levomycetin. Its level of sensitivity to the latter antibiotics was similar to that of R. prowazekii strains cultivated in the vector's organism for a long time. 相似文献
126.
S Kumar M Antony N K Mehrotra 《Biochemical and biophysical research communications》1984,125(3):967-973
Single cutaneous application of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) increased epidermal oxidised glutathione reductase activity in adult mouse by almost 100%. Pretreatment of animals with vitamin A for a week resulted in 75% inhibition of TPA induced change in the enzyme activity which remained unaffected in skin treated with vitamin A alone. This biochemical change in skin induced by TPA and modulated by vitamin A has been discussed in relation to epidermal hyperplasia. 相似文献
127.
128.
The influence of wilting on the levels of free proline, soluble proteins, reducing sugars, starch and on the activities of
nitrate reductase, invertase, amylase and pyrophosphatases have been studied in the leaf tissue of five cultivars of pearl
millet at their vegetative stage under pot culture conditions. The metabolic changes could not be correlated with the yield
behaviour of the cultivars under a drought condition in the field. 相似文献
129.
130.
Phase-sensitive two-dimensional nuclear Overhauser effect spectra of [d(GGTATACC)]2 in aqueous deuterium oxide solution at four mixing times were quantified to give all nonoverlapping cross-peak intensities. A structural model for [d(GGTATACC)]2 was built in which the GG- and -CC moieties were in the B-DNA form, while the middle -TATA- moiety was in the wrinkled-D form (BDB model). This model was subjected to energy refinement by molecular mechanics calculations with the program AMBER. Counterions (Na+) were added to neutralize the charges, and water molecules were placed bridging across the minor groove. A complete relaxation matrix analysis was used to calculate two-dimensional nuclear Overhauser effect spectra of [d(GGTATACC)]2 from the above models (before and after energy refinement) and from four other [d(GGTATACC)]2 structural models: regular A, crystalline A, regular B, and energy-minimized B. Among them, the energy-minimized BDB model yielded a set of theoretical spectra that gave the best fit to the experimental spectra. It was also the energetically most stable. Therefore, it is a good representation of the ensemble- and time-averaged structure of the octamer in solution. This model has backbone torsion angles similar to those of B-form DNA in the GG- and -CC moieties and torsion angles similar to those of wrinkled D form DNA in the -TATA- moiety. The base stacking and base pairing are not interrupted at the junctions between the two structural moieties. Its minor groove is narrower than that of B DNA, and the solvent-accessible surface of the minor groove forms a closed hydration tunnel in the middle -TATA- segment. 相似文献