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931.
Much of the differentiation of murine T cells takes place in the thymus, perhaps influenced by the operation of stringent selection mechanisms whose existence has been inferred from the high rate of thymocyte turnover in the absence of extensive emigration. The origin of those 1% of total thymocytes which leave the thymus and seed the peripheral lymphoid organs is obscure. Recent thymic emigrants are functionally and phenotypically mature, and the purported greater maturity of medullary relative to cortical thymocytes is often cited a evidence for the medullary origin of thymic emigrants, a suggestion not without its critics. To approach this question, we have now isolated a a subpopulation of thymocytes expressing high levels of a receptor that mediates the homing of blood-borne lymphocytes into peripheral lymph nodes. Surprisingly, this population of cells (1-3% of total thymocytes) is both cortical and immunocompetent, containing approximately half of all thymic cytolytic T-lymphocyte precursors. The combination of homing receptor expression and immunocompetence makes this cortical population ideally suited for emigration to peripheral lymphoid organs. 相似文献
932.
Association of rheumatoid arthritis and primary osteoarthritis with changes in the glycosylation pattern of total serum IgG 总被引:19,自引:0,他引:19
R B Parekh R A Dwek B J Sutton D L Fernandes A Leung D Stanworth T W Rademacher T Mizuochi T Taniguchi K Matsuta 《Nature》1985,316(6027):452-457
Rheumatoid arthritis (RA) is a widely prevalent (1-3%) chronic systemic disease thought to have an autoimmune component; both humoral and cellular mechanisms have been implicated. Primary osteoarthritis (OA) is considered to be distinct from rheumatoid arthritis, and here damage is thought to be secondary to cartilage degeneration. In rheumatoid arthritis, immune complexes are present that consist exclusively of immunoglobulin, implying that this is both the 'antibody' (rheumatoid factor [RF]) and the 'antigen' (most commonly IgG). Autoantigenic reactivity has been localized to the constant-region (C gamma 2) domains of IgG. There is no evidence for a polypeptide determinant but carbohydrate changes have been reported. We have therefore conducted a study, simultaneously in Oxford and Tokyo, to compare in detail the N-glycosylation pattern of serum IgG (Fig. 1) isolated from normal individuals and from patients with either primary osteoarthritis or rheumatoid arthritis. The results, which required an evaluation of the primary sequences of approximately 1,400 oligosaccharides from 46 IgG samples, indicate that: (1) IgG isolated from normal individuals, patients with RA and patients with OA contains different distributions of asparagine-linked bi-antennary complex-type oligosaccharide structures, (2) in neither disease is the IgG associated with novel oligosaccharide structures, but the observed differences are due to changes in the relative extent of galactosylation compared with normal individuals. This change results in a 'shift' in the population of IgG molecules towards those carrying complex oligosaccharides, one or both of whose arms terminate in N-acetylglucosamine. These two arthritides may therefore be glycosylation diseases, reflecting changes in the intracellular processing, or post-secretory degradation of N-linked oligosaccharides. 相似文献
933.
934.
R A Young V Mehra D Sweetser T Buchanan J Clark-Curtiss R W Davis B R Bloom 《Nature》1985,316(6027):450-452
Leprosy, a chronic infectious disease afflicting between 10 and 15 million people, is caused by the obligate intracellular parasite Mycobacterium leprae. Although M. leprae was the first identified bacterial pathogen of man, basic biochemical, immunological, diagnostic and therapeutic investigations have been severely limited because it remains one of the few human pathogens that have not been cultured in vitro. An M. leprae recombinant DNA expression library was constructed to provide a source of genes encoding proteins relevant for such studies. Monoclonal antibodies directed against M. leprae specific antigens have been used to isolate the genes encoding the five most immunogenic protein antigens of the leprosy bacillus. We report here that M. leprae specific epitopes recognized by all of 13 monoclonal antibodies tested were produced by recombinant phage in Escherichia coli. 相似文献
935.
936.
J. E. Joy S. Losee-Olson F. W. Turek 《Cellular and molecular life sciences : CMLS》1989,45(2):152-154
Single injections of the benzodiazepine, triazolam, induce phase shifts and cause a lengthening of the circadian activity rhythm in the golden hamster. The effect of triazolam on period depends on the phase of injection, but is not dependent on the direction of the phase shifts. Triazolam injections caused increases in period that were associated with phase advances as well as phase delays in the activity rhythm. This relationship between triazolam-induced phase shifts and changes in period is different from the relationship between light-induced phase shifts and period changes. 相似文献
937.
V. Roussis J. R. Pawlik M. E. Hay W. Fenical 《Cellular and molecular life sciences : CMLS》1990,46(3):327-329
Summary Two new metabolites of an apparent propionate origin have been isolated from the organic extract of the ascoglossan molluscCyerce nigricans. The proposed structures for the new natural products are based on interpretation of their physical and spectral properties. The new compounds isolated lacked the potent ichthyodeterrent properties of the whole animal extract suggesting that other molecules are involved in the defense of this shell-less mollusc. 相似文献
938.
The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) mimicked the effects of isoprenaline on the force of contraction, the cAMP content and the slow Ca++ inward current (Isi) in isolated guinea pig papillary muscles. The results support the hypothesis that phosphodiesterase inhibitors and beta-adrenoceptor agonists exert their positive inotropic effects by increasing Isi via the common mediator cAMP. 相似文献
939.
W H Boyd 《Experientia》1985,41(1):114-116
Bovine pituitary intraglandular colloid thought to be a waste product, is the holocrine secretion of intermediate lobe cells. It is housed in the intraglandular lumen (residual lumen) and is extruded into the venous circulation of the cavernous sinuses via clefts in the capsule of the gland aligned with the intraglandular lumen. Intraglandular colloid, fraction F5 (mol.wt 34,000), radiolabeled with (125I)Na and injected (0.15 ml) into the right internal jugular vein of male Wistar rats, accumulated in the endocrine pancreas. Autoradiographs showed that the material had specifically localized in the capillary network of the endocrine pancreas. Since the intermediate lobe is poorly vascularized, intraglandular colloid is considered to be the transport medium for intermediate lobe materials. 相似文献
940.